刘珂 安智伟 刘吉峰

摘 要：为了给黄河凌汛期防灾减灾提供理论参考和数据支撑，利用气象、水文等观测数据和水气界面热量平衡方程，对黄河内蒙古河段冷空气活动特征、首凌前期水体失热特征进行研究，并对2011—2019年首凌前期水气界面的热量交换特征及其气候影响因素进行了分析，结果表明：1961—2019年黄河内蒙古河段冷空气过程发生频次约为65次/a，其中寒潮发生频次约为7次/a;首凌约97%发生于冷空气过程中，这些冷空气有33%属弱冷空气、37%属寒潮，首凌当日的冷空气过程从弱冷空气过程向强冷空气过程过渡;1971—2019年黄河内蒙古河段平均首凌日期为11月18日，2011—2019年平均首凌日期较2000年以前推迟6.6 d，首凌前期河道初始水温上升对首凌日期具有明显延迟作用;2011年以前首凌前期水气界面总感热通量与过程径流总量显著正相关，2011年以后二者关系显著减弱，同流量条件下河道水温由5 ℃降至0 ℃的水气界面感热通量异常偏大，沿岸土壤温度梯度减小、冷空气活动频繁和地表风速显著加快是首凌前期水气界面感热通量异常增大的原因。

关键词：首凌;感热通量;河道水温;冷空气;黄河内蒙古河段

Abstract：Based on the ground-based meteorological and hydrological data， the characteristics of first streaming ice date in Inner Mongolia Reach of Yellow River and air-water heat fluxes were studied. The new features appeared after the year of 2011 and its attribution analysis also were traced. The results show that the average cold air event number is 65 times per year during the period 1961-2019 and the cold wave is 7 times. About 97% of the first streaming ice of the river section is occurred in the process of cold air， of which 33% are weak cold air and 37% are cold waves. The probability of cold air process occurrence on the river first streaming ice date is from weak to strong. The average date of first streaming ice in Inner Mongolia reach of the Yellow River is on November 18 for the period from 1971 to 2019. From 2011 to 2019， there are 6.6 days later than that before 2000. The initial water temperature rise of the channel in early stage delays the date of the first streaming ice significantly. Before 2011， the total air-water sensible heat flux is significantly and positively correlated with the total river flow and the relationship is remarkably weakened after 2011. Under the conditions of the same discharge， the water temperature drops from 5℃ to 0 ℃， the accumulated sensible heat flux at the air-water interface shows abnormally large. The decrease of soil temperature gradient and the increase of surface wind speed are possible climatological causes for the large anomaly occurred after the year of 2011.

Key words： first streaming ice; heat fluxes; river temperature; cold surge event; Inner Mongolia reach of Yellow River

黄河宁蒙河段（宁夏石嘴山—内蒙古头道拐）地处黄河流域最北端，海拔在1 000 m以上，距离海洋遥远，冬季常被蒙古高压控制，大陆性气候特征明显，气候寒冷，日平均气温在0 ℃以下的时间可持续4～5个月。该河段凌汛期通常从11月中下旬开始流凌，12月上旬封冻，次年3月中下旬解冻开河，封冻期封冻长度可达1 000 km[1]，冰凌灾害严重，1949年以來发生凌灾约30次[2]。……