Background,aim,and scope Yardang is a kind of typical wind-eroded landform in arid zones both on Earth and other planets.Their geomorphic process records the surface changes and climate,which may play a vital role in ...Background,aim,and scope Yardang is a kind of typical wind-eroded landform in arid zones both on Earth and other planets.Their geomorphic process records the surface changes and climate,which may play a vital role in exploring the coupled landform-atmosphere system in arid zones.Recently,significant progresses have been made in this research field,and a review is still absent,which is the aim of the paper.Materials and methods Previous studies on the distribution,composition,morphology,and climatic driving force of yardang landform were reviewed.Results Earth yardang’s three evolutionary models were generalized:morphology evolution model,altitude evolution model and climate driven evolution model.Extraterrestrial yardang and its evolution are also summarized:the morphology is dominated by long ridges on Venus and Titan,and three yardang evolution hypotheses and an indirect dating method based on stratigraphic contact have been studied on Mars.Discussion In this study,firstly,the definition and morphology of yardang were described to define its characteristics.Secondly,we argue that yardang evolution has two dimensions:short-term variation and longterm variation.In the short-term variation,the morphological evolution of yardang on earth can be divided into four stages:embryonic stage,juvenile stage,mature stage,and demise stage.In the long-term variation,the evolution of yardang on earth is climate-driven,i.e.,it is controlled by atmospheric circulation changes during glacial-interglacial periods.Thirdly,yardang research on extraterrestrial bodies was also summarized:yardang has been found on Mars,Venus,and Titan,and the research focus by far are on geomorphology only.Conclusions(1)Yardang landform is an erosion landform with alternating ridges and troughs,with main form of whale back shape and fluctuations in the range of aspect ratios;(2)the short-term variation of yardang is manifested in its morphological evolution and height change,while the long-term variation is climate-driven;(3)based on Earth yardang,extraterrestrial yardang research has been carried out on Mars,Venus,and Titan.Recommendations and perspectives We then proposed that:(1)yardang formation ages,due to the erosion characteristics,are difficult to constraint;(2)the wind erosion capacity in the yardang areas might have been severely underestimated,making it essential to re-evaluate the previous paleoclimate reconstruction in the closed basins with limited chronological data;(3)yardang evolution is driven by climate change,but the coupling relationship between the yardang geomorphy and the air circulation is still unclear.Finally,future research directions:(1)more chronological data are needed,as well as the wind erosion capacity for yardang initiation and development;(2)the co-evolution of mid-low latitude landforms involved in yardang long-term variation and its relationship with global atmospheric circulation.展开更多
The ocean surface currents are reconstructed from the satellite remote sensing data containing altimeter-derived sea surface height and QuikSCAT satellite-derived wind data. Based on the method proposed by Lagerloef, ...The ocean surface currents are reconstructed from the satellite remote sensing data containing altimeter-derived sea surface height and QuikSCAT satellite-derived wind data. Based on the method proposed by Lagerloef, a global weekly 0.5°×0.5°ocean surface current product was obtained over the period 2000 - 2008 by combining the geostrophic currents estimated from sea surface height with Ekman current estimated from the wind stress. Particularly, weight functions were introduced when calculating the Ekman currents to eliminate the discontinuity near 25°S and 25°N. These satellite-derived currents have been compared with TAO current meter and the SCUD product, respectively. The comparison showed that satellite-derived currents not only could capture the characteristics of ocean surface currents but also had high accuracy and reliability. The result showed that this innovatory method was effective.展开更多
