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1.
A diagnostic study of heat transfer within the lower atmosphere and between the atmosphere and the surface of the Arctic Ocean
snow/ice pack during clear-sky conditions is conducted using data from the Surface Heat Budget of the Arctic Ocean (SHEBA)
field experiment. Surface heat budgets computed for four cloudy and four clear periods show that, while the net turbulent
heat fluxes at the surface are small during the cloudy periods, during the clear-sky periods they are a considerable source
of surface heating, balancing significant portions of the conductive heat fluxes from within the snow/ice pack. Analysis of
the dynamics and thermodynamics of the lower atmosphere during the clear-sky periods reveals that a considerable portion of
the heat lost to the surface by turbulent heat fluxes is balanced by locally strong heating near the atmospheric boundary-layer
(ABL) top due to the interaction of subsiding motions with the strong overlying temperature inversions surmounting the ABL.
This heat is then entrained into the ABL and transported to the surface by turbulent mixing, maintained by a combination of
vertical wind shear and wave-turbulence interactions. The frequency of stable, clear-sky periods, particularly during the
winter, combined with these results, suggests that the downward transfer of heat through the lower atmosphere and into the
surface represents an important component of the heat budgets of the lower atmosphere and snow/ice pack over the annual cycle 相似文献
2.
Virginie Guemas Francisco J. Doblas-Reyes Kristian Mogensen Sarah Keeley Yongming Tang 《Climate Dynamics》2014,43(9-10):2813-2829
Polar climate studies are severely hampered by the sparseness of the sea ice observations. We aim at filling this critical gap by producing two 5-member sea ice historical simulations strongly constrained by ocean and atmosphere observational data and covering the 1958–2006 and 1979–2012 periods. This is the first multi-member sea ice reconstruction covering more than 50 years. The obtained sea ice conditions are in reasonable agreement with the few available observations. These best estimates of sea ice conditions serve subsequently as initial sea ice conditions for a set of 28 3-year-long retrospective climate predictions. We compare it to a set in which the sea ice initial conditions are taken from a single-member sea ice historical simulation constrained by atmosphere observations only. We find an improved skill in predicting the Arctic sea ice area and Arctic near surface temperature but a slightly degraded skill in predicting the Antarctic sea ice area. We also obtain a larger spread between the members for the sea ice variables, thus more representative of the forecast error. 相似文献
3.
Connection between atmospheric latent energy and energy fluxes simulated by nine CMIP5 models 
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下载免费PDF全文 The atmospheric latent energy and incoming energy fluxes of the atmosphere are analyzed here based on the historical simulations of nine coupled models from the Coupled Model Intercomparison Project Phase 5(CMIP5)and two reanalysis datasets.The globally averaged atmospheric latent energy is found to be highly correlated with several types of energy flux,particularly the surface latent heat flux,atmosphere absorbed solar radiation flux,and surface net radiation flux.On the basis of these connections,a hydrological cycle controlled feedback(HCCF)is hypothesized.Through this feedback,the atmosphere absorbed solar radiation is enhanced and causes intensification of the surface latent heat flux when the atmospheric latent energy is abnormally strong.The representativeness of the HCCF during different periods and over different latitudinal zones is also discussed.Although such a feedback cannot be confirmed by reanalysis,it proves to be a common mechanism for all the models studied. 相似文献
4.
R. J. DELMAS P. WAGNON K. GOTO-AZUMA K. KAMIYAMA O. WATANABE 《Tellus. Series B, Chemical and physical meteorology》2003,55(1):71-79
We have examined several MSA (methanesulfonic acid) records from the upper 200 m of the Antarctic ice sheet and in particular the new Dome F profile. At all the four sites studied, concentration profiles exhibit similar patterns as a function of depth. They suggest that snow metamorphism and solid phase migration are responsible for a marked release of gaseous MSA to interstitial firn air as well as probably to the free atmosphere, in particular at extremely low accumulation sites. Snow acidity can also modify MSA concentration. It is proposed that, below the upper few metres where the communication with the free atmosphere is possible, gaseous MSA may remain in the firn layers and be entrapped later in air bubbles at pore close-off, i.e. when firn is transformed into ice. Chemical measurements on the firn core do not take into account the MSA released to the gaseous phase, but this fraction is measurable in ice samples. In spite of these alterations occurring in the firn layers, relative changes of the atmospheric MSA concentration in the past are probably still there deep within the Antarctic ice sheet. However, for glacial periods, different processes have to be considered in relation to modified aerosol properties. 相似文献
5.
