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1999 Vol. 16, No. 4

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Discrete Spectra and Continuous Spectrum of the Barotropic Quasi-Geostrophic Model-A Calculation of Meteorological Data
Zhang Minghua, Zeng Qingcun
1999, 16(4): 487-506. doi: 10.1007/s00376-999-0026-z
Atmospheric disturbances at 300 hpa are decomposed into normal modes, referred as discrete-spectrum disturbances which can propagate freely in the observed zonal mean flow, and non-modal transient disturbances, referred as continuous-spectrum disturbances which are continuously sheared and eventually absorbed by the zonal flow. It is shown that normal modes represent only a small fraction of the observed atmospheric disturbances, while continuous-spec-trum disturbances represent the majority of observed disturbances, even when the basic flow is unstable. Daily variabilities of the observed continuous-spectrum disturbances are presented. They are shown to follow the results of wave-packet theory. Calculations suggest that there are abundant sources to excite continuous-spectrum disturbances in the atmosphere.
Retrieval of Tropospheric CO Profiles Using Correlation Radiometer. II: Effects of Other Gases and the Retrieval in Cloudy Atmosphere
Wu Beiying, John Gille
1999, 16(4): 507-522. doi: 10.1007/s00376-999-0027-y
The effects of methane, ozone, water vapor and nitrous oxide on the retrieval of tropospheric CO profiles using correlation radiometer have been assessed. The scheme of the retrieval in the presence of solid clouds have been proposed. The effect of methane and nitrous oxide can be well accounted by their mean profile, and that of ozone can be represented by a typical middle latitude ozone profile, while for water vapor, less than 50% uncertainty is required. With the assumption of blackbody for cloud surface, the CO profile may be retrieved for low and middle solid clouds. However, the retrieval of CO profile will lose quality for high clouds.
Dynamic Features and Maintenance Mechanism of Asian Summer Monsoon Subsystem
Xu Jianjun, Wu Guoxiong
1999, 16(4): 523-536. doi: 10.1007/s00376-999-0028-x
In the context of the dissociation of vertical shear flow and tropospheric mean flow based on 1980-1996 NCEP / NCAR re-analysis, study is undertaken of the barotropic and baroclinic de-velopment characteristics and kinetic energy maintenance mechanisms of Asian summer monsoon. Evidence suggests that the monsoon activity is marked by noticeable baroclinicity in three active regions of different dynamical characteristics, located in India, East Asian tropics and subtropics, respectively, with greatly differing maintenance mechanisms of barotropic / baroclinic kinetic en-ergy.
Diagnostic Study on Seasonality and Interannual Variability of Wind Field
Xue Feng, Zeng Qingcun
1999, 16(4): 537-543. doi: 10.1007/s00376-999-0029-9
Based on NCEP / NCAR reanalysis data during 1980-1994, seasonally and interannual va-riability of the horizontal wind field are studied. It is shown that: (1) In the lower troposphere, there exist regions with maximum of seasonality in the tropics, the subtropics and high latitudes, which is called the tropical, subtropical and temperate-frigid monsoon region respectively. In the upper troposphere, the subtropical monsoon combines with the tropical monsoon as a nonseparably planetary monsoon system. In the stratosphere, there is a belt with very large seasonality in each hemisphere caused by the inversely seasonal circulation and by the establish-ment and collapse of the night jet. (2) Seasonal variation of the large-scale monsoon may generally be attributed to that of the zonal wind, however, seasonal variation of the meridional wind is of great importance in East Asian monsoon region. (3) In monsoon region, interannual variability of the atmospheric general circulation is closely related to seasonal variation of monsoon, while in the tropical Pacific, it may considerably be influenced by the external factors such as sea surface tem-perature (SST) anomalies associated with El Nino or La Nina event. Moreover, interannual variability undergoes a pronounced annual cycle.
The Study on the Interannual Variation and the Mechanism of the South China Sea Monsoon
Jiang Jing, Qian Yongfu
1999, 16(4): 544-558. doi: 10.1007/s00376-999-0030-3
By using the USA NCAR / NCEP reanalysis data, the characteristics of climatic elements and the tem-poral and spatial structures of precipitation in the strong and weak years of the SCS monsoon are analyzed, the mechanism of the interannual variation of the SCS monsoon is discussed. It is found that the climatic el-ements in SCS have great differences, and there are great differences in the spatial and temporal structures of the precipitation anomalies between the strong and weak monsoon years. The variation of climatic ele-ments in the south of Indochina Peninsula in April is a good index of the strength of the SCS monsoon. There is a good connection between the SCS monsoon and the sea surface temperature. The SCS monsoon is weak in the EL Nino years, and strong in the La Nina years. The strength of the SCS monsoon depends on the local heating differences between the eastern continent of China and the western Pacific. It depends on the intensity and the position of the western Pacific Subtropical High. The western Pacific Subtropical High is weak and eastward in the strong monsoon years, and the case is reversed in the weak monsoon years.
