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Zhang F.,Beijing Normal University | Zhou L.X.,Chinese Academy of Meteorological Sciences
Tellus, Series B: Chemical and Physical Meteorology

Carbon dioxide (CO2) emissions and sinks in western China are estimated and implied from atmospheric CO2 measured at Waliguan during the period of 1995-2008. The observed CO2 data are first classified as background, elevated, and sequestration, using a modified background identification method. Comparing it with two other methods tests the applicability of the method. By using this method, approximately 17.2% ± 1.2% and 10.1% ± 0.8% of all observed data are identified as elevated and sequestered CO2, respectively, the percentages (occurrence rates) for both of which increased during 1995-2008. CO2 emissions in western China have enhanced significantly in all seasons during the past 14 yr. Annual mean growth rates of CO2 emissions in the region increased by ~8.4 Tg C y-1 (3.9% y-1) during 1995-2008 but accelerated after 2000 to ~12.6 TgC y-1 (6.2% y-1). The growth rates of CO2 emission in western China are lower than the rest of the country. The annual mean emissions in the country during 1995-1999 and 2000-2006 are thought to be approximately 5.5 and 6.5 times higher than in western China, respectively. However, the growth rates of CO2 emissions in western China are higher than global increase rates as reported by other studies. CO2 sinks in western China varied from 86.0 Tg C y-1 in early 1995-1999 to 106.2 Tg C y-1 in 2005-2008. The most prominent change occurs in summer, indicating enhanced sequestration of photosynthetic CO2 taken up by vegetation. The growth rates in sequestered CO2 cannot keep up with the increase of CO2 emissions in the region. If this continues, it could potentially impact on the global carbon budget. © 2013 F. Zhang and L. X. Zhou. Source

Wang Y.Q.,Chinese Academy of Meteorological Sciences
Meteorological Applications

MeteoInfo is a suite of software tools which has been developed for meteorological data visualization and analysis. It includes a .NET class library for software developers and a desktop application for end users. MeteoInfo also supports several basic GIS functions and can read widely several used meteorological data formats such as NetCDF and GRIB. Complex meteorological analyses of grid and station data can be processed using provided data models. The class library can be conveniently used to develop software routines for manipulating spatial and meteorological data. The desktop application has a user friendly GUI and is a powerful tool to view and examine meteorological data sets. MeteoInfo can also be run automatically using scripting with the IronPython language. © 2012 Royal Meteorological Society. Source

Zhang R.-H.,Chinese Academy of Meteorological Sciences
Advances in Climate Change Research

In the last half century, a significant warming trend occurred in summer over eastern China in the East Asian monsoon region. However, there were no consistent trends with respect to the intensity of the East Asian summer monsoon (EASM) or the amount of summer rainfall averaged over eastern China. Both of the EASM and summer rainfall exhibited clear decadal variations. Obvious decadal shifts of EASM occurred around the mid- and late 1970s, the late 1980s and the early 1990s, and the late 1990s and early 2000s, respectively. Summer rainfall over eastern China exhibited a change in spatial distribution in the decadal timescale, in response to the decadal shifts of EASM. From the mid- and late 1970s to the late 1980s and the early 1990s, there was a meridional tri-polar rainfall distribution anomaly with more rainfall over the Yangtze River valley and less rainfall in North and South China; but in the period from the early 1990s to the late 1990s and the early 2000s the tri-polar distribution changed to a dipolar one, with more rainfall appearing over southern China south to the Yangtze River valley and less rainfall in North China. However, from the early 2000s to the late 2000s, the Yangtze River valley received less rainfall. The decadal changes in EASM and summer rainfall over eastern China in the last half century are closely related to natural internal forcing factors such as Eurasian snow cover, Arctic sea ice, sea surface temperatures in tropical Pacific and Indian Ocean, ocean-atmospheric coupled systems of the Pacific Decadal Oscillation (PDO) and Asian-Pacific Oscillation (APO), and uneven thermal forcing over the Asian continent. Up to now, the roles of anthropogenic factors, such as greenhouse gases, aerosols, and land usage/cover changes, on existing decadal variations of EASM and summer rainfall in this region remain uncertain. © 2015 National Climate Center (China Meteorological Administration). Production and hosting by Elsevier B.V. Source

Yu R.,Chinese Academy of Meteorological Sciences | Li J.,Chinese Academy of Meteorological Sciences
Journal of Climate

In this study, late-summer rainfall over eastern contiguous China is classified according to hourly intensity and the changes of moderate, intense, and extreme precipitation in response to variation of surface air temperature are analyzed. The e-folding decay intensity (I mi) derived from the exponential distribution of rainfall amount is defined as the threshold that partitions rainfall into moderate and intense rainfall, and the double e-folding decay intensity (I e) is used as the threshold to pick out extreme cases. The mean values of I mi and Ie are about 12 and 24 mm h -1, respectively. Between the two periods, 1966-85 and 1986-2005, the ratio between moderate and intense rainfall has experienced significant changes. And the spatial pattern of changes in the percentage of moderate rainfall presents a direct relation with that of the surface air temperature. Based on temperature changes, three regimes, regime N (north China), regime C (central eastern China), and regime S (southeastern coastal area of China), are defined. In warming regimes (regimes N and S), the percentage of moderate rainfall exhibits a decreasing trend. In regime C, where the temperature has fallen, the percentage of moderate rainfall increased prominently. In all three regimes there are significant negative (positive) correlations between the percentage of moderate (intense) rainfall and the temperature. The relation between the extreme rainfall and the surface air temperature is far more regionally dependent. With plenty of water supply and little change in relative humidity, the extreme rainfall increased in regime S. Although regime N also shows strong warming trends, there is no significant trend in extreme precipitation due to the lack of water vapor transportation. © 2012 American Meteorological Society. Source

Jiang Z.,Chinese Academy of Meteorological Sciences | Wang D.,Chinese Academy of Meteorological Sciences
Quarterly Journal of the Royal Meteorological Society

Conditional nonlinear optimal perturbations (CNOPs) are the initial perturbations that acquire the largest nonlinear evolution at the forecast time with some initial constraint condition. These CNOPs are calculated and examined during the development of two cold vortices with a regional mesoscale primitive-equation model. Computation is carried out over a 48-hour optimization time interval with a dry total perturbation energy norm. Attention is given to the CNOPs in terms of structure and evolution. For the particular cases studied, it was found that the CNOPs, similar to the first linear singular vectors, exhibit localness, in which the wind, temperature and surface pressure perturbation fields match the thermal wind balance qualitatively. The primary perturbation regions of CNOPs are closely related to the source regions of high potential vorticity corresponding to the cold vortices. What is more, CNOPs have deep baroclinic structures, which extend throughout the whole troposphere. With time, CNOPs increase their spatial size over larger areas and become quasi-barotropic at the optimization time. In addition, we found that the kinetic energy contributions are much larger than the potential energy contributions to the final perturbation energy. A noteworthy property is that although the dry total energy norm is used to measure the perturbation growth, the moisture perturbation energy appears early on, which is smaller than the kinetic energy but larger than the potential energy in the lower troposphere at the forecast time. The above numerical experiments are helpful for understanding the mechanism of perturbation growth during the formation of cold vortices. © 2011 Royal Meteorological Society. Source

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