Changes in daily climate extremes in Xinjiang, northwestern China

Based on daily maximum and minimum surface air temperature and precipitation records at 48 meteorological stations in Xinjiang, the spatial and temporal distributions of climate extreme indices have been analyzed during 1961-2008. Twelve temperature extreme indices and six precipitation extreme indices are studied. Temperature extremes are highly correlated to annual mean temperature, which appears to be significantly increasing by 0.08 °C per year, indicating that changes in temperature extremes reflect consistent warming. The warming tendency is clearer at stations in northern Xinjiang as reflected by mean temperature. The frequencies of cold days and nights have both decreased, respectively by 0.86 and 2.45 d/decade, but the frequencies of warm days and nights have both increased, respectively by +1.62 and +4.85 d/decade. Over the same period, the number of frost days shows a statistically significant decreasing trend of 2.54 d/decade. The growing season length and the number of summer days exhibit significant increasing trends at rates of +2.62 and +2.86 d/decade, respectively. The diurnal temperature range has decreased by 0.28 °C/decade. Both annual extreme low and high temperatures exhibit significant increasing trend, with the former clearly larger than the latter. For precipitation indices, regional annual total precipitation shows an increasing trend and most other precipitation indices are strongly correlated with annual total precipitation. Average wet day precipitation, maximum 1-day and 5-day precipitation, and heavy precipitation days show increasing trends, but only the last is statistically significant. A decreasing trend is found for consecutive dry days. For all precipitation indices, stations in northwestern Xinjiang have the largest positive trend magnitudes, while stations in northern Xinjiang have the largest negative magnitudes.     

华北平原降水的长期趋势分析(英文)

The North China Plain (NCP) is the most important food grain producing area in China and has suffered from serious water shortages. To capture variation water availability, it is necessary to have an analysis of changing trends in precipitation. This study, based on daily precipitation data from 47 representative stations in NCP records passed the homogeneity test, analyzed the trend and amplitude of variation in monthly, seasonal and annual precipitation, annual maximum continuous no-rain days, annual rain days, rainfall intensity, and rainfall extremes from 1960 to 2007, using the MannKendall (M-K) test and Sen’s slope estimator. It was found that monthly precipitation in winter had a significant increasing trend in most parts, while monthly precipitation in July to September showed a decreasing trend in some parts of NCP. No significant changing trend was found for the annual, dry and wet season precipitation and rainfall extremes in the majority of NCP.A significant decreasing trend was detected for the maximum no-rain duration and annual rain days in the major part of NCP. It was concluded that the changing trend of precipitation in NCP had an apparent seasonal and regional pattern, i.e., precipitation showed an obvious increasing trend in winter, but a decreasing trend in the rainy season (July to September), and the changing trend was more apparent in the northern part than in the southern and middle parts. This implies that with global warming, seasonal variation of precipitation in NCP tends to decline with an increasing of precipitation in winter season, and a decreasing in rainy season, particularly in the sub-humid northern part.     

The decreasing spring frost risks during the flowering period for woody plants in temperate area of eastern China over past 50 years

The temperate monsoon area of China is an important agricultural region but late spring frosts have frequently caused significant damage to plants there. Based on phenological data derived from the Chinese Phenological Observation Network （CPON）, corresponding meteorological data from 12 study sites and phenological modeling, changes in flowering times of multiple woody plants and the frequency of frost occurrence were analyzed. Through these analyses, frost risk during the flowering period at each site was estimated. Results of these estimates suggested that first flowering dates （FFD） in the study area advanced significantly from 1963 to 2009 at an average rate of -1.52 days/decade in North-east China （P〈0.01） and -2.22 days/decade （P〈0.01） in North China. Over the same period, the number of frost days in spring decreased and the last frost days advanced across the study area. Considering both flowering phenology and occurrence of frost, the frost risk index, which measures the percentage of species exposed to frost during the flowering period in spring, exhibited a decreasing trend of -0.37% per decade （insignificant） in Northeast China and -1.80% per decade （P〈0.01） in North China, implying that frost risk has reduced over the past half century. These conclusions provide important information to agriculture and forest managers in devising frost protection schemes in the region.     

