应用气象学报

Aerosol Chemical Compositions of Beijing PM₁ and Its Control Countermeasures

Zhang Xiaoye, Zhang Yangmei, Cao Guoliang

2012, 23(3): 257-264.

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Abstract:
The mass concentrations of sulfate, nitrate, ammonium products, organic matter and black carbon are measured at urban Beijing during summer, autumn of 2007 and winter, spring of 2008. Combining assessment of major chemical compositions in less than 10 micron particles with at least an entire year data from various rural and urban sites in 16 areas of the world, the concentration level of mineral aerosol in China, which is partially a result of sand and dust transported from desert areas and contributions from urban fugitive dust/fly ash sources, is found to be almost equivalent to or even higher than the sum of all kind of aerosols in urban Europe and North America, suggesting the control countermeasures for aerosol particle in diameter between 2.5 and 10 micron in China should not be neglected, especially when the country pays much attention to control the fine PM_2.5 particles. In urban Beijing, the averaged concentrations of PM₁ are around 94, 74, 66 μg·m^-3 and 91 μg·m^-3 for spring, summer, autumn and winter, respectively, with the annual mean of 81 μg·m^-3. The relative contributions of organics, sulfate, nitrate and ammonium product are about 41%, 16%, 13% and 8%, respectively. The black carbon and chloride contribute Beijing PM₁ about 11% and 3%, respectively. The fine mineral aerosol contributes about 7%. The key of control PM_2.5 is to reduce the main emission species and their chemical transformation of PM₁ particles, and the more important is to control the organic matter at Beijing, although Beijing's pollution control has been very difficult since 26 million people living there. To be scientifically, even if China's control countermeasures can achieve one hundred percent, it is also hard to reach the air quality level of Europe and North America, because of the higher background mineral aerosol level. The cost-effective control measures and new PM_2.5 standard considering the health of Chinese need to be further investigated.

Characteristics of Precipitation in Beijing and the Precipitation Representativeness of Beijing Weather Observatory

Wang Jiali, Zhang Renhe, Wang Yingchun

2012, 23(3): 265-273.

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Abstract:

In order to investigate annual variations and characteristics of summer precipitation, Beijing is divided into four areas according to different land use and topographic height: The urban area (UA), suburban area (SA), north mountainous area (NMA), and south mountainous area (SMA). Results of cluster analysis based on monthly precipitation amount during 33 years verify the reasonability of the regional division. Using observed monthly rain-gauge measurements from 14 meteorological stations in Beijing, differences among four areas are investigated. Significant annual mean precipitation differences are observed among four areas, with the maximum precipitation amount observed in SA (620 mm), followed by UA and SMA, and the minimum precipitation amount observed in NMA (476 mm). In UA and SMA, the precipitation amount is similar, presenting a significant difference from SA and NMA. Precipitation amount in all the four areas shows a decreasing trend, with the highest decreasing rate observed in SA (47 mm/10 a), which passes the significance test at a significance level of 0.06, and the lowest decreasing rate observed in NMA (0.7 mm/10 a). Summer precipitation which accounts for 79.1% of the annual total amount in four areas is analyzed. Results show that UA and SMA have similar features, yet being significantly different from those in SA and NMA.Differences in precipitation between Beijing Weather Observation (BWO) and four areas are also investigated, and results show that BWO isn’t significantly different from UA and SMA in both annual and summer precipitation amount, but differences between BWO, NMA and SA are significant. Upon comparison of the statistics of root-mean-square error and correlation coefficient of precipitation between BWO and four areas, consistent results are obtained, which reveals that the representativeness of precipitation in BWO is good for UA and SMA, but is poor for NMA and SA. As a result, it suggests that some other stations should be selected in suburban and north mountainous areas to represent the characteristics of precipitation there. Together with BWO, these stations may better reflect the characteristics of precipitation variations over Beijing metropolitan area.

Application of GRAPES Meteorological and Hydrological Coupled Model to Flood Forecast

Wang Lili, Chen Dehui, Zhao Linna

2012, 23(3): 274-284.

