Analysis of the new ＂sharp weapon＂ of typhoon monitoring and early warning in China
China Meteorological News reporter Xiong Wei
From July 18th to 19th, 2014, the No.9 typhoon "rammasun" (super typhoon level) landed in China for three times. Although the path of "rammasun" is tortuous and changeable, and the intensity increases or decreases rapidly, the 24-hour path prediction error is only 75.8km.. Due to accurate forecast and proper defense by all departments, the disaster situation of "rammasun" is obviously lighter than that of typhoons with the same intensity.
So, what forecasting techniques support our forecasting results? In recent years, what new breakthroughs and progress have been made in typhoon forecasting technology in China? Let’s go into the Central Meteorological Observatory and Guangdong, Hainan and Zhejiang Meteorological Observatory to explore the reasons.
A new "sharp weapon" for typhoon monitoring and early warning
From July 18th to 19th, this year’s No.9 typhoon "rammasun" (super typhoon level) landed in Wenchang, Hainan, Xuwen, Guangdong and Fangchenggang, Guangxi three times. With super vitality and amazing destructive power, "rammasun" broke many records.
Although "rammasun" was threatening, the forecaster accurately predicted its route. The 24-hour path prediction error of the "rammasun" is only 75.8 kilometers; On the 15th, China accurately predicted the landing place and time of the typhoon 72 hours in advance. Behind these achievements, it is the application of new technology of typhoon monitoring and early warning.
"At this stage, with the rapid development of detection means, communication and supercomputers, numerical models can provide forecasters with products with higher and higher accuracy, longer time limit and richer expressions. At present, both conventional weather forecasting and typhoon forecasting are inseparable from numerical models. " Qian Chuanhai, director of Typhoon and Marine Meteorological Forecasting Center of China Meteorological Bureau (hereinafter referred to as Taiwan Strait Center), told the reporter.
At present, the fusion analysis results of typhoon gale inversion based on the static meteorological satellite TBB data, model fine grid data of 10m wind field, typhoon wind speed empirical profile, typhoon real-time positioning information, conventional island automatic stations, buoys, ships, oil platforms and ASCAT ocean wind field are all applied to the analysis of typhoon wind field structure. Although in the eyes of ordinary people, these difficult technical terms are hard to understand, for forecasters, their functions are no less than the "east wind" borrowed by Zhuge Liang.
Accurately describing the distribution of typhoon wind field, especially the scope of typhoon gale circle, is also very important for typhoon prevention and disaster reduction. "In the past, we only gave a simplified typhoon wind circle range based on the empirical profile of typhoon wind speed, such as 350 kilometers in the 7 th wind circle and 80 kilometers in the 10 th wind circle." Qian Chuanhai explained, "In fact, typhoons have various shapes, most of which are not circular, and the radius of the wind circle in each direction may be quite different. This year, we will provide the radius distribution of the four quadrants of the typhoon center, so that the typhoon wind field can be described more accurately. "
In recent years, with the development and application of ensemble forecasting technology, forecasters have added a "new weapon" to forecast typhoons. Ensemble forecasting plays an increasingly important role in typhoon forecasting, especially in the last two or three years, the Taiwan Strait Center has developed a correction technology based on typhoon ensemble forecasting. This technology has helped us to greatly improve the accuracy of typhoon track prediction in the past two years. "This year, we have further improved the ensemble forecast correction technology, hoping to provide better support for typhoon path and intensity forecast." Qian Chuanhai told reporters.
In addition, massive data processing is also inseparable from powerful numerical models. The numerical forecast center of China Meteorological Bureau has a special typhoon numerical forecast team to develop the typhoon numerical forecast model system and provide business services. After nearly two years of continuous improvement, the regional typhoon model GRAPES-TYM and the global typhoon model T639 have improved their forecasting performance, and the forecasting time has also increased from twice a day to four times a day, providing good technical support for forecasters. "In the business application in the past two years, we found that the typhoon intensity predicted by the GRAPES-TYM model was strong, and the typhoon track forecast in the South China Sea was northerly. To solve this problem, in 2013, the Taiwan Strait Center improved the physical process of GRAPES-TYM model and the vortex initialization technology, and calculated all typhoons in 2013. The results show that the improvement effect is more significant. " Ma Suhong, a senior engineer at the Numerical Prediction Center of China Meteorological Bureau, said.
