Vol.16, NO.6, 2005

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THE RETRIEVALOF RAINFALL INTENSITY AND VERTICAL STRUCTURE OF HYDROMETERS USING GPROF ALGORITHM
Li Xiaoqing, Wu Rongzhang
2005, 16(6): 705-716.
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Abstract:
The framework of GPROF algorithm, used as operational rainfall retrieval algorithm for TMI by NASA is introduced. GPROF algorithm is used to retrieve the rainfall intensity and vertical structure of hydrometers for some rainfall cases, including rain cases of Changde area in the summer of 2002 and a case of Utor typhoon attacking Hongkong on 5 July 2001, in terms of TMI 1B11 data. Comparison of GPROF algorithm retrievals with ground-based radar shows that GPROF algorithm retrievals can retrieve rain intensity well and indicate vertical structure of hydrometers mainly. As far as retrieved rain area, it is better for convective precipitation type than stratified precipitation type. Namely, GPROF algorithm can describe no-raining information better than infrared method especially for convective rainfall but it would leave some stratified precipitation areas out. Similarly, Comparison of GPROF algorithm retrievals with PR 2A25 products on ocean show that the results of GPROF algorithm can catch major rain information of typhoon and show that the results of GPROF algorithm can catch major rain information of typhoon and indicate vertical structure of hydrometers mainly. At same time, the retrieved latent heat can give some thermodynamic characters of typhoon, which ulteriorly help to understand climatic change and general circulation on earth. If an improvement of GPROF algorithm is made according to the precipitation characters of China, such as building a cloud-radiation database using the realistic profiles from measurement of models, considering it is a global algorithm, the precision of retrieval over China may be improved。
TEMPORAL AND SPATIAL DISTRIBUTION OF THE DIFFERENT CLOUDS OVER NORTHWESTERN CHINA WITH THE RELATION TO PRECIPITATION
Chen Yonghang, Huang Jianping, Wang Tianhe, Jin Hongchun, Ge Jinming
2005, 16(6): 717-727.
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Abstract:
The temporal and spatial characteristics of the different clouds and the relation to precipitation over Northwest China are analyzed using the ISCCP (International Satellite Cloud Climatology Project) monthly mean D2 data from July 1983 to September 2001. Northwestern China is divided into three climatic regions for the purpose of this study. The results show that the plateau climatic region is the one with highest cumuliform cloud amount with low values of liquid water path. The higher cloud amount value areas for most types, especially for high cloud, are over Tianshan Mountains, Kunlun Mountains, Qilian Mountains, and southern Shaanxi and/or southern Gansu, while the lower values of cloud amounts are located over Tarim Basin, the western desert of Inner Mongolia and the northwestern part of Loess Plateau. Also, cloud amount levels are consistent with levels of precipitation. In general, cloud amounts are higher in spring and summer while lower in autumn and winter. The amounts of stratiform clouds associated with higher liquid water path are consistent with precipitation. The amounts of cumuliform and stratocumuliform clouds, however, do not have definite relation to precipitation。
ANALYSIS OF LIGHTNING ACTIVITY OVER THE YANGTZE RIVER DELTA USING TRMM/LIS OBSERVATIONS
Dai Jianhua, Qin Hong, Zheng Jie
2005, 16(6): 728-736.
