1960—2017年中国北方气候干湿变化及其与ENSO的关系

基于中国北方424个气象站实测数据，应用FAO Penman-Monteith模型计算潜在蒸散（Potential evapotranspiration，ET₀），使用降水和潜在蒸散数据计算得到标准化降水蒸散发指数（SPEI），以此研究了1960—2017年中国北方干湿时空变化特征，分析了ENSO对北方气候干湿变化的影响。结果表明：中国北方干湿变化的线性趋势总体不显著，四季中春季和冬季变湿趋势明显。空间上，西北西部存在明显的变湿趋势，干旱化趋势主要发生在黄土高原、内蒙古东部和东北东部地区。全区各级干旱事件呈减少趋势，各级湿润事件呈增加趋势，其中以中等干旱的减少最为显著。西北西部中等干旱和极端干旱明显减少，东北北部和新疆部分地区极端湿润明显增加。全区四季3类干旱事件均表现为减少的趋势，3类湿润事件均表现为增加的趋势，西北西部四季3类干旱事件均呈减少趋势。ENSO对北方干湿的影响存在一定程度的滞后性。El Ni?o翌年气候湿润，La Nina翌年气候干旱。在年际和春季2个尺度上，SSTA与翌年SPEI存在显著的正相关关系。

Correlation Analysis of Variation of Dry-wet Climate and ENSO in Northern China During 1960-2017

Based on the long-term daily data measured at 424 meteorological stations in Northern China during 1960-2017, ET₀ was calculated using Penman-Monteith method, Standardized Precipitation Evapotranspiration Index (SPEI) were established using precipitation and evapotranspiration. On the basis of these results, the dryness/wetness trends measured by SPEI and the El Ni?o Southern Oscillation (ENSO) influence on the dryness/wetness threshold over Northern China during 1960-2017 are analyzed. The overall annual SPEI of Northern China fluctuated around the 58-year mean and its linear trend was not significant. The seasonal mean SPEI showed an increasing trend, the mean SPEI had increased more significantly in winter. Seasonally, the more significant wetness trend occurred in spring and winter. Geographically, a significant wetness was apparent over the areas of western Northwest China, and drought trend mainly occurred in the Loess Plateau, the Northern Northeast China and the eastern Inner Mongolia. Moreover, different grades of drought events decreased and different grades of wet events increased across the entire region. Among them, the moderate drought events showed the most significant decreasing trend, moderate and extreme drought events decreased significantly in western Northwest China, extreme wet events increased significantly in northern Northeast China and part area of Xinjiang. Three types of drought events decreased significantly and three types of wet events increased significantly in four seasons, Seasonally, three types of drought events decreased significantly in western Northwest China. The relationship between the ENSO and dryness/wetness climate arrives with a delay. The wet events occurred frequently in the following El Ni?o, the drought events happened often in following La Nina. SSTA had a significant positive correlation with SPEI of next year in annual and spring time scales. The SSTA was one of the factors that had an important impact to drought and wet condition in most areas of Nothern China.