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The objective of the present work is to develop a general purpose, polarized, microwave radiative transfer forward model, including calculation of interaction parameters for fast, simultaneous and accurate generation of radiances, for use in a wide variety of atmospheric retrieval applications. This complete polarized model includes the generation of atmospheric profiles, calculation of the interaction parameters and the solution of the vector radiative transfer equations. In the present work, the doubling and adding method is used to calculate radiances. Mie theory is used for spherical particles to evaluate the polarized scattering matrix. Two types of sea surface models applicable for specular and diffuse surfaces respectively are implemented. The model has been validated against standard benchmark cases and experimental data available in literature. While the model is itself generic, parametric studies are performed to study the influence of the vertical structure of the atmosphere, for two polarizations and a set of frequencies to be used on the microwave imager aboard the proposed Indo-French climate research satellite MEGHA-TROPIQUES. 相似文献
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Presented is a review of the radiative properties of ice clouds from three perspectives: light scattering simulations, remote sensing applications, and broadband radiation parameterizations appropriate for numerical models. On the subject of light scattering simulations, several classical computational approaches are reviewed, including the conventional geometric-optics method and its improved forms, the finite-difference time domain technique, the pseudo-spectral time domain technique, the discrete dipole approximation method, and the T-matrix method, with specific applications to the computation of the singlescattering properties of individual ice crystals. The strengths and weaknesses associated with each approach are discussed.With reference to remote sensing, operational retrieval algorithms are reviewed for retrieving cloud optical depth and effective particle size based on solar or thermal infrared(IR) bands. To illustrate the performance of the current solar- and IR-based retrievals, two case studies are presented based on spaceborne observations. The need for a more realistic ice cloud optical model to obtain spectrally consistent retrievals is demonstrated. Furthermore, to complement ice cloud property studies based on passive radiometric measurements, the advantage of incorporating lidar and/or polarimetric measurements is discussed.The performance of ice cloud models based on the use of different ice habits to represent ice particles is illustrated by comparing model results with satellite observations. A summary is provided of a number of parameterization schemes for ice cloud radiative properties that were developed for application to broadband radiative transfer submodels within general circulation models(GCMs). The availability of the single-scattering properties of complex ice habits has led to more accurate radiation parameterizations. In conclusion, the importance of using nonspherical ice particle models in GCM simulations for climate studies is proven. 相似文献
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A rainfall that occurred during 0200–1400 Beijing Standard Time(BST)25 August 2008 shows the rapid development of a convective system,a short life span,and a record rate of 117.5 mm h-1for Xujiahui station since 1872.To study this torrential rainfall process,the partitioning method of Q vector is developed,in which a moist Q vector is first separated into a dry ageostrophic Q vector(DQ)and a diabatic-heating component.The dry ageostrophic Q vector is further partitioned along isothermal lines in the natural... 相似文献
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The effect of a vertical diffusion scheme over a stratocumulus topped boundary layer (STBL) was investigated using the YONU AGCM (Yonsei University Atmospheric General Circulation Model). To consider the impact of clouds on the turbulence production, the turbulence mixing term, driven by radiative cooling at the cloud top, is implemented as an extended non-local diffiusion scheme. In the model with this new scheme, the STBL parameterization significantly influences the lower atmosphere over the tropical and... 相似文献
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黑碳气溶胶辐射强迫全球分布的模拟研究 总被引：15，自引：3，他引：15
