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Formation of the thermal-driven boundary jet in an f-plane mesoscale basin

Science china Earth sciences 2008年第1期51卷 152-160页

作者： FENG LiCheng1,2 & CHAO JiPing3,4 1 State Key Laboratory of Numerical Modeling for atmospheric Science and Geophysical Fluid Dynamics (lasg), institute of atmospheric physics, chinese academy of sciences, beijing 100029, china 2 Graduate University of the chinese academy of sciences, beijing 100049, china 3 National Marine Environment Forecast Center, beijing 100081, china 4 First institute of Oceanography, State Oceanic Administration, Qingdao 266061, china 1. State Key Laboratory of Numerical Modeling for atmospheric Science and Geophysical Fluid Dynamics (lasg) Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China 2. Graduate University of the chinese academy of sciences Beijing 100049 China 3. National Marine Environment Forecast Center Beijing 100081 China 4. First institute of Oceanography State Oceanic Administration Qingdao 266061 China

The paper adopts an f-plane quasi-geostrophic inertial model without linearization to investigate the perturbation temperature, boundary jet and upwelling (downwelling) in an idealized rectangular basin, under the consideration of west side friction layer and heat conservation. There is net heat input on the upper surface and equal quality heat dissipation on the west boundary, and without heat exchange on other boundaries, then the heat is conservation in the whole basin. Results show that there is thermal front due to denseness of the perturbation temperature in the west side boundary, the perturbation pressure and flow field are reversal on the upper layer and bottom layer. On the bottom layer, the west coastal current is northward, and the maximum perturbation pressure center is on the west, however, on the upper layer, the east coastal current is southward, and the maximum perturbation pressure center is on the east. There is strong vertical flow in narrow western boundary layer, and also in the central zone. The effect of different upper thermal forcings is also studied, and it can be concluded that there is always temperature denseness and boundary jet near the west boundary, and the appearance of flow field reversal, but the distribution of vertical flow is rather different.

关键词： boundary jet vertical flow thermal front thermal-driven heat conservation

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Mechanism of the Spring Persistent Rains over southeastern china

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Science china Earth sciences 2007年第1期50卷 130-144页

作者： WAN RiJin1,2,3 & WU GuoXiong1 1 State Key Laboratory of Numerical Modeling for atmospheric sciences and Geophysical Fluid Mechanicals (lasg), institute of atmospheric physics, chinese academy of sciences, beijing 100029, china 2 Guangdong Climate and Agrometeorology Center, Guangzhou 510080, china 3 Shanghai Typhoon institute of china Meterological Administration, Shanghai 200030, china 1. State Key Laboratory of Numerical Modeling for atmospheric sciences and Geophysical Fluid Mechanicals (lasg) Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China 2. Guangdong Climate and Agrometeorology Center Guangzhou 510080 China 3. Shanghai Typhoon institute of china Meterological Administration Shanghai 200030 China

The Spring Persistent Rains (SPR) in the areas to the south of middle and lower reaches of the Yangtze River or over southeastern china (SEC) is a unique synoptic and climatic phenomenon in East Asia. This study reveals a possible mechanism responsible for the climatic cause of SPR formation through climatic mean data analysis and sensitive numerical model experiments. SEC is located at the down-stream of the southwesterly velocity center (SWVC) which lies on the southeastern flank of the Tibetan Plateau (TP). As a result, there are strong southwesterly wind velocity convergence and moisture con-vergence over SEC. This is the immediate climatic cause of SPR formation. In spring, the seasonal evolution of the southwesterly velocity consists with the surface sensible heating over southeastern TP, indicating that the formation of SPR is related to not only the southwesterly wind of mechanical de-flected flow of TP, but also the southwesterly wind of thermal-forced cyclonic low circulation. Sensitive numerical experiments demonstrate that, without TP, both SWVC and the SPR rain belt will disappear. The southwesterly wind velocity increases almost linearly with the amount of the total diabatic heating with TP rising. Therefore, SWVC is the result of the mechanical forcing and thermal forcing of TP. All these strongly suggest that the presence of TP plays a primary role in the climatic formation of SPR.

