首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 543 毫秒
1.
The coupling between the stratosphere and the troposphere has been investigated by analysing low-frequency variations in: (1) the meridional mass flux into the polar cap (north of 60°N), computed separately for the stratosphere and the troposphere; (2) the polar cap mean surface pressure, and (3) the surface level meridional pressure gradient and zonal wind around 60°N. The analysis has been done for the 1979–93 Northern Hemisphere (NH) winters, using ECMWF reanalysis data. The results show that for all winters the meridional mass flux variations in the stratosphere precede those in the troposphere, by about one day. This result can also be obtained qualitatively with a very simple model, based on the zonally averaged zonal and meridional momentum equations. The lag is not very sensitive to the latitude of the southern boundary of the polar cap. The analysed variations in the polar cap mean surface pressure associated with variations in the meridional mass flux, determine most of the variability in the analysed meridional surface pressure gradient and the associated surface zonal wind around 60°N. The results also show that in the stratosphere the Coriolis force associated with the zonal-mean meridional wind is in near-balance with the convergence of the eddy momentum flux, and in the lower troposphere with the zonal frictional force. In summary, the results indicate that in the extratropical northern winter hemisphere, low-frequency variations in the meridional wind in the stratosphere induce low-frequency variations in the zonal wind near the surface.  相似文献   

2.
The generation mechanisms of convective gravity waves in the stratosphere are investigated in a three-dimensional framework by conducting numerical simulations of four ideal storms under different environmental conditions: one un-sheared and three constant low-level sheared basic-state winds with the depth of the shear layer of 6 km and the surface wind speeds (Us) of 8, 18, and 28 m s?1, using the Advanced Regional Prediction System (ARPS) model. The storms simulated under the un-sheared (Us = 0 m s?1), weakly sheared (Us = 8 and 18ms?1), and strongly sheared (Us = 28ms?1) basicstate winds are classified into single-cell, multicell, and supercell storms, respectively. For each storm, the wave perturbations in a control simulation, including nonlinearity and microphysical processes, are compared with those in quasi-linear dry simulations forced by diabatic forcing and nonlinear forcing that are obtained from the control simulation. The gravity waves generated by the two forcing terms in the quasi-linear dry simulations are out of phase with each other for all of the storms. The gravity waves in the control simulation are represented by a linear sum of the wave perturbations generated by the nonlinear forcing and diabatic forcing. This result is consistent with the results of previous studies in a two-dimensional framework. This implies that both forcing mechanisms are important for generating the convective gravity waves in the three-dimensional framework as well. The characteristics of the three-dimensional gravity waves in the stratosphere were determined by the spectral combination of the forcing terms and the wave-filtering and resonance factor that is determined from the basic-state wind and stability as well as the vertical structure of the forcing.  相似文献   

3.
The stratospheric quasi-zero wind layer (QZWL) is a transition region with low zonal wind speeds in the lower stratosphere at an altitude of ~20 km. The zonal wind direction above the QZWL layer is opposite to that below the QZWL layer and the north–south wind component is small. The atmospheric wind field near the stratospheric QZWL is an important factor affecting the flight altitude and dynamic control of stratospheric airships. It is therefore necessary to study the stratospheric QZWL to provide better environmental information for these aircraft. High-resolution radiosonde data were used to analyze the characteristics of the stratospheric QZWL over Korla, Xinjiang Province, China. A weak wind layer in which the wind direction suddenly reversed from westerly to easterly was observed at ~20 km in the lower stratosphere, characteristic of the stratospheric QZWL. The Weather Research and Forecasting model was used to simulate the profiles of the horizontal wind speed and direction over Korla. The forcing effect of each diagnostic term in the equation on the zonal wind speed was analyzed. The results showed that the advection term was the dominant factor forcing the zonal wind speed. The wave term had a secondary forcing role, although the forcing effect of the wave term on the zonal wind speed was significant in some regions.  相似文献   

