S. R. Kawa's research while affiliated with NASA Johnson Space Center and other places

Publications (200)

Article
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Atmospheric carbon dioxide (CO2) inversions for estimating natural carbon fluxes typically do not allow for adjustment of fossil fuel CO2 emissions, despite significant uncertainties in emission inventories and inadequacies in the specification of international bunker emissions in inversions. Also, most inversions place CO2 release from fossil fuel...
Article
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Improved remote sensing observations of atmospheric carbon dioxide (CO2) are critically needed to quantify, monitor, and understand the Earth’s carbon cycle and its evolution in a changing climate. The processes governing ocean and terrestrial carbon uptake remain poorly understood, especially in dynamic regions with large carbon stocks and strong...
Article
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The precise contribution of the two major sinks for anthropogenic CO2 emissions, terrestrial vegetation and the ocean, and their location and year-to-year variability are not well understood. Top-down estimates of the spatiotemporal variations in emissions and uptake of CO2 are expected to benefit from the increasing measurement density brought by...
Article
Space-borne observations of CO2 are vital to gaining understanding of the carbon cycle in regions of the world that are difficult to measure directly, such as the tropical terrestrial biosphere, the high northern and southern latitudes, and in developing nations such as China. Measurements from passive instruments such as GOSAT and OCO-2, however,...
Article
Full-text available
The precise contribution of the two major sinks for anthropogenic CO2 emissions, terrestrial vegetation and the ocean, and their location and year-to-year variability are not well understood. Top-down estimates of the spatiotemporal variations in emissions and uptake of CO2 are expected to benefit from the increasing measurement density brought by...
Article
According to current budget estimations the seasonal variation of carbonyl sulfide (COS) is governed by oceanic release and vegetation uptake. Its assimilation by plants is assumed to be similar to the photosynthetic uptake of CO2 but, contrary to the latter process, to be irreversible. Therefore, COS has been suggested as cotracer of the carbon cy...
Conference Paper
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For several years now, NASA has supported observing system simulation studies to evaluate measurement capabilities and requirements for the ASCENDS mission in the context of advancing our knowledge of carbon flux distributions and their dependence on underlying physical processes. ASCENDS (Active Sensing of Carbon Emissions, Nights, Days, and Seaso...
Article
Future space-borne lidar missions are foreseen to measure global concentrations of methane, carbon dioxide and aerosols with high sensitivity and to relate the concentrations to their surface sources and sinks. Therefore, full visibility down to the surface is required. We use CALIPSO (Cloud- Aerosol Lidar and Infrared Pathfinder Satellite Observat...
Article
Satellite observations of carbon dioxide (CO2) offer novel and distinctive opportunities for improving our quantitative understanding of the carbon cycle. Prospective observations include those from space-based lidar such as the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. Here we explore the ability of such a m...
Article
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Top–down estimates of the spatiotemporal varia- tions in emissions and uptake of CO2 will benefit from the increasing measurement density brought by recent and fu- ture additions to the suite of in situ and remote CO2 mea- surement platforms. In particular, the planned NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) sa...
Conference Paper
Future space-based lidar measurements of anthropogenic greenhouse gases are expected to close observational gaps particularly over remote, polar, and aerosol-contaminated regions where in-situ and passive remote sensing observation techniques have difficulties. Recently, a “Methane Remote Lidar Mission” (MERLIN) was proposed by DLR and CNES in the...
Article
Future spaceborne lidar measurements of key anthropogenic greenhouse gases are expected to close current observational gaps particularly over remote, polar, and aerosol-contaminated regions where actual in-situ and passive remote sensing observation techniques have difficulties. For methane, a “Methane Remote Lidar Mission” (MERLIN) was proposed by...
Article
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We investigate the sensitivity of future spaceborne lidar measurements to changes in surface methane emissions. We use surface methane observations from nine European ground stations and a Lagrangian transport model to infer surface methane emissions for 2010. Our inversion shows the strongest emissions from the Netherlands, the coal mines in Upper...
Conference Paper
Space-based remote sensing observations, such as those available from the Greenhouse gases Observing SATellite “IBUKI” (GOSAT) hold great promise for improving the scientific understanding of carbon cycle processes and budgets at regional and global scales. The degree to which the GOSAT CO2 total column (XCO2) observations can constrain global fine...
Article
NASA Goddard is developing an integrated-path, differential absorption (IPDA) lidar approach to measure atmospheric CO2 concentrations from space as a candidate for NASA’s ASCENDS (Active Sensing of CO2 Emissions over Nights, Days, and Seasons) mission. The approach uses pulsed lasers to measure both CO2 and O2 absorption simultaneously in the vert...