关键词： SPR climatic cause of formation southwesterly Tibetan Plateau sensitive experiments.

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Research on the dry intrusion accompanying the low vortex precipitation

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Science china Earth sciences 2007年第9期50卷 1396-1408页

By employing the 6.7μm satellite vapor cloud images and NCEP/NCAR 1°×1° reanalysis datasets, the characteristics and mechanism of the dry intrusion, as well as its impacts on the low vortex precipita- tion at the Meiyu front are explored in this paper. It is found that the formation,development and main- tenance of the low vortex precipitation at the Meiyu front are closely related to the evolution of the dry intrusion. The dry intrusion is characterized by high potential vorticity (PV), low humidity and cold air. The dry intrusion exhibits as an obvious dark zone on vapor cloud images, an area in which atmos- pheric relative humidity is lower than 60%. However, the features of the dry intrusion on the vapor im- ages are clearer than that of the humidity field, for the former is the digital vapor cloud images with high temporal and spatial resolution, and it can be used to explore the finer characteristics of the develop- ment, evolution and supplement of the intrusion during the development of the low vortex. The dry intrusion impacts accompanying the low vortex precipitation at the Meiyu front come from all levels of the troposphere, with the strongest intrusion located at the upper troposphere. The dry and cold air intrudes the vicinity of the low vortex from the upper isentropic surface to the lower one, slanting eastward from lower to higher level. The low vortex precipitation region is usually situated in front of the dry intrusion where the relative humidity gradient is higher. The research also reveals that the mechanism of the dry intrusion is that the high potential vorticity descends from the upper troposphere to the lower level, therefore, the dry intrusion can be used as an important index of the high PV forcing. To the west of the low vortex precipitation, the upper level northerlies descend across the isentropic surface, then the dry cold advection can trigger the instable development in the mid-low troposphere. The dry intrusion enhances the low vort

关键词： Meiyu front, low vortex precipitation, dry intrusion, mechanisim, vapor image, potential vorticity, relative humidity

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The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking

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Science china Earth sciences 2007年第8期50卷 1266-1272页

作者： YAN BangLiang CMSR, institute of atmospheric physics, chinese academy of sciences, beijing 100029, china 1. CMSR Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking is ex-amined by using a mixed-mode model. The results show that the positive feedback process of the ef-fects of the seasonal variation of the upwelling mean on the Kelvin wave is the mechanism of the locking of the event mature phase to the end of the calendar year. The memory of the Rossby waves for the sign-shifting of the sea surface temperature anomaly from positive to negative 6 months before the cold peak time is the other mechanism of the locking of the La Nia event mature phase to the end of the calendar year. The results here are different from previous ones which suggest that the balance between cold and warm trends of sea surface temperature anomaly is the mechanism involved. The cold trend is caused by the upwelling Kelvin wave from upwelling Rossby wave reflected at the western boundary, excited by the westerly anomaly stress over the central Pacific and amplified by the seasonal variation of the coupled strength in its way propagating westward. The warm trend is caused by the Kelvin wave forced by the western wind stress over the middle and eastern equatorial Pacific. The cause of the differences is due to the opposite phase of the seasonal variation of the upwelling mean to that in the observation and an improper parameterization scheme for the effects of the seasonal varia-tion of the upwelling mean on the ENSO cycle in previous studies.