本文是关于云和云天大气对太阳辐射吸收异常问题的一个综述，总结了到目前为止的对水云异常吸收的一些解释，指出这些解释的合理性和缺陷。本文的重点在于介绍近年来论争激烈的有云大气的异常吸收问题，对存在和不存在增强吸收的两种截然相反的观点都做了较详细的评述。 相似文献
6.
利用WRF模式模拟了2011年6月16-17日四川盆地的一次大暴雨过程,首先根据24 h累积降水的位置、强度,选取了位于不同地形的3个强降水中心作为代表站,分析其降水日变化的模拟效果。结果表明:模式基本模拟出了位于川东北盆地边缘旺苍地区的降水峰值;而对位于盆中的荣昌站和位于川西高原的越西地区的模拟效果不理想。为了揭示影响逐时降水的因子,对3个代表站不同时刻的模拟效果进行对比分析,发现强降水的模拟效应与对流层中水汽、动力以及热力条件的模拟效果紧密相关。模式对水汽、位势高度、流场、垂直速度及大气层结状况这些物理量在各个时刻的不同模拟效果导致了逐时降水模拟的偏差,模式中盆地周围山地地形高度的偏差同样影响降水的模拟效果。 相似文献
7.
地气耦合系统中温湿变化的数值模拟 总被引：4，自引：1，他引：4
本文提出了计算地气耦合系统中温度和湿度变化的一维数值模式,在土壤中,利用热量平衡和水份平衡原理计算土壤温度和湿度,在大气中,考虑了长短波辐射、云量和凝结等因素对大气温湿变化的影响。选择一种代表性土壤对模式进行了检验,结果发现,模式能较好地模拟诸多物理量的日变化过程。计算表明,大气和土壤的初始温湿分布,对结果有较大影响。本文的原理可应用于大气环流模式中陆气相互作用过程的参数化。 相似文献
8.
降水强迫对戈壁局地气候系统水、热输送的影响 总被引：16，自引：1，他引：16
用黑河实验中化音站（戈壁）加强期的湍流脉动场资料对降水强迫影响戈壁局地气候系统水、热输送的过程进行了系统分析。结果表明：降水强迫会使戈壁局地气候系统出现暂时的不平衡状态，要重新回到平衡状态需要通过物质和能量的重新调配来实现。该过程可划分为４个阶段，各个阶段间的感热、潜热和水汽通量均有较大差异。从近地层水、热输送特征看，受降水强迫后非平衡状态的张弛时段大约为４ｄ。在整个张弛期间，地表接收到的降水约有２／３通过地表蒸发后输送到大气，其余部分可能被渗入地下 相似文献
9.
A model for studying the heat and mass exchange between the atmosphere and a water body is developed, in which the phase change process of water freezing in winter and melting in summer and the function of the convective mixing process are taken into consideration. The model uses enthalpy rather than temperature as the predictive variable. It helps to set up governing equations more concisely, to deal with the phase change process more easily, and make the numerical scheme simpler. The model is verified by observed data from Lake Kinneret for a non-frozen lake in summer time, and Lake Lower Two Medicine for a frozen lake in winter time. Reasonably good agreements between the model simulations and observed data indicate that the model can serve as a component for a water body in a land surface model. In order to more efficiently apply the scheme in a climate system model, a sensitivity study of various division schemes with less layers in the vertical direction in the water body is conducted. The results of the study show that the division with around 10 vertical layers could produce a prediction accuracy that is comparable to the fine division with around 40 layers. 相似文献
10.
11.
暖切变型江淮梅雨锋结构及其形成和维持机制 总被引：26，自引：6，他引：20
对在1991年7月上旬特别稳定的梅雨形势下持续10天的特大暴雨期作了合成和典型过程研究,并进一步探讨了暖切变型江淮梅雨锋天气系统模型。它在自由大气层表现为结构竖立的相当正压切变线和一种不同于经典地转动量近似的带状准二维运动场。边界层的浅层锋生倾斜环流以及偏于切变线轴以南的Ekman抽吸与自由大气层中基本上由积云对流加热驱动的竖直环流相互依存和耦合,造成持续的大暴雨。这种系统的初生和中断后复苏的机制可能是由斜压性极弱的副热带高空东移的短波扰动在低层“湿度锋”带紧南侧触发导致的一种带状CISK。 相似文献
12.