4.
A cloud-resolving model is configured to span the full meridional extent of the tropical atmosphere and have sufficient zonal extent to permit the representation of tropical cloud super-clusters. This is made computationally feasible by the use of anisotropic horizontal grids where one horizontal coordinate direction has over an order of magnitude finer resolution than the other direction. Typically, the meridional direction is chosen to have the coarser resolution (40 km grid spacing) and the zonal direction has enough resolution to ‘permit’ crude convective squall line ascent (1 km grid spacing). The aim was to run in cloud-resolving model (CRM) mode yet still have sufficient meridional resolution and extent to capture the equatorial trapped waves and the Hadley circulation. The large-scale circulation is driven by imposed uniform tropospheric cooling in conjunction with a fixed sea surface temperature distribution. At quasi-equilibrium the flow is characterized by sub-tropical jetstreams, tropical squall line systems that form eastward-propagating super-clusters, tropical depressions and even hurricanes.Two scientific issues are briefly addressed by the simulations: what forces the Hadley circulation and the nature of stratospheric waves appearing in the simulation. It is found that the presence of a meridional sea surface temperature gradient is not sufficient on its own to force a realistic Hadley circulation even though convection communicates the underlying temperature gradient to the atmosphere. It is shown in a simulation that accounts for the observed time and zonal-mean momentum forcing effect of large-scale eddies (originating in middle latitudes) that the heaviest precipitation is concentrated near the equator in association with moisture flux convergence driven by the Trade winds.A spectral analysis of the stratospheric waves found on the equator using the dispersion relation for equatorially-trapped waves provides strong evidence for the existence of a domain-scale Kelvin wave together with eastward and westward propagating inertia-gravity waves. The eastward-propagating stratospheric waves appear to be part of a convectively coupled wave system travelling at about 15 ms−1.  相似文献   

5.
平流程准两年振荡(QBO)是赤道平流层(～100-1 hPa)变率的主要模态,可对中高纬地区的环流产生重要影响,但目前利用通用大气环流模式(GCM)对其进行准确模拟仍然是一个挑战.本文利用IAP大气环流模式(IAP-AGCM)的中高层大气模式版本(IAP-AGCML69)对QBO进行模拟,并对其动量收支情况进行分析.研究发现,QBO主要是由对流活动引起的重力波强迫(参数化)引起的,但该动量强迫被平流层赤道上升流所引起的平流过程显著削弱.模式可分辨尺度的波动强迫对赤道上空的QBO的总纬向风倾向有正贡献,在上平流层,其量值大小与参数化的重力波强迫相当.以上结果提供了QBO形成机制以及模式模拟差异可能原因的认识.  相似文献   

6.
Characteristics and sources of inertia-gravity waves are investigated using high-resolution radiosonde data observed at ten stations in Korea during 15 June to 15 July 2007. The wave analyses are performed in the lower stratospheric region (Z = 17–30 km). The average intrinsic frequency, vertical wavelength, and horizontal wavelength for the observed waves are 2.77f (where f is the Coriolis parameter), 2.58 km, and 620.11 km, respectively. The average eastward and westward momentum fluxes are 0.005 m2 s?2 and ?0.003 m2 s?2, respectively, and the average northward and southward momentum fluxes are 0.007 m2 s?2 and ?0.002 m2 s?2, respectively. To understand the propagation and the sources of the observed gravity waves, a three-dimensional ray-tracing model is used. The observed gravity waves are classified into two groups based on the existence of convection when and where the rays reach altitudes of 6–13 km. Sources are mostly located in the northeast and southeast of the observation stations below Z = 5 km for the convection-related cases (CONV), while those for the other cases (NCONV) are located in the northeast and southeast of the observation stations above Z = 20 km. The average intrinsic frequency and vertical wavelength of the CONV cases are somewhat larger than those of the NCONV cases. The average potential, kinetic, and total wave energies of the CONV cases are less than those of the NCONV cases.  相似文献   

7.
Summary Seasonal variations of gravity wave characteristics are investigated using rawinsonde data observed at Pohang observatory, Korea (36°2′N, 129°23′E) during the one-year period of 1998. Analysis is carried out for two atmospheric layers representing the troposphere (2–9 km) and stratosphere (17–30 km). There exist clear seasonal variations in amplitudes of temperature and wind perturbations and wave energy in the stratosphere, with their maxima in wintertime and minima in summertime. A strong correlation is found between the wave activity and the strength of the jet stream, but there is no clear correlation between the wave activity and the vertical gradient of static stability. The intrinsic frequency and vertical and horizontal wavelengths of gravity waves in the stratosphere are 2f–3f, where f is the Coriolis parameter, and 2–3 km and 300–500 km, respectively. The intrinsic phase velocity directs westward in January and northeastward in July. The vertical flux of the stratospheric zonal momentum is mostly negative except in summertime with a maximum magnitude in January. Topography seems to be a major source of stratospheric gravity waves in wintertime. Convection can be a source of gravity waves in summertime, but it is required to know convective sources at nearby stations, due to their intermittency and locations relative to floating balloons.  相似文献   

