16
Six Year Cross Meridional Vector Transport (arrows)
and Total Scalar Transport (contours)
6051-----12911
120E
E. Raschke
Figure 1.9: Residual vectorial horizontal transport from the required zonal-mean transport
(arrows) and the scalar horizontal total energy transport (contours) for a 6 year interval (April
1979 to March 1985). Units are in 10 7 J S-I m- I (from Sohn and Smith, 1992).
results, simulated for the present climate. Wielicki et al. (1995) have summarized most recent
investigations. Raschke et al. (1973) were possibly the first estimating the effect of clouds on
the planetary albedo; they also could identify the drastic decrease of the surface albedo over
the Arctic sea ice during the summer season.
1.5.2 Radiation budget at the surface
An accurate knowledge of these components of the heat budget of the earth is necessary to
validate numerical model output for the present climate, but to estimate also the effect of
related processes, such as the evapotranspiration over continents and evaporation over oceans.
Since the networks of reliable stations of the different countries are very sparse, and do not
meet the required spatial density which could be estimated from spatial variabilities of cloud
and temperature informations (see the pioneering work by Gandin, 1963), and since no stations
at all exist over the oceans, whose temperature may react sensitively to trends in the radiation
budget components at the ocean surface, there is a need to derive such information from the
available satellite based data sets. Control of such new information is possible at least over
continental areas with data from operational networks and the international Baseline Station
Radiation Network (BSRN; Whitlock et al., 1995), which has been established within the
framework of the WCRP. Automatic stations for the downward radiation components should
be installed onboard of "ships of opportunity".
During the past years, several methods have been developed to estimate the components of
the radiation budget at ground with satellite and other ancillar data. We can scetch here their
principle only and refer the reader to the papers by Stuhlmann and Rossow in this volume.
The surface albedo and temperatures can only be estimated from "clear-sky" measurements,
with specific corrections for atmospheric effects. Over continents both depend also on the
Six Year Cross Meridional Vector Transport (arrows)
and Total Scalar Transport (contours)
6051-----12911
120E
E. Raschke
Figure 1.9: Residual vectorial horizontal transport from the required zonal-mean transport
(arrows) and the scalar horizontal total energy transport (contours) for a 6 year interval (April
1979 to March 1985). Units are in 10 7 J S-I m- I (from Sohn and Smith, 1992).
results, simulated for the present climate. Wielicki et al. (1995) have summarized most recent
investigations. Raschke et al. (1973) were possibly the first estimating the effect of clouds on
the planetary albedo; they also could identify the drastic decrease of the surface albedo over
the Arctic sea ice during the summer season.
1.5.2 Radiation budget at the surface
An accurate knowledge of these components of the heat budget of the earth is necessary to
validate numerical model output for the present climate, but to estimate also the effect of
related processes, such as the evapotranspiration over continents and evaporation over oceans.
Since the networks of reliable stations of the different countries are very sparse, and do not
meet the required spatial density which could be estimated from spatial variabilities of cloud
and temperature informations (see the pioneering work by Gandin, 1963), and since no stations
at all exist over the oceans, whose temperature may react sensitively to trends in the radiation
budget components at the ocean surface, there is a need to derive such information from the
available satellite based data sets. Control of such new information is possible at least over
continental areas with data from operational networks and the international Baseline Station
Radiation Network (BSRN; Whitlock et al., 1995), which has been established within the
framework of the WCRP. Automatic stations for the downward radiation components should
be installed onboard of "ships of opportunity".
During the past years, several methods have been developed to estimate the components of
the radiation budget at ground with satellite and other ancillar data. We can scetch here their
principle only and refer the reader to the papers by Stuhlmann and Rossow in this volume.
The surface albedo and temperatures can only be estimated from "clear-sky" measurements,
with specific corrections for atmospheric effects. Over continents both depend also on the