Showing papers in "Science China-earth Sciences in 2014"

Mechanism for the formation of the January 2013 heavy haze pollution episode over central and eastern China

Abstract: In January 2013, a long-lasting episode of severe haze occurred in central and eastern China, and it attracted attention from all sectors of society. The process and evolution of haze pollution episodes were observed by the "Forming Mechanism and Control Strategies of Haze in China" group using an intensive aerosol and trace gases campaign that simultaneously obtained data at 11 ground-based observing sites in the CARE-China network. The characteristics and formation mechanism of haze pollution episodes were discussed. Five haze pollution episodes were identified in the Beijing-Tianjin-Hebei (Jing-Jin-Ji) area; the two most severe episodes occurred during 9-15 January and 25-31 January. During these two haze pollution episodes, the maximum hourly PM2.5 mass concentrations in Beijing were 680 and 530 μg m-3, respectively. The process and evolution of haze pollution episodes in other major cities in the Jing-Jin-Ji area, such as Shijiazhuang and Tianjin were almost the same as those observed in Beijing. The external cause of the severe haze episodes was the unusual atmospheric circulation, the depression of strong cold air activities and the very unfavorable dispersion due to geographical and meteorological conditions. However, the internal cause was the quick secondary transformation of primary gaseous pollutants to secondary aerosols, which contributed to the "explosive growth" and "sustained growth" of PM2.5. Particularly, the abnormally high amount of nitric oxide (NO x ) in the haze episodes, produced by fossil fuel combustion and vehicle emissions, played a direct or indirect role in the quick secondary transformation of coal-burning sulphur dioxide (SO2) to sulphate aerosols. Furthermore, gaseous pollutants were transformed into secondary aerosols through heterogeneous reactions on the surface of fine particles, which can change the particles size and chemical composition. Consequently, the proportion of secondary inorganic ions, such as sulphate and nitrate, gradually increased, which enhances particle hygroscopicity and thereby accelerating formation of the haze pollution.

Meteorological conditions for the persistent severe fog and haze event over eastern China in January 2013

Abstract: In January 2013, a severe fog and haze event (FHE) of strong intensity, long duration, and extensive coverage occurred in eastern China. The present study investigates meteorological conditions for this FHE by diagnosing both its atmospheric background fields and daily evolution in January 2013. The results show that a weak East Asian winter monsoon existed in January 2013. Over eastern China, the anomalous southerly winds in the middle and lower troposphere are favorable for more water vapor transported to eastern China. An anomalous high at 500 hPa suppresses convection. The weakened surface winds are favorable for the fog and haze concentrating in eastern China. The reduction of the vertical shear of horizontal winds weakens the synoptic disturbances and vertical mixing of atmosphere. The anomalous inversion in near-surface increases the stability of surface air. All these meteorological background fields in January 2013 were conducive to the maintenance and development of fog and haze over eastern China. The diagnosis of the daily evolution of the FHE shows that the surface wind velocity and the vertical shear of horizontal winds in the middle and lower troposphere can exert dynamic effects on fog and haze. The larger (smaller) they are, the weaker (stronger) the fog and haze are. The thermodynamic effects include stratification instability in middle and lower troposphere and the inversion and dew-point deficit in near-surface. The larger (smaller) the stratification instability and the inversion are, the stronger (weaker) the fog and haze are. Meanwhile, the smaller (larger) the dewpoint deficit is, the stronger (weaker) the fog and haze are. Based on the meteorological factors, a multi-variate linear regression model is set up. The model results show that the dynamic and thermodynamic effects on the variance of the fog and haze evolution are almost the same. The contribution of the meteorological factors to the variance of the daily fog and haze evolution reaches 0.68, which explains more than 2/3 of the variance.

Analysis of long-term variations of fog and haze in China in recent 50 years and their relations with atmospheric humidity

Abstract: Our analysis of fog and haze observations from the surface weather stations in China in recent 50 years (from 1961 to 2011) shows that the number of fog days has experienced two-stage variations, with an increasing trend before 1980 and a decreasing trend after 1990. Especially, an obvious decreasing trend after 1990 can be clearly seen, which is consistent with the decreasing trend of the surface relative humidity. However, the number of haze days has demonstrated an increasing trend. As such, the role of reduction of atmospheric relative humidity in the transition process from fog into haze has been further investigated. It is estimated that the mean relative humidity of haze days is about 69%, lower than previously estimated, which implies that it is more difficult for the haze particles to transform into fog drops. This is possibly one of the major environmental factors leading to the reduction of number of fog days. The threshold of the relative humidity for transition from fog into haze is about 82%, also lower than previously estimated. Thus, the reduction of the surface relative humidity in China mainly due to the increase of the surface temperature and the saturation specific humidity may exert an obvious impact on the environmental conditions for the formations of fog and haze. In addition, our investigation of the relationship between haze and visibility reveals that with the increase of haze days, the visibility has declined markedly. Since 1961, the mean visibility has dropped from 4-10 to 2-4 km, about a half of the previous horizontal distance of visibility.

Modeling study of regional severe hazes over mid-eastern China in January 2013 and its implications on pollution prevention and control

Abstract: The Nested Air Quality Prediction Model System (NAQPMS) was used to investigate the temporal and spatial variations of PM 2.5 over tropospheric central eastern China in January 2013. The impact of regional transport and its implications on pollution prevention and control were also examined. Comparison between simulated and observed PM 2.5 showed NAQPMS was able to reproduce the evolution of PM 2.5 during heavy haze episodes. The results indicated that regional transport of PM 2.5 played an important role in regional haze episodes in the city cluster including Hebei, Beijing and Tianjin (HBT). The cross-city clusters transport outside HBT and transport among cities inside HBT contributed 20%-35% and 26%-35% of PM 2.5 as compared with local emission, in HBT respectively. To meet the Air Quality Standards for Grade Ⅱ, 90%, 90% and 65% of emissions would have to be cut down in Hebei, Tianjin and Beijing, if non-control strategy was taken in the surrounding city clusters of HBT. This implicated that control of emissions in one city cluster is not sufficient to reduce regional haze events, and joint efforts among city clusters are essential. Besides regional transports, two-way feedback between boundary-layer evolution and PM 2.5 also significantly contributed to the formation of heavy hazes, which contributed 30% of monthly average PM 2.5 concentration in HBT.

