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1.
 Zonal advection by long equatorial waves has been shown to be an important process in the evolution of sea surface temperature in the central Pacific on ENSO time scales. The present study aims at investigating how well an oceanic model whose dynamics are based on long equatorial waves can simulate the large-scale surface zonal current variability. Thus an ocean linear model which can be run with two or three layers is validated against several sets of observations in the Pacific ocean (TOPEX/POSEIDON sea level, TAO zonal currents, surface current climatology). The surface layer (mixed-layer) has a constant depth. Therefore the layer model is equivalent to considering a shear layer solution and either one or two baroclinic modes. It allows evaluation of the impact of adding a second baroclinic mode on the simulation of surface currents. This evaluation is done for different friction parametrizations: a weak linear Rayleigh friction (24 months−1), a strong linear Rayleigh friction (6 months−1), and a new parametrization using quadratic friction in the momentum equation only. It is shown in all simulations using various Rayleigh friction parametrizations that the addition of a second baroclinic mode always improves the simulation of both the sea level and the surface currents, especially in the central western Pacific. In that region, there is a reduction of the propagating long Rossby waves whose amplitude is much too large when only one baroclinic mode is used. Despite this reduction, the use of a weak friction (24 months−1) always yields results which compare only poorly to observations confirming results from previous studies. The use of strong friction (6 months−1) improves the model simulation, but surface current variability still remains too large. Finally, the use of quadratic friction as proposed in the present study considerably improves the simulation of zonal currents and its comparison to all data sets. This result gives more confidence in the choice of such a simple model to further explore the role of zonal advection by long equatorial waves on ENSO time scales. Received: 28 May 1999 / Accepted: 18 May 2000  相似文献   

2.
1.IntroductionArnol'd(1965,1969)variationalprincipleandapriorestimatemethodisessentiallyageneralizationofLyapunovstabilitymethodforfinite--dimensionaldynamicalsystemsininfinite--dimensionalones,andhestudiedthenonlinearstabilityof2--dimensionalincompressibleidealfluidmotionbyuseofthismethod,andestablishedtwotheoremswhichareArnol,d'sfirsttheoremandArnol'd'ssecondtheorem.Eversincethe1980's,manyscientistshavebeenworkingonthissubject,Holmetal.(1985);MclntyreandShepherd(1987);Zeng(1989);Muetal.(1…  相似文献   

3.
The three-dimensional nonlinear quasi-geostrophic potential vorticity equation is reduced to a linear form in the stream function in spherical coordinates for the permanent wave solutions consisting of zonal wavenumbers from 0 to n and rn vertical components with a given degree n. This equation is solved by treating the coefficient of the Coriolis parameter square in the equation as the eigenvalue both for sinusoidal and hyperbolic variations in vertical direction. It is found that these solutions can represent the observed long term flow patterns at the surface and aloft over the globe closely. In addition, the sinusoidal vertical solutions with large eigenvalue G are trapped in low latitude, and the scales of these trapped modes are longer than 10 deg. lat. even for the top layer of the ocean and hence they are much larger than that given by the equatorial β-plane solutions. Therefore such baroclinic disturb-ances in the ocean can easily interact with those in the atmosphere.Solutions of the shallow water potential vorticity equation are treated in a similar manner but with the effective depth H = RT / g taken as limited within a small range for the atmosphere.The propagation of the flow energy of the wave packet consisting of more than one degree is found to be along the great circle around the globe both for barotropic and for baroclinic flows in the atmosphere.  相似文献   

4.
Three aircraft-based studies of boundary-layer fronts (BLFs) werecarried out during the experiment KABEG in April 1997near the sea-ice edge over the Davis Strait. The zone of strongestcross-front horizontal gradients showed a typical length scaleof 20 km, while the along-front scale was observed to beseveral hundreds of kilometres.The observed BLFs were stronger than the few previously reportedcases. Horizontal gradients of potential temperature and specifichumidity ranged up to 3 K or 0.25 g kg-1over 20 km, respectively.Low-level winds were around 15 m s-1 parallel to the ice edge.The capping inversion sloped from between250 and 400 m over sea ice to between 400 and 700 m over ocean.For two BLF cases turbulent fluxes and energy budgets are calculated.Turbulent energy fluxes show a factor 2 to 3 contrast acrossthe ice edge and range from 15 to 50 W m-2 over sea iceand from 50 to 100 W m-1 over open ocean.The mean boundary-layer energy budgets are dominated bycold, dry horizontal advection, which is exceededby vertical heat flux convergence.The momentum budgets are dominated by pressure gradient force,Coriolis force and momentum flux divergence.  相似文献   

