球层中高阶自由热对流格局及其变化的研究   总被引：4，自引：1，他引：3       下载免费PDF全文

朱涛  冯锐 《地震学报》2005,27(1):11-24

研究了下边界为应力自由边界, 上边界为刚性边界, 纯粹从底部加热的充满了无穷大普朗特数的Boussinesq流体的同心球层中的非线性自由热对流. 借鉴将极型场和扰动温度场展成勒让德多项式（以下称零级数模型, 即此时m=0）的方法, 将它们展成6阶6级（即l=6; m=0, 1, 2, hellip;, l）的勒让德函数（以下称高级数模型）, 并用Galerkin方法求解非线性方程组, 获得了高级数模型的结果. 与零级数模型仅能获得表征物质垂直运移特征和扰动温度结构的二维南北向（rphi;）剖面相比, 高级数模型还得到了东西向（rphi;）和深度剖面（theta;phi;）, 而且对流运动的许多细特征得以体现, 有利于深化认识球层中自由热对流的特征及其导致的温度结构. 瑞利数的大小对自由热对流的格局和速率产生了重要的影响, 控制着对流层中高温热柱区和低温冷柱区的相对大小. 本文所得到的结果可能主要反映了下地幔物质运动, 其对流格局和速率在不同的位置上存在明显的差异, 可能蕴涵了重要的地球动力学含义.   相似文献   

热对流和强迫对流可能性的判定     

金兴章  李相臣 《气象》1989,15(9):35-37

一、热对流可能性的判定 大气中经常存在着条件性不稳定(γ_d>Y>Y_m),日常工作中常利用温度对数压力图采用气块法分析条件性不稳定,以判定热力对流的可能性。由于大气层绪状况是不断变化的,08时的探空记录仅表征探测时刻的大气层结状况,欲进行午后热对流可能的判定,应该将08时的探空记录订正到午后热对流发生前的大气层结状况。这种订正实际  相似文献   

Water-tank experiment on the thermal circulation induced by the bottom heating in an asymmetric valley   总被引：1，自引：0，他引：1  

LIU Huizhi  LIANG Bin  ZHU Fengrong  ZHANG Boyin  SANG Jianguo 《大气科学进展》2004,21(4):536-546

Water tank experiments were carried out to investigate the thermal convection due to the bottom heating in an asymmetrical valley under neutral and stably stratified approach flows with the Particle Image Velometry (PIV) visualization technique. In the neutral stratification approach flow, the ascending draft induced by bottom heating is mainly located in the center of the valley in calm ambient wind. However~with ambient wind flow, the thermal convection is shifted leeward, and the descending draft is located on the leeward side of the valley, while the ascending draft is located on the windward side. The descending draft is minorly turbulent and organized, while the ascending draft is highly turbulent. With the increase of the towing speed, the descending and ascending drafts induced by the mechanical elevation begin to play a more dominant role in the valley flow, while the role of the thermal convection in the valley airflow becomes limited. In the stable stratification approach flow, the thermal convection is limited by the stable stratification and no distinct circulation is formed in calm ambient wind. With ambient wind, agravity wave appears in the upper layer in the valley. With the increase of the ambient wind speed, a gravity wave plays an important role in the valley flow, and the location and intensity of the thermal convection are also modulated by the gravity internal waves. The thermal convection has difficulty penetrating the upper stable layer. Its exchange is limited between the air in the upper layer and that in the lower layer in the valley, and it is adverse to the diffusion of pollutants in the valley.  相似文献   

Precipitation Structures of a Thermal Convective System Happened in the Central Western Subtropical Pacific Anticyclone   总被引：5，自引：1，他引：5       下载免费PDF全文

Fu Yunfei  Feng Jingyi  Zhu Hongfang  Li Rui  Liu Dong 《Acta Meteorologica Sinica》2006,20(2):232-243

