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1.
1. IntroductionMuch attention has been paid to the role playedby diabatic heating in the genesis and intensificationof tropical cyclone (TC). Based on a two-dimensionalprimitive equation model, Li (1984) proposed that theevolution of TC should be different if the maximumheating appears at different height. Yang et al. (1995)found that abrupt intensification of TC at the mid-latitudes is closely related to the vertical structure ofconvective heating. May and Holland (1998) suggestedthat the… 相似文献
2.
An Effective Method for Correcting the Seasonal-Interannual Prediction of Summer Climate Anomaly 总被引：25，自引：0，他引：25
1.IntroductionTheseasonalandinterannualpredictionofsummerclimateanomaliesbyvariouscoupledclimatemodelsisakeyobjectiveoftheclimateresearchcommunityintheworld.StudiesonEINinoandSouthernOscillation(ENSO)--relatedclimatepredictabilityshowedthatpredictiveskilloutsidethetropicsisgenerallylowcomparedtothattheinthetropics,althoughsomepredictiveskillsmayexistinsomemonsoonregions(Zengetal.,1990;KumarandHoerling,1995;Brankovitchandpalmer,1997;Zengetal.,1997;Jietal.,1994;Websteretal.,1998).Eveninthe… 相似文献
3.
Effects of the Indo-China Peninsula Heat Fluxes on the 1998 South China Sea Summer Monsoon 
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下载免费PDF全文 1. IntroductionBecause the South China Sea (SCS) is one of theregions where the Asian summer monsoon onset oc-curs earliest, the SCS summer monsoon (SCSSM) hasalways been a research focus, especially in recent yearswith the implementation of the SCS Monsoon Exper-iment (SCSMEX) (e.g., Tao and Chen, 1987; Changand Chen, 1995; Lau et al., 2000; Ding and Li, 1999;Ding and Liu, 2001; Li and Wu, 2000; Xie et al., 1998;Zhang et al., 2004). Climatologically, the SCSSM on-set is a rem… 相似文献
4.
A coupled atmosphere-ocean model developed at the Institute for Space Studies at NASA Goddard Space Flight Center (Russell et al., 1995) was used to verify the validity of Haney-type surface thermal boundary condition, which linearly connects net downward surface heat flux Q to air / sea temperature difference △T by a relaxation coefficient k. The model was initiated from the National Centers for Environmental Prediction (NCEP) atmospheric observations for 1 December 1977, and from the National Ocean Data Center (NODC) global climatological mean December temperature and salinity fields at 1° ×1° resolution. The time step is 7.5 minutes. We integrated the model for 450 days and obtained a complete model-generated global data set of daily mean downward net surface flux Q, surface air temperature TA,and sea surface temperature To. Then, we calculated the cross-correlation coefficients (CCC) between Q and △T. The ensemble mean CCC fields show (a) no correlation between Q and △T in the equatorial regions, and (b) evident correlation (CCC≥ 0.7) between Q and △T in the middle and high latitudes.Additionally, we did the variance analysis and found that when k= 120 W m-2K-1, the two standard deviations, σQ and σk△T, are quite close in the middle and high latitudes. These results agree quite well with a previous research (Chu et al., 1998) on analyzing the NCEP re-analyzed surface data, except that a smaller value of k (80 W m-2K-1) was found in the previous study. 相似文献
5.
1. Introduction As an important way to study the global climate change, because of its low resolution, GCM (general circulation model) shows obvious deficiency and uncer- tainty in capturing some regional features when used in the regional climate study, and the uncertainty is even serious in regional climate simulation over East Asia (Ding et al., 2000; Zhao and Luo, 1998; Qian et al., 1999). The high-resolution regional climate model (RegCM) developed in the 1980s can provide better simu… 相似文献
6.
Dust sediments collected from 1995 to 1998 in Beijing, Dunhuang, Inner Mongolia, Kashi, the Kunlun Mountains, Lanzhou, Ningxia, the Taklimakan Desert, and Xi‘an, China, were characterized in terms of their physical, chemical, and mineralogical properties. Most aerosols and dust analysed ranged in texture from silty clay to clay loam. Their median particle diameters (Mds) generally ranged between 5 to 63μm,coinciding with those of loess from central China and the finest sand from northwestern China. The dust sediments were characterized by a predominance of SiO2 and Al2O3, followed by K2O. Their SiO2/Al2O3and K2O/SiO2 molar ratios ranged from 5.17 to 8.43 and from 0.009 to 0.0368, respectively. The mass concentration spectrum during a dust storm showed a single peak, rather than the triple peak generally observed under clear sky conditions. The dominant minerals were chlorite, illite, calcite, and dolomite.These physical, chemical, and mineralogical properties were consistent with those of aeolian soils and loess in western and central China. The results suggest that aerosols and fine-gained fractions of dust sediments collected in northern China are mainly composed of soil material transported from the arid and semiarid regions of China and Mongolia by prevailing winds. The rate of deposition and properties of dust falling on eastern China were strongly influenced by meteorological conditions, season, latitude, longitude, and altitude of the sampling sites. 相似文献
7.
