Section 9.4

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9.4 Sounding Products (ATOVS and AMSU-B)

Beginning with the NOAA-15 satellite, the sounding instrument suite was dramatically changed. The four-channel MSU instrument was replaced with a 20-channel AMSU instrument suite, AMSU-A for temperature and AMSU-B for moisture. The SSU instrument was dropped but AMSU-A essentially replaces it's function. The HIRS, AMSU-A and AMSU-B instruments are described in Sections 3.2, 3.3 and 3.4, respectively. The ATOVS system is the 'TOVS' system for NOAA-15 and subsequent satellites. ATOVS uses the HIRS and AMSU-A to generate the retrieved profiles. The AVHRR instrument is used for cloud detection along with the HIRS and AMSU-A. The AMSU-B instrument is currently not part of the ATOVS system, primarily because of resource limitations in the development of the system. Therefore, the AMSU-B is processed independently of ATOVS using a slightly modified version of software developed and used to process the SSM/T-2 on the DMSP satellites. The AMSU-B system became operational about one year after ATOVS because of satellite antenna interference in the AMSU-B data. NESDIS has expended a great deal of effort to reduce the interference and accurately account for the constant interference which remains. Refer to Appendix M for more details about the AMSU-B Bias Correction Algorithm.

NESDIS currently has the capability of producing a maximum of 370,000 soundings every 24 hours from two operational spacecraft. ATOVS from NOAA-15 generates about 300,000 retrievals every 24 hours with a 60 km resolution (40 km at nadir). AMSU-B from NOAA-15 generates about 1,400,000 moisture retrievals every 24 hours with a 15 km resolution and 15 km spacing between retrievals; the data are sampled to reduce the data volume by half. Section 9.4.1 describes the ATOVS format, while Section 9.4.2 describes the AMSU-B format.

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