广东省2018年5月极端高温天气的特征及成因分析

利用1953-2018年NCEP/NCAR再分析资料和广东省逐日气象要素数据,分析了广东省2018年5月罕见大范围、持续长时间的极端高温天气过程时空分布特征和成因。结果表明:该次过程主要发生在5月中旬中期至月底,梅州高温日数长达15 d。全省高温空间分布呈自东向西逐渐递减的趋势,沿海地区温度较内陆偏低,虽高温日数明显偏少,但大部分地区极端最高气温和高温日数均破历史纪录;南亚高压和副高长时间控制广东地区,以及对流层低层弱的西南风场和辐散场,使得下沉气流增温作用显著,形成了有利于高温炎热天气的大气环流背景场;少云、弱风速和低湿度,以及充足的日照,有利于辐射增温,易出现高温炎热天气。

Characteristics of Extreme High-temperature Weather in May 2018 in Guangdong Province and Analysis of Their Causation

Using the reanalysis data of NCEP/NCAR and day-to-day meteorological elements data of Guangdong from 1953 to 2018, this work analyzes the spatiotemporal distribution of a rare, extensive and persistently long process of extreme high-temperature weather that took place in May 2018 in the province and makes a preliminary discussion of their causation. The result is shown as follows. It happened from mid-May to the end of the month, during which Meizhou’s high-temperature lasted as long as 15 d. The weather tended to decrease gradually from east to west. Having much fewer high-temperature days, the coastal area was cooler than the inland. In most of the province, both extreme maximum temperature and high-temperature days broke historical records. As the Guangdong region was dominated by a South Asia high and a subtropical high in the western Pacific for extended time and a southwest wind field and divergence field were weak at the lower troposphere, descending airflow heated the atmosphere significantly to form a background of atmospheric circulation that was favorable for high-temperature and extremely hot weather to sustain. Small amount of cloud, weak wind speed, low humidity and sufficient sunshine were favorable for the atmosphere to warm up through radiation, making the high-temperature and extremely hot weather more likely to occur.