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2002 Vol. 19, No. 5

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Application of Linear Thermodynamics to the Atmospheric System.Part Ⅱ: Exemplification of Linear Phenomenological Relations in the Atmospheric System
Hu Yinqiao
2002, 19(5): 767-776. doi: 10.1007/s00376-002-0043-7
The linear phenomenological relations in the atmospheric boundary layer are proved indirectly usingobservational facts to combine linear thermodynamic theory and similarity theory in the boundary layer.Furthermore, it is proved that the turbulent transport coefficients are in proportion to the correspondinglinear phenomenological coefficients. But the experimental facts show that the linear phenomenological rela-tions are not tenable in the atmospheric mixing layer because the turbalent transport process is an intensenon-linear process in the mixing layer. Hence the convection boundary layer is a thermodynamic state in anon-linear region far from the equilibrium state. The geostrophic wind is a special cross-coupling phenom-enon between the dynamic process and the thermodynamic process in the atmospheric system. It is a practi-cal exemplification ofa cross-coupling phenomenon in the atmospheric system.
The Features of Ozone Quasi-Biennial Oscillation in Tropical Stratosphere and Its Numerical Simulation
Chen Yuejuan, Zheng Bin, Zhang Hong
2002, 19(5): 777-793. doi: 10.1007/s00376-002-0044-6
The interannual variation of the vertical distribution of ozone in the tropical stratosphere and itsquasi-biennial oscillation (QBO) is analyzed using HALOE data. The results are compared with the windQBO. A numerical experiment is carried out to study the effects of wind QBO on the distribution, and varia-tion of ozone in the stratosphere by using the NCAR interactive chemical, dynamical, and radiativetwo-dimensional model (SOCRATES). Data analysis shows that the location of the maximum ozone mix-ing ratio in the stratosphere changes in the meridional and vertical directions, and assumes a quasi-biennialperiod. The meridional and vertical motion of the maximum mixing ratio leads to a QBO of column ozoneand its hemispheric asymmetry. The QBO of the location of the maximum is closely connected with the zon-al wind QBO. The data analysis also shows that in the tropical region, the phase of the QBO for ozone den-sity changes many times with height. Numerical simulation shows that the meridional circulation induced bythe wind QBO includes three pairs of cells in the stratosphere, which have hemispheric symmetry. Thetransport of ozone by the induced meridional circulation in various latitudes and heights is the main dynam-ic cause for the ozone QBO. Cells of the induced circulation in the middle stratosphere (25-35 km) play animportant role in producing the ozone QBO.
Effects of Turbulent Dispersion on the Wind Speed Profile in the Surface Layer
Liu Shikuo, Peng Weihong, Huang Feng, Chi Dongyan
2002, 19(5): 794-806. doi: 10.1007/s00376-002-0045-5
New Reynolds mean momentum equations including turbulent viscosity and dispersion are used to ana-lyze the vertical profile of wind speed in the surface layer. It is demonstrated that the wind profile of the sur-face layer including turbulent dispersion has a logarithmic modification on the classical power law. Underthe condition of unstable stratification, the effect of dispersion is stronger than under stable stratification.Under neutral stratification, the power law degenerates to the logarithmic law, but the yon Karman con-stant is replaced by k1 =(l+k/4)-1k, which can also be obtained by similarity theory.
Interannual and Decadal Variability of the North Pacific Blocking and Its Relationship to SST,Teleconnection and Storm Tracks
Huang Fei, Zhou Faxiu, Qian Xiaodan
2002, 19(5): 807-820. doi: 10.1007/s00376-002-0046-4
Climatological features of mid-latitude blocking occurring over the North Pacific Ocean during 52winters (December to February) of 1948/1949-1999/2000 are statistically analyzed based onNCEP/NCAR reanalysis data. Significant interannual variation with a period of about 3-7 years as wellas decadal variability is found by wavelet analysis and power spectrum analysis. A decreasing trend of the2-7 year bandscale-averaged variance occurs throughout the 52 years and an abrupt shift from a higherstate to a lower state during the 1970s is also found, which suggests an interdecadal variation of the NorthPacific blocking. The possible relationship between the variability of blocking and sea surface temperature(SST), storm tracks and teleconnection are shown using composite analysis. In strong blocking anomalywinter (SBW), the geopotential height anomaly at 500 hPa exhibits a typical PNA (Pacific-NorthAmerican)-like wave-train pattern in the North Pacific. The storm tracks, representing the activity of tran-sient eddies, extend northeastward to the western coast of North America along the mid latitudes of about40°-50°N, with the SST anomaly exhibiting a Pacific decadal oscillation (PDO) mode at mid-latitude and aLa Nina-like pattern along the equator. Contrasting features appear in weak blocking anomaly winter(WBW).