8.
A cloud-resolving model is configured to span the full meridional extent of the tropical atmosphere and have sufficient zonal extent to permit the representation of tropical cloud super-clusters. This is made computationally feasible by the use of anisotropic horizontal grids where one horizontal coordinate direction has over an order of magnitude finer resolution than the other direction. Typically, the meridional direction is chosen to have the coarser resolution (40 km grid spacing) and the zonal direction has enough resolution to ‘permit’ crude convective squall line ascent (1 km grid spacing). The aim was to run in cloud-resolving model (CRM) mode yet still have sufficient meridional resolution and extent to capture the equatorial trapped waves and the Hadley circulation. The large-scale circulation is driven by imposed uniform tropospheric cooling in conjunction with a fixed sea surface temperature distribution. At quasi-equilibrium the flow is characterized by sub-tropical jetstreams, tropical squall line systems that form eastward-propagating super-clusters, tropical depressions and even hurricanes.Two scientific issues are briefly addressed by the simulations: what forces the Hadley circulation and the nature of stratospheric waves appearing in the simulation. It is found that the presence of a meridional sea surface temperature gradient is not sufficient on its own to force a realistic Hadley circulation even though convection communicates the underlying temperature gradient to the atmosphere. It is shown in a simulation that accounts for the observed time and zonal-mean momentum forcing effect of large-scale eddies (originating in middle latitudes) that the heaviest precipitation is concentrated near the equator in association with moisture flux convergence driven by the Trade winds.A spectral analysis of the stratospheric waves found on the equator using the dispersion relation for equatorially-trapped waves provides strong evidence for the existence of a domain-scale Kelvin wave together with eastward and westward propagating inertia-gravity waves. The eastward-propagating stratospheric waves appear to be part of a convectively coupled wave system travelling at about 15 ms−1.  相似文献   

9.
夏季亚洲季风区是对流层向平流层物质输送的主要通道,其对平流层水汽的变化有重要贡献。以往的研究表明亚洲季风区向平流层的水汽传输主要在青藏高原及周边地区。本文利用多年平均的逐日ERAi、MERRA再分析数据和微波临边观测仪（Microwave Limb Sounder,MLS）数据,首先对比分析夏季青藏高原周边上空水汽的分布特征,再利用再分析资料分析了对流层—平流层水汽传输的特征。结果表明:青藏高原周边特定的等熵面和对流层顶结构分布有利于水汽向平流层的绝热输送;在南亚高压的东北侧,从青藏高原到中太平洋地区,340~360 K层次存在最为显著的水汽向平流层的纬向等熵绝热输送通道,7~8月平均输送强度可达约7×103 kg s-1。此外,在伊朗高原及南亚高压的西部,350~360 K层次也存在一支水汽向平流层的经向等熵绝热输送通道,但强度相对较弱（约2.5×103 kg s-1）。在青藏高原南侧370~380 K层次存在强的水汽向平流层的非绝热输送,主要由深对流和大尺度上升运动引起,7~8月平均输送强度约0.4×103 kg s-1。落基山以东到大西洋西部,350~360 K层次存在水汽向平流层的纬向等熵绝热输送通道,但强度也弱得多（约2.5×103 kg s-1）。  相似文献   

10.
本文综述了近年来关于平流层大气动力学及其与对流层大气相互作用动力过程的研究进展,特别是回顾了近年来关于平流层大气环流和行星波动力学、热带平流层大气波动及其与基本气流相互作用、平流层大气环流变异对对流层环流和气候变异的影响及其动力过程、平流层大气数值模拟以及在全球变暖背景下平流层大气的长期演变趋势预估等的研究进展。最近的研究揭示了大气准定常行星波传播波导的振荡现象、重力波在热带平流层准两年振荡和全球物质输送中的作用、平流层长期的变冷趋势变化、平流层在对流层天气和气候变化中的作用等现象,表明了平流层大气动力学研究的重要性。平流层大气动力学的深入研究,以及对数值模式中平流层模拟性能的提高,最终都会推动整个大气科学和气候变化研究的进一步发展。  相似文献   

