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Use of tho Stochastic Method to Study Climatic Changes in the South of Iran

Authors:
[ Raeisi ] -
[ L. Jokar ] -
[ N, Samani ] -
[ A. Soltani ] -

Abstract:

The concentration of atmospheric CO, and other gases has risen since the industrial revolution. Carbon dioxide has increased in concentration by about 35% since 1958 (Keeling, 1988). Bultot and others (1988) studied the effect of doubling the carbon dioxide concentration on hydrological parameters such as potential evapotranspiration, soil moisture, snow accumulation, groundwater storage, run-off and water budget in three watersheds in Belgium. The study showed that the potential evapotranspiration, soil moisture and groundwater storage has increased in high permeability watersheds. Mitchell (1989) showed that doubling C02 increases the air temperature from 1.8 K to 5.2 K and the precipitation from 7.1% to 15%. These changes are not uniformly distributed in space. The zonally averaged warning is generally most pronounced in high latitudes. bte (1989) used the time series of 70 years of discharge data to evaluate climatic changes. The results were not consistent. Hydrological changes were observed in some of the rivers and lakes, while in others no specific trend was observed. The carbon dioxide concentrations have not been measured in the south of Iran. Therefore hydrological data such as temperature, precipitation, and discharge could be used to study the climatic change. If the statistical parameters such as mean, and variance change in subsequent periods, then it could be concluded that the climate has changed. The spectral analysis is carried out for 40 years of precipitation data of Shiraz. The periodic and trend components were determined and the stochastic models were fitted to the random components. The analysis confirms that there is no significant trend during the 40 years period of precipitation. Therefore no time series components are found which would be compatible with a climatic change induced by the greenhouse effect.

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