应用气象学报

The Heavy Rainfall Event Leading to the Large Debris Flow at Zhouqu

Qian Weimiao, Luo Yali, Zhang Renhe, Gong Yu

2011, 22(4): 385-397.

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Abstract:
Heavy rainfall occurs abruptly at Zhouqu, Gansu Province at night of 7 August 2010, causing disastrous debris flow and bringing about more than a thousand casualties. To find out the possible triggering mechanism of this rainfall, observations by Automatic Meteorological Stations are used to analyze temporal variation of the surface temperature and spatial distribution of rainfall; brightness temperature data from MTSAT satellite are adopted to reveal evolution of convective clouds; NCEP/NCAR 1°×1° reanalysis data are used to investigate the large-scale atmospheric conditions; AIRS satellite observations are examined to analyze the atmospheric instability; and ECMWF 0.125°×0.125° forecast data are employed to study the convection. First, over Zhuoqu and its upstream (northwest) region, the rapid increase of surface air temperature and the cold air advection in the rear area of the upper-level trough significantly enhanced the conditional instability in the morning of 7 August, favoring formation and development of deep convection. Second, several small-scale convergence centers and lines at the ground surface, generated by interactions among the southerly warm and northerly cold air flow near the ground surface and the complex terrain elevation, triggered the formation of the precipitating convective clouds around 14:00 7 August 2010 (Beijing Time). Third, the southerly air flow between the strong Northwest Pacific Subtropical High and the typhoon "Dianmu" changed to easterly at 23°—30°N, transporting water vapor toward the west until reaching the eastern side of Tibetan Plateau, and then changed to northward, supplying abundant moisture for the raining storm over Zhouqu and its upstream region. At last, the convective clouds moved toward southeast following the upper-level air flow, arrived at Zhouqu and produced heavy rainfall at night of 7 August, leading to the large debris flow at Zhouqu.Satellite remote sensing observations play an important role in the diagnosis of this synoptic process. The infrared brightness temperature (TBB) from the MTSAT satellite reveals the occurrence, development, movement and weakening of the convective clouds which directly produced the heavy rainfall at Zhouqu. The air column temperature and moisture data observed by the AIRS satellite around 14:30 7 August 2010 are used to analyze convective available potential energy (CAPE) and level of neutral buoyancy (LNB) height. The results indicate that atmosphere over Zhouqu—Qinghai Lake region is strongly unstable with the area-averaged CAPE of 4393 J·kg^-1 and LNB height of 16.54 km.

Formation Mechanism of the Snowstorm over Beijing in Early Winter of 2009

Ye Chen, Wang Jianjie, Zhang Wenlong

2011, 22(4): 398-410.

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Abstract:
Using a variety of high spatial and temporal resolution observation data, an in-depth observation analysis is carried out on the formation and development mechanism of a snowstorm case happened on 1 Nov 2009 over Beijing and notable by its nature of the most early winter snowstorm in the past 60 years in Beijing. It shows that the snowstorm occurs under the favorable large scale atmospheric conditions. The enhanced 500 hPa trough over East Asian region together with the low level occluded front in Taihang and Yan mountain areas of North China provided strong forcing for the snowstorm. The occluded front is a terrain-driven cold-style occluded front system due to the encounter of the low level (below 1500 m) northwest to southeast cold air with the Taihang and Yan mountains. The low level cold air turns its original moving direction into west, and results in the moisture feeding to the occluded front zone from two different directions (the Bohai Sea and the edge of the water vapor-rich region in southern China).It shows that the snowstorm is the result of the low level occluded front, and precipitation distribution of 1101 process in 2009 is decided by the eastward-tilting structure of the occluded front, and Beijing is just located in the favorable front zone (the east side to the top of surface occluded front). Because vertical structure (below 1500 m) of the occluded front is shallower than the classic occluded front developed from the typical frontal cyclone, the vertical motion of the snowstorm case is not very strong. Therefore, its precipitation distributes evenly with time but lasts about 15 hours (rain first then it turns into snow) with large amount of the accumulated precipitation. The observation analysis based on wind profile suggests that the occluded front weakens from its bottom to top, which is caused by the cold air invading to the mature occluded front zone starting from layers below 500—800 m and then extending upward.Furthermore, the diagnosis shows that the precipitation transits from rain to snow because the surface air temperature decreases to near freezing point rapidly. The mechanisms for the temperature drop are not the same in different stages of precipitation. Evaporative cooling of the rainfall is the main contributor to the temperature drop before snowfall (from 00:00 to 08:00 on 1 November), while the low-level cold air advection plays the key role for maintaining lower air temperature during the whole snowfall period from 08:00 to 14:00 on 1 November in 2009.

