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You are here: GES DISC Home Precipitation Documentation readme_html Goddard Satellite-Retrieved Surface Radiation Budget in the Western Tropical Pacific (GSSRB)

Goddard Satellite-Retrieved Surface Radiation Budget in the Western Tropical Pacific (GSSRB)

Contents

Summary
Future Updates
Data Set Description
Data Characteristics
Data Format
Sample Software
References
Data Access
Anonymous FTP
Points of Contact

Summary

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.

Future Updates

The Goddard DAAC will update this data set as new data are processed and made available by the data producers.

Data Set Description

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.

gssrb plot

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:

· Units:

· Temporal Coverage:

· Temporal Resolution:

· Spatial Coverage:

· Spatial Resolution:

· Number of Files:

· File Size:

· File Name:

Sea surface downward shortwave & longwave fluxes, and upward longwave flux

W m-2

January 1998 to April 2000 (no data from September to December 1999)

Daily

40°S to 40°N, 90°E to 170°W

0.5° latitude x 0.5° longitude

One file per month

~12 Megabyte (Binary, uncompressed)

(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.

Sample Software

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***********************************************************************************************

References

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).

Data Access

The GSSRB data set resides on-line at the Goddard DAAC anonymous FTP site and can be accessed at
FTP.GIFftp://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

Points of Contact

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)
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Last updated: Jun 15, 2012 10:36 AM ET
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