应用气象学报

Vertical Structure of Convective Cloud in a Cold Vortex over Northeastern China Using CloudSat Data

Zhong Shuixin, Wang Donghai, Zhang Renhe, Liu Ying

2011, 22(3): 257-264.

[FullText HTML] (1002) [PDF 5228KB](1512)

Abstract:
Cold vortex (or cold low, also called cut-off low), characterized by a cold core and low pressure center over 500 hPa level, is one of the most frequent weather systems over Northeast China. It is often accompanied by strong convective incident, and can bring a wide range of continuous rainfall. However, most of the past researches mainly focus on the environmental conditions and large scale of the cold vortex systems. There is little analysis on meso-scale structure of the convective systems of cold vortex, especially using satellite and radar data, and the understanding on the vertical structure of the meso-scale convective systems is limited. CloudSat data, NCEP reanalysis data and visible light satellite data has been used to analyze the convective rain bands and meso-scale cloud structure of different stages of a cold vortex over Northeast China during 20—24 July 2006.The results show that at the beginning of development stage, the structure of the warm front is characterized with isolated and deep convective systems. At the development and matured stage, the intensity of radar echo is weaker than its development stage, and the convective systems are shallow. The echo top of occlusion under the cold vortex system presents some special characteristics: In the southeast of occlusion, the echo area is driven by the cold-dry air; in the middle area of occlusion is the main convective system and in the northwest area echo is caused by the lifting effect of warm front confront the cold front. There is delamination between ice water and liquid water at the tail of the occlusion front. The height of incursion layer of dry-cold air is about 5 km, above which is the weak echo consisting of ice water, and below the incursion layer is the echo with liquid water. At the mature stage of the cold vortex, the convective systems are located mainly outside the cold vortex in the form of isolated convective systems. Convective systems which contains plenty of ice water content are mainly located in the north of the cold vortex, while liquid water content exists below the 0℃ layer of the cold vortex center.

Low Frequency Oscillations of Southern Hemispheric Critical Systems and Precipitation During Flood Season in South China

Zhang Ting, Wei Fengying, Han Xue

2011, 22(3): 265-274.

[FullText HTML] (893) [PDF 5019KB](1163)

Abstract:
By using daily precipitation data over South China and the NCEP/NCAR daily mean reanalysis data of SLP in Southern Hemisphere during 1960—2008, the low frequency oscillations of Southern Hemispheric critical systems and precipitation during raining seasons in South China are investigated by means of statistical method, for example, MTM-SVD, and so on. The LFV spectrum results show a 30—60 days low frequency oscillation and variation of 5—7 days for the precipitation during raining seasons in South China. Australian high in Southern Hemisphere can also be decomposed into 30—60 days low frequency oscillations, 10—20 days bi-weekly oscillations and variations of 5—7 days and 2—3 days. Mascarene high has 30—90 days low frequency oscillations and characteristics of bi-weekly oscillations. The MTM-SVD method can identify coupled spatial and temporal evolving signal by using both phase and amplitude information. Tracking the spatial and temporal coupling evolution of low-frequency oscillation with 30—60 days, it is found that the Mascarene and Australian high from strong to weak is corresponding to the rainy zone transfer from southwest to northeast in South China, and vice versa. South rain belt of precipitation in South China coincides with the variations and phase of the Mascarene and Australian high very well, but North rain belt is opposite with the Mascarene and Australian high. When the SLP of Mascarene and Australian high are positive from the usual, southern rain belt in South China is usually strong and northern rain belt tends to by weak, and vice versa.

The Patterns of Anomalous Climate and Their Pre-circulation Signals in November

Yang Xiaobo, Wang Yongguang, Liang Xiaoyun

2011, 22(3): 275-282.