The Basic Climatic Features of Stratospheric Circulation Transition in Northern Hemisphere

Zhang Ling, Li Weijing, Chen Lijuan

2011, 22(4): 411-420.

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Abstract:
The basic climatic features of stratospheric circulation in Northern Hemisphere demonstrate different forms in winter and summer. In winter, the cold cyclone system and westerly winds prevail in high latitudes, while in summer the situation is the opposite. In terms of inversion of geopotential height gradient and zonal wind direction, a transition date index (TDI) indicating the change dates from summer to winter circulations in the stratosphere in Northern Hemisphere is defined by using NCEP/NCAR reanalysis daily data. Some statistic methods such as linear tendency, wavelet analysis, binomial coefficient smooth and Mann-Kendall are applied to analyze the inter-annual and inter-decadal features of the transition dates at all main levels in the stratosphere. Results indicate that in the stratosphere, with the height rising, the transition date becomes earlier and the summer circulation lasts longer. For instance, the earliest circulation transition in the stratosphere occurs at the height of 10 hPa and 20 hPa, and it shifts to 30 hPa in a short period. However, it takes longer for the transition to shift from 30 hPa to 50 hPa than that from 10 hPa to 30 hPa, which takes almost one month. The average onset date of the South China Sea Summer Monsoon (SCSSM) is one of the earliest dates in Asia Summer Monsoon (ASM) system and it is much later than the transition dates in stratosphere. Therefore, TDI can be used as a pre-signal for monitoring and predicting ASM. Furthermore, there exists an obvious regional difference in the circulation transition, among which the transition dates at each level in Siberia is the earliest and that is relatively later in Bering Sea and Greenland. The inter-annual and inter-decadal features of the circulation transition dates in Northern Hemisphere and the aforementioned three different regions are quite apparent, turning from late to early and then to late again in the past 62 years. Particularly the circulation transition date in Northern Hemisphere and in Siberia shares some similarities in inter-annual and inter-decadal variations, for example, the time variation shows significant fluctuations, and both have a transition peak in 1975. The transition dates in Bering Sea and Greenland also have the similar features, for example, the time fluctuation is relatively small. Moreover, circulation transition dates vary with the height and region, but they all have a quasi-2-year, a quasi-3-to-6-year, a quasi-9-to-12-year or a quasi-21-to-24-year cycle which may have close connections with other members of the climate system.

The Probability Distribution of the Maximum Amount of Daily Precipitation During 20 Days in Summer of the Huaihe Basins

Liang Li, Zhao Linna, Gong Yuanfa, Bao Hongjun, Wang Chengxin, Wang Zhi

2011, 22(4): 421-428.

