This study analyzes the variability of northern Eurasian snow cover（SC） in autumn and the impacts of atmospheric circulation changes. The region of large SC variability displays a southward shift from September to N...This study analyzes the variability of northern Eurasian snow cover（SC） in autumn and the impacts of atmospheric circulation changes. The region of large SC variability displays a southward shift from September to November, following the seasonal progression of the transition zones of surface air temperature（SAT）. The dominant pattern of SC variability in September and October features a zonal distribution, and that in November displays an obvious west-east contrast. Surface air cooling and snowfall increase are two factors for larger SC. The relative contribution of SAT and snowfall changes to SC, however, varies with the region and depends upon the season. The downward longwave radiation and atmospheric heat advection play important roles in SAT changes. Anomalous convergence of water vapor flux contributes to enhanced snowfall.The changes in downward longwave radiation are associated with those in atmospheric water content and column thickness.Changes in snowfall and the transport of atmospheric moisture determine the atmospheric moisture content in September and October, and the snowfall appears to be a main factor for atmospheric moisture change in November. These results indicate that atmospheric circulation changes play an important role in snow variability over northern Eurasia in autumn. Overall, the coupling between autumn Eurasian snow and atmospheric circulation may not be driven by external forcing.展开更多
This paper addresses the interannual variation of winter air temperature over Northeast China and its connection to preceding Eurasian snow cover. The results show that there is a significant negative correlation betw...This paper addresses the interannual variation of winter air temperature over Northeast China and its connection to preceding Eurasian snow cover. The results show that there is a significant negative correlation between October Eurasian snow cover and following-winter air temperature over Northeast China. The snow cover located in eastern Siberia and to the northeast of Lake Baikal plays an important role in the winter air temperature anomaly. More （less） eastern Siberia snow in October can cause an atmospheric circulation anomaly pattern in which the atmospheric pressure is higher （lower） than normal in the polar region and lower （higher） in the northern mid-high latitudes. Due to the persistence of the eastern Siberia snow from October to the following winter, the winter atmospheric anomaly is favorable （unfavorable） to the widespread movement of cold air masses from the polar region toward the northern mid-high latitudes and, hence, lower （higher） temperature over Northeast China. Simultaneously, when the October snow cover is more （less）, the SST in the northwestern Pacific is continuously lower （higher） as a whole; then, the Aleutian low and the East Asia trough are reinforced （weakened）, favoring the lower （higher） temperature over Northeast China.展开更多
This study shows a chemical and morphological characterization of snow samples collected near crossroads of urban area of Ferrara and near the Technological College of University of Ferrara (Italy) during three import...This study shows a chemical and morphological characterization of snow samples collected near crossroads of urban area of Ferrara and near the Technological College of University of Ferrara (Italy) during three important snowfalls. The field campaigns were carried out in the eastern part of Po Valley (Italy) in winter 2009-2010. The chemical composition of melted snow was compared with analyses of the same filtered samples of melted snow so as to give the composition of particles smaller than a few nm. The metal concentrations in the aerosol particles were analyzed with ICP-MS and IC methodologies, while the morphological features were described by SEM-EDS analyses. The results showed that snow samples were characterized by important amounts of allumo silicates with dimensions larger than 0.45 μm, from resuspension of the local soil, and IC analysis confirmed the anthropogenic pollution of the snow. Six main particles were classed and recognized: silica, carbonate, allumo silicate, sodium chloride and organic compounds, including biogenic materials and pollen (agricultural aerosols which are composed for 92% of single particles and for the remaining 8% of agglomerations of particles). We present here initial data on heavy metals in snow collected in Ferrara. They were obtained by analyzing fresh snow deposited during three snowfall events in December 2010, February and March 2011. The analyses were performed by the inductively coupled plasma mass spectrometry (ICP-MS), ion chromatography (IC) and scanning electron microscopy (SEM-EDS).展开更多
The Arctic sea ice minimum records appeared in the Septembers of 2007 and 2012, followed by high snow cover areas in the Northern Hemisphere winters. The snow cover distributions show different spatial patterns in the...The Arctic sea ice minimum records appeared in the Septembers of 2007 and 2012, followed by high snow cover areas in the Northern Hemisphere winters. The snow cover distributions show different spatial patterns in these two years: increased snow cover in Central Asia and Central North America in 2007, while increased snow cover in East Asia and northwestern Europe in 2012. The high snow cover anomaly shifted to higher latitudes in winter of 2012 compared to 2007. It is noticed that the snow cover had positive anomaly in 2007 and 2012 with the following conditions: the negative geopotential height and the related cyclonic wind anomaly were favorable for upwelling, and, with the above conditions, the low troposphere and surface air temperature anomaly and water vapor anomaly were favorable for the formation and maintenance of snowfalls. The negative geopotential height, cyclonic wind and low air temperature conditions were satisfied in different locations in 2007 and 2012, resulting in different spatial snow cover patterns. The cross section of lower air temperature move to higher latitudes in winter of 2012 compared to 2007.展开更多
