A series of measurements of ice-nucleating particles （1NPs） were performed at two sites in Beijing. At the Beijing Meteorological Service （BMS） site, which was an urban site, no INPs were found to be active above ...A series of measurements of ice-nucleating particles （1NPs） were performed at two sites in Beijing. At the Beijing Meteorological Service （BMS） site, which was an urban site, no INPs were found to be active above -15℃. However, at the Yanjiaping （YJP） site, which was a rural site, the concentration of 1NPs active at temperatures above -15℃ was found to be as high as 1.73 g^-1. Two parameterizations were constructed by respectively fitting the data obtained at BMS site and YJP site. The two parameterizations, as well as another parameterization from the literature, were implemented into a parcel model to investigate the effect of INPs active above -15℃ on phase partitioning in mixed-phase clouds. At a vertical velocity of 0.01 m s^-1 , which is typical for stratiform clouds associated with frontal systems, the INPs active above -15℃ nucleate ice crystals at low levels. The growth of these ice crystals remarkably reduces both the maximum liquid water mixing ratio and the altitude where the maximum liquid water mixing ratio is reached. When the vertical velocity of the parcel is increased to 0.1 m s^-l or an even higher value, the evolution of li-quid water mixing, ratio is not controlled by the INPs active above 15℃ but those active below -15℃.展开更多
Ice-nucleating proteins(INPs)are the most effective ice-nucleating agents that play a significant role in preventing freeze injuries in freeze-tolerant organisms.INPs promote ice nucleation in the extracellular space,...Ice-nucleating proteins(INPs)are the most effective ice-nucleating agents that play a significant role in preventing freeze injuries in freeze-tolerant organisms.INPs promote ice nucleation in the extracellular space,harvesting water from cells due to the low vapor pressure of ice compared with water,thereby protecting freeze-tolerant organisms from intracellular freezing.The antifreeze mechanism of INPs offers a unique opportunity to inhibit large-scale freezing by localized control of ice formation,with valuable enlightenment in anti-icing material sciences.By learning from nature,we transferred the excellent ice nucleation-facilitating capability of INPs along with an antifreeze concept of spatially controlled ice nucleation to anti-icing material design,fabricating icephobic coatings that consisted of patterned hydrogel-encapsulated INP(PHINP).The ice patterns were templated by patterned PHINPs via the tuning of ice nucleation so that the ice coverage fraction could be controlled by<30%on almost all PHINP-coated surfaces.Combining PHINP with solar-thermal conversion surfaces endowed the composite coatings with high anti-icing performances at any time of the day.展开更多
Cirrus clouds related to transported dust layers were identified on 22 occasions with ground-based polarization lidar from December 2012 to February 2018 over Wuhan(30.5°N,114.4°E),China.All the events occur...Cirrus clouds related to transported dust layers were identified on 22 occasions with ground-based polarization lidar from December 2012 to February 2018 over Wuhan(30.5°N,114.4°E),China.All the events occurred in spring and winter.Cirrus clouds were mostly located above 7.6 km on top of the aloft dust layers.In-cloud relative humidity with respect to ice(RH_(i))derived from water vapor Raman lidar as well as from ERA5 reanalysis data were used as criteria to determine the possible ice nucleation regimes.Corresponding to the two typical cases shown,the observed events can be classified into two categories:(1)category A(3 cases),in-cloud peak RH_(i)≥150%,indicating competition between heterogeneous nucleation and homogeneous nucleation;and(2)category B(19 cases),in-cloud peak RH_(i)<150%,revealing that only heterogeneous nucleation was involved.Heterogeneous nucleation generally took place during instances of cirrus cloud formation in the upper troposphere when advected dust particles were present.Although accompanying cloud-top temperatures ranged from–51.9℃to–30.4℃,dust-related heterogeneous nucleation contributed to primary ice nucleation in cirrus clouds by providing ice nucleating particle concentrations on the order of 10^(−3)L^(−1)to 10^(2)L^(−1).Heterogeneous nucleation and subsequent crystal growth reduced the ambient RH_(i)to be less than 150%by consuming water vapor and thus completely inhibited homogeneous nucleation.展开更多
