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1.
STUDYING THE SKY RADIANCE AND DEGREE OF POLARIZATION AND SOUNDING THE OPTICAL CHARACTERISTICS OF ATMOSPHERIC AEROSOL 
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下载免费PDF全文 The sky radiance and degree of polarization with multiple scattering process considered were calculated inthis paper by solving vector form radiative transfer equation iteratively. Numerical experiment for simultaneouslyretriving the size distribution (SD) and the complex refractive index (CRI) of aerosol particle was conductedwith the degree of polarization of skylight (DPS) and the library method used. It is shown from the resultsthat the real part of CRI is always sensitive to DPS. But situation is somewhat complicated for the imaginarypart of CRI. Therefore, it is expected that the real part of CRI can be retrieved from DPS and its imaginarypart should be retrieved as the particle is large in size. In this paper, seven sets of DPS measurements on 6 January,1990 in Beijing were given and the optical characteristics of aerosol were retrieved. 相似文献
2.
Summary The diffuse sky radiation component in the ultraviolet wavelengths is often at least 50% of the global irradiance under clear skies, and is the dominant component of ultraviolet global radiation under translucent overcast skies. The distribution of sky radiance was measured in a rural area and modeled for wavelength bands of ultraviolet-B (UVB, 280–320 nm) and ultraviolet-A (UVA, 320–400 nm). Sky radiance measurements were made during the summer of 1993 over a wide range of solar zenith angles using radiance sensors mounted on a hand-operated hemispherical rotation mount. UVB irradiance measurements were also made during each scan. Since the ratio of measured irradiance under overcast skies and that predicted for clear skies was not correlated with cloud base height, opaque cloud fraction, or solar zenith angle, it was concluded that the scattering from the clouds dominated the global irradiance, and this scattering was relatively unaffected by the scattering off opaque clouds in the translucent atmosphere.Analysis of the translucent overcast sky UVA and UVB radiance measurements using a semi-empirical distribution model showed that the spectral influences on multiple scattering, single scattering, and horizon brightening components of the distributions agreed with basic atmospheric radiation theory. The best model used solar zenith, the sky zenith, and the scattering angle with resultant coefficient of determination values of 0.62 and 0.25 for the UVA and UVB respectively. The developed equations can be applied directly to the diffuse sky irradiance on the horizontal to provide radiance distributions for the sky.With 6 Figures 相似文献
3.
Numerous factors can influence the radiative transfer simulation of hyper-spectral ultraviolet satellite observation,including the radiative transfer scheme, gaseous absorption coefficients, Rayleigh scattering scheme, surface reflectance, aerosol scattering, band center wavelength shifts of sensor, and accuracy of input profiles. In this study, a Unified Linearized Vector Radiative Transfer Model(UNL-VRTM) is used to understand the influences of various factors on the top of atmosphere(TOA) normalized radiance in the ultraviolet(UV) region. A benchmark test for Rayleigh scattering is first performed to verify the UNL-VRTM accuracy, showing that the model performances agree well with earlier peer-reviewed results. Sensitivity experiments show that a scalar radiative transfer approximation considering only ozone and a constant surface reflectance within the UV region may cause significant errors to the TOA normalized radiance. A comparison of the Ozone Mapping and Profiler Suite(OMPS) radiances between simulations and observations shows that the surface reflectance strongly influences the accuracy for the wavelengths larger than 340 nm. Thus, using the surface reflectivity at 331 nm as a proxy for simulating the whole OMPS hyperspectral ultraviolet radiances is problematic. The impact of rotational Raman scattering on TOA radiance can be simulated through using SCIATRAN, which can also reduce the difference between measurements and simulations to some extent. Overall, the differences between OMPS simulations and observations can be less than 3% for the entire wavelengths. The bias is nearly constant across the cross-track direction. 相似文献
4.
Qiu Jinhuan 《大气科学进展》1988,5(3):311-323
Based on the radiative transfer calculation results, three approximate expressions of the sky radiance in almucantar and its
increment caused by surface albedo are presented. They are simple, but accurate enough. The dependence of the fitted aerosol
scattering phase functions on refractive index is also studied, and its reasonable form is given. For Junge size distribution,
the approximate equations of the phase functions with some special scattering angles are obtained. These approximate equations
significantly simplify the retrieval algorithm of simultaneous determination of aerosol size distribution and its refractive
index and surface albedo. This method can be realized with a microcomputer, and has been used to process and analyse the experimental
data measured in Hefei of Anhui Province. 相似文献
5.
