Abstract Using a continuous multi-decadal simulations over the period 1981–2010, subseasonal to seasonal simulations of the Climate Forecast System version 2 (CFSv2) over Iran against the Climatic Research Unit (CRU) dataset are evaluated. CFSv2 shows cold biases over northern hillsides of the Alborz Mountains with the Mediterranean climate and warm biases over northern regions of the Persian Gulf and the Oman Sea with a dry climate. Magnitude of the model bias for 2-m temperature over different regions of Iran varies by season, with the least bias in temperate seasons of spring and autumn, and the largest bias in summer. The model bias decreases as temporal averaging period increases from seasonal to annual. The forecast generally produces dry and wet biases over dry and wet regions of Iran, respectively. In general, 2-m temperature over Iran is better captured than precipitation, but the prediction skill of precipitation is generally high over western Iran. Averaged over Iran, observations indicated that 2-m temperature has been gradually increasing during the studied period, with a rate of approximately 0.5 °C per decade, and the upward trend is well simulated by CFSv2. Averaged over Iran, both observations and simulation results indicated that precipitation has been decreasing in spring, with averaged decreasing trends of 0.8 mm (observed) and 1.7 mm (simulated) per season each year during the period 1981–2010. Observations indicated that the maximum increasing trend of 2-m temperature has occurred over western Iran (nearly 0.7 °C per decade), while the maximum decreasing trend of annual precipitation has occurred over western and parts of southern Iran (nearly 45 to 50 mm per decade).

中文翻译：

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对伊朗气候预报系统第 2 版的 2 米温度和降水产品的评估

摘要 使用 1981 年至 2010 年期间的连续多年代际模拟，评估了伊朗气候预测系统第 2 版 (CFSv2) 对气候研究单位 (CRU) 数据集的次季节到季节模拟。CFSv2 显示了地中海气候的阿尔伯兹山脉北部山坡上的冷偏，以及气候干燥的波斯湾和阿曼海北部地区的暖偏。伊朗不同地区2米气温模式偏差大小随季节变化，春秋季温带季节偏差最小，夏季偏差最大。随着时间平均周期从季节性增加到年度，模型偏差减小。该预测通常分别对伊朗的干湿地区产生干湿偏差。一般来说，伊朗上空 2 米的温度比降水更好地捕捉，但伊朗西部降水的预测技巧普遍较高。对伊朗的平均观测表明，在研究期间，2 米的温度一直在逐渐升高，大约以每十年 0.5 °C 的速度上升，并且 CFSv2 很好地模拟了上升趋势。对伊朗的平均观测和模拟结果都表明，春季降水量一直在减少，1981 年至 2010 年期间，每年每个季节的平均减少趋势为 0.8 毫米（观测值）和 1.7 毫米（模拟值）。观测表明，伊朗西部出现了最大 2 米温度上升趋势（每十年接近 0.7 °C），