Preliminary assessment of the navigation and positioning performance of BeiDou regional navigation satellite system

Abstract: BeiDou regional navigation satellite system (BDS) also called BeiDou-2 has been in full operation since December 27, 2012. It consists of 14 satellites, including 5 satellites in Geostationary Orbit (GEO), 5 satellites in Inclined Geosynchronous Orbit (IGSO), and 4 satellites in Medium Earth Orbit (MEO). In this paper, its basic navigation and positioning performance are evaluated preliminarily by the real data collected in Beijing, including satellite visibility, Position Dilution of Precision (PDOP) value, the precision of code and carrier phase measurements, the accuracy of single point positioning and differential positioning and ambiguity resolution (AR) performance, which are also compared with those of GPS. It is shown that the precision of BDS code and carrier phase measurements are about 33 cm and 2 mm, respectively, which are comparable to those of GPS, and the accuracy of BDS single point positioning has satisfied the design requirement. The real-time kinematic positioning is also feasible by BDS alone in the opening condition, since its fixed rate and reliability of single-epoch dual-frequency AR is comparable to those of GPS. The accuracy of BDS carrier phase differential positioning is better than 1 cm for a very short baseline of 4.2 m and 3 cm for a short baseline of 8.2 km, which is on the same level with that of GPS. For the combined BDS and GPS, the fixed rate and reliability of single-epoch AR and the positioning accuracy are improved significantly. The accuracy of BDS/GPS carrier phase differential positioning is about 35 and 20 % better than that of GPS for two short baseline tests in this study. The accuracy of BDS code differential positioning is better than 2.5 m. However it is worse than that of GPS, which may result from large code multipath errors of BDS GEO satellite measurements.

Development of a national VNIR soil-spectral library for soil classification and prediction of organic matter concentrations

Abstract: Soil visible-near infrared diffuse reflectance spectroscopy (vis-NIR DRS) has become an important area of research in the fields of remote and proximal soil sensing. The technique is considered to be particularly useful for acquiring data for soil digital mapping, precision agriculture and soil survey. In this study, 1581 soil samples were collected from 14 provinces in China, including Tibet, Xinjiang, Heilongjiang, and Hainan. The samples represent 16 soil groups of the Genetic Soil Classification of China. After air-drying and sieving, the diffuse reflectance spectra of the samples were measured under laboratory conditions in the range between 350 and 2500 nm using a portable vis-NIR spectrometer. All the soil spectra were smoothed using the Savitzky-Golay method with first derivatives before performing multivariate data analyses. The spectra were compressed using principal components analysis and the fuzzy k-means method was used to calculate the optimal soil spectral classification. The scores of the principal component analyses were classified into five clusters that describe the mineral and organic composition of the soils. The results on the classification of the spectra are comparable to the results of other similar research. Spectroscopic predictions of soil organic matter concentrations used a combination of the soil spectral classification with multivariate calibration using partial least squares regression (PLSR). This combination significantly improved the predictions of soil organic matter (R 2 = 0.899; RPD = 3.158) compared with using PLSR alone (R 2 = 0.697; RPD = 1.817).

A multi-resolution global land cover dataset through multisource data aggregation

Abstract: Recent developments of 30 m global land characterization datasets (e.g., land cover, vegetation continues field) represent the finest spatial resolution inputs for global scale studies. Here, we present results from further improvement to land cover mapping and impact analysis of spatial resolution on area estimation for different land cover types. We proposed a set of methods to aggregate two existing 30 m resolution circa 2010 global land cover maps, namely FROM-GLC (Finer Resolution Observation and Monitoring-Global Land Cover) and FROM-GLC-seg (Segmentation), with two coarser resolution global maps on development, i.e., Nighttime Light Impervious Surface Area (NL-ISA) and MODIS urban extent (MODIS-urban), to produce an improved 30 m global land cover map—FROM-GLC-agg (Aggregation). It was post-processed using additional coarse resolution datasets (i.e., MCD12Q1, GlobCover2009, MOD44W etc.) to reduce land cover type confusion. Around 98.9% pixels remain 30 m resolution after some post-processing to this dataset. Based on this map, majority aggregation and proportion aggregation approaches were employed to create a multi-resolution hierarchy (i.e., 250 m, 500 m, 1 km, 5 km, 10 km, 25 km, 50 km, 100 km) of land cover maps to meet requirements for different resolutions from different applications. Through accuracy assessment, we found that the best overall accuracies for the post-processed base map (at 30 m) and the three maps subsequently aggregated at 250 m, 500 m, 1 km resolutions are 69.50%, 76.65%, 74.65%, and 73.47%, respectively. Our analysis of area-estimation biases for different land cover types at different resolutions suggests that maps at coarser than 5 km resolution contain at least 5% area estimation error for most land cover types. Proportion layers, which contain precise information on land cover percentage, are suggested for use when coarser resolution land cover data are required.

