Temporal and spatial Analysis of Evapotranspiration in Libya

Abstract

Evapotranspiration is an important climatic parameter controlling surface energy exchange, energy transport and transformation in the global atmospheric system, with increases in global warming leading to get higher surface temperatures, which may generate more evaporation.  The main objective of this paper is to identify the temporal and spatial changes in potential evapotranspiration and to analyze the characteristics and trends of evapotranspiration across Libya, based on long monthly climatic parameters observed from 16 stations for 50 years (1961-2010). The trends of evapotranspiration are estimated by the Mann-Kendall test. In additional the relationship between potential evapotranspiration (PET) and climate variables that are used to estimate the (PET) was determined using person correlation coefficient. The mean annual potential evapotranspiration of stations across Libya during the period 1961-2010 ranges between1703.5- 2052.5 mm/year at coastal stations and 2501.1 mm/year for the inland station, with the highest estimated PET of 3026.3 mm/year at Sabha. The mean monthly PET during the period 1961-2010 ranges from 71.4 mm/month (January) to 212.1 mm/month (July) at the coastal stations and between 96.2 mm/month (January) to 318.8 mm/month (July) at inland stations; where July represents approximately 12.4% of the annual PET at both coastal and inland regions. Time trend of Evapotranspiration is analyzed and the results from geographical analysis are also presented.

Key Words: The trend of evapotranspiration, Penman-Monteith, climatic parameters.