利用一个改进的辐射传输模式,结合全球气溶胶数据集（GADS）,计算晴空条件下冬夏两季黑碳气溶胶的直接辐射强迫在对流层顶和地面的全球分布。计算结果表明,与温室气体引起的整层大气都是正的辐射强迫不同,黑碳气溶胶的辐射强迫在对流层顶为正值,而在地面的辐射强迫却是负值。作者从理论上解释了造成这种结果的原因。对北半球冬季和夏季而言,在对流层顶黑碳气溶胶的全球辐射强迫的平均值分别为0.085W/m2和0.155 W/m2,在地面则分别为-0.37 W/m2和-0.63 W/m2。虽然气溶胶的辐射强迫主要依赖于其本身的光学性质和在大气中的浓度,太阳高度角和地表反照率对黑碳气溶胶的辐射强迫会产生很大的影响。研究指出:黑碳气溶胶在对流层顶正的辐射强迫和在地面负的辐射强迫的绝对值都随太阳天顶角的余弦和地表反照率的增加线性增大;地表反照率对黑碳气溶胶辐射强迫的强度和分布都有重要影响。黑碳气溶胶的辐射强迫分布具有明显的纬度变化特征,冬夏两季的大值区都位于30°N~90°N之间,表明人类活动是造成黑碳气溶胶辐射强迫的主要原因。 相似文献
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气溶胶光散射信息是辐射传输模拟、气候学研究及大气海洋遥感等的重要前提,由于其基础性地位,气溶胶光散射数值模拟一直是大气科学领域的研究热点。本文简明扼要地对气溶胶光散射数值模拟技术的研究现状进行了综述,主要内容包括以下3个方面:(1)总结和分析了Mie散射理论在实际应用的局限性;(2)对气溶胶光散射理论进行了归类,概述了其发展历程、研究现状,重点分析了不同散射理论的基本原理、适用范围、算法复杂度及相应的优缺点;(3)总结了气溶胶光散射研究中存在的问题,扼要地概括了气溶胶光散射数值模拟的研究热点及发展方向。 相似文献
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The Net Exchange Formulation (NEF) is an alternative to the usual radiative transfer equation. It was proposed in 1967 by Green [Q. J. R. Meteorol. Soc. 93 (1967) 371] for atmospheric sciences and by Hottel [H.C. Hottel, A.F. Sarofim. Radiative Transfer McGraw Hill, New York, 1967] for engineering sciences. Until now, the NEF has been used only in a very few cases for atmospheric studies. Recently we have developed a long-wave radiative code based on this formulation for a GCM of the Mars planet. Here, we will present results for the Earth atmosphere, obtained with a Monte Carlo Method based on the NEF. In this method, fluxes are not addressed any more. The basic variables are the net exchange rates (NER) between each pair of atmospheric layer (i, j), i.e. the radiative power emitted by i and absorbed by j minus the radiative power emitted by j and absorbed by i. The graphical representation of the NER matrix highlights the radiative exchanges that dominate the radiative budget of the atmosphere and allows one to have a very good insight of the radiative exchanges. Results will be presented for clear sky atmospheres with Mid-Latitude Summer and Sub-Arctic Winter temperature profiles, and for the same atmospheres with three different types of clouds. The effect of scattering on long-wave radiative exchanges will also be analysed. 相似文献
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The recent hiatus in global temperature at the surface has been analysed by several studies, mainly using global climate models. The common accepted picture is that since the late 1990s, the increase in anthropogenic radiative forcings has been counterbalanced by other factors, e.g., a decrease in natural forcings, augmented ocean heat storage and negative phases of ocean–atmosphere-coupled oscillation patterns. Here, simple vector autoregressive models are used for forecasting the temperature hiatus in the period 2001–2014. This gives new insight into the problem of understanding the ocean contribution (in terms of heat uptake and atmosphere–ocean-coupled oscillations) to the appearance of this recent hiatus. In particular, considering data about the ocean heat content until a depth of 700 m and the Atlantic multidecadal oscillation is necessary for correctly forecasting the hiatus, so catching both trend and interannual variability. Our models also show that the ocean heat uptake is substantially driven by the natural component of the total radiative forcing at a decadal time scale, confining the importance of the anthropogenic influences to a longer range warming of the ocean. 相似文献
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Does temperature contain a stochastic trend: linking statistical results to physical mechanisms 总被引：1，自引：1，他引：0
Robert K. Kaufmann Heikki Kauppi Michael L. Mann James H. Stock 《Climatic change》2013,118(3-4):729-743
By construction, the time series for radiative forcing that are used to run the 20c3m experiments, which are implemented by climate models, impart non-stationary movements (either stochastic or deterministic) to the simulated time series for global surface temperature. Here, we determine whether stochastic or deterministic trends are present in the simulated time series for global surface temperature by examining the time series for radiative forcing. Statistical tests indicate that the forcings contain a stochastic trend against the alternative hypothesis that the series are trend stationary with a one-time structural change. This result is consistent with the economic processes that impart a stochastic trend to anthropogenic emissions and the physical processes that integrate emissions in the atmosphere. Furthermore, the stochastic trend in the aggregate measure of radiative forcing also is present in the simulated time series for global surface temperature, which is consistent with the relation between these two variables that is represented by a zero dimensional energy balance model. Finally, we propose that internal weather variability imposed on the stochastic trend in radiative forcings is responsible for statistical results, which gives the impression that global surface temperature is trend stationary with a one-time structural change. We conclude that using the ideas of stochastic trends, cointegration, and error correction can generate reliable conclusions regarding the causes of changes in global surface temperature during the instrumental temperature record. 相似文献