Evolution of the monsoon and dry climate in East Asia during late Cenozoic: A review

Abstract: Climate in Eastern Asia is composed of monsoon climate in the east, arid and semi-arid climate in the north and west, and the cold and dry climate of Qinghai-Tibetan Plateau in the southwest. The underlying causes for the evolution of East Asian climate during late Cenozoic have long been investigated and debated, particularly with regards to the role played by the Qinghai-Tibetan Plateau uplift and the global cooling. In this paper, we reviewed major research developments in this area, and summarized the important results. Based on a synthesis of data, we propose that the Qinghai-Tibetan Plateau uplift alone cannot fully explain the formation of monsoon and arid climates in Eastern Asia during the past 22-25 Ma. Other factors such as the global ice volume and high-latitude temperature changes have also played a vital role. Moreover, atmospheric CO2 changes may have modulated the monsoon and dry climate changes by affecting the location of the inter-tropical convergence zone (ITCZ), which controls the monsoon precipitation zone and the track of the East Asian winter monsoon during late Cenozoic. The integration of high-resolution geological record and numerical paleoclimate modeling could make new contributions to understanding the climate evolution and variation in eastern Asia in future studies. It could facilitate the investigation of the regional differences in East Asian environmental changes and the asynchronous nature between the uplift of Qinghai-Tibetan Plateau and their climatic effects. These would be the keys to understanding underlying driving forces for the evolution of the East Asian climate.

Molecular simulation of the CH 4 /CO 2 /H 2 O adsorption onto the molecular structure of coal

Abstract: Clarification of the molecular mechanism underlying the interaction of coal with CH4, CO2, and H2O molecules is the basis for an in-depth understanding of the states of fluid in coal and fluid-induced coal swelling/contraction. In terms of instrumental analysis, molecular simulation technology based on molecular mechanics/dynamics and quantum chemistry is a powerful tool for revealing the relationship between the structure and properties of a substance and understanding the interaction mechanisms of physical-chemical systems. In this study, the giant canonical ensemble Monte Carlo (GCMC) and molecular dynamics (MD) methods were applied to investigate the adsorption behavior of a Yanzhou coal model (C222H185N3O17S5). We explored the adsorption amounts of CH4, CO2, and H2O onto Yanzhou coal, the adsorption conformation, and the impact of oxygen-containing functional groups. Furthermore, we revealed the different adsorption mechanisms of the three substances using isosteric heat of adsorption and energy change data. (1) The adsorption isotherms of the mono-component CH4, CO2, and H2O were consistent with the Langmuir model, and their adsorption amounts showed an order of CH4 CO2>CH4. In addition, at higher temperatures, the isosteric heat of adsorption decreased; pressure had no significant effect on the heat of adsorption. (3) CH4 molecules displayed an aggregated distribution in the pores, whereas CO2 molecules were cross arranged in pairs. Regarding H2O molecules, under the influence of hydrogen bonds, the O atom pointed to surrounding H2O molecules or the H atoms of coal molecules in a regular pattern. The intermolecular distances of the three substances were 0.421, 0.553, and 0.290 nm, respectively. The radial distribution function (RDF) analysis showed that H2O molecules were arranged in the most compact fashion, forming a tight molecular layer. (4) H2O molecules showed a significantly stratified distribution around oxygen-containing functional groups on the coal surface, and the bonding strength showed a descending order of hydroxyl> carboxyl>carbonyl. In contrast, CO2 and CH4 showed only slightly stratified distributions. (5) After the adsorption of CH4, CO2, and H2O, the total energy, the energy of valence electrons, and the non-bonding interaction of the system in the Yanzhou coal model all decreased. The results regarding the decrease in the total energy of the system indicated an order of H2O>CO2>CH4 in terms of the adsorption priority of the Yanzhou coal model. The results regarding the decrease in the energy of valence electrons showed that under certain geological conditions, a pressure-induced “coal strain” could lead to a structural rearrangement during the interaction of coal with fluid to form a more stable conformation, which might be the molecular mechanism of coal swelling resulting from the interaction between fluid and coal. An analysis of the contribution of Van der Waals forces, electrostatic interactions and hydrogen bonds to the decrease in non-bonding interactions revealed the mechanism underlying the interactions between coal molecules and the three substances. The interaction between coal molecules and CH4 consisted of typical physical adsorption, whereas that between coal molecules and CO2 consisted mainly of physical adsorption combined with weak chemical adsorption. The interaction between coal molecules and H2O is physical and chemical.

Thinning and destruction of the cratonic lithosphere: A global perspective

Abstract: It has been proposed that the North China Craton (NCC) was thinned up to a thickness of >100 km during the Phanerozoic, and underwent an associated craton destruction. Evidently, it is an important topic worthy of future study to understanding the mechanism of cratonic destruction and its role played in the continental evolution. After synthesized the global cratons of India, Brazil, South Africa, Siberia, East Europe (Baltic) and North America, we found that lithospheric thinning is common in the cratonic evolution, but it is not always associated with craton destruction. Most cratons was thinned by thermal erosion of mantle plume or mantle upwelling, which, however, may not cause craton destruction. Based on the studies of the North American and North China Cratons, we suggest that oceanic subduction plays an important role in caton destruction. Fluids or melts released by dehydration of the subducted slabs metasomatize the mantle wedge above and trigger extensive partial melting. More importantly, the metasomatized mantle lost its original rigidity and make craton easier to be deformed and then to be destoyed. Therefore, we suggest that the widespread crust-derived granite and large-scale ductile deformation within the continental crust can be regarded as the petrological and structural indicators of craton destruction, respectively.

Quantitative characterization of reservoir space in the Lower Silurian Longmaxi Shale, southern Sichuan, China

Abstract: Based on the drilling data of the Upper Ordovician Wufeng Shale and the Lower Silurian Longmaxi Shale in southern Sichuan Basin, the construction of matrix pores and the development condition of fractures in a marine organic-rich shale are quantitatively evaluated through the establishment of the reservoir petrophysical models and porosity mathematical models. Our studies show that there are four major characteristics of the Longmaxi Shale confirmed by the quantitative characterization: (1) the pore volume of per unit mass is the highest in organic matter, followed in clay minerals, finally in brittle minerals; (2) the porosity of the effective shale reservoir is moderate and equal to that of the Barnett Shale, and the main parts of the shale reservoir spaces are interlayer pores of clay minerals and organic pores; (3) the porosity of the organic-rich shale is closely related to TOC and brittle mineral/clay mineral ratio, and mainly increases with TOC and clay mineral content; (4) fractures are developed in this black shale, and are mainly micro ones and medium-large ones. In the Longmaxi Shale, the fracture density increases from top to bottom, reflecting the characteristics with high brittle mineral content, high Young’s modulus, low Poisson’s ratio and high brittleness at its bottom.

