Tham khảo tài liệu 'evapotranspiration remote sensing and modeling part 16', khoa học tự nhiên, công nghệ sinh học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Possibilities of Deriving Crop Evapotranspiration from Satellite Data with the Integration with Other Sources of Information 439 canopy characteristics plant population degree of surface cover plant growth stage irrigation regime over irrigation can increase ET due to larger evaporation soil water availability planting date tillage practice etc. As it can be observed from Fig. 2 the movement of the water vapor from the soil and plant surface a t a field level is influenced mainly by wind speed and direction although other climatic factors also can play a role. Evapotranspiration increases with increasing air temperature and solar radiation. Wind speed can cause ET increasing. For high wind speed values the plant leaf stomata the small pores on the top and bottom leaf surfaces that regulate transpiration close and evapotranspiration is reduced. There are situations when wind can cause mechanical damage to plants which can decrease ET due to reduced leaf area. Hail can reduce also leaf area and evapotranspiration. Higher relative humidity decreases ET as the demand for water vapor by the atmosphere surrounding the leaf surface decreases. If relative humidity dry air has lower values the ET increases due to the low humidity which increases the vapor pressure deficit between the vegetation surface and air. On rainy days incoming solar radiation decreases relative humidity increases and air temperature usually decreases generation ET decreasing. But depending on climatic conditions actual crop water use usually increases in the days after a rain event due to increased availability of water in the soil surface and crop root zone. Fig. 2. Evaporation and transpiration and the factors that impact these processes in an irrigated crop. 2. Evapotranspiration and energy budget The estimation of ET parameter corresponding to the latent heat flux XE from remote sensing is based on the energy balance evaluation through several surface properties such as albedo surface temperature
