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1.
考虑了一类索赔计数相依的风险模型,该模型假设每次主索赔可随机产生一副索赔,得到了该风险模型生存概率所满足的微积分方程,并在索赔额为指数分布的情形下,给出了生存概率的精确表达式. 相似文献
2.
The streamflow over the Yellow River basin is simulated using the PRECIS （Providing REgional Climates for Impacts Studies） regional climate model driven by 15-year （1979-1993） ECMWF reanalysis data as the initial and lateral boundary conditions and an off-line large-scale routing model （LRM）. The LRM uses physical catchment and river channel information and allows streamflow to be predicted for large continental rivers with a 1°×1° spatial resolution. The results show that the PRECIS model can reproduce the general southeast to northwest gradient distribution of the precipitation over the Yellow River basin, The PRECIS- LRM model combination has the capability to simulate the seasonal and annual streamflow over the Yellow River basin. The simulated streamflow is generally coincident with the naturalized streamflow both in timing and in magnitude. 相似文献
3.
An investigation of the sensitivity of a land surface model to climate change using a reduced form model 总被引：1，自引：0，他引：1
In an illustration of a model evaluation methodology, a multivariate reduced form model is developed to evaluate the sensitivity
of a land surface model to changes in atmospheric forcing. The reduced form model is constructed in terms of a set of ten
integrative response metrics, including the timing of spring snow melt, sensible and latent heat fluxes in summer, and soil
temperature. The responses are evaluated as a function of a selected set of six atmospheric forcing perturbations which are
varied simultaneously, and hence each may be thought of as a six-dimensional response surface. The sensitivities of the land
surface model are interdependent and in some cases illustrate a physically plausible feedback process. The important predictors
of land surface response in a changing climate are the atmospheric temperature and downwelling longwave radiation. Scenarios
characterized by warming and drying produce a large relative response compared to warm, moist scenarios. The insensitivity
of the model to increases in precipitation and atmospheric humidity is expected to change in applications to coupled models,
since these parameters are also strongly implicated, through the representation of clouds, in the simulation of both longwave
and shortwave radiation.
Received: 27 March 2000 / Accepted: 11 September 2000 相似文献
4.
Ulrike Burkhardt 《Climate Dynamics》1995,11(5):299-305
A canonical correlation analysis is used to study the simulation of the relationship between small-scale precipitation patterns near the Alps and large-scale flow patterns by the ECHAM (ECMWF model, HAMburg version) climate model. The analysis is performed on a monthly mean time scale for the winter months of ECHAM1/T21, ECHAM3/T21 (improved model physics) and ECHAM3/T42 (increased resolution) simulations. The obtained patterns are compared with an identical analysis of observational data. The coarse structures of the observed relationships seem to be reasonably well simulated by the ECHAM3/T42 model version despite the simple shape of the model Alps (hereafter the model Alps), while the results for the ECHAM1/T21 and ECHAM3/T21 are not as good. This appears to be not only due to the increased resolution but also to the improved model physics, since some indication of the relationship can be found in the simulation of the ECHAM3/T21, but not in the simulation of the ECHAM1/T21 model version.Paper presented in session OA19/ST15, Simulation of climates using comprehensive global models at the XIX General Assembly of the EGS, Grenoble, 25–29 April 1994 相似文献
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Daily mean values of the Priestley-Taylor coefficient, ¯, are derived from a simple model of the daily growth of a convective boundary layer. For a particular control set of driving environmental variables, ¯ is related to the prescribed bulk surface resistance, rS by 1/¯ = 1/0 + mrS for parameters 0 and m. The dependence of the parameters 0 and m on weather is explored and a potential use of this linear relation to provide information about regional values of rS is indicated. 相似文献
9.
Abstract This study reports on the implementation of an interactive mixed‐layer/thermodynamic‐ice lake model coupled with the Canadian Regional Climate Model (CRCM). For this application the CRCM, which uses a grid mesh of 45 km on a polar stereographic projection, 10 vertical levels, and a timestep of 15 min, is nested with the second generation Canadian General Circulation Model (GCM) simulated output. A numerical simulation of the climate of eastern North America, including the Laurentian Great Lakes, is then performed in order to evaluate the coupled model. The lakes are represented by a “mixed layer” model to simulate the evolution of the surface water temperature, and a thermodynamic ice model to simulate evolution of the ice cover. The mixed‐layer depth is allowed to vary spatially. Lake‐ice leads are parametrized as a function of ice thickness based on observations. Results from a 5‐year integration show that the coupled CRCM/lake model is capable of simulating the seasonal evolution of surface temperature and ice cover in the Great Lakes. When compared with lake climatology, the simulated mean surface water temperature agrees within 0.12°C on average. The seasonal evolution of the lake‐ice cover is realistic but the model tends to underestimate the monthly mean ice concentration on average. The simulated winter lake‐induced precipitation is also shown, and snow accumulation patterns on downwind shores of the lakes are found to be realistic when compared with observations. 相似文献
10.