11.
王林  陈文  黄荣辉 《大气科学》2007,31(3):377-388
利用高分辨率的再分析资料ERA40，分析了纬向平均状态下北半球不同尺度的定常波对西风动量沿经向输送的气候态及其年变化。结果表明，对流层中定常波对西风动量输送最强的区域位于中纬度对流层的中上层，定常波在该区域长年向北输送纬向动量，且输送中心随季节有南北移动和强弱变化。此外，在高纬度地区的对流层中上层以及赤道对流层顶附近还有两个相对较弱的输送中心。前者对西风动量的输送长年向南，其垂直范围从对流层低层一直伸展到平流层下层，中心位置相对固定，强度有明显的季节变化。后者位置也相对固定，但输送方向随季节改变。平流层中定常波对西风动量的输送主要位于中高纬度的平流层中上层，定常波在该区域长年向北输送西风动量，中心位置非常稳定，而强度则随季节变化明显。行星尺度定常波的输送作用与总波动的输送作用非常一致，并在很大程度上决定了波动对动量输送强度的季节变化。天气尺度定常波和10波以上的短波的输送作用主要集中在中纬度对流层的中高层。前者与行星尺度定常波共同决定了该区域内的输送强度，并主导了输送中心的南北移动；后者的作用很小，除夏季外均可以忽略。作者给出的不同尺度定常波对西风动量输送的气候态分布不但可以作为日后研究其年际变化的基础，而且还可以为大气环流模式对大气环流模拟能力的评估提供重要的参考。  相似文献   

12.
Summary. ?A hydrostatic numerical model is used to simulate the lee wave event IOP3 (0000 GMT to 1200 GMT 15th October 1990) from the PYREX mountain experiment. Results from integrations at different horizontal resolutions are used to investigate the effect on surface pressure drag and the vertical flux of horizontal momentum due to orographically forced gravity waves. In particular, results showing the dependence on resolution of the partitioning between resolved and parametrized wave drag and fluxes are presented. With the model horizontal gridlength changing from 50 km to 10 km the majority of wave momentum flux changes from being parametrized to becoming resolved. More significantly, there is a change in the profile of flux with height. At 50 km resolution the largest inferred mean flow decelerations are at lower stratospheric level due to the parametrization scheme. At 10 km resolution this is shifted, with less deceleration high up and more wave deceleration lower down in the troposphere. Numerical weather prediction models are now beginning to take account of such low level drag with beneficial results. Received March 2, 1999/Revised July 15, 1999  相似文献   

13.
The radiative impacts of the stratosphere in global warming simulations are investigated using abrupt CO2 quadrupling experiments of the Coupled Model Inter-comparison Project phase 5 (CMIP5), with a focus on stratospheric temperature and water vapor. It is found that the stratospheric temperature change has a robust bullhorn-like zonal-mean pattern due to a strengthening of the stratospheric overturning circulation. This temperature change modifies the zonal mean top-of-the-atmosphere energy balance, but the compensation of the regional effects leads to an insignificant global-mean radiative feedback (?0.02 ± 0.04 W m?2 K?1). The stratospheric water vapor concentration generally increases, which leads to a weak positive global-mean radiative feedback (0.02 ± 0.01 W m?2 K?1). The stratospheric moistening is related to mixing of elevated upper-tropospheric humidity, and, to a lesser extent, to change in tropical tropopause temperature. Our results indicate that the strength of the stratospheric water vapor feedback is noticeably larger in high-top models than in low-top ones. The results here indicate that although its radiative impact as a forcing adjustment is significant, the stratosphere makes a minor contribution to the overall climate feedback in CMIP5 models.  相似文献   

14.
Abstract

The topographic stability of forced planetary waves in α β‐channel is investigated using a barotropic model. The equilibrium forced waves are the result of the interaction of a constant mean zonal wind over finite‐amplitude surface orography. Small‐amplitude perturbations of the equilibrium flows are considered that have a wavy part with the same zonal wavenumber as the forcing but an arbitrary meridional structure. The mean zonal part of the perturbations is also taken to be arbitrary. This configuration allows us to (1) isolate those instabilities that depend crucially on topography through form drag and (2) investigate non‐topographic effects on topographic instability that arise from the convergence of Reynolds stresses. A numerical stability analysis is then performed wherein the effects of truncation are emphasized.

