Air-Quality Management and Weather Prediction during the 2008 Beijing Olympics

by Jianjie Wang¹, Xiaoye Zhang², Tom Keenan³ and Yihong Duan⁴

Introduction

The 29th Olympiad took place from 8 to 24 August 2008 in Beijing. More than 10 000 athletes from 204 countries, territories or regions participated. It was historically exceptional in terms of its size, variety of sport events, variety of Olympic-related activities, operations of municipal infrastructure and daily activities of the general public. Over 1.7 million volunteers provided a full range of services. Analysis of the historical meteorological data shows that the olympic sites in late summer are exposed to significant risks from thunderstorm activity with heavy rain, lightning, high winds and hail. Fair weather also poses challenges such as fog, haze, heat and stable conditions. These are less conducive to the dispersion of air pollutants, which can result in poor air quality.

The meteorological services therefore faced significant challenges in minimizing the negative impacts of detrimental events. Multiple weather-related challenges and air quality had to be addressed for the Games to be successful. An unprecedented variety of air-quality management, monitoring and weather prediction solutions were undertaken by China and international partners. 

A successful and efficient Olympic Games therefore required that multiple weather-related challenges and air quality be addressed so that the negative impacts of detrimental events could be minimized. This article describes the unprecedented variety of air-quality management, monitoring and weather prediction solutions undertaken by China and its international partners that enabled the Olympic and Paralympics Games to be successful.

Air quality management and measurements

Temporary emission reduction regulations were taken by Beijing Municipal Government (BMG) to ensure the normal operation of traffic within the city to ensure good air quality during the Olympic and Paralympic Games and to fulfill the commitment to host the Games. As part of the air-quality management about 300 000 “yellow-tag” vehicles were banned from roads in Beijing from 1 July to 20 September 2008 (two days after the conclusion of the 2008 Paralympics) and all construction activities were stopped. In addition, traffic was reduced by requiring that all the vehicles from other provinces, regions, municipalities with license plates ending in odd (even) numbers would be allowed on the road on odd-(even-) numbered calendar days during the same period. During the Games period, additional emission reduction measures that focused mainly on coal combustion were taken.

From June to September 2008, the China Meteorological Administration (CMA) conducted a continuous, extensive online monitoring and analysis campaign that supported the logistics of the Games but also allowed for a unique assessment of the effects of the efforts to improve air quality (Zhang et al., 2008). The monitoring exercise tracked concentrations of PM₁₀ and PM_2.5, including aerosol fractions of organics, sulphate, nitrate and ammonium in PM₁, aerosol optical depth, ozone and other reactive gases, including nitric oxide, nitrogen dioxide, nitrogen oxide, carbon and sulphur dioxide. Ground-based monitoring was reinforced with measurements of aerosol optical depth and column nitrogen dioxide by satellite retrieval and the analysis of weather processes and characteristics. The monitoring was conducted at three urban stations at different heights (i.e. CMA, 20 m, Baolian, 3 m and the Observatory at Nanjiao, 3 m) and at four other rural stations (i.e. Gucheng station in Hebei Province, 100 km south-west of Beijing; Shangdianzi station in Miyun county, 150 km northeast of Beijing; Huimin station in Shandong Province and Yushe station in Shanxi Province). 

During the period of the Games, various atmospheric pollutants decreased dramatically in Beijing. Analysis showed that this decrease was related not only to the implementation of control measures but was also strongly linked to the weather. Specifically the sub-tropical high was located to the south so that Beijing’s weather was dominated by the interaction of a frequently eastward-shifting trough in the westerlies and a cold continental high with clear-to-cloudy days or showery weather. After removing estimates of the change in concentrations from weather conditions, analysis that the removal of ~300 000 “yellow-tags” after 1 July 2008 led to the following results:

• Reductions in various reactive gas concentrations linked with motor vehicle activities dropped by ~40 per cent;
• Reductions in PM10 particle concentrations by approximately 15-25 per cent;
• The concentration of traffic-related black carbon concentration decreased by ~25-30 per cent;
• The concentration of particle organics and nitrate was reduced by some 25-40 per cent.

