Assessment of Spatial Distribution and Temporal Trends of Temperature in Iran

Temperature is one of the most important elements of climate, which undergoes temporal and spatial changes under the influence of local and external factors. These changes can cover micro and macroclimate areas as well as short to long-term periods. Therefore, in the present study, the spatial patterns of temperature change in Iran over the past half-century are discussed. To this end, average annual temperature of 383 synoptic stations in Iran during 50 years (1961-2010) were collected from Iran Meteorological Organization. Linear regression and local Moran's I were used to analyze the trend of changes and the spatial patterns respectively. The results of intra-decade changes in temperature showed that the average temperature of Iran has increased significantly in recent decades, and have experienced less significant daily fluctuations at the same time. Results obtained from analysis of intra-decade temperature change trend showed that temperature has dramatically increased as a result of rises in mean temperature levels in recent decades, such that in the fourth (1991 to 2000) and fifth decade (2001 to 2010) the temperature variation trend has increased by 0.17 and 0.1 respectively, while the temperature of Iran in the first and third decade has declined by -0.03. The results obtained from analysis of spatial pattern of intra-decade temperature variation showed that spatial temperature pattern in Iran is mostly influenced by local factors such as latitudes variations. Generally, with increasing latitude in Iran, the temperature decreases. The temperature in the mountainous areas (negative spatial autocorrelation), southern parts, and areas around Persian Gulf, follow a high spatial pattern (positive spatial autocorrelation) due to lower latitudes and special condition of greenhouse gas emission. However, in recent decades, the positive spatial pattern zones have increased significantly as a result of upward temperature trends.