Gao, P., Zhang, X., Crisp, D., Bardeen, C., Yung, Y. L., 2012, Meteoric Dust as
Condensation Nuclei of Small-Mode Particles in the Upper Haze of Venus, AGU
Abstract P11D-1850
ABSTRACT: Observations by the SPICAV/SOIR instruments aboard Venus Express
have revealed that the Upper Haze of Venus is populated by two particle modes, as
reported by Wilquet et al. (J. Geophys. Res., 114, E00B42, 2009). In this work, we posit
that the large mode is made up of cloud particles that have diffused upwards from the
cloud deck below, while the smaller mode is generated by the in situ nucleation of
meteoric dust. We test this hypothesis by using version 3.0 of the Community Aerosol
and Radiation Model for Atmospheres, first developed by Turco et al. (J. Atmos. Sci., 36,
699-717, 1979) and upgraded to version 3.0 by Bardeen et al. (The CARMA 3.0
microphysics package in CESM, Whole Atmosphere Working Group Meeting, 2011).
Using the meteoric dust production profile of Kalashnikova et al. (Geophys. Res. Lett.,
27, 3293-3296, 2000), the sulfur/sulfate condensation nuclei production profile of
Imamura and Hashimoto (J. Atmos. Sci., 58, 3597-3612, 2001), and sulfuric acid vapor
production profile of Zhang et al. (Icarus, 217, 714–739, 2012), we numerically simulate
a column of the Venus atmosphere from 40 to 100 km above the surface. Our aerosol
number density results agree well with Pioneer Venus data from Knollenberg and Hunten
(J. Geophys. Res., 85, 8039-8058, 1980), while our gas distribution results match that of
Kolodner and Steffes below 55 km (Icarus, 132, 151-169, 1998). The resulting size
distribution of cloud particles shows two distinct modes, qualitatively matching the
observations of Pioneer Venus. We also observe a third mode in our results with a size of
a few microns at 48 km altitude, which appears to support the existence of the
controversial third mode in the Pioneer Venus data. This mode disappears if coagulation
is not included in the simulation. The Upper Haze size distribution shows two lognormallike distributions overlapping each other, possibly indicating the presence of the two
distinct modes. We test our hypothesis by simulating the atmospheric column with only
meteoric dust input, and with only sulfur/sulfate nuclei input. Our results show that the
combined Upper Haze size distribution is in essence the sum of the size distributions of
these two cases, indicating that it is very likely the two observed modes indeed arise from
the different sources mentioned above. We will test the robustness of these results by
varying the input rates and sizes of condensation nuclei and the altitude-dependence of
the eddy diffusion coefficient in future sensitivity tests.
Hicks, R. K., Trainer, G. T., Jimenez, J. L., Yung, Y. L., Toon, O. B., Tolbert, M. A.,
2012, A Termolecular Reaction Mechanism for Nitrogen Incorporation in Aerosol
Produced by Far UV Irradiation of CH4-N2 Atmospheres, AGU Abstract P12B-08
ABSTRACT: Results from the Aerosol Collector and Pyrolyser located onboard the
Huygens lander reveal the presence of carbon and nitrogen in Titan’s aerosols. Nitrogen
incorporation is thought to be initiated by energy sources strong enough to break the N-N
triple bond of molecular nitrogen (9.8eV). Such energy sources include extreme UV
photons (λ <120 nm) and electrons from Saturn’s magnetosphere. Less energetic photons
in the far UV (120-200 nm) penetrate to the stratosphere of Titan and are only expected
to affect hydrocarbon photochemistry there. However, recent results from our laboratory
indicate a surprising amount of nitrogen incorporation- up to 16% by mass- in Titan
aerosol analog produced by photochemistry initiated by far UV irradiation of CH4/N2
mixtures. The termolecular reaction
CH + N2 + M --> HCN2
has been proposed to account for this observation. Here, we test this hypothesis by using
a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) to measure
the mass loading and chemical composition of aerosol produced at a range of pressures
from roughly 0.1 to 1 atm. Even though these gas mixtures spanned an order of
magnitude in pressure, they experienced the same residence time in the photochemical
chamber and had the same methane optical depth. We report a 150% increase in aerosol
mass loading across the range of pressures studied, indicating that the mechanism
controlling the total mass produced depends on pressure. We also report an overall
increase with pressure in the ratio of nitrogen-bearing organic species to hydrocarbononly species. These observations support the hypothesis that the termolecular reaction
above is responsible for the incorporation of nitrogen into Titan aerosol analog produced
from CH4/N2 gas mixtures irradiated in the far UV. These findings have implications for
our understanding of the evolution of Titan’s atmosphere, and the atmospheric synthesis
of biologically relevant N-containing molecules.