Spatial distributions and interannual variations of snow cover over China in the last 40 years

By using the observational snow data of more than 700 weather stations,the interannual temporal and spatial characteristics of seasonal snow cover in China were analyzed.The results show that northern Xinjiang,northeastern China-Inner Mongolia,and the southwestern and southern portions of Tibetan Plateau are three regions in China with high seasonal snow cover and also an interannual anomaly of snow cover.According to the trend of both the snow depth and snow cover days,there are three changing patterns for the seasonal snow cover:The first type is that both snow depth and snow cover days simultaneously increase or decrease;this includes northern Xinjiang,middle and eastern Inner Mongolia,and so on.The second is that snow depth increases but snow cover days decrease;this type mainly locates in the eastern parts of the northeastern plain of China and the upper reaches of the Yangtze River.The last type is that snow depth decreases but snow cover days increase at the same time such as that in middle parts of Tibetan Plateau.Snow cover in China appears to have been having a slow increasing trend during the last 40 years.On the decadal scale,snow depth and snow cover days slightly increased in the 1960s and then decreased in the 1970s;they again turn to increasing in the 1980s and persist into 1990s.     

1961-2008年中国西南地区极端气候变化幅度的海拔效应(英文)

A total of 12 indices of temperature extremes and 11 indices of precipitation ex-tremes at 111 stations in southwestern China at altitudes of 285-4700 m were examined for the period 1961-2008. Significant correlations of temperature extremes and elevation in-cluded the trends of diurnal temperature range, frost days, ice days, cold night frequency and cold day frequency. Regional trends of growing season length, warm night frequency, coldest night and warmest night displayed a statistically significant positive correlation with altitude. These characteristics indicated the obvious warming with altitude. For precipitation extreme indices, only the trends of consecutive dry days, consecutive wet days, wet day precipitation and the number of heavy precipitation days had significant correlations with increasing alti-tude owing to the complex influence of atmospheric circulation. It also indicated the increased precipitation mainly at higher altitude areas, whereas the increase of extreme precipitation events mainly at lowers altitude. In addition, the clearly local influences are also crucial on climate extremes. The analysis revealed an enhanced sensitivity of climate extremes to ele-vation in southwestern China in the context of recent warming.     

Change in summer daily precipitation and its relation with air temperature in Northwest China during 1957–2016

On the basis of the summer daily-precipitation meteorological data collected from weather stations across Northwest China from 1957 to 2016, this study evaluated the trends in 12-daily precipitation indices in the summer season and their relations with air temperature. Precipitation-event intensity, which was averaged over the total study area, increased in recent decades although the total precipitation continuously decreased. In particular, intensity generally decreased in the northern and eastern parts and increased in the southern and western parts of the study area. None of the 12 precipitation indices was significantly correlated with temperature in Xinjiang; R95 N(number of events with precipitation greater than the long-term95 th percentile), RX1 day(greatest 1-day total precipitation), PI(simple daily intensity), and R10(number of heavy-precipitation days) were significantly and positively correlated with temperature in Qinghai–Gansu. However, low correlation coefficients were observed. In the Loess Plateau, P(total precipitation), WS(maximum number of consecutive wet days),R95 N, and WD(number of wet days) were significantly and negatively correlated with temperature, whereas Gini(gini concentration index) and DS(maximum number of consecutive dry days) were significantly and positively correlated with temperature. Results of the study suggested that climate shift was evident in terms of daily precipitation, and the study area faced new challenges involving precipitation-event intensity increasing in the southwestern part and unevenly dispersing in the northwest.     

