应用气象学报

Observational Study on Characteristics of Meteorological Elements in Mountain Qomolangma Region

He Lifu, Wang Suichan, Zhang Zhigang

2010, 21(6): 641-648.

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Abstract:
The Qomolangma Olympic torch relay meteorological guarantee team of the Central Meteorological Office has obtained precious first hand observational data, including in situ data of automatic station and 79 sounding data in the Qomolangma's base camp from 12 April to 8 May in 2007. Observational characteristics of meteorological elements in Mountain Qomolangma are revealed in terms of these data and the results are as follows. Due to the effect of glacier wind in Rongbuk Valley, the prevalent wind is a downslope wind (south wind) in the Qomolangma's base camp. The diurnal changes of wind speed and temperature show single peak type distribution, with the minimum appearing at 08:00 and the maximum at 15:00. Relative humidity peaks appear at 07:00 and 23:00, the minimum at noon. There is a constant south wind below 6200 meter elevation, and the strongest downslope wind happens during 22:00-00:00. West wind is dominant for 7200-9000 meters, and its speed increases significantly with the elevation. At the height of 5200-8000 meters, the temperature always reaches minimum at 08:00 and maximum at 16:00, but the temperature diurnal change shows more fluctuations above 8200 meters. The high value centers of relative humidity can maintain at an elevation of 6700-9700 meters, and the highest value areas locate mainly in 6500-8800 meters. From late April to early May, the high level frontal zone in the Everest area is at the elevation of 12000-15000 meters, and troposphere top height is around 18200 meters. Rising temperature, pressure and decreasing wind speed offer ideal time window for climbing the mountain.

Climate Characteristics of Moisture Budget in Humid Region Affected by East Asian Monsoon

Liao Rongwei, Zhao Ping

2010, 21(6): 649-658.

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Abstract:
Based on 1958—2007 NCEP/NCAR reanalysis data, the characteristics of moisture budget in humid region affected by East Asian Monsoon are calculated by moisture transport, moisture flux divergence and P-E methods. The correlation coefficients of climatological variability calculated by these methods are 0.91, 0.71, 0.81, and the percentage of ε are 17.4%, 44.1% and 44%. The results calculated by moisture transport and moisture flux divergence methods are nearly the same. The results reveal net income of moisture budget thoughout the year especially in spring and summer, while in winter and autumn it's relatively weaker. Using moisture flux divergence and P-E methods, the absolute errors in summer are larger than in other seasons. In spring and summer, water transport and moisture flux divergence are both stronger than those in autumn and winter. For the meridional moisture transport, moisture enters this area mainly from south boundary. For the zonal moisture transport, moisture enters through west boundary and departs from east boundary all the year. Overall, the period of positive moisture budget is from February to October calculated by moisture transport method, and from February to September by the other two methods. Vertical distribution of moisture budget is calculated by moisture transport method and moisture flux divergence method. It shows that the anomaly transport between 800—500 hPa is positive during 1960s and early 1970s and negative after that. Below 800 hPa, the values manifest negative before 1960s, and then turn to positive. There is net income of moisture at the whole layer except for the 850 hPa. By moisture flux divergence method, the calculated moisture convergence is positive above 450 hPa, and negative below. The interannual moisture budget variability of four seasons is quite obvious.

Assessing the Extended Range Forecast Error of NCEP/CFS in the Summer of East Asia

Chen Guanjun, Wei Fengying, Gong Yuanfa

2010, 21(6): 659-670.