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Abstract:
The daily precipitation records of 158 meteorological rain gauges over the Huaihe Basins make it possible to analyze the probability distribution, using gamma distribution of precipitation during the summer of 1980—2007 by distinguishing rainy days following a dry or wet preceding day over the years. Five precipitation rain gauge stations, namely Xixian, Fuyang, Shangqiu, Huaian, Lianyungang stations, are investigated as representative stations of five catchments, namely the upper stream of the Huaihe River, the part stream between Wangjiaba Dam and Bengbu Station of the Huaihe River, the part stream between Bengbu Station and Hongze Lake of Huaihe River, the Huaihe River downstream below Hongze Lake and the Yishu River watershed, to analyze their probability distribution respectively. Through the Kolmogorov-Smirnov (K-S) test and the comparison between the gamma distribution probability density function of the five representative stations and the sample frequency of the daily precipitation records, it is proved that gamma distribution function can be an adequate fitting to the probability distribution of the precipitation in summer of the rainy days following a dry or wet preceding day. The probability density function of gamma distribution, to a certain extent, overcomes the influence that the random oscillation of the samples caused to the estimation of daily precipitation probability distribution.The probability distribution of maximum daily precipitation in 1 to 20 days derived from gamma distribution function is reasonable. The curve of precipitation probability density of 1 day is monotonically decreasing which takes on the trend of reverse "J". The peak of probability distribution of the maximum daily precipitation in 10 days or 20 days tilts toward the side of large precipitation with the days increased.From the Huaihe Basin's probability distribution of the maximum daily precipitation more than 10 mm, 25 mm, 50 mm in 10 or 20 days, it indicates that the probability of the upper stream of the Huaihe River, the Huaihe River downstream below Hongze Lake, and the Yishu River watershed are evidently higher than the rest regions of the five catchments, which means that the maximum daily precipitation of these areas is more likely to be over 10 mm, 25 mm, 50 mm in 10 or 20 days.The high values of the probability of the maximum daily precipitation over 50 mm in 10 days locates in the eastern part of Yishu River watershed and the upper stream of the Huaihe River, while the high values of the probability of the maximum daily precipitation over 50 mm in 20 days locates in the junction of the downstream of the Huaihe River and eastern of the Hongze Lake, indicating large precipitation are more likely to occur in these areas. This approach can provide practical applications such as decision supports for the management of hydro-meteorological forecasting, agricultural, and water resources management.

Seasonal Partition Problem of MOS Forecast for Extreme Temperature in North China

Che Qin, Zhao Shengrong, Fan Guangzhou

2011, 22(4): 429-436.

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Abstract:
Aiming at seasonal partition problem of MOS (Model Output Statistics) forecast for extreme temperature, experiments are carried out in North China with cluster analysis method. A new seasonal partition way of MOS prediction equations for temperature is proposed on the basis of clustering results. The period from 11 February to 20 March and from 5 November to 4 December is defined as early spring and late autumn class; the period from 1 May to 30 September is defined as summer class; the period from 21 March to 30 April and from 1 October to 4 November is defined as late spring and early autumn class; the period from 5 December to 10 February is defined as winter class. The proposed seasonal partition is significantly different from traditional seasonal partition especially on periods of time from March to May and from September to November. The two kinds of seasonal partition definition are compared and analyzed. MOS prediction equations with new seasonal partition are founded by T213 model data, maximum and minimum temperature data of 154 stations in North China from 2003 to 2008, and verification of extreme temperature forecast in 2009 is conducted.Mean absolution error of maximum temperature forecast from September to November and minimum temperature forecast from March to May and from September to November made by new seasonal partition is less than that by traditional one. Using the new seasonal partition, there are more stations with the absolute error of MOS forecast less than 2℃ for maximum and minimum temperature from March to May and from September to November. Average error of extreme temperature forecast based on two kinds of seasonal partition ways doesn't have great differences, and their absolute error also isn't large at the same time. It shows that the system error is not significant. However, compared with traditional MOS forecast, mean absolute error of maximum temperature forecast made by new seasonal partition from March to May is larger. The cause maybe relates with great changes of temperature in spring of 2009 or cluster analysis program. More study and improvement will be carried out in order to solve the problem. The test result indicates that the overall effect of MOS forecast for maximum and minimum temperature made by new seasonal partition way is better than the traditional one, and shows that the new seasonal partition way is more suitable for MOS extreme temperature forecast.

The Change of Growing Season of the Vegetation in Huanghe-Huaihe-Haihe Region and Its Responses to Climate Changes

Chen Huailiang, Liu Yujie, Du Zixuan, Liu Zhongyang, Zou Chunhui

2011, 22(4): 437-444.

