ACTIVE: Aerosol and chemical transport in tropical convection
1.
Overall scientific case
1.1 Introduction
The goal of this proposal is to answer a number of key questions about the upper tropical troposphere, a critical
research area for climate change as well as the evolution of stratospheric ozone. Its focus is on the role that deep
convection in the tropics plays in transporting aerosol and chemical species from the planetary boundary layer to
the upper troposphere. This issue is crucial for climate science (since the aerosol serve as cloud condensation
nuclei) and for the overall composition of the tropical tropopause layer (TTL) – the layer of the tropical atmosphere
between about 13 and 17 km altitude. This in turn determines the composition of the global stratosphere. We aim to
make direct measurements of a range of aerosol and chemical species in the low-level inflow and the high-level
outflow of tropical thunderstorms, relating these to model simulations of the storms and the wider environment in
which they are embedded.
The proposal is based on aircraft campaigns at Darwin, Australia (12S, 131E), using the new NERC community
aircraft for low levels and the Australian Egrett for the high-altitude outflow. Darwin is the ideal location for the
experiment, firstly because it has excellent infrastructure for the aircraft; secondly because of the existing groundbased suite of radars, radiometers and meteorological instruments; and thirdly because of the predictable nature of
deep convection in this region. The present proposal builds on the experience already gained by UWA and UMIST
at Darwin during the EMERALD-II campaign to study the nature of the cirrus outflow from tropical storms. The
new campaign will take place in the period November 2005-February 2006, as part of two international
experiments: the joint Australian/NASA/ARM TWP-ICE campaign at Darwin in early 2006 to study cloud and rain
characteristics in the Australian monsoon, and the EU SCOUT-O3 campaign to study the composition of the TTL
(using the Russian Geophysica and German Falcon aircraft, probably from Darwin in late 2005). The synergy
between the proposed measurements and those from our international partners will generate a uniquely powerful
dataset for constraining and developing models of vertical transport in the tropics and the structure of the TTL.
1.2 The science problem
The thermal structure of the tropical troposphere is determined by radiative-convective equilibrium up to 12-14 km,
which is the level of outflow of most of the convective storms (Folkins 2002). Above this, the temperature
continues to drop to a cold point around 17 km, but the frequency of convective penetration decreases with height
and the atmosphere approaches radiative balance (Highwood and Hoskins 1998, Thuburn and Craig 2002). It
therefore behaves as the base of the Brewer-Dobson circulation, determining the eventual composition of the global
stratosphere. Below the TTL convective processes dominate the vertical transport of chemical species. The vertical
transport is fast and there are potential cloud-chemical processing effects. In the upper part of the TTL nonconvective processes dominate and the corresponding vertical transport is slow. A key quantitative uncertainty in
the TTL is the partition, as a function of height, horizontal location and season, between convective and nonconvective transport.
Air transported by deep convection to the upper troposphere will have distinctive properties, compared with air
transported by large-scale ascent. For a start, short-lived chemicals of land, marine or anthropogenic origin can be
deposited virtually unchanged at high altitudes. The source gases for halogen radicals for instance (particularly
bromine and iodine) could be transported in this way, affecting ozone concentrations in the TTL and, subsequently,
the lower stratosphere (see Chapter 2 of WMO, 2002). The stratospheric impact of the halogen compounds depends
on the interplay between the transport and the chemistry in the TTL, both of which are poorly understood. This
interplay determines the degree of transformation that the source gases can undergo in the TTL, and how much
bromine and iodine actually enters the stratosphere. Conversely, observations of some short-lived halogen
compounds can reveal the origin of air transported by deep convection: CH3I is present in marine air, and so its
presence in the TTL indicates recent marine convection (Cohan et al., 1999).
Lightning in deep cumulonimbi is a potent source of NOx radicals, and possibly also of ozone; the EMERALD-II
campaign observed elevated ozone in anvils (see below) the source of which is currently uncertain. In any case,
elevated NOx with hydrocarbons (VOCs) of ground-level origin provide a photochemical source of ozone in the
upper troposphere. As ozone is an effective greenhouse gas in this region a better understanding of its chemistry is
very important for climate modelling.
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Crucial to our ability to forecast future climate change is a better representation of cirrus clouds in climate models.
This in turn means understanding the density and nature of the cloud particles that are found in deep convective
anvils, since deep convection is the major source of cirrus cloud in the tropics. This was the main thrust of
EMERALD-II (see below). However, in order to be able to calculate the crystal number concentration and sizes in
the cirrus outflow from a thunderstorm, it is necessary to know the aerosol population, since it is from this
population that the cloud condensation nuclei are drawn. There have been few measurements to date of the aerosol
population associated with deep tropical thunderstorms, and models of convective transport of aerosols and
chemicals are largely untested; although comprehensive studies of the microphysics of cirrus anvils were
performed as part of the Cirrus Regional Study of Tropical Anvils and Cirrus Layers – Florida area Cirrus
Experiment (CRYSTAL-FACE ) during July 2002, the work proposed here will focus on the role of deep tropical
convection on the aerosol and composition of the UTLS region.
The life cycle of aerosol in the atmosphere remains uncertain. One picture involves the formation of fresh ultrafine
particles in the outflow of rapidly uplifted air. The uplift causes significant aerosol loss through precipitation, but it
also transports non-soluble gaseous precursors that can subsequently be oxidised to nucleate new ultrafine particles
(Raes et al., 2000). The lack of surface area, cold temperatures and increased ion abundance close to the tropopause
all favour new particle formation and the long residence times in the TTL allows for growth to several tens of
nanometres where particles may participate in optical and cloud-forming processes. New particle formation in the
TTL may well provide sufficient particle number to supply the lower stratospheric burden (Brock et al 1995).
Twohy et al (2002) studied the outflow from anvils of a mesoscale cluster over the mid-western USA to investigate
new particle formation in the outflow region. They found CO concentrations rising to 130 ppbv within the outflow,
compared with 100 ppbv outside and CN concentrations increasing to 4 x 104 cm-3 within the outflow, more than an
order of magnitude greater than outside it. Further, NO concentrations increased to 1500 pptv within the outflow
compared to near zero outside. No measurements were made in the inflow region of the cloud but the study clearly
demonstrated the effectiveness of deep convective clouds in transporting material (gases and particles) into the
tropopause region followed by detrainment from the cloud by cirrus anvils. The study also presented strong
evidence for the formation and growth of new sulphate particles in this region of the atmosphere.
It is well established that the black carbon content of atmospheric aerosols provides an important absorber of
visible radiation in the atmosphere leading to local warming. The black carbon budget in the UTLS remains very
uncertain, and whilst aircraft are a significant source, predictions show they do not provide the main source in the
tropics where it is likely that convective transport of smoke from biomass fires provides a considerable source
(Hendricks et al 2004). Recent measurements, with a single particle soot photometer, show considerably more
black carbon in the Arctic stratosphere than has previously been measured (Baumgardner et al 2004). If these are
correct the budgets must be substantially corrected and their role in warming the lower stratosphere will be
significant. There are no such measurements in the tropics and this should be seen as a priority that ACTIVE will
seek to address. If black carbon is mixed in the same particles as sulphate aerosol or dust, the sign of the resulting
radiative forcing can be reversed, since the particles absorb as well as scatter. This points to a major difference
between fresh and aged soot. Furthermore, black carbon can act as an efficient ice nucleus, affecting the ice crystal
number and also its optical properties. Its distribution across the aerosol population will have an important bearing
on the number of available IN in the TTL region. It has to date not been possible to make such measurements since
the methodology and instrumentation has not existed. ACTIVE will make single-particle black carbon
measurements to provide a unique data set in the TTL.