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Abstract:
Regional and persistent heavy rain in the southern parts of China can lead to severe flooding, and abnormality of key circulation system in East Asia is the most important inducement for the abnormal precipitation in target area. Furthermore, the low frequency oscillation (LFO) has special impact on the extended range forecast of general circulation. By use of fully coupled retrospective forecasts covering a 24 year period (1981—2004) provided by NCEP Climate Forecast System (CFS), the 1 to 30 days predictive skill and errors between forecast and observations (NCEP/DOE Atmospheric Model Intercomparison Project (AMIP) Ⅱ Reanalysis) are diagnosed and the predictive skill of three typical cases of persistent heavy rain, in the Yangtze Huaihe River Valley, the southern parts to the Yangtze River and South China are examined respectively. The influence of LFO on extended range forecast skill is revealed.The forecast skill of 200 hPa, 500 hPa and 850 hPa heights is obtained, by calculating the anomaly correlation coefficient (ACC) between predicted and observed fields over a typical region of the East Asia during the summer. Based on the 24 year climatology, the ACC skill maintains greater than 0.6 at a lead time of less than 6 days, which is the average level of current numerical weather prediction models. The ACC drops rapidly with increasing lead time but when it comes to 10—19 days, the ACC is relatively stable and ranges from 0.05 to 0.15. The errors also keep stable at the lead time of more than 10 days with the predicted fields lower than the observations in areas north of 60°N and higher than the observations in areas between 40°N and 60°N.By use of 30—60 days component data which is obtained by Butterworth Band pass Filter, the forecast exhibits more skillful with the ACC to observed 30—60 days component data of about 0.15 at lead time of 15 days.From the typical cases, it's found that the low frequency precipitation with quasi two weeks and 30—60 days fluctuation is an important characteristic of the persistent heavy rain, and the CFS exhibits some useful extended range forecasts skill to the low frequency oscillations of major circulation system which is useful for estimating the main region and intensity of persistent heavy rain. This may provide valuable information for utilizing the numerical products and modeling extended range forecasts.

Variations of Torrential Rain in First Rainy Season in Guangdong Province and Its Relationships with the Biweekly Oscillation of 500 hPa Key Region

Ji Zhongping, Gu Dejun, Wu Naigeng, Xie Jiongguang

2010, 21(6): 671-684.

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Abstract:
In order to improve medium range prediction of torrential rain in Guangdong Province, the variation characteristics of the torrential rain in first rainy season and their relationships with biweekly oscillation of a key region at 500 hPa geopotential height are investigated with wavelet analysis, power spectrum analysis, cross spectrum analysis and Lanczos filter using the daily precipitation data of 86 stations and rainfall regimes, and NCEP/NCAR daily data for the last 48 years of 1961-2008. The results show that torrential rain during June has increased in both the number of days and intensity since the 1990s, but the total number of torrential rain days for the season has decreased since the end of the 1990s, exhibiting significant quasi periodic oscillations of 6—7 years. The storm rainfall accounts for 37.7% of total rainfall during Guangdong first rainy season, and is significantly positive correlated to the total rainfall. The area (20°-30°N, 102.5°-120°E) with 500 hPa geopotential height is significantly negative correlated with the daily precipitation during April-June in Guangdong, named as the 500 hPa key region. The daily precipitation during April-June in Guangdong and 500 hPa key region exhibit significant quasi weekly (5—9 days) and quasi bi weekly (10-20 days) oscillations but less significant 30—60 days oscillations. The relation between 500 hPa key region and the daily precipitation during April—June in Guangdong Province in the quasi biweekly oscillation scale is most close connected, and the lead or lag time of oscillation is within 2 days. From April to June over the 48 years, the probability of torrential rain is 79% within three or four days (in fewer cases) before or after the valleys of the quasi biweekly oscillations in the 500 hPa key region. The characteristics of atmospheric circulation with or without torrential rain in Guangdong Province for quasi biweekly oscillatory valleys of 500 hPa key region are analyzed with the composite analysis of typical examples. When the torrential rain happens near the valleys, the cold air moves southward by significantly enhanced trough over East Asian, meanwhile, trough over the Bay of Bengal significantly deepens and widens, and torrential rain in Guangdong Province are caused by the interaction between north cold air and southwest warm and moist air brought by strong southwest flow from the Bay of Bengal. When no torrential rain happens near the valleys, the cold air acts northward, no significantly transfer of water vapor moisture transport from the Bay of Bengal, Guangdong Province is controlled by strong southwesterly at the verge of subtropical high and is located in the divergent region of moisture flux, the rainfall is weaker. All these are not conducive to the occurrence of rainfall, especially torrential rain. Therefore, the significant difference between the circulation fields can be used as reference for medium range forecast of torrential rain in Guangdong Province.