[FullText HTML] (867) [PDF 3084KB](1141)

Abstract:
Based on the stationery data of temperature and precipitation of 160 stations in China in November, the reanalysis data of 500 hPa geopotential height (GPH) of NCEP/NCAR, the four circulation patterns corresponding to the warm and wet, warm and dry, cold and wet, cold and dry in the monsoon regions over eastern China are analysed, and the previous and corresponding circulations are inspected with t-test method. The time series of positive station numbers about the temperature and precipitation are labeled as S₁ and S₂ respectively after removing long-term trend more than 9 years. Then the typical years according to the cold, warm, dry and wet patterns could be acquired by using the values of S₁+S₂ and S₁-S₂. In detail, the larger values of S₁+S₂ are defined as the warm and wet years, and the smaller values are defined as the cold and dry years. Meanwhile, the larger values of S₁-S₂ are represented as the warm and dry years, and the smaller values are represented as the cold and wet years. The results are as follows: The warm (cold) pattern takes on the inactive (active) blocking high over Ural Mountain and zonal (meridional) circulation prevails at middle and high latitudes. The dry (wet) type is corresponding to the weak (strong) and eastward (westward) of subtropical high in western North Pacific. The circulation difference of warm and dry pattern minus cold and wet pattern in t-test is in meridional direction, similar to the EU pattern. The circulation difference of warm and wet pattern minus cold and dry pattern in t-test is in zonal direction, similar to the anti-PNA pattern. The pentad running-mean of monthly circulation has significant differences for the warm and dry (cold and wet) type in the beginning time on 6, 11, 16 September and warm and wet (cold and dry) type in the beginning time on 11, 16 and 21 September which indicate that the previous circulation has significant implication for climate prediction. The characteristics of cold and wet (warm and dry) type are as below: On one hand, the GPH is high (low) at high latitude and low (high) at middle and low latitudes, and meanwhile AO is negative (positive), leading to low (high) temperature over northern China; on the other hand, the GPH is low (high) at the Qinghai-Tibet Plateau, and the active (inactive) southern branch trough induces the more (less) precipitation.

Characteristics of Surface Air Temperature Anomalies in China Based on Observations at 160 Stations

Zhou Guohua, Wang Panxing, Luo Xiaoli, Xie Yaoyao

2011, 22(3): 283-291.

[FullText HTML] (942) [PDF 1521KB](1330)

Abstract:
Three basic characteristics of seasonal and annual surface air temperature anomalies are analyzed by use of 160-station homogeneity adjustment scheme of China (Wang Panxing, et al, 2011) and conventional statistic methods.Anomalies in winter are the largest among the four seasons, occupying 47.7% of the total variance. Three north districts (namely Northwest China, North China and Northeast China) and the Tibetan Plateau are high variability regions in winter, with three north regions and the middle and lower reaches of Yangtze River for summer.The variance contribution of the linear warming of seasonal and annual anomaly is significant, and there are distinct differences between winter and summer. Significant annual and winter linear warming occurs in Northeast China, North China, northwest of Xinjiang and southwest of Tibetan Plateau. Weak linear cooling is observed for several stations of central and South China. The significant warming in summer is mainly located in the north of Northeast China, north of North China and Tibetan Plateau, but the range and strength are obviously less than those in winter. There is a large range cooling zone in the northwest and southeastern in summer.The variance contribution of interdecadal changes for annual, winter and summer anomalies is significant, and there are obvious differences between winter and summer. The significant interdecadal changes for annual surface air temperature in three north regions, most part of Tibetan Plateau, central China and part of East China are related to winter, while the southeast coastal areas is related to summer.Annual and seasonal mean surface air temperature calculated by network homogeneity adjustment in China is reasonable. The linear warming tendency for the national annual temperature is 1.4℃/58 a, with the maximum of 2.3℃/58 a for winter and the minimum of 0.6℃/58 a for the summer. The interdecadal changes of summer surface air temperature persists positive since the middle 1990s, while for winter and the whole year, stable warming has begun since the middle 1980s.

