应用气象学报

2017, 28(5)

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Abstract:

Implementation and Development Plan of MICAPS4

Gao Song, Bi Baogui, Li Yuean, Wang Ruotong, Dai Kan

2017, 28(5): 513-531. DOI: 10.11898/1001-7313.20170501

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Abstract:
Marked by refined weather forecasts, modern weather forecasting demands for higher spatial and temporal resolution of weather data applications. However, the existing forecast analysis system-MICAPS3 (Meteorological Information Comprehensive Analysis and Processing System Version 3) cannot meet needs of using real-time meteorological data with big data characteristics. Besides, MICAPS3 cannot provide sufficient support for numerical weather prediction model, ensemble prediction model and grid forecasting product, which are playing increasingly important role in the professional forecasting fields. Therefore, China National Meteorological Center launches development of MICAPS4, aiming to build an advanced, efficient, intelligent, convenient and open modern weather service forecast platform.Firstly, established a real-time forecasting system based on big data technology to solve the key technical problems of data processing, storage, analysis and display efficiency. Secondly, set up several specialized platforms to meet needs of different complex forecasting business. MICAPS4 combines information technology with forecasting technology and forecasting business processes to solve the key technical problems of the platform integration of modern forecasting methods and the production of refined forecast, many of specialized platforms based on MICAPS4 basic framework have promoted the application of business in China National Meteorological Center and many provinces. CIMISS (China Integrated Meteorological Information Sharing System)-MICAPS4 massive data storage environment has greatly reduced the workload of system deployment and localization, improved data analysis and data storage access efficiency significantly. Besides the utilization of the big data technology, MICAPS4 client is also upgraded in underlying rendering engine using parallel computing framework, and it can display high resolution data in high efficiency including the stream animation as a result. MICAPS4 client follows the OGC (open geospatial consortium) standards, to achieve the standard of geographic information and the intervention of WMTS (Web map tile service). The client of MICAPS4 allows users to customize data display style conveniently and support the forecast product rapid manufacturing. Flat design interface is adopted and users can switch between black theme and white theme quickly, to reduce visual fatigue and support the forecast product rapid manufacturing.MICAPS4 is a modern full-purpose forecaster work station system for processing and displaying meteorological data. The multi-window technology and specialized applications make MICAPS the ideal tool not only for operational weather forecasting, but also for other applications where meteorological information plays a vital role.

Characteristics of a Plateau Vortex Precipitation Event on 14 July 2014

Zhao Ping, Yuan Yi

2017, 28(5): 532-543. DOI: 10.11898/1001-7313.20170502

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Abstract:
Using various radar and disdrometer datasets from the Third Tibetan Plateau Atmospheric Science Experiment, MODIS data, surface and sounding datasets, temporal and spatial variations of one rainfall event on 14 July 2014 over Naqu in the central Tibetan Plateau is analyzed, the synoptic and meso-scale atmospheric circulations, and associated cloud-rainfall microphysical characteristics are also investigated. This rainfall process includes three stages, namely, the first stage with heavy rainfall starts in the afternoon (1400 BT) and ends at 1800 BT 14 July, the peak intensity of hourly precipitation occurs during 1500-1600 BT, which reaches 2.1 mm·h^-1. The second stage begins at 1900 BT, and the precipitation intensity weakens prominently compared with the first stage. The third stage is from 2200 BT 14 July to 0100 BT 15 July with a weaker precipitation intensity.Rainfall during the first stage is mainly produced by the development of a synoptic-scale plateau vortex and the formation of a meso-scale convergence line in front of the vortex circulation center. The radar echo propagates northeastward, and this stage ends with the weakening of the plateau vortex. Rainfall at night is mainly associated with the warm and moist southeasterly flow passing over the topography near Naqu, which provides favorable conditions of the atmospheric moisture, instability, and shallow dynamic elevation. With the intrusion of the low-level northeasterly flow, the radar echo generally propagates southeastward. Moreover, during the earlier stage of the first rainfall stage, the ascending motion is deep over the east of the vortex, exceeding 3 m·s^-1 between 3 km and 11 km above the ground level, which indicates the remarkable development of convections. During the later stage, rainfall is mainly produced by stratiform clouds, with a higher cloud top. Rainfall at night is mainly caused by stratiform clouds. The raindrop size distribution is wider (0.3-4.9 mm) than that size of 0.3-2.1 mm in the topographic rainfall, and the wider raindrop spectrum is closely associated with the larger rainfall rate.

