淮河流域降水过程时空特征及其对ENSO影响的响应研究

基于淮河流域35个站点1961~2008年日降水资料,从成因角度研究不同厄尔尼诺-南方涛动事件（ENSO）事件对流域降水过程时空演变特征的影响。研究表明：① 流域降水过程出现沂沭泗河水系变干、淮河水系降水量缓慢增大的特征。② CPW年,年最长连续降水日数、年最长连续降水量的距平变化幅度大且为负值;EPC年,年最长连续无降水日数较常年明显增多;EPW年,连续降水日数变长、连续降水量减少。③ ENSO对流域强降水影响较大,在CPW和EPW年淮河水系暴雨、大雨日数较常年多,而沂沭泗河水系暴雨、大雨日数比常年少;EPC年与此相反。④ ENSO对连续4 d以上降水影响显著,其中EPC年影响最大。

Spatial and Temporal Characteristics of Precipitation in the Huaihe River Basin and Its Response to ENSO Events

Study of the precipitation structure is theoretically and practically important for the development of human understanding of impacts of climate changes on regional hydrological cycle and also for regional water resources management and also for planning and management of agricultural activities and it is particularly true for the Huaihe River Basin, one of the key agricultural product suppliers in China. Flood and drought disasters are serious and prevailing in Huaihe River Basin, so it is important to analyze precipitation changes in terms of process and structure and related causes behind. Based on daily precipitation data from 35 precipitation stations covering the period from 1961 to 2008 in Huaihe River Basin, the spatiotemporal characteristics of precipitation structure are investigated and possible linkage to different ENSO events has been explored. The ENSO events considered in this study are: the Eastern Pacific warm events (EPW), Central Pacific warm events (CPW), and the Eastern Pacific cold events (EPC). The results indicate that: 1) The Yi-Shu-Si Rivers are in drying tendency and precipitation in the Huaihe River is in increasing trend. The NCD increased, while the MCD decreased in the northern Hai River Basin. Besides, significant increase of the ATP is found in the Huaihe River Basin, which may have the potential to trigger increase of downstream streamflow. While the MCD and MCP increased which significantly decreases the precipitation intensity; 2) During the CPW event, MCD and MCP changes are subject to large magnitude and in negative cumulative difference anomaly; During the EPC event, NCD increased significantly when compared with NCD changes in normal years; while the consecutive rainy days are lengthening during EPW event are with decrease of precipitation amount; 3) The heavy precipitation in Huaihe River Basin tends to be intensifying under the influences of ENSO regimes. The heavy rain and rainstorm during different ENSO events are subject to large difference anomaly and the anomaly index can reach + 50%. The EPC and CPW events have the potential to trigger flooding events in Huaihe River Basin, such as 1964, 1991and 1998 when flood occurred. In CPW and EPW events, the number of days with heavy rain and storm is more than that in normal years in Huaihe River Basin, and heavy rain days are less than those in normal years in the Yi-Shu-Si river system; In EPC events, the number of days with heavy rain and storm is less than in normal years in Huaihe River, and heavy rain days are more than in normal years in the Yi-Shu-Si River system: 4) ENSO events have impact on 4-day consecutive precipitation event significantly, and it is particularly the case for 5-day consecutive precipitation events. Precipitation anomaly is greater in EPC event in the Huaihe River Basin than in the CPW and EPW events. The precipitation anomaly index except for 1- and 2-day precipitation, are higher than + 40%. The precipitation anomaly index for 6-day precipitation event is larger than 50% during 5 out of 10 years. Floods with different magnitudes occur during EPC event in Huaihe River Basin and 6-day consecutive precipitation event is subject to the biggest anomaly during CPW event and the anomaly index can reach + 50%. The results of this study can well elucidate changing properties of precipitation events with different durations and also possible causes by analyzing changes of different precipitation events during different ENSO regimes.