共查询到18条相似文献，搜索用时 78 毫秒
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气象激光雷达的发展现状 总被引：8，自引：0，他引：8
激光雷达能用来测量云、雾、能见度、空中风场、大气密度和大气温度,也可以用来监测空气中的有害气体。该文介绍了用于气象探测的半导体激光雷达、微脉冲激光雷达、一般弹性散射激光雷达、多普勒激光雷达、差分吸收激光雷达和Raman激光雷达的发展现状和趋势,认为人眼安全、高重复频率和宽探测范围是气象激光雷达的发展方向。固体激光雷达的气象应用最广泛,微脉冲激光雷达能同时测量云底高度、能见度和获得大气气溶胶消光廓线,有比较好的应用前景,半导体激光雷达是测量云底高度的理想工具。 相似文献
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基于西安泾河国家气象站2021年微波辐射计、西安理工大学研制的大气温湿度廓线激光雷达等设备观测数据反演计算0～10 km 以下的温湿度，通过与探空资料的对比分别评估了微波辐射计和激光雷达的探测性能。结果表明，二者反演的温度均与探空数据具有较好的一致性，激光雷达反演的温度和探空温度的相关系数为0997，均方根误差在15～25 K之间，微波辐射计反演的温度和探空温度的相关系数为0973，均方根误差在15～50 K之间；在反演相对湿度方面激光雷达优于微波辐射计，激光雷达反演的相对湿度和探空相对湿度的相关系数为0964，均方根误差在5%～15%之间，微波辐射计反演的相对湿度和探空相对湿度的相关系数为0632，均方根误差在20%左右。 相似文献
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介绍了激光雷达在气象上的作用,并在使用光子计数法的基础上利用激光雷达方程计算出了在不同高度处大气的后向散射光子.为进行激光大气探测奠定理论基础. 相似文献
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基于激光雷达和微波辐射计观测确定混合层高度方法的比较 总被引：2，自引：0，他引：2
利用苏州地区2010年1月4,7,16日和2月4日4天的激光雷达及微波辐射计观测资料,比较了不同遥感手段探测晴天大气混合层高度的差异,发现试验期间该地区的混合层高度在300~1500 m之间。利用梯度法、标准偏差法、小波法从激光雷达数据中提取混合层高度并进行了对比,结果表明三种方法都能较好地反演混合层高度并且一致性较好,三者差异主要存在于大气边界层的发展和消亡阶段;梯度法和小波法结果无明显差异,而标准偏差法结果稍高于其他方法。在此基础上,利用微波辐射计探测的大气温度,使用温度梯度法估算大气混合层高度,并与激光雷达探测结果进行了比较,结果表明,大多数情况下激光雷达探测结果高于微波辐射计观测结果;两种遥感手段有较好的相关性,相关系数为0.76。激光雷达同微波辐射计结果存在差异,尤其是在边界层的发展和消散阶段,这是由两种遥感手段探测原理不同造成的。 相似文献
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利用离散偶极子近似法,数值计算分析了随机取向旋转椭球体沙尘气溶胶粒子在尺度参数为0.1~23时（波长0.55 μm对应有效半径为0.01~2 μm）的激光雷达线退偏比特性,通过比较其不同旋转椭球体轴半径比下的差别,研究了粒子非球形性程度对单分散和多分散沙尘气溶胶激光雷达线退偏比特性的影响.单分散旋转椭球体沙尘气溶胶的激光雷达线退偏比对粒子的轴半径比和尺度参数有很强的依赖性;对于长旋转椭球体,沙尘激光雷达线退偏比较小值出现在瑞利散射区,而较大的值出现在米散射区;对于扁旋转椭球体,在米散射区较大沙尘粒子也可以产生较小的激光雷达线退偏比,例如,轴半径比为1/16,尺度参数为3时的沙尘激光雷达线退偏比仅为0.1%.就随机取向旋转椭球体沙尘粒子而言,对于单分散系,仅当尺度参数小于0.5时,非球形特征越明显,其激光雷达线退偏比越大;而对多分散系,非球形特征越明显,其激光雷达线退偏比越大. 相似文献
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Analytical solutions of convective waves in the convective boundary layer (CBL) were obtained with two-layer linearized atmospheric
equations including Rayleigh friction, which represents the turbulent viscosity in the lower CBL. The analytical model shows
that the interaction between the convection in the lower layer and gravity waves in the upper layer is one of the causes for
the formation of convective bands. The flow and temperature fields obtained by the analytical model present the main characteristics
of convective bands found in field observations. We have also investigated the influences of atmospheric conditions on the
characteristics of the bands. Results accord with previous knowledge about these phenomena. 相似文献
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Dipl-Ing. K. Krettenauer Prof. Dr. U. Schumann 《Meteorology and Atmospheric Physics》1989,41(3):165-179
Summary The influence of a wavy surface on thermal convection of Rayleigh-Bénard type in a Boussinesq fluid is investigated by direct numerical simulations. The surface height varies sinusoidally in one direction. The wave amplitude amounts up to 10% of the fluid layer height and the wavelength equals about the critical wavelength of Rayleigh-Bénard convection. The horizontal size of the computational domain equals this wavelength. For isothermal no-slip boundaries, two-dimensional convection sets in at subcritical Rayleigh numbers in close agreement with linear theory. The heat-transfer rate grows almost with the square of the surface-wave amplitude. Convection in a fluid layer over a no-slip surface with prescribed heat flux and an adiabatic free-slip boundary at the top is investigated for supercritical Rayleigh numbers and a Prandtl number of 0.7 in two and three dimensions. Two-dimensional simulations show oscillatory roll convection which becomes almost stationary if the Rayleigh number is of order 7000 or less. The two-dimensional convection is unstable with respect to three-dimensional disturbances and a cross-role pattern evolves even over a surface which is undulated in one direction only. For Rayleigh numbers exceeding about 15 000, the flow becomes turbulent. The results exhibit little sensitivity of the convection to the wavy surface for a 10% amplitude.With 11 Figures 相似文献
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H. L. Kuo 《Boundary-Layer Meteorology》1979,17(1):29-39
Previous theoretical and observational investigations have shown that vertical plumes are formed in the high Rayleigh number convection field over heated horizontal surfaces and that these plumes become unsteady and turbulent when the Rayleigh number is higher than about 20 times its critical value R