The Probabilistic Flood Prediction Based on Implementation of the Schaake Shuffle Method over the Huaihe Basin

Zhao Linna, Liu Ying, Bao Hongjun, Wang Binyan, Bai Xuemei, Li Xiaomeng, Yang Ruiwen, Li Yitong

2017, 28(5): 544-554. DOI: 10.11898/1001-7313.20170503

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Abstract:
Daily precipitation records of 19 rain gauges over the Huaihe Wangjiaba-Dapoling catchment and single-value forecasts of 24-hour cumulative precipitation of the Global Forecast System (GFS) with lead time up to 14 days from 1 January 1981 to 31 December 2003 are employed to construct a probability forecast model which can generate ensemble forecast based on conditional meta-Gaussian distribution. Several single-value forecasts could be computed by this model using forecasts of the GFS for daily mean areal precipitation (MAP) and cumulative MAP for each lead time (1-14 days) over 3 sub-catchments in the Huaihe Basin. Then a method is implemented to reorder the ensemble output to recover the space-time variability in precipitation, namely Schaake shuffle method. Ensembles are then reordered to match the original order of the selection of historical data. Using this approach, the observed inter sub-catchments correlations, intervariable correlations, and the observed temporal persistence are almost entirely recovered. This reordering methodology is applied in recovering the space-time variability in modeled streamflow for twelve flood processes over the Huaihe Basin. Results demonstrate that the observation of discharge is included in the interval between the 5th percentage and the 95th percentage forecasts of discharge that is generated by MAP ensemble forecasts which is calculated from the conditional meta-Gaussian distribution model and Schaake shuffle. Several members can capture the flood peak flow and the corresponding peak time. Using approach of Schaake Shuffle, sub-catchment correlations of each ensemble member forecasting could be recovered, which are closer to the observation.A test of flood forecasting result from precipitation probability forecasts of conditional meta-Gaussian distribution model and Schaake shuffle for the stream between Dapoling to Wangjiaba Hydrologic Station is carried out. It shows that MAP ensemble forecasts can provide the maximum estimation of possibility of the future hydrologic events for flood forecasting comparing to the single-value MAP forecast of GFS model. And a comprehensive interval which includes the factor that can lead to hydrologic uncertainty is also given.

The Characteristic and Current Model of Radiation Impulse in Lightning Initial Preliminary Breakdown Process

Wu Bin, Zhang Guangshu, Wen Jun, Zhang Tong, Li Yajun, Wang Yanhui

2017, 28(5): 555-567. DOI: 10.11898/1001-7313.20170504

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Abstract:
Physical characteristics of the initial breakdown pulse has been studied widely, but the exact three-dimensional position of the initial breakdown pulse and physical characteristics of the maximum amplitude initial breakdown pulse are not understood deeply yet. Based on three improved transmission line models and particle swarm optimization algorithm, the bipolar pulse of initial preliminary breakdown process in different types of lightning at different distances is fitted by using high-precision lightning three-dimensional radiation source localization results and synchronization data of wideband electric field pulse waveform at Datong of Qinghai. The radiation field component is modified and the current waveform of initial streamer channel and characteristic parameters are derived. The fitting effect of three models on the bipolar pulse waveform of the initial preliminary breakdown process and step leader process are comparatively analyzed, and the physical feature of the initial breakdown pulse are statistically analyzed. At the same time, the bipolar pulse propagation mechanism and physical characteristics of the lightning initial pre-breakdown process are further studied.All three models can reasonably fit the measured bipolar waveforms. and it may be more reasonable that the current in the channel exponentially decays with height. The leader process and the initial preliminary breakdown process of the negative cloud-to-ground flash show cascaded developing, and both parameters using MTLE model fitting is close, indicating their transmission features are similar. The total amount of charge, total vertical dipole moment and the path length of the initial streamer upward propagating to positive charge region are larger than that of the initial streamer downward propagating to positive charge region. It may be related with the distance between the positive and negative charge region. When fitting the bipolar pulse waveform with three improved transmission line models, no model is constantly better than the other models, and it depends on specific analysis of the pulse structure. It should be noted that some of the initial pre-puncturing process bipolar pulse sometimes superimposed on the high frequency pulse, which may affect the fitting effect, but these pulses are considered inevitable product of the lightning discharge process. The presence of these pulses cannot be ignored when fitting. The wide-band electric field pulse waveform produced by lightning discharge is also distorted by the influence of environmental factors (mountains, trees, etc.) during the transmission process, which may cause the fitting effect of the pulse rising edge and the pulse end period not ideal, and therefore, synchronized electric field pulse waveform data in other observation stations can be selected for comparison and confirmation.