Subtropical High Anomalies over the Western Pacific and Its Relations to the Asian Monsoon and SST Anomaly
Sun Shuqing, Ying Ming
1999, 16(4): 559-568. doi: 10.1007/s00376-999-0031-2
Using the data of 500 hPa geopotential height from 1951 to 1995, SST roughly in the same period and OLR data from 1974 to 1994, the relation between the anomalies of subtropical high (STH for short) and the tropical circulations including the Asian monsoon as well as the convective activity are studied。 In older to study the physical process of the air-sea interaction related to STH anomaly, the correlation of STH with SST at various sea areas, lagged and simultaneous, has been calculated. Comparing the difference of OLR, wind fields, vertical circulations and SST anomalies in the strong and weak STH, we investigate the characteristics of global circulations and the SST distributions related to the anomalous STH at the western Pacific both in winter and summer. Much attention has been paid to the study of the air-sea interaction and the relationship between the East Asian monsoon and the STH in the western Pacific. A special vertical circulation, related to the STH anomalies is found, which connects the monsoon current to the west and the vertical flow influenced by the SST anomaly in the tropical eastern Pacific.
Nonlinear Stability Analysis of the Zonal Flows at Middle and High Latitudes
Mu Mu, Wu Yonghui, Tang Mozhi, Liu Haiyan
1999, 16(4): 569-580. doi: 10.1007/s00376-999-0032-1
An attempt has been made to apply Arnol’d type nonlinear stability criteria to the diagnostic study of the persistence (stability) or breakdown (instability) of the atmospheric flows. In the case of the blocking high, the cut-off low and the zonal flow, the relationships of the geostrophic stream function versus the po-tential vorticity of the observed atmosphere are analyzed, which indicates that Arnol'd second type nonlinear stability theorem is more relevant to the observed atmosphere than the first one. For both the sta-ble and unstable zonal flows, Arnol’d second type nonlinear stability criteria are applied to the diagnosis. The primary results show that our analyses correspond well to the evolution of the atmospheric motions. The synoptically stable zonal flows satisfy Arnol'd second type nonlinear stability criteria; while the synoptically unstable ones violate the nonlinear stability criteria.
Modeling N2O Emissions from Agricultural Fields in Southeast China
Gou Ji, Zheng Xunhua, Wang Mingxing, Li Changsheng
1999, 16(4): 581-592. doi: 10.1007/s00376-999-0033-0
DNDC, a rainfall-driven and process-oriented model of soil carbon and nitrogen biogeochemistry, is applied to simulate the nitrous oxide emissions from agricultural ecosystem in Southeast China. We simulated the soil N2O emission during a whole rice-wheat rotation cycle (from Nov. 1,1996 to Oct. 31, 1997) under three different conditions, which are A) no fertilizer, B) both chemical fertilizer and manure and, C) chemical fertilizer only. The processes of N2O emission were discussed in detail by comparing the model outputs with the results from field measurement. The comparison shows that the model is good at simulating most of the N3O emission pulses and trends. Although the simulated N2O emission fluxes are generally less than the measured ones, the model outputs during the dryland period, especially during the wheat reviving and maturing stages in spring, are much better than those during the paddy field period. Some sensitive experiments were made by simulating the N2O emissions in spring, when there is a smallest gap between the simulated fluxes and the measured ones. Meanwhile, the effects of some important regulating factors, such as the rainfall, N deposition by rainfall, temperature, tillage, ni?trogen fertilizer and manure application on N2O emission during this period were analyzed From the analysis, we draw a conclusion that soil moisture and fertilization are the most important regu?lating factors while the N2O emission is sensitive to some other factors, such as temperature, ma?nure, tillage and the wet deposition of atntospheric nitrate.
Dependence of the AGCM Climatology on the Method of Prescribing Surface Boundary Conditions and Its Climatological Implication
Lin Zhaohui, Bi Xunqiang, Wang Huijun, Zeng Qingcun
1999, 16(4): 593-607. doi: 10.1007/s00376-999-0034-z
By using IAP 9L AGCM, two sets of long-term climatological integration have been per-formed with the two different interpolation procedures for generating the daily surface boundary conditions. One interpolation procedure is the so-called “traditional” scheme, for which the daily surface boundary conditions are obtained by linearly interpolating between the observed monthly mean values, however the observed monthly means cannot be preserved after interpolation. The other one is the “new” scheme, for which the daily surface boundary conditions are obtained by linearly interpolating between the "artificial" monthly mean values which are based on, but are dif-ferent from the observed ones, after interpolating with this new scheme, not only the observed monthly mean values are preserved, the time series of the new generated daily values is also more consistent with the observation. Comparison of the model results shows that the differences of the globally or zonally averaged fields between these two integrations are quite small, and this is due to the compensating effect between the different regions. However, the differences of the two patterns (the global or regional geographical distributions), are quite significant, for example, the magni-tude of the difference in the JJA mean rainfall between these two integrations can exceed 2 mm/day over Asian monsoon regions, and the difference in DJF mean surface air temperature can also exceed 2oC over this region. The fact that the model climatology depends quite strongly on the method of prescribing the daily surface boundary conditions suggests that in order to validate the climate model or to predict the short-term climate anomalies, either the " new* interpolation scheme or the high frequency surface boundary conditions (e.g., daily or weekly data instead of the monthly data) should be introduced. Meanwhile, as for the coupled model, the daily coupling scheme between the different component cli?mate models (e.g., atmospheric and oceanic general circulation models) is preferred in order to partly eliminate the “climate drift” problem which may appear during the course of direct coupling.