Climatic characteristics of high temperature in East China during 1961–2005

Based on the daily maximum temperature data covering the period 1961–2005, temporal and spatial characteristics and their changing in mean annual and monthly high temperature days (HTDs) and the mean daily maximum temperature (MDMT) during annual and monthly HTDs in East China were studied. The results show that the mean annual HTDs were 15.1 and the MDMT during annual HTDs was 36.3℃ in the past 45 years. Both the mean annual HTDs and the MDMT during annual HTDs were negative anomaly in the1980s and positive anomaly in the other periods of time, oscillating with a cycle of about 12–15 years. The mean annual HTDs were more in the southern part, but less in the northern part of East China. The MDMT during annual HTDs was higher in Zhejiang, Anhui and Jiangxi provinces in the central and western parts of East China. The high temperature process (HTP) was more in the southwestern part, but less in northeastern part of East China. Both the HTDs and the numbers of HTP were at most in July, and the MDMT during monthly HTDs was also the highest in July. In the first 5 years of the 21st century, the mean annual HTDs and the MDMT during annual HTDs increased at most of the stations, both the mean monthly HTDs and the MDMT during monthly HTDs were positive anomalies from April to October, the number of each type of HTP generally was at most and the MDMT in each type of HTP was also the highest.     

1961–2011年中国南方地区极端降水事件变化(英文)

Based on the daily precipitation from a 0.5°×0.5° gridded dataset and meteorological stations during 1961–2011 released by National Meteorological Information Center, the reliability of this gridded precipitation dataset in South China was evaluated. Five precipitation indices recommended by the World Meteorological Organization(WMO) were selected to investigate the changes in precipitation extremes of South China. The results indicated that the bias between gridded data interpolated to given stations and the corresponding observed data is limited, and the proportion of the number of stations with bias between –10% and 0 is 50.64%. The correlation coefficients between gridded data and observed data are generally above 0.80 in most parts. The average of precipitation indices shows a significant spatial difference with drier northwest section and wetter southeast section. The trend magnitudes of the maximum 5-day precipitation(RX5day), very wet day precipitation(R95), very heavy precipitation days(R20mm) and simple daily intensity index(SDII) are 0.17 mm·a–1, 1.14 mm·a–1, 0.02 d·a–1 and 0.01 mm·d–1·a–1, respectively, while consecutive wet days(CWD) decrease by –0.05 d·a–1 during 1961–2011. There is spatial disparity in trend magnitudes of precipitation indices, and approximate 60.85%, 75.32% and 75.74% of the grid boxes show increasing trends for RX5 day, SDII and R95, respectively. There are high correlations between precipitation indices and total precipitation, which is statistically significant at the 0.01 level.     

Climatic characteristics of high temperature in East China during 1961–2005

Based on the daily maximum temperature data covering the period 1961-2005, temporal and spatial characteristics and their changing in mean annual and monthly high temperature days（HTDs）and the mean daily maximum temperature（MDMT）during annual and monthly HTDs in East China were studied.The results show that the mean annual HTDs were 15.1 and the MDMT during annual HTDs was 36.3℃in the past 45 years.Both the mean annual HTDs and the MDMT during annual HTDs were negative anomaly in the1980s and positive anomaly in the other periods of time,oscillating with a cycle of about 12-15 years.The mean annual HTDs were more in the southern part,but less in the northern part of East China.The MDMT during annual HTDs was higher in Zhejiang,Anhui and Jiangxi provinces in the central and western parts of East China.The high temperature process（HTP） was more in the southwestern part,but less in northeastern part of East China.Both the HTDs and the numbers of HTP were at most in July,and the MDMT during monthly HTDs was also the highest in July.In the first 5 years of the 21st century,the mean annual HTDs and the MDMT during annual HTDs increased at most of the stations,both the mean monthly HTDs and the MDMT during monthly HTDs were positive anomalies from April to October,the number of each type of HTP generally was at most and the MDMT in each type of HTP was also the highest.     