5.
南海各月月平均海流场的数值模拟   总被引:3,自引:0,他引:3       下载免费PDF全文
本文用一个区域三维、自由表面、斜压海洋模式对南海全年各月的三维平均流场进行了数值模拟,模拟得到的环境特征与己有的实测资料十分相近,这表明该模拟结果是可信的,该数值模拟也是成功的。  相似文献   

6.
The Impact Of Air-Flow Separation On The Drag Of The Sea Surface   总被引:2,自引:1,他引:2  
An approach that allows assessment ofthe impact of air-flow separation (AFS) fromwave breaking fronts on the sea-surface drag is presented. Wave breaking fronts are modelled by the discontinuities of the sea-surface slope. It is assumedthat the dynamics of the AFS from wave breaking crests is similar to thatfrom the backward facing step. The form drag supported by an individualbreaker is described by the action of the pressure drop distributed alongthe forward face of the breaking front. The total stress due to the AFS isobtained as a sum of contributions from breaking fronts of different scales.Outside the breaking fronts the drag of the sea surface is supported by theviscous surface stress and the wave-induced stress. To calculate the stressdue to the AFS and the wave-induced stress a physical model of the wind-wavespectrum is used. Together with the model of the air flow described in termsof surface stresses it forms a self-consistent dynamical system for the seasurface-atmosphere where the air flow and wind waves are strongly coupled.Model calculations of the drag coefficient agree with measurements. It is shownthat the dimensionless Charnock parameter (roughness length normalized onthe square of the friction velocity and the acceleration of gravity)increases with the increase of the wind speed in agreement with fieldmeasurements. The stress due to the AFS normalized on the square of thefriction velocity is proportional to the cube of wind speed. At low windsthe viscous surface stress dominates the drag. The role of the form drag,which is the sum of the stress due to the AFS and the wave-induced stress, isnegligible. At moderate and high winds the form drag dominates. At windspeeds higher than 10 m s-1 the stress supported by the AFS becomescomparable to the wave-induced stress and supports up to 50% of the totalstress.  相似文献   

7.
Meridional, linear, and free modes of global, primitive-equation, ocean-atmosphere models were analyzed to see if they contain multi-year, especially decadal ( 10–30 years), oscillation time scale modes. A two-layer model of the global ocean and a two-level model of the global atmosphere were formulated. Both models were linearized around axially-symmetric basic states containing mean meridional circulations. The linearized perturbation system was solved as an eigenvalue problem. The operator matrix was discretized in the north-south direction with centered finite differences. Uncoupled, meridional modes of oscillation of the ocean and the atmosphere models were calculated. Calculations were performed at three grid spacings (5°, 2.5° and 1.25°) and for two types of basic states (symmetric and asymmetric). Uncoupled, free oceanic modes in the presence of mean meridional circulations have oscillation time scales ranging from two years to several centuries. Such low frequency meridional modes do not exist in the ocean model if there are no mean meridional circulations. A large number of oceanic modes are grouped around decadal oscillation time scales. All the oceanic modes have neutral growth rates. The spatial structures of some of the oceanic modes are comparable to observed spatial structures of sea surface temperature variations in the Pacific Ocean. Most years to decades variability of meridional modes of the ocean model is contained in tropical and midlatitude modes. Some oceanic modes with years to decades periods have standing oscillations in the tropics and poleward propagation of zonal velocity and layer thickness outside the tropics. Uncoupled, free atmospheric modes in the presence of mean meridional circulations have oscillation time scales ranging from a week to several decades. Such low-frequency meridional modes do not exist in the atmospere model if there are no mean meridional circulations. A large number of modes are grouped around intraseasonal time scales. Unlike the oceanic modes, the atmospheric modes are weakly unstable. Most of the intraseasonal variability of atmospheric modes is contained in tropical, midlatitude, and polar modes. Atmospheric modes with oscillation periods longer than about one year have global extent. Meridional ocean-atmospheric modes exist in the models wherever there are mean meridional circulations, i.e., tropical, midlatitude, polar, and global. Oceanic and atmospheric eigenvectors have symmetric (assymetric) latitudinal structures if their basic states are symmetric (asymmetric) around the equator. For both models, models calculated at coarser than 2.5° grid spacing do not accurately represent low-frequency variability. Scale analysis shows taht advection by tge basic state meridional velocities is the primary cause of the meridional oscillations on time scales longer than two years in the ocean model and longer than a few weeks in the atmosphere model. Meridional modes of the coupled ocean-atmosphere models are the subject of a subsequent paper.This paper was presented at the International Conference on Modelling of Global Climate Change and Variability, held in Hamburg 11–15 September 1989 under the auspices of the Meteorological Institute of the University of Hamburg and the Max Planck Institute for Meteorology. Guest Editor for these papers is Dr. L. Dümenil  相似文献   

