(Source :www.wikipedia.org)

Wind speed and direction are inputs for calculation of evapotranspiration. Wind speeds are controlled by local pressure anomalies which in turn are influenced by temperature and local topographic features. Wind speed exhibits a wide variation not only from place to place but also during the day. The wind direction may influence evaporation if the surrounding environment has different humidity in different directions. Wind speed and wind direction are measured using anemometer and wind vane, respectively. Observations are made daily or twice daily at standard times at 08:30 and 17:30 hrs. Wind speed measurement may be instantaneous or, if wind run over a time interval is observed, then it is accumulative. Wind direction may influence measured evaporation totals if the surrounding environment in terms of wetness differs in different directions.

 Mean Upper Winds Over India and Neighbourhood at 200 mb During April and July.