By using Comprehensive Land Surface Model (CLSM), three snow cases, i.e., France Col de Porte 1993/1994, 1994/1995 and BOREAS SSA-OJP 1994/1995, were simulated. The simulated results were compared with the observations to examine the capability of the model to describe the evolutions of snow cover under two different land cover conditions. Several sensitivity experiments were performed to investigate the effects of the parameterization schemes of some snow cover internal processes and vegetation on the model results. Results suggest that the CLSM simulates the basic processes of snow cover accurately and describes the features of snow cover evolutions reasonably, indicating that the model has the potential to model the processes related to the snow cover evolution. It is also found that the different parameterization schemes of the snowfall density and snow water holding capacity have significant effects on the simulation of snow cover. The estimation of snowfall density mainly impacts the simulated snow depth, and the underestimation (overestimation) of the snowfall density increases (decreases) the snow depth simulated significantly but with little effect on the simulated snow water equivalent (SWE). The parameterization of the snow water holding capacity plays a crucial role in the evolution of snow cover, especially in the ablation of snow cover. Larger snow water holding capacity usually leads to larger snow density and heat capacity by storing more liquid water in the snow layer, and makes the temperature of snow cover and the snow ablation vary more slowly. To a smaller snow water holding capacity, contrary is the case. The results also show that the physical processes related to the snow cover variation are different, which are dependent on the vegetation existed. Vegetation plays an important role in the evolution of soil-snow system by changing the energy balance at the snow-soil surface. The existence of vegetation is favorable to the maintenance of snow cover and delays the increase of underlying soil temperature. 相似文献
8.
1. IntroductionMany studies using a variety of coupled models have reproduced ENSO like features(e.g., Hirst, 1986, 1988; Zebiak and Cane, 1987; Battisti and Hirst, 1989; Jin and Neelin, 1993;Jin, 1997; Kirtman, 1997; Kang and An, 1998; Wakata and Sarachik, 1991). But, a variety ofsolutions have been reported depending on different parameterizations of atmospheric processes, particularly the relationship between wind stress and SST anomaly, indicating that therelationship has a large i… 相似文献
9.
Impacts of cloud-induced mass forcing on the development of moist potential vorticity anomaly during torrential rains 总被引：15，自引：2，他引：13
1. Introduction The Ertel (1942) potential vorticity (PV) has beenwidely used, especially in the studies of large-scale sys-tems (Hoskins et al., 1985; McIntyre and Norton, 2000;Wu et al., 1995; Wu and Liu, 1999). The vorticityequation in quasi-geostrophic ?ows only predicts thevariation of the vorticity and cannot provide a usefulconstraint to the vorticity. PV provides a constraintfor the variation of the vorticity in the baroclinic at-mosphere (Gao et al., 1990). The PV may not bec… 相似文献
10.
In this paper, Wu and Blumen’s boundary layer geostrophic momentum approximation model (Wu and Blumen, 1982) is applied to baroclinic and non-neutral PBL, the motion equations for the PBL under the geostrophic momentum approximation are solved, in which the eddy transfer coefficient is a function of the distributions of the wind and temperature. The results are compared with those in barotropic and neutral conditions with the geostrophic momentum approximation. It is found that in the baroclinic condition, the wind distribution has both the characteristics of a steady, homogeneous and baroclinic PBL and those caused by the geostrophic momentum approximation. Those in non-neutral conditions show that they retain the intrinsic characteristics for the wind in non-neutral PBL, at the same time, the effects of the large-scale advection and local variation are also included. We can predict the wind in the non-neutral and baroclinic PBL by use of the geostrophic mo-mentum approximation when the temporal and spatial distributions of the geostrophic wind, as well as the po-tential temperatures and their variation rates at the upper and lower boundary of the PBL are given by large-scale model. Finally, the model is extended to the case over sea surface. 相似文献
11.
