Contents
- Summary
Future Updates
Data Set Description
- Data Characteristics
Data Format
- Sample Software
References
Data Access
- Anonymous FTP
- Points of Contact
This sea surface radiation data set is produced by
Dr. Ming-Dah Chou of NASA Goddard Space Flight Center (Code 913).
It contains the downward solar (or shortwave) flux, downward thermal
infrared (or longwave) flux, and upward longwave flux. The data set
covers the domain 40°S-40°N and 90°E-170°W in the western Pacific
and a period from January 1998 to April 2000 (no data from September
to December 1999). The spatial resolution is 0.5° x 0.5° latitude-longitude,
and the temporal resolution is one day.
The Goddard DAAC will update this data set as new data are processed
and made available by the data producers.
The surface downward shortwave flux
(S¯)
and longwave fluxes (F¯)
are computed using Japan's Geostationary Meteorological Satellite-5
(GMS-5) radiances, Special Sensor Microwave/ Imager (SSM/I) column
water vapor amount, National Centers for Environmental Prediction
(NCEP) sea surface temperature, and Chou et al.'s (1998) empirical
satellite-retrieval formulae. The upward longwave flux (F) is the sum of the emission
at the sea surface and the reflection of the downward longwave
flux,
F =
esTs4 + (1-e)F¯
where e is the surface emissivity,
s is the Stefan-Boltzmann constant,
and Ts is the sea surface temperature. A surface emissivity
of 0.97 is assumed in computing F.
Please refer to Chou et al. (1998) for a detailed description of the
satellite retrieval methodology.
By assuming a mean surface albedo of 0.05 at the solar spectrum,
the net surface radiative heating (srb) can be computed from
srb = 0.95*S¯ + F¯ - F
All fluxes are in W m-2.
The retrieved surface radiative fluxes have been validated with
radiometric measurements at the Atmospheric Radiation Measurement (ARM) site
on Manus Island (2.06°S, 147.43°E) in the equatorial Pacific starting from
January 1998 (Fig. 1). It has also been validated with measurements at the
radiation site on Dungsha Island (20.70°N, 116.72°E) during the South China Sea
Monsoon Experiment in May and June 1998.
Fig. 1. - Daily variations of the surface downward shortwave flux
(top panel) and surface downward longwave flux (bottom panel) measured at Manus
Island and retrieved from GMS-5 albedo and brightness temperature measurements.
Because of missing GMS data, neighboring points are not necessarily consecutive
days. Period of data is January 1998 to August 1999. All fluxes are in
W m
-2.
Note that the daily averaged fluxes at each grid point pertain to
the local time for the grid point rather than the UTC time. The daily average
distributions of surface radiative fluxes are often discontinuous at 180°E due
to the discontinuity of local time across the international dateline.
Data Characteristics
. Parameters:
Sea surface downward shortwave & longwave fluxes, and upward longwave flux |
· Units:
W m-2 |
· Temporal Coverage:
January 1998 to April 2000 (no data from September to December 1999) |
· Temporal Resolution:
Daily |
· Spatial Coverage:
40°S to 40°N, 90°E to 170°W |
· Spatial Resolution:
0.5° latitude x 0.5° longitude |
· Number of Files:
One file per month |
· File Size:
~12 Megabyte (Binary, uncompressed) |
· File Name:
(e.g., for Jan. 2000): 0001.daily.srad.bin |
Data Format
The daily data are stored in monthly files that are direct access binary
files. Each monthly file consists of one month of daily (24-hour) averaged
surface radiative fluxes. For each day, the fluxes are arranged in the order of
downward shortwave surface flux, downward longwave surface flux, and upward
longwave surface flux. Each radiative flux field occupies one record. Therefore,
for a month with 30 days, there are 30 x 3 or 90 records in the corresponding
data file. The missing data code is -999.9. Missing surface radiative fluxes are
often due to missing GMS-5 data or the grid point being over land.
Each directory contains monthly files of the same year. A monthly file is about 12 MB before compression. The pathnames for these files are of the format:
.../YY/YYMM.daily.srad.bin,
where YY is a two-digit year and MM is a two-digit month.
