FORECASTING AND WARNING OF TROPICAL CYCLONES IN CHINA

With the development of the global economy, the impact of tropical cyclones has become far-reaching. Thus they are a fundamental issue to be addressed both nationally and globally. The socio-economic impact is particularly noticeable in developing countries, especially China. This paper begins with the effects of cyclones on regional and global economies. Then a brief introduction to the past and current situations and progress in cyclones forecasting and warning in China are presented. Finally the paper gives recommendations about improving and perfecting the tropical cyclone forecasting and warning systems.


INTRODUCTION
China is one of the countries affected most severely by tropical cyclones. Generally speaking, every year about 27-28 tropical cyclones form over the northwestern Pacific Ocean and South China Sea, and seven of these make landfall over China's coastal areas. There is also a slightly increasing number of those reaching land.
Tropical cyclones are the most disaster-inducing weather systems over the Southeast China coastal area from early summer to autumn every year. They often bring a large number of casualties and great damage to the coastal areas with gales, torrential rains, and storm surges during their landfall. They may also cause great damage to inland areas when they interact with middle-latitude synoptic systems during northward motion after landing. On the other hand, tropical cyclones are an important water resource for some Southeast China areas during summer. The intense rainfall that accompanies the storms relieves drought conditions in these areas.
Therefore, exact and timely forecasting and warning is of significant importance in the struggle against tropical cyclones in order to mitigate their impacts on the population. In China, because tropical cyclone forecasting and warning have always been of major concern to all levels of government and other organizations, great progress in monitoring, forecasting and forewarning these cyclones has been made.
human survival are tropical cyclones, earthquakes, floods, thunderstorms and tornados, snow storms, snow slides, volcanic eruptions, heat waves, mud-rock flows, and storm surges. Among these, the death toll of tropical cyclones is the greatest, especially in Asia where damage from tropical cyclones is very severe.
Statistics indicate that the direct annual economic loss as result of tropical cyclones' invasions is about 26.38 billion Yuan RMB with a annual death toll of 440 from 1988 to 2005 (Figures 1 & 2). In 2005, eight tropical cyclones made landfall over China. Six of these became typhoons and two were severe tropical storms. The fastest central wind velocity (59.5m/s) was recorded when Typhoon Khanun (0515) made landfall. Four of six typhoons caused 10-20 billion Yuan RMB of direct economic loss. In these disasters, over 100 people died in Typhoons Talim (0513) and Longwang (0519), and the loss from the cyclones was 39% of that year's total ( Figure 3). In contrast, from January to September 2006, seven tropical cyclones made landfall over China's coastal areas, and more than 71 million people and 28,900 km 2 of farmland were affected. 1,261 people were killed, and 420 people were missing. 670 thousand houses were destroyed and 1,360 thousand houses were damaged. Direct economic losses were about 76.4 billion RMB Yuan (Figures 1 & 2).  China from 1988to Oct. 2006

PROGRESS OF TROPICAL CYCLONE MONITORING IN CHINA
Currently, with consistent efforts made over many years, substantial progress has been made in tropical cyclone monitoring using such methods as satellites, radar, and Automatic Weather Stations (AWS).

Satellite Remote Sensing
As in many other countries, China depends mainly on satellites for tropical cyclone detection. So far, China has launched four polar-orbiting meteorological satellites (FY-1 series) and three geo-stationary meteorological satellites (FY-2 series). The FY-1C has been functioning for nearly five years, and the FY-1D has been operating normally for about three years. The FY-2B has been put into a geo-stationary orbit for two years, and the FY-2C For more 30 years, China has had a satellite data receiving and processing system, which receives and handles different satellite data on a timely and accurate basis, and a number of products have been developed for tropical cyclone characterization and applications. All this information has become a useful tool for tropical cyclone detection and monitoring. The regional and global satellite data, which has been accumulating for years serves as a solid basis for tropical cyclone-related research and data sharing.

Weather Radar
Weather radar is one of the key means of monitoring and forecasting tropical cyclones. Considering its higher temporal and special resolutions and its timely and accurate detecting capacities, weather radar has proven to be a very effective tool for tropical cyclone monitoring and forecasting. According to requirements for its operational development, the China Meteorological Administration (CMA) has worked out a national weather radar deployment plan in coordination with relevant authorities, in which 158 Doppler weather radar sets are planned for China, in which jointly installed weather radar sets will act as a unified radar network to share radar observations, ensure timely acquisition of radar data, and make full use of radar resources in a comprehensive manner. Based on quality control, all weather radar data can be shared nationally through high-speed information networks. Up until now, 105 sets of Doppler radar have been installed and put into operation (Figures 8 & 9).

Automatic Weather Stations
With substantial support from local governments, CMA has mobilized financial resources to establish several AWS networks for meso-and small-scale meteorological observations and some automatic rain-gauges at provincial levels within the CMA framework. Our operational practices demonstrate that AWS and other automatic instruments have played a key role in pinpointing tropical cyclone tracks and landing times. Up until now, 12778 sets of AWSs have been put into operation ( Figure 10).