The ammonium product and sulphate, which are not closely related to vehicle activities, did not significantly change, while the hour concentration of ozone moderately increased. In the same period, sulphur dioxide concentrations over Beijing also decreased somewhat, due to coal-combustion control measures. The concentration of its transformed product, sulphate aerosol, had almost no change, indicating that contributions came from surrounding pollution sources.

Various reactive gas concentrations closely linked to motor vehicle activities decreased by an additional ~15-20 per cent with the introduction of odd-even motor vehicle restriction guidelines after 20 July 2008. While the overall PM10 particle concentrations increased a little, due to the motor vehicle restriction, black carbon, particle organics and nitrate were reduced by between 6-20 per cent. Ammonium product and sulphate, however, rose by ~10 per cent and ozone concentration increased by 30 per cent. The differences between the variations were meteorological in nature as stable weather conditions prevailed with the local formation and subsequent regional transport of secondary aerosols to Beijing. The aerosol optical depths observed at Beijing by ground-based remote-sensing, as well as the optical depth and total nitrogen dioxide column derived from satellite retrieval, were similar. It was found that water vapour had obvious effects on aerosol optical depth and atmospheric visibility under the stable, but fewer, aerosol days, which could give a false impression of poor air quality.

PM10, visibility and ozone forecasting

Before and during the Games, CMA provided two-day forecasts of PM10, visibility and ozone to BMG and subsequently to Beijing Meteorological Bureau (BMB) and Beijing Municipal Environmental Protection Bureau (BMEPB). The forecasters used the Chinese Unified Atmospheric Chemistry Environment for dust (CUACE)/haze/ozone forecasting system, which is a unified atmospheric chemistry and environment modelling system that can be easily coupled with different types of weather and climate models at various temporal and spatial scales. For this application, CUACE was fully coupled with the MM5 prediction model with a horizontal resolution of 54 km over Asia and the eastern part of Europe.

The initial and boundary conditions were from the CMA operational global medium-range prediction model. The CUACE model comprised a chemistry module for gases, gas-to-particle conversions, secondary organic aerosols and aerosols. The gas component in CUACE has 21 photochemical reactions by which 66 gas species for ozone, nitrogen oxide, sulphur dioxide, ammonia, carbon dioxide and volatile organic compounds can be simulated. The aerosol part in CUACE is a size-segregated multi-component module for seven types of aerosols such as dust, sea salt, black carbon/organic carbon, sulphate, nitrate and ammonium. It also contains major aerosol processes in the atmosphere such as generation, hygroscopic growth, coagulation, nucleation, condensation, dry depositions, scavenging and aerosol activations. A number of improvements to the model were undertaken to improve the chemistry forecasts such as improvements in the advection scheme for all tracers and the inclusion of a non-local vertical diffusion scheme. The aerosol thermodynamic model ISORROPIA was also introduced to calculate the composition and phase state of an ammonia-sulphate-nitrate-chloride-sodium-water inorganic aerosol in thermodynamic equilibrium with gas-phase precursors.

On the basis of a China regional emission inventory from Cao (2006), CUACE ran in real-time from 1 July to 30 September. Two-day products in 12-h mean and 2-h intervals of PM10, ozone and visibility for Beijing were provided everyday as forecast guidance to BMB and BMEPB. Figure 1 shows an example of the products. CMA also conducted and provided BMB and BMEPB with three-to seven-day forecasts of stabilized weather condition forecasts based on a parameter linking air quality and meteorology (Plam) index. This index links air quality and meteorology and is derived from the relationship of PM10 and key meteorological data derived on the basis of summer data from Beijing and its surrounding areas over the 2000-2007 period. The meteorological data include air temperature, relative humidity, wind, air pressure, visibility, clouds, evaporation, air stability and some history of weather phenomena of the preceding days. Higher Plam indices and poor air quality (>150 µg/m3 PM10) were always associated with high temperature, high humidity, lower wind speed and stable weather. An example of the use of the Plam index is shown in Figure 1. Each site outside Beijing is given a Plam weight according to the wind and speed direction relative to the arrival of the airmass in Beijing. The higher Plam value at a site in Beijing’s surrounding areas in Figure 1 shows that weather conditions in these areas would be more favourable for pollutant transport to Beijing.

