气候变暖背景下藏东南极端气温指数变化特征

Characteristic Changes of Extreme Temperature Index in Southeast Tibet under the Background of Climate Warming

基于1971~2020年藏东南4个气象站逐日最高气温、最低气温数据,选取世界气象组织气候委员会推荐的14个极端气温指数(ETI),采用线性趋势、R/S趋势分析、M-K检验等方法,分析了近50年藏东南ETI的时空变化特征及其与大气环流指数、太阳黑子和海温指数等之间的关系。结果表明:1) 近50年极端气温极值指数、暖指数和生长季长度(GSL)呈显著升高趋势,冷指数和气温日较差(DTR)为下降趋势。变化幅度中冷指数大于暖指数,夜指数大于昼指数,极高值指数大于极低值指数。2) 在10年际变化尺度上,极值指数、暖指数和GSL在1970~1990 s为负距平,2000~2010 s为正距平,而冷指数相反。3) 除DTR外,ETI表现为较强乃至很强的持续性,未来将保持过去50年变化趋势。4) M-K检测显示,除冷持续日数(CSDI)、DTR之外,ETI都发生了气候突变,其中最高气温极小值(TXn)、暖昼日数(TX90p)、冷昼日数(TX10p)和冷夜日数(TN10p)突变时间较早,发生在20世纪90年代末,其他指数主要出现在21世纪前10年。5) 多数ETI与西藏高原A和B指数、亚洲极涡强度指数、西太平洋副高面积和强度指数、印缅槽强度指数都存在显著的相关关系,以相对指数最为明显。除最高气温极大值(TXx)、CSDI、GSL、DTR外,ETI与太阳黑子具有显著的相关关系,其中冷指数是正相关。6) 绝大部分ETI不仅与西太平洋暖池面积和强度指数,还与NINOW区海表温度距平指数具有显著的相关关系,其中冷指数和DTR为负相关。同时,除最低气温极小值(TNn)、夏日日数(SU)、CSDI、DTR外,ETI与印度洋暖池面积和强度指数也有着显著的相关关系。

Based on the daily maximum and minimum temperature data from 4 meteorological stations in southeast Tibet from 1971 to 2020, 14 extreme temperature indices (ETI) were calculated by the Climate Committee of WMO. The linear trend, R/S trend analysis, and M-K test were used to analyze the temporal and spatial evolution of ETI in southeast Tibet in the past 50 years, and its relationship with atmospheric circulation index, sunspot and SST index et al. The results show that: 1) An upward trend in warm extremes, extremal indices and growing season length (GSL), and a down-ward trend in cold extremes as well as diurnal temperature range (DTR);the magnitudes of changes in cold extremes were obviously higher than those of warm extremes, which in night extremes were higher than those of day extremes, but the magnitudes of changes in extremes maximum value indices were larger than those of extremes minimum value indices. 2) In terms of decadal variations, the extremal indices, warm index and GSL were negative anomaly in 1970s~1990s and a positive anomaly in 2000s~2010s, while the cold index presented the opposite. (3) Except for DTR, Hurst index of ETI displayed stronger or even very strong persistence, that in future will maintain the trend of variability since the last 50 years. 4)According to the M-K test, except DTR and cold spell duration index (CSDI), ETI has undergone abrupt climate changes, among which annual minima of daily maximum temperature (TXn), warm days (TX90p), cold days (TX10p) and cold nights (TN10p) occurred earlier in the late 1990s, and the other indices mostly appeared in the first decade of the 21st century. 5)Most ETI were significantly correlated with the Tibet Plateau A and B indices, the Asian polar vortex intensity index, the western Pacific subtropical area and intensity index, and the Indo-Burma trough intensity index, especially in relative extremes indices. Except for annual maxima of daily maximum temperature (TXx), CSDI, GSL and DTR, ETI and total sunspot number index existed markedly relationship, among which the cold extremes were positively correlated. 6) The vast majority of ETI had significant correlations with not only the western Pacific warm pool area and intensity index, but also the NINO Z SSTA index, among which the cold ex-tremes and DTR were negatively correlated. Meanwhile, in addition to annual minima of daily minimum temperature (TNn), summer days (SU), CSDI and DTR, ETI also were significantly correlated with the Indian Ocean warm pool area and intensity index.