Strong Wind and Heavy Rain Forecasting
At present, the CMA has no objective methodology for operational forecasts of strong wind and heavy rain induced by tropical cyclones. The local weather bureaus in areas affected by tropical cyclones have to, according to their own needs, develop quasi-theoretical and quasi-empirical techniques or diagnostic statistical methodologies to forecast the intensities and locations of strong wind and heavy rain. However, in the U.S.A., where potential hurricane impact is severe, a real-time in-situ analysis and warning system based on ground radar, surface data, and GIS information has been developed. Meanwhile, research efforts are being made to estimate rainfall by unconventional means including satellites, ground and airborne radar, and the impact of microphysical processes on precipitation. Finally, attempts have been made to use Numerical Weather Prediction Models (NWP) to operationally forecast wind and rain associated with hurricanes.

IMPROVEMENT IN THE OPERATIONAL TROPICAL CYCLONE WARNING SYSTEM
Some progress in operational tropical cyclones warning and service systems have focused on the following during recent years in China: In this connection, the CMA has also worked out a 4-level warning signal and associated rules for issuing ( Figure   13), set up a regular (monthly) new release system for meteorological information and for disasters and a direct reporting and evaluation system for meteorological disasters. In the framework of Meteorological Law, CMA has

Investigation after a Tropical Cyclone landing
The amount of disaster or breakage induced by tropical cyclones, especially the destruction produced by gale force wind, differs according to the intensity and landing site of the storm. It is very important to understand the

Observing Systems for Tropical Cyclones
China started applying meteorological satellites to tropical cyclone remote sensing in the 1980s. Satellite information including derived satellite data has been used for tropical cyclone monitoring ever since. This capability enables China to receive, process, and archive satellite data from both home and abroad. However, compared with advanced international standards, China still lags behind in its satellite remote-sensing technologies, data acquisition, and processing. There is still much room for improvement in this area. On the application side, major gaps exist in producing quantitative satellite products to satisfy operational application requirements, and our quantitative applications are rather weak. Problems still exist in the fields of radar data transmission and radar products applications. There are a number of issues to be tackled in AWS data quality control, data collection, etc. In addition, because of the availability of massive tropical cyclone data such as that from the new-generation Doppler radars, lightning positioning systems, GPS/MET observations, wind profilers, a greater stress has been put on the existing communication networks.
CMA's response strategies concerning observation systems are as follows: • Strengthening operational observation by satellites. The second group of two FY-2 satellites will be launched, i.e. FY-2D and FY-2E. The two satellites will maintain continuous operations until 2012, to ensure stable meteorological satellite observations and services. • Accelerating the deployment of a radar network. A nationwide weather radar observation network will be set up, which is based on the S-band and C-band Doppler weather radars as the major components, while other types of weather radars are also interconnected with a view to improving tropical cyclone monitoring.
• Increasing AWS coverage. In order to improve tropical cyclone monitoring, appropriate considerations have been given to increase AWS deployment, particularly in islands (those far away from the coast have a higher priority) and coastal areas of higher tropical cyclone and torrential rain occurrences.

Joint Experiment in Relation to Tropical Cyclones
For some years, the development of observation technologies and the wider application of remote-sensing data have given impetus to operational tropical cyclone forecasting and scientific field experiments on tropical cyclone landfalls at a regional level. At present, outfield tropical cyclone experiments and related research programs on tropical cyclone landfalls are constantly emerging around the globe, including TOST, CBLAST, ATCCIP, DOTSTAR, CLATEX, and the accomplished TCLP. All these experiments lead to further understanding of such characteristics as the tropical cyclone boundary layer in the context of strong wind, changes of meso-scale structure and intensities, etc., which unveils new observations of the inner structure of a tropical cyclone and promotes the development of operational tropical cyclone intensity forecasts during the process of tropical cyclone landfall. However, tropical cyclone field experiments cannot be conducted continuously because of technical reasons or lack of funding. It is, therefore, necessary to strengthen international cooperation in tropical cyclone field experimentation within the region or in a larger area, in order to reveal, as soon as possible, the physical mechanism governing the movement and intensity of tropical cyclones.

The Impact of Climate Change on Tropical Cyclone Activities
At present, there is still no certainty of how global climate change will impact global and regional tropical cyclone activities, but past studies indicate that global warming might reduce, to some extent, tropical cyclone activities globally, while tropical cyclone intensity in the future may become stronger. In recent years, strong tropical cyclones have hit the U.S., Japan, and China more frequently, which, perhaps, is an important signal of the impact of global warming on tropical cyclone activities. Of course, the trend deserves further attention by meteorologists from various countries and needs to be further proven on a scientific basis.