Diurnal Evolution of the Urban Boundary Layer Structure During a Snow Process in Urumqi

Han Xi, Wei Wenshou, Liu Mingzhe, Wang Minzhong

2011, 22(3): 292-301.

[FullText HTML] (986) [PDF 4527KB](1812)

Abstract:
For the purpose of studying the boundary layer characteristics in snowy day and non-snowy day of Urumqi, 20 times of continuous observations from 11 to 13 in January 2008 and 12 times non-snowy day's observations from 21 to 23 in January 2008 are conducted based upon the Vaisala tethered balloon in the middle of the city. The detecting elements include temperature, dew point, wind speed and wind direction etc. The potential temperature and depression of the dew point isoline and wind profile are studied for investigating the characteristics of the boundary layer and the influence of warm advection and snowing on the boundary layer.The convective boundary layer (CBL) is very typical with clear ultra-adiabatic lapse layer, mixed layer (ML) and capping inversion layer (CIL) in the daytime, and there tends to be a surface inversion during the nighttime. In fact, the temperature stratification isn't affected much by snowing. When the warm advection invades, an intense surface inversion occurs in the daytime, but it's still weaker than that in the nighttime. Furthermore, compared with the nighttime, the temperature inversion is even fiercer when warm advection approaches.In the CBL, vapor is blocked at the bottom of the CIL, forming a wet center, as height increases, vapor decreases to form a dry center. The height of the wet center in the snowing day is lower than usual. Under the influence of warm advection, large area of wet center appears near the ground surface. In the evening, weak humidity inversion occurs in the surface layer, besides, the upper layer has an obvious dry center.Although wind direction is dispersed in the surface layer, the main direction still can be estimated as "N". It changes by clockwise or anti-clockwise from the surface layer to the higher layer, the main direction in the upper air is "SE". The wind speed follows the "high-low-high-low" rule at certain heights, and the extreme speed appears at the height where wind direction shifts. In conclusion, wind speed tends to rise by fluctuates with wind direction shifts.

A Circulation Index Reflecting the Monsoon Precipitation of South China

Yao Cai, Qian Weihong, Lin Zhenmin, Liu Hexiang

2011, 22(3): 302-311.

[FullText HTML] (941) [PDF 2458KB](1698)

Abstract:
The South China monsoon precipitation and the monsoon over South China attract much attention. Using the NCEP reanalysis data and precipitation data of stations and grid, the relationship between the South China monsoon precipitation and atmospheric circulation are analyzed, and then a monsoon index of South China which can reflect the intensity of South China monsoon precipitation in June is established. The monsoon index of South China is defined based on the difference of 850 hPa vorticity between the subtropical Northwest Pacific near the Philippine Islands and the South China area. Then the relationship between this index and the South China monsoon precipitation are explored. The results indicate the monsoon index of South China has very good regional representative, the positive correlation coefficient between the monsoon index of South China and grid daily precipitation of Asia is mainly located in South China. The monsoon index of South China could fairly describe the inter-annual variability and extreme year of the precipitation. When the monsoon index of South China is stronger (weaker), the precipitation of South China is more (less) correspondingly, and extreme of the monsoon index of South China also means the extreme of precipitation. The difference of the precipitation over South China between high and low monsoon index of South China is significant at 0.01 level. On inter-decadal scales, the decade in which the monsoon index of South China is stronger (weaker) is also the decade in which the precipitation of South China is more (less).The relationship between the monsoon index of South China and the atmospheric circulation are also studied. The results indicate that the monsoon index of South China also includes the information of the important influencing systems such as southwest monsoon, the Pacific Subtropical High, the westerly trough over the middle-high latitudes, and so on. In the southeastern part of South China, there is abnormal anticyclonic circulation in lower and middle atmosphere, its center locates in the oceans of the east Philippines and its western end of the ridge locates in the Indo-China Peninsula. In the lower atmosphere at 850 hPa, there are abnormal depression circulations in South China. However, there is an abnormal westerly trough in the southwest China in the middle-higher atmosphere at 500 hPa. The monsoon index of South China is defined by the characteristics of circulations affecting June precipitation in South China. The changes of June precipitation in South China can better be described by the monsoon index of South China, and the characteristics of the monsoon circulation system affecting the precipitation in South China can also be expressed, demonstrating a concise objective and quantitative indicator for studying monthly scale monsoon and precipitation in South China. Therefore, the monsoon index of South China has significance of operational use.