A Dynamic Approach to Retrieving Snow Depth Based on Integration of Remote Sensing and Observed Data

Zhao Liang, Zhu Yuxiang, Cheng Liang, Wang Chenglin

2010, 21(6): 685-697.

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Abstract:
Both the observed data and remote sensing data have respective different advantages and disadvantages. Based on integration of observed and remote sensing data, a temporal spatial dynamic approach to retrieve snow depth is explored by skillfully combining observation station data in China and brightness temperature (T_b) from the Special Sensor Microwave Imager (SSM/I). The aim is to utilize the dynamic scheme of the statistical relation to overcome the complexity of the physical relation between T_b and snow depth, accordingly, to improve the retrieval precision in marginal regions of snow cover and the regions where there are few observation stations. The dynamic scheme is implemented by the following steps: For the first time, according to the linear relationship between observed snow depth and T_b difference at each station, the retrieval coefficients of all stations at this time can be achieved, which guarantees the coefficients' spatial difference. Second, after reasonable influencing radius decided, by using of Cressman interpolation algorithm, the retrieval coefficients at all grid points at this time can be obtained, which guarantees the coefficients' spatial continuity. Third, unreasonable stations and grids are eliminated through quality control. Last, for the next time, the previous steps are repeated, and so on, which guarantees temporal dynamics. Its biggest characteristic is that the retrieval coefficients are not fixed, but variable with time and space, which overcomes the errors from regional and temporal (seasonal) differences of the physical features. By comparing it with another retrieval approach, the primary analysis indicates that the error of the snow data through the dynamic approach to retrieving snow depth based on integrated observed and remote sensing data is generally smaller, and the accuracy percentage is higher. Compared to observed data, it has a continuous snow depth distribution that is more reasonable than that of observed field, and in the regions where there are few stations, more appropriate snow depth data could still be obtained. Moreover, compared with the results from direct remote sensing retrieval approach and visible snow cover, the distribution of snow cover obtained by the approach is closer to real field, while the results from static remote sensing retrieval approach and visible snow cover usually underestimate snow cover extent in North China and Central China, and the retrieval result in the western China is also improved using the dynamic approach.

The Seasonal Characteristics of Regional Atmospheric Transport and Dispersion over the Pearl River Delta

Huang Jian, Liu Zuoting, Huang Minhui, Huang Huijun, Lü Weihua, Yang Yongquan

2010, 21(6): 698-708.

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Abstract:
After being emitted from the sources, air pollutants experience a series of atmospheric physical and chemical processes before reaching the receptor, in which the core process is the atmospheric transport, diffusion process and the clearance changes accompanied with them. Understanding the climatic background of atmospheric transport and diffusion of the Pearl River Delta would be helpful to determine the area affected by air pollutants, the regularity of air pollutants input, output and detention over this area, providing scientific basis for air pollution prediction, control and management. Based on the meteorological field of wind, temperature, humidity, geopotential height and precipitation from the NCEP/NCAR reanalysis for the period of 1985—2004, the HYSPLIT dispersion model and setting virtual air pollution sources approach are adopted to simulate the distribution of air pollutant, dispersive path and detention time over the Pearl River Delta, with full consideration of wet and dry removal processes. The seasonal characteristics and long term trends of atmospheric transport and diffusion process over this region are examined, and the main results are shown as follows. The significant differences of the distribution, diffusive paths and detention time of virtual air pollutants among four seasons suggest that there are remarkable seasonal variations of atmospheric transport and diffusion processes over the Pearl River Delta. In spring and summer, the air pollutant convergence zone is located at northwest side of the Pearl River Delta, while in autumn and winter it lies on the northwest side of the Pearl River Delta. Among four seasons, the convergence zone in summer is the strongest, followed by spring, autumn and winter. In spring and summer, the air pollutants are transported and dispersed to the mountainous area of the northwest and north side of the Pearl River Delta, respectively, while in autumn and winter, those are transported and dispersed along the relatively flat coast of western Guangdong to the west southwest. In autumn and winter, the atmospheric transport and diffusion rates are significantly higher than those in spring and summer. Pollutants stay over the Pearl River Delta for longer than 24 hours for 66.7% and 75.3% of all the air pollution events in spring and summer, respectively, while in autumn and winter, there are only 22.1% and 30.4%. The terrain effect is one of the possible factors that responsible for the weaker atmospheric transport and diffusion in spring and summer. For the period of 1985—2004, atmospheric transport and diffusion ability are weakest in 2004 and strongest in 1996 with significant annual differences, which may be caused by the variation of atmospheric systems.