Contrastive Analysis of Lightning Characteristics Between Rainstorm Case and Hailstorm Case

Wang Tingbo, Zheng Dong, Zhou Kanghui, Zhang Yijun, Xu Liangtao

2017, 28(5): 568-578. DOI: 10.11898/1001-7313.20170505

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Abstract:
Two kinds of classic convective systems in and around Beijing are picked to investigate the lightning activities (observed by SAFIR3000) and the relationship between lightning and precipitation (retrieved from radar) during different thunderstorms. Lightning activity characteristics of a rainstorm and a hailstorm are analyzed and compared. Due to different microphysics and dynamic processes, there are significant differences in the discharge process within clouds, resulting in significant differences in corresponding lightning activities. The hailstorm has larger ratio of CG (cloud-to-ground) lightning, and the ratio of positive CG lightning is 0.311, comparing to 0.191 of the rainstorm.During the rainstorm, the intensity of convective precipitation is decreasing sharply when the lightning frequency reaches the highest value. The lightning frequency in this region can provide about 5-15 min warning time for the maximum rainfall intensity. In the early stage of hailstorm, rainstorm with short duration occurs, and the frequency of lightning reaches the peak when the hailstorm occurs, and then it declines as the hailstorm maintains. The hailstorm has larger ratio of CG lightning than the rainstorm. The main discharge area in hailstorm is higher than that in rainstorm, the temperature layer corresponded to the main charge region in hailstorm is lower than that in rainstorm. The total lightning frequency between convective precipitation's linear correlation coefficient is better in rainstorm than that in hailstorm.The linear correlation between lightning and precipitation in hailstorm is more complicated, because hailstorm has more complex dynamic and ice phase microphysics. These quantificational results can provide reference for applications of lightning data in severe weather warning and precipitation estimation.However, it's not certain whether all hailstorms have the similar lightning and precipitation relationships (the highest precipitation in the early stage of the hailstorms, and the total flash to reach the maximum in the hail stage). These results can be improved through further analysis when there are more observation cases.

Prediction Experiment for the South China Sea Summer Monsoon Strength by Physical-statistic Integrated Model

