Vol.21, NO.4, 2010

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The Evolution Characteristics of Mid latitude and Low latitude Synoptic Systems During the "05.6" Heavy Rain Event in South China
He Lifu, Zhou Qingliang, Chen Tao
2010, 21(4): 385-394.
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The evolution characteristics and interaction between mid latitude and low latitude synoptic systems during "05.6" heavy rainfall process in South China is studied in detail. The monsoon activity in South China Sea, basic characteristics of sub tropical high in west Pacific, the influence of the cold air in middle latitude, and the coupling mechanism between upper level and low level jet are analyzed based on NCEP/NCAR reanalysis data with the resolution of 1°×1° and a series of observation data. FY 2C satellite data, including the brightness blackbody temperature on cloud top (TBB) data with the resolution of 0.05°×0.05° and outgoing long wave radiation (OLR) observation with the resolution of 0.5°×0.5°, surface observation for 3 hour interval, and auto weather station observation for 1 hour interval are used for model initialization and verification. The results are as follows: Under the stable background of high pressure in the north and low in the south, the "05.6" heavy rainfall is produced by the interaction between monsoon system from low latitude and mid latitude cold air driven by east coast trough and plateau short wave. During the "05.6" heavy rainfall, the sub tropical monsoon in South China Sea blocks the cross equatorial flow path and leads to the abnormal equator west wind in area of 100°-120°E. It moves northward massively for 2 times, indicating the beginning and end of this rainfall process. The strength of sub tropical high maintains very strong and the position of high ridge changes in an abnormal pattern of west advancing east retreating west stretching and north advancing during the prophase stable north jump finally. The south invading of 700 hPa cold air in westerly belt in the beginning of the process has important impacts on this event, which may be the most important feature in this process. During the "05.6", there is a ULJ (upper level jet) on left front of South China and a LLJ (low level jet) on the right. Strong aloft divergence of ULJ and the ageostrophic force in the left of LLJ forms the secondary circulation across LLJ, so the positive feedback of coupling mechanism between ULJ and LLJ may be one of the prime causes for the "05.6" heavy rain event.
Introduction of Auto nowcasting System for Convective Storm and Its Performance in Beijing Olympics Meteorological Service
Chen Mingxuan, Gao Feng, Kong Rong, Wang Yingchun, Wang Jianjie, Tan Xiaoguang, Xiao Xian, Zhang Wenlong, Wang Ling, Ding Qinglan
2010, 21(4): 395-404.
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The auto nowcasting system for convective storm (BJ-ANC) is an expert system that has been improved and further developed to many key algorithms and modules other than they are just introduced from US. The skill of the system is focused on nowcasting convective storm in Beijing and its vicinity. Key improvements have been made to the algorithms including quality control of CINRAD radar data, diagnosis and analysis of local observations from radars, satellites, AWSs, rawinsondes and meso NWP results from a WRF based rapid update cycling model, identification, analysis and tracking of storm cells, grid tracking and extrapolation of radar echo, rapid updating assimilation of radar data, quantitative precipitation estimate (QPE) and quantitative precipitation forecasting (QPF), etc. The forecast factors produced by the above algorithms are closely related with initiation, evolution and decay of convective storm in general. These algorithms are integrated by a fuzzy logic algorithm under non dimensional modes with different weighting coefficients in the system and nowcasting products are generated. Based on many theoretical and experimental results, the relationship and conceptual model of boundary layer convergence line and initiation and evolution of storm have been imported into the system for nowcasting localized initiation and rapid evolution of storm. BJ-ANC system runs in real-time mode during 2008 summer time. The system performance for nowcasting initiation and rapid evolution of storm is improved after convergence line is adopted by interactive human entry function. Verification of storm cell extrapolation and 1 hour QPF in Beijing area and its vicinity during 2008 summer is performed using the B08FDP real time verification system. The results indicate extrapolation of storm cell in 1 hour is significant and the forecast deviation is small. The 1 hour QPF from the system is comparable with rainfall observation from AWSs, denoting the QPF products can be used for supporting nowcasting operation of convective rainstorm. The storm reflectivity nowcasts from the system have been demonstrated much more significant than those from persistence method. Storm case analyses indicate these products from the system are conductive for storm nowcasting operation and boundary layer convergence line is extremely helpful. In addition, retrieval of thermo dynamical fields can clearly indicate three dimensional structures of wind, convergence and temperature at low layer and further help forecasters make decisions on storm initiation and evolution nowcasts.