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Abstract:
The GRAPES (Global-Regional Assimilation and PrEdiction System)_Meso model developed by China Meteorological Administration is coupled with a hydrological model to increase lead-time of flood forecast. GRAPES_Meso model is run in 15 km×15 km horizontal resolution and 5 km×5 km horizontal resolution. The initial fields and lateral boundaries of 15 km×15 km horizontal resolution of GRAPES is provided by global NCEP forecast datasets, and the initial fields and lateral boundaries of 5 km×5 km horizontal resolution of GRAPES is provided by 15 km×15 km horizontal resolution of GRAPES. In order to match the input scale of hydrological model, quantitative precipitation forecasts of GRAPES_Meso model is downscaled to 5 km×5 km horizontal resolution. Xin'anjiang model and grid-based distributed Xin'anjiang model are used, which have been widely applied and proven effective in flood forecasting and hydrological simulation in humid and semi-humid regions of China for a long term. Wangjiaba Station and Xixian Basin in the upper reaches of the Huai River are chosen as sensitive areas. The two hydrological models are driven by forecast datasets of GRAPES. Upstream Wangjiaba Station, the basin is divided into 10 sub-basins for the coupling experiment of Xin'anjiang model. And Xixian Basin is for the coupling experiment of grid-based distributed Xin'anjiang model. A flood which maintains from 0800 BT 28 August to 1400 BT 29 September in 2009 is forecasted by these two models. The experiment results show that compared with observed precipitation, quantitative products of GRAPES model in 15 km×15 km and 5 km×5 km horizontal resolutions are well consistent. The quantitative products of GRAPES model with 5 km×5 km are larger than the quantitative products of GRAPES model with 15 km×15 km. A promising tool is given by GRAPES meteorological and hydrological coupled hydrologic model to increase lead-time of real-time flood forecast, compared with that driven by raingauge observation. The accuracy of the flood forecasting based on the precipitation prediction of GRAPES model is approximate to the precipitation prediction. The performance may be better if the input requirements for hydrological models are exactly met.

Size Resolved Aerosol OC, EC at a Regional Background Station in the Suburb of Beijing

Yan Peng, Huan Ning, Zhang Yangmei, Zhou Huaigang

2012, 23(3): 285-293.

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Abstract:
Carbonaceous aerosols constitute major component of atmospheric aerosols. In Feburay, May, July and September of 2004, size resolved aerosol sampling measurements are conducted respectively at Shangdianzi Regional Atmospheric Background Monitoring Station which is in the suburb of Beijing, to represent the four seasons of the year. OC, EC are analyzed in the lab with Sunset OC/EC Analyzer (NIOSH TOT method, Sunset Lab, USA). The seasonal variations and size distributions of OC and EC composition are characterized, and correlations between OC and EC are discussed as well. The analysis shows that the mean concentration of OC for TSP (Total Suspend Particles) at Shangdianzi Station in the four seasons ranges from 7.5 μg·m^-3 to 31.5 μg·m^-3, and EC ranges from 1.4 μg·m^-3 to 6.6 μg·m^-3. As to PM_2.1 (particles with aerodynamic diameter less than 2.1 μm), the mean concentrations are from about 4.0 μg·m^-3 to 19.1 μg·m^-3 for OC, and from about 0.8 μg·m^-3 to 4.3 μg·m^-3 for EC. The significant seasonal variations of mean OC, EC at Shangdianzi are found with the highest OC and EC concentration appearing in winter and lowest in summer. The size distributions of OC and EC at the Shangdianzi Station shows obvious seasonal differences, with OC and EC peak size at 0.65—2.1 μm during the winter, summer and fall time, and shifts to 2.1—4.7 μm during the spring time. In summer and fall, the OC and EC are mostly concentrated in the fine particles (with particle size less than 2.1 μm). In spring, the size distributions of OC and EC are quite different, where there is a significant enhancement OC, EC mass contents in the coarse particles, which is related to the collision of carbonaceous aerosols with dust particles rich in the spring atmosphere. The mass of organic matter ([OM]=1.4[OE]) in PM_2.1 accounts for about 43%—80% of the total mass of OM, and EC in PM_2.1 accounts for 54%—70% of total EC. The average ratio of OC and EC for the whole period of sampling is about 4.0—6.0, which is similar with the reported values obtained at many urban sites of China, when considering the difference between the OC, EC laboratory analysis methods. The square correlation coefficients (R²) between OC and EC in winter, spring and fall are 0.84, 0.81, and 0.73 respectively. However, the correlation coefficient is lowest in summer, with R² about 0.49. This seasonal pattern of correlations indicates the complications for sources and production or removal processes of the carbonaceous aerosols in summer time in that region.