Article
The measurement of atmospheric CO2 from space using active (lidar) sensing techniques has several potentially significant advantages in comparison to current and planned passive CO2 instruments. Application of this new technology aims to advance CO2 measurement capability and carbon cycle science into the next decade. The NASA Active Sensing of Car...
Article
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A modelling experiment has been conceived to assess the impact of transport model errors on methane emissions estimated in an atmospheric inversion system. Synthetic methane observations, obtained from 10 different model outputs from the international TransCom-CH4 model inter-comparison exercise, are combined with a prior scenario of methane emissi...
Article
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In any data assimilation framework, the background error covariance statistics play the critical role of filtering the observed information and determining the quality of the analysis. For atmospheric CO2 data assimilation, however, the background errors cannot be prescribed via traditional forecast or ensemble-based techniques as these fail to acc...
Article
Full-text available
We investigate the sensitivity of future space-borne lidar measurements to changes in surface methane emissions. We use surface methane observations from nine European ground stations, and a Lagrangian transport model to obtain surface methane emissions for 2010. Our inversion shows the strongest emissions from the Netherlands, the coalmines in Upp...
Article
To assess horizontal and vertical transports of methane (CH4) concentrations at different heights within the troposphere, we analyzed simulations by 12 chemistry transport models (CTMs) that participated in the TransCom-CH4 intercomparison experiment. Model results are compared with aircraft measurements at 13 sites in Amazon/Brazil, Mongolia, Paci...
Article
Full-text available
A modelling experiment has been conceived to assess the impact of transport model errors on the methane emissions estimated by an atmospheric inversion system. Synthetic methane observations, given by 10 different model outputs from the international TransCom-CH4 model exercise, are combined with a prior scenario of methane emissions and sinks, and...
Article
[1] Estimates of surface fluxes of carbon dioxide (CO2) can be derived from atmospheric CO2 concentration measurements through the solution of an inverse problem, but the sparseness of the existing CO2 monitoring network is often cited as a main limiting factor in constraining fluxes. Existing methods for assessing or designing monitoring networks...
Article
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A modified cumulus convection parametrisation scheme is presented. This scheme computes the mass of air transported upward in a cumulus cell using conservation of moisture and a detailed distribution of convective precipitation provided by a reanalysis dataset. The representation of vertical transport within the scheme includes entrainment and detr...
Article
A modified cumulus convection parametrisation scheme is presented. This scheme computes the mass of air transported upward in a cumulus cell using conservation of moisture and a detailed distribution of convective precipitation provided by a reanalysis dataset. The representation of vertical transport within the scheme includes entrainment and detr...
Conference Paper
Laser instruments designed to measure methane from air- and space-borne platforms are being developed at DLR (MERLIN) and at NASA (GSFC Methane Sounder). Designing these instrument with sufficient accuracy to advance our understanding of emission source strengths and locations is crucial. Here we present a model simulation of methane used to test t...
Article
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THE UNITED STATES' NEXT GENERATION OF ATMOSPHERIC COMPOSITION AND COASTAL ECOSYSTEM MEASUREMENTS: NASA'S GEOSTATIONARY COASTAL AND AIR POLLUTION EVENTS (GEO-CAPE) MISSION The Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission was recommended by the National Research Council's (NRC's) Earth Science Decadal Survey to measure tropospher...
Article
Full-text available
A modified cumulus convection parametrisation scheme is presented. This scheme computes the mass of air transported upward in a cumulus cell using conservation of moisture and a detailed distribution of convective precipitation provided by a reanalysis dataset. The representation of vertical transport within the scheme includes entrainment and detr...
Article
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Vertical transport by moist sub-grid scale processes such as deep convection is a well-known source of uncertainty in CO2 source/sink inversion. However, a dynamical link between vertical transport, satellite based retrievals of column mole fractions of CO2, and source/sink inversion has not yet been established. By using the same offline transport...
Article
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Vertical transport by moist sub-grid scale processes such as deep convection is a well-known source of uncertainty in CO2 source/sink inversion. However, a dynamical link between moist transport, satellite CO2 retrievals, and source/sink inversion has not yet been established. Here we examine the effect of moist processes on (1) synoptic CO2 transp...
Article
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January 2009 saw the successful launch of the first space-based mission specifically designed for measuring greenhouse gases, the Japanese Greenhouse gases Observing SATellite (GOSAT). We present global land maps (Level 3 data) of column-averaged CO2 concentrations (XCO2) derived using observations from the GOSAT ACOS retrieval algorithm, for July...