The present study investigates the difference in interdecadal variability of the spring and summer sensible heat fluxes over Northwest China by using station observations from 1960 to 2000. It was found that the sprin...The present study investigates the difference in interdecadal variability of the spring and summer sensible heat fluxes over Northwest China by using station observations from 1960 to 2000. It was found that the spring sensible heat flux over Northwest China was greater during the period from the late 1970s to the 1990s than during the period from the 1960s to the mid-1970s. The summer sensible heat flux was smaller in the late 1980s through the 1990s than it was in the 1970s through the early 1980s. Both the spring and summer land-air temperature differences over Northwest China displayed an obvious interdecadal increase in the late 1970s. Both the spring and summer surface wind speeds experienced an obvious interdecadal weakening in the late 1970s. The change in the surface wind speed played a more important role in the interdecadal variations in sensible heat flux during the summer, whereas the change in the land-air temperature difference was more important for the interdecadal variations in sensible heat flux in the spring. This difference was related to seasonal changes in the mean land-air temperature difference and the surface wind speed. Further analysis indicated that the increase in the spring land surface temperature in Northwest China was related to an increase in surface net radiation.展开更多
As China＇s energy strategy moving westward, the surface movement and deformation characteristics due to high-intensive coal mining in the windy and sandy region become a research hotspot. Surface movement observation...As China＇s energy strategy moving westward, the surface movement and deformation characteristics due to high-intensive coal mining in the windy and sandy region become a research hotspot. Surface movement observation stations were established to monitor movement and deformation in one super-large working face. Based on field measurements, the surface movement and deformation characteristics were obtained, including angle parameters, subsidence prediction parameters, etc. Besides, the angle and subsidence prediction parameters in similar mining areas are summarized; the mechanism of surface movement and deformation was analyzed with the combination of key stratum theory, mining and geological conditions. The research also indicates that compared with conventional working faces, uniform subsidence area of the subsidence trough in the windy and sandy region is larger, the trough margins are relative steep and deformation values present convergence at the margins, the extent of the trough shrink towards the goaf and the influence time of mining activities lasts shorter; the overlying rock movement and breaking characteristics presents regional particularity in the study area, while the single key stratum, thin bedrock and thick sand that can rapidly propagate movement and deformation are the deep factors, contributing to it.展开更多
Based on the physical concept of heat energy of pre-ignition,a new fire susceptibility index (FSI) is used to estimate forest fire risk. This physical basis allows calculation of ignition probabilities and comparisons...Based on the physical concept of heat energy of pre-ignition,a new fire susceptibility index (FSI) is used to estimate forest fire risk. This physical basis allows calculation of ignition probabilities and comparisons of fire risk across eco-regions. The computation of the index requires inputs of fuel temperature and fuel moisture content (FMC),both of which can be estimated using remote sensing data. While ASTER data for land surface temperatures (LST) was used as proxys for fuel temperatures,fuel moisture content is estimated by regression technique utilizing the ratio NDVI/LST of ASTER data. FSIs are computed in peninsular Malaysia for nine days before the fires of 2004 and 2005 and validated with fire occurrence data. Results show that the FSI increases as the day approaches the fire day. This trend can be observed clearly about four days before the day of fire. It suggests that FSI can be a good estimator of fire risk. The physical basis provides a more meaningful FSI,allows calculation of ignition probabilities and facilitates the development of a future class of fire risk models. FSI can be used to compare fire risk across different eco-regions and time periods. FSI retains the flexibility to be localized to a vegetation type or eco-regions for improved performance.展开更多
Based on the QuikSCAT data, the features of surface wind distribution of the typhoon Vongfong landfall process are analyzed. We have also studied the variance spectral configuration of the surface wind field using DCT...Based on the QuikSCAT data, the features of surface wind distribution of the typhoon Vongfong landfall process are analyzed. We have also studied the variance spectral configuration of the surface wind field using DCT (Discrete Cosine Transform). The conclusions are as follows: The near-surface wind field is highly asymmetric; the variance components of asymmetric surface wind field depend mainly on the airflow direction of wavenumber 1 and 2. When the typhoon moves west, there are two wave spectral centers lining up in the zonal direction, mainly the airflow from zonal wavenumber 2 and meridional wavenumber 2; when it moves north, there are two wave spectral centers in a meridional array, mainly the airflow from zonal wavenumber 1 and meridional wavenumber 2. The airflow for wavenumber 1 mainly contributes to the variance of the tangential wind while that for wavenumber 2 to the variance of the radial wind. The asymmetrical distribution changes with the large-scale environment and self-rotating circulation around the typhoon. When it approached land, the associated gale appears in front portion in the advancing direction of the storm. It is in effect similar to the model of Chen Lian-shou for typhoon-related gales NNW on the left front portion and SE on the right front portion.展开更多
