Harmonious Inter-decadal Changes of July–August Upper Tropospheric Temperature Across the North Atlantic, Eurasian Continent,and North Pacific

The authors have developed an integral view of the inter-decadal variability of July-August （JA） tropospheric temperature across the entire subtropical Northern Hemisphere. Using reanalysis data and complementary balloon-borne measurements, the authors identify one major mode of variability for the period 1958 2001 which exhibits a significant cooling center over East Asia and warming centers over the North Atlantic and North Pacific. The cooling （warming） signals barotropically penetrate through the troposphere, with the strongest anomalies at 200-300 hPa. The amplitude of the cooling over East Asia is stronger than that of the warming over the North Atlantic （North Pacific） by a factor of 2 （3）. This dominant mode exhibits a declining tendency for the entire period examined, particularly before 1980. After the mid-1980s, the tendency has leveled off. Variations of the harmonious change of JA upper tropospheric temperature represented by the principal component of Empirical Orthogonal Function analysis exhibit significant negative （positive） correlations with SST anomalies in the eastern tropical Pacific and the western tropical Indian Ocean （mid-latitude North Pacific）. Possible mechanisms are discussed.

Long-term and inter-annual mass changes of Patagonia Ice Field from GRACE

Using more than 14 years of GRACE(Gravity Recovery and Climate Experiment) satellite gravimetry observations, we estimate the ice loss rate for the Patagonia Ice Field(PIF) of South America. After correcting the effects of glacier isostatic adjustment(GIA) and hydrological variations, the ice loss rate is -23.5 ± 8.1 Giga ton per year(Gt/yr) during the period April 2002 through December 2016, equivalent to an average ice thickness change of-1.3 m/yr if evenly distributed over PIF. The PIF ice mass change series also show obvious inter-annual variations during the entire period. For the time spans April 2002 to December 2007, January 2008 to December 2012 and January 2013 to December 2016, the ice loss rates are -26.4,-9.0 and -25.0 Gt/yr, respectively, indicating that the ice melting experienced significant slowing down and accelerating again in the past decade. Comparison with time series from temperature and precipitation data over PIF suggests that the inter-annual ice losses might not be directly correlated with the temperature changes and precipitation anomalies, and thus their interrelation is intricate. However, the dramatic ice loss acceleration in 2016(with more than 100 Gt within the first half of the year) appears closely related with the evident temperature increase and severe precipitation shortage over 2016, which are likely correlated with the strong E1 Nino event around 2016. Moreover, we compare the GRACE spherical harmonic(SH) and mass concentration(Mascon) solutions in estimating the PIF ice loss rate, and find that the Mascon result has larger uncertainty in leakage error correction,while the SH solutions can better correct leakage errors based on a constrained forward modeling iterative method. Thus the GRACE SH solutions with constrained forward modeling recovery are recommended to evaluating the ice mass change of PIF or other glacier regions with relatively smaller spatial scales.

A decomposition study of moisture transport divergence for inter-decadal change in East Asia summer rainfall during 1958-2001

In this paper, we report on the results of an investigation into inter-decadal changes in moisture transport and divergence in East Asia for the two periods 1980-2001 and 1958 1979. The aim is to explore the mechanism of summer rainfall change in the region after abrupt changes. The relevant changes are calculated using ERA-40 daily reanalysis datasets. The results show that both stationary and transient eddy moisture transports to the Chinese mainland have declined since the abrupt change in atmospheric general circulation in the late 1970s, leading to more rainfall in South China and less in the North. The anomalous rainfall pattern coincides well with anomalous large-scale moisture divergence in the troposphere, of which stationary-wave or monsoon transport is dominant, in comparison with the contribution of the transient eddies. F^rthermore, their divergences are found to be in opposite phases. In addition, meridional divergence is more important than its zonal counterpart, with an opposite phase in East Asia. Abnormal zonal moisture convergences appear in northwestern and northeastern parts of China, and are related to the excess rainfalls in these regions. An increase in transient eddy activity is one of the major mechanisms for excess rainfall in northern Xinjiang. Consequently, the anomalous rainfall pattern in East Asia results from a decline of the East Asian monsoon after the abrupt change, while the rainfall increase in northwestern China involves anomalies of both stationary waves and transient eddies on boreal westerly over the mid- and high latitudes.