Applicability of Universal Thermal Climate Index to Thermal Comfort Forecast

Zheng Youfei, Yin Jifu, Wu Rongjun, Ye Dianxiu

2010, 21(6): 709-715.

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Abstract:
The linear warming trend over the last 50 years (0.13 ℃ per decade) is nearly twice that for the last 100 years, and during 1995-2006 rank among the 12 warmest years in the instrumental record of global surface temperature since 1850 (IPCC AR4, 2007). Lots of researches denote that heat wave could lead to heat stoke and even death, so it has become a meteorological disaster that deserves attention from every government. In order to reduce the impact of heat wave on human health, lots of indices for thermal comfort forecast have been established both at home and abroad. However, atmospheric pressure and solar radiation are seldom recognized as factors influencing comfort, especially in China. In order to establish a Universal Thermal Climate Index (UTCI) including all meteorological factors that influence thermal comfort and human comfort in summer, an extensive questionnaire survey concerning the comfortable conditions is conducted. The database consists of questionnaire filled by 205 students those are participating in military training from 06:00 to 20:00 outdoor from 21 to 25 August 2009. Thermal sensations are reported on a five point scale and extensive statistical treatment of the data is performed. A multivariate analysis scheme is developed to handle the bulk of the data and ensure the validity of the results. The weather parameters are observed by NUSIT Weather Station being 500 meters away from the investigation site. The study confirms a strong relationship between thermal comfort and microclimatic conditions, including solar radiation, air pressure, maximum temperature, wind speed and relative humidity, ranked by importance. Therefore, the influences of atmospheric pressure and solar radiation have to be considered when forecasting the thermal comfort. UTCI is improved and formulated according to the body feeling temperature index of International Society of Biometeorology and current formula at home. The relationships between thermal comfort according to questionnaire surveys and indices including single element, bivariate, three major elements and UTCI are established and compared based on the database of questionnaire survey. The results show that domestic indices needs improving. The forecast effect of new UTCI adding atmospheric pressure and solar radiation is better than other indices both at home and abroad. Above all, based on weather forecast numerical model and SolAlt solar radiation model, the improved UTCI is an applicable index of thermal comfort forecast in Nanjing and it will provide better public weather servic

Channel Selection of Millimeter/Submillimeter Wave for Temperature and Humidity Sounding

Guo Yang, Lu Naimeng, Gu Songyan

2010, 21(6): 716-723.