Characteristics of Lightning Casualties and Vulnerability Evaluation Regionalization in China

Gao Yi, Zhang Yijun, Zhang Wenjuan, Zhang Yang

2012, 23(3): 294-303.

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Abstract:
According to the data of lightning disasters from 1997 to 2010 and lightning observation by TRMM satellite, feature of national injuries and deaths from lightning is analyzed and the results indicate that lightning causes 460 deaths and 425 injuries every year on average. The mortality rate is 0.36 per million people and 0.48 per ten thousand square kilometers every year. Three indexes about lightning casualties reports, the number of lightning fatalities per ten thousand square kilometers and the number of lightning fatalities per million people have good correlation. Lightning-related casualties have increased for the period of 1997—2007 and then begin to decrease since 2008. Casualties anomaly percent is positive in the year of 2002, 2004, 2005, 2006 and 2007, with the maximum value in 2007, when the ratio is 78% more than normal years.In order to reveal the vulnerability of lightning which lead to injuries and deaths in different region, R-cluster analysis is used for sifting the 8 indexes affected by vulnerability evaluation. Lightning density, casualties frequency, population, and region areas are selected as variables. Comparability measures of each sample are calculated by using Euclidean distance, and then the method of Q-cluster is used to analyze and calculate these date. Finally the results of 6 different kinds of risk zones of lightning that lead to injuries and deaths in China are given. Guangdong and Hainan pertain to vulnerability evaluation extreme high areas. In these areas, the comprehensive vulnerability evaluation of cluster reaches up to 5.017, where both the average density of lightning and personnel casualty rate is the highest in the six categories. In the opposite, the northwest and northeast of China are areas with the lowest vulnerability. Finally, Ward’s method of Q-cluster is adopted to explain and testify the result of cluster, showing the cluster solution is not only stable but also reliable. The result of the classification is appropriate, and preferably reflects regional vulnerability characteristics of lightning-caused casualties.

Statistical Correction for Dynamical Prediction of 500 hPa Height Field in Mid-high Latitudes

Tan Guirong, Duan Hao, Ren Hongli

2012, 23(3): 304-311.

