DQR ID | Subject | Data Streams Affected |
---|---|---|
D030312.9 | TWP/MWR/C1 - Intermittent Negative Sky Brightness Temperatures | twpmwrlosC1.a1, twpmwrlosC1.b1 |
D030822.9 | TWP/MWR/C1 - min/max/delta values incorrect | twpmwrlosC1.b1 |
D040220.1 | TWP/MWR/C1 - wrong azimuth | twpmwrlosC1.a1, twpmwrlosC1.b1 |
D050725.9 | TWP/MWR/C1 - Reprocess: Revised Retrieval Coefficients | twpmwrlosC1.a1, twpmwrlosC1.b1, twpmwrtipC1.a1, twp5mwravgC1.c1 |
Start Date | Start Time | End Date | End Time |
---|---|---|---|
01/04/2002 | 2200 | 10/31/2002 | 2220 |
Subject: | TWP/MWR/C1 - Intermittent Negative Sky Brightness Temperatures |
DataStreams: | twpmwrlosC1.a1, twpmwrlosC1.b1 |
Description: | Several related and recurring problems with the MWRs have been reported dating back to 1999. These problems were due to the occurrence of blackbody signals (in counts) that were half of those expected. The symptoms included noisy data, spikes in the data, negative brightness temperatures, and apparent loss of serial communication between the computer and the radiometer, which results in a self-termination of the MWR program. Because these all initially appeared to be hardware-related problems, the instrument mentor and SGP site operations personnel (1) repeatedly cleaned and replaced the fiber optic comm. components, (2) swapped radiometers, (3) sent radiometers back to Radiometrics for evaluation (which did not revealed any instrument problems), and (4) reconfigured the computer's operating system. Despite several attempts to isolate and correct it, the problem persisted. It became apparent that some component of the Windows98 configuration conflicted with the DOS-based MWR program or affected the serial port or the contents of the serial port buffer. This problem was finally corrected by upgrading the MWR software with a new Windows-compatible program. |
Measurements: | twpmwrlosC1.b1:
twpmwrlosC1.a1:
|
Start Date | Start Time | End Date | End Time |
---|---|---|---|
10/11/1996 | 0000 | 02/09/2003 | 2359 |
Subject: | TWP/MWR/C1 - min/max/delta values incorrect |
DataStreams: | twpmwrlosC1.b1 |
Description: | The values of valid_min, valid_max, and valid_delta for fields tkxc and tknd were incorrect. They should be 303, 333, and 0.5 K, respectively |
Measurements: | twpmwrlosC1.b1:
|
Start Date | Start Time | End Date | End Time |
---|---|---|---|
10/11/1996 | 0000 | 02/18/2004 | 2250 |
Subject: | TWP/MWR/C1 - wrong azimuth |
DataStreams: | twpmwrlosC1.a1, twpmwrlosC1.b1 |
Description: | The MWR was initially installed at an azimuth angle defined as 180 degrees but the value in the configuration file was not changed from the default of 0 degrees. In examining photos taken during the installation of the AWS tower, I noticed that the MWR was rotated opposite the normal orientation. The value in the configuration file was changed to reflect the actual azimuth of the instrument. |
Measurements: | twpmwrlosC1.b1:
twpmwrlosC1.a1:
|
Start Date | Start Time | End Date | End Time |
---|---|---|---|
05/04/2002 | 0200 | 06/30/2005 | 2100 |
Subject: | TWP/MWR/C1 - Reprocess: Revised Retrieval Coefficients |
DataStreams: | twpmwrlosC1.a1, twpmwrlosC1.b1, twpmwrtipC1.a1, twp5mwravgC1.c1 |
Description: | IN THE BEGINNING (June 1992), the retrieval coefficients used to derive the precipitable water vapor (PWV) and liquid water path (LWP) from the MWR brightness temperatures were based on the Liebe and Layton (1987) water vapor and oxygen absorption model and the Grant (1957) liquid water absorption model. Following the SHEBA experience, revised retrievals based on the more recent Rosenkranz (1998) water vapor and oxygen absorption models and the Liebe (1991) liquid waer absorption model were developed. The Rosenkranz water vapor absorption model resulted a 2 percent increase in PWV relative to the earlier Liebe and Layton model. The Liebe liquid water absorption model decreased the LWP by 10% relative to the Grant model. However, the increased oxygen absorption caused a 0.02-0.03 mm (20-30 g/m2) reduction in LWP, which was particularly significant for low LWP conditions (i.e. thin clouds encountered at SHEBA). Recently, it has been shown (Liljegren, Boukabara, Cady-Pereira, and Clough, TGARS v. 43, pp 1102-1108, 2005) that the half-width of the 22 GHz water vapor line from the HITRAN compilation, which is 5 percent smaller than the Liebe and Dillon (1969) half-width used in Rosenkranz (1998), provided a better fit to the microwave brightness temperature measurements at 5 frequencies in the range 22-30 GHz, and yielded more accurate retrievals. Accordingly, revised MWR retrieval coefficients have been developed using MONORTM, which utilizes the HITRAN compilation for its spectroscopic parameters. These new retrievals provide 3 percent less PWV and 2.6 percent greater LWP than the previous retrievals based on Rosenkranz (1998). Although the MWR data will be reprocessed to apply the new monortm-based retrievals, for most purposes it will be sufficient to correct the data using the following factors: PWV_MONORTM = 0.9695 * PWV_ROSENKRANZ LWP_MONORTM = 1.026 * LWP_ROSENKRANZ The Rosenkranz-based retrieval coefficients became active at TWP.C1 20020504.0200. The MONORTM-based retrieval coefficients became active at TWP.C1 20050630.2100. Note: a reprocessing effort is already underway to apply the Rosenkranz-based retrieval coefficients to all MWR prior to April 2002. An additional reprocessing task will be undertaken to apply the MONORTM retrieval to all MWR data when the first is completed. Read reprocessing comments in the netcdf file header carefully to ensure you are aware which retrieval is in play. |
Measurements: | twpmwrlosC1.b1:
twp5mwravgC1.c1:
twpmwrlosC1.a1:
twpmwrtipC1.a1:
|