应用气象学报

The Analysis of the Meteorological Cause of Formation of Forest Fire in Da Hinggan Ling Region

1990, 1(1): 107-112.

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Abstract:
In this paper, the meteorological factors of the catastrophic forest fire in Da Hinggan Ling region of northeastern China in May, 1987 have been analysed. It is found that the drought and less rainfall in the previous period, and much higher temperature in the first ten-day of May are the climatic conditions of the forest fire. Da Hinggan Ling region is located in northeastern China, which is part of the frigid-temperate zone and the annual mean temperature is -3 to -6oC. Therefore, the organic matters are decomposed rather slowly and make more and more combustibles accumulated in the forest, It provides the material condition of the fire. A very strong dry cold front with the average wind speed 8—12 m/s, and the extreme speed 17.0 m/s, just passed away when a large number of fire points were in existence, which spreaded the fire over wide areas rapidly. This is the key factor of the fire. In addition, the topographic factor which related to the temperature and the snow cover also affected the extension of the fire

1990, 1(1)

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Interannual Low-frequency Oscillation of Meridional Winds over the Equatorial Indian-Pacific Oceans

1990, 1(1): 2-11.

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Based on analysis of the meridional winds over oceanic areas and sea surface temperature for 1950—1979 extracted from the data sets of COADS, the long-term variability of the meridional winds over the equatorial Indian–Pacific Oceans and its relationship to the onset and development of El Nino events have been studied. The major results are as follow: ① There is a great similarity between Intertropical Convergence Zone (ITCZ) over the Pacific and SST in the seasonal trend, with ITCZ and high SST found in Southern Hemisphere in winter and in Northern Hemisphere in summer. During El Nino years, unusual meridional winds were often observed, with significant convergence of meridinal wind occurring over near-equatorial regions. ② For the near-equatorial meridional winds, there are types of interannual low-frequency oscillations—QBO, SO, FYO. QBO plays an important role in the unusual behavior of meriodional wind for El Nino years, while SO is very important for both El-Nino and cold water years. These two oscillations may fit well to the observed variation in the meridional wind. FYO may enhance the variation of mericional wind. ③ Interannual low–frequency oscillations of meridional winds originate in the Indian Ocean—Maritime Continent and coastal area of the east Pacific. Unusual activities of winter monsoon in both hemispheres and trade wind off the coastal area of the east pacific are believed to the their major cause. ④ Monsoon-trade interaction shows up in the significant amplification of the disturbances of meridional wind while they propagate eastward form monsoon area to trade wind area

A Numerical Experiment on the Lee Cyclogenesis of Qinghai–Xizang Plateau in a Six–level Limited Area Model

1990, 1(1): 12-23.

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The present model, including more physical processes, is a six-level primitive equation model for Asia area with efficient and accurate numerical techniques for the computations of pressure gradient force and the initial fields in the vicinity of mountains in σ–coordinate. The numerical experiments on the cyclogenesis of Qinghai-Xizang Plateau are performed successfully by using the present model with the initial condition based on objective analysis data on 11th July, 1981. More interesting simulation results are displayed, and they show that the dynamic influence of Qinghai-Xizang Plateau is an important role to the lee cyclogenesis with low-level south–westerly jet stream in southwestern China. The results also that unless the consideration of mountain effects (or reducing the orographic height by the factor of 0.5 in the model) the simulations are failure

A Quasi–operational Experiment from a Nonsteady Atmosphere–Earth Surface Coupled Anomaly Model

1990, 1(1): 24-33.

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A quasi–operational experiment for 30–day forecast has been made for morthly anomalies of 100 hPa, 500 hPa, SLP and SLT during January through December of 1988 from a nonsteady atmosphere—earth surface coupled anomaly model. The results show that the forecast of tendency of 100 hPa monthly anomaly is best and that of SLP is not too good, the model forecasts for both 500 hPa and surface temperature monthly anomalies are better than persistence forecasts. It means that this model can be forecast anomaly field in large scale. The results also show that it is better in the low and mid–latitude regions than in the mid–high latitudes. But the forecast effects are not quite the same for the different levels and months and the forecasts for low pressure systems are very satisfactory. The model has a defect in the spatial resolution, which is too smooth. So, it needs more experiments and improvements.

