Trends in Diurnal Temperature Range Changes in Iraq

Abstract

Diurnal Temperature Range (DTR) is a vital indicator of climate variability, especially in arid regions. Therefore, this study aimed to analyze the trends of the daily temperature range in Iraq over the period 1970–2024, based on daily minimum and maximum temperature data derived from ERA5 reanalysis datasets at both annual and seasonal scales. Sixteen points representing meteorological stations across Iraq were selected. The Mann-Kendall test and simple and partial correlation analyses were employed. The results revealed a significant increase in both minimum temperature (Tmin) and maximum temperature (Tmax), with average rates of 0.55°C and 0.46°C per decade, respectively. This increase consequently led to a decline in the annual DTR at a rate of -0.07°C per decade. Seasonally, the decrease in DTR was more pronounced during autumn and summer, with the northern and central regions exhibiting greater clarity in the summer season. This decline is primarily attributed to the faster rise in Tmin compared to Tmax during these two seasons. Correlation analyses indicated that changes in Tmin and Tmax are the most influential factors affecting DTR. Additionally, wind speed showed a significant negative correlation with DTR, while solar radiation exhibited a positive correlation. The effects of precipitation, humidity, and cloud cover were found to be weak. This study provides a fundamental understanding of DTR variability and its driving factors, which is essential for future climate change assessments and the development of adaptation strategies in Iraq