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Abstract:
In terms of the Météo France model data of DEMETER project, the performance of ensemble forecast system at 500 hPa height field of winter in mid-high latitudes (20°—90°N) is studied, then both optimum subset regression (OSR) and dynamical analogue prediction (DAP) method are used to improve the model prediction. First, empirical orthogonal function (EOF) analysis is applied to investigate the observed 500 hPa height field of 1958—1991. The time coefficients of different modes for the numerical model are calculated by projecting the model data onto the observed EOF basement. Then the performance of the model modes based on empirical orthogonal function (EOF) of observations is examined by calculating the anomaly correlation coefficient (ACC) between the time coefficients of the leading 10 model and observed EOF modes. Next, the optimum subset regression (OSR) experiential model is established to advance the model prediction on the modes, which are predicted by the numerical modes with very low skill (i.e., low skill modes). Finally, the mean time coefficients of 5 observed similarity years on each low skill mode are substituted for those of the model prediction, where the similarity year is defined as its time coefficient estimated by OSR has minor difference from that of the prediction year. In this way, the analogue method is employed to correct the model prediction on OSR basis, namely, OSR-based analogue method. The results suggest that the prediction ability of the mode accounting for less variance may be higher than the mode with more variance, such as the 2nd and 3rd EOF modes have low skill but with large variance contribution to total variance of the model field. OSR fails in advancing the model prediction. The DAP method based on OSR (DAP-OSR) shows a possibility of improving the prediction techniques with ACC increasing 0.1 by correcting the bad modes of model while OSR fails.Correcting the dynamic prediction by combing the advantages of the numerical models and statistic methods, the nonlinear analogue method based on linear OSR shows a possibility of improving the prediction techniques by correcting the EOF modes, which are predicted by the numerical modes with very low skills. However, since the numerical model has a poor capability in representing the 2nd and 3rd EOF modes of the observation which account for large percent of total variance, and the forecast ability can not be improved effectively because the model prediction information is not enough or incorrect. Therefore, it is necessary to make further analysis on the samples of the modes, predicted with low skill by the numerical model, and the corresponding external forcing. The external forcing might be more effective to improve the correction for such modes with low skill.

The Central Asian Vortexes Activity During 1971—2010

Zhang Yunhui, Yang Lianmei, Xiaokaiti Duolaite, Qin He, Li Yuanyuan, Yang Xia

2012, 23(3): 312-321.

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Abstract:
The synoptic scale system of cold vortex (the central Asian vortex) which occurs from east of Aral Sea to Xinjiang are frequently associated with Urals ridge, and its abnormal activity may cause many disasters such as rainstorm (snowstorm), low temperature and drought in Xinjiang, even affecting the weather and climate in east China. Using NCEP/NCAR reanalysis daily datasets from 1971 to 2010, the activity patterns, different moving tracks of the central Asian vortex and its influences on Xinjiang are analyzed. The result indicates that the central Asian vortex processes occur 305 times and 1166 days altogether during its strong period in the past 40 years. There are two high-frequency activity center along with the latitude: One distributes from 47.5°N to 55°N (north vortex) with 57% of the vortexes, and the other one distributes from 35°N to 47.5°N (south vortex), where 37% of the vortexes occurs. Northern vortexes change greatly in different seasons, accounting for 52% in summer. But southern vortexes occur evenly in different seasons, maybe a little more in autumn and spring. The mature period of the central Asian vortexes is 3.8 days on average, the frequency decreases rapidly with the mature period increasing: 56% vortexes sustain between 2 to 3 days, 27.5% maintain for 4 to 5 days and only 16.5% can last for more than 5 days. The vortexes show obvious monthly, seasonal, annual and interannual variation characteristics. It occurs the most in July and summer, and the least in April and winter, and the decadal increasing trend is significant. As to moving tracks, most of them move northeastward, eastward, southeastward and about 6% move little or move without obvious rules. Different moving track causes different weather in Xinjiang. About 68% of southeastward moving north vortexes and 30% of eastward and northeastward moving south vortexes have caused heavy precipitation in Xinjiang. The central Asian vortex has two types of influences on the weather in Xinjiang: One type brings heavy precipitation in Xinjiang, which is called wet vortex, and the other type causes cool wind and a long period of cold weather with little precipitation, which is called dry vortex. Dry vortexes account for 60% of the total and occur evenly in different seasons. However, the wet vortex occupies 40% of the total and is significantly different in different seasons. 57% wet vortexes occurs in summer and at this time there are more wet vortexes than dry vortexes, but for autumn, spring and winter, there are more dry vortexes than wet vortexes, and only 2% wet vortexes occur in winter. The seasonal variation patterns of wet vortexes are consistent with that of precipitation in Xinjiang.

SPI-based Drought Variations in Xinjiang, China

Li Jianfeng, Zhang Qiang, Chen Xiaohong, Bai Yungang

2012, 23(3): 322-330.