Spatial and temporal temperature variations in Xinjiang, China during 1961–2008

This study examines spatial and temporal changes in 16 extreme temperature indices at 37 weather stations in Xinjiang and their associations with changes in climate means during 1961–2008. Linear regression analyses reveal that significant increasing trends in temperature were observed over Xinjiang, with the rate of 0.13 °C/decade, 0.24 °C/decade, and 0.52 °C/decade for annual mean temperature, annual maximum, and minimum temperature, respectively. Annual frequency of cool nights (days) has decreased by -2.45 days/decade (-0.86 days/decade), whereas the frequency of warm nights (days) has increased by 4.85 days/decade (1.62 days/decade). Seasonally, the frequencies of summer warm nights and days are changing more rapidly than the corresponding frequencies for cool nights and days. However, normalization of the extreme and mean series shows that the rate of changes in extreme temperature events are generally less than those of mean temperatures, except for winter cold nights which are changing as rapidly as the winter mean minimum temperatures. These results indicate that there have been seasonally and diurnally asymmetric changes in extreme temperature events relative to recent increases in temperature means in Xinjiang.     

1962–2011年长江流域极端气温变化（英文）

Based on daily maximum and minimum temperature observed by the China Meteorological Administration at 115 meteorological stations in the Yangtze River Basin from 1962 to 2011,the methods of linear regression,principal component analysis and correlation analysis are employed to investigate the temporal variability and spatial distribution of temperature extremes.Sixteen indices of extreme temperature are selected.The results are as follows:(1) The occurrence of cold days,cold nights,ice days,frost days and cold spell duration indicator has significantly decreased by –0.84,–2.78,–0.48,–3.29 and –0.67 days per decade,respectively.While the occurrence of warm days,warm nights,summer days,tropical nights,warm spell duration indicator and growing season length shows statistically significant increasing trends at rates of 2.24,2.86,2.93,1.80,0.83 and 2.30 days per decade,respectively.The tendency rate of the coldest day,coldest night,warmest day,warmest night and diurnal temperature range is 0.33,0.47,0.16,0.19 and –0.07℃ per decade,respectively.(2) The magnitudes of changes in cold indices(cold nights,coldest day and coldest night) are obviously greater than those of warm indices(warm nights,warmest day and warmest night).The change ranges of night indices(warm nights and cold nights) are larger than those of day indices(warm days and cold days),which indicates that the change of day and night temperature is asymmetrical.(3) Spatially,the regionally averaged values of cold indices in the upper reaches of the Yangtze River Basin are larger than those in the middle and lower reaches.However,the regionally averaged values of most warm indices(except warm spell duration indicator) and growing season length in the middle and lower reaches are larger than those in the upper reaches.(4) The extreme temperature indices are well correlated with each other except diurnal temperature range.     

经验模态分解下中国气温变化趋势的区域特征

By the Empirical Mode Decomposition method, we analyzed the observed monthly average temperature in more than 700 stations from 1951-2001 over China. Simultaneously, the temperature variability of each station is calculated by this method, and classification chart of long term trend and temperature variability distributing chart of China are obtained, supported by GIS, 1 kmxl km resolution. The results show that： in recent 50 years, the temperature has increased by more than 0.4~C/10a in most parts of northern China, while in Southwest China and the middle and lower Yangtze Valley, the increase is not significant. The areas with a negative temperature change rate are distributed sporadically in Southwest China. Meanwhile, the temperature data from 1881 to 2001 in nine study regions in China are also analyzed, indicating that in the past 100 years, the temperature has been increasing all the way in Northeast China, North China, South China, Northwest China and Xinjiang and declining in Southwest China. An inverse ‘V-shaped’ trend is also found in Central China. But in Tibet the change is less significant.     

