Aeolian landforms are divided into two categories： wind deposition landforms and wind erosion landforms. The former refers to various types of sand dunes with their shapes being determined by the spatio-temporal variation of wind erosion and deposition. Wind erosion may play a significant role in reshaping the cumulated dunes which results in the formation of eroded dunes. This discovery is contrary to traditional understanding， therefore， eroded dunes have been ignored for a long time. However， many Martian dunes with subtle differences from dunes on the earth due to limited sediment supply have been found. We reviewed the description of eroded dunes by French M. Mainguet， and conceptual framework of controlling factors on dune morphology， and then pointed out clearly the necessity of studying eroded dunes. After systematic study on Martian dunes， we found ten types of eroded dunes， and then analyzed the morphology， development environment and possible formation mechanism. The vast saline-alkali land in the arid area of the earth which is similar to the limited sand supply environment on Mars is most likely to develop eroded dunes. Based on this， it can be inferred that eroded dunes are common on the earth， and the study on them is of great significance to the development of aeolian geomorphology theories and the Mars exploration in China.
In order to effectively guide geological researchers and scientific research institutions for the following year project submission， we analyzed the application， review and grant of various projects managed by Division of Geology， National Natural Science Foundation of China. The results showed： ①Compared with the number of 2020， the number of applications for 2021 projects increased except for the decrease of applications for Excellent Young Scientists Fund projects； ②The reviewed project number of General Program， Young Scientists Fund and Fund for Less Developed Regions in 2021 increased slightly compared with that in 2020. In addition， the project reports submitted in January 2021 were reviewed， and the reports concluded by the end of 2020 and their progress in various areas were summarized.
In 2020， the upstream and mid-downstream of the Yangtze River experienced massive floods， with the major mainstream floods occurring in the upper Yangtze River. In this study， we first reviewed the floods and their related losses， and then analyzed the characteristics of flooding disasters in the upper Yangtze River based on several catastrophic floods in history. Finally， we proposed the integrated strategies for flood defense and the control tactics for flash floods in the Yangtze River Basin in the new era. Our results show that the floods in the Jinsha River underlay the floods in the upper Yangtze River， whereas the flood peaks were primarily attributed to the inflow from the Minjiang River， the Jialing River and the mainstream interval. The co-occurrence of floods in the aforementioned three tributaries led to the mega-floods in the upper Yangtze River， which formed the foundation and an important component of the basin-wide floods. At present， flash floods and accompanied geological disasters caused the largest number of deaths， and the biggest property losses occurred in the middle-lower reaches and the lake areas. In the future， the embankments will remain the basis of flood control. The main means to improve flood control standards of urbans long the river will rely on the joint optimal operation of reservoirs. In addition， the most effective way to reduce flood losses will be non-engineering measures such as natural solutions that give space to floods.
MVT Pb-Zn deposit （Mississippi Valley Type） is one of the most important types of lead-zinc mine. Many large oil and gas fields developed together with MVT type Pb-Zn ore in the foreland basin in the world. Hydrocarbon fluid associated with oil/gas has played a very important role in the mobilization， transportation and precipitation of metal elements of Pb-Zn. Several metallogenic models of MVT Pb-Zn deposit have been established based on the background of foreland basin structure of which hydrocarbon fluid participated in Pb-Zn mineralization， or acted as the role of reductant to precipitate in Pb-Zn minerals. The close connections between the MVT type Pb-Zn deposit and hydrocarbon fluid of oil/gas field in foreland basin is widely recognized by deposit scientists in the world. Currently geologists' attentions have been focused on the role of hydrocarbon fluid in the metallogenic characteristics of MVT Pb-Zn deposit formation， ability of mobilization and transportation of Pb-Zn elements and metallogenic mechanism of hydrocarbon fluid during tectonic evolution history. On the basis of geological and geochemical study of MVT Pb-Zn deposit， ideas and methods of petroleum geology and organic geochemistry should be used to study the coupling relationship of evolution process of hydrocarbon fluid and mineralization process of MVT Pb-Zn deposit.
Using the observed sea surface temperature data of the Hadley Center， as well as the model data under historical experiments in the Coupled Model Intercomparison Project Phase 5 （CMIP5） and the Coupled Model Intercomparison Project Phase 6 （CMIP6）， the simulation ability of the two most important interdecadal scale modes， the Atlantic Multi-decadal Oscillation （AMO） and the Pacific Decadal Oscillation （PDO）， in CMIP5 and CMIP6 was analyzed and evaluated. By comparing the multi-model ensemble， it is found that in terms of spatial patterns， both CMIP6 and CMIP5 can simulate the signals of AMO in the North Atlantic region， but the simulation of CMIP6 is better. For PDO modes， both can simulate the signal in the North Pacific region， while for the PDO signal in the tropical Pacific region， the amplitude of the CMIP6 simulation is significantly closer to the observation. In terms of periodic simulation， the results of CMIP5 and CMIP6 are similar， and both can simulate the 60~70-year period of the AMO and the double periods， namely 20 and 60~70 years， of the PDO. On the whole， CMIP6 has a certain improvement in the simulation of spatial characteristics compared with CMIP5. But there is no significant improvement in the ability of periodic simulation.