Zheng Bin, Li Chunhui, Lin Ailan, Gu Dejun, He Chao

2017, 28(5): 579-588. DOI: 10.11898/1001-7313.20170506

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Abstract:
The South China Sea summer monsoon (SCSSM) is a tropical system that plays a key role during the flood season of South China. However, the prediction of the SCSSM strength is difficult by no matter dynamic or statistic methods. Statistic methods are used in practice rather than dynamic model, but empirical-statistic models always have good hindcasting results during the period of building model, while the forecasting skills decrease evidently in practice. Physical-statistic methods have relatively stable predictive skill when the persistence of physical processes is taken into account. Therefore, an integrated technique is introduced based on associated physical processes to establish a predictive model for SCSSM. It is well known that the rainfall of SCSSM has multi-scale climate variability, for example, quasi-biennial and quasi-quadrennial time scale, which are mainly related to TBO (Tropospheric Biennial Oscillation) and ENSO (El Niño-Southern Oscillation), respectively. Based on the corresponding climatic factors, a physical-statistic integrated model is built. Combined with the traditional empirical-statistic method, a new prediction model (namely physical and empirical-statistic integrated model) for SCSSM is developed.First, original data are processed by removing the climatic state (1981-2010) and linear trend, and then anomalous data are filtered on the TBO (12-36 months) and ENSO (36-96 months) time scales since the biennial mode of SCSSM has little connection with the ENSO. Second, regressed results based on climatic factors (e.g., sea surface temperature anomalies in Niño3.4 and the tropical western Pacific, precipitation anomalies over the maritime continent and Australian monsoon region) are assembled according to a discrimination function that is correlation coefficient larger than 0.05 significant level between regressed results and the filtered SCSSM precipitation. Moreover, the rest precipitation with SCSSM inter-annual variations removed is predicted by the traditional empirical-statistic method and results are added to those by the physical-statistic integrated model. Using data throughout 1979-2010, the physical and empirical-statistic integrated model is trained and results of 2011-2016 are predicted for test, compared with that of the empirical-statistic integrated model. It shows that the new model has better prediction skill (9.5% improvements in prediction score and 75% in anomaly correlation coefficient) and relatively stable predicting results. More than that, the new model has some predictive ability for SCSSM rainfall distribution.

Impacts of the Regional North Polar Vortex Anomalies on Summer Precipitation of the Tarim River Basin

Li Hongjun, Ma Yufen

2017, 28(5): 589-599. DOI: 10.11898/1001-7313.20170507

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Abstract:
With precipitation data of 43 stations in the Tarim River Basin and the polar vortex areas data in the Atlantic-European (polar vortex) in summer of 1961-2015, variation characteristics of the precipitation and the polar vortex, the correlation and impacts of north polar vortex anomaly on precipitation in the Basin are studied. The precipitation in the Basin has been increasing since 1961, while the polar vortex is decreasing, and a significant negative correlation is found. In negative (positive) polar vortex anomaly years, in the upper atmosphere layer, the significantly weaker (stronger) subtropical westerly jet in West Asia and Central Asia, while it is the opposite in East Asia (35°-45°N, 120°-160°E) and the Basin, where the high-middle latitude cold air and mid-low latitude warm wet air that enter the Tarim River Basin increase (decrease) and strengthen (weaken). In the middle layer, negative (positive) polar vortex anomaly may lead to stronger (weaker) Middle European ridge and the Baike Lake ridge, weaker (stronger) East Asia trough, increased (decreased) meridional circulation in the Central Asian, and converging (diverging) stream in this basin. In the low layer, negative (positive) polar vortex anomaly may lead to stronger (weaker) anomaly easterly and southwesterly (northwesterly and northeasterly), stronger (weaker) weather disturbance. More east vapor flux is found entering the Basin comparing to the west vapor flux outflowing away this Basin. Moreover, the southern and eastern vapor flux converging in the southwest borders, and the convergence of vapor flux are strengthened (weakened) in the main precipitation areas of the Basin, which all lead to the increasing (decreasing) of precipitation in the Tarim River Basin.In summer, the polar vortex anomalies in the Atlantic-European have impacts on the meridional wind, zonal wind and the vertical motion from the high latitude to the low latitude by the meridional correlations. In the meridional range of the Tarim River Basin, the meridional variation distributions of the meridional wind, zonal wind and the vertical motion are formed from high latitudes to low latitudes by the zonal correlation, which are similar to those of the Atlantic-European, and anomalies of the wind field and the water vapor transition are also triggered in the Basin and its adjacent areas, impacting the precipitation. Therefore, the north polar vortex anomalies could possibly have significant denotative meaning on the Tarim River Basin precipitation in summer.

