States of maximum entropy production in a one-dimensional vertical model with convective adjustment   总被引：2，自引：0，他引：2  

By TONI PUJOL  JOAQUIM FORT 《地球，A辑:动力气象学与海洋学》2002,54(4):363-369

We investigate the hypothesis that the atmosphere is constrained to maximize its entropy production by using a one-dimensional (1-D) vertical model. We prescribe the lapse rate in the convective layer as that of the standard troposphere. The assumption that convection sustains a critical lapse rate was absent in previous studies, which focused on the vertical distribution of climatic variables, since such a convective adjustment reduces the degrees of freedom of the system and may prevent the application of the maximum entropy production (MEP) principle. This is not the case in the radiative-convective model (RCM) developed here, since we accept a discontinuity of temperatures at the surface similar to that adopted in many RCMs.
For current conditions, the MEP state gives a difference between the ground temperature and the air temperature at the surface ≈10 K. In comparison, conventional RCMs obtain a discontinuity ≈2K only. However, the surface boundary layer velocity in the MEP state appears reasonable (≈m s⁻¹). Moreover, although the convective flux at the surface in MEP states is almost uniform in optically thick atmospheres, it reaches a maximum value for an optical thickness similar to current conditions. This additional result may support the maximum convection hypothesis suggested by Paltridge (1978 ).  相似文献   

Large-scale atmospheric circulation changes are associated with the recent loss of Arctic sea ice   总被引：21，自引：0，他引：21  

By JAMES E. OVERLAND  MUYIN WANG 《地球，A辑:动力气象学与海洋学》2010,62(1):1-9

  相似文献   

Geochemistry of Lavas from Taal Volcano, Southwestern Luzon, Philippines: Evidence for Multiple Magma Supply Systems and Mantle Source Heterogeneity   总被引：4，自引：1，他引：4  

MIKLIUS  ASTA; FLOWER  MARTIN F. J.; HUIJSMANS  JOEP P. P.; MUKASA  SAMUEL B.; CASTILLO  PATERNO 《Journal of Petrology》1991,32(3):593-627

Taal Volcano is a highly active center in the southwest Luzonvolcanic field. Recent eruptions are confined to Volcano Island,a plexus of cinder cones and tuff rings surrounding a centralcrater, occupying (and post-dating) a massive volcano-tectonicdepression resulting from multiple phases of collapse. Taallava series can be distinguished from each other by differencesin major and trace element trends and trace element ratios,indicating multiple magmatic systems associated with discretecenters in time and space. On Volcano Island, contemporaneous lava series range from typicallycalc-alkaline to iron-enriched. Major and trace element variationin these series can be modelled by fractionation of similarassemblages, with early fractionation of titano-magnetite inless iron-enriched series. However, phase compositional andpetrographic evidence of mineral-liquid disequilibrium suggeststhat magma mixing played an important role in the evolutionof these series. We interpret this to mean that mixing occurredalong a line of descent defined by fractional crystallization,with mixing occurring over larger compositional intervals inthe less iron-enriched series, consistent with numerical modelling. Between-series incompatible element ratio differences are notexplicable through differential partial melting of a homogeneoussource (also confirmed by variation in Pb isotopic ratios),suggesting a supply system from discrete melt zones in heterogeneousmantle.  相似文献   

Suspension and calibration of a sediment trap   总被引：5，自引：0，他引：5  

By Lars Håkanson 《Aquatic Sciences - Research Across Boundaries》1984,46(1):171-175

The aim of this technical note is to introduce a new, simple construction of a buoy-carried, suspended sediment trap that meets given demands concerning design (geometry of vessels) and stability during the registration period. The device is based on a ball-and-socket joint in the center and two Plexiglas cylinders (D=5cm, H=30cm) on PVC plastic arms. The suspension consists of only three parts. To determine the optimal construction, the apparatus has been calibrated in a circulating flume at various water velocities.  相似文献   

FREQUENCY-SELECTIVE DESIGN OF THE KIRCHHOFF MIGRATION OPERATOR1     

SAMUEL H. GRAY 《Geophysical Prospecting》1992,40(5):565-571

Integral migration techniques perform a sum over an aperture of input traces to obtain output at a single point. The length of the aperture is limited by a spatial Nyquist criterion, which typically prohibits imaging very steep dips at very high frequencies without generating severe migration artifacts (migration operator aliasing). For time-domain Kirchhoff migration, this can be a fatal shortcoming. The standard way to address this problem is to interpolate traces spatially before migration. This reduces the trace spacing, thereby increasing the frequency content which can be migrated without aliasing at steep dips. An alternative remedy to the operator aliasing problem is to modify the phase response of the Kirchhoff migration operator. This operator is frequency-selective across the migration aperture: it passes all temporal frequencies of the input traces in the innermost portion of the aperture (referring to the shallow dips), and gradually cuts out the higher frequencies as it approaches the outer portion of the aperture. Thus, while all frequencies of the input data contribute to the shallow-dip portion of the migrated image, only the permissible low frequencies of the input data contribute to imaging the steepest dips. Using a simple realization of a frequency-selective Kirchhoff migration operator, this technique is illustrated on a synthetic data set involving greater than vertical dips.  相似文献   

