Investigation of Advection Occurrence in the Spring and Fall Crops Growing Season in Karkaj region, Tabriz

Due to advection phenomenon, energy balance in vegetation covered field's changes and some additional energy is transferred from the barren lands to vegetation covered sites by air sensible heat flux. This phenomenon increases the evapotranspiration. The present study was conducted to investigate the advection occurrence in the field of maize as a spring crop, and winter wheat as a fall crop at the Agriculture Faculty Research Station of Tabriz University. Mentioned crops for were planted in a 1.6 hectares’ farm, equipped with a lysimeter at its middle, for two years. These crop's evapotranspiration was measured by the lysimeter during the growing season of each plant. The advection phenomenon occurrence was investigated using the methods of energy balance in the field surface, Priestly-Taylor coefficient, the ratio of evapotranspiration obtained from advection energy to vegetation surface evapotranspiration (Rad) and Bowen's ratio () on different days after planting of each crop. Observation data of the temperature showed that there was a sensible heat gradient between the lysimeter and surrounding areas. Negative values of the sensible heat flux, Rad and Bowen ratio on some days of plants growing season showed that the advection extra energy had affected the crops evapotranspiration values. Results showed that the advection effect on maize evapotranspiration was more than that on wheat evapotranspiration. In the study region except of regional advection, local advection could be occurred due to small size of cropped fields, different irrigation schedule and depth of adjacent farms, and fallow duration of some farms.