This paper presents numerical studies on the effects of atmospheric pressure fluctuations on hill-side coal fires and their surface anomalies. Based on the single-particle reaction–diffusion model, a formula to estim...This paper presents numerical studies on the effects of atmospheric pressure fluctuations on hill-side coal fires and their surface anomalies. Based on the single-particle reaction–diffusion model, a formula to estimate oxygen consumption rate at high temperature controlled by oxygen transport is proposed.Daily fluctuant atmospheric pressure was imposed on boundaries, including the abandoned gallery and cracks. Simulated results show that the effects of atmospheric pressure fluctuations on coal fires and surface anomalies depend on two factors: the fluctuant amplitude and the pressure difference between inlet(s) and outlet(s) of the air ventilation system. If the pressure difference is close to the fluctuant amplitude, atmospheric pressure fluctuations greatly enhance gas flow motion and temperatures of the combustion zone and outtake(s). If the pressure difference is much larger than the fluctuant amplitude, atmospheric pressure fluctuations exert no impact on underground coal fires and surface anomalies.展开更多
Land-surface conditions, such as surface roughness and SWC （soil-water content）, control the saltation activity and dust emission in northeast Asia. Information on spatial and temporal changes in surface SWC is need...Land-surface conditions, such as surface roughness and SWC （soil-water content）, control the saltation activity and dust emission in northeast Asia. Information on spatial and temporal changes in surface SWC is needed for dust-modeling systems used to predict dust events with the aim of preventing the damage they cause. A MTVDI （modified temperature-vegetation dryness index） was tested to see if it could reproduce the surface SWC observed in Zhangye, China, and the Tottori Sand Dunes of Japan, and the threshold wind speed at the Tottori Sand Dunes. MTVDI was calculated from land-surface temperature using the MODIS （moderate resolution imaging spectroradiometer） product, and the aerodynamic minimum and maximum surface temperatures were estimated based on meteorological data. A greater correlation is seen between MTVDI and SWC than between SWC from AMSR-E （advanced microwave scanning radiometer-earth observing system） and SWC in Zhangye. The threshold wind speed for saltation activity decreased with increasing MTVDI, that is, with drying of the soil surface of the Tottori Sand Dunes. The correlation between MTVDI and threshold wind speed is statistically significant （R2 = 0.2987）.展开更多
Hurricane fighting devices are recommended. The devices belong to the sphere of artificial weather conditions changes over the Earth surface. The purpose of the paper is the development of the original design of devic...Hurricane fighting devices are recommended. The devices belong to the sphere of artificial weather conditions changes over the Earth surface. The purpose of the paper is the development of the original design of devices for hurricane fighting. The decreasing of hurricane energy takes place under the reaction of directed air current against the hurricane air current mass. The air current is created by propellers, located in cylindrical frames with nozzles at a current exit. The devices function due to horizontal hurricanes air current. The essential factor lies in absence of influence on ecology. The devices are of simple constructions, it results in simplification of their production technology and lower cost,展开更多