In this paper, characteristics of precipitating clouds in a thermal convective system (TCS) occurred in the southeastern mainland of China at 15:00 BT (Beijing time) on August 2, 2003 in the central western subtropical Pacific anticyclone (WSPA) is studied by using TRMM tropical rainfallmeasuring mission PR (precipitution radar) and IR Infrared radiation measurements. The precipitating cloud structures in both horizontal and vertical, relationship among storm top, cloud top, and surface rain rate are particularly analyzed. Results show that a strong ascending air at 500 hPa and a strong convergence of moisture flux at 850 hPa in the central WSPA supply necessary conditions both in dynamics and moisture for the happening of the TCS precipitation. The TRMM PR observation shows that the horizontal scale of the most TCS precipitating clouds is about 30-40 km, their averaged vertical scale is above 10 km, and the maximum reaches 17.5 km. The maximum rain rate near surface of those TCS clouds is beyond 50 mm h-1. The mean rain profile of the TCS clouds shows that its maximum rain rate at 5 km altitude is 1 km lower than the estimated freezing level of the environment. Compared with the mesoscale convective system (MCS) of "98.7.20", both systems have the same altitude of the maximum rain rate displayed from both mean rain profiles, but the TCS is much deeper than the MCS. From the altitude of the maximum rain rate to near surface, profiles show that rain rate reducing in the TCS is faster than that in the MCS, which implies a strong droplet evaporation process occurring in the TCS. Relationship among cloud top, storm top, and surface rain rate analysis indicates a large variation of cloud top when storm top is lower. On the contrary, the higher the storm top, the more consistent both cloud top and storm top. And, the larger the surface rain rate, the higher and more consistent for both cloud top and storm top. At the end, results expose that area fractions of non-precipitating clouds and clear sky are 86% and 2%, respectively. The area fraction of precipitating clouds is only about 1/8 that of non-precipitating clouds.  相似文献   

花岗质岩浆侵位对围岩裂隙发育和热结构影响的数值模拟     

卢靖雯  王勤  刘春 《地质学报》2022,96(10):3619-3638

岩浆侵位会引起围岩的接触变质作用和变形，虽然围岩中的破裂提供了流体活动和元素迁移的重要通道，但是大多数岩浆侵位模型忽略了围岩中热对流的影响。本文总结了岩浆侵位的数值模拟原理和常用模拟方法，然后使用离散元软件MatDEM建立了二维的双层围岩模型和均质围岩模型，用孔隙密度流法模拟花岗质岩浆侵位和冷却过程中岩浆与围岩之间的流- 固- 热- 力耦合过程。结果表明岩浆侵位过程中围岩的裂隙发育和热对流对接触变质晕具有重要影响，围岩的裂隙发育和热传输模式可分为三个阶段：① 岩浆侵位初期的挤压力使围岩中产生广泛分布的、呈径向展布的剪裂隙，围岩以热传导和孔隙渗流为主导；② 在持续的孔隙流体压下，径向裂隙连通形成主干张性断裂并向上扩展，成为熔/流体迁移的重要通道以及伟晶岩型和热液型矿床的成矿空间，通道流和局部热对流控制了围岩的热传输；③ 在岩浆侵位后期，岩浆房附近围岩中的孔隙流体压增大，在侵入体与围岩的接触带形成大量张裂，加强了变质晕内的热对流，有助于矽卡岩型矿床的形成。与只有热传导的模型对比，热对流使围岩中变质晕的宽度减小。接触变质晕的几何形态受侵入体的形态控制，但是变质晕宽度在空间上有显著差异。本研究为重建岩浆侵位过程中的变质- 变形- 成矿作用提供了新方法。  相似文献   

塔克拉玛干沙漠夏季晴空对流边界层大涡模拟     

王敏仲  徐洪雄  王寅钧  买买提艾力&#  买买提依明  张建涛 《中国沙漠》2018,38(6):1275-1286

为了探索塔克拉玛干沙漠夏季晴空对流边界层湍流结构和热对流运动规律,利用沙漠腹地探空及地表通量观测资料,开展了晴空对流边界层的大涡模拟研究。结果表明：（1）沙漠夏季晴空条件下,对流边界层湍能主要由地表热力浮力对流产生,机械剪切对边界层湍能的贡献较小,小尺度湍涡对湍能的耗散随高度呈减弱趋势,边界层湍能变化呈现间歇性特点。（2）沙漠夏季晴空边界层中存在着有组织的热对流泡现象,热泡最大上升速度可超过4.0 m·s^-1;沙漠热对流运动一般呈羽状和网状分布特征,在上升运动区周围伴随有大片的下沉辐散区域。（3）地表感热和逆温层顶盖强度是控制和影响沙漠对流边界层发展的两个重要因素,感热增大,对流边界层变暖且高度升高;感热减小,对流边界层变冷且高度降低。在感热不变的条件下,逆温层顶盖强度越强,越不利于对流边界层发展,反之则相反。  相似文献   