Variation of Surface Solar Radiation over the Central and East of Southern China

Zheng Youfei, Guan Fulai, Cai Ziying, Wu Rongjun, Liu Jianjun

2011, 22(3): 312-320.

[FullText HTML] (944) [PDF 1296KB](1952)

Abstract:
Surface solar radiation is one of most essential variables that influence the climate and environment. Various studies analyzing long-term records of surface radiation measurements suggest a widespread decrease in surface solar radiation between the 1950s and 1980s (global dimming), with a partial recovery more recently at many locations (brightening). To provide reasonable evidence for predicting the future trend of climate changes, the spatial and temporal variation of surface solar radiation and the causes are analyzed comprehensively by using observational solar radiation data together with conventional meteorological data of the central and east of southern China from 1961 to 2007.Solar radiation is obviously declining during 1961—1990 over the central and east of southern China, and a widespread brightening is observed during 1989—1995, but from 1995 to 2007 brightening doesn't persist and the solar radiation tendency tends to moderation. Increase of aerosol may be the main causes of solar radiation from dimming to brightening during 1961—1990, and the difference of cloud cover tendency maybe the main causes of solar radiation dimming.Model simulation shows that in recent 50 years water vapor is rising, which has decreased solar radiation by 0.55 W·m^-2 at the beginning of the 21st Century than that of the 1980s, but it is not main cause of solar radiation from dimming to bighting in recent 50 years. A widespread ascending aerosol optical depth (8.8%) is observed from 1980 to 2007, but the tendency tends to moderation. Due to the joint effect of atmosphere moisture and aerosol optical depth, a variation of aerosol direct radiative forcing is weakened, and the overall trend shows that aerosol direct radiative forcing variation trend to moderation (0.22 W·m^-2 in the country and 0.29 W·m^-2 in the city).Entering the 21st Century, solar radiation tends to moderation. This tendency indicates the cause for solar radiation change of China in the 1990s is different from Europe and America, and aerosol decline is not the major contributor. On the other hand, it also demonstrates if the air quality improves in the future, the solar radiation over the central and east of southern China may rise again.

Typhoon Processes Making Landfall in China from 2000 to 2007

Wang Yan, Zheng Dong, Zhang Yijun

2011, 22(3): 321-328.

[FullText HTML] (995) [PDF 1086KB](1751)

Abstract:
Based on the data of LIS, PR and TMI of TRMM satellite, the characteristics of lightning activities and precipitation in 41 typhoon processes making landfall in China from 2000 to 2007 are analyzed. The lightning activities in typhoons are found to be relatively weak compared with other convective weather systems. The lightning activity in outer rain band is the strongest and that in inner rain band is the weakest. Corresponding to these three regions, the average lightning frequencies are 16.05, 5.04 fl·min^-1 and 2.72 fl·min^-1 and the average lightning densities are 0.023, 0.029 fl·km^-2·min^-1 and 0.005 fl·km^-2·min^-1, respectively. The lightning activity in eyewall converged more than those in other two regions. Two peak values are found along the radial direction of typhoon. The main peak located in the outer rain band, 375 km away from the center of typhoon. The second peak is near to the common boundary of eyewall and inner rain band with the distance to the center of typhoon being 55 km. It is also found that the area of convective precipitation is far smaller than that of stratiform precipitation. However, the convective precipitation amount is basically equivalent to the stratiform precipitation. The average convective precipitation intensities in eyewall, inner rain band and outer rain band are 7.7, 26.3 mm·h^-1 and 42.6 mm·h^-1, respectively. The corresponding values of stratiform precipitation intensities are 5.2, 8.3 mm·h^-1 and 11.2 mm·h^-1, respectively. The average heights of precipitation echo of convective cloud and stratiform cloud are 8 km and 7 km respectively in eyewall and inner rainband and 11 km and 9 km respectively in outer rain band. The lower the polarization corrected temperature of 85.5 GHz (TPC85.5) is, the higher occurrence probability of lightning there are. The lowest T_PC85.5 is found in outer rain band. The differences of the reflectivity at 6 km level and T_PC85.5 are obvious between the regions with lightning activity and the regions without lightning activity. In eyewall, the average T_PC85.5 is smaller than 210 K. They are smaller than 220 K and 200 K in inner rain band and outer rain band, respectively. The reflectivity values at 6 km level in the regions with lightning activity are universally larger than 20 dBZ and those in the regions without lightning activity are universally smaller than 30 dBZ.

