Analysis of the characteristics of the harmonics coefficient <Emphasis Type="Italic">J</Emphasis><Subscript>2</Subscript> of the Earth’s gravity field in different periods

The characteristics of the geopotential coefficient J2 in different periods are analyzed using satellite laser ranging data spanning the last 27 years.The satellites used in the analysis are Lageos1 and Lageos2.The variations in J2 are obtained by determining the dynamic orbit.The results show that there are strong seasonal and long-term variations.For different data spans,the seasonal variations agree well in terms of both amplitude and phase.Using all the data,the amplitude and phase of the annual term are 2.5 10-10 and 127°,respectively,while the amplitude and phase of the semiannual term are 0.94 10-10 and 213°,respectively.In the case of long-term variation,the secular variation in J2(J2) is-2.2 10-11 a-1 from 1984 to 2010.J2 differs for the different periods because of interannual variations,such as the "1998 anomaly".Another anomaly may have taken place during 2007-2010.Although the cause of the anomaly is unknown,it is an important observational constraint on the shape of the Earth.     

An analysis of the polar motion series from VLBI observations

From the reduction of 2893 globally distributed astrometric and geodetic VLBI sessions from August 1979 to the end of 1998, coordinates of 722 radio sources at J2000.0, coordinates and velocities of 128 stations at J1997.0 and about 20 years Earth Orientation Parameters were estimated. From the analysis of the resultant polar motion series, the following are demonstrated: (ⅰ) During the VLBI data span the Markowitz wobble is not exhibited. (ⅱ) The amplitudes of both annual and Chandler wobble show temporal variations, with the former being more obvious than the latter. (ⅲ) Wavelet analysis shows that all the signals in the polar motion series are characterized by temporal variation in amplitudes. If we take any signal as strictly periodic, it is impossible to remove it completely from the polar motion series by least-squares fit because the hypothesis of a constant amplitude conflicts with VLBI measurements. (ⅳ) By applying a filter, the secular polar motion was found to be (2.74±0.01) mas/a towards (83.9±0.3) °W longitude, which is smaller in rate and more westward in direction compared with those determined from optical observations or the combination of optical and space geodetic observations.     

Temporal and spatial variation of atmospheric water vapor in the Taklimakan Desert and its surrounding areas

The study of the temporal and spatial variation of atmospheric water vapor has the important significance to show the response to climate change in the Taklimakan Desert. The series of monthly atmospheric water vapor from 1961 to 1998 are reconstructed using the observation data including the precipitation, ground water vapor pressure data over the period of 1961 to 2006 from 27 observation stations in its surrounding areas and meteorological data from the Tazhong station during 1999-2006. Then the relationship between atmospheric water vapor and ground vapor pressure is calculated and validated using the observation data for the period of 1976 to 2006 from 5 sounding stations (Hotan, Kuqa, Ruoqiang, Kashgar, and Minfeng). The temporal and spatial variation of atmospheric water vapor in the Taklimakan Desert and its surrounding areas is studied and then its distribution is generated. Results show that high value zone of atmospheric water vapor is mainly distributed in the northern Taklimakan Desert and the oasis-marginal belt of western desert and the value ranges from 14 to 15 mm. The low value center of atmospheric water vapor is in the hinterland of the desert and the value is only 7―8 mm. The annual variations of atmospheric water vapor show generally the increasing trend. How- ever, the variation of atmospheric water vapor in the surrounding areas and the hinterland of the desert is insignificant during 1961―1986. The atmospheric water vapor changes abruptly after 1986 and increases clearly in the two regions. The variation trend accords with that of the precipitation’s increasing significantly in southern Xinjiang for the recent 50 years. There is great error between the NCEP/NCAR reanalysis data of atmospheric water vapor and real data in theTaklimakan Desert.     

