Analyses of Climate Variability in Jordan using Topographic Auxiliary Variables by the Cokriging Technique

Climatic variability in Jordan is unequivocal resulting from various atmospheric circulations that have complex site-specific characteristics. Trends of change in daily and monthly precipitation, mean air temperature, maximum air temperature, minimum air temperature, relative air humidity, and potential evapotranspiration across the country were investigated by the Mann-Kendall rank and linear regression trend tests using long-term historical meteorological data collected on daily and monthly bases from about 143 stational points. Trend tests indicated significant changes at both national and station levels, where the mean annual precipitation tended to decrease significantly by time at a rate of 1.2 mm per year. Mean air temperature, maximum air temperature, minimum air temperature, relative humidity, and mean annual potential evapotranspiration all tended to increase significantly by 0.02°C/year, 0.01°C/year, 0.03°C/year, 0.08%/year, and 17mm/year, respectively. The Integrated Geographic Information System (GIS), and a geostatistic approach were used for spatial interpolation of selected climatic variables. Cokriging fine resolution maps were generated from integrating climatic variables with elevations obtained from digital elevation maps. The cross validations indicated the efficient use of auxiliary information to aid the interpolation with a very high coefficient of determination and low root mean square errors. The cokriging with elevation as an auxiliary variable is a very flexible and robust interpolation method that exhibited great improvement for estimating several climatic variables in the country.