Thomas Prenosil 《Boundary-Layer Meteorology》1979,17(4):495-516
The atmospheric surface layer model of Lewellen and Teske (1973) is extended. Obvious discrepancies between model results and empirical data suggest the use of improved closure schemes for the non-diffusive parts of the pressure-velocity correlations in the Reynolds stress equations. Subsequently a time scale for the surface layer, which is based on vertical velocity fluctuations, is tested by means of the extended model. Finally the extended model is optimized by variation of the diffusion parameters, and an additional equation is introduced for the dissipation rate of Reynolds stresses. Investigations show that the normalized mean velocity and temperature gradients are verified by all model versions favorably, whereas the other turbulence variables % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqaqpepeea0xe9qqVa0l% b9peea0lb9Lq-JfrVkFHe9peea0dXdarVe0Fb9pgea0xa9W8qr0-vr% 0-viWZqaceaabiGaciaacaqabeaadaqaaqaaaOqaamaanaaabaGaam% yDaGqaciaa-DcacaWFGaGaamyDaiaa-DcaaaGaaiilaiaabccadaqd% aaqaaiabew8a1jaa-DcacaWFGaGaeqyXduNaa83jaaaacaqGSaGaae% iiamaanaaabaGaae4Daiaa-DcajaaqcaWFGaGccaqG3bGaa83jaaaa% caqGSaGaaeiiamaanaaabaGaamyDaiaa-DcajaaqcaWFGaGccaWFub% Gaa83jaaaaaaa!4DB4!\[\overline {u' u'} ,{\rm{ }}\overline {\upsilon ' \upsilon '} {\rm{, }}\overline {{\rm{w}}' {\rm{w}}'} {\rm{, }}\overline {u' T'} \] and % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqaqpepeea0xe9qqVa0l% b9peea0lb9Lq-JfrVkFHe9peea0dXdarVe0Fb9pgea0xa9W8qr0-vr% 0-viWZqaceaabiGaciaacaqabeaadaqaaqaaaOqaaGqaciaa-rfaca% WFNaqcaaKaa8hiaOGaa8hvaiaa-Dcaaaa!3BB8!\[T' T'\] cannot be simulated so easily. Complications especially arise in unstable temperature stratification. 相似文献
11.
Ng Jing Lin Abd Aziz Samsuzana Huang Yuk Feng Wayayok Aimrun Rowshon MK 《Theoretical and Applied Climatology》2018,133(1-2):489-509
Theoretical and Applied Climatology - A tropical country like Malaysia is characterized by intense localized precipitation with temperatures remaining relatively constant throughout the year. A... 相似文献
12.