Climatological analysis and modeling of the ionospheric global electron content

In this paper, we calculate the ionospheric global electron content （GEC） from the GPS TEC data along the geographic longitude 120°E during the period of 1996-2004, and investigate the relationship between GEC and 10.7 cm solar radio flux F10.7 and its seasonal dependence with partial correlation analysis. Our results show that GEC is closely correlated with solar activity index F10.7 and is also related with annual and semiannual variations. An empirical GEC model driven by those factors is then to examine the influences of different solar activity proxies for the model input. The results suggest that GEC mainly depends on solar activity and the seasonal variations; the latter is also modulated by solar activity. Furthermore, the magnitude of semiannual variation is a little greater than that of annual variation. Our empirical GEC model is proved to be better than the model proposed by Afraimovich et al.     

Long-term trends in foF2 over Moscow ionosonde station: Its estimate and origins

We introduce a new approach,using the International Reference Ionosphere 2007(IRI-2007)model and observations from the Moscow ionosonde station,to analyze the long-term trends of ionospheric foF2.Possible origins,whether natural or manmade, are discussed.A small but significant residual foF2 trend is found,with-0.76 MHz over the past 50 years,but-0.2 MHz after eliminating the most variations caused by solar and geomagnetic activities and the variational earth’s magnetic field.We find that this slope depends on local time and seasons.There is a pronounced diurnal negative variation in k(annual mean slope of diurnal variations),with much larger absolute values in the morning than during afternoon or evening;the largest k is about-0.0018 per year in spring,and the smallest trend of about-0.0012 per year occurs in winter.Finally,the evidence of crucial influences of geomagnetic activity and the earth’s magnetic field on the observed trends,as emphasized by the IRI-2007 empirical model,is confirmed,and the effect of CO2 contributions to the trend is also discussed,by cooling the thermospheric temperature or recombining the electron density.     

The diurnal variations, semiannual and winter anomalies of the ionospheric TEC based on GPS data in China

With the spherical harmonic (SH) function model and the dual frequency GPS P code phase data from the Crustal Movement Observation Network of China (CMONOC) during the period from year 2000 to 2002, time series of total electron content (TEC) in the area of China is calculated. The diurnal variations, semiannual, and winter anomalies of the ionosphere in the area of China are analyzed and discussed, especially according to the results of year 2001.     

Interannual variation of annual precipitation and urban effect on precipitation in the Beijing region

The large scale character of the interannual variation of precipitation and the urban effect on local annual precipitation anomaly are investigated in this paper based on the 1960-2000 annual precipitation observations at 20 stations in the Beijing region.The results show that:the annual precipitation in the Beijing region possesses the large scale variation character with the linear trend of-1.197/10 yr,which corresponds to a total reduction of 27.82 mm in annual precipitation in the 41 years;the local annual precipitation anomalies(percent of the normal 1960-2000)show a positive center near the urban area,i.e.urban precipitation island(UPI),whose intensity increases with the linear trend of 0.6621%/10 yr,opposite to the interannual trend of large scale precipitation over the Beijing region;changes in the UPI are also associated with the intensity of synoptic processes of precipitation,and when the synoptic processes are strong(wet years),the intensity of UPI strengthens,while the synoptic processes are weak(dry years),and the UPI disappears in the Beijing region.     

Westerly moisture transport to the middle of Himalayas revealed from the high deuterium excess

Previous studies found extremely high d-excess in both ice core and glacial melt water in Dasuopu glacier, Xixiabangma, middle of Himalayas. These values are much higher than the global average and those measured in southwest monsoon precipitation. The d-excess variation in over one year at Nyalam station will clarify this phenomenon. Studies show that the high d-excess is related to the seasonal variation of moisture transport to this region. The d-excess values are low during the southwest monsoon active periods, when moisture originated from the humid ocean surface. The d-excess values are higher in non-monsoon months, when moisture is derived from westerly transport. Winter and spring precipitation accounts for a substantial portion of the annual precipitation, resulting in higher d-excess in the yearly precipitation in the middle of Himalayas than other parts of the southern Tibetan Plateau. This finding reveals that the precipitation in the middle of Himalayas is not purely from southwest monsoon, but a large portion from the westerly transport, which is very important for ice core study in this area.     

