热带海温对珠江三角洲春季灰霾日数年际变化的影响

Impacts of Sea Surface Temperature on the Interannual Variability of Spring Haze Days in the Pearl River Delta Region

关键词:  珠江三角洲  春季灰霾日数  海温  ENSO  影响机制

Key words:  Pearl River Delta region  spring haze days  interannual variability  sea surface temperature  El Niño-Southern Oscillation (ENSO)

摘要:

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省珠江三角洲（简称珠三角）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 500 hPa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 Ni?o（La Ni?a）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:

The present study analyzed the impact of sea surface temperature (SST) on the interannual variability of spring haze in the Pearl River Delta (SHDPRD) by using daily ground-based observational data from 86 stations of the Guangdong Meteorological Service, along with reanalysis data from the National Centers for Environmental Prediction and the Extended Reconstructed Sea Surface Temperature dataset from the National Centers for Environmental Information for the period 1979—2018. The results show that the SST of the Southeast Pacific (ISSTSEP) played a leading role in the modulation of SHDPRD. Negative (positive) ISSTSEP anomalies stimulated the eastward propagation of cold (warm) Kelvin waves through the Gill forced response, causing Ekman convergence (divergence) in the Western Pacific Ocean and inducing abnormal cyclonic (anticyclonic) circulation. It was closely linked with the positive (negative) Eurasian- Asian teleconnection pattern, which resulted in the temperature and precipitation enhancement (reduction) in the Pearl River Delta and provided favorable local meteorological conditions that were conducive (not conducive) to haze occurrence. The main meteorological conditions playing a role in modulating the SHDPRD were precipitation, vertical velocity, and convective stability, followed by boundary layer thickness and low-level northeasterly winds, and finally moisture. The El Ni?o-Southern Oscillation in spring had a limited modulating effect on the variation of haze days in the PRD region. During El Ni?o (La Ni?a) springs, the fewer (more) haze occurrences were related to increased (decreased) moisture, intensified vertical upward (downward) movement, and enhanced (reduced) precipitation.