运用上月各气象要素的特征来预告下月雨量——(沈阳夏季各月雨量作例)     

杨鉴初  刘钟玲 《气象学报》1953,24(1):159-172

一个地方下月的雨量,能不能从当地上月天气演变的结果所记录下来的各种气象要素的数值来推测呢?现在这篇报告的目的就想解答这个问题。关於这方面的研究,以前早有人注意,例如竺可桢教授研究过冬天温度与夏季雨量的关系,  相似文献   

Intermediate time error growth and predictability: tropics versus mid-latitudes     

By DAVID M. STRAUS  DAN PAOLINO 《地球，A辑:动力气象学与海洋学》2009,61(5):579-586

The evolution of identical twin errors from an atmospheric general circulation model is studied in the linear range (small errors) through intermediate times and the approach to saturation. Between forecast day 1 and 7, the normalized error variance in the tropics is similar to that at higher latitudes. After that, tropical errors grow more slowly. The predictability time τ taken for tropical errors to reach half their saturation values is larger than that for mid-latitudes, especially for the planetary waves, thus implying greater potential predictability in the tropics.
The discrepancy between mid-latitude and tropical τ is more pronounced at 850 hPa than at 200 hPa, is largest for the planetary waves, and is more pronounced for errors arising from wave phase differences (than from wave amplitude differences).
The spectra of the error in 200 hPa zonal wind show that for forecast times up to about 5 d, the tropical error peaks at much shorter scales than the mid-latitude errors, but that subsequently tropical and mid-latitude error spectra look increasingly similar.
The difference between upper and lower level tropical τ may be due to the greater influence of mid-latitudes at the upper levels.  相似文献   

On the selection of prognostic moments in parametrization schemes for drop sedimentation     

By ULRIKE WACKER  CHRISTOF LÜPKES 《地球，A辑:动力气象学与海洋学》2009,61(4):498-511

Common parametrization models for cloud microphysical processes use condensate mass density and/or particle number density as prognostic properties. However, other moments of the particle size distribution can likewise be chosen for prediction. This study deals with parametrization models with one and two, respectively, prognostic moments for the sedimentation of drop ensembles. The spectral resolving model defines the reference solution.
The evolution of the vertical profiles of liquid water content, drop number density and rain rate strongly depend on the choice of the prognostic moments in the parametrization models. In models with a single prognostic moment, its vertical profile is copied by all other moments. The moment of most physical pertinence is recommended for prediction. In models with two prognostic moments, the vertical profiles of all moments differ. The orders of the prognostic moments should be chosen close to the order of moments of highest relevance. Otherwise large errors occur. For example, comparison of modelled versus observed radar reflectivity (6th moment with respect to diameter) does not tell much about the quality of other properties if reflectivity is diagnosed from for example, number density and mass density. Furthermore, mass conservation is fulfilled only if mass density is forecasted.  相似文献   

沈积岩石学     

克鲁比  比迪詹  李广源 《地质论评》1947,12(Z2):307-309

沈积学,在二十世纪初叶始渐起而为地质学中之新支,近数十年来随着石油工业之发达,而日趋蓬勃;一变昔日仅以岩石性质研究为沈积原因之解说,而侧重沈积作用及沈积环境之  相似文献   

Numerical simulations of optical properties of Saharan dust aerosols with emphasis on lidar applications     

By M. WIEGNER  J. GASTEIGER  K. KANDLER  B. WEINZIERL  K. RASP  M. ESSELBORN  V. FREUDENTHALER  B. HEESE  C. TOLEDANO  M. TESCHE  D. ALTHAUSEN 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):180-194

In the framework of the Saharan Mineral Dust Experiment (SAMUM) for the first time the spectral dependence of particle linear depolarization ratios was measured by combining four lidar systems. In this paper these measurements are compared with results from scattering theory based on the T-matrix method. For this purpose, in situ measurements—size distribution, shape distribution and refractive index—were used as input parameters; particle shape was approximated by spheroids. A sensitivity study showed that lidar-related parameters—lidar ratio   S _p   and linear depolarization ratio  δ _p   —are very sensitive to changes of all parameters. The simulated values of the  δ _p   are in the range of 20% and 31% and thus in the range of the measurements. The spectral dependence is weak, so that it could not be resolved by the measurements. Calculated lidar ratios based on the measured microphysics and considering equivalent radii up to 7.5 μm show a range of possible values between 29 and 50 sr at  λ= 532 nm  . Larger   S _p   might be possible if the real part of the refractive index is small and the imaginary part is large. A strict validation was however not possible as too many microphysical parameters influence   S _p   and  δ _p   that could not be measured with the required accuracy.  相似文献