Geo-space Effects On Composition, Aerosols and Dynamics of the Atmosphere (GEO-CADA):
An Arctic IPY consortium
P.J.Espy(BAS), J.M.C.Plane(UEA), N.J.Mitchell(Bath), I.McCrea(RAL), F.Honary(Lancaster),
T.Yeoman, N.Arnold (Leicester); Project partners: ALOMAR & UNIS(Norway), Alfred Wegener
Institute(Germany)
Introduction and Rationale
Understanding the influence of solar variability in the atmosphere system is recognized by the IPCC as a
major scientific challenge that must be quantified so that its contribution to long-term change can be
distinguished from changes of anthropogenic origin. Energetic solar radiation and particle events
penetrate deep into the atmosphere, particularly in the Polar Regions, directly affecting concentrations of
neutrals and ions and perturbing quiet-time chemical equilibrium. Since the atmosphere is a strongly
coupled system, these direct inputs can cause indirect and sometimes more dramatic effects in remote and
seemingly unconnected atmospheric regions. As neither these direct effects nor the coupling process
within the system are well characterised, the influence of solar variability is poorly represented in the
current atmospheric models that guide environmental policies. We thus propose GEO-CADA to discover
and quantify the atmospheric effects of solar radiation and energetic particle precipitation in the Polar
Regions, and the coupling processes by which that energy affects the global atmospheric system. The
three key scientific questions to be answered by GEO-CADA are:
1. What are the direct effects of changes in solar radiation and solar-driven particle precipitation on
atmospheric composition, aerosols and circulation?
2. By what processes, and on what time-scales, do these perturbations couple to other atmospheric
regions?
3. What is the combined influence of solar changes and atmospheric coupling on the climate of the
lower and middle atmosphere?
GEO-CADA is a targeted process study that will combine observational, modelling and laboratory studies
to determine the direct and indirect effects of solar radiation, cosmic rays, and solar-driven energetic
particle precipitation on the atmosphere. The observations will consist of both “patrol” and campaign
measurements of winds, temperatures, aerosols and ozone throughout in the middle atmosphere, as well
as the solar radiation and energetic particle flux inputs to the system. These will be undertaken at two
sites, one under the auroral oval (ALOMAR, Norway and ESRANGE, Sweden) and one deep within the
polar cap and vortex (Ny Ålesund and Longyearbyen, Svalbard), so as to assess both the direct and
coupled effects. The laboratory studies will provide the underpinning physico-chemical data for model
development, focusing the reaction kinetics of the neutral and ionized gasses found to be affected by
changes in the solar and particle inputs, and on aerosol formation (e.g. meteoritic smoke, mesospheric
aerosols and noctilucent clouds). The modelling effort will utilize the relevant reaction rates in simplified
box models to gauge the processes most important for coupling these changes throughout the stratosphere
through thermosphere system. These will then be incorporated into the chemical schemes of larger
circulation models to assess the effect on the circulation; the feedbacks between the directly driven
chemistry and the dynamic transport of the activated species; and the effect on tropospheric energy
exchange. Ultimately, GEO-CADA will provide a picture of the most important processes driven by
changes solar radiation and energetic particle precipitation and the coupling processes by which that
energy affects the global atmospheric system.
GEO_CADA represents a strategic sub-set of the goals proposed in the Deep Vertical Coupling
(DEEVERT) project that is part of Clustering 7 of the IPY programme that is within the scope and timeline of the NERC Arctic-IPY initiative. While focusing on the Arctic regions, GEO-CADA’s synergy
with the BAS Global Science in the Antarctic Context core programme, Sun-Earth Connections, will
provide a value-added bipolar aspect. The proposed observations will exploit the UK EISCAT effort, our
co-investigator status on the NASA TIMED and AIM satellite missions, and the existing instrumentation
at ALOMAR, Ny Ålesund and Longyearbyen. However, the infrastructure at the NERC Artic Station
would be substantially improved by extending the range of measurements possible and by providing fulltime remote electronic access to the new automated instrumentation proposed.