At well as uncertainties in composition, there are significant inadequacies in current large-scale chemical transport
models and chemical-climate models in the TTL. Firstly, the transition from convective transport dominating to
non-convective transport dominating takes place over two or three km (i.e. only two or three grid points even in
models with relatively high vertical resolution). Secondly, the velocity fields from meteorological datasets that are
used to drive chemical transport models, both grid-based models and trajectory models, are likely to be poor in this
region, in part because of the subtle mix of convective and non-convective processes. Slow vertical transport in
non-convecting parts of the TTL is liable to be swamped by the effects of poor resolution and poor representation
of these processes. Recent experience in DAMTP with trajectory calculations in the TTL based on ERA-40 3dimensional velocity fields shows unrealistically large heating rates on many trajectories. Chemical measurements
of the type proposed here are needed to deduce with better accuracy the effect of large-scale transport, and
disentangle this from convective transport.
Our overall picture of the TTL is almost certainly too simple - a consequence, in part of the small number of quality
measurements in the region. Tuck et al. (2004) have recently pointed to the dearth of measurements of the
horizontal structure of the TTL and to the inadequacy of conceptual pictures based on simple 1-dimensional
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(ascent/descent) treatments, confirmed by recent balloon measurements of tracers in the TTL by the Cambridge
group. Based on flights in the northern tropics and sub-tropics, these point to a rich structure and variability. Tracer
measurements from Darwin during 2005/2006 will allow the impact of the two different regimes on the structure of
the TTL to be assessed. These will represent an important new data set to complement the northern hemispheric
data reported by Tuck et al. (2004).
1.3
What did we learn from EMERALD-II?
The EMERALD-II experiment was conducted in Darwin by Aberystwyth, UMIST and Imperial College in
November-December 2002 using the Airborne Research Australia King Air and Egrett aircraft. Whilst the focus of
EMERALD-II was on the effects of the anvils on the radiation field, the experiment provided significant insight
into the microphysics of large tropical storms, as well as proving the suitability of Darwin for aircraft studies of this
type. No aerosol measurements were made during EMERALD-II; however, cloud-resolving model results have
shown that the microphysics of the storms are highly sensitive to the aerosol entering the base and mid levels of the
cloud. Hence, it appears that knowledge of the aerosol entering the cloud is vital to a quantitative prediction of
cloud microphysical and dynamical behaviour, precipitation development and net radiative forcing. These key
issues have provided a further stimulus for the work proposed here.
During EMERALD-II, the two aircraft were based in Darwin and flew 13 sorties towards the Tiwi Islands (see next
section). A cloud lidar was flown on the ARA King Air aircraft, measuring the backscatter and polarisation of the
cirrus anvil through which the Egrett was flying; the two aircraft followed the same ground path simultaneously
several kilometres apart vertically. An example is shown in fig 1 (top panel) of the lidar backscatter with the
Egrett’s path superimposed as a black line. The surrounding panels show ice crystals observed with the cloud
particle imager at the points denoted by the arrows. The P.I. of EMERALD-II, Dr Jim Whiteway, is now a
professor at York University, Toronto, and is a collaborator in the present experiment. He is providing a lidar
instrument for the Egrett and contributing 40% of the Egrett flight costs.
Fig 1: Lidar backscatter and crystal habit measured on EMERALD-II
Analysis of the EMERALD-II data set has revealed differences in the cirrus outflow from the thunderstorms
between consecutive days (e.g. in ice number concentration, ice water content, size and trends in the vertical).
Analysis of MODIS satellite data shows that aerosol concentrations may be responsible for these differences as it
was found that bush fires were affecting the aerosol optical depth. Bush fires are a regular occurrence in the region
during November and are significant sources of atmospheric particulates. Large Eddy Modelling (LEM) of
EMERALD-II case studies has successfully simulated the storms and predict:
a) the CCN concentration in the inflow determines the droplet number concentration in the storm. An
intermediate value of droplet number concentration causes ‘optimal’ development of the storm, leading to rapid
accretion of cloud water by rain, and glaciation via raindrop freezing/capture. Ice number concentration in the
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anvil is correlated with the droplet number concentration, and therefore the CCN input, due to the
preponderance of homogeneous freezing.
b) as the number of ice-forming nuclei (IN) entering it increases, the storm increases in intensity, producing more
condensed mass and precipitation. At low IN concentrations, ice number concentration in the anvil is
dominated by homogeneous nucleation occurring at -38C, whereas for very high values of IN the BergeronFindeison mechanism is effective lower down in the cloud.
The overall conclusions from these modelling studies and their comparison with the EMERALD-II data are that,
whilst it is possible to simulate the development of the storm, aerosol measurements must be provided as input
parameters to properly constrain the model and hence develop its predictive capability. Aerosols, both as IN and
CCN, markedly affect the development of the cloud both dynamically and microphysically. These will in turn alter
the ability of the cloud to transport and detrain material into the TTL. The data set from EMERALD-II could not be
used to provide such tests as no aerosol measurements were made. This proposal aims to use the BAe146 aircraft to
provide a very comprehensive suite of physical and chemical measurements of aerosol particles entering the cloud,
coupled to a detailed in situ and remotely sensed picture of the cloud microphysics in the anvil region, that will
provide a sound test of model performance and prediction.
A surprising result from EMERALD-II was the high concentrations of ozone and water vapour measured in the
outflow. The enhanced ozone (up to 150 ppbv) was highly correlated with very high humidity (up to 200% RH wrt.
ice) and also with sampling of very large chain-aggregate crystals that would have been formed lower in the
convection. Such high humidity suggests that very little aerosol is getting out of the storm, but this could not be
confirmed with the EMERALD-II measurements. In the present experiment we will measure a suite of chemical
species, as well as aerosol, which will allow this issue to be resolved. Remote sensing of ozone and water vapour
by lidar will reveal any instrumental artefacts in the in-situ data.
1.4 Why Darwin?
Darwin is the ideal location for an experiment of this type, for a number of reasons; that is why the TWP-ICE
consortium is planning their experiment there for early 2006 (and why SCOUT-O3 may deploy to Darwin in
2005/6). Firstly there is Darwin’s location, giving access to two distinct convection types. From about midDecember to mid-February Darwin is affected by a strong monsoon circulation; the major global monsoon heat
source is located over northern Australia in January (Manton and McBride 1992). This results in widespread
convective activity over the Darwin area, forming mesoscale complexes typical of convection across the Pacific
warm pool region (Toracinta et al 2002). Such conditions occur around 45% of the time in the period November –
March (Jakob and Tselioudis 2003) and are generally associated with westerly winds. Measurements in these
conditions will allow the contribution of the general warm pool convection to the TTL composition to be
determined.
In the pre-monsoon period (mid-November – mid-December) and during monsoon breaks, convection is dominated
by single isolated storms. Spectacular examples occur over the Tiwi Islands north of Darwin, due to convergence of
sea breezes over the islands (Carbone et al, 2000). These are the Hector storms, which occur predictably over the
islands at about the same time each day. These giant thunderstorms, which are deeper and more electrically active
than the monsoon storms, were the subject of EMERALD-II. They reach (and penetrate) the tropopause (at 17 km)
thus directly injecting air into the TTL and TLS (tropical lower stratosphere). Their predictability and isolation also
make them excellent laboratories for comparing the aerosol input and output since the task of modelling them is not
so formidable as for extensive convection, as the success of the EMERALD-II LEM modelling testifies.
