With global warming and the intensification of human activities, frozen soils continue to melt, leading to the formation of thermokarst collapses and thermokarst lakes. The thawing of permafrost results in the microbi...With global warming and the intensification of human activities, frozen soils continue to melt, leading to the formation of thermokarst collapses and thermokarst lakes. The thawing of permafrost results in the microbial decomposition of large amounts of frozen organic carbon (C), releasing greenhouse gases such as carbon dioxide (CO_(2)) and methane (CH4). However, little research has been done on the thermo-water-vapor-carbon coupling process in permafrost, and the interactions among hydrothermal transport, organic matter decomposition, and CO_(2) transport processes in permafrost remain unclear. We considered the decomposition and release of organic C and established a coupled thermo-water-vapor-carbon model for permafrost based on the study area located in the Beiluhe region of the Qingzang Plateau, China. The model established accurately reflected changes in permafrost temperature, moisture, and C fluxes. Dramatic changes in temperature and precipitation in the warm season led to significant soil water and heat transport, CO_(2) transport, and organic matter decomposition. During the cold season, however, the soil froze, which weakened organic matter decomposition and CO_(2) transport. The sensitivity of soil layers to changes in the external environment varied with depth. Fluctuations in energy, water, and CO_(2) fluxes were greater in shallow soil layers than in deeper ones. The latent heat of water-vapor and water-ice phase changes played a crucial role in regulating the temperature of frozen soil. The low content of soil organic matter in the study area resulted in a smaller influence of the decomposition heat of soil organic matter on soil temperature, compared to the high organic matter content in other soil types (such as peatlands).展开更多
In the visible spectrum, the atmospheric attenuations to sunlight mainly include aerosol scattering, atmospheric molecule Rayleigh scattering and ozone absorption, while in the near-infrared spectrum (from 650 nm to 1...In the visible spectrum, the atmospheric attenuations to sunlight mainly include aerosol scattering, atmospheric molecule Rayleigh scattering and ozone absorption, while in the near-infrared spectrum (from 650 nm to 1 000 nm), we must take water-vapor absorption into account. Based on the atmospheric correction theory, using spectrum irradiance data measured by Instantaneous Ground spectrometer, ozone content measured by Microtops Ⅱozone monitor, water-vapor content and aerosol optical thickness measured by sun photometer, we give a new way to study water-vapor absorption to sunlight, and the result shows that the main peak values of water-vapor absorption coefficients are 0.025 cm-1, 0.073 cm-1, 0.124 cm-1, 0.090 cm-1, 0.141 cm-1 and 0.417 cm-1, which respectively lie at 692 nm, 725 nm, 761 nm, 818 nm, 912 nm and 937 nm.展开更多
To analyze the mechanism by which water vapor increase leads to cooling in the stratosphere, the effects of water-vapor increases on temperature in the stratosphere were simulated using the two-dimensional, interactiv...To analyze the mechanism by which water vapor increase leads to cooling in the stratosphere, the effects of water-vapor increases on temperature in the stratosphere were simulated using the two-dimensional, interactive chemical dynamical radiative model （SOCRATES） of NCAR. The results indicate that increases in stratospheric water vapor lead to stratospheric cooling, with the extent of cooling increasing with height, and that cooling in the middle stratosphere is stronger in Arctic regions. Analysis of the radiation process showed that infrared radiative cooling by water vapor is a pivotal factor in middle-lower stratospheric cooling. However, in the upper stratosphere （above 45 km）, infrared radiation is not a factor in cooling; there, cooling is caused by the decreased solar radiative heating rate resulting from ozone decrease due to increased stratospheric water vapor. Dynamical cooling is important in the middle-upper stratosphere, and dynamical feedback to temperature change is more distinct in the Northern Hemisphere middle-high latitudes than in other regions and signiffcantly affects temperature and ozone in winter over Arctic regions. Increasing stratospheric water vapor will strengthen ozone depletion through the chemical process. However, ozone will increase in the middle stratosphere. The change in ozone due to increasing water vapor has an important effect on the stratospheric temperature change.展开更多
