The Effect of Relative Humidity and Surface Wind Speed on the Volumetric Water Content of the Soil for Selected Stations in Iraq

Abstract

Soil Water content plays an important role in global hydrological cycles and regional climate of development weather patterns, plus its take part on production of precipitation and climate change. The aim of this work is to determine the effect of some of meteorological elements on the volumetric soil water content at the first level of the soil (0.0 - 0.07 meter) and study volumetric soil water content for four levels of the soil, and the extent of the volumetric soil water content change at the first level, including with time for four selected areas of Iraq Baghdad, Basra, Mosul and Rutba and four months January, March, July and September during the 33- year period from 1979 to 2011. Work was performed with monthly data relative humidity, surface wind speed at a height of 10 meters and the volumetric soil water content for four levels of the soil. And taken from the European Center (ECMWF), specifically model (ERA- Interim), by taking advantage of some statistical techniques such as simple linear regression, the correlation coefficients Mann-Kendall and spearman rho. The results showed that the volumetric soil water content at the first level of the soil in the event of an increase in all study areas for months January, July and September, and this is shown by the results of the tests and the values of slope, has recorded the greatest value of the correlation coefficient of 0.3 and 0.4 in Baghdad in September and Basra in the month of July and both tests in a row except the connector is in the case of a decrease in the month of January, while in the month of March in the case of a decrease for all study areas have recorded the greatest value for the correlation coefficient of -0.3 and -0.5 in Mosul, and both tests in a row and showed the tests the existence of a few counterproductive correlations to the medium in the month of March for all study areas, the relationship between relative humidity and volumetric soil water content they are a direct correlation medium to high when months January and March, there is no linear relationship in the months July and September for all study areas, recorded the greatest value of the correlation coefficient of 0.6 and 0.7 in the Rutba in the month of January, but both tests, respectively. The surface wind speed relationship of volumetric soil water content is an inverse relationship a few to medium when months January and March in Baghdad and Basra, and there is no linear relationship in the months July and September, Has recorded the greatest value of the correlation coefficient -0.3 and -0.4 in Basra in the month of January, but both tests, respectively. The Mosul and Rutba, influenced by a direct effect surface wind speed, as the volumetric soil water content decreases increasing surface wind speed and vice versa, and this is evident in the month of January in the Rutba becomes the relationship is a positive medium, and there is no linear relationship between volumetric soil water content and surface wind speed in the months March, July and September and this is evident from the high values of P-value.