Geographia Polonica (1998) vol. 71

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Physical principles of climate mathematical modelling

Bogumił Jakubiak

Geographia Polonica (1998) vol. 71, pp. 7-18

Abstract

Climate is a composite system consisting of five major interactive adjoint components: the atmosphere, the hydrosphere, the oceanosphere, the cryosphere, the lithosphere and the biosphere. In the paper the nature, state and variability of the climate system are described briefly. Of particular importance in open systems such as components of the climatic system is feedback. Feedback mechanisms act as internal controls of the system and result from a special adjustment among two or more subsystems. The meteorological, oceanic and glacial records show considerable variabil-ity on all time scales. Starting from chosen elements of the observed main state of the atmosphere (air temperature, atmospheric circulation, precipitation and evaporation) interannual and interdecadal variability in the climate system is briefly described. Such natural phenomena as quasibiennial oscillations (QBO) in the stratosphere, the El Niño — Southern Oscillation (ENSO) in the tropics and regional teleconnections such as the North Atlantic Oscillation are examples of such variability. The climate of the earth has undergone large changes in the past, is changing now and will change in the future. External factors (solar radiation, absorbing gases in the atmosphere, ice cover) and the thermodynamic quantities that characterize the climate (temperature, density, velocity, moisture content, salinity) are all interrelated through a set of physical laws expressed by various equations based on the general principles of conservation of mass, momen-tum and energy. The set of coupled partial differential equations can be solved subject to knowledge of the solar radiation input and other specified boundary and initial conditions that define the instantaneous state of a climate system. Mathematical models provide a new way to not only understand the climate's behaviour, but also to explore the possibility of future climate developments being predicted.

Keywords: climate, numerical climate models, climate variability

Bogumił Jakubiak, Interdisciplinary Centre for Mathematical and Computational Modelling, Warsaw University Pawińskiego 5a, 02-106 Warsaw, Poland