Trammell, J. H., Jiang, X., Li, L., Liang, M., Zhou, J., Yung, Y. L., 2012, Investigation of
Atmospheric Recycling Rate from Observation and Model, AGU Abstract H13K-06
ABSTRACT: Precipitation plays an important role in the hydrological cycle on Earth.
Based on the long-term (1988-2009) meteorological data sets, our observational study (Li
et al., 2011) revealed that the precipitation increased over the wet area (i.e., monthly
precipitation > 200 mm) and decreased over the dry area (i.e., monthly precipitation < 50
mm) during the past two decades. The precipitation trend reported in our study is
consistent with a “rich-get-richer” mechanism suggested by theoretical studies (Chou and
Neelin, 2004; Neelin et al., 2006; Chou et al., 2009). Here, we investigate whether the
current atmospheric models can quantitatively capture the characteristics of precipitation
from the observational study (Li et al., 2011). Quantitatively simulating the precipitation
trend over the globe during the past two decades not only help predict the variation of
precipitation in the future but also provide a numerical basis to better understand the
physics behind the temporal variation of precipitation.
The NASA Goddard Institute for Space Studies (GISS) model is used to look at a historic
run of the global precipitation, temperature, and water vapor, in which the historic
greenhouse gases are included. We compare the historic simulation from the GISS model
with the actual observations provided by the Special Sensor Microwave Imager (SSM/I)
and the Global Precipitation Climatology Project (GPCP) (Li et al., 2011). We also
compare the historic run with a control run, in which the concentrations of the
greenhouse gases are fixed. With the global warming due to the historic greenhouse
gases, the historic run precipitation data in the “wet” areas illustrate an increasing trend
of precipitation over the wet area, which is consistent with the observational analysis (Li
et al., 2011). In contrast, the control run does not show a significant temporal variation in
the global temperature and precipitation. The comparison between the historic run and
the control run suggests that the increasing greenhouse gases and the corresponding
temperature variation affect the temporal variation of precipitation over the wet area. Our
simulations also show the observed increasing water vapor with the global warming,
which further implies that the increasing water vapor also contributes to the temporal
variation of precipitation. However, the GISS simulations do not successfully generate
the decreasing trend of precipitation over the dry area. We are testing the GISS model
and conducting more diagnostic studies to explore the “poor-get-poorer” mechanism over
the dry area.
Zhang, X., Shia, R., Allen, M., Liang, M., Yung, Y. L., 2012, Simulating Hydrocarbon
Distribution in the Jovian Stratosphere in a Chemistry-Transport Model, AGU Abstract
P13B-1943
ABSTRACT: The chemical and dynamical processes in the stratosphere of Jupiter are
poorly known. In this work, we constrain the meridinal transport processes using the
latitudinal distributions of ethane and ethylene obtained by the Cassini spacecraft during
Jupiter flyby in 2000 (Nixon et al. 2010; Zhang et al., 2012). Previous studies (Kunde et
al. 2004; Liang et al., 2005) have suggested that the horizontal transport timescale
between 1-10 mbar should fall within 1 to 300 years, i.e., the chemical lifetimes of
ethylene and ethane, respectively. But the relative roles of diffusion (eddy-mixing) and
advection in the horizontal transport are highly uncertain, as revealed by other tracers
such as HCN and CO2 (Lellouch et al., 2006). We introduce a two-dimensional (latitudepressure) photochemical-diffusive-advective model to simulate the distribution of
hydrocarbons in the stratosphere. Analytical solutions, both in one-dimensional
(pressure) and two-dimensional coordinates, are derived to gain the physical insight of
the coupled chemical-transport processes, and also used for validating the numerical
methods. The residual mean circulation derived from the instantaneous radiative forcing
during the Cassini flyby (Zhang et al., 2012) is applied to the simulations. The effects of
polar aerosol heating and possible chemical sources due to ion chemistry in the aurora
regions are discussed.