Applied Research on Adaptive Observation for Identifying Sensitive Regions Based upon TIGGE Data
Zhao Xiaolin, Zhu Guofu, Li Zechun
2010, 21(4): 405-415.
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Accurate prediction of high impact weather is very important. Adaptive observation has an immediate significance to improve the quality of high impact weather forecast. THORPEX (THe Observing system Research and Predictability EXperiment) is a ten year international atmospheric research program with the primary objective to improve the accuracy of 1 day to 2 week high impact weather forecasts for the benefit of society and economy. THORPEX is developed under four sub programs, and two of them are related to adaptive observation, which are observing systems, data assimilation and observing strategies, so adaptive observation is the foundation and prerequisite to achieve the ultimate goal of THORPEX. Adaptive observation is a type of observation interactive between weather forecast (or weather service) and observation. The key to adaptive observation lies in identifying sensitive regions. Sensitive regions are defined as localized regions from where the analysis errors grow significantly and thereby the forecast skills are degraded. As a new method for identification of sensitive regions which is based on ensemble predictions, ETKF (Ensemble Transform Kalman Filter) has many advantages, such as the program simplicity, independency and so on. On the basis of an ensemble prediction solely, ETKF solves Kalman equation in the space of ensemble, and it can estimate the reductions of prediction error covariance caused by adding observation immediately. The research of ETKF has a proactive effect on both adaptive observation and ensemble predictions. On the basis of TIGGE (THORPEX Interactive Grand Global Ensemble) data, through identification and comparison of the sensitive regions of two different types of heavy precipitation events, specific aspects in the actual application of ETKF method to the adaptive observation are analyzed in detail. The results indicate that the appropriate horizontal resolution and coverage of ensemble data can be used for a reasonable result and shorter computational time, and the reasonable result shows that the geographical distribution of the signal variance maxima calculated from different resolutions and coverages are basically coincident and a relatively small coverage can even be used for the heavy precipitation event under regional weather circulation comparatively to that under macroscale weather circulation; identified sensitive regions are more credible by using ensemble predictions available which are initialized more recently; identified sensitive regions calculated from different meteorological centers' ensemble data are more consistent and reliable for the heavy precipitation event under clear macroscale weather circulation than under regional weather circulation; a calculation of signal variance using nine adjacent grids at one time makes the wide distribution of signal variance maxima, and makes it not conducive to locate sensitive regions more precisely. To the result of sensitive regions, the effects could negligible if the analysis errors of routine observation are changed moderately. Sensitive regions under different circulation are dependent on the selected metric to some extent. In conclusion, the sensitive regions identified by ETKF are understandable and reasonable.
Gauge Hourly Observations by Shepard Interpolation Method and Optimum Interpolation Method
Li Chunhui, Liang Jianyin
2010, 21(4): 416-422.
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The precipitation is one of the most important meteorological factors that impact on human activities. The high resolution precipitation products are useful on weather and climate monitoring, calibration of numerical model and hydrologic prediction. Due to the asymmetry and discontinuity of precipitation in spatial and temporal distribution, the excessive and absent asymmetric rainfall resulted in the meteorological disasters such as flood and drought. In order to avoid and reduce these disasters, it is important to know the amount and distribution of precipitation exactly. Using the rainfall recorder observation is the most direct, effective and common method to obtain precipitation information. But the rainfall recorder data only represent several isolated stations information, not the continuous grid data. In order to obtain the standard grid data, it is necessary to process the original rainfall data with math methods. A lot of interpolation methods have been proposed, such as Cressman, Barnes, Gandin, Shepard, Hulme. Bussieres and Hogg as well as Chen have compared and verified the interpolation methods in application of the daily and monthly rainfall analysis. It has been concluded that Gandin optimal interpolation possesses much more exactly, effectively and stably. But for smaller time scales, what math interpolation can be used to obtain a better results and how to set the correlative parameters needs further researches. Using the Parameter elevation Regressions on Slope Model (PRISM), an objective analysis of gauge hourly regional observation precipitation in Guangdong and Guangxi from 20 May to 30 August 2007 with the spatial resolution of 0.125°×0.125° by Shepard interpolation method are implemented, the results are compared with optimum interpolation method too. The comparison analysis shows that both the results can represent the inter seasonal and diurnal variation of gauge regional mean precipitation well between direct interpolation and PRISM interpolation. Although the spatial distribution of precipitation gained by the direct interpolation is smoother than that by PRISM interpolation, but the estimated precision of direct interpolation is lower than that of PRISM interpolation. The cross validation indicates that the accuracy of precipitation products by the optimum interpolation is better than that by Shepard interpolation. The PRISM optimum interpolation is an optimal method that can improve correlation and reduce root mean square error as well as system error.
