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Evolution of desertification in a two-dimensional energy balance model coupled with thermodynamics and dynamics

Science china Earth Sciences 2010年第11期53卷 1726-1733页

作者： chao jiping1,2 & li yaokun3,4 1national marine environmental forecasting center, beijing 100081, china 2First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, china 3State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, beijing 100029, china 4Graduate University of Chinese Academy of Sciences, beijing 100049, china national marine environmental forecasting center Beijing China First Institute of Oceanography State Oceanic Administration Qingdao China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Graduate University of Chinese Academy of Sciences Beijing China

The relationship between desert evolution and change in albedo has been investigated quasi-analytically using a zonal mean two-dimensional energy balance model which considers the radiation transmission process due to thermodynamics and bound- ary layer movement caused by kinetics. A climate state including temperature, zonal wind, meridional wind and vertical wind can be simulated according to the current zonal distribution of albedo. Given desert distribution, characterized by the value and distribution of albedo, the response of climate on albedo has been studied to analyze the evolution of desert climate. One significant result is that the simple model can reproduce mean meridional circulation. Another result indicates that climate corresponds to two equilibria. This happens when the junction temperature between vegetation and desert is higher than a certain critical value. As for the first equilibrium, the desert belt is predicted to move southward in the northern hemisphere with the increasing values of albedo, which corresponds to the current trend of climate change. For the second equilibrium, vegetation will expand northward with increasing values of albedo, which would indicate a narrowing of the desert belt. In order to determine if the two equilibria exist, new physical models are needed.

关键词： two-dimensional energy balance model desertification two equilibria

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A two-dimensional energy balance climate model on Mars

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Earth and Planetary Physics 2022年第3期6卷 284-293页

作者： yaokun li jiping chao College of Global Change and Earth System Science Beijing Normal UniversityBeijing 100875China national marine environmental forecasting center Beijing 100081China

A two-dimensional energy balance climate model has been built to investigate the climate on *** model takes into account the balance among solar radiation,longwave radiation,and energy transmission and can be solved analytically by Legendre *** the parameters for thermal diffusion and radiation processes being properly specified,the model can simulate a reasonable surface atmospheric temperature distribution but not a very perfect vertical atmospheric temperature distribution compared with numerical results,such as those from the Mars Climate *** varying solar radiation in a Martian year,the model can simulate the seasonal variation of the air temperature on *** increasing dust content,the Martian atmosphere gradually ***,the warming is insignificant in the cold and warm scenarios,in which the dust mixing ratio varies moderately,whereas the warming is significant in the storm scenario,in which the dust mixing ratio increases *** an increasing albedo value of either the polar cap or the non-ice region,Mars gradually *** mean surface atmospheric temperature decreases moderately with an increasing polar ice albedo,whereas it increases dramatically with an increasing non-ice *** increase occurs because the planetary albedo of the ice regions is smaller than that of the non-ice region.

关键词： Mars energy balance climate model solar radiation dust surface albedo

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Variations in Amplitudes and Wave Energy along the Energy Dispersion Paths for Rossby Waves in the Quasigeostrophic Barotropic Model

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Advances in Atmospheric Sciences 2022年第6期39卷 876-888页

作者： yaokun li jiping chao Yanyan KANG College of Global Change and Earth System Science Beijing Normal UniversityBeijing 100875China national marine environmental forecasting center Beijing 100081China beijing Meteorological Observatory Beijing 100089China

Variations in wave energy and amplitude for Rossby waves are investigated by solving the wave energy equation for the quasigeostrophic barotropic potential vorticity *** results suggest that compared with rays in the nondivergent barotropic model,rays in the divergent model can have enhanced meridional and zonal propagation,accompanied by a more dramatic variability in both wave energy and amplitude,which is caused by introducing the divergence effect of the free surface in the quasigeostrophic *** rays propagating in a region enclosed by a turning latitude and a critical latitude,the wave energy approaches the maximum value inside the region,while the amplitude approaches the maximum at the turning *** can develop when both the wave energy and amplitude *** rays propagating in a region enclosed by two turning latitudes,the wave energy approaches the minimum value at one turning latitude and the maximum value at the other latitude,while the total wavenumber approaches the maximum value inside the *** resulting amplitude increases if the total wavenumber decreases or the wave energy increases more significantly and decreases if the total wavenumber increases or the wave energy decreases more *** matched roles of the energy from the basic flow and the divergence of the group velocity contribute to the slightly oscillating wave energy,which causes a slightly oscillating amplitude as well as the slightly oscillating total wavenumber.