Winter synoptic conditions that produce snowfall with bitterly cold temperatures create both social and economic hazards in the capital city of Albany, NY. Sometimes these systems are forecasted in error to produce ra...Winter synoptic conditions that produce snowfall with bitterly cold temperatures create both social and economic hazards in the capital city of Albany, NY. Sometimes these systems are forecasted in error to produce rain or mixed precipitation. It is beneficial for meteorologists to better understand the commonly used 5400 and 1300 GPM line to better forecast rain versus snow events. Other studies have looked into the use of the 5400 GPM (540 dm) line but none have assessed the validity of this boundary with respect to weather type characterization at Albany. This study aims to determine the reliability of the widely referenced guides for depicting the rain-snow line, and improve forecast aids for the vertical atmosphere during winter precipitation events. The mean daily 500, 850, 925 and 1000 mb heights and weather type frequency of the Spatial Synoptic Classification between November and March of 1980 - 2012 are analyzed. Results indicate that the standard vertical boundaries are inaccurate indicators of a rain versus snow event in Albany. More reasonable rain-snow cut offs for the 1000 - 500 and 1000 - 850 mb thicknesses are 5222 and 1262 GPM. For the 1000 - 925 mb level, 606 GPM is a helpful aid of identifying the rain-snow boundary. Further scrutinizing by weather type indicates that the rain-snow boundary also varies depending on what air mass/weather type is present on a given day. For instance, when the most prominent weather type is observed over Albany (Dry Polar), at the 1000 - 850 mb and 1000 - 500 mb layers, a boundary of 1242 GPM and 5152 GPM is found to be most representative. Results indicate only for the rarest of winter weather types observed over Albany, Moist Tropical, are the standard cut offs useful. Determining the reliability of this precipitation indicator at a specific station, like Albany, could enable meteorologists in other regions of the country to draw parallels between weather type, precipitation, and thickness in their forecast zones.展开更多
基金Reported investigations were partially supported by the Russian Foundation for Basic researches project No. 15-58-53013 FФEH a and the National Natural Science Foundation of China under contracts No. 51279122 and No. 51511130042.
基金supported by the National Postdoctoral Scientific Foundation(20080440342)the opening fund from the State Key Laboratory of Cryospheric Sciences,Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences(SKLCS 08-07)
基金supported by the National Key Basic Research Program of China (Grant No. 2014CB953902)the National Natural Science Foundation of China (Grant Nos. 41530425, 41275081 and 41475081)
文摘This study analyzes the variability of northern Eurasian snow cover（SC） in autumn and the impacts of atmospheric circulation changes. The region of large SC variability displays a southward shift from September to November, following the seasonal progression of the transition zones of surface air temperature（SAT）. The dominant pattern of SC variability in September and October features a zonal distribution, and that in November displays an obvious west-east contrast. Surface air cooling and snowfall increase are two factors for larger SC. The relative contribution of SAT and snowfall changes to SC, however, varies with the region and depends upon the season. The downward longwave radiation and atmospheric heat advection play important roles in SAT changes. Anomalous convergence of water vapor flux contributes to enhanced snowfall.The changes in downward longwave radiation are associated with those in atmospheric water content and column thickness.Changes in snowfall and the transport of atmospheric moisture determine the atmospheric moisture content in September and October, and the snowfall appears to be a main factor for atmospheric moisture change in November. These results indicate that atmospheric circulation changes play an important role in snow variability over northern Eurasia in autumn. Overall, the coupling between autumn Eurasian snow and atmospheric circulation may not be driven by external forcing.
基金supported by the National Natural Science Foundation of China(Grant Nos.41130103 and 41210007)the National Basic Research Program of China(Grant No.2009CB421406)the CAS–CSIRO Cooperative Research Program(Grant No.GJHZ1223)
文摘This paper addresses the interannual variation of winter air temperature over Northeast China and its connection to preceding Eurasian snow cover. The results show that there is a significant negative correlation between October Eurasian snow cover and following-winter air temperature over Northeast China. The snow cover located in eastern Siberia and to the northeast of Lake Baikal plays an important role in the winter air temperature anomaly. More （less） eastern Siberia snow in October can cause an atmospheric circulation anomaly pattern in which the atmospheric pressure is higher （lower） than normal in the polar region and lower （higher） in the northern mid-high latitudes. Due to the persistence of the eastern Siberia snow from October to the following winter, the winter atmospheric anomaly is favorable （unfavorable） to the widespread movement of cold air masses from the polar region toward the northern mid-high latitudes and, hence, lower （higher） temperature over Northeast China. Simultaneously, when the October snow cover is more （less）, the SST in the northwestern Pacific is continuously lower （higher） as a whole; then, the Aleutian low and the East Asia trough are reinforced （weakened）, favoring the lower （higher） temperature over Northeast China.