8.
Abstract

The propagation of baroclinic Kelvin and Rossby waves in a fairly coarse‐resolution numerical reduced‐gravity ocean model is investigated using simple geostrophic adjustment experiments in a box‐like domain. Numerical experiments using three different horizontal resolutions (4° × 5°,2° × 2.5° and l° × 1.25°) with properly scaled eddy viscosity coefficients show that the phase speed of the model Kelvin waves is almost exactly proportional to the grid resolution, but is virtually independent of the model viscosity. These results are consistent with the findings of Hsieh et al. (1983) and Wajsowicz and Gill (1986). It is also shown that the two relevant parameters that govern the propagation and decay of these waves, namely the grid‐resolution parameter Δ = Δx/a (where Δx is the grid size and a is the baroclinic Rossby radius, viz. a = C/f, with C being the phase speed of inviscid internal gravity waves in a continuum) and the viscosity parameterΔ = Amλ/2πfa3 (where Am is the eddy viscosity coefficient and λ is the alongshore wavelength) can be replaced with Δ only. This is because in Munk (1950)‐type models, the viscosity parameter Δ scales with Δ3. For Δ3 >1, the Kelvin wave phase speed is cK ΔC/Δ and the alongshore decay length scale is of the order of the perimeter of the basin, viz., 0(104) km.

In contrast to the case for Kelvin waves, the phase speed of the model Rossby waves is not that much different from its value in a continuum and depends only weakly on the model resolution. This is in good agreement with the theoretical results of Wajsowicz (1986). On the other hand, the model Rossby waves are severely damped, within a distance of the order of a wavelength, by the large eddy viscosity of the model. We therefore extrapolate that for a proper simulanon of Kelvin and Rossby waves in this type of numerical ocean model, we need a grid size smaller than 1° × 1°, and a higher‐order turbulent closure scheme that will reduce the eddy viscosity coefficient.  相似文献   

9.
Changes in the normal mode energetics of the general atmospheric circulation are assessed for the northern winter season (DJF) in a warmer climate, using the outputs of four climate models from the Coupled Model Intercomparison Project, Phase 3. The energetics changes are characterized by significant increases in both the zonal mean and eddy components for the barotropic and the deeper baroclinic modes, whereas for the shallower baroclinic modes both the zonal mean and eddy components decrease. Significant increases are predominant in the large-scale eddies, both barotropic and baroclinic, while the opposite is found in eddies of smaller scales. While the generation rate of zonal mean available potential energy has globally increased in the barotropic component, leading to an overall strengthening in the barotropic energetics terms, it has decreased in the baroclinic component, leading to a general weakening in the baroclinic energetics counterpart. These global changes, which indicate a strengthening of the energetics in the upper troposphere and lower stratosphere (UTLS), sustained by enhanced baroclinic eddies of large horizontal scales, and a weakening below, mostly driven by weaker baroclinic eddies of intermediate to small scales, appear together with an increased transfer rate of kinetic energy from the eddies to the zonal mean flow and a significant increase in the barotropic zonal mean kinetic energy. The conversion rates between available potential energy and kinetic energy, C, were further decomposed into the contributions by the rotational (Rossby) and divergent (gravity) components of the circulation field. The eddy component of C is due to the conversion of potential energy of the rotational adjusted mass field into kinetic energy by the work realized in the eddy divergent motion. The zonal mean component of C is accomplished by two terms which nearly cancel each other out. One is related to the Hadley cell and involves the divergent component of both wind and geopotential, while the other is associated to the Ferrel cell and incorporates the divergent wind with the rotationally adjusted mass field. Global magnitude increases were found in the zonal mean components of these two terms for the warmer climate, which could be the result of a strengthening and/or widening of both meridional cells. On the other hand, the results suggest a strengthening of these conversion rates in the UTLS and a weakening below, that is consistent with the rising of the tropopause in response to global warming.  相似文献   

