Xi Xi, Vijay Natraj, Ming Luo, Run-Lie Shia, Stanley P Sander, Yuk L Yung, 2013, CO2, CH4,
CO and Chlorophyll Fluorescence Retrievals for the Geostationary Carbon Process Investigation,
Abstract A12C-03 presented at 2013 Fall Meeting, AGU, San Francisco, CA, 9-13 Dec.
The Geostationary Carbon Process Investigation (GCPI) combines an imaging Fourier
Transform Spectrometer instrument with a geostationary Earth orbit vantage point to realize a
transformational advance in carbon monitoring beyond the synoptic capabilities of Low Earth
Orbit instruments such as SCIAMACHY, GOSAT and OCO-2. GCPI follows the paradigm of
numerical weather prediction and aims to provide orders of magnitude improvement in
observational density for atmospheric CO2, CH4, CO, and new measurements of chlorophyll
fluorescence (CF). These new observations could be used to drive and constrain Earth system
models, improve our understanding of the underlying carbon cycle processes and evaluate model
forecasting capabilities. GCPI is designed to deliver simultaneous measurements of CF and
column averaged CO2, CH4 and CO dry air mole fractions to disentangle biogenic and
anthropogenic sources of carbon. Here, we perform radiative transfer simulations over a range of
conditions expected to be observed by GCPI and estimate prospective performance of retrievals
based on results from Bayesian error analysis and characterizations. The potential benefits from
the measurements of CF are also investigated.
Yefeng Pan, Xun Jiang, Edward T Olsen, Thomas S Pagano, Liming Li, Yuk L Yung, 2013,
Investigation of High Latitude CO2 Variability From Satellite Data, Abstract A21G-0135
presented at 2013 Fall Meeting, AGU, San Francisco, CA, 9-13 Dec.
There are few studies on the CO2 variability in the polar region as most previous observations
suffer from limited coverage in time and space in the high latitudes. Recently retrieved CO2data
from satellites offer a unique opportunity to explore the variability of CO2 in the high latitudes.
In this study, we use the Principal Component Analysis method to explore the variability of CO2
in the northern hemispheric high latitude. Atmospheric Infrared Sounder (AIRS) Version 2 CO2
retrieval products are utilized in this study. AIRS CO2 data are available at 2 × 2.5 (latitude by
longitude) from September 2002 to February 2011. A lowpass filter is applied to the CO2 data
for removing high frequency signals with periods shorter than 15 months. The first leading mode
is related to the CO2trend. The second mode is related to the Pacific/North American (PNA)
oscillation. The correlation coefficient between PC2 time series and PNA index is 0.65. The third
mode is related to the Northern Annular Mode (NAM). The corresponding correlation coefficient
between PC3 time series and NAM index is 0.68. These results can help better understand the
influence of large-scale dynamics on the CO2in the polar region
Qiong Zhang, Vijay Natraj, Run-Lie Shia, DejianFu, Clare (Kam Weng) Wong, Thomas J
Pongetti, Stanley P Sander, Yuk L Yung, 2013, Retrieval of Greenhouse Gas in the LA Basin
Using High-Resolution CLARS Measurements, Abstract A21G-0138 presented at 2013 Fall
Meeting, AGU, San Francisco, CA, 9-13 Dec.
Megacities, such as Los Angeles, contribute significantly to the world's greenhouse gas (GHG)
emissions. In these areas, heavy pollution makes aerosol scattering, in particular, important in the
analysis of remote sensing measurements. Since 2011, GHG column abundances in the LA basin
have been measured by the Fourier Transform Spectrometer (FTS) at the California Laboratory
for Atmospheric Remote Sensing (CLARS) located on Mt. Wilson, California. In the presence of
haze, the measured column abundances display a low bias resulting from aerosol scattering in the
near-infrared spectral region. In this study, we use a radiative transfer model to study the
physical mechanism by which aerosols in the Los Angeles basin boundary layer contribute to
this low bias and the feasibility of retrieving CO2 in the presence of aerosol. The retrieval
algorithm is set up and tested with synthetic spectra. We also calculate the degrees of freedom
and information content as a function of signal-to-noise-ratio and resolving power of the
instrument to investigate the possibility of vertical profile retrieval. Retrieval biases caused by
aerosol scattering in both the boundary layer and the free atmosphere are analyzed separately. By
changing aerosol optical depth and solar zenith angle, we obtain the simulated daily variations of
CO2 and O2 slant column densities, and compare the results with CLARS measurements.
