塔里木盆地东北缘一次强对流天气过程中的阵风锋特征研究

利用地面自动站逐小时观测、多普勒天气雷达及WRF模式高分辨率数值模拟,分析2016年7月塔里木盆地东北缘一次强对流天气过程中的阵风锋特征。结果表明,阵风锋前沿较强的辐合抬升运动不断触发多个对流单体,其中大部分单体与其后方的对流系统合并且进一步发展,使得强对流天气不断发展和维持。在对流系统快速发展阶段,阵风锋前沿水平风的垂直切变造成湿位涡的斜压分量显著增强,从而增强局地的条件对称不稳定,为对流系统的发展和维持提供了重要的不稳定能量。不稳定能量释放需要的锋生强迫作用主要是由阵风锋前方的辐合辐散项和倾斜项决定,而阵风锋前沿附近的水平形变项及其上方的非绝热加热项提供相对较弱的贡献。     

非平稳空间相关多点地震动合成方法研究

根据地震波的传播特点,在现有的非平稳空间相关多点地震动合成方法的基础上进行了改进。通过修正随机相位角,使生成的多点地震动在局部场地上具有收敛性。给出了未知和已知相位差谱统计规律2种情况下非平稳多点地震动的合成方法。进一步提出了基于实际地震纪录的空间相关多点地震动合成方法。这些方法可用于大尺度结构的多点输入分析。     

Paleoclimate studies and natural-resource management in the Murray-Darling Basin I: past,present and future climates

This paper provides an incisive review of paleoclimate science and its relevance to natural-resource management within the Murray-Darling Basin (MDB). The drought of 1997–2010 focussed scientific, public and media attention on intrinsic climate variability and the confounding effect of human activity, especially in terms of water-resource management. Many policy and research reviews make statements about future planning with little consideration of climate change and without useful actionable knowledge. In order to understand future climate changes, modellers need, and demand, better paleoclimate data to constrain their model projections. Here, we present an insight into a number of existing long-term paleoclimate studies relevant to the MDB. Past records of climate, in response to orbital forcing (glacial–interglacial cycles) are found within, and immediately outside, the MDB. High-resolution temperature records, spanning the last 10⁵ years, exist from floodplains and cave speleothems, as well as evidence from lakes and their associated lunettes. More recently, historical climate records show major changes in relation to El Niño–Southern Oscillation cycles and decadal shifts in rainfall regimes. A considerable body of research currently exists on the past climates of southeastern Australia but, this has not been collated and validated over large spatial scales. It is clear that a number of knowledge gaps still exist, and there is a pressing need for the establishment of new paleoclimatic research within the MDB catchment and within adjacent, sensitive catchments if past climate science is to fulfil its potential to provide policy-relevant information to natural-resource management into the future.     

Can Eddy Forcing be Responsible for the Spatial Structure of the Northern Hemisphere Annular Mode?

In order to study the origin of the spatial structure of the Northern Hemisphere Annular Mode (NAM),a linear stochastic model is constructed empirically from the output of a GCM run.Optimal stochastic forcing in terms of the maximum variance contribution,which may be potentially related to the maintenance of the NAM,is investigated.Theoretical analysis on the dominant non-modal response to the stochastic forcing shows that this dominance is jointly decided by the properties of forcing and the non-modal grow...     

MODULATION OF ATMOSPHERIC THERMAL AND MECHANICAL FORCINGS AND NUMERICAL MODELING OF MEAN MERIDIONAL CIRCULATION

Upon investigating the relative locations of internal and external forcing and the resultant mean meridional circulation,it was found that thermal forcing and mechanical forcing for the formation of atmospheric mean meridional circulation are modulated by a certain ratio.This ratio is determined by the inherent baroclinity,static stability and absolute vorticity of the atmosphere.By employing a parameterization scheme for radiative heating and condensation heating,together with the analysisdata of the European Center for Medium-range Weather Forecasts,the mean meridional circulation for January wassimulated numerically.It was found that latent heat release in the tropics may result in the formation of double-layeredHadley circulation,so do the eddy momentum transfer processes.On the other hand,mean meridional circulations in extra-tropics are mainly determined by external momentum forcing and atmospheric properties of eddy momentum andheat transfer.     