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Abstract:
Daily precipitation data at 53 stations during 1957—2009 in Xinjiang are analyzed based on Standardized Precipitation Index (SPI) technique with the aim to investigate the spatial-temporal patterns of drought events. The Mann-Kendall trend test is used to detect the trends of monthly SPI values, drought intensity and drought duration. Pre-whitening technique is applied before the Mann-Kendall trend test to eliminate the autocorrelation within the precipitation series.According to the results, the frequency of mild drought in North Xinjiang is less than the theoretical frequency, while frequencies of moderate, severe and extreme droughts are higher than the theoretical ones. The statistical condition of drought events in South Xinjiang is to the opposite. Although the drought disaster in Xinjiang is abating in general, the trend varies in different areas. The decreasing of drought in North Xinjiang mainly happens in winter. However, in spring, summer and autumn, the decreasing is insignificant and has obvious influences on agriculture. As the agricultural water demand is increasing tremendously recently, this insignificant decreasing of drought hardly compensate the shortage of water demand. As a result, this change may be not beneficial to agriculture. The abating of drought in South Xinjiang mostly occurs in summer, while the drought in the south part of South Xinjiang is aggravating. The drought in East Xinjiang slightly aggravates. In North Xinjiang, both the intensity and duration of drought have decreasing trends. The intensity and duration of drought in South Xinjiang are both slightly increasing. In the middle part of East Xinjiang, the intensity and duration of drought are both significantly increasing. These results provide theoretical and practical merits for better understanding of variations of drought, monitoring of drought, and mitigating the losses of drought disaster.

The Application of LAPS to Hail Cloud Simulation

Xiang Yuchun, Yang Jun, Tang Renmao, Fu Danhong, Li Dejun, Peng Juxiang

2012, 23(3): 331-339.

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Abstract:
Local Analysis and Prediction System (LAPS) introduced and localized by Wuhan Institute of Heavy Rain integrates a variety of observations in central China and provides rich information on high-resolution meso-scale analysis field. Several hail weather processes occurred in mountainous region of western Hubei on 27 and 28 July in 2008 are analyzed based on LAPS data. And the hailstorm cloud is simulated with the three-dimensional convective cloud model which is initiated with the output of LAPS and the sounding.The difference between dew point and air temperature of sounding data and LAPS data at 0800 BT 27 July 2008 shows the humidity is higher above the hail location. According to LAPS data from 0800 BT to 1600 BT at the hail location, the temperature profiles show that there is cold air inflow in the upper air, and the differences between dew point and air temperature demonstrate that the humidity increases near the ground and then decreases with the altitude, while increases again in the upper air. LAPS data show the stratification status and wind field over the hail point is more and more favorable for hail formation, reflecting more realistic information than the sounding data at 0800 BT.The simulation results initiated with LAPS data and sounding data at 0800 BT 27 July 2008 are very close, but on 28 July the simulated echo intensity, vertical airflow speed, max wind speed and the amount of hail by LAPS data of the hail location are greater than that by sounding data. The simulation results initiated with LAPS data at 1600 BT 27 July and 1600 BT 28 July in 2008 near the hail time are larger than that at 0800 BT and the simulated amount of accumulated hail by LAPS data at 1600 BT is closer to the observation. It can be concluded that the simulation initiated with LAPS data near the hail time can better reflect the occurrence and development of the hail cloud which occurs in the afternoon. The simulated results of cloud maintenance time, hail intensity and distribution, hail size are consistent with the observation, which can provide a reference for local hail forecast. Results show that the output of LAPS can provide higher temporal and spatial resolution data for the three-dimensional convective cloud model than the sounding observations.The three-dimensional convective cloud model initiated with LAPS data near the hail occurrence time performs well in reproducing characteristics of the occurrence and development of hail cloud. Moreover, it can capture certain details such as several increment processes which are in agreement with the radar observations. Therefore, the model may contribute to warning condition for hail suppression operation and seeding scheme.

A Fog Nowcast Method Based on Satellite Remote Sensing and Numerical Products from Meso-scale Atmospheric Model

Li Yongping, Liu Xiaobo, Ge Weiqiang, Zhou Hongmei

2012, 23(3): 340-347.