漠河市一次漏报热对流天气分析     

许丽玲  韩凤岐  张友谊  张春梅 《黑龙江气象》2022,39(1):41-44

  相似文献   

Seasonal variability of zonal heat advection in the mixed layer of the tropical Pacific     

官聪  陈永利  王凡 《中国海洋湖沼学报》2013,31(6):1356-1367

Zonal heat advection （ZHA） plays an important role in the variability of the thermal structure in the tropical Pacific Ocean, especially in the western Pacific warm pool （WPWP）. Using the Simple Ocean Data Assimilation （SODA） Version 2.02/4 for the period 1958-2007, this paper presents a detailed analysis of the climatological and seasonal ZHA in the tropical Pacific Ocean. Climatologically, ZHA shows a zonal- band spatial pattern associated with equatorial currents and contributes to forming the irregular eastern boundary of the WPWP （EBWP）. Seasonal variation of ZHA with a positive peak from February to July is most prominent in the Nifio3.4 region, where the EBWP is located. The physical mechanism of the seasonal cycle in this region is examined. The mean advection of anomalous temperature, anomalous advection of mean temperature and eddy advection account for 31%, 51%, and 18% of the total seasonal variations, respectively. This suggests that seasonal changes of the South Equatorial Current induced by variability of the trade winds are the dominant contributor to the anomalous advection of mean temperature and hence, the seasonality of ZHA. Heat budget analysis shows that ZHA and surface heat flux make comparable contributions to the seasonal heat variation in the Nifio3.4 region, and that ZHA cools the upper ocean throughout the calendar year except in late boreal spring. The connection between ZHA and EBWP is further explored and a statistical relationship between EBWP, ZHA and surface heat flux is established based on least squares fitting.  相似文献   

上海地区近10年冷流降雪天气诊断分析   总被引：4，自引：2，他引：2  

陈雷  戴建华  韩雅萍 《气象》2012,38(2):182-187

统计了近10年发生在上海地区的冷流降雪过程,初步揭示了此类天气过程的产生机理,并分析了降雪发生时对应的高低空天气形势、探空图、卫星云图和雷达回波特征。结果表明：上海地区2000—2009年共出现冷流降雪12次,占降雪总日数的25%,大部分过程降雪明显时段高空500 hPa上海处在槽前。冷流降雪发生前,宝山站探空图上,低层有不稳定层结,且850～925 hPa湿度较大。冷流降雪对应的红外云图,云阶走向和海岸线一致,且云体呈白亮波状结构,云顶高度多在3000m以下,雷达反射率因子较弱,多低于35 dBz。绝大部分过程海水和850 hPa温差在10～14℃之间,海水和925 hPa温差介于8～11℃之间。降雪发生时宝山站吹NW—WNW—N风,风速为3～6 m·s^-1与山东半岛相比,上海地区地理位置和地形条件决定其冷流降雪有分布范围小、持续时间短、降雪强度弱等特点。  相似文献   

传导-对流型热流的计算模拟          下载免费PDF全文

沈显杰  张菊明 《地质科学》1990,(3):278-286

本文对8个初始模型和7个组合模型中沿断层的水热对流、断层产状、山体地形和沉积盆地与基岩热导率反差等四个影响因素对传导型地表热流分布的影响进行了计算机模拟研究。模型设计和参数的选值以西藏中北部一些地热区实测的传导-对流型热流为主要参考依据,但不直接涉及对流组分的校正,而着眼于更广泛的单因子和多因素的模型研究。分析中采用无量纲参数:α=(K₁)/(K₂)(K₁和K₂分别为基岩和沉积盆地的热导率),β=(q₁)/(q₂)(q₁和q₂分别为地表热流的垂向分量和模型的底部热流)以及γ=L/H(L和H分别为离模型左侧边界的距离和山体的高度),以求更广的普适性。对模拟结果的分析表明,上述四项影响因素依其重要性可排序为对流强度—断层倾角—介质热导率反差—地形效应。  相似文献