The Application of Wavelet Transform to Satellite Cloud Image Compression
Fang Xiang, Wang Xin
2010, 21(4): 423-432.
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Different characteristics between meteorological satellite cloud images and common images are analyzed, and a compression method of meteorological satellite cloud images is proposed based on wavelet transform (WT). First, the bio-rthogonal Odegard 9/7 filter is selected, which shows better compression ability for cloud images. Using this filter, a cloud image is five step decomposed and reorganized. It's found that the wavelet coefficients of cloud image have more similarity and obvious attenuation in different steps, the wavelet coefficients are encoded using the improved 0 tree quantization algorithm. Finally, a further compression is processed for the output data streams using the adaptive arithmetic coder. The method proposed performs better in cloud image compression than other existing compression methods, e.g., the classic embedded 0 tree wavelet (EZW) introduced by Shapiro. And within the anamorphic error range, the highest ratio of cloud image compression is 40:1 for infrared image, 60:1 for water vapor image and 35:1 for visible image.
Influences of Precipitation on Atmospheric Extinction Coefficient and Visibility
Liu Xichuan, Gao Taichang, Liu Lei, Zhang Wei, Yang Shuchen, Li Tao
2010, 21(4): 433-441.
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The variation of visibility is mainly influenced by the scattering and absorption of atmospheric particles at visible wavelengths. The principle of visibility sensors are based on the relationship between visibility and atmospheric extinction coefficient, which is integrated by scattering coefficient of atmospheric particles within a volume. The influence of aerosol, dust particles and smoke are usually taken into account in the traditional visibility analysis. However, as one important factor affecting visibility, precipitation particles are usually neglected, causing obvious inaccuracy when precipitation occurs. Physical characteristics (size, velocity, density, shape, size distribution) of precipitation particles are analyzed and then their influences on atmospheric extinction coefficient and visibility are discussed based on scattering characteristic of raindrops and snowflakes. The relationships of rainfall and snowfall with visibility are obtained by numerical simulation based on fitting size distribution parameters, which are validated by observation data of precipitation and visibility obtained by Parsivel precipitation particle spectrometer in Nanjing. The comparisons show that the numerical simulations are in good agreement with the observation data. The conclusions are as follows: The visibility decreases exponentially as the rainfall/snowfall intensity increases; however, the influence of rainfall and snowfall on visibility is different, because the atmospheric extinction is mainly affected by the types, density, velocity, sizes and distribution of the precipitation particles; with the same precipitation intensity, smaller particles leads to lower visibility; the theoretical relationship of precipitation intensity to visibility takes on a good accordance with the observation data while considering the size distribution and ice crystal types; and the influences of snowfall on visibility are more complex because the atmospheric extinction snowfall are related to the snow/crystal types. Finally the influences of precipitation on visibility are confirmed by the combination of observation data and theoretical analysis. The influences of precipitation particles on atmospheric extinction coefficient and visibility are discussed on the assumption that the aerosols are totally cleared by rain or snow in this model, which results in the overestimation of visibility. To obtain more accurate relationship of visibility and precipitation, the influence of aerosols and its variation with time should be considered, which deserves further investigation.
Temporal Distribution and Waveform Characteristics of Positive Cloud-to-ground Lightning in Beijing Area
Zhang Yang, Zhang Yijun, Meng Qing, Lü Weitao
2010, 21(4): 442-449.