Cosentino, R., Morales-Juberias, R., Dowling, T. E., Zhang, X., Nixon, C. A., West, R.
A., Yung, Y. L., Allen, M., 2012, Simulations of the Jovian Stratosphere with diabatic
heating and mechanical forcing terms, AGU Abstract P13B-1945
ABSTRACT: The coupling of dynamical and chemical processes in the middle
atmosphere of Jupiter determines the structure of mean temperatures and mean zonal
winds. The Cassini flyby of Jupiter in December 2000 provided detailed information
about the mean temperatures and atmospheric abundances of methane, acetylene and
ethane in the Jovian atmosphere. Each hydrocarbon species has an associated specific
heating and cooling rate from which a net heating term can be obtained (Zhang, X, et al
2011). We incorporate a two dimensional (latitude & pressure) net heating rate derived
from these chemical species into a general circulation model (GCM) to explore the
impact on the evolution of stratospheric temperatures and compare results to
observations. This thermal forcing alone does not produce agreement between the
observed temperatures and model outputs, so we also investigate mechanical forcing by
waves. Atmospheric waves are known to directly impact the upper troposphere and lower
stratosphere of Earth (Dunkerton 1985) and Jupiter (Friedson 1999). According to
McLandress and Scinocca (2004), more advanced dissipation schemes produce nearly
identical responses in GCM simulations and refinements to the source spectrum are
needed to more accurately capture climatological responses of the atmosphere. Since
there is not enough observational evidence to completely characterize the source
spectrum in Jupiter, we implement a gravity wave drag parameterization in the GCM
following Friedson (1999). This consists of a flat source spectrum of waves and a simple
dissipation mechanism like that proposed by Lindzen and Holton (1968). We present the
results obtained by using both a heating forcing derived from remote sensing
observations and a mechanical forcing by waves on the Jovian stratosphere.
Liang, M., Lin, L., Tung, K., Yung, Y. L., Sun, S., 2012, Lessons from Multi-Millenium
Runs of Coupled Atmospheric-Ocean General Circulation Models, AGU Abstract A21E0106
ABSTRACT: Coupled atmosphere-ocean general circulation models (AOGCM) are used
for climate prediction on the degree of warming due to increases in greenhouse gases,
and for policy recommendations on emission curbs. We first demonstrate that the
currently adopted protocol for obtaining such a prediction does not yield a robust solution
and therefore cannot be relied upon for policy recommendations. The range of
uncertainty in such predictions may have been underreported when models participating
in Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4)
were run with their oceans at various stages of flux adjustment with their atmosphere, and
could change significantly simply by running them longer. This is shown by comparing
multi-millennium long runs of the Goddard Institute for Space Studies coupled model
(GISS-EH) and the Community Climate System Model (CCSM4) with what were
reported to AR4. For common predictions from preindustrial condition to 2030-2100, the
previously predicted warming and spatial patterns vary even in ensemble average. The
commonly adopted remedy of subtracting the “climate drift” is ineffective and often leads
to a wrong solution. The long model runs here also reveal the range of variability (~30%)
in the Transient Climate Response (TCR) within the same model with the same
Equilibrium Climate Sensitivity (ECS). Fortunately, for simulations with multi-decadal to
century long time horizon, robust solutions can be obtained off thousand-year-long
control runs that reach “quasi-equilibrium” using a new protocol. The problem of
different quasi-equilibrium states in long runs and the memory of the solution on these
states are also addressed.