If the initial fields are not in geostrophic balance, the adjustment and evolution will occur in the stratified fluid, and the frontogenesis will occur under suitable conditions. The evolution is studied here with a nonhydrostatic fully compressible meso-scale model (Advanced Regional Prediction System, ARPS). Four cases are designed and compared: (i) control experiment; (ii) with different initial temperature gradient; (iii) with vapor distribution; (iv) with orographic forcing. The results show that: (1) there is an inertial oscillation in the evolution of the imbalanced flow with the frequency of the local Coriolis f, and with its amplitude de-creasing with time. The stationary balanced state can only be approached as it cannot be reached in the limit duration of time, The energy conversion ratio varies in the range of [0, 1 / 3]; (2) the stronger initial tempera-ture gradient can make the final energy conversion ratio higher, and vice versa; (3) suitable vapor distribu-tion is favorable for the frontogenesis. It will bring forward the time of the frontogenesis, strengthen the in-tensity of the cold front, and influence the final energy conversion ratio; (4) the orographic forcing has an ev-idently strengthening effect on the frontogenesis. The strengthening effect on the frontogenesis and the influ-ence on the final energy conversion ratio depend on the relative location of the mountain to the cold front. 相似文献
12.
A numerical study of geostrophic adjustment and frontogenesis 总被引：1，自引：0，他引：1
ＡＮｕｍｅｒｉｃａｌＳｔｕｄｙｏｆＧｅｏｓｔｒｏｐｈｉｃＡｄｊｕｓｔｍｅｎｔａｎｄＦｒｏｎｔｏｇｅｎｅｓｉｓＭａｊｉｄＭ．ＦａｒａｈａｎｉａｎｄＷｕＲｏｎｇｓｈｅｎｇ（伍荣生）ＤｅｐａｒｔｍｅｎｔｏｆＡｔｍｏｓｐｈｅｒｉｃＳｃｉｅｎｃｅｓ,Ｎａｎｊｉ... 相似文献
13.
利用ERA-Interim 0.125°×0.125°高分辨率逐6小时再分析数据,选取昆明准静止锋2008年1~2月长时间维持过程诊断分析了锋生函数及其各分项在锋面生消过程中的作用与贡献,并结合2016年1月20~27日锋面增强西进过程和1979年1月14~20日锋面减弱东退过程进行了比较分析。结果表明:（1）非绝热加热项对锋面生消作用较小,但存在显著的日变化。在辐射作用下,非绝热加热项日间表现为锋消,夜间为锋生。（2）西移冷气团在被高原大地形抬升过程中存在局地地形迫使冷气团下沉的情况,并导致垂直运动倾斜项表现为锋生。由于地形固定不变,局地锋生形成次级锋生带。次级锋生带与昆明准静止锋的形成、维持和东西摆动有密切的联系。（3）辐合辐散项和水平形变项是锋生函数变化的主要贡献项,其中水平形变项中的切变变形作用以锋生为主,而伸缩变形项在纬向产生锋生,在经向产生锋消。 相似文献
14.
以NCEP资料为初始场和侧边界条件,利用WRF模式对东、西天山地形对2015年12月9—12日大暴雪影响进行敏感性试验,从降水强度和分布等方面对比分析模拟结果,探讨地形在暴雪过程中的作用,对成因进行初步研究分析,结果表明:(1)此次强降雪发生是高空西南急流抽吸、低层风切变及风速辐合、偏北风与地形强迫抬升、地面冷锋移动缓慢等共同造成的。(2)此次暴雪天气过程,地形对强降雪的落区、强度影响很大,东、西天山高度与强降雪强度正相关,东、西天山高度降低、强降雪落区沿环流方向移动。(3)地形动力强迫整体上增强次级环流圈。近地面上升速度中心出现在迎风坡山脚至山腰区域,并向两侧递减,与此次大暴雪中心落区以及乌鲁木齐附近测站降雪量分布吻合,东、西天山地形高度降低50%,近地面上升速度中心值减少30%。地形强迫东、西天山峡谷近地面生成辐合中心和辐合线,辐合中心强度与地形高度正相关。(4)地形强迫抬升有加强水汽辐合汇聚的作用,东、西天山地形高度降低50%,水汽通量与水汽通量散度减少30%。 相似文献
15.
1.IntroductionTheimportanceoforographiceffectsonfrontwasrecognizedintheearly20thcentury.Butforthecomplexityofthisproblem,theinvestigationoforographiceffectsonfrontfromdynamicalviewpointisnottakenuntilthe1980s.Bannon(1983)derivedanalyticalsolutionsforthequasi--geostrophicfrontforcedbyahorizontalwinddeformationfieldthatmovesoveratwo--dimensionalmountainridge.Thesolutionsshowthatasacoldfrontapproachestheridge,itweakens,relativetotheflat--bottomsolution,andthefrontstrengthensasitmovesdowntothelees… 相似文献
16.
该文提出了冷锋的不连续传播是引起冷锋快速南移的直接原因的观点，即主冷锋南侧的锋生及其发展代替了主冷锋，在南方的锋生过程中，西南低空急流起了重要作用。 相似文献
17.