Martin Claussen 《Boundary-Layer Meteorology》1985,33(3):233-243
From measured one-dimensional spectra of velocity and temperature variance, the universal functions of the Monin-Obukhov similarity theory are calculated for the range –2 z/L + 2. The calculations show good agreement with observations with the exception of a range –1 z/L 0 in which the function
m
, i.e., the nondimensional mean shear, is overestimated. This overestimation is shown to be caused by neglecting the spectral divergence of a vertical transport of turbulent kinetic energy. The integral of the spectral divergence over the entire wave number space is suggested to be negligibly small in comparison with production and dissipation of turbulent kinetic energy.Notation a,b,c
contants (see Equations (–4))
- Ci
constants i=u, v, w, (see Equation (5)
- kme,kmT
peak wave numbers of 3-d moel spectra of turbulent kinetic energy and of temperature variance, respectively
- kmi
peak wave numbers of 1-d spectra of velocity components i=u, v, w and of temperature fluctuations i=
- ksb, kc
characteristics wave numbers of energy-feeding by mechanical effects being modified by mean buoyancy, and of convective energy feeding, respectively
- L
Monin-Obukhov length
- % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiiYdd9qrFfea0dXdf9vqai-hEir8Ve% ea0de9qq-hbrpepeea0db9q8as0-LqLs-Jirpepeea0-as0Fb9pgea% 0lrP0xe9Fve9Fve9qapdbaqaaeGacaGaaiaabeqaamaabaabcaGcba% Gabeivayaaraaaaa!3C5B!\[{\rm{\bar T}}\]
difference of mean temperature and mean potential temperature
- T*
Monin-Obukhov temperature scale
-
velocity of mean flow in positive x-direction
- u*
friction velocity
- u, v, w
components of velocity fluctuations
- z
height above ground
-
von Kármanán constant
-
temperature fluctuation
- m
nondimensional mean shear
- H
nondimensional mean temperature gradient
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nondimensional rate of lolecular dissipation of turbulent kinetic energy
- D
nondimensional divergence of vertical transports of turbulent linetic energy 相似文献
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Steven Pawson Ulrike Langematz Arnold Meyer Peter Strauch Silke Leder Klaus Rose 《Climate Dynamics》1991,5(3):161-174
Mean fields from a perpetual January simulation of a GCM extending from the surface to 0.01 hPa (near 80 km) are compared to observations. The zonal mean temperature and wind fields correspond quite well with reality; the low stratosphere, especially in the polar night, is too cold, but warmer than in the original version of the model, with an upper boundary at 25 hPa. Mean fields at standard levels show that the major features of the troposphere are represented by the model, but rather over emphasised; the stratospheric winter polar vortex is too strong, too cold, and too barotropic; it resembles an `undisturbed' January rather than the climatology. Differences in the stationary eddy activity between the extended and orginal versions of the model are noted, and used to explain some differences between the two simulations.This paper was presented at the International Conference on Modelling of Global Climate Change and Variability, held in Hamburg 11–15 September 1989 under the auspices of the Meteorological Institute of the University of Hamburg and the Max Planck Institute für Meteorology. Guest Editor for these papers is Dr. L. Dümenil 相似文献
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Implementation of a Surface Runoff Model with Horton and Dunne Mechanisms into the Regional Climate Model RegCM_NCC 总被引：1，自引：0，他引：1
A surface runoff parameterization scheme that dynamically represents both Horton and Dunne runoff generation mechanisms within a model grid cell together with a consideration of the subgrid-scaie soil heterogeneity, is implemented into the National Climate Center regional climate model （RegCM_NCC）. The effects of the modified surface runoff scheme on RegCMANCC performance are tested with an abnormal heavy rainfall process which occurred in summer 1998. Simulated results show that the model with the original surface runoff scheme （noted as CTL） basically captures the spatial pattern of precipitation, circulation and land surface variables, but generally overestimates rainfall compared to observations. The model with the new surface runoff scheme （noted as NRM） reasonably reproduces the distribution pattern of various variables and effectively diminishes the excessive precipitation in the CTL. The processes involved in the improvement of NRM-simulated rainfall may be as follows： with the new surface runoff scheme, simulated surface runoff is larger, soil moisture and evaporation （latent heat flux） are decreased, the available water into the atmosphere is decreased; correspondingly, the atmosphere is drier and rainfall is decreased through various processes. Therefore, the implementation of the new runoff scheme into the RegCMANCC has a significant effect on results at not only the land surface, but also the overlying atmosphere. 相似文献
17.
The International Nusantara Stratification and Transport (INSTANT) program measured currents through multiple Indonesian Seas passages simultaneously over a three-year period (from January 2004 to December 2006). The Indonesian Seas region has presented numerous challenges for numerical modelers — the Indonesian Throughflow (ITF) must pass over shallow sills, into deep basins, and through narrow constrictions on its way from the Pacific to the Indian Ocean. As an important region in the global climate puzzle, a number of models have been used to try and best simulate this throughflow. In an attempt to validate our model, we present a comparison between the transports calculated from our model and those calculated from the INSTANT in situ measurements at five passages within the Indonesian Seas (Labani Channel, Lifamatola Passage, Lombok Strait, Ombai Strait, and Timor Passage). Our Princeton Ocean Model (POM) based regional Indonesian Seas model was originally developed to analyze the influence of bottom topography on the temperature and salinity distributions in the Indonesian seas region, to disclose the path of the South Pacific Water from the continuation of the New Guinea Coastal Current entering the region of interest up to the Lifamatola Passage, and to assess the role of the pressure head in driving the ITF and in determining its total transport. Previous studies found that this model reasonably represents the general long-term flow (seasons) through this region. The INSTANT transports were compared to the results of this regional model over multiple timescales. Overall trends are somewhat represented but changes on timescales shorter than seasonal (three months) and longer than annual were not considered in our model. Normal velocities through each passage during every season are plotted. Daily volume transports and transport-weighted temperature and salinity are plotted and seasonal averages are tabulated. 相似文献
18.