Seasonal Variation and Heat Preference of the South Asia High
Qian Yongfu, Zhang Qiong, Yao Yonghong, Zhang Xuehong
2002, 19(5): 821-836. doi: 10.1007/s00376-002-0047-3
By use of the NCEP/NCAR reanalysis data, the seasonal variation of the South Asia high (SAH) isanalyzed. The influences of temporal and spatial variations of the middle and upper level atmospheric tem-peratures, the visible heat sources, and the diabatic heating rates in the whole atmospheric column on theseasonal variation of the SAH are discussed. Results show that the SAH has two seasonal balancing modes,one of which is the land high in summer and the other the ocean high in winter. The land high itself can bedivided into two patterns as well, that is the Tibetan high and the Iranian high. Heating fields have impor-tant impacts on the seasonal variation of the SAH. The SAH is a warm high and its center has the propertyof heat preference, usually locating over or moving to an area with relatively larger heating rates. The annu-al cycle of the SAH is mainly controlled by the seasonal process of the latent and sensible heating in SouthAsia. Strong shortwave radiative heating in the north at high latitudes and over the Tibetan Plateau also hasan effects on the northward movement and maintenance of the SAH. The cooling effect of infrared radiationis an important cause in weakening the SAH.
A Data Analysis Study on the Evolution of the EI Ni?o/ La Ni?a Cycle
Chao Jiping, Yuan Shaoyu, Chao Qingchen, Tian Jiwei
2002, 19(5): 837-844. doi: 10.1007/s00376-002-0048-2
The curved surface of the maximum sea temperature anomaly (MSTA) was created from the JEDACsubsurface sea temperature anomaly data at the tropical Pacific between 1955 and 2000. It is quite similar tothe depth distribution of the 20°C isotherm, which is usually the replacement of thermocline. From the dis-tribution and moving trajectory of positive or negative sea temperature anomalies (STA) on the curved sur-face we analyzed all the El Nino and La Nina events since the later 1960s. Based on the analyses we foundthat, using the subsurface warm pool as the beginning point, the warm or cold signal propagates initiallyeastward and upward along the equatorial curved surface of MSTA to the eastern Pacific and stays thereseveral months and then to turn north, usually moving westward near 10°N to western Pacific and finallypropagates southward to return to warm pool to form an off-equator closed circuil. It takes about 2 to 4years for the temperature anomaly to move around the cycle. If the STA of warm (cold) water is strongenough, there will be two successive El Nino (La Nina) events during the period of 2 to 4 years. Sometime, itbecomes weak in motion due to the unsuitable oceanic or atmospheric condition. This kind process may notbe considered as an El Nino ( La Nina) event, but the moving trajectory of warm (cold) water can still berecognized. Because of the alternate between warm and cold water around the circuits, the positive(negative) anomaly signal in equatorial western Pacific coexists with negative (positive) anomaly signal near10 N in eastern Pacific before the outbreak of El Nino (La Nina) event. The signals move in the opposite di-rections. So it appears as El Nino (La Nina) in equator at 2-4 years intervals. The paper also analyzed sev-eral exceptional cases and discussed the effect and importance of oceanic circulation in the evolution of ElNino/La Nina event.
Energetics of Geostrophic Adjustment in Rotating Flow
Fang Juan, Wu Rongsheng
2002, 19(5): 845-854. doi: 10.1007/s00376-002-0049-1
Energetics of geostrophic adjustment in rotating flow is examined in detail with a linear shallow watermodel. The initial unbalanced flow considered first falls under two classes. The first is similar to thatadopted by Gill and is here referred to as a mass imbalance model, for the flow is initially motionless butwith a sea surface displacement. The other is the same as that considered by Rossby and is referred to as amomentum imbalance model since there is only a velocity perturbation in the initial field. The significantfeature of the energetics of geostrophic adjustment for the above two extreme models is that although theenergy conversion ratio has a large case-to-case variability for different initial conditions, its value isbounded below by 0 and above by 1/2. Based on the discussion of the above extreme models, the energeticsofadjustment for an arbitnary initial condition is investigated. It is found that the characteristics of the ener-getics of geostrophic adjustment mentioned above are also applicable to adjustment of the general unbal-anced flow under the condition that the energy conversion ratio is redefined as the conversion ratio betweenthe change of kinetic energy and potential energy of the deviational fields.
