应用气象学报

2003, 14(3)

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Abstract:

Characteristic Parameters of Response Curves of Leaf Photosynthesis of Winter Wheat in Huanghuaihai Region

Liu Jiandong, Zhou Xiuji, Yu Qiang

2003, 14(3): 257-265.

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Abstract:
A series of winter wheat varieties in different decades is selected for measuring the leaf photosynthesis under suitable soil moisture and temperature conditions. The light response curves are fitted for each variety, and the initial quantum efficiency, maximum photosynthesis rate and respiration rate are determined. The variation regularity of leaf photosynthesis parameters with time is revealed based on these characteristic parameters. Numerical analysis of the effects of the initial quantum efficiency and maximum photosynthesis rate on the daily photosynthesis shows that it is not suitable to quote parameters from foreign literatures as the basic parameters in the Chinese crop models. A set of basic parameters of the crop model is presented, which provides premise for simulating the regional application with crop models in the future.

Impact of Initial Field and Long Wave Radiation on Climate Modeling

Shen Yuanfang, F .Baer, Wang Chao

2003, 14(3): 266-276.

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Abstract:
Ten realizations of CCM2 (T42L18) with only slight variations in the initial states have been carried out. The results reveal the response of CCM2 to the initial field, and it is evident that there is substantial variability in the runs, with deviations in many places on the globe and various spectral scales being in excess of 10%. Similar results are found for clouds and temperature. Comparing ten CCM2 algorithm runs with three runs using CCM2, MOR and NMC algorithms, it is evident that the climate simulations for the runs with different algorithms show much larger variability from one another than that for the initial field without changes of LWR algorithms. Comparing the modeling results using the CCM2, MOR and NMC algorithms in the CCM2 model, it can be seen immediately that CCM2 and MOR runs are closer to one another than to the NMC run. Nevertheless, the differences on all charts exceed 10% in many places on the globe, which are far above the impact of the initial field on climate modeling.

Analysis and Diagnosis of a Local Heavy Rain in Miyun County, Beijing

Wang Yunchun, Qian Tingting, Zheng Yongguang, Tao Zuyu

2003, 14(3): 277-286.

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Abstract:
Miyun, the northeast county of Beijing, had a local and short-time heavy rain on 1 August, 2002. The amount of precipitation reached 280.2 mm and the rain caused a mud-rock flow and flood fatality. Satellite cloud pictures show that this rain was triggered by a mseo-βconvective system which settled in the northern mountain area. The dense isoline region of TBB and the up-rushing cloud top indicate the rainfall area. The large-scale circulation shows that there was sinking motion, accompanying an inversion layer which restrained the convection and favored the accumulation of instable energy. During the rain process, the conversion from sinking to ascending made the convection possible. The large-scale analysis of water vapor indicates that there was abundant water vapor from the northwest of the subtropical high to Beijing. The result of surface mesoscale analysis shows that the mesoscale low and the convergence line are trigger factors for a mseo-βconvective system, and that the high-humidity and high-temperature airflow is in favorable of local heavy rains.

Effects of Synoptic Scale and Sub-synoptic Scale Systems on Formation of a Heavy Rainfall Process

Yao Wenqing, Xu Xiangde

2003, 14(3): 287-298.

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Abstract:
By means of the mesoscale numerical model MM5V2, the heavy rainfall process during the later June of 1998 in the middle and lower reaches of the Yangtze River is analyzed. By utilizing the scale-separating method and comparing the results of numerical experiments, the characteristics of physical elements of synoptic scale and sub-synoptic scale systems are investigated. The physical mechanisms of heavy rainfall formation are presented as follows: synoptic scale wind and water vapor fields provided long-distance water vapor transportation for the heavy rainfall while the sub-synoptic scale wind field results in strong meridional convergence which provided the steady dynamic condition for the lifting and condensation of water vapor; under the favorable disposition of upper and low level jets, the rainfall region was located to south of the upper level jet and north of the low level jet; the unstable thermal stratification, cooler at lower level and warmer at upper level, of the sub-synoptic scale temperature field facilitated the development of the thermal unstable condition and further strengthened the heavy rainfall; the sub-synoptic scale high-value center of the specific humidity field over the rainfall area was favorable to the emission of latent heat and further enhanced the feedback mechanism of the heavy rainfall. In numerical experiments, message separation was conducted on the systems with different scales in the model initial field to indicate their dynamic effects in the heavy rainfall process. The results show that both intensity and coverage of heavy rainfall will decrease to some extent while there is only a synoptic scale or sub-synoptic scale system during rainfall process. Analyses and results of numerical experiments suggest that heavy rainfall can form and sustain under the comprehensive effects of both synoptic scale and sub-synoptic scale systems.

Change of Maximum Frozen Soil Depth in China and Its Primary Explanation

Liu Xiaoning, Li Qingxiang

2003, 14(3): 299-308.

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Abstract:
With the annual maximum frozen soil depth data of China, analysis is made of the special distribution and decadal change during the recent 50 years. The results show that the annual maximum frozen soil depth in China began to decrease since the 1980s, and decreased more distinctly during the 1990s. The decreasing of the maximum frozen soil depth is in accordance with the climate change (rising of minimum temperature and decreasing of the annual average daily temperature range). It indicates that the maximum frozen soil depth is sensitive to the climate change in China.