Zhang, Q., Li, K., Li, C., Liang, M., Yung, Y. L., 2012, A Sensitivity Test of the Ozone
Solar Cycle Response with Respect to Chemical Kinetics and Model Parameters, AGU
Abstract A21G-0137
ABSTRACT: Abstract: Previous studies have shown that the observed O3 solar cycle
(SC) responses in upper and middle stratosphere are very different from those predicted
by models. It is argued whether the differences are within the uncertainties of
measurements and chemical kinetic rates. To answer this question, a simple onedimensional (1-D) Caltech/JPL photochemical model is employed to study the
discrepancies between observed and model O3 solar cycle responses. A simplified list of
reactions is developed including Chapman, HOx, NOx and ClOx chemistry. We perform
sensitivity tests on a significant portion of the kinetic rates to investigate whether the
observed O3 SC response can be modeled using standard chemistry. Other model
parameters such as eddy diffusivity are included in the tests. Finally, the optimal
estimation method (OEM) is employed to derive a set of kinetic rate coefficients and
model parameters that would minimize the difference between the observed and the
model SC responses in O3. The outcome of retrieval represents the best-fit O3 response
under the constraints of standard chemistry and measurement uncertainties.
Yung, Y. L., Weibel, J., Shia, R., 2012, An Optimized Evaluation of Isotopic
Fractionation of N2O in the Atmosphere, AGU Abstract A21G-0145
ABSTRACT: This work examines the relationships between the isotopic photodissociation of N2O, agreement between experimental and theoretical photolytic
absorption cross-sections, transport, and calculated enrichment values for the lower
stratosphere. Improvements in the theoretical description of the isotope dependent photodissociation cross-sections for N2O have spurred a re-evaluation of previous calculations
of stratospheric fractionation. However, except in the case of 15-N14-NO, these
improvements have not corresponded to much greater agreement between measured and
calculated stratospheric enrichment. While overall agreement between experimental and
theoretical photo-absorption cross-sections has improved, there are still some
discrepancies. Therefore, we have optimized the agreement between calculated and
measured isotopic stratospheric enrichment values by modifying the calculated photodissociation cross-sections. The impact of the new cross-sections for the N2O budget due
to the exchange between the stratosphere and the troposphere is examined using the
Caltech/JPL 2-D model.
Li, K., Wang, Sh., Pongetti, T. J., Sander, S. P., Yung, Y. L., 2012, The 27-day solar
cycle modulation in hydroxyl radicals over the Table Mountain Facilities, California
(34.4°) , AGU Abstract GC22E-02
ABSTRACT: Shapiro et al. [Atmos. Chem. Phys., 12, 3181–3188, 2012] have examined
the 27-day solar cycle modulation in tropical mesospheric hydroxyl radicals (OH)
measured by the Microwave Limb Sound (MLS), and found that the OH 27-day solar
response is ~1% per 1% change in Lyman-α (%-OH/%-Lyα) at 80 km and reduces to
~0.2%-OH/%-Lyα between 60 – 76 km. The OH signal was correlated (anti-correlated)
with the filtered Lyman-α index (mesospheric water vapor), suggesting that the OH solar
variability is likely generated through water vapor photolysis. However, Shapiro et al.’s
results have been limited to the availability of MLS OH data after 2004 when the solar
maximum was passed. The ground-based measurement of OH column over the Table
Mountain Facilities (TMF, 34.4°N) since 1998, may be used to extend the findings by
Shapiro et al. To better capture the solar modulations, the TMF OH data are correlated
with the Lyman-α index for boreal summer during 1998 – 2004. The sensitivity of TMF
OH to Lyman-α to the 27-day solar cycle is 0.32 %-OH/%-Lyα, which lies within the
lower mesospheric values reported by Shapiro et al. A photochemical model has been
used to simulate the 27-day solar cycle response in the OH vertical profile and the
covariance between OH and water vapor in the lower mesosphere over the 27-day solar
cycle will be discussed.