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Abstract:
The weather systems generated over tropical oceans are difficult to be detected by conventional observation, so the satellite remote sensing becomes the most effective way to monitor them. Geostationary Meteorological Satellites can observe the earth with high temporal resolution and is desirable for severe weather monitoring. But the spatial resolution for microwave instrument on board GEO could be poor because the satellites are in their high altitude orbits. To improve the spatial resolution, millimeter/submillimeter wave sounders are considered. Passive microwave sounding from geosynchronous orbit is first studied in the mid 1970s. During the early 1990s, it's suggested that the use of submillimeter wavelength water vapor and oxygen bands can significantly reduce the antenna size and costs, while retaining good spatial resolution. Based on this notion, a practical submillimeter wave geosynchronous microwave (GEM) sounder and imager is developed by the Geosynchronous Microwave Sounder Working Group (GMSWG). During the mid 1990s aperture synthesis is proposed to geostationary microwave imaging and sounding. The Geo STAR (Geostationary Synthetic Thinned Aperture Radiometer) and GAS (Geostationary Atmospheric Sounder) concept are put forward by America and Europe respectively based on this technique. In order to explore the potential applicability of millimeter/submillimeter sounders in tropical observation, weight functions for O₂ and H₂O absorption bands are calculated based on the atmosphere profiles of tropical region. The peak distribution of weight functions show that the far wings of 118 GHz can be chosen to measure the atmospheric temperature in lower troposphere, and for the temperature of the upper level, the far wings of 425 GHz are more suitable. In terms of humidity observation, the 183 GHz and 380 GHz channel combinations can be used for the middle and upper levels. Based on the analyses above, considering industry capability as well, eleven temperature channel combination including three channels around 118 GHz and eight channels around 425 GHz, eight humidity channel combination including three channels around 183 GHz and five channels around 380 GHz are recommended as the microwave observation channels for the geostationary orbit in the future. Furthermore, the differences of brightness temperature in different bandwidth range of O₂ and H₂O absorption bands are calculated using the temperature and water vapor profiles. Through this bandwidth selection test, retrieval results of temperature and humidity are statistically analyzed.It shows that in the temperature detection channel, 5.3 GHz or less and 4 GHz or less can be set as the bandwidth range for 118 GHz and 425 GHz respectively. As for the humidity detection channel, 183 GHz with a range of bandwidth 8.5 GHz or less and 380 GHz with a range of bandwidth 15 GHz avoiding 360.498 GHz is recommended, which is the oxygen absorption channel.

Satellite Remote Sensing of Cyanophyte Using Observed Spectral Measurements over the Taihu Lake

Han Xiuzhen, Wu Chaoyang, Zheng Wei

2010, 21(6): 724-731.

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Abstract:
The chlorophyll a and cyanobacterial density are important variables for the evaluation of water quality and thus important for red tide monitoring. An evaluation of spectral measurements is implemented for the estimation of chlorophyll a (Chl a) and cyanobacterial density in the Taihu Lake. There are 39 sample points over the Taihu Lake during the experiment from 10 to 12 November in 2008. For each sample point, measurements of spectral reflectance and water quality sampling are conducted. Observation shows that cyanobacterial affect water reflectance greatly, leading to an obvious absorption peak in the red while strong absorption in the blue and near infrared bands. Spectral responses for points with little cyanophyte are similar to that of water reflectance. However, for the cyanobacterial points, spectral responses show the similar trend of vegetation to some extent. Besides, comparison between the reflectance obtained at nadir and at 45° departure indicates that the existence of cyanophytes has great effects on the visible and near infrared regions. This is because the increase of heterogeneity in water will increase the energy that can be acquired by the sensor. To investigate the operational application feasibilities for satellite remote sensing of water quality, equivalent reflectance based on FY 3A/MESRI and AQUA/MODIS band settings is derived using the spectral response functions. Comparison analysis indicates that the equivalent reflectance calculated from FY 3A/MESRI band settings is consistent to that of the AQUA/MODIS. Larger variations are observed for the cyanobacterial water indicating different sensitivity of these bands in water quality evaluation. Furthermore, the Ration Index (RI) model is used for the evaluation of water quality and high determination coefficients (RMS of 0.0174 mg·L^-1 and 0.0188 mg·L^-1 for Chla; 247.21×10⁶ L^-1 and 275.64×10⁶ L^-1 for cyanobacterial density) are observed for chlorophyll a and cyanobacterial density. An important meaning lies in the linear regression for all correlations which indicates the sensitivity for high values of water samples. Generally, RI calculated from MODIS bands is more suitable for water quality assessment. A possible explanation is that the much fine spectral resolution of MODIS bands is more sensitive to chlorophyll signals. This result will be helpful for further evaluation of optical characteristics and water quality using FY 3A/MESRI observations.

The Risk Assessment of the Fog Disaster Based on Vulnerability Calculating Related to the Urban Transportation Network

Hu Haibo, Xiong Yajun, Zhang Shuli

2010, 21(6): 732-738.