Phenology is considered as an important indicator for understanding the vegetation dynamics and the impact of climate change on ecosystem. It has significant influences on surface albedo， roughness， evapotranspiration， CO2 flux， and human activities. This study presents the progress on the phenology extraction methods based on satellite， and the driving factors of vegetation phenology dynamics. The key weaknesses in our current understanding of vegetation phenology in the context of climate change are also raised， including the difficulty in estimating the phenology of evergreen vegetation based on remote sensing directly from the perspective of leaf and canopy structure， the low comparability between satellite products and ground-based measurements due to the scale effect， the unclear synergistic mechanisms between climate factors （rainfall and day/night temperature） and urbanization， the lack of phenological products and models for specific vegetation types， as well as the inconsideration of lag effect of phenology. So， it is important to focus on the following four aspects in future research： ① the development of satellite phenology extraction methods for evergreen vegetation； ② the research on the mechanisms and forecast of climate change and extreme weather on phenology； ③ the study of the impact of urbanization and vegetation types on phenology， together with their synergistic effects； ④ the establishment of phenological model at community scale which considers precipitation， lag effect and scale effect.
Land space planning is an important starting point of spatial governance modernization. This paper analyzes the realistic dilemma and breakthrough path of land space planning from the perspective of geography. Land space planning is a combination of development and management and control. We should adhere to the method of combining goal orientation and problem orientation，pay attention to the people-oriented on the basis of keeping the bottom line，realize "five wins" through the process of top-down orientation，combination of top-down and "five associations"， and realize the goal of people-centered spatial governance. We should first prepare the strategic planning of large geographical units to ensure that the macro-control is scientific and reasonable，and then prepare the detailed planning of the administrative region to achieve specific control tasks.
Andesite is an important rock type in subduction zone magmatic arcs. Its genesis is still one of focuses on the international geological research. According to the tectonic setting of the andesite， magmatic arc andesite can be classified as continental arc andesite and oceanic arc andesite， which show different features in chemical composition and spatial distribution. Since the late 1920s， numerous researches have enriched our understanding of the genesis of magmatic arc andesite， which gradually can be summarized as Basalt-input model and Andesite-input model. The Basalt-input model considers the primary magma of magmatic arc andesite is basaltic， emphasizing the intra-crustal processes such as fractional crystallization， assimilation and contamination， and magma mixing. The Andesite-input model suggests andesitic melts can be formed directly in the mantle source， emphasizing the sub-crustal processes such as the metasomatic reaction between slab-derived fluid/melt and mantle peridotite， and rising of sediment diapirs. Although some progress has been made in the study of the genesis of magmatic arc andesite， each model still needs to be improved. There are many research fields to be studied in the future， including experimental petrology research of mantle metasomatite， relationship between andesite and the formation and evolution of continental crust， application of theoretical calculation and modelling and so on.
Eutrophication can cause critical transitions in shallow lakes and severely impair ecosystem services. Phosphorus is one of important environmental factors that cause critical transitions in lake ecosystems. Exploring the mechanisms of phosphorus dynamics in lakes is a key to lake management. This paper simulated the phosphorus concentration variations in lakes using a phosphorus kinetic model， and discussed the specific impacts of main model parameters on simulation output. Based on literature reviews， we discussed in detail the effects of different types of climate change and human activities on the critical transition time， hysteresis length， and restoration rate of lakes. The paper indicated that changes in factors such as climate change induced temperature warming， weakened light intensity， increased wind/waves and human activities caused biological disturbances and water level fluctuations would not change the threshold of transition or the time of transition， but would significantly delay the recovery time， decrease the recovery threshold and extend the lag period and the steady state. For the management of lake ecosystems， we suggested that it be important to consider the different impacts from different external perturbations on the process of critical transitions to avoid harmful tipping point.
Conodont is the predominant fossil which is used to study the Ordovician stratigraphy. Although the conodont biozones which can be correlated in the globe have been built up， the correlation of each continent has not been paid more attention to， especially there is not conodont biostratigraphy constraint by high precision and accurate chronological data. We compiled the published Ordovician conodont biostratigraphy data of Asia and preliminarily set up an Ordovician conodont stratigraphy framework. Furthermore， in combination with the progress of International Geologic Time Scale， we proposed the solution for the Ordovician conodont biostratigraphy studies which should be addressed； that is， based on the running program IGCP 652 and the task of the China workgroup， we should carry out multiple stratigraphy studies for the Ordovician strata in southwest Ordos， and set up the improved conodont biostratigraphy.