1960-2012年内蒙古寒潮时空变化特征(英文)

In this study, we analyzed the spatiotemporal variation of cold surges in Inner Mongolia between 1960 and 2012 and their possible driving factors using daily minimum temperature data from 121 meteorological stations in Inner Mongolia and the surrounding areas. These data were analyzed utilizing a piecewise regression model, a Sen+MannKendall model, and a correlation analysis. Results demonstrated that(1) the frequency of single-station cold surges decreased in Inner Mongolia during the study period, with a linear tendency of –0.5 times/10a(–2.4 to 1.2 times/10a). Prior to 1991, a significant decreasing trend of –1.1 times/10a(–3.3 to 2.5 times/10a) was detected, while an increasing trend of 0.45 times/10a(–4.4 to 4.2 times/10a) was found after 1991. On a seasonal scale, the trend in spring cold surges was consistent with annual values, and the most obvious change in cold surges occurred during spring. Monthly cold surge frequency displayed a bimodal structure, and November witnessed the highest incidence of cold surge.(2) Spatially, the high incidence of cold surge is mainly observed in the northern and central parts of Inner Mongolia, with a higher occurrence observed in the northern than in the central part. Inter-decadal characteristic also revealed that high frequency and low frequency regions presented decreasing and increasing trends, respectively, between 1960 and 1990. High frequency regions expanded after the 1990 s, and regions exhibiting high cold surge frequency were mainly distributed in Tulihe, Xiao’ergou, and Xi Ujimqin Banner.(3) On an annual scale, the cold surge was dominated by AO, NAO, CA, APVII, and CQ. However, seasonal differences in the driving forces of cold surges were detected. Winter cold surges were significantly correlated with AO, NAO, SHI, CA, TPI, APVII, CW, and IZ, indicating they were caused by multiple factors. Autumn cold surges were mainly affected by CA and IM, while spring cold surges were significantly correlated with CA and APVII.     

Modeling net primary productivity of the terrestrial ecosystem in China from 1961 to 2005简

Net primary productivity （NPP） is the structure and function of the ecosystem. NPP can most important index that represents the be simulated by dynamic global vegetation models （DGVM）, which are designed to represent vegetation dynamics relative to environ- mental change. This study simulated the NPP of China＇s ecosystems based on the DGVM Integrated Biosphere Simulator （IBIS） with data on climate, soil, and topography. The appli- cability of IBIS in the NPP simulation of China＇s terrestrial ecosystems was verified first. Comparison with other relevant studies indicates that the range and mean value of simula- tions are generally within the limits of observations; the overall pattern and total annual NPP are close to the simulations conducted with other models. The simulations are also close to the NPP estimations based on remote sensing. Validation proved that IBIS can be utilized in the large-scale simulation of NPP in China＇s natural ecosystem. We then simulated NPP with climate change data from 1961 to 2005, when warming was particularly striking. The following are the results of the simulation. （1） Total NPP varied from 3.61 GtC/yr to 4.24 GtC/yr in the past 45 years and exhibited minimal significant linear increase or decrease. （2） Regional differences in the increase or decrease in NPP were large but exhibited an insignificant overall linear trend. NPP declined in most parts of eastern and central China, especially in the Loess Plateau. （3） Similar to the fluctuation law of annual NPP, seasonal NPP also displayed an insignificant increase or decrease; the trend line was within the general level. （4） The re- gional differences in seasonal NPP changes were large. NPP declined in spring, summer, and autumn in the Loess Plateau but increased in most parts of the Tibetan Plateau.     

Classification of snow cover days in western China and comparison with satellite remote sensing data

The daily snow cover data from 232 meteorological stations to the west of 105°E in China for the period 1951–2004 were used to classify the snow cover and analyze decadal variations of snow cover types in western China, and comparison was made between the observational data and those retrieved from passive microwave remote sensing data (SMMR and SSM/I) in 1980–2004. The results show that stable snow-covered areas included northern Xinjiang, the Tianshan Mountains, and the eastern Tibetan Plateau with more than 60 snow cover days; no snow cover was found in the center of the southern Xinjiang Basin, the Sichuan Basin, and southern Yunnan. In addition to the above-mentioned, there were unstable snow-covered areas in western China. Furthermore, the snow cover types in northern Xinjiang, the Tianshan Mountains, the Hexi Corridor, and the vast areas from Chengdu to Kunming were unchanged. In the 1980s, the south-north dividing line between the major snow-covered area and snow-free area advanced to its most southern position. The snow cover days calculated from satellite remote sensing were generally longer than those from observational data in western China, mainly in the higher-altitude mountains, the Hexi Corridor, and the western Sichuan Plateau.     