The China Advanced Research Reactor (CARR) is scheduled to be operated in the autumn of 2008.In this paper,we report preparations for installing the neutron radiography instrument (NRI) and for utilizing it efficientl...The China Advanced Research Reactor (CARR) is scheduled to be operated in the autumn of 2008.In this paper,we report preparations for installing the neutron radiography instrument (NRI) and for utilizing it efficiently. The 2-D relative neutron intensity profiles for the water-vapor two-phase flow inside the robe were obtained using the MCNP code without influence of y-ray and electronic-noise.The MCNP simulation of the 2-D neutron intensity profile for the water-vapor two-phase flow was demonstrated.The simulated 2-D neutron intensity profiles could be used as the benchmark data base by calibrating part of the data measured by the CARR-NRI.The 3-D objective images allow us to understand the flow pattern more clearly and it is reconstructed using the MATLAB through the threshold transformation techniques.And thus it is concluded that the MCNP code and the MATLAB are very useful for constructing the benchmark data base for the investigation of the water-vapor two-phase flow using the CARR-NRI.展开更多
2024/2025年前冬,即2024年12月1日—2025年1月15日,北半球季风区发生了1979年以来极为严重的干旱事件,其中中国东部地区尤为显著。此次事件对中国东部地区的经济发展和生态系统都造成了严重的影响。本文基于ERA5再分析资料,深入探究了...2024/2025年前冬,即2024年12月1日—2025年1月15日,北半球季风区发生了1979年以来极为严重的干旱事件,其中中国东部地区尤为显著。此次事件对中国东部地区的经济发展和生态系统都造成了严重的影响。本文基于ERA5再分析资料,深入探究了此次中国东部极端干旱事件的成因及潜在物理机制。研究结果表明,造成此次极端干旱事件的直接原因是中国东部水汽异常辐散。从环流角度来看,北太平洋的异常气旋以及青藏高原南侧的异常反气旋导致中国东部主要受干冷的偏北风影响,进而引起中国东部和南方地区水汽辐散异常和降水偏少,诱发并维持了此次极端干旱事件。进一步研究表明,大气内部模态环北半球遥相关型可能是北太平洋气旋异常形成的主要原因,青藏高原前期秋季积雪异常偏少是青藏高原上空的深厚暖高压形成的原因,二者导致中国东部地区持续受异常偏北气流控制,进而引发局地降水减少。而2024/2025年前冬弱La Ni a型海温异常则通过调控Walker环流,引起南海上空异常气旋的形成,进一步抑制了中国东部地区的降水。在全球变暖背景下,更剧烈的水汽辐合、辐散可能会引发更严重的季风区极端降水或干旱事件,这为复杂气候背景下区域性干旱事件的预测提供了一定的理论依据。展开更多
现有GNSS水汽层析研究主要聚焦于如何提升卫星观测数据利用率,但在卫星信号数据优选方面研究较少,导致穿过同一组网格集的层析观测方程线性近似且方程系数矩阵列向量元素多数为零,水汽层析模型病态严重。针对该现状,本文提出一种GNSS卫...现有GNSS水汽层析研究主要聚焦于如何提升卫星观测数据利用率,但在卫星信号数据优选方面研究较少,导致穿过同一组网格集的层析观测方程线性近似且方程系数矩阵列向量元素多数为零,水汽层析模型病态严重。针对该现状,本文提出一种GNSS卫星信号自适应优选的水汽层析方法,解决层析模型设计矩阵零元素较多和层析模型病态的难题。该方法基于网格覆盖率最大原则确定层析区域水平网格划分,并发展联合卫星高度角与方位角阈值的卫星信号自适应优选方法,克服水汽层析模型观测方程线性近似的难题。本文选取香港地区2013年5月2日—2013年5月7日共6 d 12个GNSS测站及1个无线电探空站数据为例进行试验。与现有方法相比,本文方法能在降低卫星信号利用率的同时保证网格覆盖率,克服相似卫星信号造成层析模型设计矩阵病态的现状。以无线电探空数据为真值,发现本文方法反演水汽密度廓线的平均RMS、MAE和Bias分别为1.03、0.80和0.13 g/m^(3),优于传统方法的1.25、0.97和0.10 g/m^(3),其RMS改善率为20.78%;此外,本文方法在模型解算效率方面也优于传统方法,其模型计算效率平均提升9.51%。展开更多
Based on the remote sensing data, the radiosonde data and precipitation data observed by weather stations, distributions of atmospheric water-vapor and cloud motion wind over the Qilian Mountains are analyzed. Moreove...Based on the remote sensing data, the radiosonde data and precipitation data observed by weather stations, distributions of atmospheric water-vapor and cloud motion wind over the Qilian Mountains are analyzed. Moreover, on the basis of water-vapor and cloud motion wind analyses, relations of atmospheric water-vapor distribution with precipitation~ atmospheric circulation, and terrain are investigated. The results show that distributions of atmospheric water-vapor and precipitation in the Qilian Mountains are affected by the westerly belt, the southerly monsoon （the South Asian monsoon and plateau monsoon）, and the East Asian monsoon. In the northwest Qilian Mountains, water-vapor and precipitation are entirely affected by the westerly belt, and there is no other direction water-vapor transport except westerly watervapor flux, hence, the northwest region is regarded as the westerly belt region. In the south and middle of the mountaili, water-vapor is mainly controlled by the southerly monsoon, 37.7% of the total watervapor is from the south, especially in summer, the southerly water-vapor flux accounts for 55.9% of the total, and furthermore the water-vapor content in the southerly flow is more than that in the westerly flow. The southerly monsoon water-vapor is influenced by the South Asian monsoon from the Indian Ocean and the plateau monsoon in the Qinghai-Tibetan Plateau, thus, the south and middle region is called southerly monsoon region. But in the northeast Qilian Mountains, the East Asian monsoon is the main climate system