Interrelationship of Climate Change, Runoff and Human Activities in Tarim River Basin

Yang Qing, He Qing

2003, 14(3): 309-321.

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Abstract:
The temporal and spatial characteristics of climate change, dust storms and runoff in all the source areas and the mainstream of the Tarim River are analyzed based on observations in 13 meteorological stations (from 1961 to 2000) and 8 hydrologic stations (from 1957 to 1998) over the Tarim River basin. The water consumption influencing index, which quantifies the impact intensity of human activities, is set up, and the impacts of climate change and human activities on the runoff, even the ecological environment are studied. The results show: (1) Although the runoff over the source areas didn't change obviously since 1950's, but the amount of water entered the mainstream of the river from these source areas obviously decreased, and human activities is the main cause. (2) The water consumption influencing index analysis shows an increasing trend, which reflects the impact of human activities to some degrees, and the impact of human activities in the middle reaches of the river is greater than that in the upper reaches. The impact of human activities was most obvious during the period from the 1970's to the imd-1980's, and slowed down in recent 10 years. (3) In 1990s, temperature and precipitation increased over the river basin. The increasing amplitude of temperature increases from the source areas to the lower reaches of the river. In Aksu (in the source area), the increasing amplitude is the smallest for temperature and the biggest for precipitation. (4) Since the 1990's, the number of dust storm days, the number of floating-dust days and the number of strong-wind days in the river basin obviously decreased. These changes could be attributed to the extending of oasis. (5) Precipitation at Tiekanlik (at the lower reaches) decreases, instead of increasing, and the number of dust storm days increases. It should be paid attention by the related departments.

Impact of East Asian Summer Monsoon and Subtropical Anticyclone over Western Pacific on Droughts/Floods in Fujian

Cai Xuezhan, Gao Jianyun, Wu Bin

2003, 14(3): 322-330.

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Abstract:
Based on 850 hPa NCEP/NACR wind and OLR data, different features of East Asian summer monsoon and the subtropical anticyclone over western Pacific between dry and wet years in Fujian Province are discussed. The main results are as follows: In the East Asian summer monsoon system, the intensity of tropical monsoon circulation strengthens (weakens) while the intensity of subtropical monsoon circulation weakens (strengthens), with a northward (southward)-slanted average location of the western Pacific high in wet (dry) years. During the seasonal transition from spring to summer and summer to autumn, the seasonal northward and southward jumps of the high ridge in wet years are quicker, inversely the jumps in dry years are slower. The "-+-" ("+-+") anomaly pattern dominates over East Asia at 500 hPa in wet (dry) years, i. e., there is not (is) blocking situation while the subtropical frontal zone moves northward (southward) in wet (dry) years. Results also show different features of the impacts of northward-and southward-slanted subtropical high locations on rainfall and their distributions in various months in summer in Fujian Province.

Inversion of Diffusion Coefficients and Effect of Related Difference Schemes

Liu Feng, Hu Fei

2003, 14(3): 331-338.

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Abstract:
Air pollution prediction is a direct problem, and deriving diffusion coefficients from the concentration of pollutants is an inverse problem. A direct problem is different from an inverse problem in essence, and their definitions and methods of resolution are quite different. A sort of solution of the inversion of the vertical diffusion coefficients in the atmospheric boundary layer is defined based on the theory of optimum control. The adjoint model method is introduced to calculate the gradient of the objective function, and then the inverse problem is solved. It turns out that the result of the inverse problem is sensitive to the choice of difference algorithms, and is directly affected by the settlement of the sources used in the measurement. The causes of errors are analyzed both in theory and in numerical experiments. The relationships between the inverse result and the difference algorithms and sources are summarized, and then satisfactory results are shown in the resolutions. The above studies are of help to the practical experiments to measure diffusion coefficients.

Climatological Calculation and Characteristic Analysis of Global Radiation over Wuxi Region

Zhang Yunlin, Qin Boqiang, Chen Weimin, Hu Weiping

2003, 14(3): 339-347.

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Abstract:
The variation of global solar radiation reaching the surface over the Wuxi region and its calculation are studied for further understanding of the solar transfer on water-air interface and the underwater irradiance. The main methods and formulas for climatological calculation of global radiation are simply discussed. Based on the observation data of global radiation and relative sunshine at Shanhai, Nanjing, Hangzhou stations, the empirical coefficients for these stations are calculated by using the least square method. The coefficient for the Wuxi region is calculated through interpolation from the coefficients of the three stations. The climatological calculation formula, which is suitable for Wuxi region, is brought forward. The global radiation reaching the surface is gained by using the formula and relative sunshine data at Wuxi station in recent 40 years. The formula precision is checked up by use of the observation data from the Taihu Lake ecosystem research station, which is proved to credible. At last, by analyzing the calculation results, the characteristics and causes of global radiation variation are discussed. The results show that the global radiation has decreased in the past 40 years and the decrease mainly attributed to the increase of suspended matter in the atmosphere. The annual variation of global radiation is basically similar to extraterrestrial irradiation except some differences in summer. These differences are caused by Meiyu with greater precipitation, cloud cover and less sunshine.