关键词： Rossby waves quasigeostrophic barotropic model energy dispersion wave energy amplitude

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Variations in Wave Energy and Amplitudes along the Energy Dispersion Paths of Nonstationary Barotropic Rossby Waves

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Advances in Atmospheric Sciences 2021年第1期38卷 49-64页

The variations in the wave energy and the amplitude along the energy dispersion paths of the barotropic Rossby waves in zonally symmetric basic flow are studied by solving the wave energy equation,which expresses that the wave energy variability is determined by the divergence of the group velocity and the energy budget from the basic *** results suggest that both the wave energy and the amplitude of a leading wave increase significantly in the propagating region that is located south of the jet axis and enclosed by a southern critical line and a northern turning *** leading wave gains the barotropic energy from the basic flow by eddy *** amplitude continuously climbs up a peak at the turning latitude due to increasing wave energy and enlarging horizontal scale(shrinking total wavenumber).Both the wave energy and the amplitude eventually decrease when the trailing wave continuously approaches southward to the critical *** trailing wave decays and its energy is continuously absorbed by the basic ***,both the wave energy and the amplitude oscillate with a limited range in the propagating region that is located near the jet axis and enclosed by two turning *** the leading and trailing waves neither develop nor decay *** jet works as a waveguide to allow the waves to propagate a long distance.

关键词： barotropic Rossby waves energy dispersion wave ray theory wave energy amplitude

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Two equilibria of the Antarctic Circumpolar Current and its associated Meridional Overturning Circulation

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Science china Earth Sciences 2012年第11期55卷 315-322页

作者： chao jiping li yaokun national marine environmental forecasting center Beijing 100081China First Institute of Oceanography State Oceanic AdministrationQingdao 266061China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Graduate University of Chinese Academy of Sciences Beijing 100049China

The Antarctic Circumpolar Current (ACC) and its associated Meridional Overturning Circulation (MOC) is investigated through a nonlinear inertia theory model, which consists of two layers--an upper Ekman layer driven mainly by sea surface wind stress and a lower thermocline controlled by ideal fluid nonlinear equations which can be solved by identifying the form of the arbitrary functions. The results show that the thermocline has a two-equilibrium solution though given the same Ekman layer condition. Compared to the first equilibrium, the second one has a heavier intensity and deeper circulation, which seems more consistent with the existing data.

关键词： Antarctic Circumpolar Current Meridional Overturning Circulation inertia theory two equilibria

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The dynamical evolution theory of the isolated oasis system

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Science china Earth Sciences 2015年第3期58卷 436-447页

作者： li yaokun chao jiping College of Global Change and Earth System Science Beijing Normal University national marine environmental forecasting center

Assume that an oasis and its surrounding desert consist of an isolated system without mass and energy exchange with the outer *** characteristics of oasis evolution have been explored under the condition of system energy *** results show that oasis evolves with two equilibrium *** first equilibrium suggests a stable expansive and an unstable degraded oasis whereas the second equilibrium indicates a stable shrink and an unstable increase of the oasis *** one equilibrium state is unstable,the components of the isolated system(oasis and desert) would tend to be no energy exchange and they each reach to energy balance *** would maintain its initial area in this *** analyses point out that the two equilibrium states have completely different *** the first equilibrium state,a higher vegetation albedo,lower soil albedo and larger canopy resistance,and direr soil both contribute to the oasis area expansion,accompanying an excessive large desert soil and vegetation canopy temperature difference(SCTD).In the second equilibrium state,however,a lower vegetation albedo,higher soil albedo and small canopy resistance,and wetter soil benefit the oasis area to stay near its initial value,following a moderate *** convergent trajectories of the initial values in phase space are influenced by the separatrices of the equilibrium *** temperature is an advantage factor for initial values convergent to the oasis expansion solution.

关键词： energy conservation oasis desert two equilibrium states

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A numerical study of the effect of the marginal sea on coastal upwelling in a non-linear inertial model

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Science china Earth Sciences 2014年第11期57卷 2587-2596页

作者： chao jiping KANG YanYan li JianPing national marine environmental forecasting center LASG Institute of Atmospheric Physics Chinese Academy of Sciences College of Earth Sciences University of Chinese Academy of Sciences

Inertia theory and the finite element method are used to investigate the effect of marginal seas on coastal upwelling. In contrast to much previous research on wind-driven upwelling, this paper does not consider localized wind effects, but focuses instead on temperature stratification, the slope of the continental shelf, and the background flow field. Finite element method, which is both faster and more robust than finite difference method in solving problems with complex boundary conditions, was developed to solve the partial differential equations that govern coastal upwelling. Our results demonstrate that the environment of the marginal sea plays an important role in coastal upwelling. First, the background flow at the outer boundary is the main driving force of upwelling. As the background flow strengthens, the overall velocity of cross-shelf flow increases and the horizontal scale of the upwelling front widens, and this is accompanied by the movement of the upwelling front further offshore. Second, temperature stratification determines the direction of cross-shelf flows, with strong stratification favoring a narrow and intense upwelling zone. Third, the slope of the continental shelf plays an important role in controlling the intensity of upwelling and the height that upwelling may reach: the steeper the slope, the lower height of the upwelling. An additional phenomenon that should be noted is upwelling separation, which occurs even without a local wind force in the nonlinear model.

关键词： coastal upwelling inertia theory Finite Element Method (FEM)

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