Summary Processes which played an important role in the sudden development of an intense narrow cold frontal rainband (NCFR) along the leading edge of a wintertime anafront are investigated. Quantitative analysis of the Regional Analysis and Forecast System (RAFS) initialization and Nested Grid Model (NGM) forecast fields, satellite-derived water vapor and ozone measurements, and conventional meteorological data are employed in this study.The NCFR developed upon merger of an arctic front with a nearly stationary cold front over the Appalachian mountains. Rapid intensification of an ageostrophic momentum surge associated with the formation of a sub-synoptic played a dominant role in forcing explosive frontogenesis during frontal merger. A deep tropopause fold and related mid-tropospheric subsidence feature within the entrance region of an upper-level jet crossed the mountains at the time of NCFR formation. Synthesis of the surface, NGM, and satellite data suggests that this subsidence resulted in the development of the sub-synoptic high pressure system, whose leading edge was marked by a 5mb pressure jump. Consequential amplifieation and scale contraction of the cross-front pressure gradient indicates that the scale of the merged frontal system contracted just prior to NCFR development.As precipitation developed, the pressure jump took on a microscale character and increased to 8mb amplitude. The subsequent intensity of this frontal rainband is explained by the interaction between vertical shear associated with a strong, pre-frontal, low-level jet and the gravity current-like structure at the leading edge of the merged cold front.With 22 Figures 相似文献
18.
Using National Centers for Environmental Prediction reanalysis data for the period 28 June to 12 July during 2001 to2013, the secondary circulation(SC) associated with the mei-yu front was quantitatively diagnosed by numerically solving a primitive version of the Sawyer-Eliassen equation. Results demonstrate that a direct SC exists near the mei-yu front zone during mid-summer and the synoptic-scale geostrophic deformations are the main factors determining SC structures. About94% of the sinking strength and 61% of the ascending strength in the SC are induced by the geostrophic deformations.Other terms, such as diabatic heating, ageostrophic dynamical forcing, and frictional forcing, mainly influence the fine flow pattern of the SC. The forced SC produces a frontogenesis area tilting to the north with altitude. Further diagnosis clarifies the positive feedback involving the geostrophic shear forcing and vorticity frontogenesis in the upper-level mei-yu front zone. Furthermore, statistical results indicate that all 34 deep convection cases that occurred in the warm region of the meiyu front over the period 2004-2013 experienced high-level frontogenesis associated with along-jet cold advection. The cyclonic shear forcing "moved" the monsoon SC's subsidence branch to the warm side of the mei-yu front and caused the subsidence branch to extend downwards to the lower troposphere, conducive to the initiation of deep convection in the warm region of the mei-yu front. 相似文献
19.
利用1981～2016年气象常规观测和自动站资料对南充大风的基本气候特征进行统计分析,重点探讨不同类型区域雷暴大风的天气系统配置和环境物理量基本特征。结果表明:(1)南充雷暴大风按照形成原因主要分为高空冷平流强迫类和斜压锋生类,按落区出现情况分为全市型、东部型和西部型,东部型雷暴大风主要由高空冷平流强迫所致,全市型和西部型雷暴大风过程则多为斜压锋生所造成。(2)斜压锋生类雷暴大风主要发生在显著冷暖平流导致的斜压锋生与锋面动力强迫共同作用的形势下,高空冷平流强迫类则主要是高空强干冷平流的作用。(3)雷暴大风过程发生前大气环境呈上干下湿、湿层浅薄或为“喇叭口”形态,对于不同类型雷暴大风过程发生前的环境物理结构不同,斜压锋生类雷暴大风产生时大气环境多为明显斜压特征,高空常伴有强锋区,低层不稳定能量大,因此热力因子比较重要。高空冷平流强迫类主要发生在川陕槽后强烈冷平流形势下,水平风垂直切变大、要求低层增温快,故热力和动力因子都重要。 相似文献
20.
冷锋雨带中湿物理过程与非绝热锋生的相互作用 总被引：3，自引：0，他引：3
利用包含冰相微物理过程参数化方案的三维非静力中尺度／云模式（ARPS）模拟了与冷锋有关的冷锋雨带（NCFR）结构，着重分析了锋面云系发展演变的主要特征。模拟结果表明，锋面云系是由位于锋面前沿处的锋面次级环流的上升运动激发的；锋面强度与冷锋云（雨）带中的潜热释放之间的正反馈引起的持续非绝热锋生是锋面以及冷锋雨带得以长时间维持的主要物理机制。进一步分析表明，锋区两侧位温梯度的增加是与沿着冷锋表面的倾斜上升运动引起的云水及水汽的再分布密切相关的，即在冷气团中由云水蒸发发冷却形成冷池，而在暖气团中由水汽凝结以及雨滴冻结等形成暖池，这种冷／暖池在冷／暖气团上的叠加是引起非绝热锋生的关键。 相似文献