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利用SBDART（Santa Barbara DISORT Atmospheric Radiative Transfer）辐射传输模式,结合AERONET（Aerosol Robotic Network）北京站观测的气溶胶光学特性数据,评估北京地区近十年气溶胶以及黑碳气溶胶的辐射强迫,主要研究结果如下:北京近十年气溶胶平均光学厚度（aerosol optical depth, AOD440nm）为0.61±0.56,?ngstr?m波长指数均值为1.09,单次散射反照率（single scattering albedo, SSA440nm）的均值为0.888±0.045;AOD呈现下降趋势,SSA呈上升趋势,表明该区域气溶胶污染有所改善。晴空条件下,大气层顶、地面和大气的气溶胶直接辐射强迫多年均值分别为?24.91±19.80 W m?2、?65.52±43.78 W m?2、40.61±28.62 W m?2,即气溶胶对大气层顶和地表为冷却效应,对大气产生加热作用。气溶胶和黑碳气溶胶的直接辐射强迫绝对值的年际变化表现为微弱的下降趋势,季节变化特征为春夏季高,冬季低,这与AOD的变化规律一致。并且黑碳气溶胶的直接辐射强迫下降趋势与SSA的上升趋势呈现较好的反位相关系。 相似文献
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Simulation of the radiative effect of black carbon aerosols and the regional climate responses over China 总被引：10，自引：0，他引：10
As part of the development work of the Chinese new regional climate model (RIEMS), the radiative process of black carbon (BC) aerosols has been introduced into the original radiative procedures of RIEMS,and the transport model of BC aerosols has also been established and combined with the RIEMS model.Using the new model system, the distribution of black carbon aerosols and their radiative effect over the China region are investigated. The influences of BC aerosole on the atmospheric radiative transfer and on the air temperature, land surface temperature, and total rainfall are analyzed. It is found that BC aerosols induce a positive radiative forcing at the top of the atmosphere (TOA), which is dominated by shortwave radiative forcing. The maximum radiative forcing occurs in North China in July and in South China in April. At the same time, negative radiative forcing is observed on the surface. Based on the radiative forcing comparison between clear sky and cloudy sky, it is found that cloud can enforce the TOA positive radiative forcing and decrease the negative surface radiative forcing. The responses of the climate system in July to the radiative forcing due to BC aerosols are the decrease in the air temperature in the middle and lower reaches of the Changjiang River and Huaihe area and most areas of South China, and the weak increase or decrease in air temperature over North China. The total rainfall in the middle and lower reaches of the Changjiang River area is increased, but it decreased in North China in July. 相似文献
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The solution of the vector radiative transfer equation using the discrete ordinates technique: Selected applications 总被引：2，自引：1，他引：1
The paper is devoted to the presentation of a newly developed radiative transfer code SCIAPOL_1.0 for a plane-parallel turbid slab illuminated by the monodirectional wide beam. The SCIAPOL_1.0 is based on the discrete-ordinates solution of the vector radiative transfer equation.The code is applied to a number of problems, including studies of the applicability of the scalar approximation for the calculation of light reflectance from aerosols, clouds, and molecular atmospheres. We also study the accuracy of the single scattering approximation as applied to the calculation of light reflection from molecular and cloudy atmospheres and propose new approximations for the calculation of the reflection function and the degree of light polarization under unpolarized light illumination conditions. 相似文献
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《Atmospheric Research》2006,79(3-4):166-181
The change of cloud droplet spectra can modify the microphysics and radiative processes of the atmosphere, which in turn affects surface precipitation. In this paper, the impact of cloud droplet spectral change (CDSC) on mesoscale precipitation is studied by simulating two cases, a South China Storm on June 8, 1998 and a Yangtze River Storm on July 22, 2002, and employing the MM5V3 with newly developed, dual-parameterized explicit moisture scheme coupled to. The results show that CDSC has a slight influence on rainfall distribution/pattern, but can significantly change the precipitation intensity, especially the position and intensity of the precipitation centers. The effects of CDSC are more distinct in the daytime and have an obvious diurnal cycle on rain rate. Precipitation increase (decrease) due to CDSC is ascribed to the relative upper radiative cooling (heating) and lower radiative heating (cooling) in the daytime atmosphere. 相似文献