Recent strong inter-decadal change of Meiyu in 121-year variations

The strongest change in Meiyu periods in the mid-lower Yangtze Basin （MLY） since 1885 occurred in the late 1970s： a stage of weak Meiyu from 1958 to 1978 abruptly transformed into a stage of plentiful Meiyu from 1979 to 1999. The average Meiyu amount of the latter 21 years increased by 66% compared with that of the former 21 years, accompanied by a significant increase in the occurrence of summer floods in the MLY. This change was closely related with the frequent phenomenon of postponed Meiyu ending dates （MED） and later onset dates of high summer （ODHS） in the MLY. To a considerable degree, this reflects an abrupt change of the summer climate in East China. Further analysis showed that the preceding factors contributing to inter-annual changes in Meiyu in the two 21-year stages delimited above were also very different from each other. The causes of change were associated with the following： China’s industrialization has greatly accelerated since the 1970s, accompanied by an increase in atmospheric pollution and a reduction of the solar radiation reaching the ground. The sand area of North China has also expanded due to overgrazing. The enhanced greenhouse effect is manifested in warm winters （especially in February）. Meanwhile, the January precipitation of the MLY has for the most part increased, and El Ni？o events have occurred more frequently since the late 1970s. A correlative scatter diagram consisting of these five factors mentioned above clearly shows that the two stages with opposite Meiyu characteristics are grouped in two contrasting locations with very different environmental （land-atmosphere） conditions. It is quite possible that we are now entering a new stage of lesser Meiyu, beginning in 2000.

STUDY ON INTER-DECADAL AND INTER-ANNUAL VARIABILITY OF SST IN THE TROPICAL OCEANS

Based on rotational empirical orthogonal function(REOF),max-entropy and Mexico-hat wavelet transform techniques,monthly SSTA of the tropical Pacific,Atlantic and Indian Oceans (32.5°S—32. 5°N)is investigated.It is shown that the inter-decadal variability and inter-annual variability take on global scale,and there exist their own significance areas.Moreover,through the total time series,the intensity of the variabilities is time-variable.And in fact,both the variabilities are usually coexistent.In significance areas of each of the variabilities,another variability is sometimes quite strong.

辽宁沙尘暴特点分析(英文)

Based on the factual data of dusty weather in Liaoning during the period from 1971 to 2009,the characteristics of dust storms were analyzed in the aspects including normality tests,inter-decadal variability,seasonal changes and spatial distribution characteristics.The results showed that the sandstorm weather in Liaoning tended to occur less frequently with the significant inter-decadal variation.The sandstorm in Liaoning occurred frequently in spring(most frequently in April).The dusty weather mainly occurred in the northwest of Liaoning,Fuxin and the northern region of Chaoyang during the period from late March to early May.

Spatial and temporal relationships between precipitation and ANPP of four types of grasslands in northern China

Precipitation is considered to be the primary resource limiting terrestrial biological activity in water-limited regions. Its overriding effect on the production of grassland is complex. In this paper, field data of 48 sites （including temperate meadow steppe, temperate steppe, temperate desert steppe and alpine meadow） were gathered from 31 published papers and monographs to analyze the relationship between above-ground net primary productivity （ANPP） and precipitation by the method of regression analysis. The results indicated that there was a great difference between spatial pattern and temporal pattern by which precipitation influenced grassland ANPP. Mean annual precipitation （MAP） was the main factor determining spatial distribution of grassland ANPP （r^2 = 0.61, P 〈 0.01）; while temporally, no significant relationship was found between the variance of AN PP and inter-annual precipitation for the four types of grassland. However, after dividing annual preeipitation into monthly value and taking time lag effect into account, the study found significant relationships between ANPP and precipitation. For the temperate meadow steppe, the key variable determining inter-annual change of ANPP was last August-May precipitation （r^2 = 0.47, P = 0.01）; for the temperate steppe, the key variable was July precipitation （r^2 = 0.36, P = 0.02）; for the temperate desert steppe, the key variable was April-June precipitation （r^2 = 0.51, P 〈 0.01）; for the alpine meadow, the key variable was last September-May precipitation （r^2 = 0.29, P 〈 0.05）. In comparison with analogous research, the study demonstrated that the key factor determining inter-annual changes of grassland ANPP was the cumulative precipitation in certain periods of that year or the previous year.