affecting the water-vapor. Besides west and northwest water-vapor fluxes, there are a lot of easterly water-vapor fluxes in summer. The frequency of easterly cloud motion winds in summer half year accounts for 27.1% of the total, though the frequency is not high, it is the main water-vapor source of summer precipitation in this region, therefore, the northwest region is a marginal region of the East Asian monsoon. On the other hand, atmospheric water-vapor, precipitation, and conversion rate of water-vapor into precipitation are closely related with altitudes and circulation system. Generally, there is a peak value of water-vapor content at the altitude from 3500 to 4500 m on the windward slope, but on the leeward slope, water-vapor monotonically decreases with altitude descending except for that in the East Asian monsoon region. Water-vapor on the leeward is much less than that on the windward slope~ and the maximal difference in water-vapor content between the two sides may reach about 4.49 kg m-2. Either the values of water-vapor content, precipitation or the conversion rate of water-vapor into precipitation all reach their maxima in the East Asian monsoon regions, and correspondingly the peak value of water-vapor on the windward is also large and occurs at a lower altitude in comparison with other two regions.展开更多
The supercavitation has attracted a growing interest because of its potential for high-speed vehicle maneuvering and drag reduction. To better understand the reverse flow characteristics of a water-vapor mixture in su...The supercavitation has attracted a growing interest because of its potential for high-speed vehicle maneuvering and drag reduction. To better understand the reverse flow characteristics of a water-vapor mixture in supercavitating flows around a hydrofoil, a numerical simulation is conducted using a unified supercavitation model, which combines a modified RNG k-~ turbulence model and a cavitation one. By comparing the related experimental results, the reverse motion of the water-vapor mixture is found in the cavitation area in all supercavitation stages. The inverse pressure gradient leads to reverse pressure fluctuations in the cavity, followed by the reverse motion of the water-vapor two-phase interface. Compared with the water-vapor mixture area at the back of the cavity, the pressure in the vapor area is inversely and slowly reduced, a higher-pressure gradient occurs near the cavity boundary.展开更多
基金the financial support from the National Natural Science Foundation of China(No.U22A20596).
文摘With global warming and the intensification of human activities, frozen soils continue to melt, leading to the formation of thermokarst collapses and thermokarst lakes. The thawing of permafrost results in the microbial decomposition of large amounts of frozen organic carbon (C), releasing greenhouse gases such as carbon dioxide (CO_(2)) and methane (CH4). However, little research has been done on the thermo-water-vapor-carbon coupling process in permafrost, and the interactions among hydrothermal transport, organic matter decomposition, and CO_(2) transport processes in permafrost remain unclear. We considered the decomposition and release of organic C and established a coupled thermo-water-vapor-carbon model for permafrost based on the study area located in the Beiluhe region of the Qingzang Plateau, China. The model established accurately reflected changes in permafrost temperature, moisture, and C fluxes. Dramatic changes in temperature and precipitation in the warm season led to significant soil water and heat transport, CO_(2) transport, and organic matter decomposition. During the cold season, however, the soil froze, which weakened organic matter decomposition and CO_(2) transport. The sensitivity of soil layers to changes in the external environment varied with depth. Fluctuations in energy, water, and CO_(2) fluxes were greater in shallow soil layers than in deeper ones. The latent heat of water-vapor and water-ice phase changes played a crucial role in regulating the temperature of frozen soil. The low content of soil organic matter in the study area resulted in a smaller influence of the decomposition heat of soil organic matter on soil temperature, compared to the high organic matter content in other soil types (such as peatlands).
基金Financial support was provided by The National High Technology Research and Development Program of China(863 Program):No 2001AA633030 and 2001AA633080.
