Vertical Characterization of Aerosol over the U.S. - Aeronet, MODIS AOT

Erin Robinson, Alan PinkertJune, 2010

Activities

• Begin comparing MODIS to Aeronet standard AOT

• Comparing trends in Aeronet station patterns along similar latitudes

Varied Cursor Box Size and Statistic (GSFC)

.5 Deg x .5 deg.1 Deg x .1 deg 1 Deg x 1 deg

• Chose to vary the cursor box from .1 deg x .1 deg (resolution of MODIS) to 2 deg x 2deg

• Varied statistical aggregation for 5th percentile, 60th percentile and 95th percentile.

Results:

Seasonal Comparison – Annual

Compared the R2 value for how ‘repeatable’ the measurement wasThe slope of the scatter plot indicates how close the Modis measurement is to Aeronet standard overall

Good correlation on East and NWMODIS approxmates most sites well (yellow paddles (slope = .8-1); Overestimates in west

R2 (Blue low; Red ~1) Slope (yellow =1; Red > 1)

Seasonal Comparison – Winter

Low correlation at all sites

MODIS approxmates most sites well (yellow paddles (slope = .8-1); Overestimates in west

R2 (Blue low; Red ~1) Slope (yellow =1; Red > 1)

Seasonal Comparison – Summer

Good correlation on East and NW

MODIS approxmates most sites well; Overestimates in west

The Walker Branch site shows good correlation, but slope is underestimated – this could be a systematic error that could be fixed

R2 (Blue low; Red ~1) Slope (yellow =1; Red > 1)

Troposheric Aerosol

• Aerosol in the troposphere at a constant latitude has the same composition

• Looking at Aeronet cycle views over for sites in a similar latitude to determine if there are any consistent patters

• Patterns between multiple sites mean that the aerosol is likely in troposphere and not on the surface.

Southwest U.S.

January to April Peak