Grantee Research Project Results
1999 Progress Report: Development of Techniques for Assimilating GOES Satellite Data into Regional-Scale Photochemical Models
EPA Grant Number: R826770Title: Development of Techniques for Assimilating GOES Satellite Data into Regional-Scale Photochemical Models
Investigators: McNider, R. T. , Song, Aaron , Norris, W. B.
Current Investigators: McNider, R. T. , Norris, W. B. , Biazar, Arastoo
Institution: The University of Alabama in Huntsville
EPA Project Officer: Hahn, Intaek
Project Period: July 1, 1998 through June 30, 2001 (Extended to January 17, 2004)
Project Period Covered by this Report: July 1, 1998 through June 30, 1999
Project Amount: $404,127
RFA: Air Pollution Chemistry and Physics (1998) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air , Safer Chemicals
Objective:
The specification of clouds and moisture in regional photochemical models is highly uncertain because of a lack of direct measures of these quantities on fine scales and because model estimates of these properties are poor. However, these properties are critically important to the fidelity of regional photochemical models' simulations of ozone and aerosols. Clouds dominate the available actinic flux into the boundary layer and largely govern the spatial variation in surface temperatures. Soil moisture also has a major impact on surface temperatures because it controls the partitioning of sensible and latent heat fluxes. Surface temperatures, in turn, affect the variations in biogenic emission rates and mixing heights. Under this activity, we are employing satellite data to reduce the uncertainty in the cloud and soil moisture information that meteorological models pass to the photochemical models.
Progress Summary:
During the first year of this project, we have implemented our satellite insolation assimilation scheme and satellite derived moisture availability scheme into the MM5 framework. The MM5 is probably the most popular mesoscale model for driving photochemical models and is the base model within the Environmental Protection Agency's MODELS3 System. These schemes were originally developed and tested in the RAMS framework; however, the transition to MM5 went well.
The first test of the new MM5 satellite assimilation system was for a period during the 1999 Nashville Intensive. A two-level nest was used with a coarse CONUS grid at 36 km and a finer resolution 12 km grid over the Southeast was employed. The model was initialized on July 15 using the standard analysis (rawinsonde and surface data), and run for 5 days. Four-dimensional data assimilation was invoked for the period nudging to the analysis file. Two cases were run-a control case without satellite assimilation and a second case with GOES skin temperature tendency assimilation (McNider, et al., 1994, Mon. Wea. Rev.) GOES derived insolation values (McNider, et al., 1995, Int. J. Remote Sensing and Gautier, et al., 1980, J. Atmos. Sci.). The model performance was compared to special observations made during the Nashville Intensive. Specifically, model air and land surface temperatures, latent heat fluxes, sensible heat fluxes, and net radiation were compared to special flux sites operated during the intensive. Figure 1 shows an example of the improvement in net radiation with the satellite assimilation compared to the control case. In general, the case with satellite assimilation was significantly better, i.e, net radiation was better, temperatures were better, and latent heat fluxes were better. It turns out that sensible heat fluxes were slightly degraded and we are looking into the possible causes for this.
Because we also had a radar composite data set in place in our group, we have
begun to use this data set to improve specification of temperature by including
the effects of evaporative cooling. The spatial results from the model are much
more realistic with the satellite assimilation. Figure 2 shows a four panel
depiction of the model results with and without satellite and radar
assimilation. Comparison of model results versus National Weather Service (NWS)
observations show considerable improvement in the temperature field with the
assimilation.
Future Activities:
We will continue our comparison of model output with and without satellite assimilation. We expect to first extend our model run beyond 5 days to include an eventual 30 day simulation. This will allow us to have a robust statistical comparison to NWS data as well as the special observations under both the Nashville and Atlanta Intensives in 1999. We are going to concentrate for the present on the 1999 period as opposed to the 1995 Nashville Intensive because of the flux sites available in 1999, and because the satellite data sets are more complete. One problem that we have encountered, which also has been encountered by other investigators, is that the night-time net radiation in the model appears to have some problems so that realistic surface inversions are not supported. We are continuing to work on this problem ourselves and in conjunction with other MM5 groups.
Journal Articles:
No journal articles submitted with this report: View all 4 publications for this projectSupplemental Keywords:
ambient air, precipitation, southeast, oxidants, RFA, Air, Scientific Discipline, Engineering, particulate matter, Ecology, Environmental Chemistry, Engineering, Chemistry, & Physics, Environmental Engineering, Environmental Monitoring, biogenic emissions, meterology, latent heat flux, soil, photolysis wavelength, remote sensing, GOES satellite, photochemical processes, regional scale, cloud condensation, air quality standards, air modeling, actinic flux, boundary layer, PM2.5Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.