Blowouts are the primary geomorphologic manifestation and driving force of sandy grassland desertification in the Gonghe Basin. However， their feedback mechanism between the flow dynamics and geomorphology is unclear. Two-dimensional ultrasonic anemometers and gradient sand traps were used in this study to measure the characteristics of wind flows and sediment transport at different blowouts of different developing stages in the Gonghe Basin. The feedback between the morphology-dynamic processes of the blowouts was discussed. Results show as follows. ① After entering the sand patch and small bowl blowout along the prevailing wind direction， air flow expanded and decelerated， and then accelerated until going outside the blowout； when entering a trough blowout of a small or medium size， it expanded and decelerated at the headwall， accelerated at the bottom of blowout， decelerated at the windward slope of the depositional lobe， and then recovered somewhat at the leeside slope of the depositional lobe. Besides， the wind speed was negatively correlated with steadiness of flow and directional steadiness in the early stage of blowout， but was positively correlated with the steadiness of flow and negatively correlated with the directional steadiness in the middle stage of blowout. ② Due to the rotating vortices in the blowout， the wind speed profiles in the trough blowout displayed a nonlogarithmic behavior. ③ The measured sand flux density at different stations decreased exponentially with height. However， due to the feedback effect between flow dynamics and morphology， the sediment transport fluxes at different positions were obviously different， with the lowest at the bottom of the blowout and the largest in front of the windward slope of the deposition lobe. In conclusion， there is a form-flow feedback in the blowout， and the bigger the blowout is， the more obvious the feedback effect is.
Soil hydraulic properties regulate hydrological processes， energy exchange， carbon and nitrogen cycling processes and the interactions among them over multiple scales. This study first briefly reviews the advancement in soil hydrological research over the past 30 years， including in situ observation and monitoring of hydraulic properties， the effects of soil hydraulic properties on hydrological processes， and the mechanism and scaling effects of soil hydraulic properties on hydrological processes at multiple spatial scales （soil profile， hillslope， watershed， and region）. Subsequently， it discusses the challenges and opportunities in soil hydraulic property research. Finally， it describes a case study of analysis of impacts of soil hydraulic properties on hydrological processes in the Qilian Mountain Ranges in Northwest China. This study serves as food for thought to improve current understanding of the effects of soil hydraulic properties on hydrological processes， enhance soil hydrology and mountainous hydrology， and in turn， support water resources management and regional sustainable development.
Under the global warming， the extreme warming process， heavy snowfall and Rain-On-Snow event occur more frequently， resulting in more frequent snowmelt floods， and the rain， snow and ice mixed floods. Therefore， the projection， prediction， forecasting and early warning of the flood disasters are urgently needed in the arid regions of northwest China. According to the present research progress on key technologies of snowmelt flood disaster forecasting， it is necessary to reveal the mechanism of flood disasters， develop the monitoring and early warning device of snowmelt flood disasters， and then construct the three-dimensional monitoring system in arid areas. Based on the in situ， remote observation and involved research results， a hydrological model should be developed to accurately simulate the rain， snow and ice mixed floods. Therefore， an Intelligent Decision Support System （IDSS） should be constructed to demonstrate the flood submerged areas， evaluate the risk of the flood disasters and give the best solutions in the arid regions of northwest China.
Glacier motion is composed of plastic deformation of the ice， sliding of ice over its bed and deformation of the bed itself. Among these three components， basal sliding is a significant factor. And its law， which represents the relationship between the sliding speed， the shear stress at the base of the glacier and the characteristics of the ice bed， is the basal boundary condition of the glacier dynamic process. The estimation of basal sliding plays an important role in the study of glacier motion， internal stress distribution and mechanism of glacier anomaly. This study systematically reviews the development of glacier sliding and its existing estimation methods， which gradually expand from only considering the relationship between shear stress and ice bed roughness to taking into account the comprehensive influences of effective pressure and hydrologic process under the ice. We dissect the structures and functions of existing models， and then analyze the main problems and challenges of these methods， in order to provide references for further improvements of this model. Future studies on glacier basal sliding should be based on big remote sensing data and new technique， and focused on coupling the influence of subglacial hydrological processes， so as to promote the integrated study of climate change-glacier material balance-glacier dynamic response process.
The traditional heavy mineral analysis is a fundamental and cheap provenance tracing method for clastic sediments. It provides comprehensive provenance information and irreplaceable background data for the single-mineral methods of provenance tracing. There are new progresses in basic theory and technology in recent years， but a systematic summary is still lacking. This paper summarizes the progress and development trend of heavy mineral analysis， which is shown in the following aspects： ① The impact of factors such as weathering， hydraulic sorting， diagenetic modification on heavy minerals during transport， deposition， diagenesis， and exposure； ② Data acquisition processes of heavy mineral analysis （sampling， pre-processing， selection of grain size fraction， counting） and issues that should be paid attention to； ③ How to analyze， process and apply heavy mineral data， including calculating commonly used heavy mineral indexes and sediment budgets， and carrying out bias correction； ④ The new progress and development trend of theory and technology in the heavy mineral analysis. It is believed that automatic mineral identification by machine and the combination of heavy mineral analysis method and single-mineral method are the development direction of provenance tracing based on heavy mineral analysis.
In the recent decades， there has been plenty of progress， both in analytical methods for Re-Os and PGE in geological samples and the applications of the Re-Os and PGE systems in geosciences. We first briefly review the recent advances for analytical methods of Re-Os and PGE in geological materials including sample dissolution， chemical separation and mass spectrometric determinations. Thereafter， we simply outline the recent progresses in major application fields of the Re-Os isotopic and PGE elemental systems in geosciences， including tracing the evolution of planetary formation and evolution， tracing the evolution of earth's mantle， dating of metal sulfide ore deposits， dating sedimentations and investigating the variations of earth's paleo-environment， as well as dating and tracing of the petroleum systems.This review stands as a comprehensive reference for researchers to facilitate the choice of the analytical method best adapted to each specific scientific problem and sample type， or to consider in the development of analytical methods for Re-Os-PGE in geological materials， as well as to promote the development of the applications of Re-Os and PGE in geosciences.