An Observational Study on the Vertical Distribution and Synoptic Variation of Ozone in the Arctic
Zou Han, Zhou Libo, Jian Yongxiao, Liu Yu
2002, 19(5): 855-862. doi: 10.1007/s00376-002-0050-8
Arctic ozone is important to the Arctic climate and environment system. Studying the ozone distribu-tion and variation is helpful for understanding the Arctic climate and environment and their impact on theglobal system, and for numerically forecasting climate and environment change. The Chinese Arctic Re-search Expedition 1999 made an ozone observation program possible over the Chukchi Sea in the ArcticOcean. Ozone soundings on board the Chinese icebreaker "Xuelong" (at 75°N, 160°W, 18-24 August 1999)made high-resolution vertical atmospheric structure and ozone distribution data available for studyingozone variation on a synoptic scale. Analysis of the observational data, the TOMS total ozone, and NCEPcirculation, shows that the atmospheric ozone amount experienced a high-low-high variation withlow-high-low tropopause altitude. The study shows a close relationship between the total ozone and theozone below 13 km, while the variation in the maximum concentration at about 20 km does not show any relationship to the column ozone. A weak-strong-weak southwesterly pattern in the 500 hPa synoptic systemmay be responsible for a low ozone advection during this ozone variation.
Application of the Artificial Compression Method to the Simulation of Two-Dimensional Frontogenesis
Yang Hongwei, Wang Bin, Ji Zhongzhen
2002, 19(5): 863-869. doi: 10.1007/s00376-002-0051-7
The artificial compression method (ACM) that is generally used to capture the contact discontinuity innonviscous flows is used here in the simulation of quasi-geostrophic ideal frontogenesis in two dimensions.A comparison is made among the result of the ACM, the simulation result of Cullen, and the exact solutionof the semi-geostrophic equations. The simulated front in this paper is more prominent than Cullen's and ismuch closer to the exact solution.
Initiation Mechanism of Meso-β Scale Convective Systems
Peng Jiayi, Wu Rongsheng, Wang Yuan
2002, 19(5): 870-884. doi: 10.1007/s00376-002-0052-6
With the aid of the Penn State-NCAR MM5 model, the initiation mechanism of meso-β scaleconvective systems (MCS) is investigated on the basis of simulation of the temporal and spatialthermodynamic structure of the MCS that occurred in Wuhan, Hubei, China and its surrounding area on 21July 1998. Using the PV inversion method, comparisons among the upper-, middle-, and low-leveltropospheric potential vorticity (PV) perturbations, as well as their effects on the initiation of MCS, indicatethat the low-level tropospheric PV perturbations play an important role in the triggering of MCS. Furtheranalysis reveals that the interaction between the southwest low-level jet and the gravity-inertia wave indeedinitiates MCS in the conditionally unstable ambient atmosphere.
Mechanism of Thermal Features over the Indo-China Peninsula and Possible Effects on the Onset of the South China Sea Monsoon
Zhang Yaocun, Qian Yongfu
2002, 19(5): 885-900. doi: 10.1007/s00376-002-0053-5
The thermal characteristics during the South China Sea (SCS) summer monsoon onset period near theIndo-China Peninsula are analyzed by using the South China Sea Monsoon Experiment (SCSMEX)reanalysis data from I May to 31 August 1998 and the NCEP/NCAR pentad-mean reanalysis data fromJanuary 1980 to December 1995. The possible relationships between the anomaly of thermal features nearthe Indo-China Peninsula and the SCS monsoon onset are investigated, and the mechanism causing theSCS summer monsoon onset is also discussed. Results from the 1998 SCSMEX reanalysis data show thatthere exists a strong persistent surface sensible heating near the Indo-China Peninsula prior to the SCSmonsoon onset, which has apparent low frequency oscillation features. This sensible heating leads to awarmer center in the lower atmosphere near the Indo-China Peninsula and strong local horizontal tempera-ture and geopotential height gradients which are favorable to strengthening the southwest wind over theIndo-China Peninsula. It is also found that stronger convergent winds at lower levels and stronger divergentwinds at high levels appear, which provide a favorable configuration for the development of vertical motion,enhancement of precipitation, and onset of the SCS monsoon. These results can be verified by analysis of themulti-year mean data. Additionally, it is found that the temperature at 850 hPa increases more rapidly overthe Indo-China Peninsula than the South China Sea prior to the SCS monsoon onset, which leads to astrengthening of the temperature difference between the Indo-China Peninsula and the South China Sea.Moreover, results from the analysis of the Iongitudinal temperature and geopotential height differencesshow that the eastern retreat of the subtropical high over the Indo-China Peninsula during the period ofSCS monsoon onset is associated with the temperature increase over the Indo-China Peninsula and theeastern extension of low trough over the Bay of Bengal.