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Abstract:
Using the each ten-day data of NOAA/AVHRR from 1981 to 2000 and adopting the Maximum-Slope method, Curve-Fitting method and stepwise regression, the beginning and ending of the growth season of the vegetations in the Huanghe-Huaihe-Haihe (HHH) region are analyzed. Meanwhile, the pixel by pixel I_NDV map is worked out with typical bands as the sample. Through analyzing the change of green wave and brown wave, the changing rules of vegetation activities and its responses to climate changes in the past 20 years are revealed. The growth season in HHH region starts at the last 10 days of March with I_NDV 0.19604 and ends at the first 10 days of November with I_NDV 0.22899 on average. The tendency is that the growing season has prolonged obviously by starting earlier and earlier, while ending later and later from 1982 to 2000. The average I_NDV for the vegetation in the researched area in the past 20 years is generally increasing, especially in spring. According to the I_NDV map of typical bands as the sample worked out with the pixel by pixel, the green wave changes from south to north during January—July on the band of 116°E, the maximum of I_NDV occurs in August and decreases gradually after September. On the band of 36°N, to the east and nearby 116°E, the I_NDV has two peaks because of two crops a year, which is obviously different from other regions. The two peaks occur in April and August and they become clearer and clearer from 1982 to 2000, especially in agriculture area. However, the two peaks are not obvious to the north of 38.5°N, in the area of Beijing, Tianjin and the mountain areas, and the peak value of early summer is lower than that of autumn. In agriculture area, the peak interval of green wave is broadening with the time passing by, and it's more obviously from south to north. With the time passing by, the green wave of the critical value of the growth season in the area changes from south to north, while the emergence of brown wave prolongs from north to south. According to the stepwise regression result of the every ten-day meteorological data and the I_NDV of the typical sampling areas in the HHH region, the I_NDV of vegetation is closely related to the temperature and precipitation, especially it's more sensitive to the temperature, and the significance of the correlation is 0.01. The prolonging of vegetation growth season is a main response to climate changes of vegetation activities in target areas.

The Soil Moisture Predictive Model Based on the Precipitation in North China

Wang Shanshan, Han Lijuan, Cui Hengjian, Yang Hua

2011, 22(4): 445-452.

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Abstract:
A better soil moisture predictive model for North China can enhance the accuracy of drought forecast, which will have great significance in predicting the extent and distribution of drought, playing an important role in taking positive and active measures for drought in time. It is well acknowledged that one of the key points and difficult points in research on dry farming is the change of soil moisture, which is influenced by various factors, such as rainfall, evaporation, the time of sunshine, the kind and texture of soil and so on. Of all the factors, the amount of rainfall is one of the most important factors, which contributes a lot to the change of the soil moisture, deserves more and more attentions to study their relationships.A random variable's mechanism-rational model is therefore introduced, and the meteorological data in North China during 2000 to 2008 is analyzed, taking the atmosphere precipitation as random variable as well as its delay effect, employing the regression method to set up the soil relative moisture predictive model, which is effective for ten days. 10-cm and 20-cm soil relative moisture predictive models for the 55 stations in the north of China are established, but only the fitting results of 10 stations are given, and their fitness accuracy (the Pearson correlation coefficient) is all above 60%. Meanwhile, the efficiency of this model is verified with soil moisture data of 2009 by means of the two indexes, indicating that all of the forecasting rates are above 90% and most of the drought prediction rates are above 70%, therefore a series of objective, dynamic soil moisture predictive method is established. The fitting graphs and the graphs of 95% confidence interval are also given for the 10 stations, from which the feasibility of this method can be verified. The method provides a new support for the prediction of the soil moisture in the field.The method can extend to every station in the country to set up local unique models. Though this approach is only tentative experiment, it is a success according to the results of fitting and prediction. Moreover, the model involves 10-day rainfall delay effect, whose prediction is effective for 10 days. With the extension of rainfall stations in the country, it is easier to get the daily observations of the rainfall, and it is possible to conduct continuous prediction for the soil moisture with the method, which will have far-reaching influence on the dry farming research.

The International Radiosonde Intercomparison Result for China-made GPS Radiosonde

Li Wei, Zhao Peitao, Guo Qiyun, Wang Mian

2011, 22(4): 453-462.