Inland water bodies （lakes， reservoirs， swamps， rivers） and estuarine oceans are widely and continuously distributed with sediments， which are affected by natural and human activities in the process of their formation， and have environmental significance and characteristics related to pollutants. There are great regional differences in China， and the environmental problems are more prominent. After decades of research on sediment environment and pollution control， the relevant achievements in China continue to emerge. This paper first introduces some international landmark studies on sediment environment and reviews the development of sediment research in China in the past 70 years.Then， the main research progress of China in the research fields of sediment environment and pollution control in recent 20 years are systematically summarized， which are the role and effect of sediment in water environment， environmental behavior and influencing factors of pollutants at sediment-water interface， ecological risk and quality criteria of sediments， in-situ remediation of contaminated sediments， environmental dredging and ex-situ disposal as well utilization of contaminated sediments. And the relationship and difference of some research results are reviewed. At the end of the paper， the existing problems of sediment environmental research in China are analyzed， and several scientific and technical problems that need to be studied urgently and deeply， such as interdisciplinary， composite pollution， emerging/non-traditional pollutants， quality criteria， and governance technology innovation， are put forward. The solutions and approaches are proposed， and the prospects are also given.
The magnesium （Mg） isotope system has been proved to be quite advantageous in tracking silicate weathering. By summarizing the researches about Mg isotope geochemistry in the process of continental silicate weathering， the following cognitions are summarized： ① In terms of chemical weathering， dissolution of primary minerals makes the Mg isotopic composition of the liquid phase lighter and the residual solid phase heavier. The secondary minerals contain two forms of Mg （exchangeable Mg and structural Mg） with different δ26Mg. During the formation of secondary minerals， the Mg isotope fractionation direction is related to their types，structures and formation mechanisms. When Mg2+ isadsorbed and desorbed by clay minerals， the Mg isotope fractionation direction is still uncertain. However， compared to 24Mg， 26Mg preferentially tends to be adsorbed and desorbed by the soil exchange complex. ② In terms of physical weathering， mineral separation caused by water and wind will change the Mg isotope composition of weathering products. ③ In plant-soil system， the degree of Mg isotope fractionation is very small. At present， in some important processes of continental silicate weathering， the Mg isotope geochemical behavior is still controversial. Therefore， laboratory tests， simulation calculations， and the combination with other isotopes are needed urgently to consummate the theoretical basis， so as to promote the widespread application of Mg isotopes in the tracking of continental weathering.
The change of landscape pattern has an important influence on the ecosystem water purification service. In order to explore the influence mechanism of the landscape pattern on the water purification service， in this article we systematically sorted out and analyzed the domestic and foreign relevant literature. It is concluded that there are differences in the influence of landscape pattern on water purification service at different spatial and temporal scales； that is， the response of water purification service to landscape pattern has scale dependence. At the same scale， different terrain conditions and landscape matrix also make the impact of landscape pattern on water purification service show spatial heterogeneity. At the same time， there is a threshold effect between landscape pattern and water purification service， which makes decision makers need to consider various factors more comprehensively in optimizing landscape pattern and water quality protection. In the current research， the characteristic spatial scale of water purification service response to landscape pattern is unclear； the study of landscape configuration and spatial differentiation characteristics needs to be strengthened； threshold effect is not clear. In the future， it is necessary to carry out multi-level and multi-scale comparative research to explain the characteristic scale of landscape pattern and water purification service from different aspects. Developing the landscape pattern index which can represent the ecological process and strengthening the research on the influence of landscape configuration on water purification service will deepen the exploration of spatial differentiation characteristics under different influencing factors. Strengthen the exploration of threshold recognition method of water quality purification service to landscape pattern response， effectively determines the threshold， and provides decisions support for regional landscape pattern optimization and water environment management.
Quantum gravimeter is a new type of absolute gravimeter that has been rapidly developed in the past 30 years. At present， the research on this new type of gravimeter has entered the stage of miniaturization and practical applications. The applications in the fields of earth science research based on quantum gravimeters at home and abroad have been developed rapidly， including volcanic activity monitoring， marine absolute gravity measurement， and airborne absolute gravity measurement， etc. The ZAG-E type of quantum gravimeter developed by our laboratory has the advantages of small size， easy handling， and high stability. Its absolute gravity measurement accuracy can reach 10 μGal. Based on this quantum gravimeter， our team has carried out related research on continuous absolute gravity measurement at seismic stations， focusing on the continuous absolute gravity measurement performed at the Yanzigou Seismic Station in Ganzi Tibetan Autonomous Prefecture， Sichuan Province. These studies are helpful for the construction of the gravity data of the area and the analysis of the geological topography and the geological activities. The precision gravity measurement based on quantum gravimeters can provide a new method for the research of earth science， and it can also provide reliable absolute gravity data. In the future， quantum gravimeters are expected to be more and more widely used in geosciences such as geophysics and absolute gravity surveying and mapping on the surface.
