MODIS/Aqua Reprocessing #1 Analysis Summary

MODIS/Aqua Radiance Comparison to In Situ

The updated LUT, among other changes, has resulted in a significant improvement in consistency of the annual cycle observed in the MODIS/Aqua deep-water nLw trends. The improvement is most significant for 2004 relative to previous years. The consistency is approaching that of SeaWiFS.

Annual Repeatability of MODIS/Aqua Radiance Trends, Deep Water Subset

Annual Repeatability of SeaWiFS Radiance Trends, Deep Water Subset

Direct comparison of the deep-water trends to SeaWiFS over the common mission lifetime clearly shows improved agreement between the two sensors, especially toward end of mission. The f/Q correction significantly reduces some seasonal differences between the two sensors, thereby flattening the ratio trends. Some mid-mission bias in the comparison seems to be revealed after seasonal differences have been removed. Deep water chlorophyll was trending 30% high in operational results; trend is eliminated in reprocesing configuration; bias minimal with f/Q included. Agreement in aerosol optical thickness is much better after removing straylight-contaminated retrievals in MODIS/Aqua.

Radiance Ratios to SeaWiFS, Deep Water Subset

Chlorophyll Ratios to SeaWiFS, Deep Water Subset

AOT Ratios to SeaWiFS, Deep Water Subset

The seasonal differences between SeaWiFS and MODIS/Aqua are most pronounced in mid to high southern latitudes. The regional trends indicate that the f/Q correction significantly reduces this assymetry.

nLw Ratios to SeaWiFS, North Atlantic (AtlN) Subset

nLw Ratios to SeaWiFS, South Atlantic (AtlS) Subset

At higher southern latitudes, seasonal differences between SeaWiFS and MODIS/Aqua are still significant, and the relative improvement due to f/Q correction is not as pronounced. The cause of this high-southern-latitude disagreement may not be f/Q.

nLw Ratios to SeaWiFS, PacN50 Subset

nLw Ratios to SeaWiFS, PacN20 Subset

nLw Ratios to SeaWiFS, PacS20 Subset

nLw Ratios to SeaWiFS, PacS50 Subset

The next set of plots show global trends derived from binning three of the 4-day test periods centered on a winter and a summer solstice, with the data expressed as a function of latitude. Clear-water nLw comparison of SeaWiFS (dashed-line) with MODIS show that the proposed reprocessing configurations improve agreement between the sensors, with best agreement obtained using f/Q. The f/Q removes a substantial component of the north-south trend from the MODIS to SeaWiFS ratios, however, some systematic disagreement is still evident. Most notable is a substantial depression in the MODIS radiances relative to SeaWiFS (of order 10%) which occurs at ~40N in northern hemisphere winter and 40S in northern hemisphere summer, or about 63-deg solar zenith. This is clearly seen in the deep-water ratio trends. We are still investigating this effect.

Latitude Trends, Clear Water nLw 551 Comparison to SeaWiFS 555

Latitude Trends, Clear Water nLw Ratios to SeaWiFS

Latitude Trends, Deep Water nLw Ratios to SeaWiFS