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19篇 您的检索式:作者名="Timo VIHMA"
    题名 作者 年代 出处 被引量
1Extreme Cold Events from East Asia to North America in Winter 2020/21:Comparisons,Causes,and Future Implications显示文摘Three striking and impactful extreme cold weather events successively occurred across East Asia and North America during the mid-winter of 2020/21.These events open a new window to detect possible underlying physical processes.The analysis here indicates that the occurrences of the three events resulted from integrated effects of a concurrence of anomalous thermal conditions in three oceans and interactive Arctic-lower latitude atmospheric circulation processes,which were linked and influenced by one major sudden stratospheric warming(SSW).The North Atlantic warm blob initiated an increased poleward transient eddy heat flux,reducing the Barents-Kara seas sea ice over a warmed ocean and disrupting the stratospheric polar vortex(SPV)to induce the major SSW.The Rossby wave trains excited by the North Atlantic warm blob and the tropical Pacific La Nina interacted with the Arctic tropospheric circulation anomalies or the tropospheric polar vortex to provide dynamic settings,steering cold polar air outbreaks.The long memory of the retreated sea ice with the underlying warm ocean and the amplified tropospheric blocking highs from the midlatitudes to the Arctic intermittently fueled the increased transient eddy heat flux to sustain the SSW over a long time period.The displaced or split SPV centers associated with the SSW played crucial roles in substantially intensifying the tropospheric circulation anomalies and moving the jet stream to the far south to cause cold air outbreaks to a rarely observed extreme state.The results have significant implications for increasing prediction skill and improving policy decision making to enhance resilience in“One Health,One Future”.Xiangdong ZHANG Yunfei FU Zhe HAN James E.OVERLAND Annette RINKE Han TANG Timo VIHMA Muyin WANG 2022Advances in Atmospheric Sciences2022,39,4:7
2基于温度链浮标获取南极普里兹湾积雪和固定冰厚度的研究显示文摘极地积雪和海冰厚度是气候变化的重要指标,也是船舶在冰区航行需要掌握的主要参数。2014和2015年在南极普里兹湾中山站附近布放了一种新式的温度链浮标,该浮标每天进行4次常规温度观测和1次加热升温观测,用于实时获取积雪和海冰剖面温度及厚度数据的研究。通过分析剖面温度曲线和升温曲线反映出的大气、积雪、海冰和海水4种介质的热传导特性差异,可利用人工识别的方法(人工经验法)获得大气/积雪、积雪/海冰和海冰/海水界面的位置。根据统计不同介质在升温响应和垂直温度梯度等方面的特性,找到合理阈值,可通过编写程序自动判断各界面的位置(自动程序法)。本文利用这两种方法来判断不同物质界面位置从而计算得到积雪和海冰厚度。与现场人工观测的海冰厚度相比,人工经验法的平均偏差和均方根偏差分别为2.1cm和6.4cm(2014年)以及4.3cm和6.5cm(2015年),自动程序法的平均偏差和均方根偏差分别为-6.8cm和6.4cm(2014年)以及4.5cm和6.6cm(2015年);对于积雪,人工经验法与现场人工观测的平均偏差和均方根偏差分别为0.5cm和8.5cm,而自动程序法的平均偏差和均方根偏差分别为4.7cm和10.8cm。自动程序法误差较人工经验法偏大,但考虑到整体冰厚和现场观测的误差,两种方法的结果均是可信的,精度是可以接受的。利用新式的温度链浮标实时获取南极普里兹湾积雪和海冰厚度是可行的。赵杰臣 杨清华 程斌 汪宁 惠凤鸣 沈辉 韩晓鹏 张林 Timo Vihma 2017海洋学报2017,39,11:7
3Snow and sea ice thermodynamics in the Arctic:Model validation and sensitivity study against SHEBA data显示文摘Evolution of the Arctic sea ice and its snow cover during the SHEBA year were simulated by applying a high-resolution thermodynamic snow/ice model (HIGHTSI).Attention was paid to the impact of albedo on snow and sea ice mass balance,effect of snow on total ice mass balance,and the model vertical resolution. The SHEBA annual simulation was made applying the best possible external forcing data set created by the Sea Ice Model Intercomparison Project.The HIGHTSI control run reasonably reproduced the observed snow and ice thickness.A number of albedo schemes were incorporated into HIGHTSI to study the feedback processes between the albedo and snow and ice thickness.The snow thickness turned out to be an essential variable in the albedo parameterization.Albedo schemes dependent on the surface temperature were liable to excessive positive feedback effects generated by errors in the modelled surface temperature.The superimposed ice formation should be taken into account for the annual Arctic sea ice mass balance.Cheng Bin Timo Vihma Zhang Zhanhai Li Zhijun Wu Huiding 2008Chinese Journal of Polar Science2008,19,2:5
4Observation and modelling of snow and sea ice mass balance and its sensitivity to atmospheric forcing during spring and summer 2007 in the Central Arctic显示文摘Snow depth and sea ice thickness were observed applying an ice mass balance buoy(IMB)in the drifting ice station Tara during the International Polar Year in 2007.Detailed in situ observations on meteorological variables and surface fluxes were taken during May to August.For this study,the operational analyses and short-term forecasts from two numerical weather prediction(NWP)models(ECMWF and HIRLAM)were extracted for the Tara drift trajectory.We compared the IMB,meteorological and surface flux observations against the NWP products,also applying a one-dimensional thermodynamic sea ice model(HIGHTSI)to calculate the snow and ice mass balance and its sensitivity to atmospheric forcing.The modelled snow depth time series,controlled by NWP-based precipitation,was in line with the observed one.HIGHTSI reproduced well the snowmelt onset,the progress of the melt,and the first date of snow-free conditions.HIGHTSI performed well also in the late August freezing season.Challenges remain to model the“false bottom”observed during the melting season.The evolution of the vertical temperature profiles in snow and ice was better simulated when the model was forced by in situ observations instead of NWP results.During the melting period,the nonlinear ice temperature profile was successfully modelled with both forcing options.During spring and the melting season,total sea ice mass balance was most sensitive to uncertainties in NWP results for the downward longwave radiation,followed by the downward shortwave radiation,air temperature,and wind speed.Bin CHENG Timo VIHMA Timo PALO Marcel NICOLAUS Sebastian GERLAND Laura RONTU Jari HAAPALA Donald PEROVICH 2021Advances in Polar Science2021,32,4:4