Temperature variation and abrupt change analysis in the Three-River Headwaters Region during 1961-2010

In this study, a monthly dataset of temperature time series （1961-2010） from 12 meteorological stations across the Three-River Headwater Region of Qinghai Province （THRHR） was used to analyze the climate change. The temperature variation and abrupt change analysis were examined by using moving average, linear regression, Spline interpolation, Mann-Kendall test and so on. Some important conclusions were obtained from this research, which mainly contained four aspects as follows. （1） There were several cold and warm fluctuations for the annual and seasonal average temperature in the THRHR and its three sub-headwater regions, but the temperature in these regions all had an obviously rising trend at the statistical significance level, especially after 2001. The spring, summer, autumn and annual average temperature increased evidently after the 1990s, and the winter average temperature exhibited an obvious upward trend after entering the 21st century. Except the standard value of spring temperature, the annual and seasonal temperature standard value in the THRHR and its three sub-headwater regions increased gradually, and the upward trend for the standard value of winter average temperature indicated significantly. （2） The tendency rate of annual average temperature in the THRHR was 0.36℃ 10a^-1, while the tendency rates in the Yellow River Headwater Region （YERHR）, Lancangjiang River Headwater Region （LARHR） and Yangtze River Headwater Region （YARHR） were 0.37℃ 10a^-1, 0.37℃ 10a^-1 and 0.34℃10a^-1 respectively. The temperature increased significantly in the south of Yushu County and the north of Nangqian County. The rising trends of temperature in winter and autumn were higher than the upward trends in spring and summer. （3） The abrupt changes of annual, summer, autumn and winter average temperature were found in the THRHR, LARHR and YARHR, and were detected for the summer and autumn average temperature in the YERHR. The abrupt changes of annual and summer average temperatures were mainly in the late 1990s, while the abrupt changes of autumn and winter average temperatures appeared primarily in the early 1990s and the early 21st century respectively. （4） With the global warming, the diversities of altitude and underlying surface in different parts of the Tibetan Plateau were possibly the main reasons for the high increasing rate of temperature in the THRHR.

PROCESS OF TRANSITION BETWEEN COLD AND WARM PERIODS AND ITS PREDICTION

The oscillation of multi-time scales and the process of transition between cold and warm periods over most parts of China and its 6 regions (the Northeast,North China,Changjiang River Valley,South China,the Southwest,the Northwest) were analyzed with wavelet transformation and by computing the variances of the wavelet components for the temperature grade series during January 191I to February 2001,The prediction model for cold and warm periods has been developed and the trend of cold and warm change in the coming 10 years is predicted.The results show that the oscillation with periods of around 30-40 years was the strongest in the last 100 years and the 3-year oscillation in both winter and summer was also stronger,especially in winter. The transition time of cold and warm periods in terms of winter mean did not coincide with that of annual mean,but the difference between summer mean and annual mean is less.The processes of transition of 6 regions are somewhat different,their main characteristics are that the beginning year of significant warming for 1980s to 1990s was very different for the southern and the northern part of China.It is found that the stronger oscillation with 3-year period causes cooling in Northeast China in recent several winters.The experimental predictions show that the models used in the paper can project the major transition between high and low temperature periods.

Rainfall variability in the Brazilian northeast biomes and their interactions with meteorological systems and ENSO via CHELSA product

Brazilian biomes are home to a significant portion of the world’s biodiversity,with a total of 14%of existing species and still concentrate 20%of the world’s water resources.However,changes in biomes have a direct impact on rainfall patterns and water recycling.Based on this,the objective was to evaluate the variability of rainfall in the four existing biomes in the Northeast Brazil(NEB)and their interaction with the ENSO climate variability mode and regional scale meteorological systems via CHELSA product.For this,monthly rainfall data were used from 1979 to 2013,with a spatial resolution of 1 km×1 km of the CHELSA product,and seasonal and annual rainfall patterns were extracted via boxplot.It was found that the rainy season in the Amazon,Caatinga and Cerrado biomes occurred between January and April,with varying intensities,except for the Atlantic Forest.Such seasonality patterns are associated with the NEB meteorological systems,with emphasis on ITCZ(all Biomes),UTCV(Amazon,Caatinga and Cerrado),Frontal Systems(extreme south of Caatinga,Cerrado and Atlantic Forest)and EWD/TWD in the(Atlantic Forest).In the inter-annual scale,the remarkable influence of ENSO was verified,mainly in the years 1983,1985,1989,1993,1998,2009 and 2012.It is noteworthy that 1985 was the wettest year of the period,with a surplus in all biomes,while the driest year differs between the Amazon(1983),Atlantic Forest and Caatinga(1993)and Cerrado(2012)biomes.The study via orbital product in NEB showed that anthropogenic processes and natural variability interfere with the forms of rain interception in the biomes and hence in rainfall patterns and water recycling in NEB.