10.
We investigated the dynamics of upwelling fronts near a coast. This work was first motivated by laboratory experiments [Bouruet-Aubertot, Linden, Dyn. Atmos. Oceans, 2002] in which the front is produced by the adjustment of a buoyant fluid initially confined within a bottomless cylinder. It was shown that cyclonic eddies consisting of coastal waters are enhanced when the front is unstable near the coast (the outer vertical boundary). The purpose of this paper is to provide further insights into this process. We reproduced the experimental configuration using a three-dimensional model of the primitive equations. We first show that for coastal fronts more potential energy, in terms of the maximum available potential energy, is released than for open-ocean fronts. Therefore, waves of larger amplitude are generated during the adjustment and the mean flow that establishes has a higher kinetic energy in the former case. Then as baroclinic instability starts and wave crests reach the boundary, cyclonic eddies are enhanced as in the laboratory experiments and in a similar way. However, in contrast to the laboratory experiments, offshore advection of cyclonic eddies can occur in two stages, depending on the spatial organization of the baroclinic wave. When the baroclinic wave consists of the sum of different modes and is thus highly asymmetric, the offshore advection of cyclonic eddies occurs just after their enhancement at the boundary, as in the laboratory experiments. By contrast, when a single-mode baroclinic wave develops, neighboring cyclonic eddies first merge before being advected offshore. Very different behavior is observed for open-ocean fronts. First a mixed baroclinic–barotropic instability grows. Then the eddies transfer their energy to the mean flow and the barotropic and baroclinic instabilities start again. An excellent agreement is obtained with the main result obtained in the laboratory experiments: the ratio between growth rates of surface cyclonic and anticyclonic vorticity increases as the instability develops nearer to the coast.  相似文献   

11.
Parametrisations of meridional energy and moisture transport used in zonally averaged climate models are validated using reanalysis data and results from a doubling CO2-experiment from a general circulation model. Global meridional fluxes of moisture and sensible heat are calculated by integrating surface and top-of-the-atmosphere vertical fluxes from one pole to the other. The parametrisations include an eddy-diffusion term, representing down-gradient transport of specific humidity and temperature due to the transient atmospheric eddies at mid- and high latitudes, and simple representations of the mean meridional circulation. Qualitative and quantitative agreement between the increased hydrological cycle in the 2×CO2-run from the GCM and the parametrisation is found. The performance for the sensible heat flux shows larger differences to the GCM results, particularly at low latitudes. Seasonal variations of the moisture and sensible heat transport are well captured by parametrisations including the influence of the mean meridional circulation. Interannual variability cannot be simulated. An examination of the parametrisations on different spatial scales suggests that they should not be used for small scales. Furthermore, two closures for the zonal distribution of precipitation were examined. They are used in zonally averaged atmosphere models coupled to an ocean model with different ocean basins at one latitudinal belt. An assessment of both the reanalysis data and the GCM results shows that both closures exhibit very similar behaviour and are valid in the long-term mean and seasonal cycle. Interannual variability is not captured well. They become invalid for spatial scales smaller than 10. Received: 30 November 1998 / Accepted: 4 July 1999  相似文献   

12.
There are very strong thermal gradients between the Antarctic continent and the sea-ice zone, and between that zone and the ocean to the north. As a result of these contrasts the sea-ice domain is one of strong cyclogenesis and high cyclone frequency. In this study we explore many aspects of that cyclonic behaviour and investigate the manner in which these systems influence, and are influenced by, the sea ice. Using the NCEP-DOE re-analyses (1979–2002) we have determined variables that are proportional to the mean of the wind stress and the mean rate at which mechanical energy is imparted to the surface. Using two decompositions of the wind field we have obtained estimates of how much of these fluxes are contributed to by the transient eddies. We find these to be significant over the sea ice and the ocean to the north, particularly when a new decomposition is used. The presence of frequent and vigorous cyclones is a central factor that determines the positive mean freshwater flux over the sea-ice zone in all seasons. This transfer to the ocean is smallest in summer (0.49 mm day−1) and assumes a maximum of 1.27 mm day−1 in winter.  相似文献   

13.
通过1982年梅雨期的个例分析,研究和比较了中国和日本梅雨我的结构。分析表明:1.梅雨锋区系统对流层上部宽广的斜压区和对流层低层较狭窄的弱斜压区共同组成;2.在两个个例中,中国剖面上锋区均呈“椅”型结构。日本剖面上,6月呈均匀倾斜结构,7月略呈“椅型”,涡度场上中国剖面为相当正压结构,日本剖面为斜压结构;3.梅雨锋区系统可民是均匀斜压区在不均匀和加热情况下结构改变结果;4.中国大陆雨区高层大量潜热  相似文献   