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Abstract:
Based on total 29 groups observation data of the 8th WMO International Radionsonde System Intercomparison, using the same balloon releasing method and mainly choosing Vaisala radiosonde measurements as relative reference standard, the systematic evaluation for Changfeng China-made GPS radiosonde system and Huayun China-made GPS radiosonde system is carried out including typical examples analysis and statistics analysis. The initial evaluation results show that for temperature observation, the value of both domestic radiosonde is higher compared to Vaisala radiosonde. The relative systematic error of Changfeng radiosonde is within 0.4℃ and standard deviation is within 0.7℃, the Huayun radiosonde owns similar performance, but its error obviously increases. For humidity observation, the observation data of Changfeng radiosonde below 16 km basically show dry trend compared to Vaisala radiosonde, and below 12 km humid trend for Huayun radiosonde. Below 14 km the relative systematic errors for Changfeng radiosonde and Huayun radiosonde can be within 4% and 6%, respectively, and above 14 km the relative systematic errors obviously increase, reaching 12% and 20%, respectively, and the standard deviations for gradually show increasing trend from surface to tropopause and can reach 14% and 17%, respectively. For pressure observation the relative systematic errors and standard deviations for Changfeng radiosonde and Huayun radiosonde is smaller compared to Vaisala radiosonde, the relative systematic errors show the similar trend that negative values occur in low layer and positive values in upper layer, and the standard deviations show decreasing trend from surface to upper layer. The absolute value of minimal relative systematic error minus maximal relative systematic error is within 1 hPa and maximal standard deviation is 1.2 hPa for surface point, assuring the accurate geopotential height calculation and correct pressure retrieving algorithm. For wind observation the relative systematic errors and standard deviations for Changfeng radiosonde and Huayun radiosonde is smaller compared to Vaisala radiosonde, and the analysis results show excellent GPS positioning function and correct wind calculation algorithm. It can be concluded the domestic radiosonde has reached advanced level except for the humidity element. In future, more improvements should be made on temperature observation above 30 km and humidity observation under low temperature.

May—July Temperature Variability Since 1801 Inferred from Tree Rings of Pinus tabulaeformis of Helan Mountains in China

Chen Feng, Yuan Yujiang, Wei Wenshou, Zhang Tongwen, Zhang Ruibo, Yu Shulong, Fan Ziang, Li Yang, Shang Huaming

2011, 22(4): 463-471.

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Abstract:
Ninety newly measured tree-ring width and density series from Chinese Pines (Pinus tabulaeformis) from four sites in Helan Mountains are compiled. To remove non-climatic, age-related growth trends from the raw tree-ring width and density measurement series, while allowing lower frequency information above the mean segment length to be preserved, the program ARSTAN is used to detrend the ring width and density sequences using hugershoff growth curve and to average the standardized ring width and density sequences into the master chronologies. The correlating coefficient between earlywood density record and May—July maximum temperature of Yinchuan reaches up to 0.67 during 1951—2008. The May—July maximum temperature reconstruction (1801—2008) uses the earlywood density chronologies from the region. The explained variance of model is 44.9% (F=45.625, P < 0.0001). The mean temperature over the 1801—2008 periods is estimated to be 27.4 ℃. The reconstructed temperature has 3 warm periods, including 1801—1812, 1940—1953, and 1994—2008. The rising of temperature series in the 2000s is the fastest and indicates that temperature in the 2000s has been warmer than any other period since 1801. The reconstructed temperature during the last 208a has significant period cycles of 120 years (95%), 8.1 years (95%), 6.5 years (90%), 3.2 years (95%), 2.9 years (95%), and 2.1 years (99%). Many low density values are forced by volcanic eruptions. Comparison shows volcanic eruptions have no systematic relationship with this reconstruction data, but they are correlated with the regional characteristics of the temperature and forcing data. Detailed analysis, however, suggests a cooling of several years following primarily tropical events with a volcanic eruption index (VEI). Examples include Tambora in Indonesia (1815), Cosiguina in Nicaragua (1935), Chikurachki in Kurilels (1853), Sheveluch in Kamchatka (1854), Krakatu in Java (1883), Okataina in New Zealand (1886), Santa Maria in Guatemala (1902), Ksudach in Kamchatka (1907), Katmai in Alaska (1912), Bezymianny in Kamchatka (1956), Agung in Indonesia (1963), St Helens in US (1980), El Chichon in Mexico (1982), and Pinatubo in Philippines (1991). The mean of 28 low values after volcanic eruption in reconstructed temperature series is 26.9℃, which is 0.5℃ lower than the average over the 1801—2008. The earlywood density of Helan Mountains has good relations with the earlywood densities of Shimen Mountains and Changling Mountains in Gansu.

