From June 1, Nanjing will enter the main flood season.
The meteorological department expects that the city's climate during the flood season this year is generally biased, drought and flooding, flooding is heavier than drought, and the abnormal weather and climate events are more frequent and stronger.It is understood that the city's meteorological monitoring and early warning has been able to accurately cover each street administrative district for flood control work to provide "hard core" support. This year's flood season precipitation is expected to be more than 2-5 percent
City weather station director Jiang Youshan introduced, according to forecasts, the city's flood season precipitation this year will reach 800-1000 millimeters, more than normal 2-5%. Among them, 1-2% more than normal in June; 5-8% more than normal in July; June-July there is a greater likelihood of concentrated periods of heavy precipitation, there is the possibility of localized flooding, as well as geological disasters. This year, the city into the plum slightly earlier than normal (June 17-19); out of the plum time is late (July 19-20 around the time), the rainy season is long. The amount of plum rain is 320-500 millimeters, compared with the normal 260-300 millimeters is also significantly more.
Jiang Youshan said the difficulty of predicting the weather during the flood season lies mainly in the uncertainty of how quickly El Niño will transform into La Niña. "The current El Niño is in a phase of accelerated decay, which is expected to tend to end this month, and the central and eastern equatorial Pacific may enter a La Niña state in the summer."
News from the National Climate Center also said that by the combined effects of climate warming, El Niño subyear and tropical Indian Ocean warming superimposed, 2024 China's weather and climate more complex.What are the difficulties in forecasting the frequent occurrence of strong convective weather?
May 27, the city occurred strong precipitation process, the city's highest temperature plummeted 10 ℃, early summer overnight into early fall, let people call "difficult to figure out". Nanjing University of Information Engineering School of Atmospheric Sciences Associate Professor Li Huixin introduction, the recent heavy precipitation is mainly due to the south of the low vortex shear line and the northern groove line caused by the joint influence of the "in the context of global warming, the atmospheric water-holding capacity increases, it is more likely to occur extreme precipitation events."
There are many factors affecting heavy precipitation weather. Li Huixin introduced that, limited by the resolution of current instruments and models, certain strong convective weather developed under the influence of local small and medium-scale convective systems (such as tornadoes, squall lines, etc.) could not be fully monitored. In addition, factors such as localized terrain also increase the difficulty of monitoring strong convective weather. "For example, Nanjing has a large difference in precipitation between the Shanyin and Shanyang areas, and some precipitation clouds pass over the Yangtze River with significantly heavier rain, thus making forecasting more difficult and monitoring more difficult."
Even for heavy precipitation due to relatively easy-to-predict large-scale systems, such as fronts, the equations controlling atmospheric motion are nonlinear and disordered. "Deviations in the initial values may lead to a 'butterfly effect' in the system." Li Huixin mentioned that the recent outbreak of the monsoon in the South China Sea has resulted in the transport of warm and humid southwestern air to the eastern part of the country, while the westerly wind belt at mid- to high-latitudes fluctuates violently, guides cold air southward and is prone to convection.Weather monitoring and warning has been refined to every street
While it is true that strong convective weather is difficult to grasp, the elusive strong convective weather is becoming more and more measurable with the development of new technologies.
In Pukou District Meteorological Bureau of meteorological observation field, only to see a variety of equipment "catching the wind and clouds", measuring different indicators of the equipment from the air to the ground, so that the meteorological observation field at first glance a little bit like a "test field".
Pukou District Weather Station engineer Liu Yuan a piece of introduction: "louvered box installed temperature and humidity sensors, able to real-time measurement of air temperature and humidity; tipping bucket rain sensor used to measure the amount of precipitation; more than ten meters high wind tower installed sensors used to observe the wind direction and wind speed ...... "
It is reported that there are four X-band radars in the city, which are capable of fine-tuning the prediction of the location of precipitation clouds. Pukou District X-band radar set up in the old mountain on the top of the lion ridge, it can provide precipitation cloud reflectivity factor, combined reflectivity, echo top height, echo bottom height, cumulative liquid water content, one hour estimated precipitation and other data, can be strong convective clouds "nuclear magnetic resonance" of accurate monitoring.In addition, the meteorological department device millimeter wave cloud radar, Raman rice lidar, wind profile radar, etc., can monitor the cloud microparticles, haze aerial distribution status and vertical direction of the wind direction and wind speed, and the X-band radar complement each other, the occurrence of strong convective clouds and the development of accurate "pulse".
"Radar network" can be a large-scale "sniffing" the internal situation of the clouds, deep into the streets of the meteorological monitoring station is to ensure that the city's meteorological services, "grid veins". At present, every street in the city has a regional meteorological automatic weather station, realizing the temperature, humidity, air pressure, wind speed, wind direction, rainfall six elements of minute-level automatic data collection.
Chen Qu, a senior engineer at the city's Meteorological Bureau, said, "The data can reach the computer desktops of meteorological operations personnel within five minutes, and through the support of powerful data communication and information processing technology, it can provide a decision-making basis for disaster warning, meteorological disaster prevention and mitigation work as fine as each street."
