Source: China Meteorological Administration
June 10, Shanghai, Zhejiang, Anhui Anhui South
Successively announced the entry into the plum
Zhejiang's entry into the plum this year is the same as usual. Photo: Sina Weibo
First semester, Japanese-Namae Iyume
Japan entered the plum early. Source: weathernews
Some provinces (municipalities directly under the central government) of Jianghuai Meiyu District of China
It also entered the plum flood season almost at the same time
But South China, which should have entered the flood season
But it has been affected by drought...
Many netizens said
It doesn't rain where it should rain
It doesn't stop where it shouldn't rain
Did you "deviate" during the flood season this year?
What the hell is going on
Led to plum rains this year and South China
Playing peek-a-boo?
#1华南干旱导致雨水变少?
Since late October last year, South China has suffered a severe drought due to the La Niña incident.
Precipitation is scarce in Southern China, triggering drought. Photo: National Climate Center
Taking Guangdong as an example, the average temperature of the province is 19.3 °C (October 21, 2020 to May 16, 2021), breaking the record of the same period in history (17.8 °C); the average precipitation is 293.2 mm, which is 53% less than the same period of history (624.3 mm), which is the second smallest in the same period of history, and many places have experienced continuous droughts in autumn, winter and spring.
The main causes of drought are:
# 01
SST
Since the autumn of 2020, the tropical western Pacific warm pool and tropical Indian Ocean SST have been significantly warmer, and the Middle East Pacific SST has been cold, making South China in the subtropical high-pressure controlled sinking gas flow zone for a long time, with deviations in water vapor transmission conditions, few typhoons and precipitation, and insufficient reservoir storage.
# 02
La Niña
In addition, last year there was the La Niña incident. Studies have shown that La Niña's following year is not conducive to the precipitation in the autumn, winter and spring of Guangdong.
# 03
Cyclic circulation
In addition, in the spring of this year (March to May), the South China Sea-Philippines region has been controlled by cyclonic circulation for a long time, blocking the transmission of water vapor from the southern ocean to the north, resulting in continuous low precipitation in most parts of Guangdong, and then serious drought events.
However, with the outbreak of summer winds in the South China Sea, South China ushered in the "dragon boat water", and the drought problem was also "solved".
#2江南春雨 "fired" the "first shot" of China's rainy season?
We usually believe that China's rainy season began from the pre-flood season in South China, and this year's rainy Jiangnan, Jianghuai and other places are particularly "grabbing the mirror".
Did the rainy season come early? In fact, it is not, that period should have been the spring rain stage in Jiangnan, but in previous years, the rain during the flood season in South China has been falling, and the spring rainy season in Jiangnan is not clear.
In terms of climatic state, the main rain belt activities of precipitation in eastern China include 7 stages:
Time
place
Late February
Until mid-March
Subtropical precipitation in Jiangnan and northern Southern China began first, but the precipitation intensity was generally 4 mm per day
With the beginning of the spring precipitation season, the intensity of rain in Jiangnan increased in the spring, and the precipitation intensity exceeded 6 mm per day
Late March
Until mid-May
The rain belt in northern South China extends southward to southern China, entering the spring rain in Jiangnan and the mid-to-early flood period in southern China, and the precipitation intensity in southern China reaches 8 mm per day
Mid-to-late May
With the outbreak of summer winds in the South China Sea, South China enters the late pre-flood period, and the precipitation intensity is further enhanced, and the central intensity of the rainy area exceeds 16 mm per day (equivalent to moderate to heavy rain)
Started in early June
The East Asian subtropical monsoon began to be active, and the Jiangnan, Yangtze river basins and Jianghuai river basins entered the plum rainy stage, with precipitation intensities of up to 10 mm per day (equivalent to moderate rain), and the entire plum rainy season generally lasted from early June to mid-July
As the East Asian subtropical monsoon frontier pushes north, North China and Northeast China enter the concentrated precipitation phase in midsummer, but the rain intensity is slightly weaker than that of South China, Jiangnan, Jianghuai, etc., generally 5 mm per day
July to September
Southern China, especially southern China, has entered the post-flood season, which is the rainy season with relatively frequent typhoon activity.
Therefore, the "first shot" of China's rainy season was fired in Jiangnan, not in South China and other places.
#3 "Early" plum rain is not "real" plum rain?
Before 2013, academics also classified the spring rain in Jiangnan from April to May as early plum rain. It was not until the release of the national standard for plum rain monitoring indicators in 2017 that it was clear that there was no concept of early plum rain, because the spring rain in Jiangnan was fundamentally different from the rain during the plum rain period - although the rain had, the temperature was significantly lower, and the location of the subtropical high pressure was also south.
China's plum rain area from Hubei Yichang in the west, east to the East China coast, the southern end of the 28 °n as the boundary, the north to 34 °n belt, involving the administrative regions include Shanghai, Jiangsu, Anhui, Zhejiang, Jiangxi, Hubei, Hunan and other 6 provinces and 1 city, including the middle and lower reaches of the Yangtze River, Jiangnan District and Jianghuai District three different plum rain monitoring areas.
Plum rain standard
Not only to look at the temperature and rainfall of our country, but also to look at the tropospheric atmospheric orbit system in the East Asian monsoon region, especially the subtropical high pressure in the western Pacific Ocean and the South Asian high pressure system at high altitude, and the configuration monitoring and review of various weather factors such as monsoon, westerly zone/subtropical high pressure, and South Asian high pressure.
After monitoring and forecast analysis, on June 10, Shanghai, Zhejiang, Anhui and Southern Anhui just "reached the standard" and announced that they had entered the plum.
Due to the multiple characteristics of complexity, diversity, asymmetry and importance, the plum rain has large geographical differences and obvious inter-annual and inter-annual variation characteristics.
The time scale of the rainy season spans from the week to the sub-seasonal scale, and it has become an important weather and climate phenomenon at the interface between meteorology and climatology. Therefore, every mid-to-late May, plum rain will attract much attention. How long does it last? How much rain does it rain? Is it "violent plum", "shy plum", or "classic plum"? All will attract wide attention and discussion.
But whatever the situation is this year
In the rainy season, we should pay attention to:
Rainy Season "Three Precautions"
The impact of plum rain on health: pay attention to dietary hygiene, do a good job of dehumidification, and regularly open windows for ventilation
Impact of plum rain on agriculture: Preventing the continuous lack of light and rain caused by the pale color of rice leaves and severe waterlogging caused by crop failure
The impact of plum rain on cities: Strengthen the construction of urban waterlogging engineering measures and non-engineering measures, and improve the comprehensive ability of cities to prevent and reduce disasters and seek benefits and avoid harm.
Expert: Zhou Bing, chief expert of climate services at the National Climate Center, Hu Yamin, chief forecaster of the Guangdong Provincial Climate Center
Author: Li Hui, all-media reporter of China Meteorological News