The Impact of Assimilating Sea Surface Wind Aboard QuikSCAT on Sea Fog Simulation

Liu Yudi, Ren Jingpeng, Zhou Xin

2011, 22(4): 472-481.

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Abstract:
Sea fog is a kind of disaster weather with strong local characteristics. It has brought more serious losses as people's activities over the sea become more frequent. Therefore, the forecast of sea fog is becoming more and more important. There is no effective method to directly and widely obtain the real data of meteorological fields over the sea at present. However, the microwave scatterometer aboard a satellite is the most popular sensor that provides accurate global sea surface winds which are used widely. At the same time, the progress and popularity of variational assimilation method also make a great deal of unconventional data be used in numerical models, which optimize initial condition of models.To evaluate the impact of assimilating the sea surface wind data aboard QuikSCAT on the sea fog simulation, 3 sensitive experiments are carried out for the sea fog process during 3—5 April 2006. The effect of the different boundary layer parameterization schemes, such as Medium Range Forecast Model (MRF), Yonsei University (YSU) and Mellor-Yamada-Janjic (MYJ) on sea fog simulation are discussed. It is found that YSU boundary layer physical parameterization scheme is more suitable for simulating sea fog, the MRF scheme takes the second place and the MYJ scheme is the worst. Then by the three dimensional variational data assimilation (3DVAR) method based on the Weather Research and Forecast (WRF) model the sea surface wind aboard QuikSCAT is assimilated to investigate an advection fog and a radiation fog occurred over the sea around China, respectively.The results with and without assimilating the QuikSCAT sea surface wind data are used as the initial fields for WRF model to simulate the sea fog, respectively. The simulated results are compared with the satellite nephogram and the ground observation. Preliminary results show that the three dimensions variational assimilation of sea surface wind data by WRF-3DVAR system can make the sea surface wind data affect other element fields at low levels of the model, which have an obviously positive impact on the area forecast of sea fog. In particular, some detailed results are obviously better compared with those of the control experiment without assimilating the sea surface wind data. But for high levels the impact is limited. Since the sea fog data are sparse, results of only two cases are insufficient to generalization, so more cases will be discussed to validate the conclusions in the future.

Estimating Background Error Covariance in Regional 3DVAR of WRF

Wang Man, Li Huahong, Duan Xu, Liu Jianyu, Fu Rui, Chen Xinmei

2011, 22(4): 482-492.

