| Start Date | Start Time | End Date | End Time | Data Quality Metric |
|---|---|---|---|---|
| 09/10/1996 | 0000 | 09/30/1996 | 2359 | Suspect |
| Subject: | calibration shift during Water Vapor IOP |
| DataStreams: | sgp5mwravgB5.c1, sgpmwrlosB5.a1, sgpmwrlosB5.a0 |
| Description: | DATA QUALITY REPORT(DQR)
DQR No:
o Date Submitted: 3/19/97
o Submitted By: Jim Liljegren
Organization: PNNL
Telephone: 509-372-6136
Email: jc_liljegren@pnl.gov
o Subject of DQR: SGP/MWR.5 calibration shift during Water Vapor IOP
o Data should be labeled: acceptable
o Description:
The calibrations of all 8 ARM microwave radiometers that participated
in the Water Vapor IOP were checked prior and subsequent to the IOP.
The calibration of radiometer S/N 12, which is normally located at BF-5
(Morris, OK), was found to have changed significantly between the
beginning and end of the IOP:
TIP dates Noise Injection Temperature (K)
23.8 GHz 31.4 GHz
---------- ----------
9-13 Sep 179.89 +/- 0.37 246.44 +/- 0.28
28-30 Sep 178.81 +/- 0.25 244.53 +/- 0.24
These calibration changes result in changes of approximately 0.1 cm in
vapor and 0.1 mm in liquid.
Analysis of the time series data revealed that a step change in the
brightness temperature (and thus in the calibration) occurred after
power was restored to the instrument following an outage 14-16
September 1996.
The instrument was returned to the manufacturer for examination. They
believe that the change probably resulted from changes in the alignment
of the waveguides and other microwave components due to their thermal
expansion and contraction as the instruments cooled from their
stabilized temperature (55 degC) to ambient during the power loss
and then were heated back to the set point temperature when power was
re-applied. The manufacturer replaced several microwave components and
also replaced the aluminum plate on which the waveguides are mounted
with a brass plate in order to more closely match the expansion
characteristics of the brass waveguides.
This instrument was returned to service in January and a new
calibration implemented in February.
A positive bias still appears to exist in the LWP values. This is most
likely due to differences in elevation between Morris (217 m) and the
cebtral facility (319 m) which result in an increased average pressure
and thus an increase in the dry absorption which is not accounted for
in the present retrievals that were derived for the central facility.
I have previously submitted DQRs on this issue (negative LWP biases
appear at Vici because it is at 622 m). I plan to derive retrieval
coefficients for all of the boundary facilities once I have obtained a
new disk with sufficient storgage capacity to hold all of the
soundings.
o Suggested Corrections: none |
| Suggestions: | |
| Measurements: | sgp5mwravgB5.c1: more
sgpmwrlosB5.a1: more sgpmwrlosB5.a0: more |