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Abstract:
In terms of TRMM/Lightning Imaging Sensor (LIS) data, the lightning activity over the Yangtze River Delta from 1998 to 2004 is undertaken. After applying the observation efficiency correction for the LIS data and using the viewing times statistics of LIS over the target area, the temporal (annual and diurnal) and spatial distributions of LIS lightning are depicted. The number of lightning flashes observed by LIS varies year by year, and the maximum is about three times the minimum. About 60% of the lightning days and 70% of the lightning flashes of a year occurs during July and August, with lightning peaking in the afternoon. The lightning activity peaks in the early evening in other months. In Shanghai, severe thunderstorms often occurs when the number of LIS lightning flashes in a day is more than eight. Fewer lighting flashes and days are found over water areas. Some lightning activity centers are found downstream of metropolis such as the east part of Shanghai, and mountain areas such as Longmen Mountains. When moving off shore, some thunderstorms tend to intensify and produce more flashes. Results show that the temporal change in solar radiation brings about the temporal distribution of LIS lightning activity. The physical features of surface and topography may be major causes for the difference in the spatial distribution of lightning in mesoscale. Comparisons with ground-based observations, such as Doppler weather radar and the SAFIR total lighting localization system are also made。
ESTIMATION AMOUNT OF SUMMER REGIONAL HEAVY RAINFALL USING THE AVERAGES OF RADAR VPRs TOGETHER WITH RAIN GAUGE ADJUSTMENT
Shi Rui, Cheng Minghu, Cui Zhehu, Liu Zhaohui
2005, 16(6): 737-745.
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Abstract:
A method of estimating precipitation using the averages of radar VPRs together with gauge adjustment is presented. Focusing on the several events of heavy rainfall occurred in the mid-lower reaches of the Yangtze river in the summer of 2002 and 2003, the radar reflectivity factor data of volume-scan mode acquired by the CMA new generation S-Band radar deployed in Yichang and Hefei, and the corresponding 10-min average of gauge precipitation records in the range of the 100 km radius centered at above radar locations are used to calculate possible short-term average of VPRs at the ground-level, and are further to retrieve the precipitation amount and its relative errors. These objective data are also used to analyze characteristics of real-time VPRs in 10 min heavy rainfall. The precipitation amount, which is estimated by using the averagely adjustments of gauge records together with the fitted VPRs based on the least square method (LSM), is reasonable at surface level over a great part of a certain region. Compared with gauge records, the proposed method shows its capability to improve the precision of precipitation estimation in a regional scale, however, for the case of intensive convective precipitation, only the LSM is applicable. Characteristics of VPRs in a short time intensive heavy rainfall are helpful to estimate the amount of rainfall over a region without the gauge. Additionally, with combination of other data sources, characteristics of VPRS and be used to analyze the evolution of the precipitation process。
CASE ANALYSIS OF THE FORMATION AND EVOLUTION OF 12 JULY 2004 SEVERE SQUALL LINE
Yao Jianqun, Dai Jianhua, Yao Zuqing
2005, 16(6): 746-752.
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Abstract:
Using the data from conventional weather observations, the Shanghai WSR-88D Doppler weather radar, and observations from automated meteorological stations, a long-lived severe squall line on July 12, 2004 is analyzed. The case analysis shows that the intensification of the jet between 850 hPa and 500 hPa that causes the low level frontogenesis and high potential severe weather. The squall line triggers in the case are the surface front, the low level convergence, and upper level divergence. The strong vertical wind shear and the feedback between the strong updrafts and downdrafts in the storm sustains the squall line in a severe stage for 6 hours. The interaction between the squall line and the outflow boundaries of the storms along the same Mesoscale Convective System (MCS) intensifies the other storm and changes its path。
ANALYSIS OF LOW FREQUENCY OCSILLATIONS OF THREE RAINSTORMS DURING THE PERIOD OF MEIYU IN 2004 OF ANHUI
Chen Xiaohong, Zhang Jiao
2005, 16(6): 753-762.