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The temporal distribution and waveform characteristics for positive cloud to ground lightning (PCG) vary in different regions. The research on characteristics of PCG in Beijing Area is still not enough up to now. Based on the lightning location data from March to November in 2004 and 2005, the temporal distribution of PCG in Beijing Area is analyzed. The waveform characteristics are also investigated using the data of electric field change. The results show that from May to July there are more PCG happening than other seasons in Beijing Area. The PCG occupies 55.3% of all lightning events from March to May and from October to November, while the percentage of PCG is only 10.88% for the whole year. On the other hand, the distribution of PCG in Beijing also changes with time in a day, with a high frequency of PCG and a large percentage up to 16.2% during 15:00—21:00. It's also found that the temporal distribution is inverse correlation between PCG and negative cloud to ground lightning (NCG) in a day. There is a decreasing tendency of PCG lightning with an increase of cloud to ground (CG) lightning. For most of PCG there is only one return stroke and the percentage of PCG with multiple return strokes is only 3.89%. The PCG with multiple return strokes mainly occurs in May and November and during 15:40—17:20 in a day. The waveform parameters and the characteristics of continuing current are given by statistics. The rising time of return stroke is between 5—28 μs, with a mean value of 11.55 μs. The time of slow front is between 2.8—23.6 μs with 9.41 μs on average. The ratio between the amplitude of slow front and the peak of return peak is 53%. The time of recovering to zero is 43.97 μs and the depth of the dip is 20.75%. The average value of return stroke peak after being normalized to 100 km is 13.66 V·m-1. Most of PCG contain continuing current process. The percentage of PCG with continuing current is 69.2%, 48.7% of which lead to long continuing current. The average lasting time of continuing current is 113 ms.
Simulation of Lightning Leaders and Connection Process with Structures
Ren Xiaoyu, Zhang Yijun, Lü Weitao, Tao Shanchang, Deqing Cuomu
2010, 21(4): 450-457.
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Lightning is a kind of long distance discharge phenomenon, and it often causes a variety of disasters which become more serious by the extensive use of electronic devices particularly. With deep understanding on physical processes of lightning occurrence and development, lightning leader model is established based on observational facts to study development of lightning leader and its interaction with structures and provide reference for lightning protection. In order to study the interaction of lightning leaders and structures, the connection process of leaders is simulated. A 2 dimension model of lightning leader is developed by simulating ambient potential distribution using an over relaxation method. In the model, the direction of next leader step depends on the position of a maximum potential gradient. Attractive radius in the model is defined by horizontal distance between initial axis of downward leader and connection point (such as lightning rod, the corner of building). The distance of final jump is defined by the distance between the tip of downward leader before final jump and connection point. Simulation results show that the length of stepped leader ranges from 13.8 m to 51.5 m. The induced charge of downward leader is about 0.03×10-4-1.2×10-4 C/m. The length of stepped leader and the induced charge of downward leader increase with the propagation of downward leader. These simulated results are consistent with the observation. Before the final jump, the turning of downward leader is not obvious. In the final jump, downward leader turns some direction towards the upward leader initiated from lightning rod. Simulation results are accordant with the previous simulation results. The interaction and connection process between downward leader and a structure with a width of 40 meters are simulated using this model. The corner of structure has some attractive radius and can compete with lightning rod on structure. In the design of lightning protection, attractive effect of corner to lightning leader can't be neglected. The design of lightning protection based on attractive radius of lightning rod under perfect conditions (such as isolated tip on the ground) is problematic and risky.
The Cause of pH Measurement Negative Bias in Acid Rain Monitoring
Tang Jie, Yu Xiangming, Cheng Hongbing, Wang Shufeng, Xu Xiaobin
2010, 21(4): 458-463.
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Precipitation pH and conductivity are measured routinely in a nation wide network with more than 300 stations known as Acid Rain Monitoring Network (ARMN), under the infrastructure of China Meteorological Administration (CMA) since early 1990s. Recent reports indicate that a small part of precipitation pH data in the historic ARMN CMA dataset may suffered negative bias, upmost to-0.3 pH unit, when meticulous statistical method being applied in the data quality evaluation. To seek a better understanding on the causes of this negative bias, a field investigation is designed and conducted to track the performance of pH electrode at site by using the method of routine measurement of target samples. Two target samples prepared by the central lab in Beijing, with pH value of 4.8 and 6.5, are measured at two dozen of selected CMA ARMN stations once every ten days. At one of the selected stations, obvious negative bias in pH measurement appears after a new pH electrode being put into use for only 3 months. The magnitude of the negative bias produced by this short lived electrode is relatively steady in following 6 months, which ranges from 0.2 to 0.4 pH unit and is similar with that found in the historic pH dataset of ARMN CMA. As the regulated usage period for a pH electrode in ARMN CMA is 12 months, the lack of on site pH electrode examining/testing method at ARMN CMA stations may result in using a short lived electrode unwittingly in the routine precipitation pH measurement. Hence, the aging of pH electrode is considered as the most likely cause for the negative bias found in the historic pH dataset of ARMN CMA. Further test for the found aged pH electrode, by using a group of prepared solutions with different pH values and conductivities, shows that the negative bias of aged pH electrode is not only affected by ion strength of the solution, but also by the acidity of the solution. The aged pH electrode tends to give larger negative bias in the solution of lower ion strength. Also, the negative bias given by the aged pH electrode is correlated to the pH value of the solution. For the solution with conductivity in range of 30—70 μS·cm-1, the slope of the negative bias to the pH value of the solution is about 0.08, which tends to be smaller for the solutions of higher ion strength. Based on the results of the field investigation and the laboratory test, target sample measurement is suggested as an on site quality control method for pH measurement at stations.