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Abstract:
On the basis of satellite images, the fog areas are distinguished and extracted with procedures of spectrum analysis, vein structures, shape fractals and smoothness procedures. The surface auto-weather station data in Shanghai are analyzed and diagnosed, showing that the fog moves slightly faster than the wind speed on the ground. When the relative humidity drops to lower than 91%, or the temperature difference between the sublayer and air above exceeds 3.1℃, the fog will not maintain. The wind speed thresholds for the fog to lift are 6 m/s and 11 m/s on land and sea respectively.Furthermore, a method to make fog nowcast in 2 hours is developed based on the fog coverage detected by satellite remote sensing combining with the operational meso-scale atmospheric model outputs in Shanghai Typhoon Institute. And the elements of model are modified properly based on the observations of auto-weather stations. It is proved to be efficient and accurate by case study.At last, an operational forecast platform is established and its main features include geographic information stack, satellite image editing and processing, satellite fog area identification, real-time monitoring of ground atmospheric elements, fog short-term warning product releasing, etc. Statistics with a large number of samples in foggy season of recent two years indicates that the accuracy rates of 1 and 2 hours forecast are 70% and 65%, respectively. On the other hand, this method has its limitations, e.g., the accuracy largely depends on numerical weather forecast and complexity of clouds covered. The forecast is unreliable when the atmosphere elements reach the thresholds mentioned above, and when the clouds are too thick to distinguish the fog below.

GPGPU Accelerated Massive Parallel Design of Long Wave Radiation Process in GRAPES-Global Model

Guo Miao, Jin Zhiyan, Zhou Bin

2012, 23(3): 348-354.

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Abstract:
In recent years, with the rapid advance of GPGPU (General Purpose Graphic Processing Unit) technology, leveraging the massive parallel processing power of GPGPU to provide super-computing capacity becomes a new trend. At present, GPGPU has been applied to scientific calculations of many fields. GRAPES (Global/Regional Assimilation and PrEdictions System) is the new-generation multi-scale numerical model, which is developed by Chinese Academy of Meteorological Sciences and plays an important role in weather forecasting and research. Long wave radiation process is one of the most important physical processes in GRAPES_Global model and occupies a lot of processing time, affecting the whole model's computing efficiency. Since this process could be partitioned into different tiles within the horizontal plane, a naturally parallel scheme could be carried out.A GPU has hundreds of stream processors within one chip, which enables it to handle thousands of hardware threads simultaneously, and gives much higher theoretical throughput: Over 1 TFlops by one chip. GPU also has a whole integration of supporting tool sets, from compiler to libraries, which could facilitate the development. Considering the characteristics of the long wave radiation computing process, keeping the high level MPI communication the same, a low-level fine-grained parallel architecture is designed to harness the computing power of the new hardware. This massive parallel processing implementation is based on NVIDIA GPGPU and CUDA technology. Other than looping through a big portion of the atmosphere columns within conventional CPU-based systems, the new GPU-based implementation uses each small core to process a single column. This scheme has three major advantages, including much higher thread concurrence, using bigger band width of GPU memory, denser computing intensity and better efficiency. Experiments with real dataset are performed and the correctness of the new design is validated, which show that Tesla C1060 has an 11x speedup compared to a high-end x86 CPU, greatly improving the execution speed and forecast efficiency. Timing on sub-routines and data transfer time are also recorded and compared. Different partition configurations are carried out to get the best combination. Also, the overlapping of execution and data transfer is used to hide the latency. The experiment shows GPGPU has good potential to improve numerical weather forecasting models. With more and more routines ported to GPU systems, a much better speedup could be achieved over the whole model.

Improvement and Application of Artificial Neural Networks to Cloud Classification

Zhang Zhenhua, Miao Chunsheng, Zeng Zhihua, Shi Chunxiang

2012, 23(3): 355-363.