Toward a stepwise Kwangsian Orogeny

Abstract: The Kwangsian Orogeny originated along the southeast coast of China and stepwise developed in a northwest direction. It includes two stages, a long locally varying uplift from the Late Ordovician to the early Silurian and a finally tectonic movement near the Silurian and Devonian transition. The Kwangsian uplift event shows a stepwise delay northwestwards from the southeastern coast area in Nemagraptus gracilis Biozone (Sa1) to the south side of the Xuefeng Mountains in or later than Cystograptus vesiculosus Biozone (R3) to Coronograptus cyphus Biozone (R4). In the southern of Yangtze Platform, the Yichang Uplift was droved by the Kwangsian Orogeny forming a diachronous stratigraphical break through Rhuddanian and Aeronian. The distribution of the early Telychian lower marine red beds indicates a northwestward increase of the Cathaysian Oldland. Stratigraphical evidence may explain why the Kwangsian movement was marked by an angular disconformity during the Pridoli to earliest Devonian interval.

Mesozoic tectono-magmatic activities in South China: Retrospect and prospect

Abstract: The South China Block was formed through the collisional orogeny between the Cathaysia Block and the Yangtze Block in the Early Neoproterozoic. The northern, western and southern sides of the South China Block were affected by disappearance of the Paleo-Tethyan Ocean during the Paleozoic. The southern and northern sides of the South China Block were respectively collided with the Indo-China Block and North China Block in the latest Paleozoic to form the basic framework of the Eastern China. The Eastern China has been affected by the westward subduction of the Pacific Plate since the Mesozoic. Therefore, the South China Block was influenced by the three major tectonic systems, leading to a superposed compound tectonics. The comparative study of the Mesozoic geology between the South China Block and its surrounding areas suggests that although the Mesozoic South China Block was adjacent to the subduction zone of the western Pacific, no juvenile arc-type crust has been found in the eastern margin. The main Mesozoic geology in South China is characterized by reworking of ancient continental margins to intracontinental tectonics, lacking oceanic arc basalts and continental arc andesites. Therefore, a key to understanding of the Mesozoic geology in South China is to determine the temporal-spatial distribution and tectonic evolution of Mesozoic magmatic rocks in this region. This paper presents a review on the tectonic evolution of the South China Block through summarizing the magmatic rock records from the compressional to extensional tectonic process with the transition at the three juncture zones and using the deformation and geophysic data from the deep part of the South China continental lithosphere. Our attempt is to promote the study of South Chinas geology and to make it as a typical target for development of plate tectonic theory.

Climate change regionalization in China (1961-2010)

Abstract: Since climatic condition is the important foundation for human subsistence and development and the key factor in sustainable development of economy and society, climate change has been a global issue attracting great attentions of politicians, scientists, governments, and the public alike throughout the world. Existing climate regionalization in China aims to characterize the regional differences in climate based on years of the mean value of different climate indexes. However, with the accelerating climate change nowadays, existing climate regionalization cannot represent the regional difference of climate change, nor can it reflect the disasters and environmental risks incurred from climate changes. This paper utilizes the tendency value and fluctuation value of temperature and precipitation from 1961 to 2010 to identify the climate change quantitatively, and completes the climate change regionalization in China (1961-2010) with county administrative regionalization as the unit in combination with Chinas terrain feature. Level-I regionalization divides Chinas climate change (1961-2010) into five tendency zones based on the tendency of temperature and precipitation, which are respectively Northeast China-North China warm-dry trend zone, East China-Central China wet-warm trend zone, Southwest China-South China dry-warm trend zone, Southeast TibetSouthwest China wet-warm trend zone, and Northwest China-Qinghai-Tibet Plateau warm-wet trend zone; level-II regionalization refers to fourteen fluctuation regions based on level-I regionalization according to the fluctuation of temperature and precipitation.

Source apportionment and secondary organic aerosol estimation of PM 2.5 in an urban atmosphere in China

Abstract: PM2.5 is the key pollutant in atmospheric pollution in China. With new national air quality standards taking effect, PM2.5 has become a major issue for future pollution control. To effectively prevent and control PM2.5, its emission sources must be precisely and thoroughly understood. However, there are few publications reporting comprehensive and systematic results of PM2.5 source apportionment in the country. Based on PM2.5 sampling during 2009 in Shenzhen and follow-up investigation, positive matrix factorization (PMF) analysis has been carried out to understand the major sources and their temporal and spatial variations. The results show that in urban Shenzhen (University Town site), annual mean PM2.5 concentration was 42.2 μg m−3, with secondary sulfate, vehicular emission, biomass burning and secondary nitrate as major sources; these contributed 30.0%, 26.9%, 9.8% and 9.3% to total PM2.5, respectively. Other sources included high chloride, heavy oil combustion, sea salt, dust and the metallurgical industry, with contributions between 2%–4%. Spatiotemporal variations of various sources show that vehicular emission was mainly a local source, whereas secondary sulfate and biomass burning were mostly regional. Secondary nitrate had both local and regional sources. Identification of secondary organic aerosol (SOA) has always been difficult in aerosol source apportionment. In this study, the PMF model and organic carbon/elemental carbon (OC/EC) ratio method were combined to estimate SOA in PM2.5. The results show that in urban Shenzhen, annual SOA mass concentration was 7.5 μg m−3, accounting for 57% of total organic matter, with precursors emitted from vehicles as the major source. This work can serve as a case study for further in-depth research on PM2.5 pollution and source apportionment in China.