Regional features of the temperature trend in China based on Empirical Mode Decomposition

By the Empirical Mode Decomposition method, we analyzed the observed monthly average temperature in more than 700 stations from 1951–2001 over China. Simultaneously, the temperature variability of each station is calculated by this method, and classification chart of long term trend and temperature variability distributing chart of China are obtained, supported by GIS, 1 km×1 km resolution. The results show that: in recent 50 years, the temperature has increased by more than 0.4℃/10a in most parts of northern China, while in Southwest China and the middle and lower Yangtze Valley, the increase is not significant. The areas with a negative temperature change rate are distributed sporadically in Southwest China. Meanwhile, the temperature data from 1881 to 2001 in nine study regions in China are also analyzed, indicating that in the past 100 years, the temperature has been increasing all the way in Northeast China, North China, South China, Northwest China and Xinjiang and declining in Southwest China. An inverse ‘V-shaped’ trend is also found in Central China. But in Tibet the change is less significant.     

Variations in spring leaf phenology and leaf freezing damage of common woody species in China北大核心CSCD

Freezing damage results in the dehydration of plant cells and reduces the photosynthetic capacity of plants, which causes significant losses to ecology and economy. Over the past 40 years, global warming has reduced the frequency and intensity of frost events while bringing forward the spring phenology of plants, increasing the exposure of their leaves and flowers to harsh cold temperatures. Therefore, the dual effects of climate warming should be considered in order to accurately assess the changes of plant freezing damage. To date, there is no systematic analysis of plant freezing damage in different climatic regions of China. Based on phenological observation records from the China Phenological Observation Network, leaf frost damage of four common woody plants (Ulmus pumila, Robinia pseudoacacia, Salix babylonica, Fraxinus chinensis) in the spring over the past 40 years was calculated, and the spatio-temporal patterns were analyzed. We also investigated the change in the occurrence time of maximum frost damage (TMFD) and its relationship with plant phenology. The results show that: 1) Most species presented an overall trend towards an earlier leaf unfolding date, and the advancing trend was significant and greater than 1 d/a in about 60% of the regions (P<0.05). 2) The TMFD occurred earlier in 72.22%-83.03% of the regions, which was closely related to plants' earlier leaf unfolding date. The TMFD of all species advanced the most (8.3 days) in the temperate climate zone, followed by the warm temperate, subtropical, plateau, and cold temperate zones. 3) The leaves of U. pumila, R. pseudoacacia and S. babylonica suffered more freezing damage in the spring, and the most significant freezing damage was mainly found in the north of 50°N region and part of the west of the Qinghai-Tibet Plateau. In comparison, the leaves of F. chinensis suffered less frost damage due to later leaf unfolding date and stronger leaf frost resistance. With regard to interannual variations, the average freezing damage of U. pumila, R. pseudoacacia and S. babylonica increased significantly (P<0.05), but that of F. chinensis did not change obviously. In addition, the freezing damage of U. pumila and S. babylonica increased the most in the cold temperate zone, while that of R. pseudoacacia increased in about 10% of the regions in the plateau climate zone, and 3%-6% of the regions in the cold temperate, temperate, and warm temperate climate zones. The freezing damage of F. chinensis merely increased in the warm temperate zone. The results of this study can provide a reference for assessing the risk of plant freezing damage accurately and help develop regional-specific response and adaptation strategies to climate change. © 2023, Editorial office of PROGRESS IN GEOGRAPHY. All rights reserved.     