During the 17th Century, Parral City in the Chihuahua State in Mexico was one of the most important miner zones in the whole world. After more than three centuries important amounts of residuals, known as tailings, wi...During the 17th Century, Parral City in the Chihuahua State in Mexico was one of the most important miner zones in the whole world. After more than three centuries important amounts of residuals, known as tailings, with high contents of heavy metals were generated. These residuals are a potential risk for the environment and human health. Given to that, it decided to carry out the analysis of the concentrations of cadmium, lead, chromium, zinc and arsenics, in topsoil samples susceptible of airborne transport and accumulation in risky zones （populated areas）. A 120 kin： area was selected, this include Parral City and its surroundings. From this area 30 samples were obtained. For this purpose, Atomic Absorption Spectroscopy technique was used, expecting high concentrations of heavy metals, above the permit limits, since several studies carried out in the same region, as in San Francisco del Oro Chihuahua, show that the concentrations of all the elements sampled, in topsoil, were above the limits. The analysis in the space distribution of the heavy metal detected will allow us to set the points with the highest susceptibility to the accumulation of those pollutants and to propose mitigation measures and control.展开更多
文摘Background,aim,and scope Yardang is a kind of typical wind-eroded landform in arid zones both on Earth and other planets.Their geomorphic process records the surface changes and climate,which may play a vital role in exploring the coupled landform-atmosphere system in arid zones.Recently,significant progresses have been made in this research field,and a review is still absent,which is the aim of the paper.Materials and methods Previous studies on the distribution,composition,morphology,and climatic driving force of yardang landform were reviewed.Results Earth yardang’s three evolutionary models were generalized:morphology evolution model,altitude evolution model and climate driven evolution model.Extraterrestrial yardang and its evolution are also summarized:the morphology is dominated by long ridges on Venus and Titan,and three yardang evolution hypotheses and an indirect dating method based on stratigraphic contact have been studied on Mars.Discussion In this study,firstly,the definition and morphology of yardang were described to define its characteristics.Secondly,we argue that yardang evolution has two dimensions:short-term variation and longterm variation.In the short-term variation,the morphological evolution of yardang on earth can be divided into four stages:embryonic stage,juvenile stage,mature stage,and demise stage.In the long-term variation,the evolution of yardang on earth is climate-driven,i.e.,it is controlled by atmospheric circulation changes during glacial-interglacial periods.Thirdly,yardang research on extraterrestrial bodies was also summarized:yardang has been found on Mars,Venus,and Titan,and the research focus by far are on geomorphology only.Conclusions(1)Yardang landform is an erosion landform with alternating ridges and troughs,with main form of whale back shape and fluctuations in the range of aspect ratios;(2)the short-term variation of yardang is manifested in its morphological evolution and height change,while the long-term variation is climate-driven;(3)based on Earth yardang,extraterrestrial yardang research has been carried out on Mars,Venus,and Titan.Recommendations and perspectives We then proposed that:(1)yardang formation ages,due to the erosion characteristics,are difficult to constraint;(2)the wind erosion capacity in the yardang areas might have been severely underestimated,making it essential to re-evaluate the previous paleoclimate reconstruction in the closed basins with limited chronological data;(3)yardang evolution is driven by climate change,but the coupling relationship between the yardang geomorphy and the air circulation is still unclear.Finally,future research directions:(1)more chronological data are needed,as well as the wind erosion capacity for yardang initiation and development;(2)the co-evolution of mid-low latitude landforms involved in yardang long-term variation and its relationship with global atmospheric circulation.
基金supported by the National Natural Science Foundation of China(No.41306010,41276088 and 41206002)
文摘The ocean surface currents are reconstructed from the satellite remote sensing data containing altimeter-derived sea surface height and QuikSCAT satellite-derived wind data. Based on the method proposed by Lagerloef, a global weekly 0.5°×0.5°ocean surface current product was obtained over the period 2000 - 2008 by combining the geostrophic currents estimated from sea surface height with Ekman current estimated from the wind stress. Particularly, weight functions were introduced when calculating the Ekman currents to eliminate the discontinuity near 25°S and 25°N. These satellite-derived currents have been compared with TAO current meter and the SCUD product, respectively. The comparison showed that satellite-derived currents not only could capture the characteristics of ocean surface currents but also had high accuracy and reliability. The result showed that this innovatory method was effective.