Figure 1 — 12-or 24-h forecast guidance of surface PM10, visibility and ozone as well as Plam index for Beijing and its surrounding areas by CUACE of the Centre for Atmosphere Watch and Services, CMA, starting at 08 BTC, 24 July 2008

Demonstration projects of the WMO World Weather Research Programme

Under the guidance of CMA, the Beijing Olympic Meteorological Service Centre (BOMSC) successfully provided “characteristic and high-level” meteorological services, based on the Beijing Olympic Games-oriented operational refined weather forecasting and warning system and man-machine interactive platforms. In a preliminary assessment, the meteorological services that were provided in this complex and meteorologically challenging environment attained a public satisfaction of 93.1 per cent. These capabilities were developed and tested well in advance, through substantial innovation by mobilizing national meteorological expertise and resources and through effective international cooperation. The WMO World Weather Research Programme (WWRP) demonstration projects are two examples of this international collaboration.

Beijing 2008 Olympic and Paralympic Games Project

In order to take advantage of a WMO/World Weather Research Programme project for the 2000 Sydney Olympic Games, CMA formulated plans in 2003 for a Forecast Demonstration Project (FDP) and a Research and Development Project (RDP) to assist in the technical support for weather forecasting and services for the Beijing 2008 Olympic and Paralympic Games (B08) project. In October 2004, the B08 project was formally endorsed by the 7th meeting of the Scientific Steering Committee of WMO WWRP, which was led by CMA with participants from Australia, Austria, Canada, China, Hong Kong (China), France, Japan and the USA. The B08 project included sub-projects as the nowcasting demonstration (B08FDP) and the mesoscale ensemble forecasting project (B08RDP).

Implementation of the B08 project

Implementation of B08FDP

The overall mission of B08FDP was to demonstrate and quantify the benefits of an end-to-end nowcast (predictions in the 0-6h range, especially in 0-2h time-frame) weather service, focusing on the prediction of high-impact weather using the latest science and technology. B08FDP was targeted on the development, application and field demonstration of nowcasting systems for local convective storms, the use of products from these systems in operational forecasting and assessments of socio-economic benefits to end-users. Eight nowcasting systems participated: BJ-ANC jointly developed by the BMB and the US National Center for Atmospheric Research (NCAR); CARDS of the Meteorological Service of Canada; GRAPES-SWIFT of the Chinese Academy of Meteorological Sciences of CMA; STEPS and TIFS of the Australian Bureau of Meteorology (BOM); SWIRLS of the Hong Kong Observatory; NIWOT of NCAR and MAPEL, jointly developed by McGill University of Canada and WDT of the USA.

The B08FDP was a 3 1/2 year effort with two trials in the summers of 2006 and 2007 to improve systems and optimize individual algorithms on storm extrapolation, quantitative precipitation estimation, product generation and other tasks. The field trials also enabled the systems to adapt to local data, computation and network environment. A real-time forecasting verification system was developed by BOM and also transferred to BMB. By mid-July 2008, all these systems met the demonstration requirements and were finalized and frozen to ingest and process, on a real-time basis, the multivariate and highly frequent local observational data (see Table 1) and to generate products for prediction (See Table 1) and real-time verification.

Table 1 — Data provided to B08FDP in the summer of 2008 by the Beijing Meteorological Bureau

Three international workshops and a number of meetings and telephone conferences were held to diagnose the technical difficulties encountered during the different implementation stages and to explore solutions, identify responsible working groups and discuss roadmaps and timelines for major activities. Key technical issues included radar data quality control, radar synchronization, 3-D mosaic of radar raw data and the transfer of research into operations. Two training workshops were held in Beijing in April 2007 and July 2008 to train local experts and weather forecasters to enhance local support to the B08FDP systems, especially local application of products by a panel of experts. Some end-users participated in activities as trainees.

