Impacts of sea surface temperature on the interannual variability of spring haze days in the Pearl River Delta region
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摘要: 本文利用1979-2018年广东省86站气象观测数据、NCEP再分析资料和ERSST海温资料,采用统计方法分析了年际尺度上热带海温对广东珠三角区域春季灰霾(SHDPRD)的影响。结果表明,东南太平洋海温(ISSTSEP)对SHDPRD起主导作用。低层,当东南太平洋海温异常偏冷时,协同变化效应促使南印度洋海温也为异常偏冷,激发冷Kelvin波东传,引起西太平洋Ekman辐合,导致异常气旋环流出现。异常气旋环流东北风通过等熵滑动机制诱发异常下沉运动,减少华南降水。高层,与 ISSTSEP 有密切相关的是 500hPa 正EU遥相关,使得广东温度降低,降水偏少。EU遥相关调控局地气象要素,形成有利于灰霾形成的气象要素条件。反之亦然。受异常环流影响,与珠三角春季灰霾日数紧密联系的是降水、垂直速度和对流稳定度,其次是边界层厚度和低层东北风,最后是水汽。ENSO对 SHDPRD有一定的调制作用。在 El Nino(La Nina)年春季,珠三角水汽增加(减少),垂直上升(下沉)运动增强,降水增多(减少),广东灰霾偏少(多)Abstract: Based on the daily ground-based observation data of 86 stations obtained from the Guangdong Province Meteorological Service of China, NCEP reanalysis data and ERSST datasets for the period 1979- 2017, it is analyzed the impact of sea surface temperature (SST) on spring haze in Pearl River Delta (SHDPRD) on an interannual scale. It is pointed out that the SST of the southeast Pacific (ISSTSEP) plays a leading role in SHDPRD. Positive (negative) ISSTSEP stimulates the eastward propagation of cold (warm) Kelvin waves through Gill forced response, causing Ekman convergence (divergence) in the Western Pacific Ocean, inducing abnormal cyclone (anticyclone) circulation. It is closely linked with positive (negative) Eurasian-Asian teleconnection pattern (EU), which results in the temperature and the precipitation enhancement (reduction) in Pearl River Delta and provides favorable local meteorological circumstances that are conducive (not conducive) to the haze occurrences. The main meteorological circumstances playing role in affecting the SHDPRD are Precipitation, vertical velocity, and convective, next are boundary layer thickness and low-level northeast winds, and finally is moisture. ENSO in spring has a limited modulating effect on the variation of haze days in PRD region, but not the main effect. In El Nino (La Nina) spring years, the fewer (more) haze occurrence is related to increase (decrease) of the moisture, the enhancement of the vertical upward (downward) movement, and enhancement (reduction) of the precipitation.
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