Impact of Wind Profiler Data on Regional Model Prediction in South China

Deng Hua, Liao Fei, Zhang Xubin, Shi Yang

2017, 28(5): 600-610. DOI: 10.11898/1001-7313.20170508

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Abstract:
Weather analysis demonstrates that upper-level jet, low-level jet, and wind shear are closely related with rainstorms and severe convections in South China. Wind profiler radar can continuously observe wind, making it the most direct resource of upper wind observation comparing with conventional observations. A network of observation stations with 18 wind profiler radars is built in Guangdong, data of which are assimilated every 3 hours in GRAPES_Meso model in real time, and the influence of wind profiler data is evaluated. A precipitation process in the pre-flood season of South China from 28 March to 9 April in 2014 is simulated through three designed experiments by GRAPES_Meso model. Results of assimilation trials show that wind profile data contribute a lot to analysis increment of zonal wind at levels from 1000 hPa to 850 hPa, especially at 850 hPa, and this effect rapidly diminishes above 700 hPa level. The root mean square error (RMSE) of forecasted variables at radiosonde stations are calculated in terms of sounding observations and the outcome of three experiments. Results show that profiler data mostly improve RMSE at 850 hPa, which announces a 0.7 m·s^-1 reduce of forecasted wind speed error, for 700 hPa level there's no evident improvement, and for 925 hPa level it becomes even worse. The same RMSE analysis is done at 12 wind profiler stations. The result is in accordance with radiosonde stations, which shows that the RMSE decreases at 850 hPa as well and the improvement is not evident at 925 hPa. The analysis indicates that the quality of wind profiler data is relatively better at 850 hPa. Results of two sensitive experiments for 1200 UTC 30 March 2014 is examined, revealing that the RMSE of the forecasted wind speed is even greater when wind profiler data are used in assimilation at locations of heavy rain grade or above. Besides, it seems that the RMSE of the forecasted wind speed also increases in the downstream direction of this heavy rain location. Causes of these two phenomena still need to be analyzed.

Ensemble Forecast Experiments of PM_2.5 Based on Multiple Boundary Layer Schemes in Tianjin

Cai Ziying, Yao Qing, Han Suqin, Hao Tianyi, Liu Jingle

2017, 28(5): 611-620. DOI: 10.11898/1001-7313.20170509

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Abstract:
Based on the atmospheric chemical model WRF/Chem, four kinds of boundary layer schemes (YSU, BL, MYJ and MYN3) are used to simulate the evolution of PM_2.5 mass concentration of Tianjin in 2015. Effects of different boundary layer schemes on the simulation and prediction of PM_2.5 mass concentration are analyzed, and a set of prediction products with various boundary layer schemes are constructed to improve forecast effects. Results show that the best boundary layer scheme for the near surface temperature simulation is BL scheme, the best boundary layer scheme for relative humidity simulation is MYN scheme and YSU scheme, the best boundary layer scheme for wind speed simulation is YSU scheme, and four boundary layer schemes of atmospheric chemical model have good applicability in simulation of air quality. The correlation coefficient between the simulated value and the actual value can reach 0.76, and the relative error is between 31.7% and 33%. Among four boundary layer schemes, MYN scheme leads to highest simulated boundary layer height, and the simulated boundary layer height of BL scheme is the lowest. As for the correlation coefficient between boundary layer height and PM_2.5 mass concentration, BL scheme is the highest (0.64), comparing to 0.62 with YSU scheme and MYJ scheme, and only 0.5 with MYN scheme. No single scheme has significant advantages. BL scheme is better in sunny and windy weather, while YSU and MYJ schemes perform better in cloudy and breeze weather. The simulated PM_2.5 mass concentration in Tianjin shows a significant disturbance characteristic with different boundary layer schemes. The standard deviation of daily average PM_2.5 concentration is about 5.2 μg·m^-3, accounting for 8% of the mean, and its maximum can reach 23 μg·m^-3. The hourly standard deviation reaches 11.8%, which is greater than the daily standard deviation, especially in the process of mutual transformation between stable boundary layer and unstable boundary layer. To overcome these problems, air quality ensemble prediction tests of multiple boundary layer schemes are carried out in Tianjin. Based on the analysis of forecast value in 2015, the ensemble prediction of multiple boundary layer schemes and disturbance of multiple aerosol mechanisms can decrease the relative error and root mean square error of PM_2.5 mass concentration prediction by about 25%. It can also reduce the false negative rate of heavy pollution weather from 44% to 30% and improve the forecasting capabilities of air quality level by 3%-6%. When the computing resources are sufficient, it is also an effective means to enhance the forecast ability of PM_2.5 mass concentration.