Table 2 — The B08FDP products

Implementation of B08RDP

B08RDP focused on short-term (6-36 h) predictions through the development and utilization of the high-resolution (15 km) limited-area short-range ensemble prediction systems by six different participants (the US National Center for Environment Prediction and NCAR; Environment Canada, Japan Meteorological Agency; Zentralanstalt für Meteorologie und Geodynamik of Austria, MeteoFrance and CMA). A common framework was set up in which the six participants ran their computer models remotely in their own institutions with the same computation configuration covering Beijing and surrounding area. The observation data and ensemble member data were transmitted through ftp-server in real-time, with unified resolution and area location, unified data format and filename, and GRIB2 encoding/decoding standard as TIGGE-LAM defined was used. Collaboration among the participants contributed to the advancement in basic knowledge and new forecasting techniques, and to the improvement of ensemble prediction systems. Table 3 shows the characteristics of the six participating systems.

From 2006 to 2008, all participant systems ran in real-or near-real-time in the summer season and the predictions were compared and analysed. At the CMA National Meteorological Centre (NMC) and National Meteorological Information Centre, a system was set up to fulfil the tasks of observation and ensemble prediction data transmission, data encoding/decoding, verification, bias correction and product generation, based on multi-source ensemble prediction data and product display, etc. Most ensemble products were distributed to the NMC and BMB as guidance for forecasters. The RDP also emphasized the real-time demonstration, evaluation and intercomparison of modelling activities that typically lie in the research community (e.g. multi-centre probabilistic products for the high-impact weather, high-resolution cloud-resolving model (about 2-4 km) for severe weather events).

Table 3 — The B08RDP limited area ensemble prediction system in the summer of 2008

To ensure effective application of ensemble products, the NMC focused on training national-and province-level forecasters in their daily weather forecast duty over the past several years. Liaison between B08RDP and FDP was set up, and product requirements were investigated from experts and user groups to meet the needs of the Olympic weather service. The products included the mean/spread/probability of surface elements, the uncertainties of circulations and the special products associated with high-impact weather. Moreover, probability products for Olympic venues were developed.

B08 Demonstration

The role of B08FDP

The B08FDP demonstration period for the aforementioned eight nowcasting and the real-time forecasting verification system took place from 20 July to 20 September 2008. Thirteen experts from Australia, Canada, Hong Kong (China) and the USA worked at BMB during the enhanced B08FDP demonstration period (1-24 August). All B08FDP systems provided a subset of the nowcasting guidance products referred to in Table 1 every six minutes.

To make the support to operations more organized, an B08FDP expert and two local experts were responsible for:

• Organizing analyses and discussions on the weather and nowcasting products within the B08FDP group;
• Preparing the concise texts describing the dominant circulation patterns and weather systems, as well as potential impacts on the Beijing area in general, and on sporting venues in particular;
• Interpreting B08FDP products for local forecasters; and
• Participating on behalf of the B08FDP group in the two daily BOMSC weather discussions.

In the case of an important service or a complex weather event, the B08FDP experts and local experts would participate in exchanges with forecasters and the weather discussions in the enhanced monitoring period more frequently. In the days of the opening and closing ceremonies of the Olympics, B08FDP experts worked together with BMB forecasters to track the variations of weather systems continuously until the end of these events.

