NUMBER 79

DATE: 03/02/90

Sector Processing Center (SPC):

During January, NOAA, AES and JMA processed greater than 97% of A data into B1/B2 data. December B2 data were received from ESA.

Normal operations were reported by NOAA, AES and JMA.

AES data collection is back to normal using their own bit synchronizer; only minor losses of data occurred.

ESA reported decontamination of sensors caused loss of data from 0900 UTC on 6 December through 0900 UTC on 8 December.

CSU reported that INSAT B2 data with eight-times daily frequency have now been delivered to NCAR covering the period from April 88 through April 89. CSU plans to process all INSAT data, starting with 1986, when only twice daily coverage is available. A test B2 data tape and documentation have been sent to the GPC for evaluation. A preliminary radiance normalization procedure has also been developed that uses overlapping observations (nearly simultaneous and co-located with similar satellite zenith angles) from METEOSAT and GMS B3 data (the normalized calibration). Quality inspection procedures have been developed to detect occasional errors in date/time labels and navigation off-sets. Once the B2 format design is finished and the radiance normalization tested, operational production of INSAT B2 can begin.

Special Area Processing Center (SAPC):

No reports were received.

Satellite Calibration Center (SCC):

New BC data were received for GOES-7 for January 89 with partial results for February 89; the changed IR count translation table (associated with the change to the AAA format telemetry by NOAA), implemented by AES in January 89, will require a change in the SCC processing, however.

Global Processing Center (GPC):

The GPC continued to receive B2 data and correlative data in a routine manner.

Final examination of available statistics for NOAA-9 Channel 4 (IR) calibration reveals several other isolated incidents of apparent gain changes, similar to the one discovered by the SCC in October 86; however, these cases are not sufficiently "unusual" to justify corrections in that the only effect on the data is a warming of a few kelvins at temperatures of 230-240K with little change at higher temperatures. Closer inspection of the IR calibrations of the images used by the SCC to measure this change shows that some of these images are slightly abnormal as well and had to be corrected. Consequently, no change was been made in the Channel 4 calibration on NOAA-9 for these earlier events. However, the change found by the SCC in October 87 is different in character in two ways: (1) not only are the coldest temperatures affected, but the global mean temperatures are shifted by a noticeable amount and (2) the change persists for about a year rather than for a few weeks as in all the other cases. Thus, the calibration of Channel 4 will be altered to eliminate this sudden change in the long-term statistics (the first detected in four years of data): NOAA-9 brightness temperatures for the period Oct 87 - Oct 88 will be muliplied by a factor of 1.028 and an offset of -8.5K applied.

Production of NOAA-11 B3 data is current. Continued study of the NOAA-11 Channel 1 calibration shows that the degradation of this radiometer over its first year is about twice as rapid as for NOAA-9. Delivery of these data will be delayed until the NASA calibration flight data are obtained for comparison and verification. A preliminary comparison of NOAA-9 and NOAA-11 statistics for Channel 4 shows an average difference of 2.5K in the overlappin period in October-November 88. This is the first significant difference in IR calibration discovered for AVHRR; however, the effect of the NOAA-9 calibration change has not yet been included.

Production of NOAA-10 preliminary B3 data has been completed through December 88. Using a longer data record reveals a slow drift of the NOAA-10 VIS calibration relative to that of NOAA-9 (corrected for its drift). Two anomalous months (May and July 87) of data were discovered, however, which are still being investigated. A first glance, they appear to be data from different months than indicated.

All B3 data for GOES-6 have been produced through Jan 89 and BC data are complete through October 88; final calibration of these data is underway.

Production of B3 data for GMS has been completed through October 89, skipping those six months for which replacement B2 data are needed. BC data are complete through April 88.

Production of B3 data for METEOSAT is complete through November 88; however, in December the data appear to be a mixture of MET-3 and MET-4 data. This problem is under investigation. Replacement B2 data have also been received for January through April 89; replacement B2 for May - September 89 are still needed. BC data are complete through May 89.

The combined ice/snow correlative data set for 88 has been produced and delivered to the ICA.

C1 data for August and September 85 have been completed. Production of C1 data for October and November 85 is underway.

ISCCP Central Archive (ICA):

The ICA continued to receive B1 data from NOA, AES, ESA, and JMA and B3 and C data from the GPC in a routine manner.