Observed OLR (Outgoing long wave radiation)


One proxy for tropical rainfall measurements is the Outgoing Long wave 
Radiation (OLR).  In NCEP-grib-speak, this would be the ULWRFtoa (upward long 
wave radiation flux at the top of the atmosphere).  Included on this CD-ROM 
are both observed OLR and that from the reanalysis data assimilation.  The 
latter is from the 6 hour forecasts starting from the four times daily 
analyses.  Since the OLR as well as the precipitation are heavily dependent on 
the physical parameterizations, their reanalysis estimates should not be 
considered robust.  Improvements in the physical parameterizations are apt to 
have major effects on both  the OLR and precipitation.

The observed OLR, on the other hand, is fairly well observed by satellites.
The observed OLR on this CD-ROM came from NESDIS by way of NCAR (references 
below).  Since we, at this time, have no method to distinguish between 
satellite observed OLR and simulated OLR in grib, we have put the observed OLR 
in it's own subdirectory. The observed OLR also has traits of real 
observations.  Some days are missing as well as grid points.  To compute the
daily averages, both AM and PM observations were required.  The local time
of the observations do drift; however, by requiring both an AM and PM pass, the 
effect of the drift is reduced.


The observed OLR on the CD-ROM is AVHRR.  ERBE is considered more reliable.



			      References

Gruber, A., 1977: Determination of the Earth-Atmosphere Radiation Budget for 
NOAA Satellite Data. NOAA Technical Report NES 76, U.S. Dept. Comm., NOAA, 
NESS, Washington D.C. 28p.

Gruber, A., P. Ardanuy, M. Weiss, S. K. Yang, S. N. Oh, 1994: Comparison
of ERBE and AVHRR longwave flux estimates.  Bulletin of the Amer. Meteor.
Soc., 75, 2115-2130.
 
Taylor, V.R., 1990: Implementation of Reflectance Models in Operational AVHRR 
Radiation Budget Processing, NOAA Technical Report NESDIS 49, U.S. Dept. 
Comm., NOAA, NESS, Washington D.C. 34p.