Nowadays, the Taiwan Strait Center and the Numerical Forecasting Center are still improving the typhoon forecasting technology. "At present, the resolution of the regional typhoon forecast model of the numerical forecast center is 15 kilometers, which is far from enough for the strong wind and precipitation forecast caused by typhoons. In the future, our work will focus on improving the high-resolution regional typhoon numerical forecast system, and around this key work, we will carry out research on the improvement of high-resolution model physical process and the application of observation data. Aiming at the development of new technology for vortex initialization, we try to use satellite observation data to improve the description ability of typhoon vortex in the analysis field through advanced data assimilation technology. " Ma Suhong said.
Digital grid forecasting technology accurately depicts typhoon path
The extreme nature of Typhoon No.9 this year (super typhoon level) has created a series of records in the history of Guangdong’s defense against Taiwan: the typhoon has the strongest intensity, the most landing sites and the highest emergency level; Correspondingly, the early warning against Taiwan has also "repeatedly broken records": the defense deployment is the earliest and the forecast is the finest. On July 18th, the governor of Guangdong Province praised "accurate forecast and good service" when he went deep into the first-line guidance work in western Guangdong. When the reporter visited the provincial meteorological department, he learned that the birth of forecast records is inseparable from the improvement of meteorological technology.
As early as July 8, Guangdong Meteorological Observatory accurately predicted that tropical cyclones would bring serious impact to Guangdong Province. From the afternoon of the 12th, the Provincial Meteorological Observatory began to forecast the changes of typhoon path and intensity. According to the forecast and suggestion of the Meteorological Bureau, on the 15th, the Provincial Defense General held a video conference of the whole province to deploy defensive measures; At 22: 30 on the 17th, the emergency headquarters Office of Guangdong Province launched a Class I emergency response to Typhoon 17 hours before the landing of rammasun. It is precisely because of the accurate and timely forecast that compared with the typhoon "Sally" with similar intensity in history, the loss caused by this process is significantly reduced.
The regional numerical forecasting model of Guangdong Key Laboratory of Regional Numerical Forecasting, jointly established by China Meteorological Bureau and Guangdong Provincial Government, has a remarkable forecasting effect on "rammasun". According to Feng Yerong, director of the laboratory, since the beginning of this year, the typhoon forecasting model in the South China Sea has been upgraded from the original horizontal resolution of 36 kilometers to 9 kilometers, and the error in forecasting "rammasun" within 24 hours is 71.9 kilometers, which is significantly higher than last year’s 79 kilometers; The 48-hour error is 91.5 kilometers, while last year, the average 48-hour typhoon forecast error was 126 kilometers. In addition, the Guangdong Meteorological Observatory accurately predicted the landing place and time of the typhoon. The landing place was stably predicted from Leizhou Peninsula to Hainan, and the error of landing time was only half an hour. The prediction of path, intensity and landing time reached the international advanced level.
"Based on numerical weather forecast, the refined digital grid forecast business system independently developed by Guangdong Meteorological Observatory has achieved remarkable results in this’ rammasun’ forecast service." Dr. Cheng Zhengquan, chief forecaster of Guangdong Meteorological Observatory, said that the refined grid forecasting system is based on numerical forecasting and adopts the optimal integrated forecasting technology to interpret the objective model; Forecasters can edit graphical grids intuitively and conveniently, and make subjective corrections to numerical forecasts. Finally, intelligent generation of text, graphics, tables, voice and other forecast products, and the realization of refined grid display.
At 8: 00 on the 16th, the fine digital grid forecasting business system accurately predicted the gale in the northwest of the South China Sea, the coast of western Guangdong, Qiongzhou Strait and Leizhou Peninsula at 14: 00 on the 18th, and was able to describe the distribution of the gale, which reflected its subtlety in professional services, decision-making services and public services. On the 18th, Guangdong Meteorological Observatory provided the provincial party committee and the provincial government with key protection counties (districts) with gale of magnitude 16 or above by using the fine gale forecasting technology in towns and villages.
Cheng Zhengquan said that at present, the fine forecast of typhoon wind and rain has just started. Although the Provincial Meteorological Observatory has done a lot of work in the fine typhoon forecast, there are still some problems, such as the accuracy is not stable enough to fully meet the needs of various services, and effective interpretation and application technologies need to be further developed. At present, Guangdong Meteorological Observatory has set up an ensemble forecasting technology business team to carry out various interpretation, application and correction tests on wind and rain forecasting products, so as to further improve the fine forecasting ability and accuracy of typhoon wind and rain. In the future, the station will also strive to enhance the model capability, improve the fusion and assimilation technology of various data, improve the parameterization scheme, further improve the application level of typhoon multi-model integration and typhoon ensemble forecasting technology and correction, and reduce the forecast error.
