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Radiation Transfer Parameters for Climatology

#0023


Database on benchmark calculations of solar and long wave atmospheric radiation transfer parameters for climate studies.

Tech Area / Field

  • ENV-MRA/Modelling and Risk Assessment/Environment

Status
8 Project completed

Registration date
28.02.1993

Completion date
22.12.1996

Senior Project Manager
Nagai H

Leading Institute
Kurchatov Research Center, Russia, Moscow

Collaborators

  • University of Maryland, USA, MD, College Park

Project summary

The benchmark calculations of solar and longwave radiation transfer parameters are referred to as those in which complicated processes of absorption and scattering of the radiation at fixed atmospheric conditions are directly (i.e. practically without simplifying assumptions) taken into account. The objective of the project is to obtain the database containing a wide set of such calculation results for their subsequent utilization in improving and validating parameterized radiation codes used in climate studies, weather forecasts, etc. The development of such data-base is of modem concern since the discrepancy in results obtained by approximate radiation codes presently employed in climate models runs into tens percent. In doing so the accuracy required for many climate studies runs around one percent or better that is determined by a strong sensitivity of the climate system to radiation processes. That is why the lack of appropriate benchmarks for rigorous validation of radiation codes for numerical atmosphere models disables to attain a noticeable progress in the prediction reliability of global climate changes like green-house effects or similar ones.

Initial conditions for benchmark calculations (about a hundred of cases) have been stated as a result of activities of the expert working group established about 10 years ago by the International Radiation Commission of the International Association of Meteorology and Atmospheric Physics (IAMAP) and associated with the Inter-Comparison of Radiation Codes used in Climate Models (ICRCCM). It is the ICRCCM activity that has shown the above discrepancy in practically used radiation codes, as well as the need for their accuracy improvement has been indicated. Besides, benchmark calculation data involving radiative fluxes obtained for whole variety of considered atmospheric conditions on the basis of rigorous computation approaches have been recognized to be required for above improvement. However, up to now the benchmark data have been obtained only for some calculation cases (essentially at neglecting the radiation scattering) owing to computation problems associated with the necessity of direct (line-by-line) allowance for tens of thousands of spectral lines within absorption bands of atmospheric gases at concurrent rigorous simulation of multiple radiation scattering by aerosol and cloudy particles. Thus, the benchmark calculation of solar fluxes for only one cloudy situation has required about 100 hours of the CPU time using the CYBER-205 super-computer.

Nevertheless, the project participants have managed to develop accurate numerical techniques which computational efficiency is about two orders of magnitude as high as that of similar techniques. Therefore, relatively cheap possibility is appeared for generation of a large scope of accurate benchmark data using conventional computer workstations instead of expensive super-computers. That is why, at the ISTC support, the database which for the first time will contain accurate calculations of radiative fluxes for all 112 ICRCCM cases, may be obtained in two years. Besides it is important that presently the execution of such project in the USA or other western countries will require funds being larger by a factor of 10.

The developed database will enable to test carefully the radiation codes used in climate and weather forecast models thus noticeably improving the quality of predictions involving climate and environment global changes. This, in turn, will facilitate the adoption of measures to counteract undesirable consequences of these changes and, in particular, to propose balanced programs of the nuclear and organic fuel power production development. Besides,

- the project participants, who are experts in different applications of computational physics and were engaged earlier in studies connected with the nuclear weapons development, will redirect themselves to non-military activity;

- the accurate and highly efficient radiation algorithms developed by the project participants may be prepared for the commercial use in processing systems of the environmental remote sensing and infrared satellite sounding of the atmosphere;

- the non-military geophysical investigations, which are of importance for the solution of global ecological problems, will be supported;

- the project participants will be rendered assistance in incorporating into the international scientific community, that is also in agreement with the ISTC goals.


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