Changes in temperature extremes in the Yangtze River Basin, 1962–2011简

Based on daily maximum and minimum temperature observed by the China Mete- orological Administration at 115 meteorological stations in the Yangtze River Basin from 1962 to 2011, the methods of linear regression, principal component analysis and correlation analysis are employed to investigate the temporal variability and spatial distribution of tem- perature extremes. Sixteen indices of extreme temperature are selected. The results are as follows： （1） The occurrence of cold days, cold nights, ice days, frost days and cold spell du- ration indicator has significantly decreased by -0.84, -2.78, -0.48, -3.29 and -0.67 days per decade, respectively. While the occurrence of warm days, warm nights, summer days, tropi- cal nights, warm spell duration indicator and growing season length shows statistically sig- nificant increasing trends at rates of 2.24, 2.86, 2.93, 1.80, 0.83 and 2.30 days per decade, respectively. The tendency rate of the coldest day, coldest night, warmest day, warmest night and diurnal temperature range is 0.33, 0.47, 0.16, 0.19 and -0.07~C per decade, respectively （2） The magnitudes of changes in cold indices （cold nights, coldest day and coldest night） are obviously greater than those of warm indices （warm nights, warmest day and warmest night）. The change ranges of night indices （warm nights and cold nights） are larger than those of day indices （warm days and cold days）, which indicates that the change of day and night tem- perature is asymmetrical. （3） Spatially, the regionally averaged values of cold indices in the upper reaches of the Yangtze River Basin are larger than those in the middle and lower reaches. However, the regionally averaged values of most warm indices （except warm spell duration indicator） and growing season length in the middle and lower reaches are larger than those in the upper reaches. （4） The extreme temperature indices are well correlated with each other except diurnal temperature range.     

中国碳排放对国际贸易影响的经验分析(英文)

International trade is an important impact factor to the carbon emissions of a country.As the rapid development of Chinese foreign trade since its entry into the WTO in 2002,the effects of international trade on carbon emissions of China are more and more significant.Using the recent available input-output tables of China and energy consumption data,this study estimated the effects of Chinese foreign trade on carbon emissions and the changes of the effects by analyzing the emissions embodied in trade between 2002 and 2007.The re-sults showed a more and more significant exporting behavior of embodied carbon emissions in Chinese international trade.From 2002 to 2007,the proportion of net exported emissions and domestic exported emissions in domestic emissions increased from 18.32% to 29.79% and from 23.97% to 34.76%,respectively.In addition,about 22.10% and 32.29% of the total imported emissions were generated in processing trade in 2002 and 2007,respectively,which were imported and later exported emissions.Although,most of the sectors showed a growth trend in imported and exported emissions,sectors of electrical machinery and communication electronic equipment,chemical industry,and textile were still the biggest emission exporters,the net exported emissions of which were also the largest.For China and other developing countries,technology improvement may be the most favorable and acceptable ways to re-duce carbon emissions at present stage.In the future negotiations on emissions reduction,it would be more fair and reasonable to include the carbon emissions embodied in international trade when accounting the total emissions of an economy.     

Temporal-spatial characteristics of observed key parameters of snow cover in China during 1957–2009

Using observed snow cover data from Chinese meteorological stations, this study indicated that annual mean snow depth, Snow Water Equivalent (SWE), and snow density during 1957–2009 were 0.49 cm, 0.7 mm, and 0.14 g/cm³ over China as a whole, respectively. On average, they were all the smallest in the Qinghai-Tibetan Plateau (QTP), and were greater in northwestern China (NW). Spatially, the regions with greater annual mean snow depth and SWE were located in northeastern China including eastern Inner Mongolia (NE), northern Xinjiang municipality, and a small fraction of southwestern QTP. Annual mean snow density was below 0.14 g/cm³ in most of China, and was higher in the QTP, NE, and NW. The trend analyses revealed that both annual mean snow depth and SWE presented increasing trends in NE, NW, the QTP, and China as a whole during 1957–2009. Although the trend in China as a whole was not significant, the amplitude of variation became increasingly greater in the second half of the 20th century. Spatially, the statistically significant (95%-level) positive trends for annual mean snow depth were located in western and northern NE, northwestern Xinjiang municipality, and northeastern QTP. The distribution of positive and negative trends for annual mean SWE were similar to that of snow depth in position, but not in range. The range with positive trends of SWE was not as large as that of snow depth, but the range with negative trends was larger.