Thermal Effects of the Tibetan Plateau on Rossby Waves from the Diabatic Quasi-Geostrophic Equations of Motion
Li Liming, Huang Feng, Chi Dongyan, Liu Shikuo, Wang Zhanggui
2002, 19(5): 901-913. doi: 10.1007/s00376-002-0054-4
From the diabatic quasi-geostrophic equations of motion, the authors analyze the characteristics ofdiabatic Rossby waves including the thermal effects of the Tibetan Plateau. When the basic zonal flow isbarotropic, it is demonstrated that the cooling of the Tibetan Plateau in winter not only facilitates themeridional propagation of Rossby waves but is an important driving mechanism of the intraseasonaloscillations in middle and high latitudes. When the basic zonal flow is baroclinic, it is found that the coolingof the Tibetan Plateau in winter facilitates the instability of Rossby waves, while in summer there is athreshold for the influence of the heating of the Tibetan Plateau on the stability of Rossby waves.
Interannual and Interdecadal Variability of Winter Precipitation over China in Relation to Global Sea Level Pressure Anomalies
Jianjun Xu, Johnny C. L. Chan
2002, 19(5): 914-926. doi: 10.1007/s00376-002-0055-3
Based on the method of rotated principal component (RPC) analysis and wavelet transforms, the win-ter precipitation from 36 stations over China for the period 1881-1993 is examined. The results show thatthe three leading space-time modes correspond, in sequence, to winter rainfall anomalies over the reaches ofthe Yangtze River, the bend of the Yellow River, and the northeastern region of China. The three modes ex-hibit interannual oscillations with quasi-biennial and 8-year periods as well as interdecadal oscillationswith 16- and 32-year periods. The interannual oscillation (< 10 years) occurs in phase over the differentareas, and its maximum amplitude migrates northward considerably with prominent interdecadal variations.However, the interdecadal oscillations (10-32 years) are out of phase over the different regions, and theamplitude variations have the characteristics of stationary waves.The rainfall anomalies appear to be closely re lated to the anti-phase changes of mean sea-level pres-sure (SLP) over the Asian mainland and the North Pacific. When the SLP rises over the North Pacific anddecreases over the Asian mainland, the precipitation over East China increases noticeably. The linkage be-tween the rainfall over China and the SLP anomalies apparently results from the strength of the East Asianwinter monsoon and its associated temperature and moisture advection.
Changes of Extreme Events in Regional Climate Simulations over East Asia
Gao Xuejie, Zhao Zongci, Filippo Giorgi
2002, 19(5): 927-942. doi: 10.1007/s00376-002-0056-2
Changes of extreme events due to greenhouse effects (2×CO2) over East Asia, with a focus on theChina region as simulated by a regional climate model (RegCM2), are investigated. The model is nested to aglobal coupled ocean-atmosphere model (CSIRO R21 L9 AOGCM). Analysis of the control run of the re-gional model indicates that it can reproduce well the extreme events in China. Statistically significantchanges of the events are analyzed. Results show that both daily maximum and daily minimum temperatureincrease in 2×CO2 conditions, while the diurnal temperature range decreases. The number of hot spell daysincreases while the number of cold spell days decreases. The number of rainy days and heavy rain days in-creases over some sub-regions of China. The 2×CO2 conditions also cause some changes in the tropicalstorms affecting China.
Typhoon Impacts on China's Precipitation during 1957-1996
Ren Fumin, Byron Gleason, David Easterling
2002, 19(5): 943-952. doi: 10.1007/s00376-002-0057-1
Tropical Cyclone (TC) activity is an important feature of China's climate that can have important im-pacts on precipitation and can cause extensive property damage. In particular, precipitation from TCs con-tributes a significant portion of overall precipitation. This study deals with typhoons that influence Chinaand focuses on their impact on China's precipitation. Four aspects are examined in this research. Firstly, thestudy of influencing typhoon frequency reveals that the main season that typhoons affect China is from Mayto November, especially between July and September. The frequency of influencing typhoons was steadyduring the past 40 years. Secondly, inspection of the climatology of station typhoon precipitation shows thatHainan and the southeastern coastalmost regions are most frequently affected by typhoons, and most of theregions south of the Yangtze River are affected by typhoons each year. Meanwhile, during 1957-1996, mostof the typhoon-influenced regions show decreasing trends in typhoon precipitation but only the trends insouthern Northeast China are significant. Thirdly, examination of the typhoon cases shows that there existsa significant linear relationship between the precipitation volume and impacted area. Finally, study of varia-tions of typhoon impacts on China's precipitation suggests that there exists a decreasing trend in the contri-bution of typhoon precipitation to overall precipitation, while total annual volume of typhoon precipitationdecreases significantly during the period.