Three approaches were designed to allow weather forecasters and on-site weather service teams to directly access B08FDP products and verification outcomes in a user-friendly manner in order to ensure the application of B08FDP products in the efforts of the operational meteorological services:

• A B08FDP Webpage in English and Chinese was developed on the BMB internal Website, dedicated to forecasters and on-site service teams for the B08FDP products (see Table 1);
• A subset of the B08FDP products was put into the man-machine interactive platform in the BMB operational nowcasting procedures for direct use as nowcasting guidance by forecasters;
• Local experts provided forecasters with B08FDP printouts and oral interpretations of products and expert interpretation. In addition, for other end-users (e.g. Beijing Organizing Committee for the Olympic Games (BOCOG)), civil aviation meteorological departments, the boating service unit of the Summer Palace), the Beijing Olympic Meteorological Service Website in Chinese and English was opened to access and browse the B08FDP products by Internet. This was also the approach for the general public to obtain B08FDP products and other meteorological information during the Games.

The role of B08RDP

The real-time B08RDP demonstration period was from 1 July to 24 September 2008. To ensure the practical application of B08RDP ensemble products in the Olympic meteorological services, especially during high-impact weather events, NMC designed several approaches to ensure the direct access of weather forecasters and B08RDP participants to B08RDP ensemble products, observations and analysis fields. First, ensemble products were categorized and translated into different data formats for different end-users or display purposes. Second, the B08RDP Webpage was developed in the NMC internal Website to ensure access by all forecasters from BMB/NMC and B08RDP participants in real-time. Third, partial B08RDP ensemble products developed for the 17 Olympic venues were transmitted to BMB by a high-speed dedicated cable network between CMA and BMB. This allowed close collaboration between the RDP and FDP nowcasting applications.

During the Olympics, CMA B08RDP experts also worked closely with Central Weather Observatory forecasters by transmitting and interpreting ensemble predictions and providing weather forecasting suggestions from the prospective of research. The advantage of ensemble forecasts was to characterize the uncertainties in the predictions, which was especially useful for a better understanding and improved forecasting of high-impact weather events through comparison with single, deterministic forecasts. The B098FDP project was proactive and effective in supporting the nowcasting services during the Beijing Olympics by providing plentiful and useful quantitative guidance on the one hand and offering the expertise, knowledge and analytic methodologies on the other.

Weather forecasting and services

Forecasting and service bodies

The Beijing 2008 Olympic Games involved the host city and six co-host cities (Qingdao for sailing; Hong Kong for equestrian events; Tianjin, Qinhuangdao, Shenyang and Shanghai for football). With the approval of CMA and BMG, the Beijing Olympic Meteorological Service Centre was established as the only meteorological service provider in August 2006, with full authorization to fulfil the tasks and mandates for providing various meteorological services to the Beijing Olympics (TOK, 2008). Its organizational structure is given in Figure 2.

Figure 2 — Organizational structure of the Beijing Olympic Meteorological Service Centre

BOMSC comprised three components: meteorological services of the host and co-host cities and the venue weather offices. Some national operational meteorological centres and research institutions within the CMA framework and six temporary meteorological service bodies were created in Beijing, Qingdao and Hong Kong to support outdoor sporting events and major public gatherings. The meteorological services of the host and co-host cities were to provide weather forecasts and services to the local Olympic sport organizing committees and local organizers for major public activities, whereas the national operational centres and research institutions were tasked with providing technical guidance and support to the meteorological offices in the host and co-host cities, apart from Hong Kong Observatory, which had full responsibility to provide weather forecasts and services for equestrian events. All relevant data and products received by the dedicated Beijing Olympic Information system (INFO2008) (i.e. in situ meteorological observations made at all venues in the host and co-host cities, refined weather forecasts, nowcasts and early warnings) were collected and converted into a unified format by BMB and then disseminated to the BOCOG.

Through a nationwide selective process, well in advance, CMA had seconded some experienced forecasters and service staff to the BOMSC to strengthen its weather forecasting and service teams directly involved in front-line services at both Beijing and Qingdao sport venues. Some senior Chinese and foreign meteorologists and experts were invited to share their experience with forecasters and to participate in activities during the Olympics. Altogether, 79 front-line forecasters, including service-delivery staff, 61 technicians, 32 operational management staff and 15 overseas experts (including 13 from B08FDP) were directly involved in the Olympic meteorological services. Of these, 40, 25, 15 and 15, respectively, were in support to the meteorological services in BMB.