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Abstract:
In order to explore the statistical structure of background error covariance ( B ) and its impact on initial field and three-dimensional variational data assimilation system, based on day by day WRF model forecast data from May to October in 2008, B is estimated using NMC method. The statistical structure of B is analyzed and validated with single ideal experiment, showing that it can reasonably reflect the geostrophic balance relationships and the relationships among multivariable in middle and lower latitudes. The characteristics of B structure are presented as well.A B file provided in three-dimensional variational data assimilation system, it is a generic background error statistics file called CV3- B that can be used for any resolution or area case. The CV3- B is the NCEP background error covariance, which is estimated in grid space by the NMC method. The statistics are estimated with the differences of 24 and 48-hour GFS forecasts with T170 resolution valid at the same time for 357 cases distributed over a period of one year. The major differences between these two kinds of B are the vertical covariance. CV3- B uses the vertical recursive filter to model the vertical covariance but the modified B uses the empirical orthogonal function (EOF) to represent the vertical covariance. In order to compare the difference of the two B in detail, a simulation experiment for June 2009 with two different B are performed to comparatively analyze the initial fields and precipitation distributing of strong rainfall case, and test the simulation effect in a month precipitation. The results show that different B lead to great differences in data assimilation processes. With the same background fields and observation, the minimizing convergence standards are equal to 0.01, the iterative step is about twenty using updated B , while the iterative step is about forty using CV3- B .And using updated B , for most instances it's monotonic decreasing during the iteration except for few iterative steps, and the decrease velocity is more rapid. But using CV3- B the value fluctuates from time to time. From data assimilation process, the efficiency in the iteration is higher using updated B , and the convergence of object function is steadier. The heavy rainfall process triggered by shear on 30 June 2009 in Yunnan Province is selected to analyze the effect of using different B on initial fields and precipitation distribution.Assimilating the sounding data of Tengchong in the west of Yunnan Province, the increment fields of wind vector on 700 hPa is analyzed. It is found that the increment impact spreads to the whole Yunnan Province using CV3- B , which is unreasonable. Using modified B the increment impact is within the adjacent area of the shear, leading to a relatively reasonable result. The precipitation simulation also indicate that using updated B which is consistent with model fields and all kinds of parameter, the TS in moderate rain or over is higher than using CV3- B .The whole simulating effect using updated B is remarkably superior to that using CV3- B . Thus estimating B afresh is important when three-dimensional variational data assimilation system is applied.

The Impact Factors and the Phenological Variation of Elymus nutans in Maqu Meadow

Wang Jianbing, Wang Zhigui

2011, 22(4): 493-497.

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Abstract:
Maqu county is located in the southwest of Gansu Province, on the northeast of the Qinghai-Xizang Plateau. Maqu meadow is the core region of the important water source supply area of the Huanghe River, having unique significance in the water and eco-environmental security of the Huanghe River basin. A lot of remarkable results in the variation of Maqu meadow are achieved from the perspective of climate and eco-environment, but phenological variation of the pasture grass in Maqu meadow isnts paid enough attention. Based on the growing data of Elymus nutans (1985—2005) at the agricultural meteorological station of Maqu (102°05′E, 34°00′N, sea-level elevation 3471.4 m) and the simultaneous observation meteorological factors (such as temperature, precipitation, sunshine duration, etc) at the same place, the relationship between the Elymus nutans phenological variation and the meteorological factors is studied, providing reference for the research on eco-environment variation of Maqu meadow.In recent 20 years, the Elymus nutans recovery date of Maqu meadow shows a delaying trend with the tendency ratio of 1.6 d/10 a, but the date of ear, bloom, maturate and withered show obvious advancing trends with the tendency ratios of 4.9 d/10 a, 8.0 d/10 a, 13.9 d/10 a and 1.3 d/10 a. The reducing of autumnal precipitation is main impact factor to delaying tendency of recovery date. The rising of summer temperature results in the advancing trend of Elymus nutans ear, bloom and maturate date in Maqu meadow, and the warming and drying trend of autumn is the main impact factor of the advancing Elymus nutans. The impact of these phenological changes on the Elymus nutans quality, yield and the quality of seeds need further research.Compared with Elymus nutans, the observation duration of other grass is less in Maqu meadow, so their phenological variation is not analyzed, which requires further research. Besides, the impact of the grass phenological variation on animal husbandry and eco-environment in Maqu meadow need further study too.

Meteorological Information Publishing Platform Based on ArcGIS Server and VML Technique

Zhang Yonghua, Xiao Wenming, He Wanwen, Sun Zhoujun

2011, 22(4): 498-504.