Clare (Kam Weng) Wong, Dejian Fu, Thomas JPongetti, Sally Newman, Yuk L Yung, Stanley P
Sander, 2013, Remote sensing of trend and seasonal variability of greenhouse gas emissions
from the Los Angeles basin using an FTS on Mount Wilson, Abstract A12G-0153 presented at
2013 Fall Meeting, AGU, San Francisco, CA, 9-13 Dec.
Cities, such as Los Angeles, are significant sources of anthropogenic greenhouse gases (GHGs).
With the growth of populations in cities worldwide, GHG emissions will increase, and
monitoring the temporal trends will provide crucial data for global climate models as well as
assessments of the effectiveness of control policies. Currently, continuous GHG observations in
the Los Angeles basin are limited to a few in situ measurements, which are shown to be sensitive
to local emissions and do not represent the Los Angeles basin well. To quantify GHG emissions
from the metropolitan area, which tend to have heterogeneous characteristics, it is important to
perform measurements which provide both continuous temporal and spatial coverage of the
domain. Here we present observations of the major greenhouse gases, CO2 and CH4, using a
spectroscopic remote sensing technique from the California Laboratory for Atmospheric Remote
Sensing (CLARS) at Mount Wilson, California (1.7 km elevation). A Fourier Transform
Spectrometer (FTS) deployed at the CLARS site points downward at 28 selected land surfaces in
the Los Angeles basin to measure the slant column abundances of CO2, CH4, N2O, CO and O2
using reflected sunlight in the near-infrared and shortwave infrared regions. This remote sensing
technique provides continuous temporal and spatial measurements in the Los Angeles basin to
achieve the goal of quantifying emissions of GHGs and CO. It also serves as a test-bed for future
geostationary satellite missions to measure GHGs from space such as JPL’s Geostationary
Carbon Process Investigation (GCPI). The path-averaged dry-air mixing ratio,XCO2 and XCH4,
observed by the CLARS FTS, show significant diurnal variability that arises from emissions in
the Los Angeles basin and atmospheric transport processes. High-precision data have been
collected since August 2011. Here we analyze the annual and seasonal trend of the ratio
XCH4:XCO2in the Los Angeles basin observed by the CLARS FTS from August 2011 to
present. This work demonstrates the ability to quantify and track GHG emissions in a megacity
using ground-based remote sensing from an elevated platform and the potential for future
geostationary satellite missions, such as GCPI, to monitor carbon fluxes in cities.
Xi Zhang, Adam P Showman, Yuk L Yung, 2013, General Circulation and Dynamical Transport
of the Jovian Stratosphere, Abstract P21B-1724 presented at 2013 Fall Meeting, AGU, San
Francisco, CA, 9-13 Dec.
Recent Cassini measurements during the Jupiter flyby in 2000 have greatly improved our
understanding of the Jovian stratosphere by revealing several key features: (1) large polar
heating due to solar-energy absorption by aggregated particles (Zhang et al., 2013a); (2) inverse
latitudinal trends between short-lived species (C2H2) and long-lived species (C2H6) in the lower
stratosphere (Zhang et al., 2013b); (3) decaying zonal (east-west) jet structures with altitude in
upper troposphere and lower stratosphere (Flaser et al., 2004, Simon-Miller et al. 2006); (4)
Temperature variations such as the Quasi-Quadrennial Oscillation (QQO) in the lower
stratosphere and pronounced wave-like structures in the upper stratosphere (Zhang et al., 2013b;
Greathouse et al., 2012). From those observations we conclude that a large-scale Brewer-Dobson
type meridional circulation exists in the stratosphere of Jupiter and shapes the tracer transport,
and that the tropospheric waves propagate upward into the stratosphere and could play a
significant role in the eddy-mean flow interaction and vertical and horizontal mixing of the
temperature and tracer distributions. However, the detailed structure of the circulation pattern
and the underlying physical mechanisms of the stratospheric dynamical processes remain
unclear. In this presentation, we investigate this problem from three aspects in order to elucidate
the mechanism: (1) “Diagnostic approach”. We derive the stratospheric residual mean circulation
in the latitude and altitude plane, based on the observed diabatic heating rate under the
Transform Eulerian Mean framework (Andrew et al., 1987). A map of horizontal eddy
diffusivities is obtained from the relative potential vorticity gradient and eddy potential vorticity
flux, by assuming that large-scale, quasi-geostrophic eddies are primarily responsible for the
wave-mean flow interaction and horizontal tracer transport; (2) “Tracer approach”. We introduce
a two-dimensional photochemical-diffusive-advective model to stimulate the distribution of
stratospheric hydrocarbons, under the constraints of the latitudinal distributions of C2H2 and
C2H6 (Zhang et al., 2013b). From that the stratospheric advection and eddy mixing patterns
responsible for the tracer transport are derived. (3) “First Principles approach”. We construct a
three-dimensional stratospheric general circulation model (SGCM) of Jupiter adapted from the
MITgcm. Our simulations will investigate how the interactions between upward propagating
waves and the zonal-mean flow in the stratosphere lead to meridional advection and diffusion.
