A54C-01
Defining Requirements for Future Satellite Air Quality Chemistry Observations
If a satellite mission related to atmospheric composition and air quality is to become a reality within the next decade, the atmospheric chemistry community will need to establish clear scientific motivation for the new measurements. For this, there is considerable interest in using chemical observing system simulation experiment (OSSE) studies to help define quantitative measurement requirements for satellite missions and to evaluate the expected performance of proposed observing strategies. These experiments will hopefully provide a practical way of defining a traceability matrix mapping science requirements through measurement requirements onto instrument requirements. OSSEs must be driven by well-defined scientific questions and the experiment formulation constructed accordingly. We present a framework for this comprising the following key elements: (1) a science-driven requirement for a chemical species observation, (2) a satellite instrument simulator and observing strategy that might be capable of making a useful measurement, (3) a simulated retrieval of the species with nature defined by an appropriate chemical transport model, (4) a forecast of the species distribution using an assimilation of the retrieval in the model, and (5) a quantitative assessment of the value of the measurement. This will be illustrated with an example OSSE motivated by the desire to measure the distribution and time evolution of carbon monoxide in the lower-most troposphere for air quality applications using candidate satellite multispectral measurements in the thermal and near infrared.
A54C-02
Global Monitoring of Tropospheric Pollution from Geostationary Orbit
Tropospheric pollution measurements from space now include ozone (O3), volatile organic compounds (VOCs, using tropospheric formaldehyde - HCHO - as the primary proxy for VOCs), and odd nitrogen (NOx, using tropospheric nitrogen dioxide - NO2 - as the proxy for NOx), glyoxal (CHOCHO, an alternate proxy for VOCs, currently being developed), sulfur dioxide (SO2), carbon monoxide (CO), methane (CH4), and water (H2O). Satellite measurements of these gases have been robustly demonstrated and are now routinely made. Data analysis algorithms for analyzing these gases are mature. Geostationary measurements are the logical next step in pollution monitoring from space. This presentation discusses the capabilities and limitations for geostationary monitoring of pollution, and presents requirements for the instrument design and observations. Ultraviolet/visible measurement requirements and implementation for O3, NO2, HCHO, CHOCHO, and SO2 are presented in detail. Infrared measurements approaches for CO, CH4, and O3 are discussed and some novel approaches for their measurement presented.
A54C-03
MOPITT Retrieval Performance in Extreme Pollution Conditions
Satellite-based methods for determining trace gas concentrations must be applicable in widely varying contexts. We analyze the performance of the MOPITT (Measurements of Pollution In The Troposphere) retrieval algorithm for carbon monoxide (CO) in strongly polluted atmospheres. In such conditions, retrievals of CO vertical profiles based on MOPITT observations might be degraded by at least two distinct sources of retrieval error. First, the accuracy of the operational radiative transfer model for MOPITT might be lower in conditions marked by extremely high CO loading than in more typical situations. Second, the radiative effects of aerosols, which are neglected in the operational retrieval algorithm, can potentially mask the spectral signature of CO in the upwelling radiation. In both cases, systematic differences between the calibrated radiances and model-calculated radiances can lead to biases in the CO product. We exploit a variety of approaches to investigate these potential sources of retrieval error. The effect of anomalously high CO mixing ratios can be evaluated directly by retrieval simulations; results based on the regression-based operational forward model are compared with results based on a much more accurate (line- by-line grade) forward model. The effects of aerosols on retrieval quality are more easily analyzed by empirical methods. For example, using near-simultaneous observations of MOPITT and MODIS, errors in MOPITT retrieved sea surface temperature (SST) can be related to MODIS retrievals of aerosol optical depth (AOD). Because MOPITT retrievals of SST exploit a shorter-wavelength infrared spectral band compared to MODIS, they should be more sensitive to the presence of aerosols. Correlation of the SST error and MODIS AOD provides indirect evidence of the effect of aerosols on the MOPITT radiances.
A54C-04
Combining TES Ozone with GOES Water Vapor to Discern Dynamically Driven Stratospheric Enhancements in the Upper Troposphere
As part of NASA INTEX-B we report on a satellite based empirical method for estimating the amount of stratospheric ozone present in the upper-troposphere (UT). To understand the role of anthropogenic emissions on ozone mixing ratios in the non-urban troposphere, it is vital to describe the dynamically variable background, which is influenced by the natural exchange of stratospheric ozone. Our derived product is based on the relationship between three quantities, 1) satellite measurements of UT ozone from the Tropospheric Emission Spectrometer (TES), 2) estimates of GOES Layer Average Specific Humidity (GLASH) based on the GOES water vapor channel, and 3) the dynamical tracer Potential Vorticity (PV) from the Global Forecast System model. The TES instrument, on the Aura satellite, produced nadir curtains of ozone mixing ratio. TES profiles were used to create a series of layer-averaged ozone values employing the weighting function for the atmospheric layer observed in the GLASH product, with a maximum contribution from 300-400hPa. Model PV was similarly weighted such that all three products describe the same layer. Atmospheric dynamics are a major control on ozone in this layer where stratospheric enhancements are associated with dry intrusions of PV rich air. Preliminary analyses using 22 TES overpasses (2570 TES retrievals from April and May, 2006) exhibit a strong correlation to the dynamical tracers. A Reduced Major Axis (RMA) linear regression of ozone and GLASH brightness temperatures (inversely related to specific humidity) results in an r2 of 0.67; the RMA analysis of ozone and PV results in an r2 of 0.76. A multiple regression using both GLASH and PV values in a least-squares fit of TES ozone results in an r2 of 0.82. Given that over 80% of the TES variability in the UT is explained by variations in dynamical tracers, we have used this relationship, and the coverage of the GOES product to derive a satellite based image of dynamically variable ozone in the UT.
