Investigation and Analysis of Spatial Patterns of Terrestrial Outgoing Longwave Radiation (OLR) in the Urmia Lake Basin

Articles in Press

Document Type : Research Paper

Authors

1 University of Tabriz

2 The University of Tabriz

10.22034/gp.2026.71941.3528

Abstract

Outgoing Longwave Radiation (OLR) is a fundamental component of Earth's energy budget, playing a critical role in climatic studies and environmental changes. This research was conducted to analyze the temporal variations and spatial patterns of OLR within the Lake Urmia basin over the period from 1987 to 2024. Monthly OLR data with a spatial resolution of 1° × 1° were extracted from NASA's Giovanni system and applied to the basin area and the locations of regional meteorological stations. For data analysis, statistical methods including the Standard Normal Homogeneity Test (SNHT), trend analysis via linear regression and the Mann-Kendall test, and geostatistical techniques (Inverse Distance Weighting (IDW) interpolation and Geographically Weighted Regression (GWR)) were employed. The results indicated that the annual mean OLR in the region exhibited a significant increasing trend with a slope of 0.1095 W/m² per year, with the most pronounced increases observed during the summer and autumn seasons. Structural breakpoints in the seasonal time series were identified in 1993, 1998, and the 2002–2004 period. The spatial pattern of OLR decreases from the southwest to the northeast of the basin, with the central and southwestern regions experiencing the highest values. The GWR model revealed that the relationship between OLR and spatial location is non-stationary across the basin, providing a significant improvement in predictive accuracy compared to the global model. Variations in OLR in the region may be influenced by factors such as the receding water level of Lake Urmia and changes in land use.

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Journal of Geography and Planning

Articles in Press, Accepted Manuscript
Available Online from 23 August 2026

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