This numerical approach casts doubts about the results obtained from some earlier studies involving various ad hoc assumptions. We find, in particular, that unstable long waves (i.e. waves with the zonal wavelength greater than the meridional wavelength) exist under superresonant conditions. This contradicts some previous results that suggest long waves are unstable only when the flow is subresonant. Further, our model reveals the existence of some interesting travelling instabilities. The latter are shown to depend on both form drag and Reynolds stresses in that these two mechanisms alternate in time in supplying the perturbation with the required energy to maintain the exponential growth.  相似文献   

15.
Atmospheric surface layer meteorological observations obtained from 20-m-high meteorological tower at Mangalore, situated along the west coast of India are used to estimate the surface layer scaling parameters of roughness length (z o) and drag coefficient (C D), surface layer fluxes of sensible heat and momentum. These parameters are computed using the simple flux–profile relationships under the framework of Monin–Obukhov (M–O) similarity theory. The estimated values of z o are higher (1.35–1.54 m) than the values reported in the literature (>0.4–0.9 m) probably due to the undulating topography surrounding the location. The magnitude of C D is high for low wind speed (<1.5 m s?1) and found to be in the range 0.005–0.03. The variations of sensible heat fluxes (SHF) and momentum fluxes are also discussed. Relatively high fluxes of heat and momentum are observed during typical days on 26–27 February 2004 and 10–11 April 2004 due to the daytime unstable atmospheric conditions. Stable or near neutral conditions prevail after 1700 h IST with negative SHF. A mesoscale model PSU/NCAR MM5 is run using a high-resolution (1 km) grid over the study region to examine the influence of complex topography on the surface layer parameters and the simulated fluxes are compared with estimated values. Spatial variations of the frictional velocity (u *), C D, surface fluxes, planetary boundary layer (PBL) height and surface winds are noticed according to the topographic variations in the simulation.  相似文献   

16.
Aerodynamic roughness of the sea surface at high winds   总被引：2，自引：0，他引：2  
The role of the surface roughness in the formation of the aerodynamic friction of the water surface at high wind speeds is investigated. The study is based on a wind-over-waves coupling theory. In this theory waves provide the surface friction velocity through the form drag, while the energy input from the wind to waves depends on the friction velocity and the wind speed. The wind-over-waves coupling model is extended to high wind speeds taking into account the effect of sheltering of the short wind waves by the air-flow separation from breaking crests of longer waves. It is suggested that the momentum and energy flux from the wind to short waves locally vanishes if they are trapped into the separation bubble of breaking longer waves. At short fetches, typical for laboratory conditions, and strong winds the steep dominant wind waves break frequently and provide the major part of the total form drag through the air-flow separation from breaking crests, and the effect of short waves on the sea drag is suppressed. In this case the dependence of the drag coefficient on the wind speed is much weaker than would be expected from the standard parameterization of the roughness parameter through the Charnock relation. At long fetches, typical for the field, waves in the spectral peak break rarely and their contribution to the air-flow separation is weak. In this case the surface form drag is determined predominantly by the air-flow separation from breaking of the equilibrium range waves. As found at high wind speeds up to 60 m s−1 the modelled aerodynamic roughness is consistent with the Charnock relation, i.e. there is no saturation of the sea drag. Unlike the aerodynamic roughness, the geometrical surface roughness (height of short waves) could be saturated or even suppressed when the wind speed exceeds 30 m s−1.  相似文献   

17.
A climatology of the stratosphere is determined from a 20-year integration with the stratospheric version of the Atmospheric General Circulation Model LMDz. The model has an upper boundary at near 65 km, uses a Doppler spread non-orographic gravity waves drag parameterization and a subgrid-scale orography parameterization. It also has a Rayleigh damping layer for resolved waves only (not the zonal mean flow) over the top 5 km. This paper describes the basic features of the model and some aspects of its radiative-dynamical climatology. Standard first order diagnostics are presented but some emphasis is given to the model’s ability to reproduce the low frequency variability of the stratosphere in the winter northern hemisphere. In this model, the stratospheric variability is dominated at each altitudes by patterns which have some similarities with the arctic oscillation (AO). For those patterns, the signal sometimes descends from the stratosphere to the troposphere. In an experiment where the parameterized orographic gravity waves that reach the stratosphere are exaggerated, the model stratosphere in the NH presents much less variability. Although the stratospheric variability is still dominated by patterns that resemble to the AO, the downward influence of the stratosphere along these patterns is near entirely lost. In the same time, the persistence of the surface AO decreases, which is consistent with the picture that this persistence is linked to the descent of the AO signal from the stratosphere to the troposphere. A comparison between the stratospheric version of the model, and its routinely used tropospheric version is also done. It shows that the introduction of the stratosphere in a model that already has a realistic AO persistence can lead to overestimate the actual influence of the stratospheric dynamics onto the surface AO. Although this result is certainly model dependent, it suggests that the introduction of the stratosphere in a GCM also call for a new adjustment of the model parameters that affect the tropospheric variability.  相似文献   