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Abstract:
In terms of wavelet, vortex and moisture flux divergence analyses, study is undertaken of 2004 rainstorms from June to August in Anhui. Results show that the elements exhibit significant 2~6 d, 7~15 d and 18~30 d oscillations. The variations of 2~6 d and 7~15 d oscillations of the these elements are almost consistent with the anomaly of precipitation from mid-June to later-June. The vortex of the 7~15 d oscillation moves towards Anhui along the mid-latitude from west to east, and the moisture flux divergence of the 7~15 d oscillation moves towards Anhui from low-latitudes. The cyclone and anticyclone wave trains of the 7~15 d oscillation moves towards northwest over the equatorial west Pacific Ocean and the high frequency change of the streamline field at low levels provide favorable conditions for Anhui rainstorms in June 2004。
STUDY ON DECADE CHANGE OF CLIMATE SHIFT FROMWARM-DRY PERIOD TO WARM-WET PERIOD OVER TIBETAN PLATEAU
Niu Tao, Liu Hongli, Song Yan, Chen Long xun
2005, 16(6): 763-771.
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Abstract:
In terms of the yearly average data obtained from 123 routine meteorological observatories located over Tibetan Plateau, the decade characteristics of climate change over the Plateau in the recent 40 years are studied. It is found that in the mid-late 1980s, an evident climatic sudden change happens to yearly average temperature rainfall and relative humidity, featured by the increasing of them. The climate of the Plateau shifts to warm-wet period from warm-dry period at the sudden turning point. The climatic sudden change of temperature and rainfall are earlier than that of relative humidity over the target region. Over the Plateau, the increases in temperature and humidity occur mainly in winter and these increases, also occurring in spring, show slow range; increase of temperature and somewhat lowered humidity happen in summer; autumn is a season for remarkable increase of temperature but humidity shows no tendency of its change。
Influences of Nino3 SST Rising in the Second Half Year on East Asia Spring General Circulation and Shandong Spring Precipitation
Hu Guifang, Zou Jin, Zhang Xuan
2005, 16(6): 772-778.
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Abstract:
By analyzing next-spring abnormal features of 500 hPa height and 850 hPa, 200 hPa meridional wind due to Nino3 SST rising, it is found that Nino3 SST rising abnormally in the second half year leads to 500 hPa height field rising in the tropic and Northwest Pacific subtropical region, namely the Northwest Pacific subtropical high is stronger and shifts westwards and northwards compared with the mean, and the trough over East Asia is weaker with its location shifts eastwards; the height field falls from the area around Balkhash to Baikal Lake, i. e., trough often maintains; zonal circulation prevails over Asia and the Western Pacific; Southerly winds intensifies over east part of China and neighboring sea area. while northerly winds weaken over north China and the Northeast of China. The abnormal features of the height and meridional wind fields are uniform with that of much more April precipitation in Shandong. Result suggests that spring precipitation in Shandong and eastern China are often richer after Nino3 SST unusually increasing in the last second half year。
IMPROVED EXPERIMENT ON THE EXPLANATION AND ANALYSIS METHOD OF DYNAMICAL EXTENDED RANGE FORECAST PRODUCTS
Jiang Shuangwu, Tian Hong, Chen Lijuan
2005, 16(6): 779-786.
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Abstract:
Based on a relationship between monthly precipitation anomaly and monthly circulation, the forecast equation coefficients are calculated as variables. The sample data are selected from which has similar potential height field to that in the forecast month. The monthly rainfall forecasts is improved by calculating the equation coefficients. The latest seven-year hindcast tests proves that the method of calculating of coefficients has certain value in operational application. Under the consideration of a limited accuracy of T63/NCC monthly dynamical extended-range forecast products (T63/NCC MDERFP). Also, results are obtained in the application of monthly rainfall forecast of Anhui Province by T63/NCC MDERFP。
THE PHYSICAL MECHANISMS ANALYSIS AND FORECAST RESEARCH ABOUT THE HEAVY FOG IN HUZHOU
Yu Shuqiu
2005, 16(6): 787-793.
