黄河宁蒙河段凌汛特征及成因分析

利用NCEP1°×1°的6小时分析资料、常规气象观测资料和水文观测资料,对黄河上游宁夏和内蒙古河段封、开河期的凌汛灾害特征和成因进行了天气动力学和热力学综合分析。结果表明:宁蒙河段凌汛灾害是特定的气象、地理和水文条件所造成的;封河主要是在经向型、开河在纬向型的有利大尺度环流形势下,与冷暖空气的侵入、气温剧烈降升、大气与水体对流失热和增热密切相关;气温的变化取决于温度平流和非绝热因子的作用,冷暖空气的强弱则取决于涡度平流的作用。

Characteristics and Causes of Ice Flood in Ningxia-Inner Mongolia Section of the Yellow River Valley

During the season when the river water freezes or the river ice melts, ice flood disaster usually occurs in Ningxia-Inner Mongolia section of the Yellow River valley. Based on the meteorological and hydrological observations and NCEP/NCAR 6h analysis dataset of 1°×1°, the characteristics and causes of the disaster are analyzed by thermodynamic and dynamic methods. The results indicate that the disaster occurs under some meteorological, geographical and hydrological conditions. The freeze-up/break-up is related closely to the cold/warm air incursion and abrupt decreasing/increasing of temperature under advantageous large-scale circulation. The temperature advection and diabatic factor have an effect on the temperature change, while the intensity of the cold/warm air depends on the vorticity advection.