关键词： Kelvin wave Rossby wave interaction between atmosphere and sea positive feedback

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An improved δ-Eddington approximation

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chinese Science Bulletin 1999年第4期44卷 304-309页

作者： QIU Jinhuaninstitute of atmospheric physics , chinese academy of sciences , beijing 100029, china institute of atmospheric physics Chinese Academy of Sciences Beijing China

Based on an accuracy analysis of two-stream approximations, an improved δ-Eddington ap-proximation is developed. The approximation has much better accuracy than all exiting two-stream ap-proximations as the optical depth is less than unity. As the surface reflectance is zero and the opticaldepth is less than unity, errors in both transmission and reflection calculated by the present approxima-tion are more one time less than those by other two-stream approximations. In the case of aerosol opti-cal depth of<1, surface reflectance of < 0.6, solar zenith angle of < 78°and aerosol imaginary indexof < 0.05, transmission and reflection errors calculated by the improved δ-Eddington approximationare generally less than 3.5% and 2.6%, respectively. The errors are over 41% and one times lessthan those by Eddington or δ-Eddington.

关键词： radiation flux fractional factor of δ-function Eddington approximation.

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Prediction model for spring dust weather frequency in North china

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Science china Earth sciences 2008年第5期51卷 709-720页

作者： LANG XianMei Center for Disastrous Climate Research and Prediction, institute of atmospheric physics, chinese academy of sciences, beijing 100029, china Center for Disastrous Climate Research and Prediction Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

It is of great social and scientific importance and also very difficult to make reliable prediction for dust weather frequency (DWF) in North china. In this paper, the correlation between spring DWF in beijing and Tianjin observation stations, taken as examples in North china, and seasonally averaged surface air temperature, precipitation, Arctic Oscillation, Antarctic Oscillation, South Oscillation, near surface meridional wind and Eurasian westerly index is respectively calculated so as to construct a prediction model for spring DWF in North china by using these climatic factors. Two prediction models, i.e. model-I and model-II, are then set up respectively based on observed climate data and the 32-year (1970 -2001) extra-seasonal hindcast experiment data as reproduced by the nine-level atmospheric General Circulation Model developed at the institute of atmospheric physics (IAP9L-AGCM). It is indicated that the correlation coefficient between the observed and predicted DWF reaches 0.933 in the model-I, suggesting a high prediction skill one season ahead. The corresponding value is high up to 0.948 for the subsequent model-II, which involves synchronous spring climate data reproduced by the IAP9L-AGCM relative to the model-I. The model-II can not only make more precise prediction but also can bring forward the lead time of real-time prediction from the model-I’s one season to half year. At last, the real-time predictability of the two models is evaluated. It follows that both the models display high prediction skill for both the interannual variation and linear trend of spring DWF in North china, and each is also featured by different advantages. As for the model-II, the prediction skill is much higher than that of original approach by use of the IAP9L-AGCM alone. Therefore, the prediction idea put forward here should be popularized in other regions in china where dust weather occurs frequently.

关键词： spring dust weather frequency prediction model iap9l-agcm hindcast experiment real-time prediction

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The influence of tropical Indian Ocean warming on the Southern Hemispheric stratospheric polar vortex

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Science china Earth sciences 2009年第3期52卷 323-332页

作者： LI ShuangLin Nansen-Zhu International Research Centre, institute of atmospheric physics, chinese academy of sciences, beijing 100029, china Nansen-Zhu International Research Centre Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

During the past decades, concurrent with global warming, most of global oceans, particularly the tropical Indian Ocean, have become warmer. Meanwhile, the Southern Hemispheric stratospheric polar vortex (SPV) exhibits a deepening trend. Although previous modeling studies reveal that radiative cooling effect of ozone depletion plays a dominant role in causing the deepening of SPV, the simulated ozone-depletion-induced SPV deepening is stronger than the observed. This suggests that there must be other factors canceling a fraction of the influence of the ozone depletion. Whether the tropical Indian Ocean warming (IOW) is such a factor is unclear. This issue is addressed by conducting ensemble atmospheric general circulation model (AGCM) experiments. And one idealized IOW with the amplitude as the observed is prescribed to force four AGCMs. The results show that the IOW tends to warm the southern polar stratosphere, and thus weakens SPV in austral spring to summer. Hence, it offsets a fraction of the effect of the ozone depletion. This implies that global warming will favor ozone recovery, since a warmer southern polar stratosphere is un-beneficial for the formation of polar stratospheric clouds (PSCs), which is a key factor to ozone depletion chemical reactions.

