NUMBER 56

DATE: 04/07/88

Sector Processing Center (SPC):

During February, NOA, ESA, CSU and JMA collectively processed greater than 90% of A data into B1 and/or B2 data. AES processed 85% of A data into B1 and B2.

Normal operations were reported by NOA, ESA, JMA, AES, and CSU.

AES reported losses of data caused by a failure of the front-end collection system on 1 February and a power outage on 27 February. They now have in place a procedure to capture a "substitute" image in case of the loss of the target image; this has significantly increased their capture rate.

CSU reports that GOES -6 will be in eclipse from 27 February through 15 April; during this time the 0845 GMT image is substituted for the 0915 GMT image.

NOAA reported that the communications link between the NESDIS Satellite Operations Control Center and the Command and Data Acquisition Station at Gilmore Creek, Alaska failed on 25 February and was not restored until 29 February. This caused the loss of about 50% of A data from both NOAA-9 and NOAA-10 during this period.

Special Area Processing Center (SAPC):

No reports were received.

Satellite Calibration Center (SCC):

The following BC data have been received: (1) GOES-6 for December 84, January, February, March and December 85, January 86, and March 87, (2) GMS-3 for April 87, (3) METEOSAT-2 for September and November 86 (extra IR reports) and July and October 87. Completion of these BC eliminates the backlogs for GOES-6 and brings all satellites up to 1987.

No AC data have been received from CSU since March 87 when the GOES transmission format was changed.

At the last WGDM meeting in Colorado, a coincident change in the IR normalizations for the geostationary satellites in October 1986 was noted. Additional METEOSAT BC for September and November 86 have been obtained to refine the analysis of this problem. Initial conclusions are: (1) the September (days 7, 16, 17) normalization is consistent with the November (days 12, 28) results and different from the October (days 3, 5, 15) results, (2) the change appears primarily at cold temperatures, (3) the October data have the same quality as the data for September and November, (4) the change starts between September 17 and October 3 and ends between November 2 and November 12, (5) the change appears to be caused by a change in the NOAA-9 radiometer, since no similar occurrence has been noted in the past.

The SCC reports that the gain on the METEOSAT VIS radiometer has been changed for the first time to correct a long term decrease in sensitivity. However, the BC data, obtained by comparison to NOAA-9, have not shown such a decrease, but rather have shown a small increase. This behavior is consistent in magnitude and sign with the preliminary results that suggest that the NOAA-9 VIS radiometer sensitivity has also been declining since launch. The GPC monitor results will be compared with the aircraft calibration results obtained during the FIRE experiment to obtain a final estimate of this calibration change.

Global Processing Center (GPC):

The GPC continued to receive B1 and/or B2 data from JMA, ESA, CSU, AES and NOA and correlative data from NOAA/NESDIS in a routine manner.

New B3 tapes for GOES-6, with the corrected IR calibration for the last half of February and the first half of March 84, have been sent to the archive. New BC values have also been applied to the GOES-6 data for November 84 through January 85; these B3 data will be delivered to the ICA next week.

The GPC has not yet received the replacement navigation information for June 84 for GMS; also the calibration for the VIS channel B3 data in July 84 has not yet been corrected.

All of the NOAA-8 B3 data (from October 83 through May 84) have been shipped to the ICA. A replacement B2 data set is needed to complete the processing of the B3 for June 84.

All B3 for the first 19 months of the project are now in the archive, with the exception of two months of GMS data and one month of NOAA-8 data. These remaining data should be processed and shipped within the next month or two, once the SPCs supply the needed information or replacement data sets. QC inspection for all of these data is also complete.

NOAA-9 B3 production has been completed through November 86 and is continuing; tape problems continue to slow production and have caused the loss of some B2 data (even though it was copied). Replacement B2 tapes are needed for June and July 86. Comparison of the calibration monitor results for October/November 86 with the aircraft calibration obtained during the FIRE Cirrus Intensive Field Observations is underway. Once the calibration for NOAA-9 has been determined, delivery of B3 data beyond January 1985 can begin.

