## 2007 Vol. 24, No. 6

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2007, 24(6): 940-953. doi: 10.1007/s00376-007-0940-x
[Abstract](1125) [PDF 194KB](1779)
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Recent progress in atmospheric observation techniques, observational systems and their application in China are reviewed. According to different observational platforms, the review is presented in three sections, i.e., satellite remote sensing (SRS), ground-based observation technologies and applications, and aircraft/balloon measurements. The section satellite remote sensing" presents advances in SRS techniques, SRS of clouds and aerosols, and SRS of trace gases and temperature/moisture profiles. The section ground-based observation technologies and applications" focuses on research such as lidar systems and applications, sun/sky radiometer and broadband radiation observations, weather radar and wind profilers, GPS measurements, and some new concept systems. The section aircraft/balloon measurements" presents some newly developed aircraft- and balloon-based sounding techniques.
2007, 24(6): 954-971. doi: 10.1007/s00376-007-0954-4
[Abstract](1895) [PDF 8155KB](2253)
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This article summarizes the main results and findings of studies conducted by Chinese scientists in the past five years. It is shown that observed climate change in China bears a strong similarity with the global average. The country-averaged annual mean surface air temperature has increased by 1.1oC over the past 50 years and 0.5--0.8oC over the past 100 years, slightly higher than the global temperature increase for the same periods. Northern China and winter have experienced the greatest increases in surface air temperature. Although no significant trend has been found in country-averaged annual precipitation, interdecadal variability and obvious trends on regional scales are detectable, with northwestern China and the mid and lower Yangtze River basin having undergone an obvious increase, and North China a severe drought. Some analyses show that frequency and magnitude of extreme weather and climate events have also undergone significant changes in the past 50 years or so. Studies of the causes of regional climate change through the use of climate models and consideration of various forcings, show that the warming of the last 50 years could possibly be attributed to an increased atmospheric concentration of greenhouse gases, while the temperature change of the first half of the 20th century may be due to solar activity, volcanic eruptions and sea surface temperature change. A significant decline in sunshine duration and solar radiation at the surface in eastern China has been attributed to the increased emission of pollutants. Projections of future climate by models of the NCC (National Climate Center, China Meteorological Administration) and the IAP (Institute of Atmospheric Physics, Chinese Academy of Sciences), as well as 40 models developed overseas, indicate a potential significant warming in China in the 21st century, with the largest warming set to occur in winter months and in northern China. Under varied emission scenarios, the country-averaged annual mean temperature is projected to increase by 1.5--2.1oC by 2020, 2.3--3.3oC by 2050, and by 3.9--6.0oC by 2100, in comparison to the 30-year average of 1961--1990. Most models project a 10%--12% increase in annual precipitation in China by 2100, with the trend being particularly evident in Northeast and Northwest China, but with parts of central China probably undergoing a drying trend. Large uncertainty exists in the projection of precipitation, and further studies are needed. Furthermore, anthropogenic climate change will probably lead to a weaker winter monsoon and a stronger summer monsoon in eastern Asia.
2007, 24(6): 972-992. doi: 10.1007/s00376-007-0972-2
[Abstract](1349) [PDF 1479KB](1902)
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This paper reviews briefly advances in recent research on monsoon by Chinese scholars, including primarily: (1) the establishment of various monsoon indices. In particular, the standardized dynamic seasonal variability index of the monsoon can delimit the geographical distribution of global monsoon systems and determine quantitatively the date of abrupt change in circulation. (2) The provision of three driving forces for the generation of monsoon. (3) The revelation of the heating-pump action of the Tibetan Plateau, which strengthens southerlies in the southern and southeastern periphery of the Plateau and results in a strong rainfall center from the northern Bay of Bengal (BOB) to the Plateau itself. (4) Clarification of the initial onset of the Asian Summer Monsoon (ASM) in the BOB east of 90E Indochina Peninsula (ICP) and the South China Sea, of which the rapid northward progression of tropical convection in the Sumatra and the rapid westward movement of the South Asia High to the Indochina Peninsula are the earliest signs. (5) The provision of an integrated mechanism for the onset of the East Asian Summer Monsoon (EASM), which emphasizes the integrated impact of sensible heat over Indian Peninsula, the warm advection of the Tibetan Plateau and the sensible heat and latent heat over the Indochina Peninsula on the one hand, and the seasonal phase-lock effect of the northward propagation of low frequency oscillation on the other. (6) The revelation of the planetary-scale moisture transport large-value band" from the Southern Hemisphere through to the Asian monsoon region and into the North Pacific, which is converged by several large-scale moisture transport belts in the Asian-Australian monsoon regions and whose variation influences directly the temporal and spatial distribution of summer rainfall in China. (7) Presenting the features of the seasonal advance of the EASM, the propagation of intraseasonal oscillation, and their relationship with rainfall in China; indicating that the intraseasonal oscillation of the EASM propagates in the form of a wave-train along the coast and behaves as monsoon surge propagating northward. (8) Describing the interannual and interdecadal variation of Asian monsoon, revealing the factors affecting it, and possible mechanisms of the variation of Asian monsoon. An elementary outlook on the existing problems and future direction of monsoon research is also provided.