An integrative estimation model of summer rainfall-band patterns in China

Three variation indices are defined to objectively and quantitatively represent fluctuations of three rainfall-band patterns in summers in China for the period from 1951 to 2005, and the variation features of these indices are analyzed on both of interdecadal and interannual scales. A new method is proposed to establish an integrative estimation model based on the analysis of rainfall-band indices, and the model is applied to air, ocean factors to estimate their roles on variations of three rainfall-band patterns on different time-scales. The tests of estimation effects show that the fluctuations of three rainfall-band patterns are composed of variations on both significant inter-decadal and interannual scales, of which the interannual variation is mainly influenced by the Elnino/Lanina events, the East Asia monsoon and the ridge locations of subtropical high pressures in western pacific, while the interdecadal variation is mainly controlled by the Pacific decadal oscillation and interdecadal oscillations of the Arctic oscillation, ENSO, Nino3 sea surface temperature and summer monsoon. The estimated results from the integrative estimation model of rainfall-band patterns suggest that the way of estimation first according to each time scale of both the interdecadal and interannual scales, then estimating with an integration, which is proposed in this paper, has an obvious improvement on that without separation of time scales.     

An integrative estimation model of summer rainfall-band patterns in China

Three variation indices are defined to objectively and quantitatively represent fluctuations of three rainfall-band patterns in summers in China for the period from 1951 to 2005, and the variation features of these indices are analyzed on both of interdecadal and interannual scales. A new method is proposed to establish an integrative estimation model based on the analysis of rainfall-band indices, and the model is applied to air, ocean factors to estimate their roles on variations of three rainfall-band patterns on different time-scales. The tests of estimation effects show that the fluctuations of three rainfall-band patterns are composed of variations on both significant inter-decadal and interannual scales, of which the interannual variation is mainly influenced by the Elnino/Lanina events, the East Asia monsoon and the ridge locations of subtropical high pressures in western pacific, while the interdecadal variation is mainly controlled by the Pacific decadal oscillation and interdecadal oscillations of the Arctic oscillation, ENSO, Nino3 sea surface temperature and summer monsoon. The estimated results from the integrative estimation model of rainfall-band patterns suggest that the way of estimation first according to each time scale of both the interdecadal and interannual scales, then estimating with an integration, which is proposed in this paper, has an obvious improvement on that without separation of time scales.     

The utilization of water resources and its variation tendency in Tarim River Basin

Water resources efficient utilization is the key to ecological improvement and economic development in Tarim River Basin. It is necessary to analyze the water resources utilization and its variation tendency in the whole river basin. Based on the monitored data and formation at eight meteorological stations and fifteen hydrological stations, the method of time series, regression analysis are applied to analyzing the water resources utilization and variation trend in the headstreams and mainstream areas especially in recent 10 years. The quantitative results indicate that inflows of the headstream areas have an increasing trend to different extent in the past 40 years. The runoff increasing trend is more significant from1994 to 2002, which show the water resources condition in the headstreams is at an advantage. However, under the condition of water increase with the volume of 25×10^8 m^3 in headstreams in recent 10 years, the mainstream water flowing from the headstreams has increased less than 0.9985×10^8 m^3. In addition, the runoff at the different hydrologic stations along the Tarim River has a significant linear de- creasing trend. It is shown that the degraded trend of ecological environment in the mainstream areas hardly changes even if the Tarim River Basin is in the special water period for ten consecutive years.     

The coral grayness in northern South China Sea and its description of interdecadal variation of precipitation in south China

The interdecadal variation of coral grayness in northern South China Sea （SCS） is studied using the annual mean coral grayness in northern SCS from 1789 to 1992 and annual precipitation at Guangzhou from 1908 to 1992 by Singular Spectrum Analysis （SSA）, correlation analysis, Mann-Kendalrs abrupt change analysis and composite analysis. The interdecadal variation of south China precipitation as reflected by the series of Guangzhou precipitation rebuilt with the coral grayness is discussed. The results show that the variation of coral grayness in SCS has significant terms of tendency, much-weighted interdecadal variation and weak interannual variation. There was a century-scale abrupt change of coral grayness at the end of the 1880s that changed from positive anomalies to negative anomalies. The global field of SST difference corresponding to the point of abrupt change was negative anomalies over the SCS and neighboring northern Indian Ocean, most of central and western Pacific Ocean and coastal areas of the northern Atlantic Ocean. The large-scale distribution of SST anomalies is concomitant with the century-scale abrupt change of coral grayness in SCS. Negative correlation exists between the coral grayness in SCS and precipitation in Guangzhou on the interdecadal scale and the interdecadal precipitation in Guangzhou as reflected by the interdecadal data of SCS coral grayness shows that the interdecadal variation of south China precipitation changes significantly from phase to phase. The current study aims at contributing in the effort of identifying alternative indexes for climate change in south China on the interdecadal scale and beyond.     