14.
With the purpose of studying the upper part of the ocean, the shallow water equations (in a `reduced gravity' setting) have been extended in the last decades by allowing for horizontal and temporal variations of the buoyancy field ϑ, while keeping it as well as the velocity field u as depth-independent. In spite of the widespread use of this `slab' model, there has been neither a discussion on the range of validity of the system nor an explanation of points such as the existence of peculiar zero-frequency normal modes, the nature of the instability of a uniform u flow, and the lack of explicit vertical shear associated with horizontal density gradients. These questions are addressed here through the development of a subinertial model with more vertical resolution, i.e., one where the buoyancy ϑ varies linearly with depth. This model describes satisfactorily the problem of baroclinic instability with a free boundary, even for short perturbations and large interface slopes. An enhancement of the instability is found when the planetary β effect is compensated with the topographic one, due to the slope of the free boundary, allowing for a `resonance' of the equivalent barotropic and first baroclinic modes. Other low-frequency models, for which buoyancy stratification does not play a dynamical role, are invalid for short perturbations and have spurious terms in their energy-like integral of motion.  相似文献   

15.
We consider subinertial, free waves trapped along three coastlines (i.e., shelf waves) in an ocean governed by a geophysical model in which stratification is explicitly obtained by taking the Vaisala frequency N much greater than the inertial frequency f. The behavior is generalized in terms of the parameter S = (N/f)a where a is the bottom slope of the trapping region. Only when S $?0.2, are the predicted shelf waves like those predicted by Laplace's tidal equations (LTE) on an f-plane. When 0.2 ? S < 1, LTE are inappropriate because the shelf waves are only qualitatively like those predicted by LTE, and when S 1, the shelf waves are like baroclinic Kelvin waves in that they can occur at any subinertial frequency up to f (in qualitative disagreement with the predictions of LTE). Since N/f is usually a large number in the real ocean (of order 50–250), S is likely to be large unless the bottom slope is very gentle throughout the trapping region. Some applications to coastal current observations are discussed.  相似文献   

16.
The dynamics of a low-order coupled wind-driven ocean–atmosphere system is investigated with emphasis on its predictability properties. The low-order coupled deterministic system is composed of a baroclinic atmosphere for which 12 dominant dynamical modes are only retained (Charney and Straus in J Atmos Sci 37:1157–1176, 1980) and a wind-driven, quasi-geostrophic and reduced-gravity shallow ocean whose field is truncated to four dominant modes able to reproduce the large scale oceanic gyres (Pierini in J Phys Oceanogr 41:1585–1604, 2011). The two models are coupled through mechanical forcings only. The analysis of its dynamics reveals first that under aperiodic atmospheric forcings only dominant single gyres (clockwise or counterclockwise) appear, while for periodic atmospheric solutions the double gyres emerge. In the present model domain setting context, this feature is related to the level of truncation of the atmospheric fields, as indicated by a preliminary analysis of the impact of higher wavenumber (“synoptic” scale) modes on the development of oceanic gyres. In the latter case, double gyres appear in the presence of a chaotic atmosphere. Second the dynamical quantities characterizing the short-term predictability (Lyapunov exponents, Lyapunov dimension, Kolmogorov–Sinaï (KS) entropy) displays a complex dependence as a function of the key parameters of the system, namely the coupling strength and the external thermal forcing. In particular, the KS-entropy is increasing as a function of the coupling in most of the experiments, implying an increase of the rate of loss of information about the localization of the system on its attractor. Finally the dynamics of the error is explored and indicates, in particular, a rich variety of short term behaviors of the error in the atmosphere depending on the (relative) amplitude of the initial error affecting the ocean, from polynomial (at 2 + bt 3 + ct 4) up to exponential-like evolutions. These features are explained and analyzed in the light of the recent findings on error growth (Nicolis et al. in J Atmos Sci 66:766–778, 2009).  相似文献   