Climatic Division of the Types and Yields of Grassland in Inner Mongolia

Liu Hong, Guo Wenli, Quan Weijun

2011, 22(3): 329-335.

[FullText HTML] (1045) [PDF 1930KB](2658)

Abstract:
Based on the meteorological observation data of 107 weather stations in Inner Mongolia, mean monthly temperatures, mean monthly air humidity and annual rainfall distribution of kilometer-scale are calculated using gradient method of inverse distance square law. Taking the raster data into Ivanov moisture degree calculation formula, the moisture degree of kilometer-scale in Inner Mongolia Autonomous Region are obtained. Combined with the distribution regularity of actual vegetation types of Inner Mongolia, climate zoning index of grassland types in Inner Mongolia are identified. Five grassland types are defined in Inner Mongolia as meadow steppe, typical steppe, desert steppe, steppe desert, and desert. With the grassland type climate zoning index, partition boundaries of grass yield are determined. On the basis of output distribution in each partition, six grass yield levels of climate zoning index are obtained, which are grass yield greater than or equal to 2000, 1600—2000, 1100—1600, 900—1100, 800—900 kg·hm^-2, and less than 800 kg·hm^-2, respectively. And then humidity raster data could be classified by using these climate zoning indexes. After that, the zoning map of grassland type in Inner Mongolia Autonomous Region natural grassland could be drawn. In addition to that, the zoning map of geographical distribution of grass yield could also be got. Afterwards data of 65 field investigations samples as well as 49 ecological observation sites are used in a reliability test, for climate zoning results. The reliability analysis shows that division results and the distribution of actual grassland types in Inner Mongolia have good consistency, indicating that the grassland climate zoning can better reflect the spatial distribution regularity of natural grassland types. Hence, the grassland type division results can be used for climatic regionalization in Inner Mongolia grassland. Due to neglecting the soil texture, economic and other non climate factors, there is a certain error on the boundaries between the sand, grass crisscross midwest and different grassland type areas. For each district, its geographical position, climate characteristics and grassland utilization status are reviewed, and furthermore, related analysis, countermeasures and suggestions on rational distributions are given. In conclusion, the results can provide a scientific basis for adjusting agricultural structure and optimizing livestock layout in Inner Mongolia Autonomous Region.

Comparison of Temperature and Geopotential Height Records Between L-band and RS90/92 Radiosonde Systems Using First-guess Field

Ma Ying, Yao Wen, Huang Bingxun

2011, 22(3): 336-345.