Article
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[1] Satellite observations of CO2 offer new opportunities to improve our understanding of the global carbon cycle. Using such observations to infer global maps of atmospheric CO2 and their associated uncertainties can provide key information about the distribution and dynamic behavior of CO2, through comparison to atmospheric CO2 distributions...
Article
Change of the NRC report. The U.S. National Research Council (NRC), at the request of the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA), and the U.S. Geological Survey, conducted an Earth Science Decadal Survey review to assist in planning the next generation of Earth science satell...
Article
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A chemistry-transport model (CTM) intercomparison experiment (TransCom-CH4) has been designed to investigate the roles of surface emissions, transport and chemical loss in simulating the global methane distribution. Model simulations were conducted using twelve models and four model variants and results were archived for the period of 1990–2007. Al...
Article
Errors in the retrieval of column-average CO2 concentration (XCO2) from GOSAT satellite data have dropped to the point where it now makes sense to use these data in flux inversion studies. Recent spectroscopic refinements in NASA/JPL's ACOS retrievals, for example, have brought systematic errors down into the 1-2 ppm range, while random errors are...
Article
We present results from our summer 2010 CO2 measurement campaign using the NASA Goddard CO2 lidar sounder onboard the NASA DC-8 aircraft platform. This instrument is a candidate for NASA's ASCENDS space mission. The airborne instrument steps a pulsed wavelength-tunable laser transmitter across the 1572.33 nm CO2 line in thirty steps at a 300 Hz rep...
Article
Many components of the carbon cycle are constrained by a variety of remote sensing measurements. Observations of land surface parameters constrain estimates of carbon flux from terrestrial biosphere models while estimates of oceanic carbon fluxes are informed by satellite observations of ocean color and ocean properties. Atmospheric CO2 concentrati...
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Inverse methods to estimate fluxes of carbon dioxide (CO2) rely on networks of atmospheric CO2 measurements. The current network of continuous observations in North America has grown from 9 continuous CO2 monitoring towers in 2004 to approximately 35 in 2008. Despite its growth, however, the sparse network of monitoring stations has been a limiting...
Article
The CarbonTracker atmospheric CO2 analysis system historically has used one atmospheric transport model (TM5 with ECMWF forecast model winds), one terrestrial biosphere model (a CASA variant used by the GFED fire emissions project), and one model each of air-sea exchange and fossil fuel emissions of carbon dioxide. While careful attention has been...
Article
We assess the ability of different proposed CO2 lidar measurement approaches to constrain surface CO2 fluxes, as part of the development of science requirements for NASA's ASCENDS mission. Observing system simulation experiments (OSSEs) are performed for different overall measurement uncertainty levels and vertical weightings to determine what desi...
Article
Several NASA groups have developed integrated path differential absorption (IPDA) lidar approaches to measure atmospheric CO2 concentrations from space as a candidates for NASA's ASCENDS space mission. For example, the Goddard CO2 Sounder approach uses two pulsed lasers to simultaneously measure both CO2 and O2 absorption in the vertical path to th...
Article
We compare global variations in atmospheric CO2 concentrations using a comprehensive model of surface carbon cycling and atmospheric transport to retrievals of column CO2 mole fraction from near-infrared spectroscopy from the GOSAT mission. Surface carbon exchanges due to photosynthesis, respiration, decomposition, biomass burning, fossil fuel comb...
Article
The advent of atmospheric CO2 observations from satellites provides new opportunities for improving our knowledge of the carbon cycle and to verify its representation in biospheric, oceanic, inventory, and atmospheric models. We present a novel approach for comparing CO2 observations from satellites to models. We attempt to answer the following que...
Article
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Atmospheric mixing ratios of CO2 are strongly seasonal in the Arctic due to mid-latitude transport. Here we analyze the seasonal influence of moist synoptic storms by diagnosing CO2 transport from a global model on moist isentropes (to represent parcel trajectories through stormtracks) and parsing transport into eddy and mean components. During win...
Article
We present our first results of CO2 surface biosphere fluxes and global atmospheric CO2 transport using NASA's new MERRA reanalysis data. MERRA is the Modern Era Retrospective-Analysis For Research And Applications based on the Goddard Global Modeling and Assimilation Office GEOS-5 data assimilation system. After some application testing and analys...
Article
NASA launched science flight campaigns in summers 2009 and 2010 for future space mission ASCENDS (the Active Sensing of CO2 Emissions over Nights, Days and Seasons). Three NASA laser approaches currently under development in the Goddard Space Flight Center (GSFC), the Langley Research Center and the Jet Propulsion Laboratory flew and tested during...
Article
We report on airborne atmospheric pressure measurements using new fiber-based laser technology and the oxygen A-band at 765 nm. Remote measurements of atmospheric temperature and pressure are required for a number of NASA Earth science missions and specifically for the Active Sensing of CO2 Emissions Over Nights, Days, and Seasons (ASCENDS) mission...
