Tidal Vorticity around a Coastal Promontory     

Moon-Jin Park  Dong-Ping Wang 《Journal of Oceanography》2000,56(3):261-273

The vorticity generation around a coastal promontory is examined using a transport vorticity equation. The complete vorticity balance analysis is made for the transient and residual vorticity generations around an idealized, symmetric promontory. The topographic vorticity tendency is found to be the dominant forcing term in the production of transient tidal vorticities. This result is different from the previous works which emphasized the effects of lateral and bottom frictions. The residual vorticity balance is between advection and topographic vorticity tendency. The model results are consistent with the observations off Gay Head, Massachusetts. Also, the stability of a promontory as well as the offshore sand bank formation are studied by examining the sand transport pattern around the promontory. Strong deposition occurs off the tip of the promontory while erosion occurs along the upstream slope of the promontory suggesting that an originally symmetric promontory tends to incline cyclonically from the axis normal to the tidal stream. Such tendency is indeed found among coastal promontories.  相似文献   

Convective instability of thickening mantle lithosphere     

Clinton P. Conrad 《Geophysical Journal International》2000,143(1):52-70

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华南锋面与暖区暴雨个例对比分析   总被引：14，自引：1，他引：13  

赵玉春  李泽椿  肖子牛 《气象科技》2008,36(1):47-54

分析了1961～1999年亚洲热带近海海温与云南降水的关系.通过研究云南夏季降水对近海海温异常的响应,发现云南初夏的降水与亚洲热带近海海温有明显的负相关关系,这种降水减少海温正距平的情况在北印度洋西部和阿拉伯海表现比孟加拉湾和南海更显著,但是在盛夏相关关系不显著.同时发现云南西南部的夏季降水与前期盂加拉湾海温有显著的正相关,而与其它海域的海温相关不显著.滇东南的夏季降水只与前期南海的海温有显著的正相关.  相似文献   

山西2006年雨季天气气候特征分析     

姚彩霞  杨英  任璞  郭俊龙  郝建萍 《气象科技》2008,36(1):74-77

2005年6月17～24日,华南地区发生了连续多日的暴雨天气过程,其显著特征是存在着南北两条雨带,北支雨带(福建中北部)由准静止的梅雨锋造成,南支雨带(广东中东部)发生在锋前暖区之中,这种连续多日共存的双雨带现象引起了气象学家的广泛关注.为了探究锋面和锋前暖区暴雨的成因,加深这两类不同性质暴雨的认识,利用NCEP每6 h一次的1°×1°经纬度再分析资料以及华南地区加密观测的逐小时地面降水等资料,以此次连续多日维持的双雨带降水过程为例,详细分析了锋面附近与锋前暖湿区内暴雨系统的主要物理差异.结果发现:梅雨锋暴雨和锋前暖区暴雨不仅在中尺度雨团活动、系统动力结构、大气不稳定机制和大气加热结构等存在明显的差异,而且在水汽输送、中尺度环境以及与暴雨有关的垂直环流之间也存在着不同点,这些差异可能是造成锋前暖区暴雨难以模拟和预报的主要原因.  相似文献   

海南雷暴气候特征及大气环流背景分析   总被引：12，自引：2，他引：10  

郭冬艳  辛吉武  吴胜安  姜涛  杨昌贤  陈红 《气象科技》2008,36(4):404-409

利用1966～2005年海南地区18个市、县逐日雷暴观测资料及NECP再分析资料和EOF分析方法,分析了海南地区雷暴天气的气候特征及其气候变化的可能影响因素.结果表明:海南雷暴的年际变化呈较明显的下降趋势;空间分布丰要旱现北部内陆地区多、南部沿海地区少的特点;全省雷暴集中发牛在4～10月,盛发期在5～9月;雷暴异常年5～9月平均大气环流与同期500 hPa大气环流特征的关系表现在雷暴频繁年低纬地区的位势高度距平场出现大范围的负距平.当年夏季西太平洋副热带高压较弱,位置偏东,雷暴偏少年则副高较强,脊线偏西.不稳定凶子K指数和TT指数对海南的雷暴有一定预报能力.  相似文献   

地电阻率供电回路故障检测板的研制与使用     

郅红魁  赵彦旭  付靖  谢佳兴  尚淑珍 《地震地磁观测与研究》2021,42(1):69-75

地电阻率仪器在工作中容易出现无电流、电流不稳等故障现象,不易排查维修.通过对仪器工作原理和供电回路过程进行研究,发现供电回路中间仪器的内部或外部各接头接触不良是造成上述现象的主要因素.根据存在的问题,洛阳地震台研制出供电回路故障检测板.该检测板可利用其继电器上LED灯的工作状态和动作时序,快速查找、排除相关供电回路故障...  相似文献   