For example, '9801.daily.srad.bin' contains the daily (24-hour) average surface radiative fluxes for all the days of January 1998. This file is located in directory .../98.
The following is an example FORTRAN 77 program to read the three surface radiative fluxes for the day 15May1998.
c**********************************************************************************************
c
c Program: 'read.f'
c
c Purpose: To read the 3 surface radiative fluxes for the day 15May1998.
c
c Corresponding data file is '9805.daily.srad.bin'
c
c----------------------------------------------------------------------------------------------
c File structure of '9805.daily.srad.bin':
c Record 1: array downward shortwave surface flux swd(200,160) for 1May1998
c Record 2: array downward longwave surface flux lwd(200,160) for 1May1998
c Record 3: array upward longwave surface flux lwu(200,160) for 1May1998
c
c Record 4: array downward shortwave surface flux swd(200,160) for 2May1998
c Record 5: array downward longwave surface flux lwd(200,160) for 2May1998
c Record 6: array upward longwave surface flux lwu(200,160) for 2May1998
c .....
c .....
c .....
c Record 91: array downward shortwave surface flux swd(200,160)for 31May1998
c Record 92: array downward longwave surface flux lwd(200,160) for 31May1998
c Record 93: array upward longwave surface flux lwu(200,160) for 31May1998
c-----------------------------------------------------------------------------------------------
c The spatial resolution is 0.5 degree. The first dimension of the grid
c (index i) is longitude and the second dimension of the grid (index j)
c is latitude. i=1 is 90.25E; i=2 is 90.75E; and so on to i=200 which is
c 189.75E. j=1 is 39.75S; j=2 is 39.25S; and so on to j=160 which is 39.75N.
c
c All surface radiative fluxes are in W/m2.
c
parameter (msize=200*160)
real swd(200,160),lwd(200,160),lwu(200,160)
c
open(2,file='9805.daily.srad.bin',form='unformatted',access='direct',recl=msize)
c
c iskip= number of records to skip = 3*14 = 42
c
iskip=42
read(2,rec=iskip+1)((swd(i,j),i=1,200),j=1,160)
read(2,rec=iskip+2)((lwd(i,j),i=1,200),j=1,160)
read(2,rec=iskip+3)((lwu(i,j),i=1,200),j=1,160)
close(2)
end
c***********************************************************************************************
Chou, M.-D., W. Zhao, and S.-H. Chou, Radiation budgets and cloud radiative forcing in the Pacific warm pool during TOGA COARE, J. Geophys. Res., 103, 16967-16977, 1998.
Chou, M.-D., P.K. Chan, and M.-H. Yan, A sea surface radiation data set for climate applications in the tropical western Pacific and South China Sea, J. Geophys. Res., 2001 (in press).
The GSSRB data set resides on-line at the Goddard DAAC anonymous FTP site and can be accessed at
ftp://disc2.nascom.nasa.gov/data/TRMM/Ancillary/gssrb.
- or directly via FTP at
- ftp disc2.nascom.nasa.gov
- login: anonymous
- password: < your internet address >
- cd http://disc.sci.gsfc.nasa.gov/data/TRMM/Ancillary/gssrb
DAAC Help Desk:
- For information about or assistance in using any DAAC data, contact
the DAAC Help Desk at:
- EOS Distributed Active Archive Center (DAAC)
- Code 610.2
- NASA Goddard Space Flight Center
- Greenbelt, Maryland 20771
- Email:daacuso@daac.gsfc.nasa.gov
- 301-614-5224 (voice)
- 301-614-5268 (fax)
Data Producers:
- The Principal Investigator for the Surface Radiation project is:
Dr. Ming-Dah Chou
- NASA Goddard Space Flight Center
- Code 913
- Greenbelt, Maryland 20771
- Email:chou@climate.gsfc.nasa.gov
- 301-614-6192 (voice)
- 301-614-6307 (fax)
- The producer of the GSSRB product is:
Dr. Pui King Chan
- Code 913
- NASA Goddard Space Flight Center / SSAI
- Greenbelt, Maryland 20771
- Email:chan@climate.gsfc.nasa.gov
- 301-614-6407 (voice)
Atmos Composition