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Abstract:
In well developed urban area, the atmosphere is full filled with more aerosol than in suburban and rural area for industrial pollution and automobile emissions. It is evident that the accumulation of air pollutants contributes to the intensification of fog in urban. Fog has impacts on the living of citizens, especially in traffic affairs, in which fatal collision can cause casualties and death, further more the bad air quality in fog influences human healthy heavily. So it is very necessary to assess the risk of the fog disaster in city for emergency and disaster risk management. A new method is proposed to assess the urban fog disaster risks, calculating a risk index from fog probability, fragility and vulnerability, and the index is overlapped onto the map with GIS grid cell technology. The fog probability in urban area is determined based on the observatory data. The frequency of fog days is considered to be the probability of fog disaster, and for each grid cell a value is assigned. The Fragility Exponential (FE) is computed upon the regular gird cell, in which the density of the road net is its substitution while different road types have different weight coefficients in measuring the density, and the FE can be modified according to the important facility distribution. In the end, the density of the road net is normalized and considered to be the fragility of fog disaster. The population density is used as the index of vulnerability. Moreover, the probability, fragile, and vulnerability is composed by 5:2:1 to integrally sum up as the risk index of fog disaster in urban area. A 10 year fog observatory data of Beijing district is studied to assess the fog disaster risk by spatial grid. The result indicates that the high fragility value area is consistent to the extending of highway, ring roads and high rank roads. High risk area of fog disaster distributes in urban central area with dense population, highway, ring roads extension area and airport. It's also found that the frequency of fog in southeast area of Beijing is relative higher than any other area.

The Method of CINRAD/SB Radar Echo Intensity Calibration and Adjustment

Pan Xinmin, Chai Xiumei, Cui Bingjian, Huang Yueqing, Wang Quanzhou, Xu junling

2010, 21(6): 739-746.

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Abstract:
CINRAD echo intensity calibration is the key technology to improve the reliability of observational data. Improper intensity calibration adjustment method or mishandling of the alarm can lead to large measurement error. Based on test procedure of CINRAD/SB radar signal and the principle of echo intensity calibration, the work discipline of echo intensity calibration is established. The related parameter measurement, calibration and adjustment methods are introduced, clarifying receiver dynamic range, radar parameters, the line channel target syscal constant, test channel parameters. To meet the receiver's dynamic range, parameter measured adjustment method or the standards method is applied and the line channel target syscal constant calibration is considered. These methods ensure that echo intensity measurement error caused by changes of transmit power and receiver dynamic range is calibrated with real time corrected echo intensity data, and the technical requirements for controlling echo intensity measurement error range within±1 dBZ are met. The mechanisms through which receiver test channel parameter change and transmit power measurement error lead to the echo intensity measurement error are also discussed in detail. Calibration problem diagnosis and treatment process of CINRAD/SB radar echo intensity are illustrated based on relevant alarms of echo intensity calibration and echo display information, combining the receiver test channel, main channel and the antenna feeder system, transmission power. The imperfections and improving method of CINRAD/SB echo intensity calibration technique is explored to provide reference and technical support for new generation of weather radars.

Application of Multi job Management Mode to Numerical Simulation for Wind Energy Resource

Zhang Xiaowei, Li Zhengquan, Yang Zhong'en, Yao Yiping, Cai Juzhen

2010, 21(6): 747-753.

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Abstract:
Numerical simulation of regional wind energy resource requires high performance computing resource. High spatial/temporal resolution models need more running time due to the limit of computing power. So lots of efforts are devoted to improving calculation efficiency of numerical model. The coupled MM5/CALMET model is proved to be suitable for simulating wind energy resource, and it is also recommended by China Meteorological Administration as a numerical simulation model to estimate provincial wind energy resource. Therefore, interpreting the computational flow of MM5 and CALMET models, a multi job management mode is designed based on parallel calculation principle. The numerical simulation of wind energy resource in Zhejiang Province demonstrates that the multi job management mode can significantly improve calculation efficiency of the coupled MM5/CALMET model. In the numerical simulation experiments of monthly parameters which are related to wind energy resource assessment, the CALMET model without parallel calculation needs 1501.2 minutes, but it only costs 149.5 minutes when implementing the multi job management mode, increasing the calculation efficiency of the coupled MM5/CALMET model by 4 times. The multi job management mode shows the ability to further improve the calculation efficiency of the coupled MM5/CALMET model with its simulation area expanding and simulation period prolonging.