Properties and stability of a meso-scale line-form disturbance   总被引：1，自引：0，他引：1  

沈新勇  丁一汇  赵南 《大气科学进展》2006,23(2):282-290

By using the 3D dynamic equations for small- and meso-scale disturbances, an investigation is performed on the heterotropic instability (including symmetric instability and traversal-type instability) of a zonal line-like disturbance moving at any angle with respect to basic flow, arriving at the following results: (1) with linear shear available, the heterotropic instability of the disturbance will occur only when flow shearing happens in the direction of the line-like disturbance movement or in the direction perpendicular to the disturbance movement, with the heterotropic instability showing the instability of the internal inertial gravity wave; (2) in the presence of second-order non-linear shear, the disturbance of the heterotropic instability includes internal inertial gravity and vortex Rossby waves. For the zonal line-form disturbance under study, the vortex Rossby wave has its source in the second-order shear of meridional basic wind speed in the flow and propagates unidirectionally with respect to the meridional basic flow. As a mesoscale heterotropic instable disturbance, the vortex Rossby wave has its origin from the second shear of the flow in the direction perpendicular to the line-form disturbance and is independent of the condition in the direction parallel to the flow; (3) for general zonal line-like disturbances, if the second-order shear happens in the meridional wind speed, i.e., the second shear of the flow in the direction perpendicular to the line-form disturbance, then the heterotropic instability of the disturbance is likely to be the instability of a mixed Rossby–internal inertial gravity wave; (4) the symmetric instability is actually the instability of the internal inertial gravity wave. The second-order shear in the flow represents an instable factor for a symmetric-type disturbance; (5) the instability of a traversal-type disturbance is the instability of the internal inertial gravity wave when the basic flow is constant or only linearly sheared. With a second or nonlinear vertical shear of the basic flow taken into account, the instability of a traversal-type disturbance may be the instability of a mixed vortex Rossby – gravity wave.  相似文献   

Applications of conditional nonlinear optimal perturbation to the study of the stability and sensitivity of the Jovian atmosphere     

姜智娜 《大气科学进展》2006,23(5):775-783

A two-layer quasi-geostrophic model is used to study the stability and sensitivity of motions on smallscale vortices in Jupiter’s atmosphere. Conditional nonlinear optimal perturbations (CNOPs) and linear singular vectors (LSVs) are both obtained numerically and compared in this paper. The results show that CNOPs can capture the nonlinear characteristics of motions in small-scale vortices in Jupiter’s atmosphere and show great difference from LSVs under the condition that the initial constraint condition is large or the optimization time is not very short or both. Besides, in some basic states, local CNOPs are found. The pattern of LSV is more similar to local CNOP than global CNOP in some cases. The elementary application of the method of CNOP to the Jovian atmosphere helps us to explore the stability of variousscale motions of Jupiter’s atmosphere and to compare the stability of motions in Jupiter’s atmosphere and Earth’s atmosphere further.  相似文献   

高地应力围岩分区碎裂化的时间效应分析和相关参数研究   总被引：2，自引：0，他引：2  

李英杰  潘一山  章梦涛 《地质力学学报》2006,12(2):252-260

本文阐述了高地应力围岩分区碎裂化现象的形成需要经过一定的时间,但这段时间不会很长;采用蠕变理论对岩石分区碎裂化的时间效应进行了分析;推导了能够描述加速蠕变阶段的流变模型-改进的西原模型的本构方程和蠕变方程,在此基础上求出了岩石分区碎裂化发生时破裂带半径(破碎带距巷道中心的距离)的公式。   相似文献   

极点对称模态分解下陕西气候变化特征及影响因素   总被引：1，自引：0，他引：1  

申雨晨  李双双  延军平  武亚群  汪成博 《干旱区地理》2021,44(1):36-46

全球变暖背景下,受人类活动和气候系统波动共同影响,气候要素响应具有非线性、非平稳特征,如何识别气候变化多时间尺度信息,是当前研究的热点话题.基于1970—2017年气温和降水逐日数据,辅以滑动平均、趋势分析和极点对称模态分解(ESMD)等方法,对陕西3大地理单元气候时空特征进行分析,进而探讨不同海区厄尔尼诺指数与气温、...  相似文献