17.
In 2004–2007 and 2011–2013, oceanography sections with the high spatial resolution were carried out on the shelf and continental slope of the Commonwealth Sea and in the Prydz Bay in the Antarctic. In combination with a fine vertical resolution, this provides an advanced interpretation of the obtained data. It becomes possible to analyze the local thermohaline structure of the baroclinic Antarctic slope front (the ASF) and to investigate its stability. The reliable determination of the ASF characteristics enables to apply the parameterizations and criteria obtained during laboratory experiments for analysis of its stability. The ASF instability is preceded by the local vertical dramatic intensification of the front, where the ASF approaches the pure baroclinic state. Therefore, the local baroclinic instability in the ASF area prevails over the barotropic one at the significant mutual impact of layers (δ = H ASF/H b ≈ ≈ 0.3–0.6, H b is the total depth) and accompanied with the hydrostatic instability. Instability conditions in the frontal zone with a width of ~(1–2)Rd L (Rd L is local baroclinic deformation radius) relative to the wide ASF (L ASF ≈ (3–5)Rd L ) coincide with those of the narrow (intensified) ASF (L ASFRd L* ). In the case of the runoff of dense Antarctic shelf water, on the shelf edge the realization is possible of the self-oscillatory mechanism of the ASF instability caused by the topographic beta-effect as well as the periodic generation of baroclinic vortices.  相似文献   

18.
We analyse the dependence of the cloud radiative effect (CRE) and cloud amount on mid-tropospheric pressure velocity (ω 500) and sea surface temperature (SST) and point out the shortcomings of using these two proxies separately as means to separate cloud regimes. A bivariate approach is proposed to overcome these shortcomings and it is used to systematically investigate marine cloud properties at different spatial and time scales in the present-day (1985–2001) tropical climate. During the 1997–1998 El Niño, the greatest regional change in CRE and cloud cover coincides with the greatest local change in circulation and SST. In addition, we find that the cooling effect of the stratiform low clouds reduces at the rate of approximately 1 W/m2 per percent of cloudiness reduction in the subsident cold pools of the Pacific ocean. During El Niño, the transition between different cloud regimes gives rise to opposing cloud feedbacks. The sign of the total feedback is controlled by the cloud optical thickness. More generally, we find that the largest part of the cloud response to El Niño, when averaged over the tropical Pacific, is not directly associated with ω 500 and SST changes, so other factors must play a role as well.  相似文献   

19.
吕克利  徐亚梅 《气象学报》1995,53(3):328-336
利用三维半地转模式讨论了春夏秋冬四季基本气流上非线性斜压扰动的发展过程和锋面形成过程。计算结果表明,在四季基本气流上,斜压扰动的发展能产生冷暖锋,扰动的发展以冬季为最强,春季次之,秋季和夏季最弱,相应地,形成的锋也以冬季最强,春季次之,秋夏季最弱,与实际观测比较一致。  相似文献   

20.
Various types of satellite (AIRS/AMSU, MODIS) and ground measurements are used to analyze temperature trends in the four vertical layers (skin/surface, mid-troposphere, and low stratosphere) around the Korean Peninsula (123–132°E, 33–44°N) during the period from September 2002 to August 2010. The ground-based observations include 72 Surface Meteorological Stations (SMSs), 6 radiosonde stations (RAOBs), 457 Automatic Weather Stations (AWSs) over the land, and 5 buoy stations over the ocean. A strong warming (0.052 K yr?1) at the surface, and a weak warming (0.004~0.010 K yr?1) in the mid-troposphere and low stratosphere have been found from satellite data, leading to an unstable atmospheric layer. The AIRS/AMSU warming trend over the ocean surface around the Korean Peninsula is about 2.5 times greater than that over the land surface. The ground measurements from both SMS and AWS over the land surface of South Korea also show a warming of 0.043~0.082 K yr?1, consistent with the satellite observations. The correlation average (r = 0.80) between MODIS skin temperature and ground measurement is significant. The correlations between AMSU and RAOB are very high (0.91~0.95) in the anomaly time series, calculated from the spatial averages of monthly mean temperature values. However, the warming found in the AMSU data is stronger than that from the RAOB at the surface. The opposite feature is present above the mid-troposphere, indicating that there is a systematic difference. Warming phenomena (0.012~0.078 K yr?1) are observed from all three data sets (SMS, AWS, MODIS), which have been corroborated by the coincident measurements at five ground stations. However, it should also be noted that the observed trends are subject to large uncertainty as the corresponding 95% confidence intervals tend to be larger than the observed signals due to large thermal variability and the relatively short periods of the satellitebased temperature records. The EOF analysis of monthly mean temperature anomalies indicates that the tropospheric temperature variability near Korea is primarily linked to the Arctic Oscillation (AO), and secondarily to ENSO (El Niño and Southern Oscillation). However, the low stratospheric temperature variability is mainly associated with Southern Oscillation and then additionally with Quasi-Biennial Oscillation (QBO). Uncertainties from the different spatial resolutions between satellite data are discussed in the trends.  相似文献   

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