Addressing the issue of fog and haze: A promising perspective from meteorological science and technology

Abstract: Fog and haze are two kinds of weather phenomena. Fog is referred to as water droplets suspended in the air near earths surface, which reduces the visibility to less than 1 km. A fog consisting of ice crystals is called ice fog. Haze is the particles suspended in the air that reduce visibility by scattering the light, and is usually a mixture of aerosol and photochemical smog. Fog and haze usually coexist. The occurrence and evolution of haze and fog are closely related with meteorological conditions.

Land cover mapping using time series HJ-1/CCD data

Abstract: It is very difficult to have remote sensing data with both high spatial resolution and high temporal frequency; thus, two categories of land-use mapping methodology have been developed separately for coarser resolution and finer resolution data. The first category uses time series of data to retrieve the variation of land surface for classification, which are usually used for coarser resolution data with high temporal frequency. The second category uses fine spatial resolution data to classify different land surface. With the launch of Chinese satellite constellation HJ-1in 2008, four 30 m spatial resolution CCDs with about 360 km coverage for each one onboard two satellites made a revisit period of two days, which brought a new type of data with both high spatial resolution and high temporal frequency. Therefore, by taking the spatiotemporal advantage of HJ-1/CCD data we propose a new method for finer resolution land cover mapping using the time series HJ-1/CCD data, which can greatly improve the land cover mapping accuracy. In our two study areas, the very high resolution remote sensing data within Google Earth are used to validate the land cover mapping results, which shows a very high mapping accuracy of 95.76% and 83.78% and a high Kappa coefficient of 0.9423 and 0.8165 in the Dahuofang area of Liaoning Province and the Heiquan area of Gansu Province respectively.

High-resolution remote sensing mapping of global land water

Abstract: Land water, one of the important components of land cover, is the indispensable and important basic information for climate change studies, ecological environment assessment, macro-control analysis, etc. This article describes the overall study on land water in the program of global land cover remote sensing mapping. Through collection and processing of Landsat TM/ETM+, Chinas HJ-1 satellite image, etc., the program achieves an effective overlay of global multi-spectral image of 30 m resolution for two base years, namely, 2000 and 2010, with the image rectification accuracy meeting the requirements of 1: 200000 mapping and the error in registration of images for the two periods being controlled within 1 pixel. The indexes were designed and selected reasonably based on spectral features and geometric shapes of water on the scale of 30 m resolution, the water information was extracted in an elaborate way by combining a simple and easy operation through pixel-based classification method with a comprehensive utilization of various rules and knowledge through the object-oriented classification method, and finally the classification results were further optimized and improved by the human-computer interaction, thus realizing high-resolution remote sensing mapping of global water. The completed global land water data results, including Global Land 30-water 2000 and Global Land 30-water 2010, are the classification results featuring the highest resolution on a global scale, and the overall accuracy of self-assessment is 96%. These data are the important basic data for developing relevant studies, such as analyzing spatial distribution pattern of global land water, revealing regional difference, studying space-time fluctuation law, and diagnosing health of ecological environment.

Characterization, controlling, and reduction of uncertainties in the modeling and observation of land-surface systems

Abstract: Uncertainty is one of the greatest challenges in the quantitative understanding of land-surface systems. This paper discusses the sources of uncertainty in land-surface systems and the possible means to reduce and control this uncertainty. From the perspective of model simulation, the primary source of uncertainty is the high heterogeneity of parameters, state variables, and near-surface atmospheric states. From the perspective of observation, we first utilize the concept of representativeness error to unify the errors caused by scale representativeness. The representativeness error also originates mainly from spatial heterogeneity. With the aim of controlling and reducing uncertainties, here we demonstrate the significance of integrating modeling and observations as they are complementary and propose to treat complex land-surface systems with a stochastic perspective. In addition, through the description of two modern methods of data assimilation, we delineate how data assimilation characterizes and controls uncertainties by maximally integrating modeling and observational information, thereby enhancing the predictability and observability of the system. We suggest that the next-generation modeling should depict the statistical distribution of dynamic systems and that the observations should capture spatial heterogeneity and quantify the representativeness error of observations.

Improvement of snow depth retrieval for FY3B-MWRI in China

Abstract: The primary objective of this work is to develop an operational snow depth retrieval algorithm for the FengYun3B Microwave Radiation Imager (FY3B-MWRI) in China. Based on 7-year (2002–2009) observations of brightness temperature by the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and snow depth from Chinese meteorological stations, we develop a semi-empirical snow depth retrieval algorithm. When its land cover fraction is larger than 85%, we regard a pixel as pure at the satellite passive microwave remote-sensing scale. A 1-km resolution land use/land cover (LULC) map from the Data Center for Resources and Environmental Sciences, Chinese Academy of Sciences, is used to determine fractions of four main land cover types (grass, farmland, bare soil, and forest). Land cover sensitivity snow depth retrieval algorithms are initially developed using AMSR-E brightness temperature data. Each grid-cell snow depth was estimated as the sum of snow depths from each land cover algorithm weighted by percentages of land cover types within each grid cell. Through evaluation of this algorithm using station measurements from 2006, the root mean square error (RMSE) of snow depth retrieval is about 5.6 cm. In forest regions, snow depth is underestimated relative to ground observation, because stem volume and canopy closure are ignored in current algorithms. In addition, comparison between snow cover derived from AMSR-E and FY3B-MWRI with Moderate-resolution Imaging Spectroradiometer (MODIS) snow cover products (MYD10C1) in January 2010 showed that algorithm accuracy in snow cover monitoring can reach 84%. Finally, we compared snow water equivalence (SWE) derived using FY3B-MWRI with AMSR-E SWE products in the Northern Hemisphere. The results show that AMSR-E overestimated SWE in China, which agrees with other validations.