Wang, S., Li, K., Liang, M., Sander, S. P., Yung, Y. L., Livesey, N. J., Sentee, M. L.,
Harder, J. W., Snow, M. A., Mills, F. P., 2012, Vertical Profile of the Solar Cycle
Induced Variability in Atmospheric OH and the Implications on Ozone, AGU Abstract
GC22E-03
ABSTRACT: Solar irradiance variability during the 11-year solar cycle has been shown
to have strong impacts on Earth’s atmospheric composition and climate. Wang et al.
[PNAS, 2012, under review] extracted the solar cycle signal in atmospheric hydroxyl
radical (OH) from ground-based and satellite observations, which shows excellent
correlation with the variability in solar parameters such as total soar irradiance (TSI) and
Lyman-alpha. The observed 7-10% variability in total OH abundance in mid-latitude is
larger than model simulations (~3% and ~6-7% for model runs using solar spectral
forcing from reconstruction by Naval Research Laboratory (NRL) model and
measurements by Solar Radiation and Climate Experiment (SORCE), respectively). In
the present study, we examine in detail the vertical profile of the solar cycle signal in OH
and its major source species based on simulations (using the Whole Atmospheric
Community Model (WACCM) and the Caltech/JPL 1-D photochemical model) and
global observations from Aura Microwave Limb Sounder (MLS). The general shape of
the observed OH vertical profile response to solar cycle is close to model simulations
using solar forcing from SORCE measurements, showing a primary peak response in the
mesosphere and a small secondary peak response in the upper stratosphere. The
latitudinal dependence of this variability will also be presented. The corresponding
impacts on ozone and hence the climate will be discussed.
Jiang, X., Olsen, E. T., Pagano, T. S., Chen, L., Licata, S., Yung, Y. L., 2012, Natural
Variability of CO2 From Satellite Retrievals and Model Simulations, AGU Abstract
A33I-0245
ABSTRACT: The increasing level of the atmospheric CO2 has a significant influence on
the global climate change. Superimposed on this trend is an annual cycle resulting from
the uptake and release of CO2 by the vegetation. In addition to the trend and the annual
cycle, atmospheric CO2 also exhibits variability at different time scales. Combining the
satellite/in-situ observations and model simulations, we found that there is a semi-annual
oscillation (SAO) signal in the middle tropospheric CO2 [Jiang et al., GBC 2012]. The
SAO signal in the CO2, which can propagate from the surface to the mid-troposphere, is
related to the CO2 exchange between biosphere and atmosphere [Jiang et al., GBC 2012].
El Niño and Southern Oscillation (ENSO), an important large-scale climate inter-annual
variability in the tropical region, can also influence CO2 concentrations. Using midtropospheric CO2 from satellite and model, we found that ENSO can influence the midtropospheric CO2 concentrations [Jiang et al., GRL, 2010; Jiang et al., JAS 2012]. Midtropospheric CO2 is enhanced in the central Pacific Ocean and diminished in the western
Pacific Ocean during El Niño. Similar signal is also seen in the chemistry-transport
model. However, the signal is weaker in the model than that in the observation [Jiang et
al., JAS 2012]. In the high latitude, we have utilized the satellite CO2 data to explore the
influence of the northern hemispheric annular mode (NAM) on the mid-tropospheric
CO2 and found that there is less (more) CO2 at the polar region during the positive
(negative) NAM years [Jiang et al., GRL 2010]. These results will help us better
understand the natural variability of CO2, which is important for investigating the carbon
budget.