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Abstract:
In recent years, more extreme weather phenomena have caused great damages on people's lives and property. In order to guarantee the accurate quick society service of the weather information, the establishment of meteorological information platform is imperative.The system is developed using ArcGIS Server platform with ArcSDE, Oracle, combined with ASP.NET, VML, Ajax and other technologies. By integrating real-time weather information into actual GIS environment, the system delivers the basic operation of the map, the inquiry of dynamic information, and the visualization release of various statistical charts. Meanwhile, it will provide analysis of surface rainfall and typhoon affected area, by making full use of the GIS spatial analysis capabilities. When facing various complex weather, it shows the forecasters with a variety of weather information visually and quickly, supporting the decision-making, and it also provides better and more effective meteorological service for the public.The system consists of four layers. The first layer is the data storage layer, including the basis of meteorological data and geographic service data, which are stored in Oracle 10.2 database and ArcSDE for Oracle spatial database respectively. The second layer is the data service layer, including attribute and spatial data services, achieved by ArcGIS Server map services combining with the application services of DOTNET. The third layer is the business logic layer, it provides specific business logic processing and organization in accordance to client requests, achieved by the business module. The fourth layer is the clients' presentation layer, it provides all kinds of weather information dynamically and instantly through a friendly browser interface. The new techniques of Web 2.0, including EXT script libraries, Ajax and so on, bring the user new experience.ArcMap is introduced to manage mxd files and configure map document. Typhoon path displaying and buffer analyzing are based on the VML and ArcGIS Server interface. Contour surface rainfall analysis results can be overlaid with the raster of administrative map. Other key techniques include map services publishing, map cache generating, system deploying and load balancing, and so on.At present, this system has been on trial for more than one year in the Guangdong Provincial Meteorological Bureau, and has provided rich data for forecasters and other meteorologists. In particular, real-time data contour analysis, surface rainfall analysis, typhoon path buffer analysis and the raster overlay analysis of typhoon affected areas based on Geographic Model, have provided scientific basis for forecasting and decision-making, which is exactly the innovation of this system. Meanwhile, various statistical charts and diagrams of spatial analysis are great helpful to researchers. In addition, a variety of analysis charts can be used to check observation data, identify the site of wrong data quickly and amend the error in time. Based on user feedback, the system is under constant improvement.

The Design and Implementation of Provincial Meteorological Information Sharing System

Ma Yuyong, Xu Xiaoli, Song Zhi, Wu Wei, Jiang Yong

2011, 22(4): 505-512.

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Abstract:
Meteorological information plays the fundamental role in weather forecast and meteorological service. With the rapid development of meteorological observing system and numerical weather prediction model in the last decade, the types and amount of the meteorological information, including observation data and forecast products, increases enormously. The traditional meteorological information management and sharing system can not fully meet the requirements of meteorological operation and service. To address the growing demand of meteorological operation and service, a new model of provincial meteorological information management and sharing system is proposed. The model is mainly made up of two parts: The relational database and the message-oriented middleware.The database manages integrated meteorological information from both observation and model outputs. Due to different data encoding mechanism, meteorological information is divided into two categories. The first category is decoded to meteorological element data and stored in two-dimensional data tables of the database. The other one is stored in a special storage area in file form and its file index table is managed by the database. So the database can provide the meteorological information sharing service in both file-level and element-level.The middleware provides flexible and high-performance access to the database. It is compatible with a variety of development environment and programming languages. The middleware also takes full advantage of indexes in the database, and protects the database by automatically generating and submitting SQL statements for the application software. The advantages of the meteorological information sharing system are as follows: The system manages a mass amount of meteorological data in an intensive way. The meteorological information in the database is retrieved exactly and efficiently by utilizing some technologies, such as metadata. The middleware of the system implements a more open, more efficient and safer access to the database.The meteorological information management and sharing system in Sichuan Province is developed in accordance with the model. The Oracle 10g is installed as the core database and IBM Websphere MQ, a message-oriented middleware with further developed library, is used as the access interface to the database. A series of applications developed upon the sharing system have been put into operation in recent years all over the Province, and have played extremely important roles in weather forecasting and meteorological service, especially in flood seasons service and emergency service.In practice, it's proved that the model of provincial meteorological information management and sharing system not only improves the internal quality of meteorological information management, but also the meteorological information sharing service in all round way. The model can meet the requirements to manage and share meteorological information for the provincial meteorological service. Therefore, this model can be used as a reference in designing of the provincial meteorological information management and sharing system.

Vol.22, NO.4, 2011