The core weather forecasting and service delivery systems

The special demands for highly advanced meteorological services by the Olympic sport events and related large social events exceeded the range of routine weather forecasts and operational services in many aspects. To address this issue, BMB, in association with other meteorological services, focused on research and the development of new techniques, methodologies and tools to make the advanced forecasts of weather elements at specific venues, nowcasts and early warnings of local severe convective weather (Wang, 2007). The following “four systems and two interactive tools” were established for the Games by BMB:

The Hi-MAPS system was able to pre-process a wide range of highly frequent observations in a rapid update manner (e.g. six-minute radar volume scanning raw data, six-minute wind profiles, five-minute automatic weather station observations, 6-h enhanced radiosonde observations, etc.). Hi-MAPS provided observation data for the BMB operating systems and provided standard data for the eight B08FDP demonstration systems on a real-time basis;

The BJ-ANC system was developed jointly with NCAR. It produced severe convective weather nowcasts based mainly on multiple Doppler radar observations with more complex extrapolation techniques. BJ-ANC also incorporated other algorithms, such as the variational Doppler radar analysis system and radar quantitative precipitation estimation and prediction algorithms. The system generates much nowcasting guidance (see Table 2);

The BJ-RUC system was developed jointly with NCAR. It is the local version of the NCAR mesoscale Weather Research and Forecasting system with a number of improvements, e.g. development of a 3-D variation data-assimilation scheme for local meteorological data (multi-elements, automatic weather station observations and ground-based GPS-meteorological data), adjustment of co-variance error in the model background field and digital filtering scheme. With a rapid cycle every three hours, it provided a high-resolution (3 km) mesoscale numerical output covering Beijing and the surrounding area for the following 24 or 36 hours as refined forecast guidance;

The OFIS system was a man-computer interactive tool to facilitate the analysis of weather conditions and the production of three-hourly forecasts of refined weather elements over the following three days (0-63 h) based on a variety of observations, numerical weather prediction (NWP) products and venue forecast guidance as well as real-time verification of guidance. The venue forecast guidance derived mainly from:

• Multi-element, venue-specific forecasts by the support vector machine regression method, a statistic interpretation of NWP products;
• Multi-element venue-specific forecasts by half periodic function fit methods, based on the chief forecaster’s conclusions for 12-hourly forecasts for the following three days;
• The VIPS system was a man-machine interactive tool to assist forecasters in monitoring severe convective weather and producing early warnings in the Beijing area. A variety of high-frequency mesoscale meteorological observations and NWP products, as well as nowcasting guidance (e.g. outputs from Hi-MAPS, BJ-RUC, BJ-ANC and B08FDP nowcasting systems) and geographic information, could be superimposed on one screen. It also supported early warning mapping and screen-revision functions and automatically generated warning texts in both Chinese and English with an editing function.

The OMIS system had multiple functions. It collected real-time observations and venue-specific weather forecasts in Beijing and co-host cities and automatically decoded, converting data format and unit of measurements, translating into the target languages, classifying and packaging for different users in different form of products and distributing to BOCOG, Beijing Olympics INFO2008 system, Beijing Olympic Broadcasting and Olympic Meteorological Service Website in real-time.

The weather and services

There was more rainfall than normal in Beijing during the Olympic Games. The accumulated precipitation (8-24 August) was 151.7 mm in the plain area of Beijing, 90 per cent higher than the same period of the 30-year average (80 mm). There were four widespread precipitation events across Beijing and another four local precipitation events in Beijing, of which five individual days had 10 mm of daily precipitation. On 10-11 August, the city witnessed heavy storms and rainfall. High-impact weather other than precipitation was less than normal.

