Weather monitoring and forecasting services for provincial highways and railways in Title by Yan Mingliang1, Yuan Chengsong1 and Pan Xinmin2

Introduction paid increasing attention to traffic lines, which have effectively reduced weather. On 27 July 2005, the China the number of derailments due to high Meteorological Administration and winds. At present, the weather, traffic Along with the rapid increases in the Ministry of Communications and safety departments across China volumes of traffic, safety has become signed a Memorandum for Joint are jointly strengthening their traffic an increasing challenge. Severe Development of Highway Traffic weather services. weather is one of the main causes Weather Forecasting Work, in order of traffic accidents. At the beginning to issue joint national expressway of 2008, persistent snow and frost in traffic weather forecasts. This action Traffic weather southern China led to severe traffic was the start of a nationwide traffic monitoring system disruption, as well as an increased weather forecasting service. number of accidents. Low visibility on expressways induces the tailgating The concept for a traffic weather Traffic weather monitoring of scores, even hundreds, of cars. service developed relatively early network and stations Similarly, highway and railway traffic in some areas, such as is frequently affected by rainstorm Province. Since 1998, after a decade and flooding events, as well as rain- of research, experiments and Traffic weather monitoring must induced geological hazards such as engineering construction, Jiangsu include the monitoring of highway debris flows. Railways in western Meteorological Administration built surfaces, low-visibility weather China are often affected by gales and a traffic weather monitoring network conditions, water temperature and sand- and duststorms. At Hundred- system and developed a traffic a number of other factors. All this Li Fetch near Hami in Xinjiang, gales weather forecasting service. Some information must be transmitted in can induce train derailments. Many other meteorological administrations, real- or near-real time. The automatic water navigation channels in China including , Shanghai meteorological monitoring stations are also frequently affected each year and , have also cooperated covering expressways and water by severe weather such as heavy with traffic departments, selecting transportation routes need to include fog, gales and rainstorms with water important sections of expressways as real-time monitoring of visibility, damage to goods, ship collisions and demonstration sites of traffic weather traffic surface, temperature, humidity, even capsizing. in urban areas and developing wind direction, wind speed and expressway traffic weather monitoring precipitation and, at the same time, In the past decade, China has and forecasting services. meet the technical requirements of experienced record growth in the traffic engineering equipment. construction of air, land and water To mitigate wind damage in navigational infrastructure. All levels Hundred-Li Fetch, the Xinjiang Traffic weather monitoring networks of government, as well as weather Railway Administration constructed consist mainly of four parts: a and traffic departments, have observation sites at the railway weather data acquisition module; a stations in the area. Meteorological weather data processing module; departments developed gale and an information monitoring module; 1 Jiangsu institute of Meteorological Science, Nanjing 210008 sand- and duststorm monitoring and and a weather service information 2 Xinjiang Meteorological Administration forecasting services along railway module.

118 | WMO Bulletin 58 (2) - April 2009 Expressway traffic weather monitoring system

The weather monitoring network system constructed by the Nanjing Institute of Transportation Meteorology on the Shanghai-Nanjing Expressway is one of the most advanced highway traffic weather monitoring systems in China.

It acquires field weather information through 26 automatic meteorological monitoring stations and two highway surface-temperature monitoring stations along the expressway. Monitoring data are transmitted to the receiving centre by means Figure 1 — Time sequence from a visibility sensor (laser-based automatic weather of wireless communication and station) installed adjacent to a key expressway in eastern China (Shanghai-Nanjing) imported into the server database of the Meteorological Administration second half of 2006, the forecasting weather information issue system and and expressway command centre. centre introduced video monitoring a number of other systems. Monitoring Real-time weather monitoring and information sharing along the analysis and application of data in information, weather disaster 101 highways from the Shanghai- real-time and displaying the data on warning and forecasting information Nanjing Expressway Command the same or different screens by time, are then synchronously saved in a Centre. This information has enabled station and/or weather conditions in server database and displayed at the weather observers and forecasters the form of tables, charts and GIS terminal workstations of Shanghai- to directly monitor the weather maps respectively (Figure 1) has also Nanjing Expressway management and road conditions along highway been a substantial advance. It is also and weather departments. segments. possible to set up a colour warning and/or sound alarm for visibility at Such information can meanwhile All the management and safety data each station and then display this be issued and displayed at various from the traffic weather monitoring information (by means of a GIS) for information terminals (information stations and the forecasting products traffic management departments and boards, monitoring terminals, etc.) are entered into a database for the public users (Figure 3). of the expressway. During the management system, the traffic Railway gale monitoring system

The foundation engineering (single station for wind monitoring) for the Lanzhou-Xinjiang railway line in the Xinjiang autonomous region and the network engineering on the northern Xinjiang and southern Xinjiang lines were completed and installed between 1998 and April 2000. Since 1998, this system has been both upgraded and expanded.

It includes digital wind-monitoring instrumentation and optical cable communication and computer network techniques. Other features are a high degree of automation, Figure 2 — Optimizing traffic flow by anticipating high-impact weather events is critical simple and convenient operation, easy on China’s busy expressways. commands, a clear display, friendly

WMO Bulletin 58 (2) - April 2009 | 119 Forecasting of patchy heavy fog The influences on, and damage to, traffic of low visibility and heavy fog are well known. Patchy, heavy fog and local “fog masses” are the focus of current highway traffic weather research. The accumulated monitoring data show that the formation and dissipation of heavy fog are not a process which develops slowly, but a weather phenomenon with relatively obvious evolution [1]. Setting up automatic weather monitoring stations along expressways will facilitate this much-needed area of research.