Conceptual study of lunar-based SAR for global change monitoring

Abstract: As an active microwave remote sensing imaging sensor, Synthetic Aperture Radar (SAR) plays an important role in earth observation. Here we establish a SAR system based on the platform of the moon. This will aid large-scale, constant, and long-term dynamic Earth observations to better meet the needs of global change research and to complement the space borne and airborne earth observations. Lunar-based SAR systems have the characteristics of high resolution and wide swath width. The swath width could be thousands of kilometers in the stripe mode and it could cover 40% of earth’s surface with 10 meters or even higher spatial resolution in the scanning mode. Using the simplified observation model, here we quantitatively analyze the spatial resolution and coverage area of lunar-based SAR and simulate the observation on the Qinghai-Tibet plateau and the Amazon plain. The results show that this system could provide near 100% daily coverage of the Qinghai-Tibet plateau, whereas 40% to 70% daily coverage of the Amazon plain. Lunar-based SAR could provide large-scale, long-term and stable time series data in order to support future research of global change.

Diagenetic fluid evolution and water-rock interaction model of carbonate cements in sandstone：An example from the reservoir sandstone of the Fourth Member of the Xujiahe Formation of the Xiaoquan-Fenggu area, Sichuan Province, China

Abstract: Carbonate cement is the most abundant cement type in the Fourth Member of the Xujiahe Formation in the Xiaoquan-Fenggu area of the West Sichuan Depression. Here we use a systematic analysis of carbonate cement petrology, mineralogy, carbon and oxygen isotope ratios and enclosure homogenization temperatures to study the precipitation mechanism, pore fluid evolution, and distribution of different types of carbonate cement in reservoir sand in the study area. Crystalline calcite has relatively heavy carbon and oxygen isotope ratios (δ13C = 2.14‰, δ18O = −5.77‰), and was precipitated early. It was precipitated directly from supersaturated alkaline fluid under normal temperature and pressure conditions. At the time of precipitation, the fluid oxygen isotope ratio was very light, mainly showing the characteristics of a mixed meteoric water-seawater fluid (δ18O = −3‰), which shows that the fluid during precipitation was influenced by both meteoric water and seawater. The calcite cement that fills in the secondary pores has relatively lighter carbon and oxygen isotope ratios (δ13C = −2.36‰, δ18O = −15.68‰). This cement was precipitated late, mainly during the Middle and Late Jurassic. An important material source for this carbonate cement was the feldspar corrosion process that involved organic matter. The Ca2+, Fe3+ and Mg2+ ions released by the clay mineral transformation process were also important source materials. Because of water-rock interactions during the burial process, the oxygen isotope ratio of the fluid significantly increased during precipitation, by about 3‰. The dolomite cements in calcarenaceous sandstone that was precipitated during the Middle Jurassic have heavier carbon and oxygen isotope ratios, which are similar to those of carbonate debris in the sandstone (δ13C = 1.93‰, δ18O = −6.11‰), demonstrating that the two are from the same source that had a heavier oxygen isotope ratio (δ18O of about 2.2‰). The differences in fluid oxygen isotope ratios during cement precipitation reflect the influences of different water-rock interaction systems or different water-rock interaction strengths. This is the main reason why the sandstone containing many rigid particles (lithic quartz sandstone) has a relatively negative carbon isotope ratio and why the precipitation fluid in calcarenaceous sandstone has a relatively heavier oxygen isotope ratio.

Impact of global change on transmission of human infectious diseases

Abstract: Global change, which refers to large-scale changes in the earth system and human society, has been changing the outbreak and transmission mode of many infectious diseases. Climate change affects infectious diseases directly and indirectly. Meteorological factors including temperature, precipitation, humidity and radiation influence infectious disease by modulating pathogen, host and transmission pathways. Meteorological disasters such as droughts and floods directly impact the outbreak and transmission of infectious diseases. Climate change indirectly impacts infectious diseases by altering the ecological system, including its underlying surface and vegetation distribution. In addition, anthropogenic activities are a driving force for climate change and an indirect forcing of infectious disease transmission. International travel and rural-urban migration are a root cause of infectious disease transmission. Rapid urbanization along with poor infrastructure and high disease risk in the rural-urban fringe has been changing the pattern of disease outbreaks and mortality. Land use changes, such as agricultural expansion and deforestation, have already changed the transmission of infectious disease. Accelerated air, road and rail transportation development may not only increase the transmission speed of outbreaks, but also enlarge the scope of transmission area. In addition, more frequent trade and other economic activities will also increase the potential risks of disease outbreaks and facilitate the spread of infectious diseases.

Relative pollen productivities of typical steppe species in northern China and their potential in past vegetation reconstruction

Abstract: The Relative Pollen Productivities (RPPs) of common steppe species are estimated using Extended R-value (ERV) model based on pollen analysis and vegetation survey of 30 surface soil samples from typical steppe area of northern China. Artemisia, Chenopodiaceae, Poaceae, Cyperaceae, and Asteraceae are the dominant pollen types in pollen assemblages, reflecting the typical steppe communities well. The five dominant pollen types and six common types (Thalictrum, Iridaceae, Potentilla, Ephedra, Brassicaceae, and Ulmus) have strong wind transport abilities; the estimated Relevant Source Area of Pollen (RSAP) is ca. 1000 m when the sediment basin radius is set at 0.5 m. Ulmus, Artemisia, Brassicaceae, Chenopodiaceae, and Thalictrum have relative high RPPs; Poaceae, Cyperaceae, Potentilla, and Ephedra pollen have moderate RPPs; Asteraceae and Iridaceae have low RPPs. The reliability test of RPPs revealed that most of the RPPs are reliable in past vegetation reconstruction. However, the RPPs of Asteraceae and Iridaceae are obviously underestimated, and those of Poaceae, Chenopodiaceae, and Ephedra are either slightly underestimated or slightly overestimated, suggesting that those RPPs should be considered with caution. These RPPs were applied to estimating plant abundances for two fossil pollen spectra (from the Lake Bayanchagan and Lake Haoluku) covering the Holocene in typical steppe area, using the “Regional Estimates of Vegetation Abundance from Large Sites” (REVEALS) model. The RPPs-based vegetation reconstruction revealed that meadow-steppe dominated by Poaceae, Cyperaceae, and Artemisia plants flourished in this area before 6500-5600 cal yr BP, and then was replaced by present typical steppe.