Darwin also provides the best facilities available to support the experiment. The Australian Bureau of Meteorology
(BoM) is keen to foster international research collaboration and Darwin airport provides an excellent base for
aircraft operations, as the evidence of EMERALD-II shows. The BoM operates two weather radar systems within
25 km of each other around Darwin, one fully polarimetric and one an operational Doppler. These radars provide
real-time images of the convective storms to guide aircraft operations, and their measurements of the 3-D wind and
precipitation field in the storms serve as a key constraint for LEM modelling. The BoM also operates 920 and 50
MHz wind profilers about 5 km from Darwin. In addition, Darwin is a fully-instrumented Atmospheric Radiation
Monitoring (ARM) site, with comprehensive radiation measurements, micropulse lidar and 35 GHz cloud radar.
Radiosondes are launched from the airport, and for January-February 2006 will be launched at 3-hourly intervals
from Darwin and a further five stations located around it (including the Tiwi islands and a ship to the west of
Darwin).
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1.5 Why two campaigns?
Two campaigns are planned (before and after Christmas) for two reasons:
a) the very different meteorology in the two periods. The pre-monsoon period, as mentioned above, is
characterised by isolated, giant thunderstorms reaching the tropopause. These provide the opportunity to study
the direct injection of material from low level throughout the TTL. Progress in EMERALD-II in modelling
these thunderstorms (see above) also demonstrates that we can relate measurements made in the inflow and
outflow with some confidence, thus making progress on the basic scientific objectives of aerosol modification.
By contrast, the monsoon period has more widespread, less penetrating convection more typical of the Pacific
warm pool. Studies during this period will be more readily generalised to the global scale.
b) The opportunity to participate in wider international experiments. In January and February the TWP-ICE
experiment will provide an enhanced infrastructure and a wealth of cloud measurements from ground-based and
aircraft platforms. Our aerosol and chemical measurements will complement TWP-ICE, and benefit in turn from
their measurements. The SCOUT-O3 experiment will be using the Russian Geophysica and DLR Falcon aircraft
to study the TTL in late 2005/ early 2006 and there is a good chance that it will be based in Darwin where it
would be able to reach the top of the Hector storms. Both experiments are described in more detail below.
In summary, this is a unique opportunity for UK scientists to address some extremely important scientific questions
in collaboration with two large scientific consortia. Our experience and expertise with EMERALD-II, together with
the exciting possibilities using the new BAe146 aircraft, means we can make a powerful contribution to these
experiments (with aerosol and chemical measurements) and gain a dataset that will provide exacting constraints on
a range of models.
1.6 Why a consortium?
Consortium grants are intended to support focussed, co-ordinated, collaborative research into specific issues that
cannot be addressed through other NERC funding modes. The experiment we propose is very ambitious. It requires
several aircraft with a range of specialised instrumentation, and a range of modelling approaches to interpret the
data. No one UK university has the necessary expertise to undertake this experiment, but the four universities in
this consortium all have wide experience of field campaigns and data interpretation, with modelling capabilities
ranging from cloud microscale processes to global transport scales, and their scientific expertise complements and
strengthens one another. The project is not suitable for a standard grant because of the cost and the very close coordination that will be needed, particularly in the measurement campaigns.
Further justification for a consortium approach comes from the number of international partners. Key
instrumentation for the Egrett will be provided by DLR, Germany, (ozone and water vapour) and FZJ (NO, NO2)
who are particularly interested in the ozone/NOx produced by the storm. The CAPS aerosol instrument will be
provided by Prof. Andrew Heymsfield, NCAR, USA, who is a world-leading authority on cirrus cloud. The cost of
flight hours on the Egrett will be shared by Prof. Jim Whiteway of York University, Canada, who was the PI on
EMERALD-II and has extensive experience of interpreting aircraft data. ARA Australia, will provide the basic
meteorological measurements on the Egrett, and the Australian Bureau of Meteorology (BoM) will provide ground
facilities and supporting measurements at Darwin. The experiment proposed here forms part of two major
international campaigns (described below), again requiring a high degree of co-ordination best accomplished
through the consortium mechanism.
2. Specific Scientific Objectives
The overall aim of this proposal is to determine the impact of deep convection on the composition of the TTL and
its relative importance compared with large-scale ascent.
i.
ii.
iii.
iv.
To relate measurements of aerosol and chemical species in the outflow of deep convection, and in the
surrounding TTL, to low-level sources.
To determine how deep convection modifies the aerosol population reaching the outflow, and thus evaluate
its impact on cirrus nucleation in the TTL.
To compare the concentration of aerosol and chemical tracers (with a range of lifetimes and origins) in the
outflow with that in the background TTL, and therefore determine the contribution of convection to the
composition of the TTL over Darwin.
To use latitudinal surveys of tracers, together with high-resolution global models, to determine the
contribution of large-scale transport to the composition of the TTL
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v.
vi.
vii.
To compare the effects of isolated very deep convection with that of widespread but less penetrative
convection on the composition of the TTL.
To determine the contribution of deep convection to the NOx and O3 budget in the TTL
To measure how much black carbon reaches the outflow regions of the storms.
3. The international dimension
3.1 Tropical Warm Pool – International Cloud Experiment (TWP-ICE)
(http://science.arm.gov/~mather/darwiniop/)
The impact of oceanic convection on its environment and the relationship between the characteristics of the
convection and the resulting cirrus characteristics is still not understood. An intense airborne measurement
campaign combined with an extensive network of ground-based observations is being planned for the region near
Darwin during January-February, 2006 to address these questions. TWP-ICE will be the first field program in the
tropics that attempts to describe the evolution of tropical convection, including the large scale heat, moisture, and
momentum budgets, while at the same time obtaining detailed observations of cloud properties and the impact of
the clouds on the environment. The experiment is a collaboration between the US DOE ARM project, the
Australian Bureau of Meteorology (BoM), NASA and several United States, Australian, Canadian, Japanese and
European Universities.
Observations of cloud properties will be provided by an extensive set of in situ and remote sensing instruments.
The Darwin ARM site will provide continuous measurements of cloud properties through remote sensing retrievals.
A second set of instruments will be deployed on a ship in the Timor Sea, approximately 100 km northwest of
Darwin. Added to these surface-based observations will be several research aircraft including the NASA WB-57
and the DOE Proteus, as well as three aircraft provided by Airborne Research Australia (ARA): the Egrett, King
Air and Dimona. These aircraft fulfill a variety of observational requirements to address the science goals (see 4.1).
Specific goals of TWP-ICE are:
 Make detailed measurements of the cirrus microphysics and how they relate to storm intensity and proximity
(spatial and temporal) to the parent convection.
 Verification of remotely sensed microphysical measurements.
 Provide data sets for forcing cloud resolving and single column models that will attempt to simulate the
observed characteristics and impacts.
 Document the evolution of oceanic convective clouds from the early convection phase through to the remnant
cirrus with particular emphasis on their microphysics.
 Measure the dynamical and radiative impacts of the cloud systems.
 Characterize the environment in which the cloud systems occur.