Excitation of seasonal polar motion by atmospheric and oceanic angular momentums

A quantitative study on the seasonal polar motion excitated by the atmospheric angular momentum (AAM) and the oceanic angular momentum (0AM) has been carried out using numerical models. The results show that for the prograde and retrograde components of the seasonal polar motion (the annual polar motion and the semiannual polar motion) , the sum of excitations by both the AAM and the 0AM is closer to the observed results rather than that of the AAM only. This reflects a significant contribution of the 0AM to the seasonal polar motion.     

Localized 3D-structural features of dynamic-chemical processes of urban air pollution in Beijing winter

The Beijing City Air Pollution Observation Field Experiment (BECAPEX) is described with emphases on the “point-surface” research approach and composite analysis. The analysis results of measurements from four observation sites across the Beijing urban area from January to March indicate that the overall impact of urban emission sources in the heating season is significant, and the staggered impact of urban emission sources has different features at observation sites over different parts of Beijing in both heating and non-heating seasons. The pollutants NOx, SO2 and CO in the urban boundary layer have the in-phase variation features over a large area. 03 concentrations at different sites have the same variation trend but its change is reversed phases with above pollutants. The pollutants over the urban area in heating and non-heating seasons also have the synchronous variation trend. The comprehensive sounding of BECAPEX indicates that pollutants and aerosol verticalprofiles are closely correlated to the vertical structure of the large-scale inversion layer in the urban boundary layer over the urban area. The localized 3D-structural features of local urban polluting processes associated with the peripheral areas are discussed with a “point-surface” comprehensive sounding technique.     

Relationship between calcium and atmospheric dust recorded in Guliya ice core

By the analyses of Guliya ice core on the Tibetan Plateau, it was found that the calcium (Ca^2 ) originated from the terrestrial source is the main cation of soluble aerosol and a good proxy of the atmospheric component and environment in the mountain ice core located in the mid-low latitude arid regions. Evident variation of Ca^2 concentration has been found in the Guliya ice core since the Last lnterglaciation with two relatively strong increase periods and two weak increase periods. These variations are generally related to climatic changes: high Ca^2 concentration periods coincide with cold periods and low Ca^2 concentration periods coincide with warm periods. However, Ca^2 concentration does not always decrease (increase) with climate warming (cooling). The magnitude and phase of Ca^2 concentration does not always match temperature either. The changes of atmospheric circulation, land surface condition and atmospheric humidity might be important factors which influence Ca^2 concentration besides temperature.     

The interdecadal trend and shift of dry/wet over the central part of North China and their relationship to the Pacific Decadal Oscillation （PDO）

Based on monthly precipitation and monthly mean surface air temperature (SAT),the dry/wet trends and shift of the central part of North China and their relationship to the Pacific Decadal Oscillation (PDO) from 1951 to 2005 have been analyzed through calculating surface wetness index (SWI). The results indicate that there was a prominent drying trend and an abrupt change in the analysis period. A per-sistent warming period with less precipitation from the mid and late 1970s to present was found,and a shift process exists from the wet to the dry in the central part of North China during 1951-2005. The transition is located in the mid to late 1970s,which should be related to the shift variation of large-scale climate background. The correlation analysis has brought about a finding of significant correlativity between PDO index (PDOI) and SAT,precipitation and SWI in this region. The correlation exhibits that the positive phase of PDOI (warm PDO phase) matches warming,less precipitation and the drought period,and the negative PDOI phase corresponds to low SAT,more precipitation and the wet period. The duration of various phases is more than 25 years. The decadal variation of sea surface temperature (SST) in the North Pacific Ocean is one of the possible causes in forming the decadal dry/wet trend and shift of the central part of North China.     