Leaf wax n-alkanes are widely distributed in sediments； they have a clear formation process， and they are resistance to environment change. δD composition of leaf wax n-alkanes is a newly developed biogeochemistry proxy with great potential in paleoenvironment reconstruction. In this paper， we reviewed the formation process of leaf wax n-alkanes and their hydrogen isotopic fraction， evaluated the relationship between leaf wax n-alkanes δD and regional humidity， and summarized recent applications of them to paleoclimate reconstruction. Based on the studies of n-alkanes δD of surface sediments， we find n-alkanes δD is a good proxy indicator of humidity in semiarid and arid climate region in monsoonal East Asia. Compared with other proxies from loess-paleosol sequences， the n-alkanes δD is a direct indicator of humidity variations； it shows direct response to environment change， and it reveals precession signal of solar insolation variations in orbital timescales paleoclimate record. In this case， the n-alkanes δD is a good proxy for humidity variations in sedimentary records in East Asia monsoon region， and， further research on the influence of the variations of precipitation isotope and local isotope fraction process to the n-alkanes δD is compulsively needed.
The Third Pole （TP） has diverse climate and frequent disasters and is a key area that affects global and Asian climate anomalies. The study of seasonal-interannual climate prediction in the TP area is of great scientific and guiding significance for improving regional forecasting skills and reducing the natural disaster impacts. Based on the hindcast data of BCC_CSM1.1m， we evaluated the prediction performance of 2m-air temperature （T2m） and snow depth over the TP by employing deterministic forecast verification methods and then analyzed the modulation of the Sea Surface Temperature Anomalies （SSTA）. The results indicate that BCC_CSM1.1m has useful prediction skills in the TP area for the seasonal-interannual 2m-air temperature and snow depth predictions. The prediction skill of summer T2m is generally higher than winter T2m and snow depth. The predictivity of BCC_CSM1.1m is generally weaker for a longer lead time， but there is a skill-recovery. Meanwhile， SSTA could modulate the seasonal-interannual climate prediction over the TP and ocean signals such as El Ni?o show their direct and indirect influences on the predictability.
As the third pole of the world， the Tibet Plateau （TP） is one of the natural landforms， which has the most significant impact on global weather and climate. The thermal effect of the huge land surface deep into the middle of the troposphere directly affects the atmosphere， which not only forms the climate pattern in Asia， but also leads to climate change in the northern hemisphere and even the world. In the northern part of the TP， there is the largest desert group in the mid-latitudes of the northern hemisphere. Compared with other underlying surfaces including the TP， the desert has the characteristics of large surface albedo， low soil heat capacity， and low water content， which is an important source of sensible heat in the earth system and even plays significant roles in global and regional energy balance and climate changes. TP and its northern vast desert area—The two important terrestrial systems constitute a unique symbiotic geographical unit in the world， where land-atmosphere coupling must be related to each other through a certain process. Drought is a common and extremely serious natural disaster in the world. China is one of the countries where droughts occur most frequently. Under the background of climate change， droughts also tend to occur more frequently and worsen， especially in the north China. The causes of drought are complex， and they have always been a difficult and hot spot for research in related fields both at home and abroad. Starting from the land-atmosphere coupling process of the plateau-desert symbiosis geographic unit， what mechanism is used for the formation and evolution of drought in northern China is a frontier topic worth exploring. This article summarizes the latest advances in atmospheric scientific research on TP and the research on arid and semi-arid land surface processes including desert areas in recent years，from which we condense the key scientific issues in the research on the impact of the land-atmosphere coupling process between TP and the northern desert on drought in China for the purpose of reference and helping scientific and technological workers to carry out related exploration.
Most of the permafrost regions are located in mid-latitude plateau regions in China， which are different from the permafrost regions around the Arctic Ocean， and the genesis mechanism， occurrence environment and basic characteristics of Natural Gas Hydrate （NGH） are more sophisticated. Qilian Mountain is verified as the only permafrost area in which the samples of NGH can be obtained through scientific drillings. In the past 10 years， with the support of Special Research Project of the Ministry of Natural Resources and the National Special Project of Gas Hydrate of China Geological Survey， the key technologies of NGH geochemical exploration have been successively carried out in the Qinghai-Tibet Plateau and the Mohe basin. The effective index and identification marks of NGH geochemical exploration are optimized， and the accumulation mechanism of NGH in permafrost area is discussed. The geochemical exploration model of NGH was developed， and the geochemical exploration technology system for NGH was preliminarily established， which shows the validity of exploration practice. The effectiveness of geochemical exploration technology system for NGH has been preliminarily tested and applied， which has a broad application prospect.
