Determination of surface energy balance depends on the energy exchange between land and atmosphere. Thus, crop, soil and meteorological factors are crucial, particularly in agricultural fields. Evapotranspiration is derived from latent heat component of surface energy balance and is a key factor to clarify the energy transfer mechanism. Development of the methods and technologies for the aim of determining and measuring of evapotranspiration have been one of the main focus points for researchers. However, the direct measurement systems are not common because of economic reasons. This situation causes that different methods are used to estimate evapotranspiration, particularly in locations where no measurements are made. Thus, in this study, non-linear techniques were applied to make accurate estimations of evapotranspiration over the winter wheat canopy located in the field of Atatürk Soil Water and Agricultural Meteorology Research Institute Directorate, Kırklareli, Turkey. This is the first attempt in the literature which consist of the comparison of different machine learning methods in the evapotranspiration values obtained by the Bowen Ratio Energy Balance system. In order to accomplish this aim, support-vector machine, Adaptive neuro fuzzy inference system and Artificial neural network models have been evaluated for different input combinations. The results revealed that even with only global solar radiation data taken as an input, a high prediction accuracy can be achieved. These results are particularly advantageous in cases where the measurement of meteorological variables is limited. With the results of this study, progress can be made in the efficient use and management of water resources based on the input parameters of evapotranspiration especially for regions with limited data.

Determination of Sensitivity of the Winter Wheat Crop to Meteorological Factors by DAISY Model    Nilcan Altınbaş1*, Mahir Aydın1, İrem Özmen1,  Barış Çaldağ1, Levent Şaylan1 1 Istanbul Technical University, Faculty of Aeronautics and Astronautics, Department of Meteorological Engineering, Istanbul, TURKEY [*]akatas@itu.edu.tr [*] Corresponding author: akatas@itu.edu.tr [*] ABSTRACT  Climate change or climate variability has always pose a risk for sustainable agricultural production.  Changes in meteorological factors may have different effects on different phenological stages of plants.  For this reason, not only the quantitative change of meteorological factors but also the temporal variation of these factors’ effects of plant growth and yield should be investigated. In this study, DAISY crop growth simulation model was used to analyze the sensitivity of winter wheat plant to meteorological factors during flowering period.  In this context, the effect of changes in temperature, rainfall and total solar radiation during the flowering period has been examined.  Key words:Climate change, Crop growth, Crop yield  [*] Corresponding author: akatas@itu.edu.tr

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Agriculture plays an important role in the global greenhouse gas (GHG) budget andits cycle. CO2 is one of the most important greenhouse gases, and plants releaseCO2 into the atmosphere by respiration and sink it by photosynthesis from theatmosphere. In addition, soil has an essential role in this exchange. Unfortunately,studies on the measurement of greenhouse gases above agricultural crops ininternationally accepted methods are not sufficient, especially in developingcountries. Thus, it is a clear need to determine carbon exchange of agriculturalcrops and activities (sink and emission) by taking into consideration of the specificconditions such as climate, crop variety, soil etc. Eddy Covariance (EC) is one ofthe widely used micrometeorological methods in the world for flux measurementstudies. Developments in measurement and analysis by instruments have allowedthis method to be applied more by researchers for the studies on GHG exchange. Inthis research, carbon exchanges (sink and emission) of watermelon grown inAtatürk Soil, Water and Agricultural Meteorology Research Institute located in theThrace part of Turkey, was measured using the Eddy Covariance method. Finally,estimated gas exchange above crops will be presented.