A Condensed Gas-Phase Chemical Model and Its Application
Wang Tijian, Sun Zhaobo, Li Zongkai
1999, 16(4): 608-618. doi: 10.1007/s00376-999-0035-y
Using the “lumped mechanism” and “counting species” methods, we developed a condensed gas-phase chemical model based on a simplified one. The modified quasi-steady-state approximation (QSSA) scheme and the error redistribution mass conservation technique are adopted to solve the atmospheric chemistry ki-netic equations. Results show that the condensed model can well simulate concentration variations of gas species such as SO2, NOx, O3, H2O2 and conversion rates of SO2 and NOx, transformation to H2SO4 and HNO3. These results are in good agreement with those from the simplified model, The conversion rates of SO2 and NOx under different initial concentrations and meteorological conditions are computed, and the results can be directly applied to regional acid deposition model.
On the Upper Oceanic Heat Budget in the South China Sea: Annual Cycle
Yang Haijun, Liu Qinyu, Jia Xujing
1999, 16(4): 619-629. doi: 10.1007/s00376-999-0036-x
The upper oceanic heat budget in the South China Sea (SCS) is studied on the basis of ocean surface heal flux, upper sea heat storage and horizontal oceanic heat transport calculated from Comprehensive Ocean and Atmosphere Data Set. Several useful conclusions can be obtained and they are helpful for us to understand the climatologically thermal condition in the SCS. The annual variation of net heat budget reflects the adjustment and sudden change of the monsoon circulation over the SCS. The variation of upper oceanic heat storage of the SCS is tightly connected with the oceanic heat transport as well as the vertical movement in the SCS and so on.
Influence of ENSO Event on the Maintenance of Pacific Storm Track in the Northern Winter
Zhu Weijun, Sun Zhaobo
1999, 16(4): 630-640. doi: 10.1007/s00376-999-0037-9
An influence of ENSO event on the maintenance of Pacific storm track in the Northern winter is stu-died based on the NCEP/ NCAR daily re-analysis data. The result shows that in El Ni?o (La Ni?a) year an increase (decrease) of baroclinicity over the storm track, extension (withdrawal) eastward and southward (westward but northward for its east end) of its position and augmentation (debilitation) of its strength are closely in response to the enhancement (abatement) of eddy heat flux and momentum flux that are associ-ated with the development of the storm track. It thus indicates that ENSO event exerts an important impact on its maintenance and development in the Pacific Ocean.
The Interdecadal Variation Characteristics of Arctic Sea Ice Cover-ENSO-East Asian Monsoon and Their Interrelationship at Quasi-Four Years Time Scale
Zhu Congwen, Chen Longxun, Nobuo Yamazaki
1999, 16(4): 641-652. doi: 10.1007/s00376-999-0038-8
Interdecadal and quasi-four years variation characteristics of Arctic sea ice cover, ENSO and East Asian mon-soon index (EAMI) are analyzed based on Singular Spectrum Analys. (SSA), lead-lag correlation and EOF for the past four decades. Results show that the Arctic sea ice cover decreased in the early 1970s, several years earlier than that of global SSTA increase in the mid 1970s, which indicates that recent warming over the Northern Hemisphere firstly begins in the Arctic region in the 1970s, Great change of the East Asian monsoon intensity from stronger to weaker in summer (from weaker to stronger in winter) took place in the mid 1970s response to the abrupt modulation of SSTA particularly in the tropical eastern Pacific. Focus on the quasi-four years oscillation, close relationship is found among the sea ice cover, ENSO and EAMI based on lead-lag correlation. In which, the correlation coefficient reaches its maximum when the index of NINO3 SSTA variation takes 6 and 9 months lead of the western Pacific subtropical high and sea ice cover index in Section-III. Their interaction can be explained in the framework of asymmetric Walker circulation anomaly and Western Pacific Northern Pole (WPN) teleconnection pattern in the context of quasi-four years oscillation.