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Abstract:
2449 cloud classification samples are artificially selected from infrared channel 1, infrared channel 2 and water vapor channel of VISSR on FY-2C geostationary meteorological satellite during 2005—2009. Different linear combination of three channels are selected as feature values, which are brightness temperature of IR1, IR2, WV, and brightness temperature difference of IR1 to IR2, IR1 to WV, IR2 to WV. According to statistical theory, the sample probability distribution is assumed to help to remove some apparent unreasonable data such as outliers, and to understand cloud normal features better. It is found that the brightness temperature difference of IR1 to IR2 is most sensitive to the amount of thin cirrus cloud in 6 selected values. On the other hand, the error of the BP neural network model mostly comes from the contradiction of this feature too. A nested BP artificial neural network model is designed, and it's composed of two layers. The first layer includes five features of brightness temperature of IR1, IR2, WV, and brightness temperature difference of IR1 to WV, IR2 to WV that are used to classify each pixel to one of four categories such as clear, mixed cloud, thick cirrus cloud and strong convective cloud. And the second layer includes just one feature, brightness temperature difference of IR1 to IR2 that are used to classify mixed cloud to low-level cloud, mid-level cloud or thin cirrus cloud. Finally, every pixel is classified into one of total 6 categories corresponding to each color. Both layers adopt a BP neural network, the most widely used algorithm for generating classifiers, with one hidden layer and the additional momentum method, not only accelerating the training speed, but also reducing the redundancy of the networks.Error analysis shows that the accuracy rates of the nested BP artificial neural network for types of mid-level cloud and thin cirrus cloud have increased by 42.6% and 11.3%, respectively. The mean square error and normalized mean square error of the whole classification model have decreased by 6.1% and 44.7% with the correlation coefficient increasing by 3.4%. By comparison of the classification results from 3 tests of tropical, subtropical areas and tropical cyclone, it shows that the nested model identifies thin cirrus cloud more accurately than the traditional model. Therefore, the results of the nested model are more reasonable than the traditional model.

The Estimation and Application of Design Rainstorm Intensity in Tianjin Area

Ren Yu, Li Mingcai, Guo Jun, Xiong Mingming, Yang Yanjuan

2012, 23(3): 364-368.

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Abstract:
The design rainstorm is an important foundation for the construction of flood control and drainage facilities. It is significant to improve the design rainstorm for strengthening the response to the regional flood and urban waterlogging disaster risk, which has been increasing with climate change and social development. However, the regular observations of rainstorm from general weather stations are insufficient for estimating the intensity of design rainstorm in urban drainage. It has been of great significance to maximize the use of regular observations to geographically refine the design rainstorm in urban drainage. Therefore, two weather stations from Tianjin urban and Tanggu districts with long period of precipitation-in-minute records, are chosen to estimate the intensity of design rainstorm and fit the intensity formula. Two methods are used in data sampling, one collecting the annual maximum and the other collecting multiple values per year. The comparison of the two locations indicates that the design rainstorm intensity in Tanggu district is much greater than that in the urban district. As a result, the drainage design at Tanggu district should be different from the urban district. Otherwise, Tanggu district would be confronted with greater risk of urban waterlogging disaster. The comparison of the two intensity formula suggests that the one based on the annual-maximum sampling is applicable in drainage design for the return period of 2—10 years. The application scope of the estimated design rainstorm intensity using regular observations is also pointed out for urban drainage. This provides a realistic reference for further spatial refinement of urban drainage design rainstorm.

Fengyun Series Meteorological Satellite Data Archiving and Service System

Qian Jianmei, Sun Anlai, Xu Zhe, Xian Di, Gao Yun, Luo Jingning, Zheng Xudong

2012, 23(3): 369-376.