Distribution and changes of active layer thickness (ALT) and soil temperature (TTOP) in the source area of the Yellow River using the GIPL model

Abstract: Active layer thickness (ALT) is critical to the understanding of the surface energy balance, hydrological cycles, plant growth, and cold region engineering projects in permafrost regions. The temperature at the bottom of the active layer, a boundary layer between the equilibrium thermal state (in permafrost below) and transient thermal state (in the atmosphere and surface canopies above), is an important parameter to reflect the existence and thermal stability of permafrost. In this study, the Geophysical Institute Permafrost Model (GIPL) was used to model the spatial distribution of and changes in ALT and soil temperature in the Source Area of the Yellow River (SAYR), where continuous, discontinuous, and sporadic permafrost coexists with seasonally frozen ground. Monthly air temperatures downscaled from the CRU TS3.0 datasets, monthly snow depth derived from the passive microwave remote-sensing data SMMR and SSM/I, and vegetation patterns and soil properties at scale of 1:1000000 were used as input data after modified with GIS techniques. The model validation was carried out carefully with ALT in the SAYR has significantly increased from 1.8 m in 1980 to 2.4 m in 2006 at an average rate of 2.2 cm yr−1. The mean annual temperature at the bottom of the active layer, or temperature at the top of permafrost (TTOP) rose substantially from −1.1°C in 1980 to −0.6°C in 2006 at an average rate of 0.018°C yr−1. The increasing rate of the ALT and TTOP has accelerated since 2000. Regional warming and degradation of permafrost has also occurred, and the changes in the areal extent of regions with a sub-zero TTOP shrank from 2.4×104 to 2.2×104 km2 at an average rate of 74 km2 yr−1. Changes of ALT and temperature have adversely affected the environmental stability in the SAYR.

Environment-ecosystem dynamic processes of Spartina alterniflora salt-marshes along the eastern China coastlines

Abstract: Spartina alterniflora is ecologically important in its original habitat; however, it has caused controversy since it was introduction into China (now it has been spreading rapidly on the Jiangsu, Shanghai, Zhejiang and Fujian coasts). The purpose of the present contribution is, on the basis of an analysis and synthesis of existing data sets, to evaluate the environmental-ecological effects of S. alterniflora, and to identify the relevant scientific problems that require further research in the future. Investigations have shown that, by reducing the near-bed shear stress associated with tidal currents, S. alterniflora can enhance the settling flux of suspended sediment and deposition rate on the tidal flats over the region. Further, field survey and analysis indicate that the S. alterniflora salt-marsh has a high primary production and provides a new type of habitat for the native benthic fauna. Some macro-, meio- and micro-fauna that used to live in the native salt-marshes have adapted to the S. alterniflora salt-marsh, forming a new ecosystem. Under the influences of a number of background factors, such as latitude variations and the coastal type, the environmental-ecological changes induced by Spartine have regional differentiations. To the north of Hangzhou Bay, with a high position of the pre-Holocene stratum base, a large width of the tidal flats, and a gentle bed slope, only a small part of the intertidal zone is occupied by the S. alterniflora salt-marsh. Here, the S. alterniflora salt-marshes mainly play a positive role in coastal protection and ecosystem functioning. In contrary, to the South of Hangzhou Bay, The pre-Holocene deposits are situated in relatively deeo waters, and the width of the tidal flats formed within coastal embayments is relatively narrow. As such, the expansion of S. alterniflora has squeezed the living space of other intertidal organisms, thus has a negative ecological effect. Therefore, the regional differentiation of the Spartina effects should be sufficiently considered in coastal development and management. Furthermore, in order to predict the future evolution of the S. alterniflora wetlands over the region, in addition to in situ monitoring and measurements, an ecosystem dynamic model should be established, taking into account the coupling of the rerrestrial and marine environmental-ecological processes.

Paleo-productivity evolution across the Permian-Triassic boundary and quantitative calculation of primary productivity of black rock series from the Dalong Formation, South China

Abstract: The change of the primary productivity across the Permian-Triassic boundary (PTB) remains controversial. In this study, records from two deep-water sections in South China (Xiakou and Xinmin sections) show the primary productivity decreased gradually from the latest Permian to the earliest Triassic, and five evolutionary stages Increase-Decrease-Recovery-Recession-Stagnation) can be observed from Clarkina changxingensis-C. deflecta to Hindeodus parvus-Isarcicella isarcica zones. Primary productivity decreased abruptly from the base of C. meishanensis zone. Besides, for adjusting to the deterioration of the oceanic environment, the primary producers in the oceanic surface had changed to acritarch and cyanobacteria, which were more tolerant of stressful environment. Then the producers were under huge stagnation in the H. parvus-I. isarcica zone. The values of quantitative calculation of the primary productivity from the black rock series in the Dalong Formation were very high, corresponding to that of an upwelling area in modern ocean, which shows that the strata of the Dalong Formation in the study region are potential hydrocarbon source-rocks. This result may come from the fact that South China craton was located at the equatorial upwelling area during the Permian-Triassic transitions. But organic matter contents were different in various sections because they could be affected by redox conditions and diagenesis process after burial.

