NUMBER 59

DATE: 07/01/88

Sector Processing Center (SPC):

During May, CSU, ESA and NOA collectively processed greater than 93% of A data into B1 and/or B2 data.

Normal operations were reported by NOA, ESA and CSU.

AES reported difficulties with their new optical disk recording system that produce inconsistent read-back of data. All of the April and part of the May B1 data are on this medium and are believed to be intact. Efforts are underway to retrieve these data for production of B2 data.

The JMA report for April indicated normal operations and successful collection of 100% of B1 data. JMA also submitted its first B2 data tape to the GPC containing the April data. No report on May data collection has been received. JMA reports discovery of a significant diurnal cycle in the calibration of the GMS IR data that is especially large during eclipse seasons. The amplitude of the variation for GMS-1 and GMS-2 data is only about 1K; however, GMS-3 shows a somewhat larger amplitude of about 2K outside eclipse season. In eclipse the amplitude of the diurnal variation has been observed to approach 9K. This problem and methods to correct the calibration are under investigation; JMA recommended suspension of B3 data production until the problem is resolved.

Special Area Processing Center (SAPC):

No reports were received.

Satellite Calibration Center (SCC):

No report was received.

Global Processing Center (GPC):

The GPC continued to receive B1 and/or B2 data and correlative data in a routine manner.

The June 1984 and a revised version of the July 1984 GMS B3 data were delivered to the ICA. The first B2 data have been received from JMA; the contents and format are being checked. So far, only a few minor errors in documentation, not the actual data tape, have been uncovered. A check of the GPC QC results for the first 19 months of GMS data indicates that the amplitude of any spurious diurnal calibration cycle for the IR data is less than 2K for GMS-1 and GMS-2 data, even during eclipse seasons. However, the amplitude of this cycle for GMS-3 during the one eclipse season we have (late 1984) is larger, about 2-3K. Production of B3 data will not be suspended, as JMA recommended, since the design of the B3 data format allows for easy changes to instrument calibration. In producing B3 data, the original count value are never altered in any case; rather all corrections to instrument calibration are applied to the appended calibration tables so that all such changes are reversible. This approach allows for further refinement of calibrations by the project or users of the data. However, the GPC will re-schedule GMS B3 production to delay its delivery somewhat and allow time to correct this problem. GMS B3 data through June 1985 were completed; delivery to the ICA will begin next week.

B3 data for GOES-6 have been produced through June 1985 and will be delivered shortly to the ICA.These geostationary satellite data sets are now being produced using the correction to the NOAA-9 visible channel calibration determined by the GPC. This correction alters the SCC normalization to remove the long-term decline in the sensitivity of the NOAA-9 AVHRR.

NOAA-9 B3 production has been completed through February 1988. A refinement of the trend correction has been calculated with the extra few months of data by checking the time evolution of the target mean reflectances. The correction coefficients are being applied to the NOAA-9 B3 data tapes; data through April 1985 have been completed so far and will be delivered to the ICA next week. All apparent anomalies in the IR calibration have been traced to the presence of a few images containing bad data or lacking calibration tables altogether; these data have been labeled as bad. However, the October 1986 "incident" is still being investigated. The processing to correct the calibration tables takes much longer than anticipated, since it requires eight tape jobs per month of data. Completion of all the NOAA-9 data through February 1988 is estimated to require about two more months. Before correction of the last six-seven months, we will first examine more data from 1988 to be sure that the current trend in the calibration continues unchanged.

New ice/snow data for 1985 and 1986 have been delivered to the ICA. The production of data for 1987 and 1988 is not anticipated until late 1989, when all of the digital sea ice data for the south pole will have been completed.

The TOVS data for 1983 and 1984 has also been delivered to the ICA. Production of data for 1985 is about half completed. The estimated production pace is about one year of data per month; thus, the backlog in this product should be eliminated by October of this year.

Production of the final versions of the July 83 and Jan 84 C1 data began in mid-June, using the revised absolute calibration for the VIS data. These first data (second versions) should be delivered to the ICA in late July. The next two data sets to be produced will be the C1 for August 1983 and April 1985. In early August, we will produce the revised BX/CX for October 1986 and the GOES BX/CX for the FIRE field experiment time periods.

ISCCP Central Archive (ICA):

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