Shortwave Radiation Budgets at Surface and in the Atmosphere Derived from 5 Years of ERBE Measurements

                                     Zhanqing Li
                                  February 15, 1993
The data are here.

I. INTRODUCTION

This document describes a set of abbreviated, monthly averaged results of shortwave Surface Radiation Budget (SRB) and Atmospheric Radiation Budget (ARB), i.e. the shortwave radiative fluxes absorbed at the surface and in the atmosphere. They are derived from the Earth Radiation Budget Experiment (ERBE) data set S-4 and the European Centre for Medium-range Weather Forecasts (ECMWF) analysis archive using the algorithm proposed by Li et al (1993). There are three input parameters: reflected flux or albedo on the top of the atmosphere, vertically integrated water vapor content and the solar zenith angle. S-4 data provides monthly-mean reflected fluxes and albedo on the top of the atmosphere at 2.5X2.5 degrees of latitude/longitude. Precipitable water is obtained from ECMWF data by vertical integration of humidity analyses from the bottom to the top of the atmosphere. Solar zenith angle is calculated according to latitude and time.

The ERBE consists of 3 satellites, NOAA 9, 10 and ERBS. NOAA satellites were in sun-synchronous polar orbits, while ERBS has an orbit inclined 57 degrees relative to the equator which allows observations at different local times. ERBE has both scanning and non-scanning radiometers. Gridded product at 2.5X2.5 degrees was derived from scaner observations. ERBS scaner began observation in Nov. 1984 and failed in February 1990. NOAA 9 scanner operated from Jan 1985 to Jan 1987, while NOAA 10 from Oct 1986 to May 1989. The period covered by the S-4 product is not exactly same as the scanner operation time but a bit shorter. S-4 product contains both single data measured from one satellite and combined data from more than one satellites. The principle of data selection in the acquisition of SRB and ARB is that single data were not used unless combined data were not available.

For detailed description of S-4 data, please refer to The Regional, Zonal, and Global Averages, S-4, User's Guide, available from NASA Langley, Hampton, Virginia, USA

The procedure of deriving global SRB and ARB and discussion of the results were presented in

Li, Z., and H.G. Leighton, 1993, Global climatology of the solar radiation budgets at the surface and in the atmosphere from 5 years of ERBE data, J. Geophy. Res.- Atmosphere, 98, 4919-4930.

For detailed description of the algorithm, please refer to

Li, Z., H.G. Leighton, K. Masuda and T. Takashima, 1993, Estimation of SW flux absorbed at the surface from TOA reflected flux, J. Climate, 6, 317-330.

Preliminary validation against surface observations can be found from

Li, Z., H.G. Leighton, and R.D. Cess, 1993, Surface net solar radiation estimated from satellite measurements: Comparisons with tower observations, J. Climate (September, 1993)

II. DATA STRUCTURE

                                erbe 
                                  |                 
             glob                 |              part
               |                  |                |
      srb      |       arb        |       srb      |       arb
       |       |        |         |        |       |        |
month  | mean  | month  |  mean   | month/ | mean  | month/ | mean  
         / | \            / | \              / | \           / | \
        /  |  \          /  |  \            /  |  \         /  |  \
      clr cld for      clr cld for        clr cld for     clr cld for
  1. GLOB/PART The files under directory GLOB differ from those under PART in
    1. GLOB files cover the whole globe, i.e. 90S to 90N, while PART files cover the region from 60S to 60N.
    2. GLOB files are 4-year results (1985 - 1988), while PART files are nominally 5 years (1985-1989), except for January and July for which PART files contains 4 years of results.
    3. The results of 1989 contained in PART files are derived mainly from ERBS observations, as the NOAA scanner failed thereafter. The results in polar region (60 north or south) contained in GLOB files are based on NOAA ERBE observations only, as the ERBS satellite cannot view these areas.
  2. SRB/ARB Files under SRB are shortwave surface radiation budget data, while those under ARB are shortwave radiation budget in the atmosphere.
  3. MONTH/MEAN
    MONTH
    contains the results for individual months and years under all-sky condition.
    MEAN
    contains multi-year means of the monthly results that are obtained by averaging the results of the same months from 4 or 5 years of SRB or ARB data.
  4. CLR/CLD/FOR MEAN has three sub-directories that contain clear-sky results (CLR), all-sky results (CLD) and cloud forcing (FOR) which is defined as the difference between all-sky and clear-sky results.
    
Should you have any problem, please do not hesitate to contact Dr. Zhanqing Li Global Monitoring Section Applications Division Canada Centre for Remote Sensing 588 Booth Street Ottawa, Ontario Canada K1A 0Y7 Phone: 613-947-1311 Fax: 613-947-1406 INTERNET: LI@CCRS.EMR.CA