 Document the evolution of the convective boundary layer throughout the diurnal cycle and through the
lifecycle of convective systems.
3.2 SCOUT-O3
SCOUT-O3 is a 5 year EU integrated project which started in May 2004, with Prof Pyle and Dr Harris as its
coordinators. Tropical activities are a major component within SCOUT-O3 and include field campaigns, studies of
past and future ground and satellite data, and modelling. The main field campaigns will involve aircraft and
balloons. Several measurement phases are being planned. The largest phase will involve the high-flying M55
Geophysica and the DLR Falcon looking at transport of air from the TTL into the stratosphere and is due to take
place in late 2005/early 2006. The location will be finally decided in autumn 2004 after further planning studies
have taken place. The main options are the Indonesian maritime continent (with the planes most likely based at
Darwin) and West Africa. If the M55 and Falcon are based in Darwin in either late 2005 or early 2006, the Egrett
and BAe-146 activities proposed here will be closely coordinated with them. The M55 is capable of flying up to 21
km and will carry a range of chemical and particle instruments. It is very well suited to observe the influence of
convective outflow on the TTL at higher altitudes than can be measured by the Egrett. The Falcon will carry an
ozone and water vapour lidar. It will act primarily as a pathfinder for the M55 guiding it to regions of interest, but it
can also perform coordinated flights with the BAe-146.
3.3 Synergy with SCOUT-O3 and TWP-ICE
It is important to see the current proposal in the context of SCOUT-O3 and TWP-ICE. Basically, TWP-ICE is
focusing on cirrus while we are focusing on aerosol and chemical measurements (although cloud particle
measurements will of course be made by the Egrett and TWP-ICE aircraft will make aerosol measurements). The
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Proteus aircraft flies higher than the Egrett and has a flight endurance >10 hours. As well as radiometers, it carries
in-situ sampling instruments: a CAPS (as on the Egrett) for cloud and aerosol, frost-point hygrometers, cloud lidar
and radar and ice particle sampler. The NASA WB-57 carries a comprehensive aerosol and chemistry package; it
again will sample the anvils and extend the measurements to 18 km. Its flights will also be optimised for validation
of the Aura satellite. These two aircraft will concentrate on the edges of the anvils and the surrounding
environment; the Egrett will provide the bulk of the measurements in the cirrus anvils. The ARA King Air will
carry the UWA cloud lidar and a cloud radar, flying with the Egrett in the same manner as EMERALD-II; the aim
is to penetrate thicker cirrus than last time using the radar where the lidar signal is unable to penetrate. Finally, the
ARA Dimona (a low-level aircraft) will measure boundary layer turbulence and heat/moisture fluxes together with
CO2. Clearly, the various aircraft will have to be closely coordinated for maximum scientific impact. Some of the
TWP-ICE experiments will be designed for validating remote-sensing measurements (from satellite and ground)
and will not be of direct interest to this proposal, while the Egrett latitudinal surveys (see below) will not be of
interest to TWP-ICE. The bulk of the flying however will be concentrated on individual storms and cirrus anvils,
and here the aircraft will be arranged to sample different altitudes and different parts of the storm outflow, as well
as the background TTL. The combination of so many well-instrumented high-altitude aircraft will constitute a
unique experiment and characterise the impact of convection on the chemical and microphysical state of the TTL to
unprecedented accuracy.
In SCOUT-O3, the Geophysica and Falcon will fly together in the same way as the King Air and the Egrett (fig.1),
i.e. with the Falcon lidar measuring vertical profiles along the Geophysica path. These aircraft will characterise the
upper part of the TTL and the TLS (tropical lower stratosphere), with particular emphasis on water vapour and
cirrus near the tropopause. The Falcon will also make a comprehensive set of chemical measurements at low level
and in the convective part of the troposphere. If the SCOUT-O3 campaign is carried out in the pre-monsoon period,
the measurements from this proposal would provide information on the water vapour, aerosol and chemical outflow
from Hector while the Geophysica would be able to extend the vertical profiles into the lower stratosphere. Each
experiment separately would provide unique new information about the TTL; together they will form a uniquely
powerful combination.
4. Methodology and approach
4.1 Aircraft campaigns
The aircraft flights planned for this experiment fall into two categories:
a) studies of the inflow and outflow from convection. First, the BAe146 aircraft will be flown in the boundary
layer around the inflow to the chosen storm, sampling the aerosol and chemical fields in the inflow. Then,
the Egrett will be flown into the outflow of the storm, guided by the King Air or the BAe146 lidar, as for
EMERALD-II (TWP-ICE will provide the King Air). Different regions of the outflow will be studied in
turn. During the first campaign (Nov-Dec 2005), we expect (on the basis of EMERALD-II) that the
convection will be similar from one day to the next, so that the ensemble of flights can be used to build an
overall picture of the anvils. During the monsoon campaign, by contrast, each storm will be different and
the aim will be to sample a representative distribution of anvils by selecting storms with different
characteristics (e.g. oceanic, land, isolated, cluster), to gain a statistical picture of anvil properties.
b) Latitudinal surveys. The Egrett will be flown at maximum altitude (14.5 – 15 km, depending on conditions)
on transects north and south of Darwin. Advantage will be taken of the transit flights from and to the
Egrett’s home base of Adelaide (35S) for the southward survey. Northward transects will be necessarily
more limited in extent, reaching about 5 north of Darwin, but will use different altitudes out and back. If
available, the BAe146 lidar will be used to measure the vertical profiles of ozone, cloud and water vapour
along the Egrett path. Otherwise, the BAe146 aircraft will be used to survey the low-level chemical and
aerosol fields around Darwin when the Egrett is performing survey flights.
Both the BAe146 and Egrett aircraft will carry instruments for aerosol, chemical and tracer measurements. These
are described in full in the Appendix. Most of the instruments we propose to use are available at one of the partner
institutions, or as part of the aircraft facilities, or through collaboration. We propose to include four new
instruments which will either be purchased, built or leased as part of this proposal:
a) Cambridge will build two versions of the µ-Dirac instrument which is a development of the DIRAC GC,
flown successfully on the Egrett and on balloons (Robinson et al 2000). One will be deployed on the Egrett
(50-80 samples / flight), with the other used on the ground to analyse samples from the whole air sampler
on the BAe-146 (64 / flight). Here we will focus on CFC-11 (reduced concentrations indicate that
stratospheric air is sampled), CH3CCl3, CCl4, CHCl3, Halon-1211 (all industrial tracers), CHBr3, CH2Br2,
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and CH3I (an excellent tracer marine boundary layer air, Cohan et al 1999). Typical accuracy should be 5%
or better, depending on compound. The anticipated sampling interval is 3-6 minutes.
b) A Single Particle Soot Photometer (SP-2) to measure black carbon on the Egrett. This will be hired from
DMT, USA. The SP-2 samples particles between 0.2 and 1 µm in diameter and sizes them by optical
scattering. The scattering signal is also used to gate a pulsed laser that heats the particle until it
incandesces. The black body temperature is characteristic of the material incandescing. During ACTIVE
we propose to fit the instrument into the U-Bay of the Egrett and sample using an inlet designed by
Brechtel Manufacturing Inc. (BMI). The inlet uses a double diffuser cone and automatically varies the
sample flow to maintain isokinetic sampling. Versions of this inlet are now in use on the NOAA P3 and the
US DoE G-1 aircraft.
c) GRIMM SMPS+CPC system (Model 5.402-900) will be used to measure submicron aerosol on the Egrett,
also sampling from the BMI inlet. The instrument comprises an electrostatic classifier and CPC, capable of
scanning between 15 nm and 900 nm mobility diameter. The instrument is robust and compact; however,
the commercial instrument will not be capable of sampling at the reduced pressures that will be
experienced. Modifications will be made, using the advice of Dr Hans Grimm, prior to the campaign.
d) Forschunzentrum Julich NO/NO2 instrument. This is a chemiluminescent instrument (reacting O3 with NO)
with an inherent sampling time of 10 Hz and a typical detection limit for a 4 s sample of 30-50 pptv. As its
purpose is to measure NOx in the thunderstorm outflow this sensitivity is more than adequate. It is a
version of the MOZAIC NO/NOy detector, supplied by Prof A. Volz-Thomas.
