Beijing News Express (Reporter Deng Qi) From August 11th to 13th, Beijing-Tianjin-Hebei and other places will see the strongest rainfall since the flood season, and the local accumulated precipitation in Beijing-Tianjin-Hebei and other places will reach 150-200 mm. Zhang Tao, chief forecaster of the Central Meteorological Observatory, introduced on the 11th that it is currently expected that this round of heavy precipitation in Beijing-Tianjin-Hebei is not uncommon, and is a typical process of heavy precipitation during the main flood season in the region.
"Have not seen for many years" experience has great individual differences
The Beijing News: The recent strong convective weather in Beijing and other places, some citizens feel that they have not seen such gusts and showers for many years. The Beijing-Tianjin-Hebei region will usher in the heaviest rainfall in the flood season this time. Are these weather processes rare recently?
Zhang Tao: First of all, it needs to be clear that some people feel that there are very large individual differences in the expression of "have not seen such hurricanes and rains for many years," and it is difficult to represent a common phenomenon. From the perspective of meteorological observations, such weather in Beijing is not uncommon. For example, on "5.17" last year, Tongzhou experienced extreme precipitation and hail with a diameter of 5 cm. So, people in Tongzhou have this feeling, but people in Xicheng and Haidian may not have this feeling. But for meteorological observations, the occurrence of strong convective weather in Beijing area is mainly caused by locality.
This round of heavy precipitation in the Beijing-Tianjin-Hebei region is a typical process in the midsummer period of the Beijing-Tianjin-Hebei region, especially during the main flood season of "seven down and eight up". In theory, there will be at least once or twice a year, so from this perspective, it is not rare. But in the end, we need to evaluate afterwards. From my personal experience, if according to the current forecast, this round of precipitation is not uncommon, it is a typical process of heavy precipitation.
Beijing News: From the 15th to the 17th, there was another precipitation in the north. What was the intensity?
Zhang Tao: From the 15th to the 17th of this northern precipitation process, it is still difficult to judge whether the intensity can match this process. At present, it may be slightly weaker, but there are relatively large variables that require close judgment.
The risk of urban flooding and flash floods will increase significantly
Beijing News: For the north, what are the difficulties in preventing such heavy precipitation?
Zhang Tao: The characteristics of this round of heavy rainfall in the north are similar to those in the south, and the water vapor conditions and rainfall mechanism are the same as the heavy rainfall in the southern summer. Because the north does not rain very much all year round, and under this background, the rainfall equal to the intensity of the heavy rainfall in the south will bring greater flood control pressure.
In this round of heavy rainfall in the Beijing-Tianjin-Hebei region, the hourly rain intensity is expected to be 30 to 50 mm, but in extreme cases it may reach 80 to 100 mm. Such a strong rainfall intensity will greatly increase the risk of urban flooding and flash floods in the north.
In addition, since this is a large-scale weather process, the rainfall on the surface may also be relatively strong, which also brings pressure to the flood control of the Haihe River Basin.
For the public, what needs to be guarded is to travel cautiously in mountainous areas and guard against geological disasters such as mountain torrents, landslides and mudslides. In urban areas, try to avoid entering some low-lying areas that are prone to rapid water accumulation when rainfall occurs. In addition, we must pay attention to prevent strong convective weather processes such as strong winds and thunder and lightning.
Beijing News: Since the beginning of this year, extreme weather such as heavy rainfall, drought, and high temperature has occurred frequently. Looking at it now, is this year of abnormal climate?
Zhang Tao: Since the beginning of this year, extreme weather such as heavy rainfall, drought and high temperature have occurred frequently. It should be said that these weathers occur every year in our country, and they occur on a large scale. For example, when the main rain belt is in South China, it is a period of heavy rainfall in South China. When the main rain is brought to Jiangnan, it is the rainy season. When the main rain belt travels north to Northeast and North China, it is the heavy rainfall in the north. Conversely, the places controlled by the subtropical high are facing long-term high temperatures, and some places are still arid, which is a long-standing climate phenomenon.
From the current point of view, the climate has indeed been extreme this year, not a year-round average condition, and is in a more abnormal direction. I personally think that this year may be a year of relatively abnormal climate, but the final degree of abnormality requires a climate assessment afterwards.