Analysis on the source of raw material of the celadon bodies from Zhanggongxiang kiln and Qingliangsi kiln by PIXE

The proton induced X-ray emission (PIXE) is used to measure the chemical ingredients of seven main elements of each sample of celadon body from Qingliangsi kiln in Baofeng County and Zhanggongxiang kiln in Ruzhou City. The PIXIE data are then analyzed by fuzzy cluster method, and the trend cluster diagram is obtained to determine their relation of classification and provenance. The result shows that the producing area of raw material of Ru porcelain bodies is concentrated in Qingliangsi kiln, while that of celadon bodies is slightly scattered in Zhanggongxiang kiln. The raw material origin of Ru porcelain bodies from Qingliangsi kiln in Baofeng County is different from that of Zhang-gongxiang kiln in Ruzhou City. The materials of Ru Guan porcelain bodies and Ru Civil porcelain bodies in Qingliangsi kiln are basically the same.     

Forcing mechanisms for East-Asia monsoonal variations during the late pleistocene

Based on the climate records derived from loess deposits in north-central China, the characteristics of the East-Asia paleomonsoonal changes during the Late Pleistocene are summarized as follows: (ⅰ) The 0.1_Ma climate period is predominant in both summer and winter monsoonal changes over East Asia; (ⅱ) The East-Asia monsoonal variation is different from the Indian monsoon during the Late Pleistocene; (ⅲ) There is a ～5_ka time lag of the East-Asia monsoon changes relative to the theoretically calculated solar radiation changes; (ⅳ) There is a general trend toward increase in winter monsoon and decrease in summer monsoon in the last glaciation; (ⅴ) In the East-Asia monsoonal region, the amplitude of glacial-to-interglacial cycles shows a remarkable increase from south to north. To explain these characteristics, a conceptual model is developed and the forcing of global ice volume variations in the monsoonal history is emphasized.     

Low-frequency sea level variation and its correlation with climate events in the Pacific

Global mean sea level(GMSL) has not only significant secular trend and seasonal variations,but also inter-annual and decadal variations.This paper reconstructs the time series of GMSL variations between 1948 and 2007 by combining satellite altimeter measurements and tide gauge observations.Based on the time series,the acceleration of GMSL rise in the second half of 20th century is estimated to be 0.010±0.009 mm/a 2,and multi-scale low frequency sea level oscillations including decadal variations are detected,and the high-rate of GMSL rise during 1993-2003 is locate in the ascending phase of low frequency oscillation.Then,using the reconstructed GMSL time series after removing the secular trend from satellite altimetry and tide gauges measurements,it shows that low frequency signal of sea level variation has strong correlations with the index of El Ni o/Southern Oscillation(ENSO) and Pacific Decadal Oscillation(PDO).But in several time periods,they have large difference due to effects of both high frequency occurrence of El Ni o and La Ni a phenomenon and short term switch of PDO events.     

Statistical property of the Chandler wobble excitation function

The Chandler wobble excitation function (hereinafter, geodetic excitation) is obtained by removing the seasonal components and low frequency components with periods from several years to decades from the polar motion excitation function derived from SPACE2002 series. The geophysical excitation functions of the individual AAM, OAM, HAM, and two combined excitations of the AAM OAM and AAM OAM HAM at ld, 5d, lm and 3m intervals are statistically tested for the hypothesis of the normality, and then tested for the hypotheses of identical distribution between the geodetic and the geophysical excitations. The results show that, among the total 16 components of the two combined excitation functions at ld, 5d, lm and 3m intervals, most follow random normal processes, the hypotheses of identical distribution between the geodetic excitation and the two combined excitation are acceptable, while most of the hypotheses of identical distribution between the geodetic excitation and the individual excitations of the AAM, OAM, and HAM are rejectable. These results elucidate from a new point of view, that the excitations from AAM, OAM, and HAM are the main sources of the Chandler wobble, and the Chandler wobble excitation function is of a random normal property.