4.2 Ozonesondes
During EMERALD-II, UWA ozonesonde equipment was taken to Darwin and used for a series of ozone profile
measurements. These have been very useful in helping to interpret the aircraft ozone measurements. Given the
overall focus of this campaign on the TTL region it is even more important that we fly ozonesondes to characterise
the background atmosphere in which the flights are taking place. We intend flying one ozonesonde per flight day
during the campaign periods (20 sondes) with extra flights when the background upper troposphere above Darwin
in downwind of deep convection (10 sondes).
4.3 Modelling and interpretative techniques
Large scale modelling: TOMCAT
p-TOMCAT is a new version of the three-dimensional global TOMCAT Chemical Transport Model (CTM). It has
been parallelised using the MPI message-passing library and can be run on many tens of processors to achieve
much improved performance. The model includes a detailed tropospheric chemistry scheme and includes
photolysis, wet and dry deposition and a comprehensive set of emissions. The model also includes treatment of
physical processes in the troposphere with parameterisations of shallow and deep convective transport, boundary
layer mixing and vertical diffusion. The model has been verified by several comparisons against observations from
established datasets and during measurements campaigns. Recently, the improvements to the performance of the
model have enabled some preliminary integrations at very high resolutions (0.5°x0.5°) to be performed. The model
will be used, along with trajectory studies (see next), to diagnose transport into and out of the TTL by a variety of
processes. p-TOMCAT will provide information on the expected variability of the TTL and possible differences
between the two proposed campaign periods. We expect this new dataset to point to important deficiencies in
model treatment of this region.
Trajectory modelling
The use of trajectory calculations based on 3-D winds from global meteorological datasets is well established as an
approach to interpreting and complementing in-situ chemical data. Recent studies in the extratropical troposphere
indicate very good consistency between calculated trajectories and structure observed in chemical fields, supporting
the idea that the wind fields are sufficiently accurate for this purpose (e.g. Methven et al 2003). Dynamical
phenomena in the tropics are probably not so well resolved by the meteorological datasets and such trajectories
cannot capture all aspects of non-convective transport. However agreement between structure measured in water
vapour, for example, and calculated trajectories is often very good (J. Methven, personal communication),
suggesting that when used with due care, taking account of the known presence of convective systems, they can be
a valuable complement to observations. The Cambridge group have significant experience in use of trajectory
calculations to study the tropical tropopause region (Bonazzola and Haynes 2004) and also in chemical calculations
along trajectories (Evans et al 2000).
Large Eddy Modelling
A combination of the Met Office Cloud Resolving Model (CRM) and the UMIST explicit microphysics model
(EMM) will be used to simulate individual storms. This approach is currently being used to interpret the
8
EMERALD-II dataset and was successfully used by Phillips et al (2001) to model storms forming over New
Mexico. This model will provide the main theoretical tool to link the aerosol and microphysical measurements by
the two aircraft.
The CRM includes parameterised microphysics with a double-moment scheme representing the number density
and mixing ratios of the ice phase as described by Swann (1998). UMIST will run this model for each of the
observational case studies using aircraft and radiosonde ascent data as input. The cloud structure predicted by the
model as the storm develops will be compared to the radar image, i.e. the model will predict the radar reflectivity.
Sensitivity tests will be performed with the model, varying input parameters over the range of their uncertainty e.g.
wind shear, temperature profile and ice nucleus concentration. This will enable us to understand the sensitivity of
the model to each of these parameters and hence determine the reason for differences between the predictions and
observations.
The 3-D cloud dynamics and cloud water content from the CRM simulations provide the input parameters for the
EMM. This model treats the following microphysics explicitly within this dynamical framework:
a. The activation of cloud droplets from the aerosol entering the cloud.
b. The growth of raindrops by collision coalescence, the production of ice particles by primary nucleation.
c. The homogeneous nucleation of ice is treated at temperatures below –35ºC.
d. The growth of ice particles, of habit determined by temperature and supersaturation (including ventilation
effects) aggregation and riming.
e. Secondary ice particle production by riming splintering, raindrop freezing and ice crystal evaporation.
f. The melting of precipitation below the freezing level is treated along with the recirculation of hydrometeors
between neighbouring updraughts and downdraughts.
In this way the model is able to predict the microphysical properties of the anvil region for direct comparison with
the in situ measurements. It is also able to predict the fluxes of water vapour, particles and passive tracers out of the
cloud through the anvil region. The detailed microphysical model will also enable direct comparisons between the
modelled evolution of the cloud and measurements of reflectivity from the radar both as the cloud develops and in
its mature state.
Microphysics, Aerosol and Chemistry (MAC) model
The specific advantage of MAC in this project is that it simulates a size-resolved aerosol interactively with the
cloud microphysics and dynamics, which is not done in the EMM. MAC currently uses a 2-D axisymmetric/slabsymmetric configuration for the dynamics with bin-resolved microphysics for aerosol, drops, ice, graupel and
aggregates (Yin et al 2001, 2002, 2004). It also includes a kinetic treatment of gas scavenging and bin-resolved
aqueous-phase chemistry. Therefore, size-resolved aerosol particles processed by clouds and detrained from the
cloud outflow region can be simulated. Extension of the model to a 3-D version and to include cloud electricity is
underway and will be complete before the field campaign. This model will be the main theoretical tool for
investigating chemical transport and generation (NOx/O3) in the storms. It will also be used to interpret the black
carbon measurements. For the lightning scheme, measurements from the Osaka University lightning interferometer
at Darwin will be used to constrain the simulations.
Simulations with MAC can include the effects of variable aerosol composition and externally mixed aerosol
distributions, which can influence cloud droplet spectra. On the other hand, the formation and diffusional growth of
ice particles, and the production of ice by secondary processes such as the Hallett-Mossop process, are calculated in
more detail in the EMM. Simulation of the same case studies using the two models, with regular intercomparisons,
will enable us to reach more robust conclusions regarding the microphysical and dynamical repose to aerosols.
In the second (monsoon) campaign we expect to encounter a much greater variety of convective clouds than in the
pre-Christmas campaign. It is not feasible, nor useful, to simulate them all - it is the ensemble properties of these
clouds that will be of interest. The BAe146 measurements will provide the range of aerosol concentrations and
types entering the storms (bearing in mind that Darwin, being a coastal location, is within reach of convection over
land and ocean). Thermodynamic profiles will be available from the network of radiosondes as well as the BAe146
and other TWP-ICE aircraft. These will be used as input to the model to examine the range of anvil properties
(aerosol and cirrus and chemicals) that it produces; these will be compared with the observations and used to
improve the model simulations.
