Computer Modeling Laboratory 6

Written report due: March 6

Passive remote sensing of atmospheric aerosols

Lectures 6 and 7


A new satellite mission is being planned to study planets X and Y. The payload will include a passive radiometer with several narrow band channels in the UV-visible. It is expected that planet X has an atmosphere consisting of a non-light absorbing gas. Planet Y's atmosphere consists of dust only. Both atmospheres are optically thin. Planets X and Y have same surface reflectivity which is low but not negligible.

  1. Design a retrieval algorithm to determine surface reflectivity and atmospheric optical depth of each planet.
  2. Based on the orbit of planet Y around the Sun, it is expected that the radiometer will cover scattering angles from 1300 to 1600. Estimate an error in retrieved dust optical depth if the retrieval algorithm will assume spherical shape of dust particles. What scattering angle would you recommend to minimize the error? Figure shows a representative scattering phase function for non-spherical dust particles and spherical particles. Assume that single scattering albedo of spherical and non-spherical dust particle is same.



In this task you will be analyzing a large wildfire episode occurred in May 2007 in the Southeast US using satellite imagery and aerosol products. This event was one of the largest wildfires in Florida, degrading air quality over the entire Southeast.

1) Analyze MODIS true color images (RGB) to identify smoke plumes, considering 22, 27 and 31 May. Briefly explain why smoke plumes cannot be identified in some instances. To find RGB images for MODIS on Terra and Aqua, go to main MODIS website Then go to Atmosphere => Images => Terra L1B Granule Images or Aqua L1B Granule Images.

2) Using Giovanni perform an analysis of MODIS and MISR aerosol products retrieved in May 2007 over the region (S300- N360; W-860 - E-800).

To display (and download) data, go to Giovanni => Atmospheric Instances=> Terra and Aqua MODIS daily products; for MISR, go to Giovanni => Atmospheric Instances=> MISR Daily.

2.1) Generate MODIS/Terra, MODIS/Aqua and MISR daily aerosol optical depth (green band, ~ 550 nm) for May 22 and 31. To do so, use option "Lat-Lon map, Time-averaged" to visualize aerosol optical depth (AOD) retrieved over the selected domain. Download image and data for analysis.

Identify major differences in AOD fields among these three instruments. Briefly discuss possible reasons.

2.2) Based on statistical analyses of ground-based PM2.5 measurements and collocated satellite-derived AOD, empirical relationships were developed to enable repeat regional characterization of Air Quality Index (AQI) (see Table showing AQI designation based on PM2.5. Source: U.S. EPA).

For May 22, compute PM2.5 fields from MODIS/Terra and MODIS/Aqua aerosol optical depth using an empirical relationship: PM2.5 (ug/m3) = 46.76*AOD+7.13. Identity regions with highest PM2.5 and corresponding AQI category.