Further processing of ice and snow data for 1985 through 1987 requires obtaining the sea ice data for these later years.

Production of the ISCCP version of TOVS data has been completed for July 83 through December 84; however, the GPC has not yet received the replacement data for two months during this period. A tape format design and documentation have been completed. First delivery of these data to the ICA is delayed to await the replacement data and to conduct additional quality inspection of the data.

One of the changes made to the radiative model analysis in the cloud algorithm was to modify the calculation of water absorption in the IR to include the effects of weak absorption lines in the 10 - 11 micron wavelength region. This additional absorption makes the resulting surface temperature retrievals more sensitive to water vapor abundance variations. Examination of new results revealed a problem with spurious water vapor amounts reported in the TOVS data: excessively low values are reported over the marine stratus regions while excessively high values are associated with persistent cirrus in the ITCZ. These problems lead to very low and very high surface temperatures. Therefore, a quality control procedure has been added to the TOVS processing with four steps. (1) The difference between each daily water abundance report for each 250 km region and its corresponding monthly mean value is calculated. (2) The difference distribution for each of eight latitude zones is formed. (3) A range of values for the difference about the mode difference (which is usually at or very near zero) is determined by the values with 5% of the mode frequency. (4) Each daily value is tested to determine whether it is within this range of its corresponding monthly mean value. If a value is outside this range, it is replaced by the nearest value within the range (e.g., if a value is too high, it is reduced to the monthly mean value plus the maximum difference).

Two months (July 83 and January 84) were processed through the cloud detection part of the algortihm for all satellites. Inspection of these results revealed some small clear sky bias problems and some continuing production of fake clouds. With one further adjustment of the test parameter values and the thresholds to reduce these problem and with some corrections of minor code errors, cloud production was re-started. Both months will be processed through the detection step by the end of this week.

In addition to applying some quality checks to the TOVS data, inspection of the surface retrievals shows that using the daily values of TOVS water vapor abundances increases the variability of the resulting surface temperatures, even over the ocean. Other tests, as well as estimates of the accuracy of the TOVS water measurements reported in the literature, confirm that some of the variability in these data is measurement noise. Therefore, a three-day averaging process for water and ozone abundances has been added to the radiation analysis to reduce this noise level. Other checks of the radiation code have been completed. Processing of the data through the radiation analysis step will begin next week.

Changes in the diagnostic step that produces the C1 data are completed. The tape contents and format have been revised, as well as the READ program to incorporate new conversion tables and new parameter values. The production code for these portions of the processing are ready to begin processing next week.

Delivery of the first two months of C1 data (July 1983 and January 1984) is now expected to occur by the end of April.

ISCCP Central Archive (ICA):

The ICA continued to receive B1 data from JMA, CSU, ESA, AES and NOA in a routine manner.

The health of GMS-3, METEOSAT-2, GOES-6, GOES-7, NOAA-9 and NOAA-10 remained good. CSU reported that the NEDIS estimate is that the GOES-6 encoder lamp (the last) will most likely fail before orbit/attitude fuel shortages become critical. Past performance of the encoder lamps suggests that the remaining lamp may last until the end of 1988. NOAA decided to try truncating the images in an attempt to extend the life of the encoder lamp. This procedure was tried in February, but did not help much so full imaging has been restored. The orbital inclination will now be allowed to grow and will reach 1 degree by January 89; however, the fuel shortage will become critical in early to middle 1989. NOAA-9 experienced some intermittent power and attitude control problems in late February and early March; these did not affect data quality and have not recurred since middle March. Continuing problems with the AVHRR on NOAA-H have delayed its launch until at least 13 July 1988.

Obtaining NOAA-10 B1/B2 data over the Indian sector starting in December 1986.

Arranging for the delivery of INSAT B1 data.

Completing BC data for 1987.

Delivering all B3 data for 1985 and 1986.

Obtaining digital sea ice data for 1985 through 1987.

Beginning delivery of the final version of C1 data.

Delivery of special C data sets for the polar workshop, FIRE, the WGNE, and ERBE.