9
5. Project plan
Although this is a closely integrated proposal, with each part depending on the others, we present the
project plan as a series of work packages, for clarity.
WP1 Campaign planning (all participants)
Coordinator: G. Vaughan
Given the scale of this proposal, careful planning of the experimental phase will be vital. Equipment will need to be
tested and installed on the aircraft, with some needing to be bought or hired (and so tested in the laboratory). The
PIs will need a series of meetings with the SCOUT-O3 and TWP-ICE partners to finalise arrangements and flight
planning. Logistics for the experiment will need careful planning and one (or more) of the PIs will need to visit
Australia in 2005 for this purpose.
Deliverables: Campaign logistical plan
Equipment ready for campaign
WP2 Pre-campaign modelling studies (Cambridge)
Coordinator: J. A. Pyle
p-TOMCAT will be run with full chemistry, and an additional set of tracers, to investigate transport into and out of
the TTL, and the horizontal variability of the TTL. Runs will be targeted at both seasonal and interannual
variability. The tracers will be designed to diagnose lifetime in the TTL and the location of transport into and out of
the TTL, using differently marked tracers from a range of tropical regions. Tracers will be initialised both from the
boundary layer and from within the TTL. Trajectory calculations using winds from previous years will be used to
study the range of air mass characteristics that may be expected in the troposphere in the region planned for the
observational campaign.
Deliverables: Real-time modelling tools for the campaign
WP3 Campaigns (all participants)
Coordinator: G. Vaughan
Here there will be a need to take enough people to Darwin for flight planning, instrument testing and maintenance
and ozonesonde operations. As there is an enormous benefit to be had from the theoretical participants
experiencing first hand the field campaign, it is proposed that they should also travel to Darwin for one or other of
the campaigns, to help the PI with flight planning and liaison with the other projects.
Deliverables: 125 flight hours' of data from Egrett and 100 hours from BAe146 aircraft
WP4 Data analysis and project data base (all participants)
Coordinator: G. Vaughan
The aim of this work package is to complete all the data analysis and produce final data from all the flights in a coordinated fashion. A common data structure will have to be agreed for efficient scientific exploitation of the data,
which will be influenced to some extent by the corresponding plans for SCOUT-O3 and TWP-ICE.
Deliverables: 1-second files containing data from in-situ instruments on Egrett
1-second files containing data from in-situ instruments on BAe146
Lidar data from BAe146 (if available)
Ozonesonde profiles
Data base of these and ancillary data (radar, radiosonde, forecast model products etc.)
WP5 Aerosol and cloud in the outflow (Aberystwyth, Manchester, DLR)
Coordinator: H. Coe
Vertical profiles will be made by the Egrett in the outflow regions of the cloud to examine the transport of aerosol
through the cloud system. Survey flights will be used to observe aerosol downwind of convection and in the
background upper troposphere. Measurements of the aerosol size distribution will reveal any depletion of particles
in the outflow and, whilst the SMPS will be unable to observe nucleation, its lowest sample size of 15 nm will
allow us to observe recent new particle formation. The SP-2 will measure black carbon mass and its distribution
with particle size and location in the outflow region, and this will be correlated with the measurements of aerosol
flowing into the same cloud by the BAe146 aircraft. The microphysical probes on the Egrett will be used to observe
ice crystal number, size and habit in the detraining anvil as a function of the aerosol being entrained into the lowers
levels of the cloud and the former will be used to assess the IN availability from information on ice crystal number,
size and habit.
Deliverables: assessment of particle number distributions in the detraining region of storms and their
impact on surrounding TTL air.
determination of the input of black carbon into the TTL and its distribution over the aerosol
population as a function of air mass entering the cloud.
characterisation of the microphysics of the detraining anvil as a function of the inflowing
aerosol population and assessment of the ice nucleation processes.
10
WP6 Ozone and NOx in the anvils (Aberystwyth, DLR, FZJ, Cambridge, York Canada, York UK).
Coordinator: G Vaughan
This WP will combine the ozone, NOx and VOC measurements from the Egrett, BAe146 and other aircraft with the
ozonesondes to determine the ozone outflow from convective storms. The TOMCAT model will be used to assess
the impact of this outflow on the overall TTL environment (i.e. how far away from the storm can the enhancement
be detected and how much secondary production of ozone is there in the TTL.).
Deliverables: evaluation of how much ozone, NOx and VOCs comes out of a convective storm
evaluation of impact of this production on the TTL
WP7 Transport of chemicals to the TTL (Cambridge, Aberystwyth, York, DLR, FZJ) Coordinator: N. Harris
Tracer distributions measured on latitudinal transects and other flights will be analysed to determine the processes
contributing to the composition of the TTL, with individual tracers being taken as representative of different
processes (CH3I for marine convection; VOCs for industrial pollution and biomass; low halocarbons & high O3 for
transport from extratropical lowermost stratosphere). Modelling studies will be performed in close conjunction with
WP10 to interpret specific measurements, e.g. air originating from particular convective systems. More general
studies will investigate the influence of large-scale processes on the chemical composition of the TTL
Deliverables: evaluation of relative amounts of air lifted by marine and continental convection
evaluation of impact of local processes on large-scale composition of TTL
WP8. Simulation of cloud microphysical structure (Manchester)
Coordinator: T. Choularton
This WP is key to interpreting the experimental data, as the main tool to link the inflow and outflow measurements.
It will use the CRM/EMM to simulate the microphysics of the cloud anvil and to predict the fate of particles and
gases entering the storm through its base, using radar images to constrain the dynamics. It will also evaluate the
impact of the aerosol on nucleation of cirrus particles in the TTL.
Deliverables: simulations of all storms with adequate data coverage from the two campaign periods
evaluation of the model’s ability to simulate the outflow region correctly
evaluation of the impact of the aerosol population on cirrus nucleation
WP9 Aerosol and chemical transport and processing (Aberystwyth)
Coordinator: Y. Yin
This modelling activity will simulate the processing of aerosol by the storms, and evaluate the feedback of the
microphysics on the dynamics. It will be used to calculate ensemble predictions of anvil structure during the
monsoon period, based on the variability of the BAe146 aerosol measurements. It will also calculate the transport
of chemical species through the storms, and the generation of NOx and ozone by lightning, for comparison with the
observations. It will involve close liaison with the CRM/EMM modelling.
Deliverables: evaluate the feedback between aerosol/microphysical processes and dynamics of storms
statistics of simulated anvil properties during the monsoon period
evaluation of the success of the model in simulating the outflow properties
prediction of ozone and NOx in the outflow for comparison with observations
WP10 Regional-scale impact of convection on the TTL (Cambridge)
Coordinator: P. Haynes
Back and forward trajectory calculations will be used to interpret chemical measurements made during the
campaigns and to build up a picture of the regional-scale three-dimensional circulation that was present at the time
of the measurements. This in turn will allow assessment of the regional-scale chemical impact of the observed
convective systems. (See also WP11). Comparison between trajectories, chemical measurements and results from
LES modelling will be used to identify systematic inaccuracies in trajectories due to convective transport, and
assess implications. To complement the trajectory analyses, p-TOMCAT will be run throughout the campaign at
high resolution for comparison with the measurements and for diagnostic studies. p-TOMCAT will additionally
provide a global view of transport and structure in the TTL.