We will also investigate the mechanisms by which the waves help to maintain the zonal-mean
circulation; particular problems of interest include the decay with height of the zonal jets in the
lower stratosphere and the temperature variations in the upper troposphere and lower
stratosphere. This project was supported by the Bisgrove Fellowship in the University of
Arizona. YLY was supported by NASA NNX09AB72G grant to the California Institute of
Technology.
Peter Gao, Renyu Hu, Yuk L Yung, 2013, Stability of CO2 Atmospheres on Terrestrial
Exoplanets in the Proximity of M Dwarfs, Abstract P21B-1728 presented at 2013 Fall Meeting,
AGU, San Francisco, CA, 9-13 Dec.
M dwarfs are promising targets for the search and characterization of terrestrial exoplanets that
might be habitable, as the habitable planets around M dwarfs are in much more close-in orbits
compared to their counterparts around Sun-like stars. CO2, one of the most important
greenhouse gases on our planet, is conventionally adopted as a major greenhouse gas in studying
the habitability of terrestrial exoplanets around M dwarfs. However, the stability of CO2 in
terrestrial atmospheres has been called into question due to the high FUV/NUV flux ratio of
some M dwarfs in comparison to that of Sun-like stars. While CO2 is photolyzed into CO and O
by photons in the FUV, with O2 forming from the O atoms through third body catalytic
reactions, NUV photons are able to photolyze water, producing HOx radicals which go on to
catalytically recombine the relatively stable CO and O2molecules back into CO2. The
comparatively low NUV flux of some M dwarfs leads to a significantly reduced efficiency of
catalytic recombination of CO and O2 and the possible net destruction of CO2and the build up of
CO and O2. In this work we test the above hypothesis using a 1D photochemical kinetics model
for a Mars-sized planet with an initial atmospheric composition similar to that of Mars and the
incoming stellar flux of a weakly active M dwarf, assuming the exoplanet is 0.1 AU away from
its parent star, in proximity of its habitable zone. We show that a CO2-dominated atmosphere
can be converted into a CO2/CO/O2-dominated atmosphere in 10^3-10^4 years by CO2
photolysis. This process is kept from running away by a combination of O2 photolysis, three
body reactions of O, O2, and another species to form O3, and reactions of CO with OH to form
CO2 and H. However, such a large amount of O2 and CO, combined with some amount of H and
H2, may be susceptible to spontaneous combustion or detonation, and thus could prove to be an
especially unstable state in itself. Thus there could arise a situation whereby a CO2 atmosphere
dissociating into CO and O2 would be periodically and violently converted back into mostly
CO2 due to some "spark". Our simulation results suggest that it is unlikely that CO2 atmospheres
can remain stable on terrestrial planets around M dwarfs with high FUV/NUV flux ratios unless
it is extremely quiescent. Furthermore, any detection of O2 andO3 in such atmospheres is far
more likely to be due to photochemical processes rather than as a result of biology.
Pushkar Kopparla, Vijay Natraj, Robert J D Spurr, Run-Lie Shia, Yuk L Yung, 2013, Fast and
Accurate Shortwave Radiative Flux Calculations for Climate Models Using Principal
Component Analysis, Abstract A33B-0210 presented at 2013 Fall Meeting, AGU, San
Francisco, CA, 9-13 Dec.
Radiative transfer (RT) computations are an essential component of climate models, being used
for calculating the Earth's energy budget. In particular, RT models are required for the generation
of top of the atmosphere radiative fluxes in the long wave and shortwave spectral regions,
especially for aerosol-laden scenarios (Randles et al. [2013]). However, full treatment of RT
processes is computationally expensive, prompting usage of 2-stream approximations in
operational climate models.Natraj et al. [2005, 2010] and Spurr and Natraj [2013] demonstrated
the ability of a technique using principal component analysis (PCA) to speed up RT simulations.