文摘In the visible spectrum, the atmospheric attenuations to sunlight mainly include aerosol scattering, atmospheric molecule Rayleigh scattering and ozone absorption, while in the near-infrared spectrum (from 650 nm to 1 000 nm), we must take water-vapor absorption into account. Based on the atmospheric correction theory, using spectrum irradiance data measured by Instantaneous Ground spectrometer, ozone content measured by Microtops Ⅱozone monitor, water-vapor content and aerosol optical thickness measured by sun photometer, we give a new way to study water-vapor absorption to sunlight, and the result shows that the main peak values of water-vapor absorption coefficients are 0.025 cm-1, 0.073 cm-1, 0.124 cm-1, 0.090 cm-1, 0.141 cm-1 and 0.417 cm-1, which respectively lie at 692 nm, 725 nm, 761 nm, 818 nm, 912 nm and 937 nm.
基金supported by the National Basic Research Program of China (2010CB428603)the National Natural Science Foundation of China (40505008, 40705014, and 40633015)
文摘To analyze the mechanism by which water vapor increase leads to cooling in the stratosphere, the effects of water-vapor increases on temperature in the stratosphere were simulated using the two-dimensional, interactive chemical dynamical radiative model （SOCRATES） of NCAR. The results indicate that increases in stratospheric water vapor lead to stratospheric cooling, with the extent of cooling increasing with height, and that cooling in the middle stratosphere is stronger in Arctic regions. Analysis of the radiation process showed that infrared radiative cooling by water vapor is a pivotal factor in middle-lower stratospheric cooling. However, in the upper stratosphere （above 45 km）, infrared radiation is not a factor in cooling; there, cooling is caused by the decreased solar radiative heating rate resulting from ozone decrease due to increased stratospheric water vapor. Dynamical cooling is important in the middle-upper stratosphere, and dynamical feedback to temperature change is more distinct in the Northern Hemisphere middle-high latitudes than in other regions and signiffcantly affects temperature and ozone in winter over Arctic regions. Increasing stratospheric water vapor will strengthen ozone depletion through the chemical process. However, ozone will increase in the middle stratosphere. The change in ozone due to increasing water vapor has an important effect on the stratospheric temperature change.
基金Supported by National Natural Science Foundation of China (Grant No.50876080)
文摘The China Advanced Research Reactor (CARR) is scheduled to be operated in the autumn of 2008.In this paper,we report preparations for installing the neutron radiography instrument (NRI) and for utilizing it efficiently. The 2-D relative neutron intensity profiles for the water-vapor two-phase flow inside the robe were obtained using the MCNP code without influence of y-ray and electronic-noise.The MCNP simulation of the 2-D neutron intensity profile for the water-vapor two-phase flow was demonstrated.The simulated 2-D neutron intensity profiles could be used as the benchmark data base by calibrating part of the data measured by the CARR-NRI.The 3-D objective images allow us to understand the flow pattern more clearly and it is reconstructed using the MATLAB through the threshold transformation techniques.And thus it is concluded that the MCNP code and the MATLAB are very useful for constructing the benchmark data base for the investigation of the water-vapor two-phase flow using the CARR-NRI.
文摘2024/2025年前冬,即2024年12月1日—2025年1月15日,北半球季风区发生了1979年以来极为严重的干旱事件,其中中国东部地区尤为显著。此次事件对中国东部地区的经济发展和生态系统都造成了严重的影响。本文基于ERA5再分析资料,深入探究了此次中国东部极端干旱事件的成因及潜在物理机制。研究结果表明,造成此次极端干旱事件的直接原因是中国东部水汽异常辐散。从环流角度来看,北太平洋的异常气旋以及青藏高原南侧的异常反气旋导致中国东部主要受干冷的偏北风影响,进而引起中国东部和南方地区水汽辐散异常和降水偏少,诱发并维持了此次极端干旱事件。进一步研究表明,大气内部模态环北半球遥相关型可能是北太平洋气旋异常形成的主要原因,青藏高原前期秋季积雪异常偏少是青藏高原上空的深厚暖高压形成的原因,二者导致中国东部地区持续受异常偏北气流控制,进而引发局地降水减少。而2024/2025年前冬弱La Ni a型海温异常则通过调控Walker环流,引起南海上空异常气旋的形成,进一步抑制了中国东部地区的降水。在全球变暖背景下,更剧烈的水汽辐合、辐散可能会引发更严重的季风区极端降水或干旱事件,这为复杂气候背景下区域性干旱事件的预测提供了一定的理论依据。
文摘现有GNSS水汽层析研究主要聚焦于如何提升卫星观测数据利用率,但在卫星信号数据优选方面研究较少,导致穿过同一组网格集的层析观测方程线性近似且方程系数矩阵列向量元素多数为零,水汽层析模型病态严重。针对该现状,本文提出一种GNSS卫星信号自适应优选的水汽层析方法,解决层析模型设计矩阵零元素较多和层析模型病态的难题。该方法基于网格覆盖率最大原则确定层析区域水平网格划分,并发展联合卫星高度角与方位角阈值的卫星信号自适应优选方法,克服水汽层析模型观测方程线性近似的难题。本文选取香港地区2013年5月2日—2013年5月7日共6 d 12个GNSS测站及1个无线电探空站数据为例进行试验。与现有方法相比,本文方法能在降低卫星信号利用率的同时保证网格覆盖率,克服相似卫星信号造成层析模型设计矩阵病态的现状。以无线电探空数据为真值,发现本文方法反演水汽密度廓线的平均RMS、MAE和Bias分别为1.03、0.80和0.13 g/m^(3),优于传统方法的1.25、0.97和0.10 g/m^(3),其RMS改善率为20.78%;此外,本文方法在模型解算效率方面也优于传统方法,其模型计算效率平均提升9.51%。
