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对上饶市2000年6月22～23日连续暴雨的形势场以及卫星云图进行了分析,得出了一些有益的结论。 相似文献
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利用实况资料对江西省上饶市2002年6月底出现的连续暴雨过程进行了分析,揭示出产生暴雨的主要环流形势配置和一些物理量场的特征,对今后预报暴雨过程具有一定的指示意义. 相似文献
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利用螺旋度理论,对上饶市2002年"6.28"区域性连续暴雨过程进行了诊断分析.结果表明,垂直螺旋度的变化对汛期暴雨落区,特别是对流性强降水具有很好的指示意义,在高、低层螺旋度高值轴之间最有可能出现暴雨. 相似文献
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２００１年１０～１２月总的天气特点是：气温接近常年略偏高，降水北多南少，日照接近常年。２００１年１０～１２月平均气温全省大部分地区较常年偏高０．１～０．６℃。１０月平均气温全省偏高１℃以上，以瑞金市偏高２．１℃为最大。１１月除上饶市东部和南部较常年偏低外，全省其它地区接近常年。１２月除景德镇市、上饶市的东北部较常年偏高０．３～０．７℃外，全省其它地区偏低０．１～１．６℃。２００１年１０～１２月降水除吉安市的南部、赣州市较常年偏少０．４～５．２成外，全省大部分地区偏多０．６成～１．２倍。其中信江流… 相似文献
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利用2010—2019年江西省闪电定位监测数据、地理信息数据和社会经济数据,基于GIS技术、自然灾害风险评估方法和层次分析法等方法,从致灾因子、孕灾环境、承灾体3个方面,开展雷电灾害风险区划的研究,并形成江西省雷电灾害风险区划。结果表明：江西省雷电灾害的极高风险区和高风险区主要分布在南昌市、宜春市、新余市、上饶市、吉安市大部分地区和赣州小部分地区,中风险区和低风险区主要分布在九江市、萍乡市和抚州市大部分地区,该区划结果与江西省近10 a雷灾造成的人员伤亡情况大致吻合。 相似文献
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Bingrui Jia Guangsheng Zhou Fengyu Wang Yuhui Wang Ensheng Weng 《Climatic change》2007,82(1-2):211-223
Soil respiration, canopy temperature, soil moisture, above and belowground biomass were observed in 2001, 2002, 2004 and 2005
at fenced and grazed typical Leymus chinensis steppes in Inner Mongolia. Based on soil respiration data obtained by the enclosed chamber method, diurnal and seasonal dynamics
of soil respiration and their controlling factors were analyzed. The effects of grazing on diurnal and seasonal soil respirations
were not significant. The diurnal patterns of soil respiration could be expressed as a one-humped curve and the lowest and
highest values appearing from 1:00 to 3:00 and from 11:00 to 14:00, respectively. Canopy temperature had a strong influence
on the diurnal variation of soil respiration. The rates of soil respiration rose to a seasonal maximum from the middle of
June to the end of July and then gradually decreased. Soil moisture explained about 71.3% and 58.3% of the seasonal variation
in soil respiration at fenced and grazed plots, respectively, and canopy temperature only 33.9% and 39.7%. Soil respiration
rate, above and belowground biomass and soil moisture were significantly increased at the fenced plots compared to the grazed
plots (P < 0.05), but the difference was not significant in canopy temperature. The mean soil respiration rates were 247.85 and 108.31
mgCO2 m−2 h−1 during the whole experiment at fenced and grazed plots, respectively. Soil respiration rate was enhanced significantly at
the fenced plots, which might attribute to the increasing soil moisture and biomass. The response of soil respiration rate
to grazing varied among different sites and might be related to local soil moisture status. 相似文献
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The Impact Of Air-Flow Separation On The Drag Of The Sea Surface 总被引：2，自引：1，他引：2
An approach that allows assessment ofthe impact of air-flow separation (AFS) fromwave breaking fronts on the sea-surface drag is presented. Wave breaking fronts are modelled by the discontinuities of the sea-surface slope. It is assumedthat the dynamics of the AFS from wave breaking crests is similar to thatfrom the backward facing step. The form drag supported by an individualbreaker is described by the action of the pressure drop distributed alongthe forward face of the breaking front. The total stress due to the AFS isobtained as a sum of contributions from breaking fronts of different scales.Outside the breaking fronts the drag of the sea surface is supported by theviscous surface stress and the wave-induced stress. To calculate the stressdue to the AFS and the wave-induced stress a physical model of the wind-wavespectrum is used. Together with the model of the air flow described in termsof surface stresses it forms a self-consistent dynamical system for the seasurface-atmosphere where the air flow and wind waves are strongly coupled.Model calculations of the drag coefficient agree with measurements. It is shownthat the dimensionless Charnock parameter (roughness length normalized onthe square of the friction velocity and the acceleration of gravity)increases with the increase of the wind speed in agreement with fieldmeasurements. The stress due to the AFS normalized on the square of thefriction velocity is proportional to the cube of wind speed. At low windsthe viscous surface stress dominates the drag. The role of the form drag,which is the sum of the stress due to the AFS and the wave-induced stress, isnegligible. At moderate and high winds the form drag dominates. At windspeeds higher than 10 m s-1 the stress supported by the AFS becomescomparable to the wave-induced stress and supports up to 50% of the totalstress. 相似文献