In the face of complex and changeable weather, BOMSC paid special attention to some key components in its service delivery:

• Enhancing weather “consultation”
  Special discussions were organized for important events (i.e. opening and closing ceremonies and weather-sensitive outdoor events), in which senior forecasters and experts, as well as foreign nowcasting experts, were invited to participate;
• Making good use of advanced technologies
  The “four systems and two interactive tools” were incorporated into early warning and refined forecast processes to tap the human potential for improving efficiency and quality based on high technologies;
• Enhancing interactions with venues
  The simplified VIPS version was installed at on-site weather offices so that venue service teams could access updated observations, forecasts and early warnings and enable them to interact in a timely manner with end users. At the same time, information communication channels allowed staff on-site and at head office to accommodate the changes in users’ demands and to provide relevant and tailored services at any time.

With the benefit of these initiatives, focusing on the characteristics of outdoor events, BOMSC provided BOCOG with “characteristic and high-level” refined forecasts and early-warning services, which helped the organizers accurately arrange the timing of a number of competitive events. The Olympic Schedule Committee called for six telephone conferences and made schedule changes for eight sports events according to the weather forecasts delivered by BOMSC. Despite more rainfall than normal, accurate and timely short-term forecasts and nowcasts, as well as continuous follow-up services, ensured the smooth running of the majority of outdoor events. Only a few were interrupted because of unexpected rainfall.

All events were completed on schedule and with high quality. For example, the competition command group was informed of the rainfall on 10 August 48 hours in advance and it rained in the 08:00-09:00 time slot on the day as forecast, delaying the first tennis match, which was originally scheduled for 10:00. Based on the evolution of weather systems, the tennis event organizers were informed ~11:30 on 10 August that there would be no rain between 12:30 and 16:00 so that the event was able to start shortly after. In another example, BOMSC forecast that there would be more rainfall before 09:00 on 21 August, but would lessen after 09:00. The International Association of Athletics Federations decided that the women’s 20-km walk and decathlon would be held on time, but that the high jump and javelin would be postponed for one hour.

Forecast products and performances

From the check-in of the athletes at the Olympic Village to the end of the Paralympic Games, BOMSC issued and distributed a total of more than 10 000 copies of weather forecasts, reports, briefings and warnings in 18 categories in Chinese, English and French (Table 3); 58 985 files in XML format were transmitted through Info2008; 7 211 graphic files were sent for large screen display at the main operation centre of BOCOG; 9 240 satellite and radar images were provided to Beijing Olympic Broadcasting. At the same time, more meteorological information than ever before was issued to the general public through television, radio, Websites, telephone, newspapers, mobile SMS and other means and also weather information in English was made available. The Olympic Meteorological Service Website (www.weather2008.cn), established by BOMSC, had a link to the BOCOG official Website, and there were 15 126 795 visits.

Table 4 — Weather forecast and severe weather warning issued by BOMSC from 25 July to 17 September 2008

Preliminary verification on the three-hourly weather forecasts for the next 63 h targeted to the venues in Beijing showed that:

• Forecasters largely depended on the guidance provided; they could make merit-based judgments and amendments;
• The quantitative precipitation forecast is the most difficult one in forecast elements, especially when it relates to specific location and time;
• Forecasters’ skills in temperature, relative humidity and wind speed were slightly better than forecast guidance, but their skills in precipitation and wind direction were more or less equivalent to the guidance on average;
• The accuracy rate of three-hourly relative humidity forecasts issued by forecasters, with bias less than 10 per cent against observation, is about 70 per cent within 24 h, 65 per cent in 24 h-48 h, and 55 per cent beyond 48 h. The mean absolute error of three-hourly temperature forecasts is about 1.7°C within 24 h, 2.0°C in 24 h-48 h, and 2.2°C beyond 48 h (see Figures 4 and 5);
• Comparing the performance of venue three-hourly precipitation forecasts using the threat score (TS), forecasters had higher skill than support vector machine guidance, but the skill decreases with the valid time (TS around 0.1-0.2 within 24 h, and 0.07-0.13 in 24 h-63 h against TS of support vector machine guidance less than 0.1 in 0-63 h). It is noticeable that TS of three-hourly venue rainfall guidance within 24 h valid time from BJ-RUC had the highest TS among the three. However, its unstable performance from different runs during the daily cycle did not give much confidence to forecasters to rely on it more during the period of Beijing Olympics.