Based on one planned arctic gas pipeline project which will cross continuous， discontinuous and sporadic permafrost zones and zones of seasonal frost from north to south， with 5 ℃， -1 ℃ and -5 ℃ settings of gas-flow in buried pipeline， a geothermal model for the interactions between pipeline and permafrost was established to investigate the thermal effect of pipelines on the freezing and thawing of soil around pipeline and thermal stability of permafrost by using a commercially available finite-element program for numerical analysis. The results show that different pipeline gas flow temperatures influence the permafrost table greatly. Especially in discontinuous permafrost zones the permafrost table is influenced in both positive temperature and negative temperature. The warm （+5 ℃） gas pipeline could lower permafrost table by about 1 to 3 times of pipe diameter and aggravate the degradation of permafrost around pipeline； The cold （-1 ℃） and chilled （-5 ℃） gas pipeline can effectively raise the permafrost table and maintain the thermal stability of frozen soil， but the temperature of soils under the chilled （-5 ℃） pipeline decreases obviously， which may lead to frost heave hazards. In terms of thermal stability around pipeline， it is advised that a transporting temperature of gas flow as -1 ℃ should be adopted in continuous permafrost zone all year round which causes only little disturbance to the permafrost environment； in discontinuous permafrost zone pipeline could operate above freezing in the summer months with the station discharge temperature trending the ambient air temperature， but the discharge temperature must be maintained as -1 ℃ throughout the winter months； in zone of seasonal frost the cold （-1 ℃） and chilled （-5 ℃） pipeline may cause frost heave， therefore pipeline should run in positive temperature without extra temperature cooling control. Finally， the initial framework solutions are proposed in hope of supplementing existing gas transporting process theory and identifying new approaches for gas pipeline in northern and upland permafrost regions.
In the vertical， the isothermal layer and mixed layer are two parameters governing the upper ocean structure. High salinity stratification in the surface layer often limits the mixed layer depth and thus results in the interlayer called the barrier layer between the base of mixed layer and the top of the thermocline. The barrier layer acts as a "barrier" for the transfer of heat， monmentum， mass， and nutrient fluxes between the mixed layer and the thermocline， affecting the heat budget of the surface mixed layer and resultant air-sea interaction. Owing to the implementation of global ocean observation programs， scientists have gradually realized the importance of oceanic salinity in ocean circulation and climate change in the past two decades. Thus， the role of barrier layer caused by salinity in heat balance of upper ocean is the present hotspot in physical oceanography field. Focusing on the key scientific issues centered at the barrier layer variations and its climatic impacts， three aspects of it are introduced under the review：Spatial structures and multi-scale variations of barrier layer in the world ocean； roles of oceanic and atmospheric processes in barrier layer variations； key processes and mechanisms of interactions between barrier layer and weather， climate and biology. We mainly emphasize the ocean-atmosphere interactions associated with the barrier layer variations and their cliamtic impacts. Finally， we propose several issues that remian to be solved were proposed.
Earth's gravity field and its application in geosciences is one of the important contents in the fields of Earth sciences. It plays an irreplaceable role in national basic surveying and mapping， disaster monitoring， resource exploration， surface layer coupling， aerospace and other aspects. In recent years， with the continuous innovation of gravity field observation technology， gravity measurement and the corresponding theory， methods and applications have developed rapidly， and fruitful research results have been achieved. The gravity topics of the annual meeting of Chinese Geoscience Union in 2020 are the concentrated display of these achievements （including 42 oral reports and 10 posters）. Based on the reports on this annual meeting， this paper summarizes the latest research progress in the Earth's gravity field and its geoscience application in China in recent years.
Antarctic ice core is an ideal paleoclimatic and paleoenvironmental carrier， which records the past variations of various parameters such as air temperature， precipitation and their major factors， e.g. solar activity， volcanism. High-resolution geochemical analyses of LGB69 ice core， East Antarctica show that ① Based on the combination of seasonal variations of δ18O and Na+ with volcanic eruption markers， LGB69 ice core is dated to 290 a （A.D.1712-A.D.2001）±2 a through annual layer counting， with a high average annual accumulation rate of 259 mm w.e./a； ② Five-year moving average （A.D.1968-A.D.2001） of δ18O of LGB69 ice core has good positive correlation with that of temperature departure at adjacent Davis Station， indicating that δ18O is an effective proxy for air temperature. Air temperature from A.D.1712 to A.D.2001 in LGB69 region is a process of fluctuating warming， which can be divided into four stages. The average annual value of 5-year moving average temperature departure is 0.43 ℃ higher than that of last cold stage in the Little Ice Age which ended in A.D.1914； ③ By Morlet wavelet analysis， both δ18O （air temperature） and accumulation rate （precipitation） of LGB69 ice core from A.D.1712 to A.D.2001 present ca. 11-year， ca. 22-year and ca. 60-year cycles. Multinest of cycles for δ18O， accumulation rate of LGB69 ice core implies its sensitivity to climate change. The above-mentioned results build up a good basis for further research on the reconstruction of temporal variations in air temperature and precipitation and the effects of factors such as solar activity， volcanism on climate change in Antarctica.
It is important to assess and monitor the level of regional sustainable development. With the development of observation and computer technology， scholars and stakeholders have realized that constructing an index is a critical step in evaluating the level of regional sustainable development. This paper introduced the "Sustainable Society Index" （SSI） from three perspectives， namely， theory， indicators framework， and methodology. This paper reviewed the literatures about the SSI based on two views， that is， limitation and improvement. There are three conclusions. First， the scholars and stakeholders widely thought SSI was a comprehensive method for assessing and monitoring the level of national sustainable development. Second， the limitations of SSI were mainly about the selection and aggregation of indicators. Third， the improvements of SSI were mainly about the aggregation methods. Finally， this paper also suggested possible research directions in the future.