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Abstract:
Using the daily temperature data of 234 stations during recent 50 years in China, the trend of daily maximum/minimum, the changes of days with characteristical temperature, the growing season length and effective accumulative temperature are studied. The result shows the daily maximum displays an obvious increase trend in summer for most of northern part of the country, while there is a decrease trend in south part of Xinjiang and middle Huanghe river basin and Huaihe river basins. The daily minimum of summer in most part of northern China has increasing trend, while in south part of Xinjiang and Changjiang river basin it is decreased. During winter time, both daily maximum and minimum have increasing trend, especially in northern China. The number of hot day with 30℃ or above is not change obviously, but the number of warm days with temperature 20~30 ℃ increased during the last 50 years. Number of days with temperature below 5 ℃ are decreased. The cold days with daily temperature below 0 ℃ are decreased in the region north to Changjiang river. Also the very cold days with daily temperature below-10 ℃ are decreased along the region 40º~45ºN deceased very obviously. The growing season length in most parts of the country, except the southwest region increased during recent 50 years. Accordingly the effective accumulative temperature increased too。
The Physical Mechanisms Analyses and Forecast Research About the Heavy Fog in Huzhou
Li Faran, Zhou Zhixu, Chen Weifeng, Zhu Hong, Chen Shichun
2005, 16(6): 794-803.
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Abstract:
A model is developed to prognosticate the heavy fog. For creating a objective forecasting-heavy-fog model, the circulation background information must be transformed into numeral format. Ignored the fog classification and corresponding synoptic patterns, it uses various physical variations to describe the circulation background on the formation mechanism of the heavy fog which is valuable in not only easily quantifying, but also realizing the forecast's objectivity and automatity. The algorithm of the variations conversion and their combinations presented. The concept and its formula of the directional transporting are very effective to dynamical quantifying of relevant background field. In the fog-forecasting model, based on BP neural networks technique, the forecast factors and forecast index and better describe the whole background, in which developed the heavy fog, it consists of numerous information and has effective application. The design of the neural networks and the parameterization scheme would be a good reference to the construction of the other forecast systems。
REMOTE SENSINGMONITORING TECHNOLOGY OF THICK FOG AT NIGHT BASED ON NEURAL NETWORKS AND FRACTAL GRAIN
Zhang Shunqian, Yang Xiurong
2005, 16(6): 804-809.
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Abstract:
In terms of the ground-object spectrum information and the image-grain information as symbols to distinguish the ground-objects, fractal theory and BP neural networks are used to monitor thick fog at night, which increases the monitoring precision of thick fog obviously. Compared with the traditional Maximum Likelihood Classifying (MLC), the identified precision of clear sky ground, fog areas, cloud areas is increased, especially that of the cloud areas is increased by 10%. The image-grain extraction technology of grey-power box-counting dimension basing on grey degree connected region made extracting the borderline of cloud and fog more reasonable. Also, the merger of kings is discussed。
IMPROVEMENTOF K-DISTRIBUTION PRECISION FOR CALCULATING THE TRANSMISSION OF SATELLITE REMOTE SENSING CHANNEL
Yin Hong
2005, 16(6): 811-819.
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Abstract:
The absorption band of oxygen at 0.76μm may be used for satellite remote sensing pressure of ocean, earth and cloud surface. The relative variation of pressure is about 10-3, so the precision of vertical transmission calculated by k-distribution method must be less than 10-3. According to the increase of computer velocity, the way to increase the precision of vertical transmission calculated by k-distribution method includes: (1) decreasing the simplify calculating processes, (2) when the variation of absorption coefficient is complicated in the channel, increasing the number of sectional points. The extreme number of sectional points is 136, the extreme stand error of vertical transmission calculated by k-distribution method is less than 3×10-5
Study on Eco-climate Applicability of Spring Wheat for Condign Planting Division in Gansu Province
Ma Xing xiang, Deng Zhenyong, Li Dongliang, Chen Lei, Wei Yuguo, Zhu Guoqing
2005, 16(6): 820-827.