1990, 1(1)

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1990, 1(1)

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Reconstructions of the Southern Oscillation and Pacific Sea Surface Temperature for the Last 500 Years

1990, 1(1): 34-44.

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In this paper, a canonical correlation technique has been used to reconstruct the seasonal index of the Southern Oscillation and seasonal Pacific SST from the dryness/wetness in China for the last 500 years. About 40 percent of the SO variance during the calibration period of 1913—1973, and about 20 percent of the variance for an independent period of 1852—1912 have been caliberated and verified, respectively. In the reconstrucion of the Pacific SST, about 60 percent SST variance has been caliberated in the equatorial eastern Pacific areas and the estimate value has been efficiently verified over 100 years. It shows that the past ENSO events can be reconstructed in certain extent by using dryness/wetness data in China. It is found that ENSO events not only has apparent periodicity, but also has about 250 years stage change. Both SO and SST have the well-known 2—7 year periodicities, besides, SO has 10.6 year period and SST has 25—28.5 and 100 year periods which related with the solar activities. It is also found that the low SOI events are estimated to be less frequency during the 18th, 19th and the early 20th centuries than the later 15th, 16th, 17th and later 20th centuries, and that the frequent (rare) occurrence of the low SOI events mentioned above corresponds with the climatic cold (warm) period, and that the dryness (wetness) period in China is related to the cold (warm) East Pacific and warm (cold) West Pacific

Numerical Simulation for Tropospheric Ozone

1990, 1(1): 45-55.

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An one-dimensional atmopheric chemical model is developed. Using the model, diurnal variations of ozone and other trace gases have been simulated, and several sensitive experiments have been made. The results show that increments of CH4 or CO cause O3 to increase and increment of water vapour causes O3 to decrease; in the free atmosphere O3 decreases with a rise in temperature, but in the boundary layer O3 increases; when solar radiation enhances, O3 decreases in the free atmosphere, but in the boundary layer O3 increases. In addition, the influence of the boundary layer on the distribution of trace gases is studied. It is found that the effect of the boundary layer has to be considered in the simulations for the variation of trace gases in the lower atmosphere

A Laboratory Study on the Nucleating Properties of Three AgI–type Aerosols Under Water Sub–Saturation

1990, 1(1): 57-62.

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Three kinds of AgI–type aerosols have been tested in a 2m3 isothermal cloud chamber under water sub–saturation conditions to study their ice nucleating properties. The possibility for contact nucleation is excluded in such a cloudless condition and whether there is the frozen droplet or not in the ice crystal center is taken as a sign to tell condensation freezing nucleation from deposition nucleation. The qualitative results obtained show that there are the obvious differences of three kins of AgI–type aerosols in their ice nucleating properties

The Synoptic Characters in the Eastern China During the El Nino Period

1990, 1(1): 63-70.

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The results of analyzing the 500 hPa monthly average circulation during 1951—1985 show that the occurrence of subtropical high in the El Nino period is earlier and stronger than that in the non-El Nino period. When the positive difference value of 500 hPa geopotential height between the El Nino and non-El Nino periods maintained in the western Pacific and eastern Asia, it would be unfavorable for developing the cyclonic circulation. Also, in the El Nino period, the frequencies of the cyclone and the cyclonic convergence circulation occurred in the Yellow Sea and Bohai waters of the coast of eastern China would be evidently reduced. In addition, according to the statistical data of typhoons in western Pacific and South China Sea, the typhoon in South China Sea is of very rare occurrence during the El Nino event, and the number of landing typhoon in the coast of southeastern China is reduced by 20%. Also, the landing position is located towards the south.

Large Scale Meteorological Conditions Associated with Mesoscale-Convective Cloud Clusters over Western China in Midsummer

1990, 1(1): 71-78.