Theory and evidence indicate that trees and other vegetation influence the atmospheric water-cycle in various ways.These influences are more important, more complex, and more poorly characterised than is widely realis...Theory and evidence indicate that trees and other vegetation influence the atmospheric water-cycle in various ways.These influences are more important, more complex, and more poorly characterised than is widely realised.While there is little doubt that changes in tree cover will impact the water-cycle, the wider consequences remain difficult to predict as the underlying relationships and processes remain poorly characterised. Nonetheless, as forests are vulnerable to human activities, these linked aspects of the water-cycle are also at risk and the potential consequences of large scale forest loss are severe. Here, for non-specialist readers, I review our knowledge of the links between vegetation-cover and climate with a focus on forests and rain(precipitation). I highlight advances, uncertainties and research opportunities. There are significant shortcomings in our understanding of the atmospheric hydrological cycle and of its representation in climate models. A better understanding of the role of vegetation and tree-cover wil reduce some of these shortcomings. I outline and il ustrate various research themes where these advances may be found.These themes include the biology of evaporation, aerosols and atmospheric motion, as well as the processes that determine monsoons and diurnal precipitation cycles. A novel theory—the ‘biotic pump’—suggests that evaporation and condensation can exert a major influence over atmospheric dynamics. This theory explains how high rainfall can be maintained within those continental land-masses that are sufficiently forested. Feedbacks within many of these processes can result in non-linear behaviours and the potential for dramatic changes as a result of forest loss(or gain): for example, switching from a wet to a dry local climate(or visa-versa). Much remains unknown and multiple research disciplines are needed to address this: forest scientists and other biologists have a major role to play.New ideas, methods and data offer opportunities to improve understanding. Expect surprises.展开更多
基金Supported by the National Natural Science Foundation of China(41775138 and 41330421)Natural Science Foundation of Beijing(8172023)+1 种基金Beijing Municipal Science and Technology Commission(D171100000717001)Science and Technology Project of Beijing Meteorological Service(BMBKJ201701007)
文摘A series of measurements of ice-nucleating particles （1NPs） were performed at two sites in Beijing. At the Beijing Meteorological Service （BMS） site, which was an urban site, no INPs were found to be active above -15℃. However, at the Yanjiaping （YJP） site, which was a rural site, the concentration of 1NPs active at temperatures above -15℃ was found to be as high as 1.73 g^-1. Two parameterizations were constructed by respectively fitting the data obtained at BMS site and YJP site. The two parameterizations, as well as another parameterization from the literature, were implemented into a parcel model to investigate the effect of INPs active above -15℃ on phase partitioning in mixed-phase clouds. At a vertical velocity of 0.01 m s^-1 , which is typical for stratiform clouds associated with frontal systems, the INPs active above -15℃ nucleate ice crystals at low levels. The growth of these ice crystals remarkably reduces both the maximum liquid water mixing ratio and the altitude where the maximum liquid water mixing ratio is reached. When the vertical velocity of the parcel is increased to 0.1 m s^-l or an even higher value, the evolution of li-quid water mixing, ratio is not controlled by the INPs active above 15℃ but those active below -15℃.
基金The authors gratefully acknowledge the financial support from The National Key Research and Development Program of China(grant no.2020YFE0100300)Chinese National Nature Science Foundation(grant nos.51925307,21733010,21875261,and 21805286)+2 种基金National Key R&D Program of China(grant no.2018YFA0208502)Key Research Program of Frontier Sciences,CAS(grant no.ZDBS-LYSLH031)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(grant no.2018044).
文摘Ice-nucleating proteins(INPs)are the most effective ice-nucleating agents that play a significant role in preventing freeze injuries in freeze-tolerant organisms.INPs promote ice nucleation in the extracellular space,harvesting water from cells due to the low vapor pressure of ice compared with water,thereby protecting freeze-tolerant organisms from intracellular freezing.The antifreeze mechanism of INPs offers a unique opportunity to inhibit large-scale freezing by localized control of ice formation,with valuable enlightenment in anti-icing material sciences.By learning from nature,we transferred the excellent ice nucleation-facilitating capability of INPs along with an antifreeze concept of spatially controlled ice nucleation to anti-icing material design,fabricating icephobic coatings that consisted of patterned hydrogel-encapsulated INP(PHINP).The ice patterns were templated by patterned PHINPs via the tuning of ice nucleation so that the ice coverage fraction could be controlled by<30%on almost all PHINP-coated surfaces.Combining PHINP with solar-thermal conversion surfaces endowed the composite coatings with high anti-icing performances at any time of the day.
