validation of shaw model in determination of maximum soil frost penetration depth in typical arid and semi-arid zones of iran

simultaneous heat and water model (shaw) is based on the assimilation rate of melting and/or freezing of the accumulated snow as well as melting of ice in soil. the main objective of this study was to evaluate applicability of shaw model in determining maximum depth of frost penetration in soils in some typical climates of iran. to this end, the daily data of air temperature, soil temperatures at different depths, duration of bright sunshine, and air humidity were collected for the period of 1992-2003 for four meteorological stations of iran including shahr-e- kord, urumia, sanandaj, and yazd. then, the maximum soil frost penetration depth (sfpd) for each year in the above mentioned stations was determined based on both the measured temperatures at different layers of soil and the calculated values using shaw model. results of the analyses indicated that there was a significant linear relationship between the observed and the calculated values of maximum sfpd. the obtained coefficients of linear correlation between the observed and the calculated values for meteorological stations of shahr-e-kord, urumia, sanandaj and yazd were 0.90, 0.77, 0.84 and 0.94, respectively, all being significant at one percent level. according to the results, it was concluded that, with the yearly records of weather parameters and soil conditions, a reliable estimate of the maximum annual depth of soil frost penetration can be made in similar regions of iran by application of shaw model.