Soil is heterogeneous and has different thermal and hydraulic properties, causing varied behavior in heat and moisture transport. Therefore, soil has an important effect on land–atmosphere interactions. In this study, an improved soil parameterization scheme that considers gravel and organic matter in the soil was introduced into CLM4.5 (Community Land Model). By using data from the Zoige and Madoi sites on the Tibetan Plateau, the ability of the model to simultaneously simulate the duration of freeze–thaw periods, soil temperature, soil moisture, and surface energy during freeze–thaw processes, was validated. The results indicated that: (1) the new parameterization performed better in simulating the duration of the frozen, thawing, unfrozen, and freezing periods; (2) with the new scheme, the soil thermal conductivity values were decreased; (3) the new parameterization improved soil temperature simulation and effectively decreased cold biases; (4) the new parameterization scheme effectively decreased the dry biases of soil liquid water content during the freezing, completely frozen, and thawing periods, but increased the wet biases during the completely thawed period; and (5) the net radiation, latent heat flux, and soil surface heat flux of the Zoige and Madoi sites were much improved by the new organic matter and thermal conductivity parameterization. 相似文献
13.
Leads and polynyas have a great impact on the energy budget of the polar ocean and atmosphere. Since atmospheric general
circulation models are not able to resolve the spatial scales of these inhomogeneities, it is necessary to include the effect
of fractional sub-grid scale sea-ice inhomogeneities on climate by a suitable parametrization. In order to do this we have
divided each model grid-cell into an ice-covered and an ice-free part. Nevertheless, a numerical model requires effective
transports representative for the whole grid-box. A simple procedure would be to use grid averages of the surface parameters
for the calculation of the surface fluxes. However, as the surface fluxes are non-linearly dependent on the surface properties,
the fluxes over ice and open water should be calculated separately according to the individual surface-layer structure of
each surface type. Then these local fluxes should be averaged to obtain representative fluxes. Sensitivity experiments with
the Hamburg atmospheric general circulation model ECHAM3 clearly show that a subgrid scale distribution of sea ice is a dominant
factor controlling the exchange processes between ocean and atmosphere in the Arctic. The heat and water vapour transports
are strongly enhanced leading to a significant warming and moistening of the polar troposphere. This affects the atmospheric
circulation in high- and mid-latitudes; e.g. the stationary lows are modified and the transient cyclonic activity over the
subpolar oceans is reduced. A pronounced impact of sub-grid scale sea-ice distribution on the model climate can only be obtained
when the non-linear behaviour of the surface exchange processes is considered by a proper, physically based, averaging of
the surface fluxes. A simple linear averaging of surface parameters is not sufficient.
Received: 13 September 1994 / Accepted: 25 July 1995 相似文献
14.
A primitive equation model is used to investigate the warm pool equilibrium of the tropical Pacific ocean. Attention is focused
on the upper ocean. The oceanic response is described using an isothermal approach applied to warm waters contained in the
TOGA-COARE domain. The heat balance shows that all the terms, atmospheric surface fluxes, advection and diffusion, operate
in the heat bugdet with different time scales. Over long periods, diffusive heat fluxes transfer heat received from the atmosphere
out of the warm pool trough the top of the main thermocline. Over short periods, the impact of westerly wind bursts modifies
this balance: atmospheric heating is reversed, diffusion is enhanced and advective heat transports out of the warm pool operate
through zonal and vertical contributions. We were able to relate the two latter processes to zonal jets and Ekman pumping,
respectively. Conversely, the meridional contribution always represents a source of heat, mainly due to the tropical wind
convergence. The modelling results clearly show that except during strong wind events, entrainment cooling is not an important
component of the budget. The inability to remove heat is due to the salt stratification which needs to be first reduced or
even destroyed by westerly wind bursts to activate heat entrainment into deeper layers. Finally, we suggest that the near
zero estimate for the surface heat flux entering the warm pool may be extended to longer periods including seaosnal to interannual
time scale.
Received: 16 December 1996 / Accepted: 8 July 1997 相似文献
15.
1960—2010年中国南方地区夏季旱涝时空分布特征 总被引：1，自引：0，他引：1
基于1960—2010年中国南方地区51 a降水资料,进行Z指数变换,再利用降水距平场作REOF分区,并分别对各区域代表站点Z指数序列作线性趋势分析和M-K分析及Morlet小波分析。结果表明：中国南方5个分区岳阳站、广州站、丽水站、信阳站和巢湖站5个典型站点的年际及年代际波动幅度都比较明显,但均呈由干变湿的趋势。且5个站点分别在1973、1993、1992、2002年和1979年发生突变,突变后UF一直呈上升趋势,总体均由干变湿5,个分区旱涝异常具有相对一致的性质。中国南方地区夏季降水具有多时间尺度振荡的特点,存在2—3 a和5—6 a的周期。 相似文献
16.