Characteristics and Impact Factors of Acid Rain in Beijing
Pu Weiwei, , Zhang Xiaoling, , Xu Jing, Zhao Xiujuan, , Xu Xiaofeng, Dong Fan, Yu Bo
2010, 21(4): 464-472.
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The annual and seasonal characteristics of acid rain in Beijing during 2003-2008 and their relationships with the meteorological conditions and pollutant concentrations are investigated using data observed at Beijing Weather Observatory, Changping and Shangdianzi acid rain observation stations. The average pH of precipitation is lower than 5.6 from 2003 to 2008, and the variation in the annual average precipitation acidity displays a decreasing trend over the past 6 years. After 2007, the acid rain pollution becomes more serious in Beijing area, when the average pH of precipitation is lower than 4.5 at all the three observation stations. The annual average pH values of precipitation at Beijing Weather Observatory and Changping are higher than that at Shangdianzi Station in the past 6 years except for 2008. It shows that the acidification degree in background area is heavier than that in urban area. Seasonal and monthly variations in precipitation acidity, conductivity and the frequency of acid rain are observed in Beijing area. The average pH and K values of acid rain in summer and autumn are lower than those in spring and winter. The frequency of acid rain with pH < 4.5 and 4.5 < pH < 5.0 is highest in autumn and summer, respectively.The monthly variation of acid deposition show that the heaviest acid rain pollution occurs in summertime, espe-cially in August.The decrease tendency in the pH and K value and the increase tendency in the frequency of acid rain with pH < 4.5 are found with the increase of precipitation intensity, respectively.The higher pH and K value at Beijing Weather Observatory and Changping Station indicate that the process of below-cloud scavenging is more important in urban area, and alkaline coarse particles in the atmosphere plays an important role in neutralization.The wind direction at 1500 ml evel has significant influence on the precipi-tation acidity and conductivity value over Beijing area.The lowest pH is observed with south wind, and higher K value and heavier acid deposition are recorded with the southwest and south wind.The transport of pollutants by the southerly flow enhances the acidity of precipitation.The acid rain is also influenced by the temperature inversion.The frequency of acid rain increases when continuous inversion occurs (temper-ature inversion occurs at rainy day and the day before that).Temperature inversion occurs most frequently during autumn that leads to the increase of acid rain pollution in this season.Furthermore, pollutants in the atmosphere have important effect on the acidity of precipitation.There is a significant negative correla-tion between the concentration of atmospheric pollutants, suchas SO2, NO2 and PM2.5, and the pH of rain, suggesting that the variation of pollutant concentration in lower atmosphere layer has significant in-fluence on the acid rain.SO2 and NO2 are the important precursors of the acidic compositions and the major contributors of acidity in rainwater.The neutralization effect of fine particles (PM2.5) is very weak.On the contrary, the acid compositions of PM2.5 are partly contributed to the acidity of precipitation when they are scavenged into the rainwater.
Temporal and Spatial Distribution Characteristics of Carbon Monoxide Column Amount over China Based on Satellite Data
Bai Wenguang, Zhang Peng, Zhang Xingying, Wang Weihe, Qi Jin, Liu Hui, Zhang Wenjian, Bianba Ciren
2010, 21(4): 473-483.
