Atmospheric conditions associated with heavy precipitation events in comparison to seasonal means in the western mediterranean region
Atmospheric conditions associated with heavy precipitation events in comparison to seasonal means in the western mediterranean region
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DOI：
10.1007/s00382-016-3058-y
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发表时间：
2018-08
期刊：
影响因子：
4.6
通讯作者：
S. Khodayar;N. Kalthoff;C. Kottmeier
中科院分区：
文献类型：
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作者：
S. Khodayar;N. Kalthoff;C. Kottmeier
与强降水事件（HPEs）在西地中海地区的秋季大气条件和季节平均条件的差异进行了研究。使用了覆盖2011年和2012年秋季的区域气候模式COSMO-CLM的季节性高分辨率模拟。被认为是在五个不同的子域周围的地中海西部的大气条件，即法国，意大利（北部和南部），西班牙和北非。在HPE期间，水分和不稳定源通常位于海上目标区域的上游，通过快速的低空风向HPE区域输送。陆面高湿的集中和对流的发生与地形密切相关。较强的对流降水事件发生在中等海拔地区，而不是在较高的海拔地区。在HPEs之前确定的大气湿度和不稳定性的显着增加，在两个不同的时间长度中建立：大气湿度增加可以追溯到事件开始阶段之前至少6-24 h，而对流可用势能（CAPE）的增加在事件发生前的几个小时内被检测到。最强烈的HPE通常与较高的综合水汽值、CAPE以及低层和对流层中层风速有关。在所有子域的HPE期间，主要的降水峰值发生在1200和1800 UTC之间，这表明对流降水在大多数HPE中占主导地位。HPEs成熟阶段的综合水汽日循环表明，大气在大部分时间内保持比平均水平更潮湿，只有在下午降水高峰后才有所减少。可忽略的CAPE的特点是平均季节条件，而经典的日周期与下午早些时候的峰值和更高的平均值发生在HPE事件。尽管显着差异的降水分布和特征的调查子域，类似的机制被确定在HPE环境和相当大的对比度相比，平均季节性条件。
The autumn atmospheric conditions associated with Heavy Precipitation Events (HPEs) in the western mediterranean region and differences with respect to the seasonal-mean conditions are investigated. Seasonal high-resolution simulations from the regional climate model COSMO-CLM covering the autumn periods of 2011 and 2012 are used. Atmospheric conditions at five different subdomains surrounding the western Mediterranean are considered, namely France, Italy (North and South), Spain, and North Africa. During HPEs, moisture and instability sources are located generally upstream of the target area over the sea, being transported by fast low-level winds towards the HPE areas. Concentration of high humidity over land and initiation of convection are highly related to the orography in the area. Stronger convective precipitation events occur at mid-level elevations rather than at higher altitudes. The significant increase in atmospheric moisture and instability, identified prior to HPEs, builds up in two different time lengths: atmospheric moisture increase could be traced back to at least 6–24 h before the initiation stage of the event, whereas an increase of Convective Available Potential Energy (CAPE) is detected in the hours prior to the event during the mature stage. The most intense HPEs are in general associated with higher values of integrated water vapour, CAPE, and low-level and mid-tropospheric wind speed. During HPEs in all subdomains, the dominant precipitation peak occurs between 1200 and 1800 UTC suggesting that convective precipitation prevails in most HPEs. The diurnal cycle of integrated water vapour during the mature stage of HPEs shows that the atmosphere remains wetter than average for most of the period and that only a decrease is seen after the afternoon precipitation peak. Negligible CAPE characterizes mean-seasonal conditions while the classical diurnal cycle with the peak in the early afternoon and much higher mean values occur during HPE events. Despite significant differences in the precipitation distribution and characteristics of the investigated subdomains, similar mechanisms are identified in relation to HPE environments and considerable contrasts compared to the mean-seasonal conditions.