西北地区东部旱涝气候特征 总被引：1，自引：1，他引：1
利用中国气象科学研究院收集、整理的西北地区东部代表站1470~2003年的旱涝等级资料,根据不同的地形地貌特征和气候特征,将西北地区东部分为3个气候区,利用周期分析、coif3小波变换等统计分析方法对3个气候区534年旱涝指数的年代际气候特征及地域之间旱涝变化的差异进行分析。结果表明,西北地区东部不同区域旱涝的时空分布特征不尽相同,旱涝演变趋势、旱涝周期变化既有一致性,也存在明显的差异。534年以来北部、中部由偏旱趋于正常或偏涝,南部1724年以前的变化趋势由偏旱趋于偏涝,1724年以后由偏涝趋于偏旱;3个气候区都存在25年和10年的显著周期,其中中部还存在14~15年的显著周期,说明中部旱涝交替较北部和南部明显。 相似文献
17.
The aerosol optical depth of the atmosphere obtained from spectral sun photometer measurements and the integral optical depth determined from standard actinometric observations of direct solar radiation are the parameters of the optical state of the atmosphere. The quantitative estimates of the integral transparency and aerosol optical depth of the atmosphere in Antarctica are presented, their long-term variability over the entire period of observations is analyzed. The comparison of obtained data with the estimates for other natural regions and conditions revealed that during the periods without the impact of volcanic eruptions, the levels of atmospheric aerosol turbidity in Antarctica over the recent decades are minimal on the planet and can be considered as global background characteristics. 相似文献
18.
耦合时间步长对ENSO循环周期模拟的影响 总被引：2，自引：0，他引：2
利用严邦良等所构造的热带海 气耦合模式来研究耦合时间步长对海 气耦合模式模拟ENSO循环的影响 ,结果表明 :由于耦合时间步长不同 ,海 气耦合模式模拟的不规则周期的ENSO循环可以变为有规则周期的ENSO循环或者反过来。同时 ,耦合时间步长还可以对耦合系统中大气及海洋变量的增长率及传播方向产生影响。 相似文献
19.
大气气溶胶的垂直非均一对向上亮度和卫星遥感地表反射率的效应 总被引：1，自引：0，他引：1
均一模式和两层模式是两个忽略气溶胶垂直非均一、并广泛用于卫星遥感的辐射模式。通过两个模式的数值模拟，分析了气溶胶的垂直非均一对向上天空亮度和卫星遥感地面反射率的效应。数值模拟选用了２４个有代表性的气溶胶模式。对于具有强分子散射的卫星短波通道，由于分子和气溶胶散射性的明显不同，应用均一和两层模式计算的向上亮度往往存在较大误差。对长波通道，如果气溶胶的光学特性随高度变化不大，该亮度误差较小，但如果存在不同散射相函数和一次散射反照率的气溶胶层，该误差仍可能较大。对于干净的大气，由均一和两层模式计算的亮度误差可分别高达３１．４％和３１．５％，而对于混浊的大气，该误差可分别高达６７．８％和５９．２％。该亮度误差可以引起地表反射率解存在大的不确定性，特别是对于短波通道和强吸收的气溶胶。对于包含强吸收气溶胶的混浊大气，均一和两层模式不适合于大气订正应用。 相似文献
20.
Tropospheric transport of continental tracers towards Antarctica under varying climatic conditions 总被引：1，自引：0，他引：1
We present a method to analyse tracer transit time climatologies based on the concept of tracer age. The method consists of introducing idealized, short-lived radioactively decaying tracers in a general circulation model of the atmosphere. Tracer age since emission is calculated at any given place in the atmosphere from the ratio of the concentrations of tracers with different lifetimes emitted over the same source area. An obvious use of this method is the analysis of transport of real tracers with similar lifetimes (such as dust particles) during different climatic periods. Here, this method is applied to transport from southern hemisphere continental source areas towards Antarctica at the present, the last glacial maximum (21 kyr BP) and the last glacial inception (115 kyr BP). It is found that the variation over time of atmospheric transport efficiency towards Antarctica depends on the tracer source region: changes for Patagonian tracers differ from those for tracers originating over Australia and southern Africa. Transport towards Antarctica during the last glacial maximum (LGM) is faster for Patagonian, but not for Australian and Southern African tracers. It is shown that for the time of the last glacial inception, tracer transit time towards Antarctica is not significantly different from the present, although signs of a more vigorous atmospheric circulation can be seen in the simulation. 相似文献