FILENAME:      shbmwrlosorr.readme.txt

DATASET TITLE:      SHEBA: ETL Reprocessed Microwave Radiometer Retrievals
                                   Version # 2 retrievals, released on 11/30/01.
               Version #1 is available from the ARM Program.
CONTACTS:                Brad Orr, brad.w.orr@noaa.gov, 303-497-5152
               Matthew Shupe, matthew.shupe@noaa.gov, 303-497-6471.
               Taneil Uttal, taneil.uttal@noaa.gov, 303-497-6409

SUMMARY: Microwave radiometer data files provide retrievals of precipitable water vapor
(PWV) and condensed liquid water path (LWP).  These files are identical to the initial files
available from the Atmospheric Radiation Measurement (ARM) Program with the vapor and
liquid fields replaced with reprocessed data.

TIME PERIOD: 12/5/97 - 9/9/98

INSTRUMENT: 
23.8 and 31.4 GHz Microwave Radiometer (MWR) -   Radiometrics WVR-1100.  References for
the instrument, calibration, and initial retrievals can be found on the DOE/ Atmospheric
Radiation Measurement (ARM) Program's web site at:
http://www.arm.gov/docs/instruments/static/mwr.html.

TECHNIQUES: Microwave radiometer measured brightness temperatures are used in Arctic-
specific retrievals that incorporate information on the dielectric constants of super-cooled liquid
water and the absorption of dry air according to the methods described by Westwater et al.
(2001).  The reprocessing was performed using a statistical method based on climatological
soundings from Barrow, Alaska.  Preliminary comparisons indicate that LWP values may be
somewhat higher than those obtained with in situ aircraft measurements by about 15%.  This
discrepancy is not completely resolved at the time of this data version release.  Original
microwave data were obtained from the U.S. Department of Energy Atmospheric Radiation
Measurement Program.

SAMPLING RESOLUTION: Observations of brightness temperatures and retrievals of LWP and
PWV are given on approximately 2-minute intervals.
               
FILE FORMAT: NetCDF.

PARAMETERS (units, uncertainties):
Note: Information on all parameters is included in the NetCDF header information for each file. 
These files are identical to the original ARM files with only the "vap" and "liq" fields being
replaced.  Retrieval coefficients in the global attributes were also updated.  Useful fields include:
base_time - Seconds since 1-1-1970, 00:00:00.
time_offset - Seconds since base_time.
tbsky23 - Sky brightness temperature at 23.8 GHz in Kelvins.  0.3 K rms error.
tbsky31 - Sky brightness temperature at 31.4 GHz in Kelvins.  0.3 K rms error.
vap - Retrieved column precipitable water vapor in cm. <0.05 cm error.
liq - Retrieved column liquid water path in cm.  0.003 cm rms error.
wet_window - Designation if instrument window is wet or not. If so measurements are in error.

KNOWN ERRORS:  The MWR data set prior to 5 December 1997 suffered from irrecoverable
calibration problems and is therefore not included here.  

REFERENCES:
Westwater,E.R., Y. Han, M. D. Shupe, S. Y. Matrosov, 2001: Analysis of integrated cloud liquid
and precipitable water vapor retrievals from microwave radiometers during SHEBA, J.  Geophys. 
Res., 106, 32,019-32,030.