Deliverables: model predictions of regional-scale chemical impact on TTL
assessment of usefulness of trajectories based on winds from meteorological datasets
comparative assessment of the influence of isolated deep convection compared with
widespread monsoon convection on the composition of the TTL.
WP11 Improved representation of cloud processes in larger-scale models (Manchester, BoM)
Coordinator: T. Choularton
The cloud modelling activity in this proposal is confined to the cloud scale, in order to interpret the wealth of
experimental data. However, under TWP-ICE there will be a range of modelling activities aimed at better
representation of cirrus clouds in mesoscale and global models. Furthermore, the results of this work will provide
an ideal set of case studies for NERC grant NE/B504706/1 (co-PI Choularton) ‘Deep convective cloud responses
11
to natural and anthropogenic aerosol perturbations’ which starts on 1 October 2004 and aims to improve the
treatment of deep convection, including tropical convection, in large scale models. In this WP the Manchester
PDRA will facilitate the use of the ACTIVE results by: (1) spending 3 months in Melbourne applying the lessons
of ACTIVE to the BoM models, in particular regional-scale models which contain realistic representations of
surface processes and which are linked to global-scale models. This will complement the Australian modelling
effort in interpreting TWP-ICE results; and (2) will also collaborate with scientists in Manchester and Leeds
working on the treatment of deep convection and mixed phase clouds in larger scale models.
Deliverables: Summary of main findings of the ACTIVE study provided to BoM mesoscale and global scale
modellers, in particular the CRM/EMM and MAC model predictions.
Joint synthesis of cloud representations in models covering a range of scales and processes
Report on strategy for improving cloud processes in larger scale models
WP12 Project management
Coordinator: G. Vaughan
A project of this complexity needs significant resources devoted to management, to ensure that the different
elements keep to schedule and that unexpected setbacks are overcome. The postdocs at Aberystwyth will assist the
PI in these duties.
Deliverables: Overall campaign science plans with SCOUT-O3 and TWP-ICE teams
Implementation plan for campaigns
Data structure plan for WP5
6 monthly project meetings
Campaign reports for the two campaigns (summarising flight information and met)
Publication strategy leading to published papers
Table 1: Plan of activities
Year
Quarter
WP1
WP2
WP3
WP4
WP5
WP6
WP7
WP8
WP9
WP10
WP11
WP12
2005
1
2
1
2006
3
4
3
2
4
1
2
2007
3
4
1
2
2008
3
4
1
2
3
4
5
8
9
9
9
10
10
10
11
12
13
6
6
7
6
Milestones
1. final science plan
2. real-time modelling tools for campaigns
3. final logistical plan for campaigns
4. campaign
5. data structure plan
6. project meetings
7. campaign reports
8. final project data set
9. initial reports on aerosol, ozone and NOx in
6,7
6
6
14
6
10. final assessment (papers) of aerosol and
chemicals in TTL compared with low-levels
11. see deliverables of WP8
12. see deliverables of WP9
13. assessment of regional-scale chemical impact
of the observed convective systems
14. report on strategy for improving cloud
processes in larger scale models
the outflow, for input to modelling packages
12
6. Justification of resources.
Table 2: Summary of staff resources requested by WP, man-months
Post
Aber RA1
Aber RA2
Aber PG1*
Man RA1
Man RA2
Man PG1*
Cam RA1
Cam RA2
Cam PG1*
York RA1
WP1
9
2
2
11
2
2
11
2
2
4
WP2 WP3 WP4 WP5 WP6 WP7 WP8 WP9 WP10 WP11 WP12
2
3
6
7
4
3
6
3
18
2
6
10
10
3
3
2
2
2
4
2
20
6
2
6
13
10
2
6
7
8
2
6
18
2
6
6
11
6
2
4
1
1
* PhD students assumed to spend 3 months each on training courses
Two postdocs and a PhD student are requested for the three main participants. The three experimental RAs
will be appointed in January 2005 to prepare for the campaign. They will need training in setting up and
operating the instruments and will organise the logistics of transporting their equipment to Darwin and
operating them during the campaign; afterwards these RAs will prepare the flight datasets. The three other
RAs will be responsible for the modelling activities, although they will also assist the experimenters during
the measurement campaigns (e.g. with meteorological summaries, liaising with SCOUT-O3 and TWP-ICE
and flight planning). The PhD students will assist during the campaigns, concentrating on data analysis.
After the campaigns, they will be involved with data analysis, modelling and scientific interpretation.
Consumables
Details of the consumables are given on the Je forms. They fall into the following categories:
(i)
Freight costs, £22 k, based on costs experienced during EMERALD-II.
(ii)
Ozonesondes, radiosondes, interface cards, balloons for 30 packages, £18k
(iii)
Campaign consumables, £29.5 k. Again, the experience of EMERALD-2 has been used to
inform this bid. Aberystwyth costs include local ozonesonde and computing consumables (£5k),
Cambridge require laboratory materials (running gases, calibration gases, etc) for µ-Dirac and
for the BAe146 CO instrument (£10k).York require £1 k for gases (some of their costs shared
with Cambridge). Consumables costs for Manchester (£13.5k) include calibration particles for
spectrometers, filter media for the BAE 146 and contributions to their analysis by IC;
components for modification of SP2 and GRIMM to operate in the Egrett’s unpressurised
instrument bay) and hire of the CAPS probe (£7k).
(iv)
Post-campaign costs – calibration work and computing costs £14.5 k
(v)
Building two µ-DIRAC instruments (gas valves, regulators, electronics, £9 k), one flown on the
Egrett and the other used on the ground to analyse samples from the BAe146 Whole Air
Sampler.
Travel and subsistence
There are several elements to the T&S budget:
(i)
Regular meetings of the participants in the UK, at one of the participating institutions. Seven
meetings are envisages during the 45-month project, two for planning and five for examining
data and ensuring scientific outcomes. £8.4 k
(ii)
As this project will join two major international experiments, funds are requested for the PI to
travel to two planning meetings and one post-campaign meeting. At present it is not decided
where these will be – one meeting is planned for Darwin in late 2005, and we have budgeted for
two further meetings in Germany and USA. £6 k
(iii)
Campaign costs. Four people (including students) each from Aberystwyth and Cambridge, and
five from Manchester will be required in Darwin, to operate instrumentation (including
ozonesondes), plan flights and perform data analysis. York will send one person. £98 k
(iv)
Conference travel, to disseminate the results of the research. £14 k
13
(v)
Professor Heymsfield requests some travel and subsistence to travel to Darwin to install and
operate the CAPS instrument during the experiment, and analyse the data. £10 k.
Equipment
A significant element of the cost of this project is the need to install aerosol instrumentation on the Egrett.
The GRIMM submicron aerosol instrument (£52 k + aerosol generator £5k) and the Single Particle Soot
Photometer (£34 k + £2.6k for computer) are described in 4.1. Both will be mounted in the Egrett U-bay and
fed via a Brechtel inlet (£30.6K). These two instruments are essential for the scientific objectives of the
project: measuring aerosol and black carbon in the thunderstorm outflow. We propose leasing the SP-2 as the
most cost-effective solution (it would cost £100k+ to buy) but this option is not available with the GRIMM
instrument. Two HP micro-ECDs (total £10k) are required for the µ-Dirac instruments
Exceptional
This is the major cost heading for the proposal, including the Egrett costs (£255 k) and BAe146 costs (£272
k). A quotation from ARA for the Egrett is attached. Although we do not pay for BAe146 flight hours, the
cost of deploying this aeroplane to Darwin is substantial, and the cost quoted is based on £4 k per day for
two campaigns of 30 days, plus four days either side to fly out and back. £40k each are requested for the
provision and operation of the FZJ NO/NO2 instrument by A. Volz-Thomas; for the provision of O3 and
water vapour by DLR; and to the RAAF for use of the Darwin military airfield.