Jun Wei Paola Malanotte-Rizzoli Elfatih A. B. Eltahir Pengfei Xue Danya Xu 《Climate Dynamics》2014,43(5-6):1575-1594
Climatological high resolution coupled climate model simulations for the maritime continent have been carried out using the regional climate model (RegCM) version 3 and the finite volume coastal ocean model (FVCOM) specifically designed to resolve regions characterized by complex geometry and bathymetry. The RegCM3 boundary forcing is provided by the EMCWF-ERA40 re-analysis. FVCOM is embedded in the Global MITgcm which provides boundary forcing. The domain of the coupled regional model covers the entire South China Sea with its through-flow, the entire Indonesian archipelago with the Indonesian through-flow (ITF) and includes a large region in the western Pacific and eastern Indian oceans. The coupled model is able to provide stable and realistic climatological simulations for a specific decade of atmospheric–oceanic variables without flux correction. The major focus of this work is on oceanic properties. First, the coupled simulation is assessed against ocean-only simulations carried out under two different sets of air–sea heat fluxes. The first set, provided by the MITgcm, is proved to be grossly deficient as the heat fluxes are evaluated by a two-dimensional, zonally averaged atmosphere and the simulated SST have anomalous cold biases. Hence the MITgcm fluxes are discarded. The second set, the NCEP re-analysis heat fluxes, produces a climatological evolution of the SST with an average cold bias of ~?0.8 °C. The coupling eliminates the cold bias and the coupled SST evolution is in excellent agreement with the analogous evolution in the SODA re-analysis data. The detailed comparison of oceanic circulation properties with the International Nusantara Stratification and Transport observations shows that the coupled simulation produces the best estimate of the total ITF transport through the Makassar strait while the transports of three ocean-only simulations are all underestimated. The annual cycle of the transport is also very well reproduced. The coupling also considerably improves the vertical thermal structure of the Makassar cross section in the upper layer affected by the heat fluxes. On the other hand, the coupling is relatively ineffective in improving the precipitation fields even though the coupled simulation captures reasonably well the precipitation annual cycle at three land stations in different latitudes. 相似文献
19.
A model of the planetary boundary layer over a snow surface has been developed. It contains the vertical heat exchange processes due to radiation, conduction, and atmospheric turbulence. Parametrization of the boundary layer is based on similarity functions developed by Hoffert and Sud (1976), which involve a dimensionless variable, ζ, dependent on boundary-layer height and a localized Monin-Obukhov length. The model also contains the atmospheric surface layer and the snowpack itself, where snowmelt and snow evaporation are calculated. The results indicate a strong dependence of surface temperatures, especially at night, on the bursts of turbulence which result from the frictional damping of surface-layer winds during periods of high stability, as described by Businger (1973). The model also shows the cooling and drying effect of the snow on the atmosphere, which may be the mechanism for air mass transformation in sub-Arctic regions. 相似文献
20.
The erosion of a model stratospheric polar vortex in response to bottom boundary forcing is investigated numerically. Stripping of filaments of air from the polar vortex has been implicated in the occurrence of stratospheric sudden warmings (SSWs) but it is not understood in detail what factors determine the rate and amount of stripping. Here a shallow water vortex forced by topography is used to investigate the factors initiating stripping and whether this leads the vortex to undergo an SSW. It is found that the amplitude of topographic forcing must exceed some threshold (of order 200–450 m) in order for significant stripping to occur. For larger forcing amplitudes significant stripping occurs, but not as an instantaneous response to the forcing; rather, the forcing appears to initiate a process that ultimately results in stripping several tens of days later. There appears to be no simple quantitative relationship between the amount of mass stripped and the topography amplitude. However, at least over the early stages of the experiments, there is a good correlation between the amount of mass stripped and the global integral of wave activity, which may be interpreted as a measure of the accumulated topographic forcing. Finally there does not appear to be a simple correspondence between amount of mass stripped and the occurrence of an SSW. 相似文献