761 ISSN 1064-2293, Eurasian Soil Science, 2007, Vol. 40, No. 7, pp. 761–765. © Pleiades Publishing, Ltd., 2007. Original Russian Text © E.Sh. Elizbarashvili, M.E. Elizbarashvili, R.V. Maglakelidze, N.G. Sulkhanishvili, Sh.E. Elizbarashvili, 2007, published in Pochvovedenie, 2007, No. 7, pp. 846–851. FORMULATION OF THE PROBLEM Investigation of soil temperature regimes is impor- tant for solving numerous theoretical and practical problems, including the assessment of crop growth conditions, hydraulic engineering and hydroameliora- tive construction, pipeline laying, and others [1, 3, 6]. The nonuniform climatic, topographic, and other natural conditions in Georgia predetermine the diver- sity of soils. Monitoring of soil temperature has been performed in Georgia since 1891; by the present time, data from 130 meteorological stations have been obtained. However, there are only a few works devoted to soil temperature regimes in Georgia [2, 4, 7]. In this paper, we discuss some aspects of soil tem- perature regimes in Georgia on the basis of soil temper- ature records collected at 60 meteorological stations in 1947–1964 and presented in the Reference Book on Cli- mate in the Soviet Union [5]. We have also used archived materials of the Hydrometeorological Depart- ment of Georgia obtained prior to 1995. RESULTS AND DISCUSSION Heat exchange in the soil–air system. Solar radi- ant energy is the main heat source for the soil. Solar energy is absorbed by the soil surface, transformed into thermal energy, and transmitted to the top, then, to the deeper soil layers. Part of the heat is radiated. Heat is transferred from the soil to the atmosphere due to the molecular thermal conductivity, turbulent exchange, heat convection, radiative thermal conductivity, and evaporation with further moisture condensation. These processes control the relationship between the soil and air temperatures and can be described by the following linear function: (1) T a kT s T ao , + = where T a is the air temperature, T s is the soil surface temperature, k is the regression coefficient, and T ao is the air temperature corresponding to zero temperature of the soil surface. Averaged values of k and T ao for all of Georgia are given in Table 1. The given equation and its parameters (Table 1) can be used for appreciation of the temperature conditions in the soil–air systems of all the soil-climatic zones of Georgia. This is confirmed by the high correlation coef- ficients and confidence limits of the regression coeffi- cients equal to ± 0.09 at a significance level of 95%. The confidence limits of the deviation of the theoret- ical linear regression line from the empirical data with due account for the maximum temperature deviation from its mean values (at a significance level of 95%) are ±0.9° for January, ±0.8° for April and October, and ±0.7° for July, which points to the statistical signifi- cance of the equation. In general, soils in Georgia are warmer than the air in periods with a positive radiation balance. In the win- ter, the soil loses heat due to radiation and cools to a greater degree than the air. These processes are differ- ently manifested under different geographic conditions (Fig. 1). For example, the temperature of well-drained light loamy alluvial and brown calcareous soils in Tbilisi is higher than the air temperature from March to SOIL PHYSICS Specific Features of Soil Temperature Regimes in Georgia E. Sh. Elizbarashvili a , M. E. Elizbarashvili a , R. V. Maglakelidze b , N. G. Sulkhanishvili a , and Sh. E. Elizbarashvili a a Institute of Hydrometeorology, Academy of Sciences of Georgia, pr. D. Agmashenebeli 150a, Tbilisi, 0112 Georgia b Geographical Faculty, Dzhavakhishvili Tbilisi State University, pr. Chavchavadze 1, Tbilisi, 0128 Georgia Received August 16, 2005 Abstract—Soil temperature regimes in Georgia are assessed on the basis of records of 60 meteorological sta- tions within the period from 1947 to 1995. Heat exchange in the soil–air system, the effect of soil types and landforms on the temperature, and regularities of the temperature distribution pattern in the topsoil are dis- cussed. DOI: 10.1134/S1064229307070083 Table 1. Values of the parameters k and T ao and correlation coefficients R Parameter Month Jan. Apr. Jul. Oct. k 0.85 0.86 1.04 1.00 T ao 0.72 –0.85 –5.70 –0.98 R 0.96 0.95 0.93 0.95