A54C-05
Inferring Ground-level Nitrogen Dioxide Concentrations From OMI
Surface NO2 concentrations are strongly associated with mortality. We present an approach to infer ground- level NO2 concentrations using tropospheric NO2 columns from the OMI satellite instrument and NO2 profile shapes from a global chemical transport model (GEOS-Chem). The derived surface NO2 concentrations are compared with in situ NO2 data from 214 monitoring sites from the AQS/NAPS networks in the United States and Canada. Laboratory and field measurements are used to develop and test a correction algorithm for interference by reactive nitrogen in the in-situ ground- based measurements. The OMI derived ground-level NO2 data exhibit significant agreement with the corrected in situ measurements. This comparison not only demonstrates the capability of monitoring surface air quality from space but also serves as an indirect validation of the OMI tropospheric NO2 columns.
A54C-06
Three-Dimensional Air Quality System (3D-AQS)
The 3-Dimensional Air Quality System (3DAQS) integrates remote sensing observations from a variety of platforms into air quality decision support systems at the U.S. Environmental Protection Agency (EPA), with a focus on particulate air pollution. The decision support systems are the Air Quality System (AQS) / AirQuest database at EPA, Infusing satellite Data into Environmental Applications (IDEA) system, the U.S. Air Quality weblog (Smog Blog) at UMBC, and the Regional East Atmospheric Lidar Mesonet (REALM). The project includes an end user advisory group with representatives from the air quality community providing ongoing feedback. The 3DAQS data sets are UMBC ground based LIDAR, and NASA and NOAA satellite data from MODIS, OMI, AIRS, CALIPSO, MISR, and GASP. Based on end user input, we are co-locating these measurements to the EPA's ground-based air pollution monitors as well as re-gridding to the Community Multiscale Air Quality (CMAQ) model grid. These data provide forecasters and the scientific community with a tool for assessment, analysis, and forecasting of U.S Air Quality. The third dimension and the ability to analyze the vertical transport of particulate pollution are provided by aerosol extinction profiles from the UMBC LIDAR and CALIPSO. We present examples of a 3D visualization tool we are developing to facilitate use of this data. We also present two specific applications of 3D-AQS data. The first is comparisons between PM2.5 monitor data and remote sensing aerosol optical depth (AOD) data, which show moderate agreement but variation with EPA region. The second is a case study for Baltimore, Maryland, as an example of 3D-analysis for a metropolitan area. In that case, some improvement is found in the PM2.5 /LIDAR correlations when using vertical aerosol information to calculate an AOD below the boundary layer. http://alg.umbc.edu/3D-AQS/
A54C-07
A Satellite-based Assessment of Trans-Pacific Transport of Pollution Aerosol
It has been well documented that pollution aerosol and dust from East Asia can transport across the North Pacific basin, reaching North America and beyond. Such intercontinental transport extends the impact of aerosols for climate change, air quality, atmospheric chemistry, and ocean biology from local and regional scales to hemispheric and global scales. Long term, measurement-based studies are necessary to adequately assess the implications of these wider impacts. A satellite-based assessment can augment intensive field campaigns by expanding temporal and spatial scales and also serve as constraints for model simulations. Satellite imagers have been providing a wealth of evidence for the intercontinental transport of aerosols for more than two decades. Quantitative assessments, however, became feasible only recently as a result of the much improved measurement accuracy and enhanced new capabilities of satellite sensors. In this study, we generated a 4-year (2002 to 2005) climatology of optical depth for pollution aerosol (defined as a mixture of aerosols from urban/industrial pollution and biomass burning in this study) over the North Pacific from MODerate resolution Imaging Spectro-radiometer (MODIS) observations of fine- and coarse-mode aerosol optical depths. The pollution aerosol mass loading and fluxes were then calculated using measurements of the dependence of aerosol mass extinction efficiency on relative humidity and of aerosol vertical distributions from field campaigns and available satellite observations in the region. We estimated that about 18 Tg/year pollution aerosol is exported from East Asia to the northwestern Pacific Ocean, of which about 25% reaches the west coast of North America. The pollution fluxes are largest in spring and smallest in summer. For the period we have examined the strongest export and import of pollution particulates occurred in 2003, due largely to record intense Eurasia wildfires in spring and summer. The overall uncertainty of pollution fluxes is estimated at about 80%. A reduction of uncertainty can be achieved with a better characterization of pollution aerosol through integrating emerging A- Train measurements. Simulations by the Goddard Chemistry Aerosol Radiation and Transport (GOCART) and Global Modeling Initiative (GMI) models agree quite well with the satellite-based estimates of annual and latitude- integrated fluxes, with larger model-satellite differences in latitudinal variations of fluxes.
A54C-08
Use of TES, AIRS and other satellite data for evaluation of air quality modeling efforts by the Texas Commission on Environmental Quality
Currently, one of the most pressing air quality issues for the state of Texas is surface ozone. The cities of Houston and Dallas are both in violation of the EPA air quality standard for 8-hour concentration of surface ozone. The Texas Commission on Environmental Quality (TCEQ) uses the CAMx air quality model to study scenarios for reducing emissions to bring the state into agreement with EPA requirements. The results from the model analyses are incorporated into the State Implementation Plan (SIP) that provides the detailed procedures by which the state will improve air quality in the future. We present preliminary results in trying to use satellite data to understand how the air quality models are doing in the free troposphere and in regions where there are no ground station data available. We will focus on the use of TES data to evaluate ozone and carbon monoxide fields from CAMx and outline our plans to incorporate data from AIRS and other satellite instruments into the analysis.