Kuai, L., Worden, J., Kulawik, S. S., Bowman, K. W., Biraud, S. C., Abshire, J. B.,
Wofsy, S. C., Natraj, V., Frankenberg, C., Wunch, D., Connor, B. J., Miller, C. E., Roehl,
C. M., Shia, R., Yung, Y. L., 2012, Profiling Tropospheric CO2 using the Aura TES and
TCCON instruments, AGU Abstract A44C-05
ABSTRACT: Characterizing the global carbon budget requires mapping the global
distribution and variability of CO2 sources and sinks. Measurements of the total column
of CO2 by ground or by satellite have the potential to estimate global sources and sinks
(Rayner and O’Brien, GRL, 2001, Olsen and Randerson, JGR, 2004) but are less
sensitive to regional scale and local sources and sinks because CO2 is a long-lived gas
which makes it challenging to disentangle local sources from CO2 transported into the
observed air parcel (Keppel-Aleks et al., BGD, 2011). We explore the use of total column
measurements with estimates of the free tropospheric CO2 by TES to distinguish
boundary layer CO2 and free tropospheric CO2 because quantify the vertical gradient
between the free troposphere and boundary layer is critical for estimating CO2 fluxes
(Stephens, Science, 2007) and near surface CO2 should be more sensitive to local fluxes
than the total column CO2. In this study, CO2 profiles are estimated from the Total
Carbon Column Observing Network (TCCON) measurements and integrated into a
column-averaged concentration. These column averages agree with aircraft data within
0.67 ppm, consistent with the uncertainties due to measurement noise and temperature.
There is a bias of about -5 ppm, consistent with Wunch et al. (Atmos. Meas. Tech. 2010).
Free troposphere estimates of CO2 are obtained from the GEOS-Chem model that has
assimilated CO2 measurements from Aura Tropospheric Emission Spectrometer. The
boundary layer CO2 estimates are calculated by subtracting TES free tropospheric CO2
from TCCON column CO2. This estimate of boundary layer CO2 agrees well with
aircraft data with RMS of 1.44 ppm for about the fifty PBL CO2 estimates. This work
shows that total column from NIR measurements (GOSAT, TCCON and OCO-2) and
free troposphere measurement from TIR (e.g. TES and AIRS) can be used to profile CO2
and obtain PBL CO2 with precision necessary to capture the atmospheric CO2
variability. It also shows potential of joint retrieval of NIR and TIR. With a long-term
boundary layer CO2 record, the CO2 surface flux can be better quantified.
Newman, S., Xu, X., Kort, E. A., Miller, C. E., Sander, S., Duren, R. M., Eldering, A.,
Yung, Y. L., 2012, Seasonal Variations in Fossil Fuel Emissions in the Los Angeles
Megacity, AGU Abstract GC53B-1274
ABSTRACT: Understanding the effects of global warming resulting from increasing
CO2 levels in the atmosphere requires understanding the sources and trends of emissions
in urban regions, which contribute disproportionately relative to their spatial extent. We
report the carbon isotopic composition of CO2 in air collected during mid-afternoon in
two locations within the Los Angeles basin of California, Pasadena and Palos Verdes
peninsula, for the past 3 (Palos Verdes) - 6.5 (Pasadena) years. Radiocarbon (Δ14C) is
the gold standard for distinguishing between CO2 produced by terrestrial biosphere
processes and fossil fuel combustion, since the latter contains virtually no 14C, whereas
photosynthesis and respiration reflect the modern atmosphere. The stable isotopic
composition of carbon in CO2 (δ13C) can be useful in distinguishing petroleum (higher
δ13C) from natural gas (lower δ13C) combustion. We observe a significant inverse
correlation between the fraction of CO2 from fossil sources at the receptor site of
Pasadena, as determined by Δ14C, and the δ13C of the pollutant end member, determined
from the Keeling plot intercept. This indicates that the fraction of CO2 emitted by natural
gas combustion increases as the fraction of CO2 contributed locally by all fossil fuel
burning increases. The proportion of CO2 emitted by fossil fuel combustion was never
less than 80% during the study period, and it was occasionally above 100% when the
biosphere was a local sink for CO2 during the second quarter of the year. In Palos
Verdes, the proportion of fossil fuel combustion in the local emissions was much more
varied, ranging from 25 to >100%. The local emissions are inversely correlated at the two
sites, reflecting the importance of transport in controlling the signals detected. During the
summer, air travels from the ocean over the Los Angeles basin to Pasadena, whereas
during the winter, wind directions are much more varied, with frequent events from the
northeast bringing air of relatively low CO2 content from the desert to Pasadena and then
over the basin to Palos Verdes. The isotopic compositions reflect this passage over
emissions sources in the basin in the seasonal cycles observed at the two sites.