[FullText HTML] (917) [PDF 1499KB](1401)

Abstract:
The first-guess field (FG) has been used to assess the quality of sounding observation data in operation work for many years. A long term data analysis shows that the mean differences of temperature and geopotential height records between observations and FG at those neighboring stations using the same type of radiosondes are very small, while the differences for those neighboring stations using different types of radiosondes are significant. It can be inferred that FG can reflect the regional differences of meteorological elements caused by the synoptic situation. So it is feasible to compare neighboring stations records by using FG as a relative reference, which can eliminate the regional synoptic situation differences. Undoubtedly, such comparison should be applied in small region (i.e., between neighboring stations) by using synchronous observation records, and only sufficient (long term) sampling data has statistical representation.Hongkong sounding station has used the RS90/RS92 radiosonde manufactured by Vaisala since 2005. And during 2007—2009, the L-band radiosondes are used at several stations nearby Hongkong, such as Wuzhou, Shantou, Dongyuan and Yangjiang. So 5 stations above are appropriate for indirect comparison of L-band and RS92 radiosondes by using FG. It shows that there exist significant systematic differences between L-band and RS92 radiosonde systems, for both the temperature records and geopotential height records at each standard pressure level, through the two-year statistical comparison.At 19:00, the mean differences of temperature and geopotential height records are very small in the troposphere. In the stratosphere, the temperature measured by L-band radiosonde is lower than that measured by RS92, and the difference increases with height, reaching over 1℃ at 20 hPa height. The increasing temperature difference with height brings on an increasing geopotential height difference, which is over 30 gpm at 20 hPa height.At 07:00, the temperature measured by L-band is higher than that measured by RS92, which leads to a higher geopotential value. The temperature difference reaches 0.4℃ in the middle and upper troposphere, and the geopotential height difference is over 20 gpm at 100 hPa height. In the stratosphere, although the temperature measured by L-band is lower than that measured by RS92, and the difference also increases with the increase of height, the cumulative difference of temperature at 07:00 is less than that at 19:00. So the geopotential height difference between L-band and RS92 records is only about 10 gpm at 20 hPa height at 07:00.The long term direct comparison between different types of radiosondes is difficult to be carried out because of the high cost. Indirect comparison by using FG is not only economical but can reflect the real difference of operational records, so it is well worth to be widely applied.

Deriving Atmospheric Zonal Mean Winds from Refractive Index Data

Xiao Weihua, Fu Yang, Gao Taichang, Du Xiaoyong, Xue Zhengang, Guo Yuening

2011, 22(3): 346-355.

[FullText HTML] (981) [PDF 1993KB](2201)

Abstract:
There are few effective ways to explore the middle atmospheric wind field directly at the altitude range of 20—60 km, and the direct sounding methods have some limitations, but the wind field could be derived from atmospheric refractive index and pressure data. From the bending angles, a large number of profiles of atmospheric refractivity, pressure and temperature are obtained with the newly launched Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC)/Formosa Satellite 3(FORMOSAT-3) System. Taking full advantage of these data has a positive impact on the research of the global middle atmospheric wind field. The approach for calculating middle atmosphere zonal mean winds at the altitude range of 20—60 km is constructed according to gradient wind equations from atmospheric refractive index data, considering the characteristics and calculation methods of geostrophic wind, gradient wind and balance wind respectively, and the relationships among atmospheric refractive index, density and wind field. Following the method constructed above, the middle atmosphere zonal mean winds are calculated by the gridded refractive index data in January, April, July and October of 2007 and the latitude-height distributions of zonal mean winds are discussed. The gridded data is derived through the inverse distance weighted interpolation method. The data is compared with monthly average wind data of European Centre for Medium Range Weather Forecasts Reanalysis-interim (ERA-interim) and the Modern Era Retrospective-analysis for Research and Applications (MERRA) data sets for validation. The comparisons reveal excellent agreement, and the characteristics of calculated winds are similar with that of the reanalyzed winds. In January and July, easterly winds prevail in summer hemisphere zonal mean zona1 winds and it increase as the height increases, while in winter westerly winds prevail hemisphere zone-mean zona1 winds. The zonal wind first increases and then decreases from the high-latitude to the low-latitude regions of winter hemisphere, with the maximum in the middle-latitude regions of winter hemisphere. The root mean square deviation and the largest deviation at different heights are larger and larger along the heights, while the correlation coefficients along latitude get smaller, but it is still greater than 0.98. The root mean square deviation is about 6 m·s^-1, and the largest deviation is less than 11 m·s^-1in January and July. Spring and autumn are the transition periods, when westerly winds prevail in global, but decrease versus increasing heights in the high-latitude regions of northern hemisphere and even reverse near the top in April; westerly winds prevail in the high-latitude regions, while for some altitudes in the low-latitude regions easterly winds are dominant. The differences are not very large in April and October, with the largest deviation no more than 8 m·s^-1, indicating that deriving wind fields from the COSMIC refractive index data through gradient wind equations is an effective way.

