Climatology of convective density currents in the southern foothills of the Atlas Mountains
Climatology of convective density currents in the southern foothills of the Atlas Mountains
复制标题
阿特拉斯山脉南麓对流密度流的气候学
DOI：
10.1029/2009jd012863
复制
发表时间：
2010
影响因子：
--
通讯作者：
O. Schulz
中科院分区：
文献类型：
--
作者：
Carmen Emmel;P. Knippertz;O. Schulz
[1]由蒸发冷却的空气提供的密度流是产生沙尘暴的一个重要特征，可以构成干旱地区的一个湿气来源。最近，在个案研究的基础上，证明了在高阿特拉斯山脉和摩洛哥南部撒哈拉沙漠之间地区存在这种系统。在这里，气候分析，使用的数据从密集的气候站网络的IMPETUS项目（一种综合的方法来有效地管理稀缺的水资源在西非）的5年期2002-2006。主要基于风和露点温度的突变的客观标准定义，以识别可能的密度流的情况。然后，借助卫星图像和地面观测对预选的事件进行主观评估，以排除除潮湿对流冷池形成之外的气团变化原因。平均每年测得密度流11 ± 4次，主要季节为4 ~ 9月。由于湿对流的日循环，密度流主要发生在下午和晚上。前缘的平均变化是2 m露点温度和风速分别增加5.4°C和8.2 m s-1，2 m空气温度降低2.3°C。高阿特拉斯和杰贝勒萨格罗被认为是最重要的源区，只有少数系统起源于撒哈拉低地。由于非洲西北部上空的高层槽和水分含量增加而导致的大气稳定化有利于密度流的形成。此外，详细的案例研究代表不同的异重流类型。
[1] Density currents fed by evaporationally cooled air are an important dust storm–generating feature and can constitute a source of moisture in arid regions. Recently, the existence of such systems has been demonstrated for the area between the High Atlas Mountains and the Sahara desert in southern Morocco on the basis of case studies. Here, a climatological analysis is presented that uses data from the dense climate station network of the IMPETUS project (An Integrated Approach to the Efficient Management of Scarce Water Resources in West Africa) for the 5 year period 2002–2006. Objective criteria mainly based upon abrupt changes in wind and dew point temperature are defined to identify possible density current situations. The preselected events are then subjectively evaluated with the help of satellite imagery and surface observations to exclude causes for air mass changes other than moist convective cold pool formation. On average, 11 ± 4 density currents per year are detected with the main season lasting from April to September. Density currents occur mainly in the afternoon and evening due to the diurnal cycle of moist convection. Mean changes at the leading edge are increases in 2 m dew point temperature and wind speed by 5.4°C and 8.2 m s−1, respectively, and a decrease in 2 m air temperature of 2.3°C. The High Atlas and Jebel Saghro are found to be the most important source regions, while only a few systems originate over the Saharan lowlands. Labilization of the atmosphere due to upper-level troughs over northwest Africa and an enhanced moisture content favor density current formation. In addition, detailed case studies representative of different density current types are presented.
影响因子：
4.4
作者：
Knippertz, P.;Deutscher, C.;Schuetz, L.
通讯作者：
Schuetz, L.