介绍并验证了一种快速、精确地计算Jacobian的解析方法(辐射传输方程的线性化,简称LR方法),将其结果与NAST-I真正的线性模式及数值方法(差分方法)的Jacobian值进行比较。结果表明,这种解析算法不仅快速、精确,而且独立于辐射传输方程,在有效Jacobian计算中只需要输入大气透过率,可适用于任何垂直探测器权重函数的计算。 相似文献
6.
Qiu Jinhuan 《大气科学进展》1988,5(3):311-324
Based on the radiative transfer calculation results, three approximate expressions of the sky radiance in almucantar and its increment caused by surface albedo are presented. They are simple, but accurate enough. The dependence of the fitted aerosol scattering phase functions on refractive index is also studied, and its reasonable form is given. For Junge size distribution, the approximate equations of the phase functions with some special scattering angles are obtained. These approximate equations significantly simplify the retrieval algorithm of simultaneous determination of aerosol size distribution and its refractive index and surface albedo. This method can be realized with a microcomputer, and has been used to process and analyse the experimental data measured in Hefei of Anhui Province. 相似文献
7.
The variations of albedo and absorptivity of the snow cover are considered caused by the presence of the snow roughness in
the form of sastrugi. The numerical modeling is carried out within the framework of statistical approach based on the analytic
averaging of the radiative transfer equation and statistically homogeneous model on the basis of Poisson flows of points at
the straight lines. The estimates of the influence of 3D-effects of the rough surface are represented depending on optical
and geometrical characteristics of sastrugi and on the illumination conditions. It is demonstrated that if the absorption
by the snow particles is weak (the single scattering albedo w = 0.9999) the reflection of radiation by snow decreases by ∼ 2–3% when the sastrugi appear. This effect is more significant
in near infrared spectral region where w is below 0.99. 相似文献
8.
Kwang-Mog Lee Joong-Hyun Park Myoung-Hwan Ahn Mi-Lim Ou Yoonjae Kim 《Asia-Pacific Journal of Atmospheric Sciences》2012,48(2):135-143
Infrared radiance spectra measured in space or on the ground have been used for many applications, such as the retrieval of atmospheric temperature and humidity profiles. The Korean Meteorological Administration (KMA) recently installed an Atmospheric Emitted Radiance Interferometer (AERI) system at the Korea Global Atmosphere Watch Center (36°32??N, 125°19??E) in Anmyondo to measure the downward radiance spectra on the ground. For further utilization of such interferometeric radiance measurements, an accurate line-by-line radiative transfer model is required. This study introduces a line-by-line radiative transfer model developed at Kyungpook National University (KNU_LBL) and presents comparisons of spectra simulated using the KNU_LBL model and measured by the AERI system, that is installed inside a secure container. When compared with the Atmospheric and Environmental Research (AER) radiative transfer codes, the KNU_LBL model provides nearly identical spectra for various model atmospheres. The simulated spectra are also in good agreement with the AERI spectra for clear sky conditions, and a further improvement is made when taking into account of the emissions and absorption by CO2 and H2O for the light path inside the container, even though the path is short. 相似文献
9.
Summary The influence of the micro- and macrophysics of water clouds on the scattering and radiative properties of clouds is investigated using versatile cloud drop size distributions (DSDs) and Mie theory for single scattering and the delta-Eddington approximation for multiple scattering. A new parameterization scheme for the shortwave radiative properties of water clouds is presented. As for single- scattering properties, a new parameterization for cloud optical thickness () is proposed. This is based upon the seperation of the dependence of on the total number of DSDs, the cloud thickness, and the liquid water content, combined with equivalent radius. The cloud bulk radiative properties, i.e., the flux reflectance, transmittance, and absorptance, are uniquely fitted by a dimensionless parameter (X) or the optical thickness. The parameterization is compared with other schemes. Finally, the features and potential use of the scheme are discussed.With 5 Figures 相似文献
10.