In the PCA method for RT performance enhancement, empirical orthogonal functions are
developed for binned sets of inherent optical properties that possess some redundancy; costly
multiple-scattering RT calculations are only done for those (few) optical states corresponding to
the most important principal components, and correction factors are applied to approximate
radiation fields. Here, we extend the PCA method to a broadband spectral region covering the
ultraviolet, visible and near infrared, including gaseous absorbing regions and intermediate
continua. Top of the atmosphere radiative fluxes are calculated for several scenarios with varying
aerosol type, optical depth, extinction profile and solar zenith angle and comparisons made
between our model and 2-stream methods (such as those used in climate models).We show that
very accurate radiative forcing estimates can be obtained, accounting for multiple scattering by
aerosol, at speeds comparable to 2-stream models.
Xun Jiang, James Houston Trammell III, Liming Li, Yuk L Yung, 2013, Investigation of
Precipitation over Wet and Dry Areas from Observation and Model, Abstract A34E-03 presented
at 2013 Fall Meeting, AGU, San Francisco, CA, 9-13 Dec.
Precipitation plays an important role in the hydrological cycle on Earth. Based on the long-term
(1988-2012) meteorological data sets, our observational study 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. We further investigate
whether the current atmospheric models can quantitatively capture the characteristics of
precipitation from the observation. The NASA Goddard Institute for Space Studies (GISS)
model is used to examine the historic run of the precipitation, in which the historic greenhouse
gases are included. The consistency between the historic simulation from the GISS model and
the observation from the Global Precipitation Climatology Project (GPCP) suggests that the
NASA GISS model can qualitatively capture the temporal trends of precipitation over the wet
and dry areas. However, the precipitation trends are weaker in the model than in the observation.
The observed trends of precipitation do not appear in the control run with the fixed
concentrations of greenhouse gases, which suggests that the global warming due to the historic
increase of the greenhouse gases can influence the temporal variations of precipitation over the
wet and dry areas. Diagnostic studies of other variables (e.g., meridional circulation and vertical
wind) from the GISS model further suggest that enhanced rising air can increase the precipitation
over the wet area. Abundance of cloud from the GISS model is also used to explore its possible
relation with the Precipitation.
Christopher Dennis Parkinson, Stephen W Bougher, Rick Schulte, Peter Gao, Yuk L Yung, AnnCarine Vandaele, Valerie Wilquet, Arnaud Mahieux, Silvia Tellmann, 2013, Analysis of Venus
Express optical extinction due to aerosols in the upper haze of Venus, Abstract P41D-1949
presented at 2013 Fall Meeting, AGU, San Francisco, CA, 9-13 Dec.
Observations by the SPICAV/SOIR instruments aboard the Venus Express(VEx) spacecraft have
revealed that the upper haze (UH) of Venus, between 70 and 90 km, is variable on the order of
days to weeks and that it is populated by two particle modes. Gao et al. (submitted, Icarus, 2013)
posit that one mode is made up of cloud particles that have diffused upwards from the main
sulfuric acid cloud deck below, while the other mode is generated in situ by nucleation of
sulfuric acid droplets on meteoric dust. They also propose that the observed variability in the UH
is caused in part by vertical transient winds. They test this hypothesis by simulating a column of
the Venus atmosphere from 40 to 100 km above the surface using a model based upon the
Community Aerosol and Radiation Model for Atmospheres (CARMA).In this work, we
significantly extend the analysis using the new more detailed SOIR/VeRa Vex temperature
profiles which better constrain the observed strong CO2 15-micron cooling emission and 4.3-µm
near-IR heating in Venus' atmosphere (and consistent with Venus Thermospheric General
Circulation Model (VTGCM) simulations of Brecht et al. (2011)). We discuss our new results in
context of the recent VEx observations (Wilquet et al., Icarus 217, 2012) with an
intercomparison with the PVO data. We will also discuss similarities and differences arising
from the PVO and VEx epochs where they exist. Additionally we report on our efforts selfconsistently applying the VTGCM to constrain the degree to which effects due to vertical
transient wind simulations can establish variability timescales and number density profiles that
match VEx observations.
Hui Su, Jonathan H. Jiang, Chengxing Zhai, J David Neelin, Graeme L Stephens, Yuk L Yung,
Janice T. Shen1, 2013, High Climate Sensitivity Suggested by Multi-satellite Observations: the
Role of Circulation and Cloud Feedback, Abstract A43K-03 presented at 2013 Fall Meeting,
AGU, San Francisco, CA, 9-13 Dec.