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The Internet, WebGIS, distributed spatial database, three-dimensional global images and several derivative technologies are developing rapidly in the 21st century. The meteorological satellite data has following features: Huge amount of daily data volume and archived data volume, high frequency of the historical data download, and the data users distribute around the world. In order to meet the needs, meteorological satellite data archiving and service system is constructed, focusing on high frequency data archiving and management for high capacity. The system provide users with a variety of fast and convenient query retrieval and efficient data downloading methods, as well as satellite data displaying from multiple angles and Internet-based data services.Meteorological satellite data archiving and service system developed by National Satellite Meteorological Center relies on Fengyun series satellites. The system construction takes on unified design, rolling development and batch expansion method. It is a comprehensive information service system of meteorological satellites. The system adopts today's advanced and sophisticated computer technology, storage technology, network data retrieval technology, database technology, information dynamic release technology and GIS technology to establish a new generation of national environmental data archiving and service system through FY-2 and FY-3 series satellite ground application system. It takes account of foreign meteorological satellite data. It can not only provides data retrieval service, but also help all kinds of users to share satellite data with various aids and information, meeting all domestic and international users' demands.Meteorological satellite data archiving and service system integrates several high-performance servers, high availability disk array, large-scale automated tape library as well as system software, database software, storage software and application software, all of which constitutes archive and service application clusters. The application of configured dynamic load container technology and multi-server processing load balancing and parallel computing technology makes the cluster a highly scalable, highly available, highly efficient operational system to realize all levels of satellite data archiving, customization, retrieval, dynamic information release, operation monitoring, management, historical data integration and other functions. Internet-based full dataset sharing technology, distributed spatiotemporal integration of database storage technology, WebGIS global satellite image distribution technology, visual processing and display technology, 3D earth image distribution technology, multi-source data fusion technology and many other key technologies are adopted in the system to improve data sharing and service.Completion of the system meets the needs of operational meteorological satellite, achieving daily 2 TB data storing and daily 1 TB data download service. The system running in National Satellite Meteorological Center is the first one to provide internet-based full archive dataset (online, nearline, offline) sharing service in the area of civil remote sensing satellite data services, National Satellite Meteorological Center has archived 801 kinds of data and products for 21 Chinese and foreign satellites, the total storage is up to 1150 TB, and various satellite data sharing service are available for 24258 registered users. The system can also be configured to expand to meet future needs.

Application of Memory-forwarding Model to Data Transmission System of CIMISS

Yang Runzhi, Ma Qiang, Li Dequan, Zheng Bo

2012, 23(3): 377-384.

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In China Integrated Meteorological Information Sharing System (CIMISS) Project, the transmission time of data has put forward specific requirements. As one of the 14 categories of data, satellite data and products have more types, higher capacity, and more files amounts comparing with other conventional data files. As in recent years, the number of satellite data and products categories have gradually increased, meanwhile, the scope of applications of satellite data and products is being used more frequently in both weather forecast and research. Therefore, the satellite data transmission process calls for better timeliness.Considering the features of satellite data and products from users' aspects, the current satellite data receiving and forwarding process in National Meteorological Information Center (NMIC) is analyzed, and the limitation of existing procedure is figured out. In the existing satellite data forwarding process, the data receiving process is handled by standard FTP server, and data forwarding process uses standard FTP client. So it makes data receiving and forwarding flow, two relatively independent processes. The data receiving process is only responsible for the various data source reception, which only makes sure that all the arrived data and products could be recognized and transferred to data forwarding process successfully. Also, the data forwarding process only takes the responsibility to constantly scanning the sending directory to check out whether there is data or products to send. It may be concluded that there is no communication between data receiving process and data forwarding process, thus makes the total timeliness of data transmission lower than the ideal value.In order to solve or improve the situation, a new memory-forwarding model is proposed. In this model, by the memory sharing mechanisms, the data receiving process and forwarding process are combined as a unified whole, which has reduced the number of intermediate processing links. Based on memory-forwarding model, a unified procedure is designed by restructuring the FTP server transformation module. Through the development and testing of prototype systems, memory-forwarding model and unified procedure has been fully applied and achieved stage progress, and it will continue being validated and improved in further actual business system.

Vol.23, NO.3, 2012