2007, 24(6): 993-1023. doi: 10.1007/s00376-007-0993-x
[Abstract](1504) [PDF 3203KB](1872)
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Recent advances in studies of the structural characteristics and temporal-spatial variations of the East Asian monsoon (EAM) system and the impact of this system on severe climate disasters in China are reviewed. Previous studies have improved our understanding of the basic characteristics of horizontal and vertical structures and the annual cycle of the EAM system and the water vapor transports in the EAM region. Many studies have shown that the EAM system is a relatively independent subsystem of the Asian-Australian monsoon system, and that there exists an obvious quasi-biennial oscillation with a meridional tripole pattern distribution in the interannual variations of the EAM system. Further analyses of the basic physical processes, both internal and external, that influence the variability of the EAM system indicate that the EAM system may be viewed as an atmosphere-ocean-land coupled system, referred to the EAM climate system in this paper. Further, the paper discusses how the interaction and relationships among various components of this system can be described through the East Asia Pacific (EAP) teleconnection pattern and the teleconnection pattern of meridional upper-tropospheric wind anomalies along the westerly jet over East Asia. Such reasoning suggests that the occurrence of severe floods in the Yangtze and Huaihe River valleys and prolonged droughts in North China are linked, respectively, to the background interannual and interdecadal variability of the EAM climate system. Besides, outstanding scientific issues related to the EAM system and its impact on climate disasters in China are also discussed.
2007, 24(6): 1024-1036. doi: 10.1007/s00376-007-1024-7
[Abstract](1074) [PDF 1786KB](1656)
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2007, 24(6): 1037-1048. doi: 10.1007/s00376-007-1037-2
[Abstract](1161) [PDF 387KB](1396)
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The Climate Variability and Predictability (CLIVAR) program is one of the sub-programs of the World Climate Research Program (WCRP). In this paper, CLIVAR related research in China (2003--2006) is briefly reviewed, including four major components, namely, low-frequency intraseasonal oscillations, interannual variability, decadal variations in East Asia, and global warming simulations.
2007, 24(6): 1049-1059. doi: 10.1007/s00376-007-0863-6
[Abstract](918) [PDF 188KB](1253)
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This paper reviews the main theoretical progress of mesoscale weather dynamics since 2003, including: (1) The dynamic mechanisms of balanced and unbalanced flow are applied to study the genesis and development problems of mesoscale circulation. The symmetric instability and transverse-wave instability are analyzed in line and vortex atmosphere convection, and further research has been done on nonlinear convective symmetric instability. The interaction between forced convection and unstable convection and the wave characteristics of mesoscale motion are also discussed. (2) Intermediate atmosphere dynamic boundary layer models are developed. The complicated nonlinear interaction is analyzed theoretically between the atmospheric boundary layer and the free atmosphere. The structure of the topography boundary layer, atmospheric frontogenesis, the structure and circulation of the low-level front and other boundary layer dynamic problems are discussed. (3) The formation and development of meso-$\beta$-scale rainstorms under the background of the East-Asia atmosphere circulation are diagnosed with the variation of MPV (moist potential vorticity) anomalies. And some physical vectors are modified and applied in the moist atmosphere.
2007, 24(6): 1060-1076. doi: 10.1007/s00376-007-1060-3
[Abstract](4018) [PDF 4637KB](4136)
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Studies of the impacts of the Tibetan Plateau (TP) on climate in China in the last four years are reviewed. It is reported that temperature and precipitation over the TP have increased during recent decades. From satellite data analysis, it is demonstrated that most of the precipitation over the TP is from deep convection clouds. Moreover, the huge TP mechanical forcing and extraordinary elevated thermal forcing impose remarkable impacts upon local circulation and global climate. In winter and spring, stream flow is deflected by a large obstacle and appears as an asymmetric dipole, making East Asia much colder than mid Asia in winter and forming persistent rainfall in late winter and early spring over South China. In late spring, TP heating contributes to the establishment and intensification of the South Asian high and the abrupt seasonal transition of the surrounding circulations. In summer, TP heating in conjunction with the TP air pump cause the deviating stream field to resemble a cyclonic spiral, converging towards and rising over the TP. Therefore, the prominent Asian monsoon climate over East Asia and the dry climate over mid Asia in summer are forced by both TP local forcing and Eurasian continental forcing. Due to the longer memory of snow and soil moisture, the TP thermal status both in summer and in late winter and spring can influence the variation of Eastern Asian summer rainfall. A combined index using both snow cover over the TP and the ENSO index in winter shows a better seasonal forecast. On the other hand, strong sensible heating over the Tibetan Plateau in spring contributes significantly to anchor the earliest Asian monsoon being over the eastern Bay of Bengal (BOB) and the western Indochina peninsula. Qualitative prediction of the BOB monsoon onset was attempted by using the sign of meridional temperature gradient in March in the upper troposphere, or at 400 hPa over the TP. It is also demonstrated by a numerical experiment and theoretical study that the heating over the TP leads to a significant variability in the atmospheric circulation on a quasi-biweekly timescale, bearing much similarity to that found from observational studies. Finally, some important issues for further work in understanding the impacts of the TP are raised.