关键词： tropical Indian Ocean warming Southern Hemispheric stratospheric polar vortex atmospheric general circulation model ensemble experiments planetary wave

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North Pacific sea ice cover, a predictor for the Western North Pacific typhoon frequency?

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Science china Earth sciences 2007年第8期50卷 1251-1257页

作者： FAN Ke institute of atmospheric physics, chinese academy of sciences, beijing 100029, china Department of atmospheric Science, Yun-nan University, Kunming 650091, china 1. institute of atmospheric physics Chinese Academy of Sciences Beijing 100029 China 2. Department of atmospheric Science Yunnan University Kunming 650091 China

The relationship between the sea ice cover in the North Pacific and the typhoon frequency has been studied in this paper. It follows that the index for the sea ice cover in the North Pacific (ISA) both in December-January-February (DJF) and in March-April-May (MAM) is negatively correlated with annual typhoon number over the western North Pacific (TNWNP) during 1965―2004, with correlation coeffi-cients of -0.42 and -0.49 respectively (above 99% significant level). Large sea ice cover in the North Pacific tends to decrease TNWNP. Positive ISA (MAM) is associated with the tropical circulation and SST anomalies in the North Pacific, which may lead to unfavorable dynamic and thermal conditions for typhoon genesis over WNP from June to October (JJASO). The variability of the atmospheric circula-tion over the North Pacific, associated with the ISA anomaly in MAM is connected to the tropical at-mospheric circulation variability in MAM via the teleconnection wave train. Besides, as the tropical circulation has strong seasonal persistency from the MAM to JJASO, thus, the ISA in MAM-related variability of the tropical atmospheric circulation as well as the SST can affect the typhoon activity over the western North Pacific.

关键词： typhoon sea ice cover North Pacific teleconnection

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Slow wave in barotropic atmosphere

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chinese Science Bulletin 2003年第S2期48卷 68-70页

作者： LIN Yihua lasg, institute of atmospheric Physies. chinese academy of sciences, beijing 100029, china chinese Acad Sci Inst Atmospher Phys LASG Beijing 100029 Peoples R China

In barotropic atmosphere, slow wave solution isobtained from linear primitive equation in the one dimensioncase; here the slow wave behaves very similarly to Rossbywave. The existence of the slow wave depends on the merid-ional structure of the basic flow instead of the ft effect. Thecharacter of the slow wave is almost the same as Rossbywave if the profile of basic flow is the convex function abouty.

关键词： linear barotropic atmosphere primitive equation slow wave meridional structure of basic flow.

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Sensitivity of sea ice and ocean simulations to sea ice salinity in a coupled global climate model

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Science china Earth sciences 2010年第6期53卷 911-918页

作者： LIU JiPing State Key Laboratory of Numerical Modeling for atmospheric sciences and Geophysical Fluid Dynamics, institute of atmospheric physics, chinese academy of sciences, beijing, 100029, china 1. State Key Laboratory of Numerical Modeling for atmospheric sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

The impacts of the spatiotemporal variations of sea ice salinity on sea ice and ocean characteristics have not been studied in detail, as the existing climate models neglect or misrepresent this process. To address this issue, this paper formulated a parameterization with more realistic sea ice salinity budget, and examined the sensitivity of sea ice and ocean simulations to the ice salinity variations and associated salt flux into the ocean using a coupled global climate model. Results show that the inclusion of such a parameterization leads to an increase and thickening of sea ice in the Eurasian Arctic and within the ice pack in the Antarctic circumpolar region, and a weakening of the North Atlantic Deep Water and a strengthening of the Antarctic Bottom Water. The atmospheric responses associated with the ice changes were also discussed.

关键词： sea ice salinity coupled global climate model Arctic and Antarctic

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