NUMBER 80

DATE: 04/05/90

Sector Processing Center (SPC):

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

Normal operations were reported by NOAA, ESA, JMA and AES.

AES reported that B1 shipments to the ICA have been delayed by new security procedures that restrict access to the data.

ESA reported that decontamination of MET-4 sensors caused loss of data from 0900 UTC on 2 January through 1500 UTC on 4 January. Anomalous behavior by MET-4 was observed in late January and is being investigated. MET-3 replaced MET-4 as the operational satellite at 0900 UTC on 24 January and continued through February.

Special Area Processing Center (SAPC):

No reports were received.

Satellite Calibration Center (SCC):

New BC data were received for GOES-6 for November 88 and January 89, completing all BC for this satellite which ended operations at the end of January 89. Also, new BC data were received for GMS-3 for July and October 88. Additional results for GOES-7 for January and February 89, using both IR translation tables, were provided to the GPC to assist in understanding the relation between data calibrations obtained using these two different translations. The SCC reports working on GMS-3 BC data for the latter part of 88 when NOAA-11 was used as the reference and on changing the IR translation table for GOES-7 data.

Global Processing Center (GPC):

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

Re-calibration of the IR radiances from NOAA-9 for the period Oct 87 through Oct 88 is underway; data for Oct 87 through Feb 88 are completed. A further refinement of the statistics led to a change of the correction factor from 1.028 with an offset of -8.5 K to a factor of 1.038 with an offset of -11.5 K. This change does not affect warmer temperatures, but further reduces the colder values. Moreover, the same correction was applied to NOAA-9 B3 data for March 87, while a correction of 1.028 with an offset of -8.5 K was applied to the Oct 86 B3 data.

Production of NOAA-11 B3 data is current. Continued study of the NOAA-11 Channel 1 calibration now shows that the behavior over the first 14 months is not a steady decline, as exhibited in the earlier part of the time record. Instead we observe an initial decline for about 10 months and then a recovery for the next four months. In a workshop on 27-28 March 1990, sponsored by NOAA, there was some discussion that the significantly earlier orbit of NOAA-11 (launched into an orbit with a 13:20 equator crossing time) may be causing some problems with direct sunlight in the imaging cavity. This is only a rumor at this point, but other calibration monitoring results show the same qualitative behavior as we have found. We have just obtained ER-2 calibration flight results for NOAA-9 and NOAA-11 for November 88 (with which we will check and refine our trend correction for NOAA-9) and for NOAA-11 for April and July 89 with which we can check our trend monitoring. Results from a ER-2 flight this spring should be available by summer, so that we may be able to determine what the NOAA-11 AVHRR is doing. Delivery of these data will be delayed until the NASA calibration flight data are obtained for comparison and verification.

Production of NOAA-10 preliminary B3 data has been completed through September 89, which completes all of the NOAA-10 data that are available. NOAA has no funds remaining this fiscal year for processing of NOAA-10 B2 data; no more data will be delivered until next fiscal year, which starts on 1 October 90. The two anomalous months (May and July 87) of data were, in fact, from the wrong months due to a data set naming error. The complete data record from December 86 through September 89 will be used to correct the drift of the NOAA-10 Channel 1 calibration. Re-calibration and delivery of NOAA-10 B3 should begin this month.

The last BC data for GOES-6 have been received from the SCC; final calibration of the remainder of these data is underway.

Production of B3 data for GMS-3 has been completed through November 89, skipping those six months for which replacement B2 data are needed. Production of B3 for GMS-4 (from December 89) cannot begin until nominal calibration and spectral response information are obtained. BC data are complete through October 88.

Production of B3 data for METEOSAT is complete through April 89. Replacement B2 data for May and June 89 have been shipped by ESA; only July through September 89 B2 data still need to be replaced. Production of MET-4 preliminary B3 has resumed with October 89 data. BC data are complete through May 89.

Several researchers have requested that the daily frequency of TOVS observations reported in C1 data be increased, if possible; moreover, some people have claimed that the regular TOVS product which we receive has daily observation frequencies of at least twice daily, if not almost four times daily when two polar orbiters are operational. We have completed a survey of all of our TOVS data, from mid-83 through mid-89 to check this possibility. Three factors control the available sampling frequency: the number of observations that are complete, the number of polar orbiters operating, and the overlap of sequential orbits. Since we require both temperature and humidity information for our analysis, we use only those observations that report both. Typically, this means that we discard anywhere from 40 - 60% of the results provided. Using the results that do not report humidities and retaining constant humidity values over one day did not seem to be any better than retaining one temperature-humidity set over the day. Over the first six years of ISCCP from July 83 through July 89, TOVS has been produced from a single polar orbiter for about 2.5 years. Whenever the TOVS results are based on a single polar orbiter, the global average daily sampling frequency falls significantly below one: in July 84, the global average daily sampling frequency was < 0.6. Finally, a small difference in the global average frequency is produced by how one maps the data; the TOVS product is collected in an effective 2.5 grid, which means many more observations are reported at high latitudes than are actually needed. In summary, the average daily sampling frequency over the whole TOVS data set (including only observations reporting both temperature and humidity) is just about one and is never higher than about 1.25, so no change in the ISCCP C1 data will be made.

C1 data for October and November 85 have been completed. Production of C1 data for December 85 and January 86 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.