基金funded by the National Natural Science Foundation of China (Grant Nos. 42005101 and 41927804)Hubei Provincial Natural Science Foundation of China (Grant No. 2020CFB229)+1 种基金the Fundamental Research Funds for the Central Universities Grant (Grant Nos. 2042020kf0018 and 2042021kf1066)The Meridian Space Weather Monitoring Project (China) also provides financial support for lidar maintenance
文摘Cirrus clouds related to transported dust layers were identified on 22 occasions with ground-based polarization lidar from December 2012 to February 2018 over Wuhan(30.5°N,114.4°E),China.All the events occurred in spring and winter.Cirrus clouds were mostly located above 7.6 km on top of the aloft dust layers.In-cloud relative humidity with respect to ice(RH_(i))derived from water vapor Raman lidar as well as from ERA5 reanalysis data were used as criteria to determine the possible ice nucleation regimes.Corresponding to the two typical cases shown,the observed events can be classified into two categories:(1)category A(3 cases),in-cloud peak RH_(i)≥150%,indicating competition between heterogeneous nucleation and homogeneous nucleation;and(2)category B(19 cases),in-cloud peak RH_(i)<150%,revealing that only heterogeneous nucleation was involved.Heterogeneous nucleation generally took place during instances of cirrus cloud formation in the upper troposphere when advected dust particles were present.Although accompanying cloud-top temperatures ranged from–51.9℃to–30.4℃,dust-related heterogeneous nucleation contributed to primary ice nucleation in cirrus clouds by providing ice nucleating particle concentrations on the order of 10^(−3)L^(−1)to 10^(2)L^(−1).Heterogeneous nucleation and subsequent crystal growth reduced the ambient RH_(i)to be less than 150%by consuming water vapor and thus completely inhibited homogeneous nucleation.
基金the value of participation in the Australian Research Council projects under grants DP160102107 and LP130100498benefitted from the meeting in Leuven,Belgium in 2015 where his participation was funded by We Forest and the Center for International Forest Researchfrom the meeting in Wageningen,Netherlands,also in 2015,where his participation was funded by Tropenbos
文摘Theory and evidence indicate that trees and other vegetation influence the atmospheric water-cycle in various ways.These influences are more important, more complex, and more poorly characterised than is widely realised.While there is little doubt that changes in tree cover will impact the water-cycle, the wider consequences remain difficult to predict as the underlying relationships and processes remain poorly characterised. Nonetheless, as forests are vulnerable to human activities, these linked aspects of the water-cycle are also at risk and the potential consequences of large scale forest loss are severe. Here, for non-specialist readers, I review our knowledge of the links between vegetation-cover and climate with a focus on forests and rain(precipitation). I highlight advances, uncertainties and research opportunities. There are significant shortcomings in our understanding of the atmospheric hydrological cycle and of its representation in climate models. A better understanding of the role of vegetation and tree-cover wil reduce some of these shortcomings. I outline and il ustrate various research themes where these advances may be found.These themes include the biology of evaporation, aerosols and atmospheric motion, as well as the processes that determine monsoons and diurnal precipitation cycles. A novel theory—the ‘biotic pump’—suggests that evaporation and condensation can exert a major influence over atmospheric dynamics. This theory explains how high rainfall can be maintained within those continental land-masses that are sufficiently forested. Feedbacks within many of these processes can result in non-linear behaviours and the potential for dramatic changes as a result of forest loss(or gain): for example, switching from a wet to a dry local climate(or visa-versa). Much remains unknown and multiple research disciplines are needed to address this: forest scientists and other biologists have a major role to play.New ideas, methods and data offer opportunities to improve understanding. Expect surprises.