基金supported by the National Natural Science Foundation of China (Grant No. 40730952)the National Basic Research Program of China (Grant No. 2009CB421405)the Program of Knowledge Innovation for the third period, the Chinese Academy of Sciences (Grant No. KZCX2-YW-220), and IAP07414
文摘The present study investigates the difference in interdecadal variability of the spring and summer sensible heat fluxes over Northwest China by using station observations from 1960 to 2000. It was found that the spring sensible heat flux over Northwest China was greater during the period from the late 1970s to the 1990s than during the period from the 1960s to the mid-1970s. The summer sensible heat flux was smaller in the late 1980s through the 1990s than it was in the 1970s through the early 1980s. Both the spring and summer land-air temperature differences over Northwest China displayed an obvious interdecadal increase in the late 1970s. Both the spring and summer surface wind speeds experienced an obvious interdecadal weakening in the late 1970s. The change in the surface wind speed played a more important role in the interdecadal variations in sensible heat flux during the summer, whereas the change in the land-air temperature difference was more important for the interdecadal variations in sensible heat flux in the spring. This difference was related to seasonal changes in the mean land-air temperature difference and the surface wind speed. Further analysis indicated that the increase in the spring land surface temperature in Northwest China was related to an increase in surface net radiation.
基金Financial supports for this work, are provided by the National Natural Science Foundation of China （NSFC） ＆ Shenhua Group Corporation Limited key support project of the coal joint fund （U1361203） and NSFC under Grant No. 41501562. Thanks are also due to some participants for rendering assistant cooperation during studies.
文摘As China＇s energy strategy moving westward, the surface movement and deformation characteristics due to high-intensive coal mining in the windy and sandy region become a research hotspot. Surface movement observation stations were established to monitor movement and deformation in one super-large working face. Based on field measurements, the surface movement and deformation characteristics were obtained, including angle parameters, subsidence prediction parameters, etc. Besides, the angle and subsidence prediction parameters in similar mining areas are summarized; the mechanism of surface movement and deformation was analyzed with the combination of key stratum theory, mining and geological conditions. The research also indicates that compared with conventional working faces, uniform subsidence area of the subsidence trough in the windy and sandy region is larger, the trough margins are relative steep and deformation values present convergence at the margins, the extent of the trough shrink towards the goaf and the influence time of mining activities lasts shorter; the overlying rock movement and breaking characteristics presents regional particularity in the study area, while the single key stratum, thin bedrock and thick sand that can rapidly propagate movement and deformation are the deep factors, contributing to it.
基金Projects KSTAS/MACRES/T/2/2004 supported by the Airborne Remote Sensing (MARS) Program of Malaysia, 4067113040671122 by the National Natural Science Foundation of China
文摘Based on the physical concept of heat energy of pre-ignition,a new fire susceptibility index (FSI) is used to estimate forest fire risk. This physical basis allows calculation of ignition probabilities and comparisons of fire risk across eco-regions. The computation of the index requires inputs of fuel temperature and fuel moisture content (FMC),both of which can be estimated using remote sensing data. While ASTER data for land surface temperatures (LST) was used as proxys for fuel temperatures,fuel moisture content is estimated by regression technique utilizing the ratio NDVI/LST of ASTER data. FSIs are computed in peninsular Malaysia for nine days before the fires of 2004 and 2005 and validated with fire occurrence data. Results show that the FSI increases as the day approaches the fire day. This trend can be observed clearly about four days before the day of fire. It suggests that FSI can be a good estimator of fire risk. The physical basis provides a more meaningful FSI,allows calculation of ignition probabilities and facilitates the development of a future class of fire risk models. FSI can be used to compare fire risk across different eco-regions and time periods. FSI retains the flexibility to be localized to a vegetation type or eco-regions for improved performance.
基金Special Fund Project for Social Benefit Research Study on the Monitoring and Predicting Techniques of Desasters by landding typhoons in China (2002DCA20026-01) Knowledge Innovation Project of The Chinese Academy of Sciences (ZKCXZ-SW-210)
文摘Based on the QuikSCAT data, the features of surface wind distribution of the typhoon Vongfong landfall process are analyzed. We have also studied the variance spectral configuration of the surface wind field using DCT (Discrete Cosine Transform). The conclusions are as follows: The near-surface wind field is highly asymmetric; the variance components of asymmetric surface wind field depend mainly on the airflow direction of wavenumber 1 and 2. When the typhoon moves west, there are two wave spectral centers lining up in the zonal direction, mainly the airflow from zonal wavenumber 2 and meridional wavenumber 2; when it moves north, there are two wave spectral centers in a meridional array, mainly the airflow from zonal wavenumber 1 and meridional wavenumber 2. The airflow for wavenumber 1 mainly contributes to the variance of the tangential wind while that for wavenumber 2 to the variance of the radial wind. The asymmetrical distribution changes with the large-scale environment and self-rotating circulation around the typhoon. When it approached land, the associated gale appears in front portion in the advancing direction of the storm. It is in effect similar to the model of Chen Lian-shou for typhoon-related gales NNW on the left front portion and SE on the right front portion.