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William Blumen 《Boundary-Layer Meteorology》2001,99(3):509-519
The traditional Ekman boundary-layer parameterization is introduced into the quasigeostrophic Eady baroclinic instability model and into the deformation flow model, to couple the planetary boundary layer with the inviscid interior flow aloft. An explicit time-dependent version of this parameterization is then introduced into an unbalanced zero potential vorticity model to evaluate the initial transient response. It is noted that the adaptation of the geostrophic flow to the same parameterization is different in each of the balanced models. The characteristic flow response reflects thedifferent constraints imposed by each model. Further, the zero potential vorticity condition constrains the evolution of the baroclinic geostrophic part of the flow, which leads to an unphysical flow response when the Ekman boundary-layer parameterization is employed with this unbalanced model. The barotropic part of the flow does, however, evolve in a physically consistent manner spinning down to reflect the introduction of low momentum air pumped into the interior from the boundary layer. Moreover, the transient spin-up processis shown to have an insignificant effect on this spin-down process. 相似文献
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A three-dimensional mesoscale model was used to study the effect of an urban heat island in a relatively complex situation. A heat emission inventory was carried out for an urban airshed thatincludes sources such as motor vehicles, waste heat from industries and electricity consumption. To demonstrate the relative significance of anthropogenic heat flux and variant surface characteristics, three model simulations were conducted. In the first simulation, anthropogenic heat flux was ignored and non-variant surface properties were considered for the entire modelling domain. In the second simulation, variant surface characteristics were considered. While in the third simulation, gridded anthropogenic heat flux and variant surface characteristic were utilised. From these experiments, it was inferred that an additional source of heat in urban areas can substantially affect the wind and temperature regime under light wind conditions. During the day, the anthropogenic heat flux has minimum effect on the urban temperature, however it magnifies the intensity of the convergence near the urban areas. 相似文献
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The impact of air-flow separation from breaking dominant waves is analyzed.This impact results from the correlation of the pressure drop with theforward slope of breaking waves. The pressure drop is parameterized via thesquare of the reference mean velocity. The slope of breaking waves isrelated to the statistical properties of the wave breaking fronts describedin terms of the average total length of breaking fronts. Assuming that thedominant waves are narrow and that the length of breaking fronts is relatedto the length of the contour of the breaking zone it is shown that theseparation stress supported by dominant waves is proportional to thebreaking probability of dominant waves. The breaking probability of dominantwaves, in turn, is defined by the dominant wave steepness. With thedominant wave steepness increasing, the breaking probability is increasedand so does the separation stress. This mechanism explains wave age (youngerwaves being steeper) and finite depth (the spectrum is steeper in shallowwater) dependence of the sea drag. It is shown that dominant waves support asignificant fraction of total stress (sea drag) for young seas due to theair-flow separation that occurs when they break. A good comparison of themodel results for the sea drag with several data sets is reported. 相似文献