Global Aerosol Data Set (GADS)

Global Aerosol Data Set (GADS)

What is on this page?

Global distribution of basic aerosol microphysical properties and online access to data files
Integral text of paper by Hess et al., 1998
Computations of aerosol microphysical properties in each grid point
Computations of aerosol optical properties in each grid point
Download the complete version of GADS
GADS programs online
References

    Aerosol data globally existing from different measurements and extensive models have been compiled by Hess and Koepke (Meteorolgisches Institut der Universitat Munchen, Germany), Schult (Max-Plank-Institut fur Meteorologie, Hamburg, Germany), and Shetle (Remote Sensing Division, Naval Research Lab. Washington, USA) into Global Aerosol Data Set (GADS) (Koepke et al., 1997). The copy of the GADS web page is available also here.
    The GADS is a completely revised version of the aerosol climatology by d'Almeida et al., 1991. The data now are consistent in number distribution, mass per volume and optical properties. Aerosols are modeled as 10 components which are described with size distribution and spectral refractive index (on the basis of (WMO, 1983), (d'Almeida et al., 1991)). From these data the optical properties are calculated with the Mie theory at wavelengths between 0.25 micrometers and 40 micrometers and for 8 values of relative humidity, if necessary. The properties of the aerosol components themselves are available in the software package OPAC (Optical Properties of Aerosols and Clouds). In GADS, for the entire globe, on a grid of 5 degrees longitude and latitude, with 7 differentiating height profiles, and both for summer and winter, the aerosol at the gridpoints is composed from the aerosol components.
    This data set consists of aerosol properties averaged in space and time and therefore is mainly determined for use in climate
modelling.

The following basic averaged aerosol microphysical properties at each grid point have been archived in the GADS for two seasons of the Northen Hemisphere (into the winter.dat and summer.dat files below):

Aerosol height profile (7 different profiles are used in GADS. Click here to view them.)
Total particle number density at surface in particles cm^-3
Number and list of aerosol components which compose the aerosol at a given grid point (up to 4 aerosol components are used at each grid point). The full list of possible aerosol components is given in column 2 of Table 1.
Mixing ratio of each of these aerosol components

Click with the mouse left button to view or with the mouse right button to download the following files:

winter.dat: valid for the period September to February.
summer.dat: valid for the period March to August.

The detailed description of the file contents is given in the header of each file.

The following averaged aerosol optical propertiesat each grid point, at wavelengths between 0.25 micrometers and 40 micrometers and for 8 values of relative humidity (for some components) can be computed using the GADS FORTRAN code:

Extinction coefficient [km^-1]
Scattering coefficient [km^-1]
Absorption coefficient [km^-1]
Single scattering albedo
Asymmetry parameter
Optical depth
Lidar ratio [sr]

Click here to view an example of output file with computed aerosol optical properties. File format is given in headers of each file.

All formulas and definitions are given in the basic paper by Hess et al., 1998: Click with the mouse right button and select "Save link as" item of the pop-up menu to download :

The following averaged aerosol microphysical properties at each grid point can be computed using the GADS FORTRAN code:

Aerosol microphysical property	*Example of an output file of such a type^()**
Total number density of aerosol particles in particles cm^-3or in microgram m^-3.	Click here
Number densities of aerosol components listed in column 2 of Table 1.	Click here
Aerosol types^(**), listed in column 1 of Table 6, typical for each grid point at sea level	Click here
Aerosol profile types listed in profiles.dat file, typical for each grid point.	Click here

^(*) All output files with microphysical properties have the same format: a file header, and rows with 3 values: latitude of a grid point (in degree) in column 1, longitude of a grid point (in degree) in column 2, a computed parameter (number density in particles cm^-3or in microgram m^-3, aerosol type or aerosol profile type for this grid point) in column 3.
^(**) Aerosol types are coded as integers in the GADS output files: the fist aerosol listed column 1 of Table 6 (continental clean) is refered as 1, the second one (continental average) is refered as 2, etc.

Availability and use of GADS

How to get GADS?

The complete version of the GADS as well as the detailed description of its content can be gotten:

directly from the GADS web site
from this web site: click here with the mouse right button and select the "Save link as" item of the pop-up menu. The detailed instructions on installation of the GADS are given here.The FORTRAN source of the gads.f program is given here.

GADS programs online.

GADS programs are online accessible from this page:

Global distribution of aerosol microphysical properties => Click here (NOT AVAILABLE NOW)
Global distribution of aerosol optical properties => Click here (NOT AVAILABLE NOW)