Zircon SHRIMP U-Pb dating of granites from Dulan and the chronological framework of the North Qaidam UHP belt, NW China

Abstract: Zircon SHRIMP dating of granites from Dulan, east segment of North Qaidam UHP belt shows that they are 406.6±3.5 Ma for Yematan-E, 407.3±4.3 and 397±6 Ma for Balijiehatan-W, 404.5±4.0 and 397.0±3.7 Ma for Shuiwenzhan-N, 380.5±5.0 Ma for Shuiwenzhan-S, 382.5±3.6 and 372.5±2.8 Ma for Chachagongma. These granites from Dulan represent the products of the third and fourth periods of Paleozoic magmatism in North Qaidam. Geochemically, the granitoids with metalumious to weak peratuminous are quartz diorite, granodiorite, and granite in composition and mainly belong to calc-alkaline series, a few samples to calc or alkali-calc series. The third period of granites is a rock association of granodiorite + granite, with initial 87Sr/86Sr ratios from 0.7082 to 0.7110 and T 2DM model ages from 1.41–1.90 Ga; and the fourth period of granites is a rock association of quartz diorite+granodiorite+granite, with initial 87Sr/86Sr ratios from 0.7072 to 0.7091 and T 2DM model ages from 1.07–1.38 Ga. Therefore, the third period of granites has higher initial 87Sr/86Sr ratios and T2DM model ages. On the contrary, the fourth period of granites has ɛ Nd(t) values from 0.6 to −3.0, higher than that of the third granite with ɛ Nd(t) values −3.2 to −9.3. Thus, the data comparison indicates that the third granites may derive from Paleo-proterzoic continental crust with mantle material whereas the fourth granites may derive from the Meso-proterzoic basalt crust with continental material. Combined with regional geology, we thought that the third granites were formed relative to plate exhumation and the fourth granites to delamination of the lithospheric mantle.

The P-wave velocity structure of the lithosphere of the North China Craton—Results from the Wendeng-Alxa Left Banner deep seismic sounding profile

Abstract: For the first time on the Chinese mainland, long-range wide-angle seismic reflection/refraction profiling technology has been applied to seismic wave phases from different depths and with different attributes within the various blocks of the North China Craton to characterize the structure of the crust and upper mantle lithosphere. By comparative analysis of the seismic wave phase characteristics in each block across a 1500-km-long east-west profile, we have identified conventional Pg, Pci, PmP and Pn phases in the crust, made a clear contrast between PL1 and PL2 waves belonging to two groups of lithospheric-scale phases, and produced a model of crust-mantle velocity structures and tectonic characteristics after one- and two-dimensional calculations and processing. The results show that the thickness of the crust and lithosphere gradually deepens from east to west along the profile. However, at the reflection/refraction interface, seismic waves in each group show obvious localized changes in each block. Also, the depth to the crystalline basement changes greatly, from as much as 7.8 km in the North China fault basin to only about 2 km beneath the Jiaodong Peninsula and Taihang-Luliang area. The Moho morphology as a whole ranges from shallow in the east to deep in the west, with the deepest point in the Ordos Block at 47 km; in contrast, the North China Plain Block is uplifting. The L1 interface of the lithosphere is observed only to the west of Taihang Mountains, at a relatively slowly changing depth of about 80 km. The L2 interface varies from 75 to 160 km and shows a sharp deepening to the west of Taihang Mountains, forming a mutation belt.

Texture and tectonic attribute of Cenozoic basin basement in the northern South China Sea

Abstract: Based on the drilling data, the geological characteristics of the coast in South China, and the interpretation of the long seismic profiles covering the Pearl River Mouth Basin and southeastern Hainan Basin, the basin basement in the northern South China Sea is divided into four structural layers, namely, Pre-Sinian crystalline basement, Sinian-lower Paleozoic, upper Paleozoic, and Mesozoic structural layers. This paper discusses the distribution range and law and reveals the tectonic attribute of each structural layer. The Pre-Sinian crystalline basement is distributed in the northern South China Sea, which is linked to the Pre-Sinian crystalline basement of the Cathaysian Block and together they constitute a larger-scale continental block—the Cathaysian-northern South China Sea continental block. The Sinian-lower Paleozoic structural layer is distributed in the northern South China Sea, which is the natural extension of the Caledonian fold belt in South China to the sea area. The sediments are derived from southern East China Sea-Taiwan, Zhongsha-Xisha islands and Yunkai ancient uplifts, and some small basement uplifts. The Caledonian fold belt in the northern South China Sea is linked with that in South China and they constitute the wider fold belt. The upper Paleozoic structural layer is unevenly distributed in the northern South China. In the basement of Beibu Gulf Basin and southwestern Taiwan Basin, the structural layer is composed of the stable epicontinental sea deposit. The distribution areas in the Pearl River Mouth Basin and the southeastern Hainan Basin belong to ancient uplifts in the late Paleozoic, lacking the upper Paleozoic structural layers. The stratigraphic distribution and sedimentary environment in Middle-Late Jurassic to Cretaceous are characteristic of differentiation in the east and the west. The marine, paralic deposit is well developed in the basin basement of southwestern Taiwan but the volcanic activity is not obvious. The marine and paralic facies deposit is distributed in the eastern Pearl River Mouth Basin basement and the volcanic activity is stronger. The continental facies volcano-sediment in the Early Cretaceous is distributed in the basement of the western Pearl River Mouth Basin and Southeastern Hainan Basin. The Upper Cretaceous red continental facies clastic rocks are distributed in the Beibu Gulf Basin and Yinggehai Basin. The NE direction granitic volcanic-intrusive complex, volcano-sedimentary basin, fold and fault in Mesozoic basement have the similar temporal and spatial distribution, geological feature, and tectonic attribute with the coastal land in South China, and they belong to the same magma-deposition-tectonic system, which demonstrates that the late Mesozoic structural layer was formed in the background of active continental margin. Based on the analysis of basement structure and the study on tectonic attribute, the paleogeographic map of the basin basement in different periods in the northern South China Sea is compiled.