极点对称模态分解下西安高温天气的趋势特征

基于1960-2016年西安均一化气象资料,采用极点对称模态分解法,对西安市的高温天气变化特征进行分析,探讨赤道东太平洋海温异常（El Ni?o）、西太平洋副热带高压变化（WPSH）,与西安极端高温变化的关系。结果表明：① 采用非均一化数据,会低估西安暖夜、夏季、热夜、热浪日数变化趋势,高估冬季供暖能耗下降幅度、夏季制冷能耗上升幅度,对暖昼、高温日数影响相对较小。② 在年代变化上,暖昼、热浪、高温日数和制冷度日等四个指标,反映西安白天高温变化特征,呈现一致的四阶段“下降—上升—下降—上升”的变化过程;表征夜间高温变化的暖夜和热夜日数,以1993年为节点,呈现两阶段“阶梯状”的上升趋势。③ 在影响因素上,赤道太平洋中西部海温异常与西安高温关系更为密切。当Ni?o 4区海温异常偏高时,西安暖昼、夏季、炎热天气制冷耗能明显增加,寒冷天气供暖能耗显著降低;同时,当WPSH强度越大,控制面积越大、西伸脊点偏西时,西安暖夜、夏季、热夜日数明显增加、寒冷天气供暖能耗明显下降。

The nonlinear trends of high temperature weather in Xi'an by extreme-point symmetric mode decomposition method

The analysis of the nonlinear trends and non-stationary oscillations of high temperatures and heatwaves in Xi'an, based on 8 extreme high temperature indices, is performed using homogenized temperature dataset over the period of 1960-2016. Temporal trends and their impact factors are evaluated by climate diagnosis methods including extreme-point symmetric mode decomposition (ESMD) and correlation analysis.The effect of air-sea anomalies such as El Ni?o and West Pacific Subtropical High (WPSH) to extreme high temperatures are explored. The results are as follows: (1) Using the in-homogeneity dataset, the warming trends of warm nights, summer days, hot nights, and heatwaves are underes- timated, the downtrend in the heating energy consumption and the uptrend in the cooling energy consumption are overestimated; while the trend change of warm days and high temperature days are affected little by in-homogeneity data. (2) Meanwhile, warm days, heatwaves, high temperature days and cooling degree days, reflecting the characteristics of extreme high temperatures in the daytime, show the fluctuations of decrease-increase-decrease-increase; warm nights and hot nights, which describe the features of extreme high temperatures in the nighttime, exhibit the low stationary fluctuation before 1993 and high stable fluctuation afterwards; (3) With regards to influencing factors, sea surface temperature anomaly in the Ni?o 4 region is closely related to high temperatures in Xi'an. When sea surface temperature in the Ni?o 4 region is high abnormally, warm days, summer days and cooling energy consumption increase significantly whereas heating energy consumption decreases obviously. When the intensity of WPSH increases and its control area enlarges, with its ridge point expanding westward, warm nights, summer days and hot days increase obviously, while heating energy consumption decreases.