The Aqua-MODIS calibration transfer using DCC David Doelling, Conor Haney, Ben Scarino, Rajendra Bhatt, Arun Gopalan GSICS Annual Meeting, Darmstadt Germany, March 24-28, 2014

2 methods to transfer the Aqua-MODIS calibration to GEO using DCC Aqua-MODIS BRDF corrected DCC multi-year mode radiance over the GEO domain only use GEO DCC during Aqua overpass times Assume the same DCC are captured by both Aqua-MODIS and GEO, although not exactly coincident and by the same viewing conditions Rely on DCC BRDF model to remove sampling dependencies Use the month to month DCC mode radiance, to remove seasonal cycle present in both Aqua and GEO Applicable to historical instruments Aqua-MODIS/GEO DCC raymatching Similar to Aqua-MODIS/GEO all-sky ray-matching except restrict only to DCC identified regions Use coincident angle matched DCC radiance pairs

Aqua-MODIS BRDF corrected DCC mode radiance over GEO domain Use same GEO and Aqua-MODIS criteria to obtain the MODIS monthly BRDF corrected DCC mode radiance over the GEO domain

Aqua-MODIS BRDF corrected DCC mode radiance The 10-year DCC mode radiance over the GEO domain is the predicted DCC radiance GEO and MODIS must have same selection criteria Maybe the monthly mode radiance variability is correlated to the GEO variability A 0.7% difference in MODIS DCC mode radiance is observed for a 5°K temperature difference @205°K, however, the trend was identical

DCC mode radiance comparison over 140° East GEO domain GEO calibrated by ray-match with MODIS • Aqua-MODIS C6 • NPP-VIIRS Land PEATE calibration Global DCC mode radiance • Terra DCC trend half of Aqua

Possible explanations Aqua-MODIS and NPP-VIIRS monthly DCC frequency Aqua and NPP in same orbit, 45 minutes apart Aqua-MODIS C6-C5 B13 (11µm) temperature difference C6 vis C5 IR • Aqua-MODIS C5 warmer and therefor lower DCC mode radiance

DCC mode radiance comparison over 0° East GEO domain • The DCC temporal variability is somewhat similar

DCC mode radiance comparison over 140° East GEO domain • GEO and MODIS DCC frequency is some what similar

DCC mode radiance comparison with independent methods MTSAT-2 RT and DCC GOES -12 Desert and DCC 0.6% difference 0.4% difference • These results use the 10 year mode radiance

MTSAT-2/Aqua-MODIS raymatching using all 0.5° lat/lon regions SBAF based on radiance applied

Is the ray-match monthly scatter or timeline noise due to spectral differences • The DCC SBAF correction is very small • Will DCC ray-matching reduce noise? • Will there be enough samples?

DCC ray-matching Regress monthly Aqua-MODIS/GEO visible radiance pairs Identify DCC cells in Aqua 1-km pixel level data Use several cell sizes to find optimum size The mean pixel level temperature < 205°K Compute standard deviation of pixel level visible radiances and temperatures of both the core pixels and the adjacent pixels. Using GEO angle prediction software, determine if the MODIS and GEO view and azimuthal angles are within 15° Write out MODIS center latitude and longitude and time Based on MODIS time and navigation order GEO images within 15 minutes to compute similar statistics as MODIS To avoid cell overlap over an image, start with the coldest cell and remove adjacent cells within coldest cell Regress monthly Aqua-MODIS/GEO visible radiance pairs Use various thresholds and cell sizes to find lowest standard error

View angle MODIS GOES-E LEO glint Azimuth angle GEO glint IR matched regions MODIS GOES-E LEO glint Azimuth angle GEO glint VIS matched regions

Predictor Enhancements

Raymatching 302-km 92-km 1° lat/lon grid, MTSAT-2, July 20, 2011 2:32 GMT

MTSAT-2, 302-km FOV No filtering VZA<35°, s<10%

MTSAT-2, 302-km FOV Feb 2012 0.8% s 0.5831 Mar 2012 0.6% s 0.5727 Gain changes Feb s=0.8% -1.8% Mar s=0.6% +2.0% Apr s=1.2% -2.4% May s=0.9% +4.3% July 1.6% Apr 2012 1.2% s 0.5842 May 2012 0.9% s 0.5699

MTSAT-2/Aqua-MODIS April 2012 raymatched radiance pairs All-sky ocean DCC 92km DCC 302km .5772 .5847 .5842 • DCC raymatch results very similar

MTSAT-2/Aqua-MODIS monthly raymatch timelines All-sky ocean 9-km 30-km .5791 .5853 .5837 • ~1% difference in the overall absolute calibration between DCC and all-sky ocean ray-match • ~0.3% difference between various DCC ray-matching selection thresholds

Conclusions Plan is to use DCC ray-matching in the short term for current operational DCC calibration Compare with 10 year mean DCC mode radiance given to GPRCs Long term plan is to derive an annual (long-term) GEO domain specific DCC mode radiance Verify by DCC ray-matching Look at all dependencies, such temperature Look into seasonal dependencies, BRDF Learn from comparing MODIS and VIIRS domain specific DCC mode radiance