It has long been recognized that cloud feedback is a leading contributor to the spread of models’
climate sensitivity. Here we show that simulated cloud feedbacks are strongly correlated with the
changes of the Hadley Circulation. We further show the present-day simulations of circulation
and clouds have imprints that foreshadow the strength of circulation and cloud feedback under
global warming. Compared with multi-satellite observations and reanalysis data, the high
sensitivity models perform better than the low sensitivity models. Using observational metrics
that emphasize the coherent spatial variabilities of clouds and relative humidity in association
with the Hadley Circulation, we find the best estimates of equilibrium climate sensitivity likely
range from 3.6 to 4.7 K, with a mean of 4.1K and a standard deviation of 0.4 K.
Sally Newman, Yik Hong Wong, Hung-I Lee, King-Fai Li, Xiaomei Xu, Jennifer Campbell, Yuk
L Yung, 2013, Natural Variabilities and Trends in CO2 from the Los Angeles Megacity
Measured Over 15 Years, Abstract A51J-03 presented at 2013 Fall Meeting, AGU, San
Francisco, CA, 9-13 Dec.
Urban regions are the dominant sources of greenhouse gases, comprising over80% of global
anthropogenic emissions while covering just ~3% of the land. Although urban CO2 domes result
in large signals for monitoring cycles and trends, they are affected by many processes, both
natural and man-made. For example, background air is affected by global patterns as observed at
remote sites, and local meteorology modifies anthropogenic and biogenic sources. All of these
processes must be disentangled before we can understand the trends caused by human activities.
Here we show results from 15 years of flask sampling of CO2 in air from Pasadena, CA, a good
receptor site for the Los Angeles basin. We use the time series of mid-afternoon data to look at
the processes operating on weekly, seasonal, and inter-annual time-scales. We observe long
natural oscillations such as ENSO. A distinct annual cycle is observed, but it is out of phase with
the natural cycle.
Jiabin Liu, Le Kuai, Run-Lie Shia, Qiong Zhang, Dejian Fu, Stanley P Sander, Hartmut H
Aumann, Thomas J Pongetti, Yuk L Yung, 2013, Retrieval of Atmospheric Concentrations for
Ecosystem Studies, Abstract B51C-0288 presented at 2013 Fall Meeting, AGU, San Francisco,
CA, 9-13 Dec.
Remote sensing of Earth’s atmosphere is a powerful tool to investigate various ecosystem
structures. The forest canopy structure, in particular, influences the water vapor and CO2 in the
atmosphere and has impact on the solar radiance of satellite measurements. In our study, Lineby-line Radiative Transfer Model (LBLRTM) and a two-stream analytical model are combined
to retrieve the water vapor, temperature, and CO2 in the boundary layer, based on the thermal
infrared observation from space. Degrees of freedom (DOF) and information content (IC) of the
retrieval are also calculated to show the efficiency of vertical profile retrieval for each gaseous
species. The retrieved information helps pin down the physical structure of the canopy and its
influence. Based on our studies, we also suggest the ideal retrieval windows and resolution for a
Moderate-resolution Infrared Imaging Sounder (MIRIS), a conceptual instrument for future at a
comparatively lower cost with equally good or better performance with AIRS.
Shuhui Wang, King-Fai Li, Luis F Millan Valle, Stanley P Sander, Yuk L Yung, Nathaniel J
Livesey, Michelle L Santee, Mao-Chang Liang, 2013, Solar Cycle Induced Variability in the
Abundances and Partitioning of Atmospheric HOx, Abstract GC54A-05 presented at 2013 Fall
Meeting, AGU, San Francisco, CA, 9-13 Dec.
Solar UV irradiance variability during the 11-year solar cycle has been shown to have strong
impacts on Earth’s atmospheric composition and climate. The odd hydrogen species (primarily
OH and HO2), which plays a key role in controlling middle atmospheric ozone, are expected to
show distinct variability following the solar cycle. Wang et al. [PNAS, 2013] compared the solar
cycle signal in OH column abundances from ground-based and satellite observations with model
calculations, suggesting that the HOx solar cycle variability may dominate the ozone solar cycle
variability at the altitudes of 40 -60km and that the uncertainty in solar spectral irradiance
variability during Solar Cycle 23 is a major source of discrepancies between models and
observations. In the present study, we investigate the solar cycle-induced variability in both OH
and HO2, as well as the partitioning between them, which is important in the catalytic HOx cycle
that destroys ozone. We examine in detail the vertical distribution of the solar cycle signals in
OH and HO2 based on global observations from Aura Microwave Limb Sounder (MLS) (5.5year OH data and 9-year HO2 data) and model simulations using the Whole Atmospheric
Community Model (WACCM) and the Caltech/JPL 1-D photochemical model. The results of
using different solar spectral irradiance (SSI) variabilities in models and the comparison with
observations will be discussed.