Qiu Jinhuan 《大气科学进展》1986,3(1):1-9
An approximate expression of the sky radiance in almucantar is confirmed in this paper. Under the conditions with molecular optical depth<0.3, aerosol (or cloud) optical depth<0.6, solar zenith angle< 75° and scattering angle<30°, the errors of the sky radiance and the aerosol phase function computed from the expression are respectively less than 8 % and 10 %, but the phase functions computed from Box-Deepak formula and single-scattering formula can be 84 % and 260 % more than the exact value, respectively. Furthermore, by use of the expression we have inferred the volume scattering functions of 1°≤θ≤30° for retrieving aerosol size distribution with the conclusion that the distribution information in the range of 0.1相似文献
11.
On the basis of forward IR radiation transfer analyses for an atmosphere containing semi-transparent, non-black cirrus, parameterization equations are derived for the retrieval of the cloud optical depth and cloud temperature utilizing AVHRR 3.7 and 10.8 μum channels. The retrieval techniques developed involve the use of either dual-frequency or dual-scanning angle radiance observations. We show that the cloud optical depth and cloud temperature may be inferred successively from the observed brightness temperature differences using these two techniques. Numerical experiments anderror analyses demonstrate that the dual-frequency method is specifically appropriate for optically thin cirrus cases (τ <1). In case the optical depth of cirrus is close to 3, combination of dual-frequency and dual-scanning angle methods is shown to give reasonable accuracy for the cloud optical depth and temperature retrieval. 相似文献
12.
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
13.
A two-step method is employed in this study to retrieve vertical ozone profiles using scattered measure- ments from the limb of the atmosphere. The combination of the Differential Optical Absorption Spectroscopy (DOAS) and the Multiplicative Algebraic Reconstruction Technique (MART) is proposed. First, the limb radiance, measured over a range of tangent heights, is processed using the DOAS technique to recover the effective column densities of atmospheric ozone. Second, these effective column densities along the lines of sight (LOSs) are inverted using the MART coupled with a forward model SCIATRAN (radiative transfer model for SCIAMACHY) to derive the ozone profiles. This method is applied to Optical Spectrograph and Infra Red Imager System (OSIRIS) radiance, using the wavelength windows 571-617 nm. Vertical ozone profiles between 10 and 48 km are derived with a vertical resolution of 1 km. The results illustrate a good agreement with the cloud-free coincident SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) ozone measurements, with deviations less than ± 10% ( ± 5% for altitudes from 17 to 47 km). Furthermore, sensitivities of retrieved ozone to aerosol, cloud parameters and NO 2 concentration are also investigated. 相似文献
14.
J. I. F. King Dr. R. G. Hohlfeld J. C. Kilian 《Meteorology and Atmospheric Physics》1989,41(3):115-126
Summary A new theoretical approach is developed for remote temperature sensing based on application of Laplace transform techniques to the radiative transfer equation. This approach allows calculation of the atmospheric temperature profile from measurements of the upwelling radiance and its derivatives. Atmospheric temperatures are obtained by this technique without the use of anya priori temperature information. This technique is applied toboth synthetic data for detailed numerical study, and to measurements of the upwelling radiance taken with the Tiros Operational Vertical Sounder (TOVS). Limitations arising from experimental errors, truncation errors, round-off, numerical errors, and instability of numerical Laplace transformation are discussed.With 9 Figures 相似文献
15.
三维辐射传输模式分析非均匀云对天空辐射场影响 总被引：4，自引：1，他引：3
为了解非均匀分立云体分布状况下的天空辐射场与无云晴空辐射场的差异, 本文借助一个三维辐射传输数值模式SHDOM模拟了离散云块分布条件下的天空辐射场分布, 重点分析不同云况分布情况下“非云”大气的辐射分布特征, 并将该区域与无云晴空大气辐射场的相同区域进行了比对。工作主要从辐亮度以及450 nm/650 nm的辐射比两参数入手进行讨论。研究发现, 相对无云晴空大气, 云的存在会对周围“非云”大气散射辐射产生影响, 影响程度与云量、云及气溶胶光学厚度等参数相关。数值模拟结果表明, 在云量不太大的条件下, 无云视场空间的大部分辐射值与无云晴空相比变化很小, 集中在±2％之间。这一结果表明, 已有的一维均匀大气辐射传输模式运算结果所得云与非云相元的判据基本适用于非均匀分布的有云大气。另一方面, 模拟结果表明我们也完全可以利用非均匀有云大气中的无云视场观测结果进行大气气溶胶等晴空大气光学特征的探测研究。 相似文献
16.