文摘This paper presents numerical studies on the effects of atmospheric pressure fluctuations on hill-side coal fires and their surface anomalies. Based on the single-particle reaction–diffusion model, a formula to estimate oxygen consumption rate at high temperature controlled by oxygen transport is proposed.Daily fluctuant atmospheric pressure was imposed on boundaries, including the abandoned gallery and cracks. Simulated results show that the effects of atmospheric pressure fluctuations on coal fires and surface anomalies depend on two factors: the fluctuant amplitude and the pressure difference between inlet(s) and outlet(s) of the air ventilation system. If the pressure difference is close to the fluctuant amplitude, atmospheric pressure fluctuations greatly enhance gas flow motion and temperatures of the combustion zone and outtake(s). If the pressure difference is much larger than the fluctuant amplitude, atmospheric pressure fluctuations exert no impact on underground coal fires and surface anomalies.
文摘Land-surface conditions, such as surface roughness and SWC （soil-water content）, control the saltation activity and dust emission in northeast Asia. Information on spatial and temporal changes in surface SWC is needed for dust-modeling systems used to predict dust events with the aim of preventing the damage they cause. A MTVDI （modified temperature-vegetation dryness index） was tested to see if it could reproduce the surface SWC observed in Zhangye, China, and the Tottori Sand Dunes of Japan, and the threshold wind speed at the Tottori Sand Dunes. MTVDI was calculated from land-surface temperature using the MODIS （moderate resolution imaging spectroradiometer） product, and the aerodynamic minimum and maximum surface temperatures were estimated based on meteorological data. A greater correlation is seen between MTVDI and SWC than between SWC from AMSR-E （advanced microwave scanning radiometer-earth observing system） and SWC in Zhangye. The threshold wind speed for saltation activity decreased with increasing MTVDI, that is, with drying of the soil surface of the Tottori Sand Dunes. The correlation between MTVDI and threshold wind speed is statistically significant （R2 = 0.2987）.
文摘Hurricane fighting devices are recommended. The devices belong to the sphere of artificial weather conditions changes over the Earth surface. The purpose of the paper is the development of the original design of devices for hurricane fighting. The decreasing of hurricane energy takes place under the reaction of directed air current against the hurricane air current mass. The air current is created by propellers, located in cylindrical frames with nozzles at a current exit. The devices function due to horizontal hurricanes air current. The essential factor lies in absence of influence on ecology. The devices are of simple constructions, it results in simplification of their production technology and lower cost,
文摘During the 17th Century, Parral City in the Chihuahua State in Mexico was one of the most important miner zones in the whole world. After more than three centuries important amounts of residuals, known as tailings, with high contents of heavy metals were generated. These residuals are a potential risk for the environment and human health. Given to that, it decided to carry out the analysis of the concentrations of cadmium, lead, chromium, zinc and arsenics, in topsoil samples susceptible of airborne transport and accumulation in risky zones （populated areas）. A 120 kin： area was selected, this include Parral City and its surroundings. From this area 30 samples were obtained. For this purpose, Atomic Absorption Spectroscopy technique was used, expecting high concentrations of heavy metals, above the permit limits, since several studies carried out in the same region, as in San Francisco del Oro Chihuahua, show that the concentrations of all the elements sampled, in topsoil, were above the limits. The analysis in the space distribution of the heavy metal detected will allow us to set the points with the highest susceptibility to the accumulation of those pollutants and to propose mitigation measures and control.