18.
The drag coefficient C d (10 m) at the center of shallow Lake Flevo (20-km diam) is evaluated for wind speeds u between 5 and 15 m s?1 independently by three methods. Trivane measurements of eddy-correlation fluxes agree with eddy flux data available for moderate wind speeds from other sites, and can together be represented by C d(10 m) = 0.0007 μ0.3. Additional evaluations of water-surface slope give C d(10 m) ≈ 0.0024, indicating that the stress at the water-surface level may not be entirely accounted for by eddy-correlation measurements well above the waves. Neither the eddy-correlation stress, nor the water-surface stress appears to be accurately estimable from profile measurements of wind, temperature and humidity analyzed without regard to sea state, if u > 10 m s?1.  相似文献   

19.
A systematic comparison of wind profiles and momentum exchange at a trade wind site outside Oahu, Hawaii and corresponding data from the Baltic Sea is presented. The trade wind data are to a very high degree swell dominated, whereas the Baltic Sea data include a more varied assortment of wave conditions, ranging from a pure growing sea to swell. In the trade wind region swell waves travel predominantly in the wind direction, while in the Baltic, significant cross-wind swells are also present. Showing the drag coefficient as a function of the 10-m wind speed demonstrates striking differences for unstable conditions with swell for the wind-speed range 2 m s?1 < U 10 < 7 m s?1, where the trade-wind site drag values are significantly larger than the corresponding Baltic Sea values. In striking contrast to this disagreement, other features studied are surprisingly similar between the two sites. Thus, exactly as found previously in Baltic Sea studies during unstable conditions and swell, the wind profile in light winds (3 m s?1) shows a wind maximum at around 7–8 m above the water, with close to constant wind speed above. Also, for slightly higher wind speeds (4 m s?1 < U 10 < 7 m s?1), the similarity between wind profiles is striking, with a strong wind-speed increase below a height of about 7–8 m followed by a layer of virtually constant wind speed above. A consequence of these wind-profile features is that Monin–Obukhov similarity is no longer valid. At the trade-wind site this was observed to be the case even for wind speeds as high as 10 m s?1. The turbulence kinetic energy budget was evaluated for four cases of 8–16 30- min periods at the trade-wind site, giving results that agree very well with corresponding figures from the Baltic Sea.  相似文献   

20.
A self-contained derivation of the IPESD models [Majda, A.J., Klein, R., 2003. Systematic multi-scale models for the tropics. J. Atmos. Sci. 60, 393–408] governing synoptic and planetary scale tropical flows is provided. This derivation demonstrates the analytic tractability of the model and the effect of zonally and meridionally tilted synoptic scale heating on the forcing of planetary scale flows through upscale momentum and temperature fluxes. Exploiting the analytic tractability of the models, different aspects of the planetary scale forcing are traced to meridional and vertical tilts in the synoptic scale heating profile. Variants of the archetypal IPESD models for the Madden–Julian oscillation (MJO) presented in Majda and Biello [Majda, A.J., Biello, J.A., 2004. A multi-scale model for tropical intraseasonal oscillations. Proc. Natl. Acad. Sci. 101, 4736–4741; Biello, J.A., Majda, A.J., 2005. A new multi-scale model for the Madden–Julian oscillation. J. Atmos. Sci. 62, 1694–1721] are studied. In addition to vertically tilted synoptic scale heating, the models discussed herein incorporate upscale zonal momentum flux due to meridional flux convergence arising from meridionally tilted heating. The effect of a boundary layer momentum drag at the base of the free troposphere is also systematically incorporated into the IPESD models. Both meridional tilts and lower boundary layer drag are shown to meridionally confine the MJO westerly wind burst and drive a planetary scale barotropic flow. Meridionally tilted heating can also greatly strengthen the wind burst at the base of the troposphere and modify its vertical profile. The competing effects of meridionally tilted, and off-equatorial heating can also significantly weaken the MJO winds. Appendices are provided which discuss generalizations and a solution algorithm for the IPESD models.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号