As an important part of the Tibetan Plateau， the SE Tibetan Plateau experienced significant tectonic uplift， fault activity， climate change， and river system reorganization during the Cenozoic and these processes were accompanied with rapid rock exhumation. Therefore， the SE Tibetan Plateau has become one of the hottest areas of research focus. However， great debate exists regarding the exhumation process and forcing mechanism of the SE Tibetan Plateau during the Cenozoic. Therefore， we select the Lincang granite of the SE Tibetan Plateau as the research area. Firstly， we reconstruct the Cenozoic exhumation history of the Lincang granite area， based on multi-system low temperature thermochronology ［including apatite （U-Th）/He， zircon （U-Th）/He and apatite fission track］ and thermal history modeling. Secondly， we explore possible forcing mechanisms for the recorded several phases of rapid rock cooling in this area by integrating regional climatic and tectonic data. The preliminary conclusions are as follows： ① The Lincang granite area experienced three phases of rapid exhumation during the Cenozoic （late Eocene， Oligocene and middle Miocene）. ② Combined with regional climate and geological data， we suggest that the late Eocene rapid cooling event of Lincang granite area was mainly caused by crustal shortening， and the Oligocene rapid cooling event was associated with crustal shortening and lateral extrusion. The occurrence of these two events may be inevitably connected with the oblique subduction of the Indian plate. In contrast， the middle Miocene rapid cooling event was closely related to the Asian summer monsoon intensification. The intensified monsoon precipitation would have likely increased the power of river incision， which accelerated the geomorphic evolution of this region.
The Indian Ocean Dipole （IOD） is one of the dominant interannual variabilities in the tropical Indian Ocean， which has important impacts on countries around the Indian Ocean and even the global climate. The research on the formation mechanism of IOD and its climatic effects is of great significance for climate prediction. This study mainly reviews the related research progress of IOD during the past 10 years， such as its basic characteristics， its relationship with El Ni?o-Southern Oscillation （ENSO） and the Asian summer monsoon， its climate effect， and its variation under the global warming. The relationship between IOD and ENSO is reflected in their mutual influence. The influence mechanism of different types of IOD on the development of ENSO is not clear and needs further investigation. A strong interaction between IOD and the Asian summer monsoon is found. The positive IOD and the summer monsoon circulation in the eastern Indian Ocean mutually promote， while the interaction between the IOD and the Indian summer monsoon needs further study. Furthermore， the extreme positive IOD will increase under the global warming， which has an important influence on extreme climatic events in China. Researches primarily focus on the effect of IOD alone or the combination effect of IOD and ENSO on extreme climatic events in China， but the synergistic effect between IOD and the mid-high latitude circulation system or the pan-tropical ocean on extreme climatic events in China needs further studies. A systematic review of IOD research progress during the past 10 years can provide a scientific basis for the future research of IOD.
In the process of ensemble data assimilation， due to the false correlation between the remote observation and the assimilation state， which affects the performance of DA， more attention has been paid to the localization methods. In addition， because of the limited ensemble size， it is easy to cause phenomena such as under-sampling and underestimation of covariance， which makes the filtering effect divergent. The fuzzy control algorithm is proposed， which is mainly used to judge the distance between the observation point and the state update point to assign the corresponding observation weight to the observation point， and then adjust the localization coefficient to update the background error covariance and observation error covariance， respectively. Thus， an effective state estimation is obtained. Based on BL and RL method， coupled with fuzzy control， the Background Covariance Fuzzy （BCF） and Fuzzy Observation Covariance （FOC） were proposed. We conducted an experiment on the Lorenz-96 model， and the BCF and the FOC method exhibited better assimilation effect with the small ensemble size and localization radius. By analyzing the Taylor diagram， it was found that the new algorithms had a high correlation with the observation point and small spatial variability. Finally， the robustness of BCF and FOC algorithms was further verified under the different dimensional fuzzy controller. It will provide a good research platform for data assimilation error processing in the future.
The Earth's inner core translational oscillation modes， also referred to as Slichter modes， are the basic normal modes of Earth's free oscillation， and the periods of the Slichter triplet are important physical quantities which can be used to determine the density jump across the inner core boundary， and the latter is of great research value to constraining the density structure of the deep interior of the Earth. However， there are not generally accepted conclusions so far about the Slichter modes' excitation mechanism and attenuation mechanism as well as the actual detecting results， which lead to great arguments. Hence， the determination of the eigenperiods has become one of the international challenges in fundamental geophysics. This paper firstly summarizes the basic theories of the Earth's inner core translational oscillation modes， including their dynamic equations and main solving theories and numerical methods， and overviews their theoretical periods under different Earth models using different solving theories. Secondly， the main hypotheses and conjectures about Slichter excitation mechanism and attenuation mechanism are discussed， and thereinto， degree-one surficial pressure flow acting in the core may excite the Slichter modes to an observable level. Finally， we review the research progress in the study of the detections of the Slichter triplet signals using the superconducting gravity data in the past 30 years， and discuss some potential future research subjects about the Slichter triplet detection. Therefore， from three different perspectives including exploration of excitation mechanism， fine preprocessing of superconducting gravity data， stacking and enhancement of extremely weak signals， the research breakthrough is expected to achieve reliable detection of the Slichter triplet signals.
