2014-2015年度黄河宁蒙河段凌情及气象成因

摘要

In ice flood season of 2014~2015 year, the ice characteristics of Ningxia⁃Inner Mongolia reach of the Yellow River were as the following:late of the first ice date, large discharge of the river frozen up, thin of the ice sheet and the smallest ice flood peak during thawing period in history. The intensity of cold air activities at Inner Mongolia reach was weak in winter of 2014~2015 and the temperature was higher than normal. Especially in January 2015, the temperature of Inner Mongolia reach was abnormally high and monthly mean temperature of three stations (Dengkou, Baotou and Tuoxian) was 2.9~4.9℃ higher than the mean annual. Additionally, the 500 hPa and surface (sea level) charts in November 2014 and January to March 2015 showed mainly causes which led the high temperature in the winter of Ningxia⁃Inner Mongolia reach:a) polar vortex maintained at north of 60°N polar regions;b) prevailing zonal circulation in Asia mid latitude was not conducive to the north cold air south;c) mongolia high intensity was weak.%2014—2015年度凌汛期黄河宁蒙河段凌情特点主要表现为首凌日期晚、封河流量大、封河长度短、冰层偏薄、开河凌峰为历史最小等。该凌汛期影响内蒙古河段的冷空气过程强度偏弱，气温较常年偏高，尤其是2015年1月内蒙古河段气温异常偏高，磴口、包头、托克托三站月平均气温偏高2．9～4．9℃。造成宁蒙河段冬季气温偏高的主要因素：①500 hPa高空图上，2014年11月及2015年1—3月极涡均维持在北纬60°以北的极地区域；②亚洲中纬度地区盛行纬向环流，不利于北方冷空气南下；③地面图上蒙古冷高压势力偏弱。