In order to further improve the ability of typhoon monitoring and forecasting, Guangdong Provincial Bureau is accelerating the construction of "Safe Ocean" meteorological support project, strengthening the construction of marine buoy stations and island automatic stations, and realizing accurate monitoring of meteorological elements within 200 kilometers of the South China Sea. Give full play to the role of the State Key Laboratory of Regional Numerical Weather Forecasting, vigorously strengthen the research and development of core technologies of meteorological forecasting, strive to reach the international advanced and first-class level in Asia within five years, and provide service assistance to the Pan-Pearl River Delta and Southeast Asian countries and regions, and export technologies and products.
Spread the net of science and technology to catch the wind and rain
No.9 typhoon "rammasun" (super typhoon level) has just left this year, and No.10 typhoon "Medham" (super typhoon level) is approaching the east China coast step by step. Where will Medham land? How big is the wind and rain? The technical team of typhoon and marine meteorological fine forecasting is providing strong technical support for typhoon forecasting service in Zhejiang Province.
At 8 o’clock in the morning of July 22nd, the national morning weather consultation was going on. Luo Ling, chief forecaster of Zhejiang Meteorological Observatory, said: "All numerical models and the objective integrated forecast of typhoon track of Zhejiang Provincial Station show that typhoon’ Medham’ will land in the central part of Taiwan Province from midnight on the 22nd to the morning of the 23rd, and land again on the north-central coast of Fujian from the afternoon of the 23rd to the night. It will bring heavy precipitation to the southeastern coastal areas of our province, southern Zhejiang and western mountainous areas. The maximum precipitation will appear at the junction of Zhejiang and Fujian, and the process rainfall can reach 100 mm-200 mm, and the local area is more than 200 mm. "
Luo Ling’s judgment stems from the solid technical support given by the typhoon and marine meteorological fine forecasting technical team in recent years from the aspects of typhoon path and fine forecasting of landing typhoon wind and rain. The fine forecast of OCF precipitation in provincial stations and the distribution of typhoon and gale areas have been applied in business one after another. The innovation of forecasting technology makes forecasters have reliable localized typhoon forecasting service products. In the typhoon track forecast and evaluation in Zhejiang in 2013, the average error of 24-hour track forecast was 89.4 kilometers, which was significantly higher than that in previous years.
For meteorological stations at or below the provincial level, it is particularly important to do a good job in pre-assessment of typhoon’s wind and rain impact and typhoon disaster after having more accurate typhoon path forecast. Combined with the local weather and climate background, the typhoon and marine meteorological fine forecasting technical team developed the typhoon business numerical forecasting model in Zhejiang Province, which effectively improved the ability to identify the typhoon intensity in the initial value field of the numerical model and the mesoscale weather system in the typhoon circulation area. Based on the model products, a fine forecasting method of typhoon rain is developed, and the gridded precipitation products are output, which provides a solid foundation for meteorological stations in cities and counties in the province to accurately predict the impact of typhoon rainfall. In addition, the team also combined historical data with precipitation grid data to quickly form a targeted typhoon disaster pre-assessment product.
Radar is the most effective tool to detect the changes of typhoon internal structure, and it is also a powerful weapon to do a good job in typhoon rainstorm forecast. The typhoon innovation team obtains relevant maritime radar monitoring data from the network, and expands the coverage of radar jigsaw products, so that typhoons can be monitored and tracked with high precision thousands of miles away, and the distribution characteristics of precipitation intensity can be grasped in advance, effectively improving the timeliness and accuracy of typhoon rainfall forecast.
Compared with the influence of heavy rainfall, the strong winds in typhoons are sometimes more harmful to Zhejiang. Due to the scarcity of observation data at sea and the low accuracy of numerical forecast, how to improve the fineness and accuracy of gale forecast has become the bottleneck of forecast. For this reason, the team members developed a dynamic interpretation forecast technology for typhoon wind field, which objectified the forecaster’s subjective correction information on the typhoon path and intensity predicted by numerical model, and then corrected the typhoon wind field predicted by numerical model to improve the accuracy of typhoon gale forecast.
In addition, the technical team of typhoon and marine meteorological fine forecasting further organized technical forces to carry out research on the forecasting technology of extreme wind release at sea, and corrected the regional error and seasonal error of gale forecasting by using climate methods, so as to further improve the accuracy of gale forecasting. The vision of typhoon innovation team is not only limited to disaster reduction, but also focused on ocean services. The fine forecast products of sea gale have been directly used by coastal cities and county-level meteorological stations to carry out daily business such as fishery gale forecast, route forecast and island tourism forecast. At the same time, the introduction of ensemble forecasting toolbox technology from the Central Meteorological Observatory has further enhanced the ability of forecasters at all levels to predict and judge the strength of strong winds. Forecasters at all levels generally realize that they are more confident in forecasting strong winds through the use of box charts, plume charts, rose charts and strong wind probability distribution charts.