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气候模式中云的垂直重叠假定对模拟的地-气辐射的影响研究 总被引：6，自引：4，他引：2
本文将一种新的可以模拟云的多种垂直重叠假定的随机次网格云产生器 (SCG) 放入NCAR/CAM3气候模式中, 利用该产生器得到云的四种垂直重叠结构, 即最大重叠 (MO)、 随机重叠 (RO)、 最大-随机重叠 (MRO) 以及近年来发展的一般重叠 (GenO), 并以GenO为参照研究了这四种云的重叠结构对模拟的地-气辐射的影响, 为气候模式中云的次网格结构选择提供一定的依据。结果表明, MRO、 MO和RO总云量分别与GenO总云量 (全球平均0.64左右) 偏差约-0.012、 -0.034和0.026, 其中MRO最接近GenO。不同重叠假定对地面接收到的短波辐射通量 (DSR) 的改变显著, 在热带对流区达到16 W/m2以上, 相当于GenO下该地区相应量的8%～12%, 通过了95%信度检验; 在中高纬度低云量大的地区也达到4～8 W/m2。不同重叠假定对大气顶出射长波辐射 (OLR) 的改变比其对短波辐射通量的改变小得多, 在热带对流区有极大值3～4 W/m2。不同的云重叠结构的大气加热率垂直廓线不同, 从而影响大气热力结构, 其中长波加热率差值 (最大约0.1～0.26 K/d) 比短波加热率差值 (最大约0.01～0.025 K/d) 几乎大一个量级, 因此, 长波加热率的变化是影响大气热力层结的主要因素。云重叠假定影响地面和大气顶云辐射强迫, 并通过柱辐射强迫使得整层气柱的能量收支发生变化, 不同纬度变化趋势也不同, 从而系统性地改变地-气系统能量在各纬度地区的分配, 影响所模拟的气候系统的演变。 相似文献
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The influence of various cloud parameters and the interactions with the ground albedo and the solar zenith angle have been studied by means of model simulations. The radiative transfer model suitable for a cloudy atmosphere as well as for a clear atmosphere has been developed on the basis of the Discrete Ordinate Method. This study leads to a general understanding for cloudy atmospheres: in the presence of a uniform cloud, the cloud scattering is dominant to molecular and aerosol scattering, and it is also wavelength-independent; the ratio of transmitted irradiance in a cloudy atmosphere to that in the background clear atmosphere is independent of cloud height and solar zenith angle. That’s to say, the radiation downwelling out of a cloud is quite isotropic; it decreases approximately exponentially with the cloud optical depth at a rate related to the ground albedo; the reflected irradiance at the top of the atmosphere is dependent on cloud optical depth as well as on solar zenith angle, but not on ground albedo for clouds of not very thin optical depth. 相似文献
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Monte-Carlo method has been applied to investigate the radiance and radiative flux on the horizontallyinhomogeneous ground surface in a cloudy atmosphere.It has been found that the characteristics of theground radiance and flux are significantly changed by clouds.The flux in the quadrant toward the surfacewith higher reflectivity are greater than that toward the surface with lower reflectivity.And the flux variesacross the boundary of the two areas with different surface albedos.The effect of inhomogeneity of the surfacealbedo in a cloudy atmosphere can extend far to 20 km.In addition,the horizontal distribution of the fluxabsorbed by the ground is more homogeneous in a cloudy atmosphere than that in a clear air. 相似文献
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An Improved Atmospheric Vector Radiative Transfer Model Incorporating Rough Ocean Boundaries 
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下载免费PDF全文 The radiative transfer model (RT3), a vector radiative transfer (VRT) scheme in a plane-parallel atmosphere, was bounded by a rough ocean surface in this study. The boundary problem was solved using a Fourier series decomposition of the radiation field as a function of the azimuth. For the case of a rough ocean surface, the decomposition was obtained by developing both the Fresnel reflection matrix and the probability distribution of the water facet orientation as Fourier series. The effect of shadowing by ocean surface waves was also considered in the boundary condition. The VRT model can compute the intensity and degree of polarization of the light at the top of the atmosphere (TOA), the ocean surface, and any level of the atmosphere in the ocean-atmosphere system. The results obtained by our model are in good agreement with those computed by Ahmad’s model. The simulated results showed that the shadow effects of wave facets on the intensity and the degree of polarization are negligible except at the ocean surface near the grazing angle, possibly because we did not consider the effect of white caps. 相似文献
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利用毫米波云雷达、微波辐射计联合反演方法,对2015年11月11日安徽寿县的一次层状云过程的云参数进行了反演,将所得云参数加入到SBDART辐射传输模式中,进行辐射通量计算,并将计算的地面辐射通量与观测的地面辐射通量进行了对比分析。研究表明:1)利用毫米波雷达和微波辐射计数据联合反演的云参数比较可靠;2)利用SBDART模式并结合反演的云参数,可以准确实时地计算地面及其他高度层的长短波辐射通量;3)在反演的云参数中,光学厚度对地面各种辐射通量的影响是最大的,云层的光学厚度越大,到达地面的太阳短波辐射越小,地面反射短波辐射也越小。另外云底温度越高,云体向下发射的红外长波辐射越大。地面向上的长波辐射是地面温度的普朗克函数,随地面温度而变;4)云对地面的短波辐射强迫为负值,对地面有降温的作用。云对地面的长波辐射强迫是一个正值,对地面有一个增温的作用;5)云对地面的净辐射强迫随时间变化很大,它的正负与太阳高度角和云参数有关。 相似文献