Evaluation on Energy Balance of Farmland in Shouxian County of Anhui Province

Tian Hong, Wu Qiong, Tong Yingxiang

2011, 22(3): 356-361.

[FullText HTML] (952) [PDF 544KB](1398)

Abstract:
Energy balance means the balance between the sum of latent heat, sensible heat flux observed by Eddy Covariance (EC) technique and the variance of net radiation flux, soil heat, canopy heat. According to the first law of thermodynamics and basic assumption of EC observation, the ratio of energy balance can be used as an effective evidence to evaluate data quality and system performance of an observation system theoretically. Energy balance ratio of the field has been investigated based on the data of flux observation system on near surface layer observed at the representative station of Huaihe River Basin, Shouxian National Climate Observatory from September 2007 to August 2008 in order to assess operation status of this new system. The results show that the annual average energy balance ratio is 0.89 during the period, and it is higher in the day than that in the night, higher in spring, summer, autumn than that in winter, higher over the bare surface than that over the cropland surface, while different weather conditions make little differences. The largest energy balance ratio is 0.92 over the bare surface, and smaller ratio is 0.9 over wheat field and paddy field, while it's only 0.50 over snow surface. It also shows that energy balance is influenced by the negligence of heat reserve during exuberant growing period to some extent and absorption tem, such as thaw, freeze and sublimation. During the observation period, the observed turbulent fluxes are always less than available energy, indicating that turbulent fluxes might be underestimated. The energy balance during daytime seems better than that at night because of stronger turbulence. It can be concluded that the applicability of EC method is best in flat, bare field, better in the day than that in the night, better on the underlying surface with low vegetation than that covered with snow. All in all, the phenomenon of energy imbalance is fairly common in flux observation and it often reaches 10% to 30%. The annual energy balance ratio (0.89) of Shouxian National Climate Observatory is close to the lower limit of ranges, so the EC method of flux observation over farmland ecosystem in Huaihe River Basin is reliable.

The Optimized Design of Stack for GRAPES's Adjoint Mode

Ren Disheng, Shen Xueshun, Xue Jishan, Zhang Lin, Zhao Wentao

2011, 22(3): 362-366.

[FullText HTML] (885) [PDF 1072KB](1138)

Abstract:
The four dimensional variational data assimilation system (4DVAR) of GRAPES (Global/Region Assimilation and Prediction System) can use different meteorological data from different areas of different times obtained to optimize the quality of forecast based on an initialization background. As the core of the 4DVAR, tangent mode and adjoint mode can adjust the initialization background through using the deviation of the estimate of 3DVAR and observation.When a segment of the adjoint mode is run, the initial state of corresponding nonlinear mode might be needed as input. In order to balance the disadvantage of whole storage and whole computation, a double chained stack is used to store an interim data's snap for implementing the adjoint mode. Adopting the whole storage can speed up the adjoint mode prominently, but this may lead to the relation of first in and first out (FIFO) among some data blocks, which conflicts with the configuration of the double chained stack. A nested and double chained stack is proposed based on original double chained stack, using a kid chained stack to separate the data blocks that have FIFO relations. Data block pops first must be pushes in kid chained stack, and then can be popped at any time as needed. The nested and double chained stack can meet these requirements of different data blocks, FIFO or FILO, and satisfy the requirement of adjoint mode better. The result of experiment shows these approaches can double the operational speed with 30% extra memory.

