In order to evaluate the effects of blocking patterns on the duration of frost waves across Iran, the minimum daily temperatures of 60 weather stations were collected from 20 March 1968 to 21 June 2014. The findings, which were obtained based on the distribution tables of reported temperatures and their frequency variation graphs, resulted in identifying 114 frost waves. We obtained the daily weather maps at 500 hPa from NCEP/NCAR during the peak days of durable frosts, and it was revealed that the formation of low pressures over 20°-70°E and the dominant southwest-northeast troughs at 500 hPa facilitated the influx of cold air from both eastern Europe and central Siberia toward Iran, leading to the average frost duration of 12.4 days. Furthermore, low-pressure centers appeared in a dipole pattern in northern Iran over Caspian Sea and created durable frosts with an average duration of 15.4 days. The effect of omega shaped pattern of the geopotential height on durable frosts demonstrated a sharp difference with two recent patterns leading to the frost occurrence with a 13.3-day duration averagely. Additionally, the slow speed of cold western currents in the rex type of blocking from 30° to 50°N caused durable frosts of 14.3 days. Also, we found a specific reduction in the frequency of blocking patterns, which has occurred in the past four decades. Mostly, the blocking and non-blocking patterns cause long- and short-duration frosts over Iran, respectively.

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春霜波阻塞模式与持续时间之间关系的评价：以伊朗为例

为了评估阻塞模式对伊朗各地霜冻持续时间的影响，收集了1968年3月20日至2014年6月21日的60个气象站的最低每日温度。这些发现是根据报告的分布表得出的温度及其频率变化图，可确定114个霜波。我们从NCEP / NCAR在持续霜冻的高峰期获得了500 hPa的每日天气图，并且揭示了20°-70°E上低压的形成以及500 hPa西南西南东北低谷的形成有助于东欧和西伯利亚中部的冷空气流入伊朗，平均霜冻时间为12.4天。此外，低压中心在里海北部以偶极子模式出现，并形成了平均持续时间为15.4天的持久性霜冻。欧米茄形状的地势高度模式对持久性霜冻的影响表现出明显的差异，最近的两种模式导致霜冻的发生，平均持续时间为13.3天。此外，雷克斯类型的冷西方气流在30°N到50°N之间的缓慢速度导致了14.3天的持续霜冻。另外，我们发现在过去的40年中，阻塞模式的频率有了特定的降低。通常，阻塞和非阻塞模式分别在伊朗造成长期和短期霜冻。欧米茄形状的地势高度模式对持久性霜冻的影响表现出明显的差异，最近的两种模式导致霜冻的发生，平均持续时间为13.3天。此外，雷克斯类型的冷西方气流在30°N到50°N之间的缓慢速度导致了14.3天的持续霜冻。另外，我们发现在过去的40年中，阻塞模式的频率有了特定的降低。通常，阻塞和非阻塞模式分别在伊朗造成长期和短期霜冻。欧米茄形状的地势高度模式对持久性霜冻的影响表现出明显的差异，最近的两种模式导致霜冻的发生，平均持续时间为13.3天。此外，雷克斯类型的冷西方气流在30°N到50°N之间的缓慢速度导致了14.3天的持续霜冻。另外，我们发现在过去的40年中，阻塞模式的频率有了特定的降低。通常，阻塞和非阻塞模式分别在伊朗造成长期和短期霜冻。我们发现，在过去的40年中，阻塞模式的频率有了特定的降低。通常，阻塞和非阻塞模式分别在伊朗造成长期和短期霜冻。我们发现，在过去的40年中，阻塞模式的频率有了特定的降低。通常，阻塞和非阻塞模式分别在伊朗造成长期和短期霜冻。