Countries located in arid and semi-arid regions of the world, such as Iran, with highly dependent economy to agriculture, are more vulnerable to climate change. Six agro-climatic indices have been used, which include the length of the growing season and the frost-free season, dates of the occurrence of the last frost in spring and the first frost in autumn, and annual sum of the growing degree-days (GDD) for two temperature thresholds. To explore variabilities of the indices in the future, outputs of three regional climate models (RCMs) have been analyzed based on two Representative Concentration Pathway (RCP4.5 and RCP8.5) scenarios for the South Asia CORDEX region, with the horizontal resolution of 0.44°. Differences between the historical and future simulated agro-climatic indices have been calculated, in which the former is obtained from historical outputs of three models for the period 1961–1990, while the latter is based on future simulations during the period 2061–2090 applying RCP4.5 and RCP8.5 scenarios. Both RCP scenarios indicate an increase in the number of frost-free days (maximum 40 and 70 frost-free days according to the RCP4.5 and RCP8.5 scenarios, respectively), with higher changes in mountainous regions. Our results indicate that shorter frost days will be more common in northwestern and western Iran in the future period. The highest increase in annual sum of the GDD will be in southern and central Iran, but the lowest increase will be in northwestern Iran.

位于世界干旱和半干旱地区的国家，例如伊朗，对农业的经济高度依赖，因此更容易受到气候变化的影响。已经使用了六个农业气候指数，包括生长季节的长短和无霜季节的长短，春季最后一次霜冻的发生日期和秋季第一次霜冻的发生日期以及生长度日的年度总和。 （GDD）表示两个温度阈值。为了探索未来的指数变化，基于南亚CORDEX地区的两个代表性集中路径（RCP4.5和RCP8.5）情景，分析了三个区域气候模型（RCM）的输出，水平分辨率为0.44°。计算了历史和未来模拟的农业气候指数之间的差异，其中前者是从1961-1990年三个模型的历史输出中获得的，而后者则是基于2061-2090年期间使用RCP4.5和RCP8.5方案的未来模拟得出的。两种RCP方案均表明无霜天数增加（根据RCP4.5和RCP8.5方案分别最多无霜天数为40和70），山区的变化更大。我们的结果表明，在未来时期，较短的霜冻天数将在伊朗的西北和西部更加普遍。GDD年度总和的最高增长将出现在伊朗南部和中部，而最低的增长将出现在伊朗西北部。两种RCP方案均表明无霜天数增加（根据RCP4.5和RCP8.5方案分别最多无霜天数为40和70），山区的变化更大。我们的结果表明，在未来的一段时间，较短的霜冻天数将在伊朗的西北和西部更加普遍。GDD年度总和的最高增长将出现在伊朗南部和中部，而最低的增长将出现在伊朗西北部。两种RCP方案均表明无霜天数增加（根据RCP4.5和RCP8.5方案分别最多无霜天数为40和70），山区的变化更大。我们的结果表明，在未来的一段时间，较短的霜冻天数将在伊朗的西北和西部更加普遍。GDD年度总和的最高增长将出现在伊朗南部和中部，而最低的增长将出现在伊朗西北部。