Long-Term Time Series Variability of Outgoing Longwave Radiation and Interrelationship with Air Temperature over Iraq

Abstract

The OLR is an important and key parameter of the Earth's energy balance. Because of the impact of OLR the heat of the atmosphere rises. Some of this radiation is reflected back and returned to Earth, raising the Earth's surface temperature and playing a crucial role in global warming. The aim of this research is to investigate at the OLR and air surface temperature (AST) time series and trends distributions over five stations in Iraq, and the strength of relationship between these two parameters. The correlation results displayed a strong positive and direct relationship between AST and OLR from September to June with high correlation coefficient (R) ranged between 0.924 and 0.956, except for July and August was moderate (0.713 and 0.783). The monthly time series for both AST and OLR exhibited comparable changes and fluctuated, minimum (decreases, December and January) and maximum (increases, July and August) in trend. The average monthly of AST and OLR variances among the seasons over five considered selected stations; Baghdad, Mosul, Basra, Kirkuk, Rutba. For both parameters, the lowest values in winter (northern region), highest in summer (southern region for AST and western region for OLR), moderate to slightly high in spring and autumn. The AST results observed positive trends in their annual AST series over all stations. The OLR results also appeared positive trends in all station during study period. The relationship between the AST and OLR results appears a high correlation coefficient (R) ranged between 0.713 and 0.95 for all months