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Carbon monoxide is an important tropospheric species inasmuch as it influences the atmospheric chemistry through its reaction with the OH radical. It's also one of the main pollutants produced by incomplete combustion processes. Coupled with few weeks lifetime, it can be used as a tracer of atmospheric transport. Surface CO measurements which have generally been limited to boundary layer measurements often affected by local pollution cannot provide a global view of CO temporal and spatial distribution. Better understand these characteristics relies on a combination of ground based, aircraft, and space based measurements. CO long term changes and trends over a large area can only be obtained through space based remote sensing observations. Such measurements have been carried out by the SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument on ENVISAT satellite and the Measurement of Pollution in the Troposphere instrument on TERRA (MOPITT). These measurements have been used effectively on monitoring CO plumes from forest fires, intercontinental transport of pollutions, frontal lifting and convective transport of pollution to the upper troposphere, and for inverse modeling to quantify surface source of CO. MOPITT measurements are useful in providing a global picture of the distribution of CO, but studies on their near surface application is limited. Since the sensors of CO on MOPITT are near the 4.7 μm absorption spectra, they are sensitive to CO mostly in the middle and upper troposphere but generally less sensitive in the lower troposphere comparing with the CO measurements in the solar channel at 2.3 μm by SCIMACHY. An introduction is given on CO remote sensing retrieval methods used by SCIAMACHY/ENVISAT and MOPITT/TERRA. Distribution properties and trend of CO from MOPITT of 2003 to 2005 are compared to SCIMACHY retrieval results. The two products show good agreement on the land; also they give roughly the same spatial and temporal distribution characteristics of CO. Comparisons between MOPITT product and ground measurement data of CO over Longfengshan, Lin'an and Waliguan during 2007—2008 show roughly the same temporal change in posture. Distribution characteristics and trend of CO from March 2000 to February 2004 over China is analyzed using MOPITT retrieval CO column amount product. On the average, CO in the east of China is higher than west. There is significant seasonal variation for CO with a peak in spring time. CO concentration in summer time is lowest in the east, but it reaches the minimum in autumn in the west of China. Trends analysis suggests that CO average column amount have increased during these nine years. The increasing trend for CO in the west region of China is at magnitude of a few thousandths, but in the east the increasing trend is about 1%.
Downscaling Interpretation of NCC_CGCM Products for the Summer Precipitation over the Mid lower Reaches of the Yangtze
Ai Wanxiu, Sun Linhai, Song Wenling
2010, 21(4): 484-490.
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With February initial fields, NCC_CGCM model is run and the products (height field at 500 hPa, zonal wind and meridional wind fields at 200 hPa and 850 hPa) are compared with NCEP observation during 1983—2002 to study their relations. Although the differences between the observations and NCC_CGCM model predictions are obvious, there are still some areas where the correlation index is high to 0.6, such as the western equatorial Pacific at u200, the northern equatorial Pacific at v200, the central equatorial Pacific at u850, the central North Pacific at v850, some area around New Zealand at H500, and so on. The total amount of grids where the positive correlations reach or exceed 95% statistical confidence is counted. For u200 and u850 there are more correlated grids, and correlated grids amount for H500 is the smallest. An experiment is done using the summer precipitation index in the mid lower reaches of the Yangtze which is one of the 15 areas divided by climate characteristic in China. Some grids data are chosen where the correlations (between the precipitation index and NCEP, between the precipitation index and model products) are both positive, reaching or exceeding 95% confidence at the same time. With the chosen data from NCC_CGCM, the regional precipitation index is predicted by EOF downscaling method from 2003 to 2007, getting an accuracy of 80%. The precipitation forecast result got by downscaling with chosen data from the model proves better than those with the model and EOF downscaling with only H500 product of CGCM for the mid lower reaches of the Yangtze. The same downscaling is also run on the rest 14 areas from 2003 to 2007 but the accuracies are different. In Jiangnan and Inner Mongolia, the accuracies reach 80% too.
Causes of Winter Precipitation Anomalies in Northern Xinjiang
Yang Lianmei, Shi Yuguang, Tang Hao
2010, 21(4): 491-499.
