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61.
一次三峡大暴雨的地转螺旋度分析 总被引:5,自引:4,他引:5
本文引入了地转螺旋度概念,并将其用于一次大暴雨的分析,结果发现;在地转螺旋度垂直剖面图上,在雨区上空300hPa附近有一个负的极小值中心,在500hPa有一个正的极大值中心,该分布形成原因可用图6解释。 相似文献
62.
With the marine ship observation data set obtained by three cruise-phases of Chinese Xi-angyanghong 5 from November 5,1992 to February 19,1993 in the TOGA-COARE IOP at 2°S,156°E.the sea surface fluxes at this point are estimated by three different bulk schemes.Firstly.aquasi-linear relation is found between the neutral drag coefficients and wind speed.Then,the sta-bility-dependent drag and heat transfer coefficients are solved in the iterative method.Based onthus-derived transfer coefficients,the momentum,sensible and latent heat fluxes are calculated.In the warm pool region,the fluxes corresponding to the westeily winds are much greater thanthose of the easterly trade winds.The magnitude of sea surface fluxes depends upon the atmo-spheric stability as well,in particular in the case of weak wind condition.The estimated sea sur-face net heat budget shows that considerable amount of heat transport from ocean to atmosphere ismainly produced by the effective longwave radiation,latent and sensible heat fluxes.Among themthe value of latent heat flux is the largest and the sensible heat flux is the smallest.Finally,an ac-curacy analysis is made by direct measurements with the eddy-correlation method on the JapaneseR/V Hakuho board at the same time.It is shown that the bulk-derived fluxes are acceptable withmuch confidence.The estimated effective longwave radiation is used to compare with those by di-rect observations on Xiangyanghong 5.This research is compared with TOGA investigation in thetropical western Pacific. 相似文献
63.
In this paper we consider the shot-noise model of streamflow series. We show how design discharge can be obtained by the stochastic intensity of thinned Poisson processes describing the peaks over a threshold. The main result concerns the stationary distribution of peaks. We derive an explicit expression for this limit distribution in terms of its Laplace transform. Approximation formulas are developed making use of the saddle point method for the asymptotic evaluation of contour integrals and the Post-Widder formula for inversion of Laplace transforms. We illustrate this methods on the case of Gamma-distributed shots. The stationary peak distribution is used to approximate the maximum value distribution for larger time intervals. 相似文献
64.
本文利用一个三维中尺度模式,分别采用两种不同的湿过程处理方案FPA和NCA模拟同一个洋面冷锋个例,以考察模拟结果对湿过程参数化方案的敏感性。两种方案的区别在于前一种使用了次网格湿对流参数化而后者没有。通过比较分别使用FPA和NCA方案所进行的模拟FPS和NCS,发现冷锋结构在两者间出现较大差异。从850 hPa等压面|Δθe|等值线图所显示的结构看,NCS中冷锋呈现为一长一短两条锋带,而FPS中冷锋仅呈现为一条锋带。在相应的冷锋横向垂直剖面中,NCS中存在两个相邻的锋面垂直环流,而FPS中只有一个。另外,NCS中对流不稳定的冷锋区出现垂直运动过分发展的现象,而FPS中不存在这个问题。通过与卫星云图比较,我们注意到,NCS中尽管出现了垂直运动过分发展的现象,但相对于FPS而言,其模拟的冷锋结构与实际较为接近,成功地模拟出云图上显示的双冷锋结构。NCS中垂直运动过分发展的一个重要原因是模式中采用的静力平衡近似。FPS中次网格对流参数化方案的使用,通过减少甚至消除对流不稳定度,一方面使垂直运动的过分发展倾向受到约束,另一方面也可能使在对流不稳定层结下的锋区环境中本应出现的中尺度结构失去了形成的机会。 相似文献
65.
66.
In the estimation of momentum fluxes over land surfaces by the bulk aerodynamic method, no unique value of the drag coefficient
(C
D) is found in the literature. The drag coefficient is generally estimated from special observations at different parts of
the world. In this study an attempt is made to estimate drag coefficient over the western desert sector of India using data
sets of Monsoon Trough Boundary Layer Experiment (MONTBLEX) during the summer monsoon season of 1990. For this purpose, the
fast and slow response data sets obtained simultaneously from a 30 m high micro-meteorological tower at Jodhpur are used.
All the observations used in this study are confined to a wind speed regime of 2.5–9.0 ms−1.
A comparison of momentum fluxes computed by eddy correlation (direct estimation) with profile and bulk aerodynamic (C
D = 3.9 × 10−3, Garratt, 1977) methods revealed that though the nature of variation of the fluxes by all these methods is almost similar,
both the indirect methods give an under-estimated value of the fluxes. The drag coefficient is estimated as a function of
wind speed and surface stability by a multiple regression approach. An average value of the estimated drag coefficient is
found to be of the order of 5.43 × 10−3. The estimated value ofC
D is validated with a set of independent observations and found to be quite satisfactory. The recomputed momentum fluxes by
bulk aerodynamic method using the estimated drag coefficient are in close agreement with the directly estimated fluxes. 相似文献
67.
68.
69.
1 Introduction The mean meridional circulation plays an important role in the transportation and balance of heat, momen- tum, vortex and vapor between different latitudes. According to the data analysis, there are three circula- tions from the equator to the polar area: the Hadley circulation, a heat-driven circulation which rises around the equator and sinks at a certain latitude; the subpolar circulation, another heat-driven circulation around the polar area; and the Ferrel circulation, an i… 相似文献
70.
The common-ray approximation eliminates problems with ray tracing through S-wave singularities and also considerably simplifies
the numerical algorithm of the coupling ray theory for S waves, but may introduce errors in travel times due to the perturbation
from the common reference ray. These travel-time errors can deteriorate the coupling-ray-theory solution at high frequencies.
It is thus of principal importance for numerical applications to estimate the errors due to the common-ray approximation applied.
The anisotropic-common-ray approximation of the coupling ray theory is more accurate than the isotropic-common-ray approximation.
We derive the equations for estimating the travel-time errors due to the anisotropic-common-ray (and also isotropic-common-ray)
approximation of the coupling ray theory. The errors of the common-ray approximations are calculated along the anisotropic
common rays in smooth velocity models without interfaces. The derivation is based on the general equations for the second-order
perturbations of travel time. 相似文献