Research and Implementation of Remote Sensing Big Data Distributed Technology

Luo Jingning, Liu Liwei

2017, 28(5): 621-631. DOI: 10.11898/1001-7313.20170510

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Abstract:
In the past ten years, the global various digital information grows explosively, and a big data era with massive data production, sharing and application is opened. In this decade, with the development of information technology, distributed storage and computing technology get great development to deal with the explosive growth of information, and the knowledge system and technical reserves are established gradually. In China, research on big data and distributed computing is being carried out widely. For satellite remote sensing data of large volume and rapid growth, the traditional archive-callback-application cannot meet demands of data analysis and data mining in the era of big data.The traditional file-based way has many limitations, especially when used for cloud computing and in-telligent services, and it is very difficult to use. The big data grid model and distributed model is the key to solve the bottleneck, enabling real-time computing and on-demand services, and therefore it has important reference significance. It overcomes the temporal and spatial fragmentation problem, making the remote sensing data possible to be stored, calculated and applied as a whole. Based on the Hilbert curve grid hash algorithm, a distributed system containing fundamental structure of grid, time slice and physical layer is established, demonstrating excellent parallel read-write performance. Hilbert hash algorithm has stable discrete degree, which is the key for the grid model to maintain spatial correlation and to map two-dimensional space to one-dimensional sequence.Using the distributed system, instead of traditional way of data file organization and management, properties flexible and intuitive data acquisition are realized. Users can truly experience a new way of what you see is what you get and what you get is what you need to get. The future system which is based on the data model, will greatly increase the work efficiency, make the focus from the data itself to data applications. Internet-based cloud computing grid cell calculation can be realized, and the extension ability of the whole system can achieve linear growth, based on the general hardware and software platform. The implementation of this system will greatly improve the work efficiency, completing high-speed parallel data reading and writing, making on-demand data application more smoothly.

Design of CMA S2S Data Archive Center and Key Technology

Xiao Huadong, Sun Jing, Sun Chaoyang, Nie Yuanding, Zhao Chunyan, Guo Feng, Chang Biao, Zhang Xinnuo, Liu Liming

2017, 28(5): 632-640. DOI: 10.11898/1001-7313.20170511

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Abstract:
S2S, sub-seasonal to seasonal prediction project, is a WWRP/THORPEX-WCRP joint research project established to improve forecast skill and understanding on the sub-seasonal to seasonal time scale, and promote its uptake by operational centers and exploitation by the applications community. To achieve many of these goals, the establishment of an extensive data base of sub-seasonal (up to 60 days) forecasts and reforecasts (sometimes known as hindcasts) is advocated. Managing an extensive data base for the sub-seasonal time scale is a challenging task for the diverse characteristic of these forecasts (e.g., start dates, length of the forecasts, average periods, and updating frequency of forecasts).Open access to forecast data and user interface friendly data bases are important requirements for construction of S2S archiving data. CMA, one of two S2S data archive centers, is responsible for collecting S2S data from all data providers, performing basic quality check, archiving and storing data, and providing data service. The traditional FTP and a simple data downloading program based on ECMWF WebAPI is used to collecting data provided by all eleven S2S data centers. The data synchronization with another archive center of ECMWF is implemented by applying the combination strategies of common routine data transfer through FTP, ECMWF WebAPI based data download for missing reforecast data, and transferring missing real-time data copied from tapes directly by MARS system command. The file of compressed format TAR and GRIB2 is checked by executing command of tar and grib_get and its return value. A program based on the tigge_check command provided by GRIB_API is also developed to check the attribute of GRIB2 data, since all S2S data are saved as GRIB2 format. Through using GRIB_API command of grib_filter and designing a unified data form organized by a single center, a single date and a single meteorological parameter field, the unified S2S data are created to store in the online storage system which makes fast retrieval of data possible and open access. In the meantime, the unified form of S2S data file could be easily obtained their real storage addresses by their file names. The S2S data portal provides both free text and faceted search method to access forecast and reforecast data in the format of GRIB2 and NetCDF through online converting the data format.CMA S2S archive center is in operation since 15 November 2015. With the availability of data of all data providers, the construction of S2S archive center will be continued to improve the in-time of data integrity and data access methods.

Vol.28, NO.5, 2017