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Abstract:
Based on Meteorological data, such as 10-day average temperature, sunlight times, precipitation, accumulated temperature (≥0℃), altitude above the sea level and etc, a integrated contribution index and a function of eco-climate applicability for spring wheat are established. Results show that the applicability of spring wheat to altitude is between 0.15-0.85 with minimum values in Dingxi and Gulang, maximum values in Jinta and Dunhuang; the applicability to accumulated temperature (≥0℃) has the same tendency with altitude; applicability to 10-day average temperature is with 0.35-0.58, which indicates the temperature is suitable to the spring wheat growing. Afterwards, by the way of integral regression, the contributive coefficients in different climate regions and growth phases are analyzed for spring wheat. It suggests that the average contribution coefficients of sunlight, temperature and water has maximum values at moderate plain, oasis irrigated area; medium values at warm desert oasis irrigated area; and minimum values at cold hill half-irrigated area. The influence and relying of spring wheat of ceo-climate applicability is studied too. Finally, the integrated division index of eco-climate is confirmed, the planting division of climate applicability is divided into 5 grades. Also, a effective approach of exploiting and developing the eco-climate resources is proposed。
MEASUREMENTS OF CO2 FLUXES OVER TWO DIFFERENT UNDERLYING SURFACES IN AN AGRICULTURAL ECOSYSTEMOVER LOWER BASINS OF THE YANGTZE
Bian Lingen, Gao Zhiqiu, Lu Longhua, Wang Ying, Chen Zhigang
2005, 16(6): 828-834.
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Abstract:
In order to better understand the regional climate change, it is necessary to quantify the CO2 flux over agricultural ecosystem. CO2 fluxes are collected directly by using eddy covariance over a rice paddy in the summer of 2001 and over an inhomogeneous crop surface in the summer of 2002 respectively. On average, daytime absorption and nighttime release of CO2 flux by the rice paddy are 55.16 g· m-2·d-1and 14.19 g·m-2·d-1, and by the inhomogeneous crop surface are 22.67 g·m-2·d-1and 12.40 g·m-2·d-1. Rice paddy and the inhomogeneous crop surface are sinks of atmospheric CO2. China is a great agricultural country, increasing the area of rice paddy will help CO2 deposition, and will slow down increase of atmospheric CO2 and greenhouse effect. In addition, the relationship between daytime absorption of CO2 flux and Photosynthetically-active radiation is investigated for the rice paddy, and resulting a negative correlation. Hopefully the results obtained in present work will provide an important basis for numerical modeling of CO2 flux between atmosphere and land。
THE ALGORITHMOF SOUNDING BALLOON FLOATING ERROR
Li Wei, Wang Zhiwen, Xie Zhuang, Liu Fengqin, Xu Lei, Tu Manhong
2005, 16(6): 835-840.
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Abstract:
With the development of numerical model, more attention is paid to the error caused by sounding balloon floating. In order to improve the quality of sounding data and reduce the sounding balloon drifting error, China Meteorological Administration puts forward an expansion code scheme. Based on the analysis of principal of current operational sounding system, the article introduces the algorithm of scheme, illustrates the utilization method and operational application prospect in terms of a case study。
TO IMPROVE THE OBJECTIVE POSITION PRECISION OF TC WITH GIS
Lu Xiaoqin, Lei Xiao tu
2005, 16(6): 841-848.
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Abstract:
Supported by GIS technology, an objective TC (Tropical Cyclone) center positioning system integrating much data and arithmetic is performed. All kinds of vector and raster layer data, such as Quikscat wind distribution on the ocean, weather state, forecast state, different satellite images and different band images of the same satellite, are super positioned together and analyzed in this system. It is helpful to show TC characters in many ways. Many TC center positioning methods, such as analyzing cloud form, finding the warmest point on cloud and eroding or dilating cloud image to find TC center, are synthesized to make TC center positioning more objective, precision and roboticized, center of 0203, 0209, 0212, 0417 and 0419 TC are positioned by this system. The result shows that the precision of this system is close to that of operation TC center positioning. It proves that this system could be applied in operation
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