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There is steady and thick snow cover in Tianshan Mountains and its north area (northern Xinjiang) in the cold winter. Snowfall has important impacts on crop surviving the winter, livestock feeding and drinking, traffic and transfer, ice snow resources replenishment. With economic development, the impacts of winter precipitation anomalies become more and more important. To further understand the mechanism of winter precipitation anomalies, the inter seasonal characteristics of circulations, water vapor (WV) transfer, income and expenses of WV are analyzed. Using daily rainfall data of 38 stations in northern Xinjiang and NCEP/NCAR daily reanalysis dataset from 1960 to 2004, the characteristics of circulation, WV transfer, income and expenses of WV for November, December and January precipitation anomalies in northern Xinjiang are investigated, as well as contributions from circulations and WV anomalies respectively on the whole WV transfer anomalies. The results show that Scandinavian (SCA) pattern plays a leading role on monthly precipitation anomalies in winter of Xinjiang. WV transfer quantity (WVTQ) is the largest in November, and smallest in January. West and east boundaries are charged with the dominating importing and exporting borderline of WV respectively for every level, and net WV earning quantity presents an obvious increasing trend every month. During the months with abundant precipitation, more WVTQ along westerly over middle Asia comes from Arctic Ocean, Siberia and Arab Sea respectively rather than from regions of Mediterranean Sea and Caspian Sea. WVTQ along westerly of east to Caspian Sea reveals weakening in less precipitation months. For winter precipitation prediction, the east west oscillations of the upper level jet stream over north Atlantic and the corresponding the baroclinic eddies resulting in SCA pattern activity is very important, and WV transfer anomalies coming from Arctic Ocean, Siberia and Arab Sea areas should also be highly concerned.
Influences of Climate Warming on Plant Phenology in Qinghai Plateau
Li Hongmei, Ma Yushou, Wang Yanlong
2010, 21(4): 500-505.
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Long period data observed at selected meteorological stations are analyzed to investigate the response of plant phonology to climate warming in Qinghai Plateau. The Plteau is divided into eastern agriculture region, around Qinghai Lake region, source of three rivers and Qaidam Basin, with their representative areas of Huangyuan, Menyuan, Qumalai and Delingha, and the analysis period is 1983—2007, 1987—2007, 1997—2007 and 1987—2007 respectively. Monthly and annual mean temperature, precipitation, plant development period and other related data are analyzed statistically, showing that annual temperature increases in all of the 4 regions with the ratio of 0.61℃/10 a, 0.59℃/10 a, 1.52℃/10 a, 0.62℃/10 a respectively. Annual precipitation of around Qinghai Lake region shows a decreasing trend, and the value is-11.58 mm/10 a. Annual precipitation of eastern agriculture region, source of three rivers and Qaidam Basin increases by 0.86 mm /10 a, 107.37 mm /10 a and 12.95 mm /10 a respectively. The date of turning green in Qaidam Basin region has delayed by 8.2 d, but in eastern agriculture region, around Qinghai Lake region and source of three rivers it is 8.6 d, 10.5 d and 9.8 d earlier than before. In these 4 regions the flowing stage are respectively 3.2 d, 7.8 d, 1.7 d and 10.9 d earlier. The yellow stage is respectively 6.5 d, 16.2 d, 6.6 d and 6.2 d later, so the plant growth stage is extended in the eastern agriculture region, around Qinghai Lake region and the source of three rivers, but the plant growth stage is shortened a little in Qaidam Basin. The changing tendency of turning green data and yellow stage is found well correlated with annual mean temperature. There are many factors affecting the flowing of plant, so the correlation between plant flowing and mean annual temperature is less significant. The annual precipitation and stage precipitation have some influences on key periods of plant growing, but the influences are less important compared with the temperature.
The Design of an Open Platform for Automatic Weather Stations on Real time Data Quality Control
Feng Xiuyan, He Zhijun, Wang Heping, He Lide
2010, 21(4): 506-512.
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The open platform for real time data quality control provides a unified interface and operating environment with the methods of quality control. The platform management system has the comprehensive ability to apply a variety of embedded quality control methods. Reports of the quality control from different system of quality control methods can also be analyzed comprehensively. With the platform, on the basis of interface and operating environment, technicians can independently carry out some operational trials and technological research about some quality control methods. Relevant quality control methods can also be integrated in the platform, so the methods with poor performance can be improved and replaced. Using the platform, pressure, temperature, relative humidity and precipitation data of 78 automatic weather stations are processed real time with 5 different quality control methods during the 3 month trial run in Zhejiang Province. Experiments show that using the comprehensive application of the platform can increase accuracy rate of the data error detection by 60%, and provide technical foundation for the research of promoting the quality control methods.
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