Article
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A method for evaluating the North America in-situ atmospheric carbon dioxide (CO2) monitoring network is presented. In-situ atmospheric CO2 measurements represent an integral component of inverse modeling and data assimilation studies aimed at estimating North American terrestrial CO2 sources and sinks. The sparse network of monitoring locations ha...
Conference Paper
In recent years, many new observation streams, such as (GOSAT) satellite retrievals, have become available that provide information on surface carbon fluxes. Satellites provide global coverage but are limited in some areas due to clouds and aerosols. It is important to know what we can learn by adding these new observations compared to the existing...
Article
Transport by baroclinic waves in the mid-latitude storm track is a poorly-resolved process which controls the distribution of atmospheric trace gases on synoptic to seasonal time scales. Synoptic transport of CO2 involves strong vertical and meridional motion and is correlated with ecosystem metabolism because large-scale baroclinicity and photosyn...
Article
We report recent progress derived from comparison of global CO2 flux and transport models with new remote sensing and other sources of CO2 data including those from satellite. The overall objective of this activity is to improve the process models that represent our understanding of the workings of the atmospheric carbon cycle. Model estimates of C...
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We evaluate North American carbon fluxes using a monthly global Bayesian synthesis inversion that includes well-calibrated carbon dioxide concentrations measured at continental flux towers. We employ the NASA Parametrized Chemistry Tracer Model (PCTM) for atmospheric transport and a TransCom-style inversion with subcontinental resolution. We subsam...
Article
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We report results of initial space mission simulation studies for a laser-based, atmospheric CO2 sounder, which are based on real-time carbon cycle process modelling and data analysis. The mission concept corresponds to the Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) recommended by the US National Academy of Sciences’ De...
Conference Paper
NASA Goddard Space Flight Center is developing an active laser approach for global atmospheric CO2 concentration measurement from space as a candidate for NASA's future mission ASCENDS - the Active Sensing of CO2 Emissions over Nights, Days, and Seasons. This pulsed laser approach provides several advantages with respect to passive approaches and o...
Article
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We evaluate the GEOS-Chem atmospheric transport model (v8-02-01) of CO<sub>2</sub> over 2003–2006, driven by GEOS-4 and GEOS-5 meteorology from the NASA Goddard Global Modelling and Assimilation Office, using surface, aircraft and space-borne concentration measurements of CO<sub>2</sub>. We use an established ensemble Kalman filter to estimate a po...
Article
The National Research Council of the U.S. National Academies has recommended a future space mission called Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) in its Decadal Survey. This mission aims 'to produce global atmospheric column CO2 measurements without seasonal, latitudinal, or diurnal bias using simultaneous laser re...
Article
Stratospheric ozone is expected to increase during the 21st century as the abundance of halogenated ozone-depleting substances decrease to 1960 values. However, climate change will likely alter this "recovery" of stratospheric ozone by changing stratospheric temperatures, circulation, and abundance of reactive chemical species. Here we quantify the...
Article
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Recent in situ and satellite measurements suggest a contribution of ~5 pptv to stratospheric inorganic bromine from short-lived bromocarbons. We conduct a modeling study of the two most important short-lived bromocarbons, bromoform (CHBr<sub>3</sub>) and dibromomethane (CH<sub>2</sub>Br<sub>2</sub>), with the Goddard Earth Observing System Chemistr...
Article
The NASA Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission was recommended for launch in the second phase of missions (2013-2016) by the 2007 U.S. National Research Council Earth Science Decadal Survey, ``Earth Science and Applications from Space.'' The mission's purpose is to identify human versus natural sources of aerosols and oz...
Article
The purpose of calculating variability metrics from atmospheric measured and modeled 4-D fields is to defining the spatial and temporal scale requirements for GEO-CAPE for the purposes of 1) characterizing emission patterns and 2) observing the spatio-temporal evolution of pollution processes. We present these metrics (e.g., autocorrelations, cross...
Article
We present a system to analyze GOSAT/Tanso data using a combination of existing models of CO2 exchanges due to hourly photosynthesis and respiration, daily air-sea gas exchange, biomass burning, Fossil Fuel Emissions, and atmospheric transport. This comprehensive system allows direct comparison to the observed record of both in-situ and remotely se...
Article
Stomata play a key role in controlling the carbon and water cycles and can influence regional climate. We currently use empirical models calibrated from laboratory experiments to model stomata in natural canopies, and we test these models against measurements of latent heat and carbon dioxide fluxes from forests and fields. In many systems net radi...