A53H-01
Long-Range Transport of Asian Sulfate and Its Effects on the Canadian Sulfate Burden
Anthropogenic sulfur emissions from East Asia have grown significantly in the past decade. Long-range transport of Asian aerosol affects surface air quality and climate in North America. Using a satellite-based approach, we develop a spatially resolved estimate of sulfur dioxide emission growth in East Asia. We assess the effect of these emissions on Canadian air quality in Spring 2006. We use a chemical transport model (GEOS-Chem) to interpret aircraft measurements (DC-8, C130 and Cessna) from the Intercontinental Chemical Transport Experiment Phase B (INTEX-B) and satellite measurements (OMI, MODIS and MISR). The Canadian component of INTEX-B included 33 vertical profiles from a Cessna 207 aircraft equipped with an aerosol mass spectrometer. Measured sulfate plumes in the free troposphere over British Columbia exceeded 1 ug/m3 and are attributed primarily to Asian sources. Substantial Asian enhancements from organic or nitrate aerosol are not observed. Anthropogenic East Asian sulfur emissions increase mean springtime sulfate in Western Canada at the surface by 0.10-0.15 ug/m3 (20-30%) and account for 40% of the overall regional sulfate burden between 1 and 6 km.
A53H-02
Dragon Breath in the American West: Inter-Annual Correlations Between Dust Storms in Asia and PM10 in the Western U.S. as Seen by IMPROVE and MODIS Data
The deserts of western China and Mongolia are large sources of atmospheric dust on a hemispheric scale especially during spring when meteorological conditions are most favorable for lofting and long range transport. Specific case studies and long-term records have shown that there can be significant surface particulate matter impacts in North America from Asian dust. Our preliminary analysis using the number of Asian dust storms each spring indicates a strong correlation with PM10 in the western United States. In this work we extend this analysis to include MODIS maps of aerosol properties determined from the Deep Blue algorithm. We use area- averaged aerosol optical thickness (AOD) over the two main dust source regions, the Taklamakan Desert and the Gobi Desert, with surface aerosol observations from the IMPROVE network in the western United States. The Deep Blue algorithm provides an enhanced measure of AOD over these highly reflective dust source regions, while the IMPROVE data provides a policy-relevant measure of aerosol concentrations in the United States. Preliminary results based on three years of data show a strong correspondence between the inter-annual variations in area-averaged AOD over the Asian deserts and seasonally averaged PM10 and fine Ca2+ mass in the western United State. This work is being extended to include spring 2000 through 2006. The additional data will provide insight into factors responsible for the relationship between these two distant but related measures of air quality. We hypothesize that these factors will include meteorological conditions, transport pathways, and satellite sampling frequency.
A53H-03
Evaluation of the use of high spatial resolution AOD retrievals from MODIS on air quality monitoring system in urban areas
The aerosol quality monitoring system in most mega-cities is based on a network of ground-based stations essentially measuring aerosol mass concentrations in one or two particle size ranges (usually PM10 and PM2.5). Satellite retrieval of aerosol optical depth (AOD) over urban areas has become an extremely important additional source of aerosol data as urbanization increases exponentially worldwide, and is critical in megacities without ground-based networks. Progress in this satellite domain will provide an alternative tool to complement the monitoring of urban air-pollution control efforts. Recent studies have compared quantitative AOD data from the MODIS sensor on the Terra and Aqua satellite (10 km x 10 km pixels) with data from ground-based particulate matter monitoring networks and have shown that the remote sensing product can be used quantitatively to estimate PM2.5 under certain conditions. Nevertheless, major improvements in the accuracy and spatial resolution of the satellite products are required for air quality applications in urban areas. We discuss the possibilities and limitations of the use of satellite AOD products with high spatial resolution over urban areas as air quality monitoring tools. The AOD product from satellites was compared specifically to the measured ground based PM2.5 mass concentrations of aerosols in different urban areas including Mexico City and Sao Paulo. We will present the results of a study evaluating the use of the remote sensing of aerosols as a complementary tool to the ground based monitoring of aerosols in the atmosphere in urban areas.
A53H-04
Recent increases in Asian emissions and consequences for transpacific ozone pollution in the United States: INTEX-B and Aura observations
We examine ozone production in transpacific Asian pollution and its impact on surface ozone in the United States by using aircraft, satellite, and surface observations in April-May 2006 from the NASA/INTEX-B campaign. The observations are interpreted with a global three-dimensional chemical transport model (GEOS-Chem). We estimate anthropogenic NOx emissions from eastern Asia using tropospheric NO2 column observations from OMI for April-May 2006. We find a factor of two increase compared with 2000 estimates. Observations from Mount Bachelor Observatory (MBO) in the northwest United States indicate three major events of Asian transpacific pollution during INTEX-B. We study in detail one event that was also observed by the INTEX-B aircraft and by the TES and AIRS satellite instruments. The Asian plume was lifted ahead of a cold front and split into northern and southern branches over the northeast Pacific. Elevated ozone was observed in the subsiding southern branch and was consistent with production from PAN decomposition. This southern branch impacted the western United States including MBO. GEOS-Chem simulates well this transpacific event and the associated O3-CO correlations observed by TES. We find that continuous ozone formation over the Pacific from exported Asian NOx and PAN is comparable to direct transport of Asian ozone produced in the boundary layer. Model results indicate that the doubling of Asian anthropogenic NOx emissions from 2000 to 2006 increased surface ozone by 1.2-1.8 ppbv in the western United States. Rising Asian emissions, increases the possibility to detect Asian ozone plumes at mountain sites such as MBO.
