رابطه دماي هوا با دماي سطح و اعماق مختلف خاك

Relationship between air temperature and surface and depth temperature

Soil temperature is one of the main physical parameters of soil. Plant growth and soil generation processes are subject to temperature changes. The study of soil temperature in different depth is of utmost importance in meteorology specially, in micro scale, in climatology, agriculture and industry. Soil temperature change is subject to weather temperature of earth surface. Relationship of soil and weather temperature is one of the most important relationships which can be applied in forecasting cold weather and estimation of damages incurred on agricultural products. Boroujen area is one of agricultural areas of chaharmahal province. This study has been in this area for decreasing the frost bite damages incurred on fannerʹs products of that area and proper information providing for them. In this study, the minimum weather temperature, minimum earth surface temperature and the temperature of different depths of earth (5-10-20-30-50 and 100 cm of earth) have been analyzed in definite standard hours, 6:30 in the morning, 12:30 of noon, and 6:30 in the afternoon after collecting the data and doing different tests(data qualification and homogeneity). Observations show that the temperature changes range in 24 hours is decreased as the earth depth is increased and that a time delay is occurred in lower depths before the temperature reaches its maximum point. The annual temperature cycle shows a time delay and a temperature changes range decrease by depth increase. The annual average temperature of earth is more than the annual average temperature of air because the energy absorbed in earth is more then the energy absorbed in air and a part of heating energy absorbed in earth is transferred to lower depths. The depth of a frost bitten layer of earth has been determined in different seasons especially in the spring and fall and finally the predication of earth minimum temperature has been offered for the prognosis of the occurrence of these phenomena. The study shows that the reason of sudden temperature decrease in the spring has mainly been radiation temperature decrease. The temperature change of earth in 50 cm. depth has been slow in such a way that the total temperature changes have been about 19.3 °C. The most temperature changes range in this area has been in 5 cm. depth and about 29.1 °C. This study has shown that the correlation of the minimum weather temperature and minimum earth temperature in all months is linear. The most correlation has been 0.98 in June and the least correlation has been 0.52 in May. The change of earth temperature has been wavy and has been decreased from surface to depth. The maximum temperature has been in 50 cm depth of earth in August with one month delay.