Designing and Implementation of Meteorological Information Web Sharing System Based on Flex

Sun Lihua, Wu Huanping, Zheng Jinwei, Luo Bing, Wang Qi, Hu Lixia, Zheng Weijiang, Lu Zhongliang

2010, 21(6): 754-761.

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Abstract:
With the pace of meteorological service information accelerated, more and more kinds of comprehensive meteorological observation and forecast data have been produced. To share meteorological data timely and effectively online, the meteorological information delivering system is established based on Flex and Rich Internet Application (RIA) which are of advantage in internet GIS. On the basis of user requirement and the construction target analysis, a general framework composed of four layers is proposed for the Meteorological Information Web Sharing System. The data layer on the bottom mainly stores meteorological data, geo spatial data and socioeconomic data, providing fundamental data for upper layers. The upper service layer consists of various GIS services, Web services and LiveCycle Data Service. Different data and application services will be sent according to different requests from presentation layer. The presentation layer is composed of visual Flex controls, including map display object, geometric object, functional object etc. This layer communicates with data service layer and interacts with the client layer. The uppermost layer is the client layer with Flash plug in installed for running SWF files. The features of the sharing system are introduced from six aspects, including basic geographic information displaying, meteorological data displaying, information querying, data downloading, spatial analysis on meteorological data, and web map plotting/outputting. Finally, four key issues related to this system are further discussed. The first one is data organization and management. Massive data of the system are stored and managed by category. For instance, the view of existing data based on old database structure is newly designed for management, obtaining a minimum dataset satisfying constraint in order to improve data access efficiency. With respect to meteorological data stored as a file form, spatial database is adopted. Meanwhile, all data is created following by meta data tables. The second issue is meteorological data conversion. Utilizing model builder technology, some complicated geo processing models as tasks are established, which can automatically accomplish data conversion, data generation and data loading. The task can be done as a batch job by customizing parameters of the model manager. The third issue is cache technology for map services. Basic geographic map and meteorological services are cached with different strategies to improve the display efficiency. The last issue is map display technology based on Flex. Due to combination ArcGIS API for Flex with features and special effects of Flex, the meteorological information delivering system is notable and interactive.In conclusion, Flex and Flash are feasible in meteorological information sharing field, improving the display efficiency of meteorological data in internet GIS. The advantages of this system comparing with the conventional Web GIS in meteorological field are discussed. This system can also bring a high performance meteorological information sharing platform based on network for emergency and public meteorological services. It can also lay solid technique foundation for constructing more effective meteorological information delivering system in nationwide.

Application of the LDM Software to Meteorological Data Exchange

Ai Yan, Yang Genlu, Wei Yantao, Wang Min, Wu Peng

2010, 21(6): 762-768.

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Abstract:
Multiform meteorological data exchange platform with different data interface and exchanging software are used around the country, adding the inconvenience and inconsistency of communication management, data acquisition, data transmission, data monitoring when a new kind of data are applied to operational work. The Unidata Local Data Manager (LDM) is a collection of cooperating programs that select, capture, manage, and distribute arbitrary data products. The system is designed for event driven data distribution, which means any data put into the data product queue can be processed as quickly as possible. The LDM system is widely used in some developed countries. All the operational radar data of America are transferred to National Weather Service (NWS) by LDM. It is also used in the World Meteorological Organization (WMO) THORPEX Interactive Grand Global Ensemble (TIGGE) project to transfer data among the data centers. In order to validate the applicability in civil meteorological data communication, a series of research and experiment are carried out, and Real time Meteorological Data Distribution Service System Based on LDM is built in Henan. Using the LDM system, every new observation data and the data of Project 9210 are transferred reliably, so the data transfer program can be integrated. LDM is designed as event driven which can process data files with multithreading, so it can resolve the congestion and ensure priority. The implementation of LDM program improves the transfer quality, resolves the problem of inconsistency, and ensures priority when much more files are processed. Workloads of operators on duty can also be reduced when monitoring data communication. The LDM system has good prospect in civil meteorological data exchange.

Vol.21, NO.6, 2010