Precipitation dynamics in Ecuador and northern Peru during the 1991/92 El Nino: A remote sensing perspective
Precipitation dynamics in Ecuador and northern Peru during the 1991/92 El Nino: A remote sensing perspective
复制标题
1991/92厄尔尼诺期间厄瓜多尔和秘鲁北部的降水动态：遥感视角
DOI：
10.1080/014311600210731
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发表时间：
2000
影响因子：
3.4
通讯作者：
J. Bendix
中科院分区：
文献类型：
--
作者：
J. Bendix
利用气象卫星3号图像、基于NOAA-AVHRR的多通道海面温度(MCSST)和附加气象观测资料，研究了1991/92年厄尔尼诺期间厄瓜多尔和秘鲁北部强降水的形成、动力学和空间分布。利用气象卫星红外资料利用对流和层状技术(CST)反演降水，并对气象卫星图像序列进行互相关处理，得到云运动风(CMW)，这对于分析导致强降水的环流模式是必不可少的。通过对45天强降水天气的分析，证实了暴雨形成的三种机制。每一种机制都揭示了一种特定的局部影响。(1)最常见的机制(∼的频率为61%)代表了一个延伸的陆海风系统。在这样的天气条件下，主要发生了局部受限的降水模式。白天受海风锋面影响的地区是西安第斯山坡上1000米等高线以下的沿海平原。导致降水的多云频率的局部最大值可出现在沿海较低的珊瑚的孤立山峰上。夜间，瓜亚基尔湾温暖的水面上的降水频率最高，这主要是由于其沿海形状非常有利于夜间陆风的汇聚。(2)下午在沿海平原和西安第斯山坡开始的对流，由于亚马逊盆地卷云屏蔽层的残余物夹带而显著加强。这些云碎片在对流层中上层以发达的贸易溢出安第斯山脉，与每日的海风/上坡风吹向相反的方向。溢流点的特点是西安第斯山坡上有深对流区域，经常是垂直于山脉和厄瓜多尔南部安第斯凹陷的山谷轴线。(3)厄尔尼诺主期(3-4月)，沿海平原大范围持续强降水，既没有明显的日循环，也没有明显的优势区域。深对流经常在中尺度对流复合体(MCC)中组织，并与MCSST和GT；27在空间上相关。对流层在这些天气条件下的广泛不稳定表现为对流云层街道和厄瓜多尔南部和秘鲁沿海经向哈德利环流的加强。
The formation, dynamics and spatial distribution of heavy precipitation during the 1991/92 El Nino in Ecuador and northern Peru were examined by means of Meteosat-3 imagery, NOAA-AVHRR-based multichannel sea surface temperatures (MCSST) and additional meteorological observations. The Convective and Stratiform Technique (CST) was used for rain retrieval by means of Meteosat IR data and a cross-correlation approach was applied to Meteosat image sequences to derive cloud motion winds (CMW) which are essential for the analysis of circulation patterns leading to severe precipitation. From an analysis of 45 days with severe precipitation it is proven that three mechanisms were responsible for the formation of heavy rains. Each mechanism reveals a specific localized impact. (1) The most frequent mechanism (frequency of ∼61%) represents an extended land-sea breeze system. During such weather conditions, predominantly locally confined precipitation patterns occured. Areas affected by the sea wind front during the day were the coastal plains up to the 1000 m contour line on the western Andean slope. Local maxima in the frequency of cloudiness leading to precipitation could be found at isolated peaks of a lower coastal cordillera. At night the highest frequency of precipitation was found over the warm water surface of the Gulf of Guayaquil, mainly due to its coastal shape which significantly favours convergence of the nocturnal land breeze. (2) Convection, initiated in the coastal plain and on the western Andean slopes during the afternoon, was significantly intensified by an entrainment of remainders of cirrus shields from the Amazon basin. These cloud fragments spilled over the Andes with well-developed trades in the mid/upper troposphere which blew in the opposite direction to the daily sea/up-slope breeze. The spill over points were characterized by areas of deep convection on the western Andean slopes and were frequently valley axes perpendicular to the mountain chain as well as the Andean depression in southern Ecuador. (3) During the main El Nino phase (March-April), heavy and persistent precipitation was extended over wide areas of the coastal plain showing neither a distinct diurnal cycle nor preferential areas. Deep convection was frequently organized in mesoscale convective complexes (MCC) and was spatially correlated with MCSST > 27 . The extensive instability of the troposphere during these weather conditions was marked by convective cloud streets and an intensification of the meridional Hadley circulation off the coast of southern Ecuador and Peru.