Some judgments on the forecasting of heavy fog can be made according Figure 3 — Planar display of traffic weather information to the determination of weather type, conditions at both the surface and high interface, stable performance and that of a new generation of radar altitude, analysis of the movement minimal maintenance. monitoring products and other of the cloud system, analysis of automatic weather stations, and the temperature inversion layer At present, the Xinjiang railway gale using the output results of meso- and advection as per the sounding monitoring and alarm system consists scale numerical prediction models. curve, combined with the information of 50 wind monitoring points (small Technological development over the provided by monitoring stations along stations), 32 cross stations (bus past two years has shown that the highways [4]. stations), one data-processing centre warning service has, indeed, reduced (main station of dispatching centre of traffic accidents and produced other Through analysis of the monitoring railway administration), three database economic and social benefits. data and the visibility atlas acquired servers (electronic computation centre of the railway administration), one operation monitoring server (technical – railway support centre) and many computers (customer service terminals). The system operates continuously The Chinese Qinghai–Tibet railway is a high-altitude railway that connects 24 hours a day and includes a real- to . Its total length is 1 956 km. time alarm function. Construction of the 815 km section between Xining and Golmud was completed in 1984. The 1 142 km section between Golmud and Lhasa was inaugurated on 1 July 2006. Traffic weather forecasting technology The Tanggula Pass at 5 072 m above sea level is the world’s highest rail track. The 1 338-m Fenghuoshan tunnel is the highest rail tunnel in the Weather also has a significant world, at 4 905 m above sea level. At 4 264 m above sea level, the 3 345‑m influence on the main lines of Yangbajing tunnel is the longest tunnel on the line. communication, particularly given the relatively small areal More than 960 km—more than 80 per cent of the Golmud-Lhasa section— extent and short duration of many is at an altitude of more than 4 000 m. There are 675 bridges, totalling events. Warnings in advance of 159.88 km, and some 550 km of the railway are laid on permafrost. high-impact weather events has improved by increasing the spatial density of monitoring equipment, the frequency of data uploading, combining monitoring data with

120 | WMO Bulletin 58 (2) - April 2009 various types of weather monitoring information and forecasting service information can be displayed along expressways. Among the information products provided, a series of other weather forecasting service products is available for users. These products have served as an interface for the system and will therefore improve future weather traffic services.

“e-route weather net” (ht tp:// www.16t7.com) is a professional traffic weather service Website. It integrates national and provincial traffic weather monitoring, forecasting information and traffic weather research results, traffic weather news, traffic weather disasters and assessments of all of these. Through sharing the scientific and technological resources of traffic Figure 4 — Some key stretches of railroad in China are particularly susceptible to high weather, this Website provides high- winds, requiring close attention from forecasters. quality services for users from the traffic sector and also provides a over the previous four years, ranges Techniques for gale platform for communication on traffic for speed limits (50-200 m) and forecasting along weather for regional and even national road closures (<50 m) have been weather departments. established. Before the appearance railway lines of main-body heavy fog, an advanced Traffic weather service products oscillation usually occurs. This Through research on gale formation combine long-, middle- and short-time oscillation exists for a short time, and mechanisms and various forecasting forecasting and include special-line even though the visibility value is not methods, an hour-by-hour forecast forecasting, station-point forecasting, particularly low, it serves as a prelude system with a forecasting time of subdivided forecasting, regional to sudden heavy fog and, therefore, 12 hours for representative stations forecasting, warning, important has forecasting value. in 15 km and 50 km stretches along weather forecasting, actual situations the railway line has been established. and holiday forecasting. The monitoring, warning and For hazardous gales (> grade 8) as a forecasting system of low visibility research and analysis object, typical due to heavy fog are much improved gales in different seasons from 2006 to Conclusion by combining conventional meteo­ 2007 were studied. Based on analysis rological observations with of the numerical forecasting model and Traffic weather research and monitoring results transmitted and measurements along railway stations implementation are a new subject displayed by automatic monitoring points, a model forecasting equation in the weather system spectrum due stations with concrete place, time was established. By correcting errors to the significant impact on traffic and numerical values measured along in the model forecasting equation, safety of increased traffic and severe highway segments. This entire system weather conditions in the 1-12 hour weather conditions. integrates synoptic forecasting range were made possible. An hour- methods and numerical forecasting by-hour wind trend for the following Severe weather conditions, including products, including the characteristics 1-12 hour interval is output twice low visibility due to heavy fog, of heavy fog appearing along the daily. high and low temperatures of road Shanghai-Nanjing Expressway. surfaces, heavy rain and snow, It presents the forecasting flow, sand- and duststorms, heavy wind transmits the forecasting results to Traffic weather service and icing on road surfaces are the the highway command department main causes of traffic accidents. and then evaluates the monitoring By combining a traffic weather Constructing an applicable and and forecasting results according to monitoring system, an interface pertinent traffic weather monitoring the road administration report. protocol and access authorization, network system is the basis and

WMO Bulletin 58 (2) - April 2009 | 121 precondition for developing traffic References [3] , Jizhong, 1997: Fractal, weather work. Tsinghua University Press, 1-18. [1] Feng Minxue, Yuan Chengsong, Bian Guanghui and Zhou Zengkui, [4] Yuan Chengsong, Bian Guanghui, Feng The forecasting and warning of 2003: Real-time monitoring and Minxue, Wu Zhen and Zhou Zengkui, severe weather conditions on main characteristics of heavy fog in spring 2003: Monitoring and Forecasting communication lines depend on both at section of Shanghai Nanjing of Low Visibility on Expressways, the judgment of the overall synoptic Expressway. Meteorological Science, Meteorology, .29 11 :36 40. situation and weather type and on 23 4 435-445. monitoring and numerical forecasting [5] Ma Henian et al., 2001: Foundation [2] Bak P. amd K. Chen, 1991: Critical state of Meteorological Service, Xinjiang products. of self-organization. Science, 5 8 16. Publishing House.

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