The axisymmetric metal spring marine gravimeter is inevitably affected by carrier disturbance in dynamic measurement. Taking CHZ-Ⅱ marine gravimeter developed by Innovation Academy for Precision Measurement Science and Technology， Chinese Academy of Sciences as an example， we set up its measuring model by mechanical analysis under working condition， and analyzed the influence of carrier disturbance on capacitance micro displacement detection. The results show that the vertical disturbance acceleration of the carrier directly affects the output of capacitance micro displacement detection of CHZ-Ⅱ marine gravimeter. We also analyzed the influence of carrier disturbance on dynamic nonlinear error of the gravimeter. The conclusions are as follows： Disturbance acceleration from the carrier （such as survey ship， investigation boat） is the direct factor of the marine gravimeter's nonlinear error. The dynamic nonlinear error is positively correlated with the amplitude of disturbance acceleration and the frequency of disturbance acceleration. The research in this paper is of great significance to improving the dynamic measurement accuracy of marine gravimeter.
The measurement of gravitational acceleration plays a very important role， which is not only reflected in the basic research fields of metrology science， earthquake prevention and mitigation， but also in the practical application fields of pressure， force measurement， weighing instrument， geodesy and other professional fields. From 2016 to 2020， China National Institute of Metrology undertook and implemented the project of "Gravity Metrology Special Service". The project team went to Tibet， Xinjiang， Hong Kong and other regions， successfully completed the transmission of gravity acceleration in more than 50 stations， and initially established the National Gravity Metrology Reference Network. In the future， the team plans to further improve the National Gravimetric Reference Network.
The study of satellite gravity and the Earth's gravity field is an important research field of international geodesy， which not only drives the development of geodesy itself， but also obtains important scientific applications in related scientific fields. Taking the scientific papers in this field in the Web of Science core collection database during the 20 years from January 2000 to September 2020 as the research object， using the bibliometric methods and CiteSpace， this paper analyzes the current research status， development context and research hotspots of this field. The results show that the number of literatures on satellite gravity and the Earth's gravity field has been increasing year by year， and has maintained a high level since 2016， and the United States， Germany and China rank among the top three in the world. The top three research institutions with the largest number of papers published are Chinese Academy of Sciences， California Institute of Technology and NASA. China's research efforts in the fields of satellite gravity and the Earth's gravity field are relatively concentrated. The number of papers published by the Chinese Academy of Sciences， Wuhan University and the University of the Chinese Academy of Sciences accounts for 75.36% of China's total number in this field. Using the data of GRACE and the spherical harmonic function to construct high-precision Earth's gravity field model， as well as retrieving local mass change， is the current international research hotspot. Thanks to the satellite gravity observation data， the global gravity field model has been substantially improved.
Tidal friction leads to secular changes of lunar orbit and Earth's rotation. It is very important to accurately determine these parameters for understanding the evolution of the Earth-Moon system. The theoretical methods for solving these parameters are described. The analysis results of astronomical observations， low-Earth-orbit satellites observations， numerical tide models and Lunar Laser Range（LLR） data are reviewed and compared. It is found that low-Earth-orbit satellites and LLR data are more accurate than astronomical data， but the data span is shorter. With the accumulation of observational data， it can provide more reliable information about the long-term changes of the Lunar orbit and the Earth's rotation， improving the cognition of the changes of Earth-Moon space environment.
The marine area is a strategic area of China， and the building of a strong marine nation is an important part of the building of a world scientific and technological power. Adhering to the scientific and technological independence and self-improvement， and strengthening the marine national strategic scientific and technological power are an important means to promote the construction of a strong marine nation. This paper studies the development trend of first class scientific research institutions in the world's marine science and technology powers， analyzes China's construction layout of national scientific research institutions and scientific and technological innovation bases in the field of marine science， introduces the practice and experience of institutional reform and innovation in the field of marine science of the Chinese Academy of Sciences， and puts forward thoughts and suggestions on strengthening the national strategic scientific and technological strength in the marine field. To strengthen the national strategic scientific and technological strength in the marine field， we must focus on the most urgent and real national strategic needs， adhere to the concept of "doing something， leaving something"， make strategic layout in the key directions related to China's marine core interests， rely on forward-looking and strategic major scientific and technological projects， and give full play to the role of the state as the organizer of major scientific and technological innovation， so as to provide strong scientific and technological support for the construction of a maritime power.
Utilizing simultaneously continuous tidal gravity observations from a Burris spring gravimeter in the -848 m deep tunnel and a LCR-ET20 spring gravimeter， surficial and underground gravity noise levels at the deep geophysical experimental field in Huainan were preliminarily analysed. Analysis results show that the underground gravity noise level is lower than the surficial noise level below 1.7 mHz （period about 9.8 min）； especially in the gravimeter senstive frequency band （period over 3 h）， the underground gravity noise level is lower by two orders of magnititude， which fully demonstrates the low noise of ungerground environment at the deep geophysical experimental field in Huainan. Our results further indicate that the -848 m deep tunnel can provide both an ultra quiet environment for deep multi-physical fields observations and a perfect condition for the detection of weak geophysical signals.