2007, 24(6): 1077-1085. doi: 10.1007/s00376-007-1077-7
[Abstract](1065) [PDF 157KB](1296)
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Recent advances in the study of nonlinear atmospheric and climate dynamics in China (2003--2006) are briefly reviewed. Major achievements in the following eight areas are covered: nonlinear error dynamics and predictability; nonlinear analysis of observational data; eddy-forced envelope Rossby soliton theory; sensitivity and stability of the ocean's thermohaline circulation; nonlinear wave dynamics; nonlinear analysis on fluctuations in the atmospheric boundary layer; the basic structures of atmospheric motions; some applications of variational methods.
2007, 24(6): 1086-1098. doi: 10.1007/s00376-007-1086-6
[Abstract](1004) [PDF 467KB](1400)
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Since the last International Union of Geodesy and Geophysics General Assembly (2003), predictability studies in China have made significant progress. For dynamic forecasts, two novel approaches of conditional nonlinear optimal perturbation and nonlinear local Lyapunov exponents were proposed to cope with the predictability problems of weather and climate, which are superior to the corresponding linear theory. A possible mechanism for the spring predictability barrier" phenomenon for the El Ni\~no-Southern Oscillation (ENSO) was provided based on a theoretical model. To improve the forecast skill of an intermediate coupled ENSO model, a new initialization scheme was developed, and its applicability was illustrated by hindcast experiments. Using the reconstruction phase space theory and the spatio-temporal series predictive method, Chinese scientists also proposed a new approach to improve dynamical extended range (monthly) prediction and successfully applied it to the monthly-scale predictability of short-term climate variations. In statistical forecasts, it was found that the effects of sea surface temperature on precipitation in China have obvious spatial and temporal distribution features, and that summer precipitation patterns over east China are closely related to the northern atmospheric circulation. For ensemble forecasts, a new initial perturbation method was used to forecast heavy rain in Guangdong and Fujian Provinces on 8 June 1998. Additionally, the ensemble forecast approach was also used for the prediction of a tropical typhoons. A new downscaling model consisting of dynamical and statistical methods was provided to improve the prediction of the monthly mean precipitation. This new downscaling model showed a relatively higher score than the issued operational forecast.
2007, 24(6): 1099-1108. doi: 10.1007/s00376-007-1099-1
[Abstract](1007) [PDF 248KB](1837)
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This paper summarizes the recent progress of numerical weather prediction (NWP) research since the last review was published. The new generation NWP system named GRAPES (the Global and Regional Assimilation and Prediction System), which consists of variational or sequential data assimilation and nonhydrostatic prediction model with options of configuration for either global or regional domains, is briefly introduced, with stress on their scientific design and preliminary results during pre-operational implementation. In addition to the development of GRAPES, the achievements in new methodologies of data assimilation, new improvements of model physics such as parameterization of clouds and planetary boundary layer, mesoscale ensemble prediction system and numerical prediction of air quality are presented. The scientific issues which should be emphasized for the future are discussed finally.
2007, 24(6): 1109-1120. doi: 10.1007/s00376-007-1109-3
[Abstract](980) [PDF 172KB](1679)
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A review is presented about the development and application of climate ocean models and ocean-atmosphere coupled models developed in China as well as a review of climate variability and climate change studies performed with these models. While the history of model development is briefly reviewed, emphasis has been put on the achievements made in the last five years. Advances in model development are described along with a summary on scientific issues addressed by using these models. The focus of the review is the climate ocean models and the associated coupled models, including both global and regional models, developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences. The progress of either coupled model development made by other institutions or climate modeling using internationally developed models also is reviewed.
2007, 24(6): 1121-1137. doi: 10.1007/s00376-007-1121-7
[Abstract](958) [PDF 208KB](1941)
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A review of China cloud physics research during 2003--2006 is made in this paper. The studies on cloud field experiments and observation, cloud physics and precipitation, including its theoretical applications in hail suppression and artificial rain enhancement, cloud physics and lightning, and clouds and climate change are included. Due primarily to the demand from weather modification activities, the issue of cloud physics and weather modification has been addressed in China with many field experiments and model studies. While cloud physics and weather modification is still an important research field, the interaction between aerosol, cloud and radiation processes, which is the key issue of current climate change research, has become a new research direction in China over the past four years.