Figure 3 — Forecast accuracy rate of relative humidity (bias<10 per cent) (statistics based on the data of 8-24 August 2008)

Figure 4 — Mean absolute error of temperature (°C, statistics based on data of 8-24 August 2008)

Responses to a satisfaction survey showed that users (BOCOG affiliates, the opening and closing ceremony operators, Shunyi water sports teams, the National Stadium, and city operation teams, city officials, sport event organizers, referees, athletes, volunteers and the general public) believed that the forecasts delivered by BOMSC were accurate, timely and effective with a public satisfaction rate of 93.1 per cent.

Conclusions

The successful, extensive and complex set of activities to support air quality and weather during the Olympic and Paralympic Games will have a lasting effect on both China and the international community.

The monitoring campaign illustrated the large concentration decreases of traffic-related gases and aerosols from traffic restrictions, but the sulphate, ammonium and particulate matter changed during the control stages and the ozone concentration moderately increased. The “yellow-tag vehicle ban” measure had a larger effect on the reduction of the atmospheric composition than the alternating registration plate restrictions. Several recommendations were made to BMG for understanding and improving air quality on the basis of these findings and other urban areas throughout the world could benefit from this knowledge.

The BOMSC provided effective and quality weather services in the context of more rainfall than normal, which were recognized by all walks of life. The success was due to the use of advanced technologies and techniques, the “human” role, close interactions with end-users, implantation of B08 demonstration projects and the unique working and management measures.

The B08FDP demonstration proved to be very supportive to the Beijing Olympic nowcasting services by providing guidance, but also through a highly interactive approach with experts, forecasters and knowledge delivery. B08FDP was a successful example of combining research findings with operational applications and the model here should be followed in developing enhanced nowcasting support elsewhere.

B08RDP furthered knowledge of the use of multi-centre ensembles and characterizing uncertainty. The bias-corrected and combination products of the multimodel ensemble were superior to any single ensemble so that benefit can be obtained from the real-time utilization of probabilistic products for severe weather. However, the paradigm shift of a forecast office from deterministic to ensemble prediction is challenging, even after careful training.

The Olympic Meteorological Service provided a practical opportunity for forecasters to produce refined weather forecasts. However, refined forecasting is a new and challenging task for forecasters, whose previous experiences in conventional forecasts are not necessarily applicable. At present, skills of forecasters for making refined forecasts slightly outperform the objective prediction methods, but there will be much room for forecasters to play a value-added role in refined forecasts by continuous and cumulative learning from experience.

The activities for the Olympic and Paralympic Games were extensive and a great deal of the success lies in the long-term multi-year planning for all aspects of the effort and the commitment of the international partners and local hosts.

Acknowledgements

The authors wish to thank all participants in B08FDP/RDP for their contributions to the success of the project and their outstanding performance in supporting the meteorological services to the 2008 Beijing Olympics. F. Liang, S.Y. Shi, D.B. Su, H. Guo, and X.Q. Ma helped in making the figures and tables.

References

Wang, J. J., 2007: Refined forecasts for the weather service to 2008 Beijing Olympics, paper for Annual Workshop of China Meteorological Society, December 2007 (in Chinese).

CMA, 2008: Transfer of Knowledge (TOK), Functional Area Report—Meteorological Service.

Zhang, X.Y., Y.Q. Wang, X.C. Zhang, T. Niu, S.L, Gong, P. Zhao, J.L. Jin and M. Yu, 2008: Aerosol monitoring at multiple locations in China: contributions of EC and dust to aerosol light absorption. Tellus B 60B, 647-656.

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¹ Beijing Meteorological Bureau, China Meteorological Administration, Beijing
² China Academy of Meteorological Sciences, China Meteorological Administration, Beijing
³ Bureau of Meteorology Research Center, Bureau of Meteorology, Melbourne, Australia
⁴ National Meteorological Center, China Meteorological Administration, Beijing