Atmospheric Infrared Sounder (AIRS) Version 5 IR-Only Level 2 (AIRS2STC,AIRS2SPC) and Level 3 CO2 (AIRS3C2D, AIRS2C28, and AIRS3C2M) products are now available.
The AIRS CO2 post-processing retrieval algorithm now uses AIRS Level 2 Version 5 products as input. Because of an increase in noise for channel 5 of the Advanced Microwave Sounding Unit (AMSU), the yield of Level 2 data from the AIRS+AMSU algorithm declined. Therefore, production of CO2 data derived from the AIRS+AMSU algorithm was discontinued after February 29, 2012 (DOY 60).
Processing based on the new IR-Only algorithm commenced with data from January 2010. The overlap in the two product types (AIRS+AMSU and IR-Only) will facilitate comparison between the two retrieval scenarios. The AIRS Version 5 Release Tropospheric CO2 Products document (large PDF file, 13.7 MB) indicates that the IR-Only and AIRS+AMSU derived CO2 products have similar accuracy and yield over the two-year period from 2010-2011, when AMSU channel 5 was still useful. AIRS CO2 products will continue to be produced using the Version 5 IR-Only algorithm until the Version 6 CO2 product is produced.