Co-funding
Dr. Jim Whiteway (York Uni, Canada) will be involved in all parts of the project and will provide £160k
towards the Egrett flight costs (in addition to the £260k budgeted here). His experience as PI of EMERALDII will be invaluable to this project. He will also provide an upward-looking ozone lidar for the Egrett which
will be used to measure through the TTL above the cirrus anvils, to detect ozone enhancements in the TTL
and very thin clouds at the cold-point tropopause. FZJ and DLR are contributing 50% and 33% respectively
of the cost of providing their instruments, while BoM is contributing towards the infrastructure costs at
Darwin (see Je form and letters of support).
7. Management of project and resources, inc. training and career development opportunities.
Most of the instruments to be used in this project are supplied as part of the UFAM and FAAM facilities, and
are managed by those facilities and UFAM staff will be heavily involved in both field campaigns. The
overall project management will be the responsibility of the PI (Prof. Vaughan), with assistance from the
RAs as shown. There are two main challenges in managing this project – ensuring successful experimental
campaigns and ensuring successful scientific exploitation. Aberystwyth, UMIST and Cambridge have an
excellent track record in this area, with the Aberystwyth Egrett experiment in 2000 (involving Aberystwyth
and Cambridge) and the two Emerald projects (involving Aberystwyth and UMIST) successfully completed.
Dr Lewis at York also has extensive experience of successful field campaigns.
This project involves experimental work, data analysis and modelling as well as extensive international
collaboration. It is therefore ideal for training the three PhD students noted above. They will also receive
basic training in Atmospheric Physics and research techniques at their home institution, as well as taking
advantage of external courses in their area of research (e.g. the European course on atmospheres, or the
Cambridge course on geophysical fluid dynamics. The research assistants will receive training in
experimental or theoretical techniques as appropriate.
8. Long-term stewardship of datasets.
Data produced by this proposal will be supplied to BADC for long-term archiving. Data will also be shared
with collaborators in SCOUT-O3 and TWP-ICE and so will be supplied to the project databases of these two
experiments.
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cloud and the feedback on cloud development. Q. J. Roy .Meteorol. Soc., in press., 2004
Appendix 1: Aircraft and instrumentation
Egrett
The Grob 520T Egrett is a high altitude aircraft that has been modified to carry instrumentation for
atmospheric research. It can carry 750 kg of scientific load to a maximum altitude of 15 km, with an
endurance of 6 hours. The aircraft will operate from an open hangar at the RAAF base at Darwin previously
used during EMERALD-2. For ACTIVE, we propose augmenting the Egrett with a swappable U-bay
(removable instrument platform) with aerosol composition and trace gas instrumentation (Table A1). In
addition to the instrumentation below, UWA will supply a cloud lidar for the King Air aircraft.
Table A1: Egrett Science Payload
Instrument/Supplier
Variable
Egrett Location
Aerosol
DMT Single Particle Soot
Aerosol particle size distribution (0.2 – 1.0 U-Bay 1 with
Photometer (SP-2)
µm), light absorbing particle fraction (LAP), Brechtel inlet. §
carbon mass (precision ± 0.02 pg, accuracy
± 50%)
GRIMM SMPS+C system
Fine and ultrafine aerosol size distribution U-Bay 1 with
(15 – 900 nm)
Brechtel inlet. §
Cloud Microphysics
DMT Cloud, Aerosol &
Cloud Droplet psd, aerosol/small particle
Wing pylon (port)
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Institute
UMIST
UMIST
NCAR.
Precipitation Spectrometer
(CAPS)††
asymmetry, aerosol refractive index (out of
cloud), large ice psd, (0.3<Dp<3,200 µm);
Total Liquid Water Content (0.01-3.0 g m-3)
SPEC Cloud Particle Imager CPI- Cloud particle/ice CCD images for habit
Wing pylon
UMIST
230.†
identification and ice particle psd, (30 < Dp< (starboard)
2,300 µm)
Trace Gas Measurements
Aero Laser AL-5003 Airborne CO High precision (± 2 ppb), fast response (10 Fuselage,
York (UK)
Analyser (UFAM)
Hz) CO concentration.
Rosemount inlet.
Miniature GC-ECD, µDirac.$
Halocarbon suite (see 4.1)
As CO
Cambridge
Adsorbent tube sampler*
VOCs
U-Bay 2
York
Buck Research CR-2 frost point Temperature, dew/ice point, accuracy ±0.1º, U-Bay 2
DLR
hygrometer†
response time 10-20s
Tuneable diode laser Hygrometer Water vapour concentration
Starboard
UWA
(SpectraSensors) †
(2 Hz, ± .005 ppmv precision)
undercarriage
TE-49C UV Ozone sensor†
Ozone concentration (± 1 ppbv, 10 s)
Rear fuselage
DLR
Chemiluminescent NOx detector NO/NO2
U-bay 2
FZJ
† Previously flown and installed on the Egrett during EMERALD 1 and/or 2.
†† Extended variant of previously flown FSSP-100/300. This is a relatively new instrument for airborne
research that combines several previous cloud microphysics instrumentation.
§ Inlet to be purchased and fitted as part of this project.
* This is a new adsorbent tube sampler designed for autonomous operation from aircraft. The sampling
device has been recently tested for ground use during the TORCH field campaign. Up to sixteen 2L
volumetric samples are drawn onto temperature-controlled high-sample-capacity carbon traps each flight,
then sealed and removed post-flight for analysis. The target species will be C4-C9 aliphatics, acetone and
monoterpenes which derive from a variety of natural and anthropogenic sources.
FAAM (BAe 146)
The nominal performance of the aircraft is a range of about 2000 nautical miles, a ceiling of 35000 feet and a
maximum flight duration of a little more than six hours (with a cruise altitude of 27000 feet). It can carry 2
crew and up to 18 scientists. See http://www.faam.ac.uk/ for details.
Table A2, BAe146 science payload
Basic meteorology
FAAM
PCASP aerosol size distribution (0.1 – 3 µm) FAAM
Position (GPS)
FAAM
Cloud condensation nuclei
Met Office
Fast FSSP
FAAM
Condensation nuclei counter
FAAM
2D Cloud Particle Imaging
FAAM
SPEC cloud particle imager (5-2300 µm)
UMIST
probe (50-800 µm)
Nevzorov liquid and total
FAAM
Nephelometer (atmospheric scattering
FAAM
water content probe
coefficient)
Particle soot absorption
Met
Ice nuclei counter
Met Office
photometer
Office
Aerosol mass spectrometer
UMIST
Ozone
FAAM
CO (AL5002 analyser)
FAAM
Lidar (ozone/ aerosol/water vapour)
FAAM
ORAC –GC for nonmethane York
Whole air sampler*
York
hydrocarbons
* Analysed post-flight for C2-C9 aliphatics, monoaromatics, DMS, acetone, acetaldehyde (also analysed for
halocarbons by Cambridge)
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