The continuous improvement of typhoon "monitoring"
At 15: 30 on July 18th, it was an unforgettable moment for Hainan people. At this time, this year’s No.9 typhoon "rammasun" (super typhoon level) landed in Wengtian Town, Wenchang City, Hainan Province, bringing a rare storm in history. The maximum gust measured at the buoy station in the east of Hainan Island was above 17, the wind speed reached 74.1 m/s, and the precipitation in Changhua Town of Changjiang River reached 702.1 mm.
"rammasun" is the strongest typhoon in South China since 1973. The accuracy of its forecast is directly related to whether the defensive measures are appropriate or not, and to the safety of people’s lives and property. In this process, the meteorological department of Hainan Province predicted the landing point accurately, the error of landing time was small, and the forecast of precipitation area and magnitude was basically consistent with the actual situation. Since rammasun entered the South China Sea, the meteorological department of Hainan Province predicted that it would land in Wenchang, Hainan; Eight hours before the typhoon landed, it was predicted that "rammasun" would land at around 16: 00 on the 18th. In the forecast opinion, it is clearly pointed out that there will be heavy rain to heavy rain from the northeast to the northwest of Hainan Island, and heavy rain in some areas. Timely and accurate meteorological forecast has been praised by leaders and relevant departments in Hainan Province, calling the forecasting and early warning short message of meteorological department "life-saving short message". The reason why the forecast is so accurate is due to the rapid development of typhoon forecasting technology in Hainan Province.
In recent years, Hainan meteorological observatory network has been improved day by day, the computer performance has been improved rapidly, and the numerical forecasting model has been continuously upgraded, especially with the development and application of multi-source data fusion and assimilation technology, the accuracy of numerical models has become higher and higher, the forecasting time has become longer and longer, and the forecasting guidance products have become more and more abundant. In addition, with the improvement of the application technology of localized interpretation of ensemble forecasting and regional model forecasting, the typhoon forecasting business in Hainan Province has also developed rapidly, especially typhoon track forecasting and wind and rain forecasting.
"In the past, the typhoon path prediction in our province relied on the technical experience of forecasters and the qualitative prediction method based on meteorological theory. Now it has developed into a qualitative prediction method based on numerical prediction and based on man-machine interaction processing system, and comprehensively applied a variety of data and methods. The accuracy of typhoon path prediction has basically reached the international advanced level." Feng Wen, deputy director of Hainan Meteorological Observatory, said. At present, the typhoon forecasting methods of meteorological departments in Hainan Province include the application of dynamic statistical forecasting, multi-model integrated forecasting products and ensemble forecasting products.
According to the research on typhoon storm forecast for many years, this year, forecasters in Hainan Province have established a set of reasonable conceptual models for typhoon storm forecast. Based on the conceptual model of forecast, Hainan Meteorological Bureau judged the gale level in the affected area according to the forecast intensity and local topography when the typhoon landed, and made a reasonable forecast of precipitation distribution by combining various data such as automatic stations, radars, satellites and ensemble forecast precipitation products.
"Although great progress has been made in typhoon path forecasting and wind and rain forecasting technology, the progress in typhoon intensity forecasting is still not great, and there is still a big gap between the interpretation technology of typhoon numerical forecasting and the international advanced level. There is still a certain gap between the ability of typhoon refined wind and rain forecasting and the actual needs of disaster prevention and mitigation in Hainan." Feng Wen frowned slightly.
Due to the lack of typhoon detection data with high spatial and temporal resolution, the mechanism of typhoon intensity, path mutation and violent increase of wind and rain is not well understood, and there is little research on the law of typhoon path change and the complexity of typhoon structure and intensity change after landing, which limits the further improvement of typhoon path, intensity and wind and rain forecasting ability. In the future, Hainan Meteorological Bureau will increase the layout density of buoy stations and mesoscale automatic observation stations in the South China Sea, and further strengthen the typhoon field observation test. In view of the influence of the interaction of different scale systems and circulation at different latitudes on typhoons, we will continue to study the scientific problems related to typhoons landing in Hainan Island, improve our understanding of the physical mechanisms related to the path, intensity, structure and heavy rainfall distribution of landing typhoons, and improve the accuracy of typhoon forecasting in Hainan.
This year, the meteorological department of Hainan Province has planned to add five meteorological buoy stations in the South China Sea, which plays an important role in collecting meteorological data of typhoons at sea, monitoring typhoon tracks and improving typhoon forecasting ability.
(Source: China Meteorological News, third edition, July 24, 2014)