Application of the Background Management Model to Data Sharing Service Platform

Gao Feng, Wang Guofu, Sun Chao, Yu Wen, Xu Yan

2011, 22(3): 367-374.

[FullText HTML] (884) [PDF 1094KB](2659)

Abstract:
Along with the development of meteorological data sharing service platform and the establishment of the security system, appropriate administrative organization and operating mechanism, a background management system is needed to realize automated and operational management. The background management model is planned as enriching the service data products and enhancing the quality of data service. A lot of developing work has been carried out to optimize the flow of data publishing and updating, operation flow, data automatic collecting, the whole network monitoring and data service to meet these demands and changes from the beginning of 2006. At the end of 2009, the construction of the whole data sharing platform is accomplished, which consists of foreground interactive sub-system and background management sub-system. The former is responsible for the provision of data discovery and data access, and the latter offers a lot of configure management functions.The background management system for meteorological data sharing service platform is developed completely based on the metadata technology, and it uses J2EE architecture to ensure the scalability and flexibility. The logic diagram of the background management system includes data level, management level, service level and support level. The system is made up of metadata management, operational management, platform management and system monitoring modules. The system realizes metadata management and new data product publishing, data (set) management, information statistics and analysis, content management, security management, system configuration management, system monitoring, and other functions. The deployment and implementation of background management system make sure that the publishing of one new data products become more timeliness and convenient, and ensure a long-term and stable operational running of the meteorological data sharing service platform.

Subsystem for Interactively Drawing Synoptic Chart in MICAPS

Yu Lianqing, Hu Zhengguang

2011, 22(3): 375-384.

[FullText HTML] (1002) [PDF 1048KB](1512)

Abstract:
A subsystem is developed for interactively drawing synoptic chart to solve issues in previous versions of MICAPS and meet new user requirements. First of all, the composite design pattern is used to define the class hierarchy that describes graphical objects. This class hierarchy fits well with the relation among different graphical objects and therefore reduces the spatial complexity of the program, making manipulations to graphical objects much easier to implement. Thanks to the polymorphism feature provided by modern object-oriented programming languages, clients manipulating the graphical objects can treat all objects in this composite structure uniformly. The consequential benefit of this design advantage in practice is that the client code does not need to be modified when new types of graphical objects are introduced. This is especially useful for developers to define customized graphical object in their own applications. Above all, the proposed class hierarchy not only promotes code reusability, but also makes it easy to add new types of graphical objects. The code that draws rubber band graphical objects is constructed using the state design pattern, in which the behavior of drawing a particular type of graphical object is implemented in the corresponding class. The advantage of this approach is that introducing new types of graphical objects only require deriving new subclass and does not affect existing code. In addition, the gesture event class is proposed to represent the start, continue and end gestures in the rubber band drawing. In this way, the gestures can be customized at runtime by users. On the contrary, if the conventional code structure using large conditional statements is employed for rubber band drawing as in the previous implementation, the code complexity will increase dramatically when new types of graphical objects are introduced and the code defining the gestures has to be modified when user changes these gestures. The disadvantage makes it difficult to extend, debug and maintain the code. An algorithm to modify linestrip-type graphical objects, in particular isolines, is proposed. By taking advantage of the smoothness constraint, the proposed algorithm is able to solve the ambiguity in isolines modification and make the modified result meet the user expectation. The command design pattern is employed to implement undo/redo and runtime logging. The former feature facilitates users manipulation and the latter feature can restore the program session to the last successful state after the program quits abnormally. These two features enhance usability and reliability of the program. The implementation of automatically saving edited document which ensures the integrity of the documents is discussed. With all these features implemented, the proposed system not only facilitates users manipulation but provides good performance and reliability as well.

Vol.22, NO.3, 2011