Statistical Characteristics of Unusual Tropical Cyclone Tracks in Offshore Guangdong

Mao Shaorong, Zhang Dong, Liang Jian, Li Xiaojuan, Weng Xiangyu

2003, 14(3): 348-355.

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Abstract:
Statistical analyses are made on unusual tropical cyclone tracks with sudden changes of directions in offshore Guandong based on the data from Typhoon Almanac for the period of 1949 to 2000. Studies are also carried out on characteristics of intensity, moving speed, offshore distance, and turning points of typhoons with unusual tracks, as well as their relationships. Meanwhile, the impact of topography in the Guangdong coastal area on tropical cyclones is also studied. The results show that the locations where these tropical cyclones turned suddenly (or close to the coast) were concentrated in mountainous coastal areas, and tropical cyclones tend to slow down when they approach the coast. It is also shown that prior to turning, the more intense the tropical cyclones are, the closer the turning points are to the coast, and the smaller incident angle they need. In addition, near the coast, the slower the tropical cyclones move, the more markedly they turn.

Relationships Among Wheat Surface Temperature, Air Temperature and Surface Ground Temperature at Noon in the Wheat Fields

Duan Yonghong, Li Bengang, Tao Shu

2003, 14(3): 356-362.

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Abstract:
The quantitative relationships among wheat surface temperature (TL), air temperature (Tɑ) and siol-surface temperature (TS) at noon in the wet and dry wheat fields were investigated based on field data. The data collected was divided into a training set and a validation set and three types of weather were categorized as clean, cloud and both. The results show that for the wet wheat field in clear days, the best results could be achieved using Tɑ to estimate TL; based on the final model, the average estimated error is 1.03oC and the RMS of estimated TL is 1.26 oC. For the dry wheat field in the clear or cloud days, TL could be well estimated with TS. The average estimated errors of the final model are 1.64 and 1.54 oC respectively and the RMS of estimated TL are 2.05 and 1.89 oC respectively. The RMS errors achieved are generally lower than those derived from NOAA digital images (2—3 oC). The results of this research show that it is feasible to forecast wheat surface temperature with air temperature and soil-surface temperature, too. It provides a new cheap effective means to get wheat surface temperature; at the same time, it is also possible to combine satellite image data with measured data from ground weather stations to predict the water requirement of winter over a larger region.

Preliminary Research on Inhomogeneous Distribution of Tibetan Plateau Sensible Heat Fluxes in Spring

Bai Jingyu, Xu Xiangde, Zhou Yushu, Zhang Xuejin

2003, 14(3): 363-368.

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Abstract:
Study is undertaken of Tibetan sensible heat flux features in spring prior to the summer flood/drought in the milled and lower reaches of the Yangtze River (hereafter referred as MLRY). Analysis of the difference of atmospheric temperatures and 0 cm soil temperatures indicates that the Tibetan thermodynamic structure displays noticeable discrepancy preceding flood/drought in MLRY: there exists an air-ground temperature difference pattern of "high in South and low in North" in spring before flood and "high in North and low in South" before the drought. Sensible heat fluxes on Tibetan Plateau show that the spring flux difference (of flood and drought in MLRY) in the target regions takes on "high in South and low in North" manner. Outcome of simulations suggests that Tibetan plateau sensible heat fluxes in spring on a south-north inhomogeneous basis lead to the summer precipitation abnormity in MLRY, that is, the Tibetan sensible heat flux anomaly is one of the "strong signals" which contribute to the flood/drought in MLRY.

Scalability of Massively Data Parallel Computing Problems

Jin Zhiyan, Wang Dinxing

2003, 14(3): 369-374.

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Abstract:
The performance of distributed parallel systems is influenced by many factors, for examples, the total number of nodes in the system, node speed, I/O speed, latency and communication speed of the inter-network. Adding more nodes and/or using more powerful nodes can improve the performance, but I/O and communication could suffer from it. To determine the relationship between performance and those factors, the scalability of the massively parallel computers by using a data parallel model is analyzed. The relationship between the number of node, the speed of the nodes and the communication speed and latency of the links between nodes, the I/O speed of the system is obtained. The results shows that it is necessary to increase the I/O speed and the speed of the links (decrease the latency) by a certain ratio while increasing the number or the speed of the processors, so as to keep the scalability of the system. Only increasing the number or the speed of the processors will decrease the scalability of the system.

Brief Analyses of Virus Damage to Meteorological Operational Network and Antivirus Methods

Gong Xianchuang

2003, 14(3): 375-378.

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Abstract:
The computer virus damage to the meteorological operational network and the computer virus's variation tendency are analyzed. The design and application of the anti-virus system of the Wuhan Meteorological Center, Hubei Province, are introduced. It is shown that the anti-virus system using the group and rank management model is effective against computer virus for the meteorological operational network and can insure the normal operation of meteorological service.

Vol.14, NO.3, 2003