c. Based on these results, we conclude that the dissipation of kinetic energy takes place mainly in the surface boundary layer in high Rayleigh number laminar convection and mainly in the vertical plumes in turbulent convection, while the conversion of eddy potential energy into kinetic energy is accomplished mainly in the well-mixed main body of the fluid. On making use of these rather general conclusions concerning the kinetic energy generation and dissipation processes in the energy integrals, we are able to derive the well known 5/4 and 4/3 power laws of upward heat transfer by laminar and turbulent convections theoretically. 相似文献
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J.-P. Boulanger 《Climate Dynamics》2001,17(2-3):159-173
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
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An algorithm for remote sensing of water color from space 总被引：3，自引：0，他引：3
The ocean color algorithm proposed in this paper takes into account the effects of Rayleigh and aerosol scattering. The inherent reflectance and the diffuse transmittance of the Rayleigh atmosphere are expressed as functions of optical thickness and satellite measurement geometry with the aid of simple and accurate formulas. In the case of a turbid atmosphere, from which the aerosol optical thickness is unknown, the aerosol contribution is estimated with the aid of a measurement in a channel where the ocean is a blackbody (in the red or near infrared). If the relationship between the ocean color and the chlorophyll-like pigment concentration is assumed to be known at sea level, it is shown that the chlorophyll-like pigment concentration at an open ocean site can be determined from space to within a factor of 1.5 to 3 (uncertainty equal to 0.2 to 0.5 log interval), depending on the atmospheric turbidity. 相似文献
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Absorption of solar radiation within the thermal molecular sublayer of the ocean can modify the temperature difference across the cool skin as well as the air-sea gas transfer. Our model of renewal type is based on the assumption that the thermal and diffusive molecular sublayers below the ocean surface undergo cyclic growth and destruction, the heat and gas transfer between the successive burst events are performed by molecular diffusion. The model has been upgraded to include heating due to solar radiation. The renewal time is parameterized as a function of the surface Richardson number and the Keulegan number. A Rayleigh number criterion characterizes the convective instability of the cool skin under solar heating. Under low wind speed conditions, the solar heating can damp the convective instability, strongly increasing the renewal time and correspondingly decreasing the interfacial gas exchange. In the ocean, an additional convective instability caused by salinity flux due to evaporation becomes of importance in such cases. The new parameterization is compared with the cool skin data obtained in the western equatorial Pacific during the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment in February 1993. In combination with a model of the diurnal thermocline it describes main features of the field data both in nighttime and daytime. Under low wind speed conditions (< 5 m s-1) diurnal variations of the sea surface temperature due to the formation of a diurnal thermocline were substantially larger than those across the cool skin. Under wind speeds > 5 m s-1, diurnal variations of the surface temperature due to the variations of the thermal molecular sublayer become more important. 相似文献
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Experimental observations of cellular convection between two rigid, horizontal, conducting boundaries are reported for two different cases. First, the stability of two-dimensional roll convection of various wavenumbers and Rayleigh numbers is investigated in fluids of Prandtl numbers 16 and 2.7. The results qualitatively agree with earlier observations by Busse and Whitehead of fluid with Prandtl number 126 but they differ somewhat quantitatively. Second, the stability of the bimodal flow, consisting of two rolls of differing and perpendicular wavenumber, is observed to be stable for given bandwidths and ranges of Rayleigh numbers when the configuration of the bimodal flow, consisting of two sets of rolls at right angles, is flawless — without any disruptions in the periodic matrix. The stability range differs from earlier experiments and from our own experiments in which the bimodal planform is uncontrolled. 相似文献