基金supported by the Fund of Polar Scientific Research(No.20080216) of State Ocean Administration, Chinaby Chinese Natural Science Foundation(No. 20407001,No.40701170)
文摘This study shows a chemical and morphological characterization of snow samples collected near crossroads of urban area of Ferrara and near the Technological College of University of Ferrara (Italy) during three important snowfalls. The field campaigns were carried out in the eastern part of Po Valley (Italy) in winter 2009-2010. The chemical composition of melted snow was compared with analyses of the same filtered samples of melted snow so as to give the composition of particles smaller than a few nm. The metal concentrations in the aerosol particles were analyzed with ICP-MS and IC methodologies, while the morphological features were described by SEM-EDS analyses. The results showed that snow samples were characterized by important amounts of allumo silicates with dimensions larger than 0.45 μm, from resuspension of the local soil, and IC analysis confirmed the anthropogenic pollution of the snow. Six main particles were classed and recognized: silica, carbonate, allumo silicate, sodium chloride and organic compounds, including biogenic materials and pollen (agricultural aerosols which are composed for 92% of single particles and for the remaining 8% of agglomerations of particles). We present here initial data on heavy metals in snow collected in Ferrara. They were obtained by analyzing fresh snow deposited during three snowfall events in December 2010, February and March 2011. The analyses were performed by the inductively coupled plasma mass spectrometry (ICP-MS), ion chromatography (IC) and scanning electron microscopy (SEM-EDS).
基金supported by the Project of Comprehensive Evaluation of Polar Areas on Global and Regional Climate Changes (CHINARE2015-04-04)the National Natural Science Foundation of China (Grant No. 41406027)+1 种基金the NSFC-Shandong Joint Fund for Marine Science Research Centers (Grant No. U1406404)the international cooperation project of Indo-Pacific ocean environment variation and air-sea interaction (Grant No. GASI-03-IPOVAI-05)
文摘The Arctic sea ice minimum records appeared in the Septembers of 2007 and 2012, followed by high snow cover areas in the Northern Hemisphere winters. The snow cover distributions show different spatial patterns in these two years: increased snow cover in Central Asia and Central North America in 2007, while increased snow cover in East Asia and northwestern Europe in 2012. The high snow cover anomaly shifted to higher latitudes in winter of 2012 compared to 2007. It is noticed that the snow cover had positive anomaly in 2007 and 2012 with the following conditions: the negative geopotential height and the related cyclonic wind anomaly were favorable for upwelling, and, with the above conditions, the low troposphere and surface air temperature anomaly and water vapor anomaly were favorable for the formation and maintenance of snowfalls. The negative geopotential height, cyclonic wind and low air temperature conditions were satisfied in different locations in 2007 and 2012, resulting in different spatial snow cover patterns. The cross section of lower air temperature move to higher latitudes in winter of 2012 compared to 2007.
文摘Winter synoptic conditions that produce snowfall with bitterly cold temperatures create both social and economic hazards in the capital city of Albany, NY. Sometimes these systems are forecasted in error to produce rain or mixed precipitation. It is beneficial for meteorologists to better understand the commonly used 5400 and 1300 GPM line to better forecast rain versus snow events. Other studies have looked into the use of the 5400 GPM (540 dm) line but none have assessed the validity of this boundary with respect to weather type characterization at Albany. This study aims to determine the reliability of the widely referenced guides for depicting the rain-snow line, and improve forecast aids for the vertical atmosphere during winter precipitation events. The mean daily 500, 850, 925 and 1000 mb heights and weather type frequency of the Spatial Synoptic Classification between November and March of 1980 - 2012 are analyzed. Results indicate that the standard vertical boundaries are inaccurate indicators of a rain versus snow event in Albany. More reasonable rain-snow cut offs for the 1000 - 500 and 1000 - 850 mb thicknesses are 5222 and 1262 GPM. For the 1000 - 925 mb level, 606 GPM is a helpful aid of identifying the rain-snow boundary. Further scrutinizing by weather type indicates that the rain-snow boundary also varies depending on what air mass/weather type is present on a given day. For instance, when the most prominent weather type is observed over Albany (Dry Polar), at the 1000 - 850 mb and 1000 - 500 mb layers, a boundary of 1242 GPM and 5152 GPM is found to be most representative. Results indicate only for the rarest of winter weather types observed over Albany, Moist Tropical, are the standard cut offs useful. Determining the reliability of this precipitation indicator at a specific station, like Albany, could enable meteorologists in other regions of the country to draw parallels between weather type, precipitation, and thickness in their forecast zones.