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In this paper, three-dimensional environmental meteorological fields for the life processes of eighteen mesoscale- convective cloud clusters over subtropical humid region of China during July—August of 1984—1985 have been analysed. Largescale meteorological conditions and three-dimensional structures associated with ten meso- convective cloud clusters over western China are mainly studied. It is shown that they are characterized as subtropical monsoon cloud clusters. The evolutions of convective clusters through east slope of Tibetan Plateau and their environmental conditions of continuative development in the moving eastforward are discussed.

Implementation of the Parallel Algorithm for the NWP Model with IMB 4381–P03 Dual CPU

1990, 1(1): 79-85.

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This paper presents the parallel algorithm experimental results on numerical weather prediction, which have been carried out by using the dual CPU computer system consisting of three IBM 4381-P03 installed at SMC/SMA, Beijing, According to the x-and y-coordinate directive decomposion (fork)-composion (join), the IBM 4381-P03 dual CPU have executed the calculation of the model difference scheme which is conditionally stable in form but nonconditionally stable in fact. The preliminary experiment results show: (1) IBM 4381-P03 with dual CPU can excite parallel algorithm in a common separate task way. (2) MVS grand operating system controls the Multitasking Facility (MTF) in the VS FORTRAN library to execute the decomposing task—parallel processing—waiting synchronization, to carry out the parallel algorithm. It is the first time to calculate NWP model in parallel way in China. From now on, we may execute step by step the parallel algorithm on the NWP and on the satellite informations processing. (3) In our estimation, a speed-up ratio of the parallel programming for the initial value problem is about 1.3 to 1.5, but not reaches the 1.8 level of the IBM yet. So it is worth to further exploit potentialities of the dual CPU

A Microcomputer-based Remote Terminal Network of Wuhan Digitized Weather Radar System and Its Application

1990, 1(1): 86-92.

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The dissemination of weather real condition and forecast products is one of three main links in modern systems for nowcasting and very short range forcasts, Based on Wuhan Weather Radar System (WMS) in consideration to the use in China, the idea of design for microcomputer-based remote terminal network (WMSN) is outlined in this paper. The radar echo color images and weather forecasts as well as warning can be disseminated in real time to many remote users by WMSN. WMSN has put into operation for about three years, so for, the great social and economic benefits have been achieved

A Review of the Nowcasting over the World

1990, 1(1): 93-99.

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This paper mainly presents the rapid development of short range weather forecast in some countries with the development of computer and new sounding measures, especially the remote sensing technique since the 1970s. The paper puts emphasis on the short range weather forecast for meso-small scale systems, some plans in 5—10 years and problems at present as well as the coming problems in the mid–1990s in the United States of America and so on. The paper reviews the general aspects of short range weather forecast in China and presents the progress of short range weather forecast in China since the 1980s stressing on the working stations, the sounding networks and the telecommunication networks which have been establishing in the four bases of the Zhujiang Delta, the Yangtze Delta, Jingjinji (Beijing, Tianjin and Hebei Province) and the middle-upper reaches of Yangtze River, as well as the analysis research on the severe convective weather and nowcasting in these four bases

The Study on the Microthermal Weather Process in the Lower Reaches of Yangtze River in Spring and Summer and Sudden Change of Triple-frequency Harmonic

1990, 1(1): 100-106.

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In this paper, the microthermal weather process in spring and summer using wave spectrum data during 1971 to 1984 and energy spectrum data from May to July in 1972 through 1982 has been presented. It shows that the microthermal weather process often occurs in spring and summer, and it occurs most in April of spring and in July of summer. In the light of the analysis of the wave energy density spectrum, transport spectrum of momentum and angular momentum, divergent spectrum of momentum flux and index Ik and EOF expansion, the microthermal weather process in summer is closely related to the sudden change of triple-frequency harmonic. Therefore, sudden change of triple-frequency harmonic is a better indication of the microthermal weather process.

Vol.1, NO.1, 1990