A53H-05
Impact of MODIS AOD Assimilation on Regional Aerosol Predictions
Direct Broadcast real-time retrievals of Aerosol Optical Depth (AOD) from the MODIS instrument onboard the Terra satellite have been used for monitoring regional particle pollution in the US on a daily basis. AOD provides column integrated aerosol loading which is supplemental to the ground-based in-situ measurements. Monitoring atmospheric loadings of dust and smoke and their subsequent transport using MODIS AOD has been found to be particularly effective, because these aerosol species are frequently transported aloft and not observed by ground-based in-situ networks. Air quality models have become a powerful tool to diagnose and predict three- dimensional distributions of aerosol species. The model performance with dust and smoke is, however, not as good as that with sulfate aerosol. This is because dust and smoke events are episodic and it is difficult to characterize their emissions. Consequently, these aerosol constituents introduce large uncertainties in modeled aerosol distributions. Assimilation of MODIS AOD within an aerosol forecast model makes it possible not only to understand the current aerosol distribution but also to predict it with constraints from the satellite observations. This study presents an assessment of the improvement in aerosol predictions due to the incorporation of MODIS AOD in a regional aerosol forecast model. The Real-time Air Quality Modeling System (RAQMS) with a MODIS AOD assimilation is used to simulate the aerosol distributions for Aug - Oct, 2006, when dust is being transported from Sahara to the Gulf of Mexico and smoke is emitted from biomass burning over the Pacific Northwest. The model performance is evaluated using the CALIPSO observations for assessing vertical profiles and the EPA AIRNow data for assessing the surface distribution. An impact of the MODIS AOD assimilation on each aerosol species is analyzed. Further improvement of the MODIS AOD assimilation is also discussed.
A53H-06
A-Train Tropospheric Chemistry Observations on 30 August 2006 over the 2006 TexAQS/GoMACCS Study Area
During the 2006 Texas Air Quality Study (TexAQS)/Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS), AIRS and TES Science Team members provided flight planning support for NASA and NOAA aircraft, large scale context for NOAA, EPA, and State of Texas surface measurements, and contributions to post-mission modeling analyses and the Rapid Science Synthesis (RSS) Report. We present results from our ongoing integrated analysis using a number of A-Train observations to investigate tropospheric chemistry and dynamics over the 2006 TexAQS/GoMACCS study area (Texas, surrounding states, the Gulf of Mexico, and bordering countries). Focusing on one pollution event over Houston, Texas on August 30-Sept 1, AIRS and TES retrievals of tropospheric CO indicate distant biomass burning contributed to poor air quality in Houston. Closer examination of AIRS and TES tropospheric ozone retrievals reveals additional features due to surface pollution, lightning, and stratospheric intrusions. As part of the integrated analysis, AIRS" wide swath provides context for TES" higher vertical resolution retrievals of CO and O3. Integrating MODIS, OMI, MLS, CALIPSO observations and in situ measurements into our analysis yields a more complete and complementary view of tropospheric processes.
A53H-07
Validation of OMI tropospheric NO2 observations during INTEX-B and Application to Constrain NOx Emissions Over the Eastern United States and Mexico
We compare tropospheric NO2 column measurements from the Ozone Monitoring Instrument (OMI) aboard the EOS Aura satellite with coincident in situ aircraft measurements on vertical spirals over the southern United States, Mexico, and the Gulf of Mexico during the INTEX-B campaign in March 2006. Good correlation with no significant bias (r2 = 0.67, slope=0.99 ± 0.17, n = 21) is found for the ensemble of comparisons when the aircraft could spiral sufficiently low to sample most of the NO2 column. Urban spirals where large extrapolations were needed below the aircraft floor (1000 feet) showed poorer agreement. We use the OMI observations together with a global chemical transport model (GEOS-Chem) to estimate emissions of nitrogen oxides over the eastern United States and Mexico in March 2006. Comparison to EPA's National Emissions Inventory 1999 (NEI99) calls for a decrease in power plant emissions and an increase in on-road vehicle emissions relative to that inventory. These findings are consistent with independent assessments. Our OMI- derived emission estimates for Mexico are higher by a factor of 2.0 ± 0.3 than bottom-up emissions, similar to a comparison between the recently released Mexican NEI99 inventory and the bottom-up showing that the Mexican NEI99 inventory is 1.6-1.8 × higher.
A53H-08
NO2 columns in the western U.S. observed from space and simulated by a regional chemistry model and their implications in NOx emissions.
In the western U.S., there are many isolated sources of NOx emissions such as power plants, cities, and highways. Thus, errors in bottom-up NOx emissions from various sectors could be evaluated separately with satellites and atmospheric chemistry models in this part of the U.S. We carried out simulations with the Weather Research and Forecasting-Chemistry model (WRF-Chem) for the western US domain during the summer of 2005. Model NO2 columns are compared with SCIAMACHY and OMI satellite observations. The sensitivities of simulated NO2 columns to chemical mechanism and scalar-advection scheme along with the sensitivities of satellite retrievals to several assumptions are examined. Agreement between the satellite data and the model results will be summarized for each type of source.