There are large uncertainties in the quantitative assessment of radiative effects due to atmospheric dust aerosol. The optical properties contribute much to those uncertainties. The authors perform several sensitivity experiments to estimate the impacts of optical characteristics on regional radiative forcing in this paper. The experiments involve in refractive indices, single scattering aibedo, asymmetry factor and optical depth. An updated dataset of refractive indices representing East Asian dust and the one recommended by the World Meteorology Organization （WMO） are contrastively analyzed and used. A radiative transfer code for solar and thermal infrared radiation with detailed aerosol parameterization is employed. The strongest emphasis is on the refractive indices since other optical parameters strongly depend on it, and the authors found a strong sensitivity of radiative forcing on refractive indices. Studies show stronger scattering, weaker absorption and forward scattering of the East Asian dust particles at solar wavelengths, which leads to higher negative forcing, lower positive forcing and bigger net forcing at the top of the atmosphere （TOA） than that of the WMO dust model. It is also found that the TOA forcings resulting from these two dust models have opposite signs in certain regions, which implies the importance of accurate measurements of optical properties in the quantitative estimation of radiative forcing. 相似文献
17.
We summarize an on-line coupled meteorological–emissions–photochemical modelling system that allows feedback from air-quality/chemistry
to meteorology via radiative forcing. We focus on the radiative-forcing impacts (direct effects) of ozone. We present an application
of the coupled modelling system to the episode of 23–31 July 1998 in Portland, Oregon, U.S.A. Results suggest that the inclusion
of radiative-forcing feedback produces small but accountable impacts. For this region and episode, stand-alone radiative transfer
simulations, i.e., evaluating the effects of radiative forcing independently of changes in meteorology or emissions, suggest
that a change of 1 ppb in ground-level ozone is approximately equivalent to a change of 0.017 W m−2 in radiative forcing. In on-line, coupled, three-dimensional simulations, where the meteorological dependencies are accounted
for, domain-wide peak ozone concentrations were higher by 2–4 ppb (relative to a simulated peak of 119.4 ppb) when including
the effects of radiative-forcing feedback. A scenario of 10% reduction in anthropogenic emissions produced slightly larger
decreases in ozone, an additional 1 ppb in local-peak reductions, relative to scenarios without feedback. 相似文献
18.
东亚地区气象参数卫星遥感反演理论和方法研究Ⅱ:ISPRM和VSPRM2 总被引：1，自引：0，他引：1
在改进的同步物理模式（ＩＳＰＲＭ）实践基础上,根据泛函数变分原理,按ＴＯＶＳ遥感方程,提出了较普遍的变分同步物理反演模式（ＶＳＰＲＭ２）,其一级功能（ＶＳＰＲＭ１）和ＩＳＰＲＭ完全相同。ＶＳＰＲＭ从协合（ｓｙｎｅｒｇｙ）遥感反演机理,进一步拓宽和发展了ＩＳＰＲＭ模式。分析了ＶＳＰＲＭ２模式性能,指出这类模式的反演潜力。特别着重分析了模式的水汽核函数参数化和水汽遥感反演问题。针对这类非适定反问题的强欠定性质,为妥善使用先验信息,以获得精确的正演辐射率Ｒ。,还对透射率精确计算,低层温、湿廓线反演通道最佳选择和云层影响修正的改进作了进一步分析。经过长期业务运行条件反演比较实验,结果表明改进的物理反演方法（ＩＳＰＲＭ）是适于中国大陆包括青藏高原温、湿参数分布的反演方法,特别在有云条件下能反演出温、湿廓线。 相似文献
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20.
本文根据参数化的多次散射雷达方程,分析了激光多次散射对激光回波信号和一次散射雷达方程反演结果的效应,提出了迭代前向积分法和迭代后向积分法以求解参数化的多次散射雷达方程,并根据多次散射信号对云和气溶胶的前向散射相函数的高度敏感性提出了一个从双接收视场的多次散射激光回波信号,同时确定云和气溶胶消光系数分布和前向散射相函数的方法.此外,本文还根据数值试验分析了这些反演方法在地基激光雷达和空间站激光雷达两种情形下的适用性. 相似文献