基金the Ministry of Science and Technology of China under No.2004BA901A16the Natural Science Foundation of Gansu Province under No.3ZS051-A25-011
文摘Based on the remote sensing data, the radiosonde data and precipitation data observed by weather stations, distributions of atmospheric water-vapor and cloud motion wind over the Qilian Mountains are analyzed. Moreover, on the basis of water-vapor and cloud motion wind analyses, relations of atmospheric water-vapor distribution with precipitation~ atmospheric circulation, and terrain are investigated. The results show that distributions of atmospheric water-vapor and precipitation in the Qilian Mountains are affected by the westerly belt, the southerly monsoon （the South Asian monsoon and plateau monsoon）, and the East Asian monsoon. In the northwest Qilian Mountains, water-vapor and precipitation are entirely affected by the westerly belt, and there is no other direction water-vapor transport except westerly watervapor flux, hence, the northwest region is regarded as the westerly belt region. In the south and middle of the mountaili, water-vapor is mainly controlled by the southerly monsoon, 37.7% of the total watervapor is from the south, especially in summer, the southerly water-vapor flux accounts for 55.9% of the total, and furthermore the water-vapor content in the southerly flow is more than that in the westerly flow. The southerly monsoon water-vapor is influenced by the South Asian monsoon from the Indian Ocean and the plateau monsoon in the Qinghai-Tibetan Plateau, thus, the south and middle region is called southerly monsoon region. But in the northeast Qilian Mountains, the East Asian monsoon is the main climate system affecting the water-vapor. Besides west and northwest water-vapor fluxes, there are a lot of easterly water-vapor fluxes in summer. The frequency of easterly cloud motion winds in summer half year accounts for 27.1% of the total, though the frequency is not high, it is the main water-vapor source of summer precipitation in this region, therefore, the northwest region is a marginal region of the East Asian monsoon. On the other hand, atmospheric water-vapor, precipitation, and conversion rate of water-vapor into precipitation are closely related with altitudes and circulation system. Generally, there is a peak value of water-vapor content at the altitude from 3500 to 4500 m on the windward slope, but on the leeward slope, water-vapor monotonically decreases with altitude descending except for that in the East Asian monsoon region. Water-vapor on the leeward is much less than that on the windward slope~ and the maximal difference in water-vapor content between the two sides may reach about 4.49 kg m-2. Either the values of water-vapor content, precipitation or the conversion rate of water-vapor into precipitation all reach their maxima in the East Asian monsoon regions, and correspondingly the peak value of water-vapor on the windward is also large and occurs at a lower altitude in comparison with other two regions.
基金Project supported by the National Natural Science Foun-dation of China(Grant No.50679001)
文摘The supercavitation has attracted a growing interest because of its potential for high-speed vehicle maneuvering and drag reduction. To better understand the reverse flow characteristics of a water-vapor mixture in supercavitating flows around a hydrofoil, a numerical simulation is conducted using a unified supercavitation model, which combines a modified RNG k-~ turbulence model and a cavitation one. By comparing the related experimental results, the reverse motion of the water-vapor mixture is found in the cavitation area in all supercavitation stages. The inverse pressure gradient leads to reverse pressure fluctuations in the cavity, followed by the reverse motion of the water-vapor two-phase interface. Compared with the water-vapor mixture area at the back of the cavity, the pressure in the vapor area is inversely and slowly reduced, a higher-pressure gradient occurs near the cavity boundary.