Methodology
Observational Programme: Observations will take place under the auroral oval (ALOMAR, Norway and
ESRANGE, Sweden) and deep within the polar cap and polar vortex (Ny Ålesund and Longyearbyen,
Norway). In order to identify the atmospheric response, data will be sorted into quiet and disturbed
conditions using F10.7 flux and particle energy inputs. The 27-day solar rotation will provide fine-scale
variations, whilst storms will provide extreme and transient events. Ground-based radars and optical
imagers that operate autonomously will provide both quiet and disturbed time measurements of
temperatures, winds, tides, planetary waves, gravity waves and gravity-wave momentum flux. Our partner
organizations will monitor Ozone and aerosol concentrations in the stratosphere and mesosphere using
DIAL and Rayleigh lidars at the two sites. EISCAT, ground-based riometers, VLF and optical imagers
will quantify the energy, deposition location and flux of energetic particle in the atmosphere and identify
quiet and elevated periods. To extend the ground-based data, the SABER/TIMED satellite observations
will provide ~15 transects per day (up to ~80 degrees latitude) of temperature, NO, ozone and atomic
oxygen in the stratosphere, mesosphere and thermosphere. Similarly, sunrise/sunset altitude profiles of
temperature, aerosol, NO and ozone concentrations from the AIM spacecraft will be available throughout
the IPY measurement period.
The UK already operates a number of meteor radars in the Arctic through Bath University that will be
incorporated in this study. These systems are autonomous and well suited to providing the wind and wave
climatology as well as the changes to that background related to periods of elevated solar radiation,
cosmic rays and solar-driven energetic particle precipitation. New airglow-auroral imagers will be
proposed for the two stations to measure gravity waves and the gravity-wave momentum flux, as well as
the characteristic energy and spatial morphology of precipitating electrons and protons. Similarly, the
UK operates autonomous imaging riometers at ALOMAR through Lancaster University, and VLF
measurements at Ny Ålesund through BAS that will be used in this investigation. One new riometer and
VLF system will be proposed to complete the coverage. Finally, the continued UK membership in
EISCAT will continue through the duration of the proposed investigation, providing measurements from
80 km through the thermosphere at both ALOMAR-ESRANGE and Longyearbyen. Proposals for
EISCAT time will be made through RAL.
Laboratory measurements: Utilizing facilities at UEA, measurements will include determinations of rate
coefficients of selected reactions of neutral and ionized gases, measured over the appropriate temperature
and pressure ranges of the stratosphere through thermosphere. Studies of aerosol nucleation and growth,
and heterogeneous processes on low-temperature ice surfaces and analogues of meteor smoke particles
will be undertaken to assess the effects of solar-driven changes
Modelling studies: The modelling programme will explore dynamical and radiative coupling processes to
assess their importance for inclusion in the UM, via simpler models such as the ex-UKMO stratospheremesosphere model at Leicester. The chemical coupling processes from the mesosphere and thermosphere,
such as auroral production of NO, and the role of meteoric metals and smoke particles, will be explored
via a box model to include the relevant reactions before adding them to a modular chemical scheme in the
UM. Finally, the programme will include a scheme to test the various scenarios of ice nucleation
processes that form middle atmospheric aerosols (e.g. meteoric smoke, ion clusters), and would attempt to
separate the contributions to their apparent change in frequency and brightness from increased greenhouse
gases, changes in nucleation, changes in dynamics, and changes in H2O or its photolysis rate.
Logistics support requirements: Additional space for passive optical measurements at the NERC Artic
Station at Ny Ålesund and a permanent inter-net connection.
Funding sought from NERC: Approximately £1.2M
Legacy/Deliverables: Quantification of the coupling processes that connect different levels of the
atmosphere and how these processes respond to solar variability. Enhanced, world-class instrumentation
at ALOMAR and Ny Ålesund; enhanced facilities at the NERC Artic Station extending the measurement
capabilities of the station to automated atmospheric observations; full-time internet connection the station
to facilitate all users at the station.