Research on Monitoring and Forecasting Tropical Cyclones
There are a number of difficulties and challenges in theoretical research on operational tropical cyclone forecasts.
For example, an effective method is lacking for forecasting abrupt changes of tropical cyclone motion and speed including abrupt changes in its structure and intensity and the unexpected increase of associated heavy rainfall during the landfall. Future tropical cyclone research should emphasize: • The 3-dimensional inner structure of a tropical cyclone. The evolution of a tropical cyclone is closely related to its structure. With the development of detection technologies such as satellites, radar, etc., more refined meso-scale and small-scale structures inside the tropical cyclone, including the characteristics of the tropical cyclone boundary layer, will be revealed. These will be helpful in improving forecasting capability.
• The mechanism behind the abrupt changes of tropical cyclone tracks and intensities. Several theories have been proposed addressing the abrupt change of tropical cyclone tracks. NWP can also be effective in forecasting unexpected tropical cyclone tracks. Comparatively speaking, it is more difficult to forecast tropical cyclone intensity changes than to predict tropical cyclone tracks. Moreover, intensity changes often lead to abrupt track changes. However, there is little research on the mechanism of abrupt tropical cyclone track changes, and the research in this area should be strengthened.

An Operational Platform for Tropical Cyclone Forecasting
A new-generation tropical cyclone forecasting platform will include the following functions: • Historical Database Retrieval System for accessing meteorological elements and atmospheric fields of tropical cyclones; • Identification of the best track. The best tropical cyclone track will be calculated automatically according to the locations and intensities of the tropical cyclone center defined by various measurements provided by satellite, Dvorak technology, aircraft and dropsonde observations; • Production of tropical cyclone track forecasts. After inputting the best track into the system, the numerical models and an ensemble forecast system should generate tropical cyclone track products.
Then, a final track forecast could be made by combining these results with the forecasters' judgments and experience; • Tropical cyclone intensity forecast. A final intensity forecast could be made on the basis of the tropical cyclone intensity output from the numerical models and relevant statistical models, taking into consideration the factors that affect tropical cyclone intensity as well as the experience of the forecasters; • Warning issuance. An assessment of tropical cyclone-related disasters will be made, and then tropical cyclone warnings will be prepared for dissemination of tropical cyclone warning products and relevant information; • Tropical cyclone warnings standardization and verification.

Risk Management for Tropical Cyclones
The existing tropical cyclone disaster assessment and decision-making systems are inadequate in terms of the Data Science Journal, Volume 6, Supplement, 13 October 2007 S734 timely reception of complete information about disasters related to tropical cyclones. The assessment of tropical cyclone disasters is often undertaken long after the event has taken place. Disaster information via satellite has not been analyzed and utilized in a timely fashion. Therefore, decision-making authorities cannot be well informed with timely disaster information about the affected areas, which are badly needed for taking proper and effective mitigation measures to reduce the loss of lives and properties. On the other hand, the current disaster assessment methods seem to be too simple and primitive. Therefore, assessment for disasters related to tropical cyclones should be further enhanced in order to improve disaster risk management. Moreover, the emergency preparedness and response system for tropical cyclone disasters as well as the relevant data exchange networks should be strengthened in order to provide improved forecasting and services. Meteorological establishments at all levels in China will enhance the disaster assessments and fully demonstrate our professional and technological capabilities to better incorporate meteorological investigations and assessments on high-impact disasters into the governments' natural disaster prevention and mitigation system, according to the Meteorological Law of the People's Republic of China.
The risk management and assessment system for disasters related to tropical cyclones should include the following: • Research on tropical cyclone behavior; • Analysis of the capacities of prevention and mitigation against disasters in populated, economically developed areas; • Development of a disaster information database; • Research on disaster damage assessment methodology; • Comprehensive assessment of the multi-disasters induced by tropical cyclones; • Verification of the usefulness of forecasting; • Response strategies for disaster prevention and mitigation.

Early Warning System for Tropical Cyclones
The current operational tropical cyclones forewarning system will be further improved, and timely and user friendly modern warning and forecasting services will be developed, in order to provide governments and relevant authorities at all levels and the general public with tropical cyclone forecasts and information about associated disasters including response strategy services. Guided by the concept of "public meteorology, security-oriented meteorology, and natural resource-oriented meteorology," the CMA will meet the evolving demands of socio-economic development on a public meteorological service, and it will expand the coverage of meteorological early warnings, establish interactions with the agencies such as water resources, civil aviation, land resources, agriculture, construction, safety supervision, and media improve the coordinated emergency response mechanism, and incorporate the meteorological service into the government's public service system.

Public Awareness of Disaster Preparedness and Mitigation
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The increasing public awareness of preparedness and mitigation of disasters related to tropical cyclones should include the following: • Professional training; • Management training; • Outreach and education to increase public awareness.
Public awareness and knowledge about combating tropical cyclone-induced disasters and the public's active participation in preventing and combating these disasters are key components of disaster preparedness and mitigation. However, insufficient knowledge about tropical cyclone disasters and a small sense of participation often serve as a bottleneck that restricts effective efforts in preventing and mitigating tropical cyclone-induced disasters.

International Cooperation
The relationship among international organizations, such as WMO, the WMO/ESCAP Typhoon Committee, and WMO/ESCAP Panel on Tropical Cyclones, the government and its administrative departments, education and research institutions, monitoring, forecasting, and warning operative departments of tropical cyclones must be enhanced, and effective regional cooperation and exchange mechanisms for monitoring, forecasting, and warning technology and measurements to mitigate the disasters of tropical cyclones must be established.