NUMERICAL EXPERIMENT OF THE INFLUENCES OF HEAT AND WIND STRESS ON THE EQUATORIAL OCEAN CIRCULATION*

A time-dependent linear model on the equatorial beta plane is developed in this paper.Its vertical structure consists of two active layers with equal density and temperature above the thermocline and a quasi-stationary layer with constant density below the thermocline.The results of nurnericat experiments show that the direct influence of heat on the equatorial ocean is much smaller than that of wind stress.Nevertheless,through the tropical ocean-atmosphere interaction,the change of wind stress resulting from the thermal forcing may set a determinant effect on the equilibrium and anomalous development of the ocean-almosphere circulation.     

短时间尺度周期性热力强迫下流型的低频振荡

本文在正压涡度方程中引进短时间尺度周期性热力强迫项。在一定的参数范围内,该强迫项可以引起环流指数准两至三周的低频振荡。     

NUMERICAL EXPERIMENT OF THE INFLUENCES OF HEAT AND WIND STRESS ON THE EQUATORIAL OCEAN CIRCULATION

A time-dependent linear model on the equatorial beta plane is developed in this paper.Its verticalstructure consists of two active layers with equal density and temperature above the thermocline and aquasi-stationary layer with constant density below the thermocline.The results of nurnericat experiments show that the direct influence of heat on the equatorial ocean ismuch smaller than that of wind stress.Nevertheless,through the tropical ocean-atmosphere interaction,the change of wind stress resulting from the thermal forcing may set a determinant effect on the equilibriumand anomalous development of the ocean-almosphere circulation.     

Numerical experiments on the generation of long ocean waves in coastal waters of the Buenos Aires province,Argentina

A numerical model (two horizontal dimensions, vertically integrated) is used to investigate the generation of long ocean waves, ranging from 20 min to almost 2 h, at Buenos Aires continental shelf. The domain includes the Río de la Plata estuary and the continental shelf together and extends from 33.5° to 40.5°S latitude, and from 51° to 63°W longitude. Sea-level oscillations are modeled by forcing with passage of atmospheric cold fronts and atmospheric gravity waves. Both forcing mechanisms, which have been present during high activity lapses of long ocean waves, are mathematically implemented. After several numerical simulations, it is concluded that the pressure and wind fields associated to cold fronts do not generate long ocean waves in the area, though they do produce disturbances with periods longer than the tidal ones. On the other hand, it is so concluded that atmospheric gravity waves are an effective mechanism to force long ocean waves. Results obtained show that generation of long ocean waves is highly sensitive depending on the propagation direction and the phase speed of the atmospheric gravity waves. The long ocean wave event detected during the large-amplitude gravity-wave event of 13 October 1985 is successfully simulated. Finally, all our results suggest that atmospheric gravity waves are a highly effective mechanism forcing for the generation of long ocean waves in Buenos Aires coastal waters.     

THE IMPACT OF RELATIVE HUMIDITY ON THE RADIATIVE PROPERTY AND RADIATIVE FORCING OF SULFATE AEROSOL

With the data of complex refractive index of sulfate aerosol,the radiative properties of theaerosol under 8 relative humidity conditions are calculated in this paper.By using the concentrationdistribution from two CTM models and LASG GOALS/AGCM,the radiative forcing due tohygroscopic sulfate aerosol is simulated.The results show that:(1)With the increase of relativehumidity,the mass extinction coefficiency factor decreases in the shortwave spectrum;singlescattering albedo keeps unchanged except for a little increase in longwave spectrum,andasymmetry factor increases in whole spectrum.(2)Larger differences occur in radiative forcingsimulated by using two CTM data,and the global mean forcing is—0.268 and—0.816 W/m~2,respectively.(3)When the impact of relative humidity on radiative property is taken into account,the distribution pattern of radiative forcing due to the wet particles is very similar to that of drysulfate,but the forcing value decreases by 60%.