5Observed and modelled snow and ice thickness in the Arctic Ocean with CHINARE buoy data显示文摘Sea ice and the snow pack on top of it were investigated using Chinese National Arctic Research Expedition(CHINARE) buoy data.Two polar hydrometeorological drifters,known as Zeno? ice stations,were deployed during CHINARE 2003.A new type of high-resolution Snow and Ice Mass Balance Arrays,known as SIMBA buoys,were deployed during CHINARE 2014.Data from those buoys were applied to investigate the thickness of sea ice and snow in the CHINARE domain.A simple approach was applied to estimate the average snow thickness on the basis of Zeno~ temperature data.Snow and ice thicknesses were also derived from vertical temperature profile data based on the SIMBA buoys.A one-dimensional snow and ice thermodynamic model(HIGHTSI) was applied to calculate the snow and ice thickness along the buoy drift trajectories.The model forcing was based on forecasts and analyses of the European Centre for Medium-Range Weather Forecasts(ECMWF).The Zeno~ buoys drifted in a confined area during 2003–2004.The snow thickness modelled applying HIGHTSI was consistent with results based on Zeno~ buoy data.The SIMBA buoys drifted from 81.1°N,157.4°W to 73.5°N,134.9°W in 15 months during2014–2015.The total ice thickness increased from an initial August 2014 value of 1.97 m to a maximum value of2.45 m before the onset of snow melt in May 2015;the last observation was approximately 1 m in late November2015.The ice thickness based on HIGHTSI agreed with SIMBA measurements,in particular when the seasonal variation of oceanic heat flux was taken into account,but the modelled snow thickness differed from the observed one.Sea ice thickness derived from SIMBA data was reasonably good in cold conditions,but challenges remain in both snow and ice thickness in summer.TIAN Zhongxiang CHENG Bin ZHAO liechen VIHMA Timo ZHANG Wenliang LI Zhijun ZHANG Zhanhai 2017Acta Oceanologica Sinica2017,36,8:3
6Links between Arctic sea ice and extreme summer precipitation in China:an alternative view显示文摘Potential links between the Arctic sea-ice concentration anomalies and extreme precipitation in China are explored. Associations behind these links can be explained by physical interpretations aided by visualisations of temporarily lagged composites of variables such as atmospheric mean sea level pressure and sea surface temperature. This relatively simple approach is verified by collectively examining already known links between the Arctic sea ice and rainfall in China. For example, similarities in the extreme summer rainfall response to Arctic sea-ice concentration anomalies either in winter(DJF) or in spring(MAM) are highlighted. Furthermore, new links between the Arctic sea ice and the extreme weather in India and Eurasia are proposed. The methodology developed in this study can be further applied to identify other remote impacts of the Arctic sea ice variability.Petteri Uotila Alexey Karpechko Timo Vihma 2014Advances in Polar Science2014,25,4:2
7Foreword显示文摘Rapid changes of Arctic sea ice cover have been in the focus of the international climate research community in recent years.Quite a few of nations have completed a large number of related surveys and research projects in the Arctic Ocean.Up to now,China has performed six research cruises to the Arctic Ocean resulting in a significant volume of research output.Improved knowledge on the atmospheree-sea ice-ocean interactions in the Arctic isMatti Lepparanta Timo Vihma Huiding Wu 2014Advances in Polar Science2014,25,4:1
8Modeling of superimposed ice formation during the spring snowmeh period in the Baltic Sea显示文摘Cheng B Timo VIHMA Roberta PIRAZZINI 2006Annals of Glaciology2006,44,:1
9Effects of Arctic Sea Ice Decline on Weather and Climate: A Review显示文摘Timo Vihma 2014Surveys in Geophysics2014,,5:1
10Effect of weather on the performance of mara- thon runners显示文摘TIMO VIHMA 2010Int J Biometeorol2010,54,:1
11‘Observations and Modelling of Cold-air Advection over Arctic Sea Ice’显示文摘Timo Vihma Christof Lüpkes J?rg Hartmann Hannu Savij?rvi 2005Boundary - Layer Meteorology2005,,2:1
12Impact of Assimilation of Radiosonde and UAV Observations from the Southern Ocean in the Polar WRF Model显示文摘Weather forecasting in the Southern Ocean and Antarctica is a challenge above all due to the rarity of observations to be assimilated in numerical weather prediction(NWP)models.As observations are expensive and logistically challenging,it is important to evaluate the benefit that additional observations could bring to NWP.Atmospheric soundings applying unmanned aerial vehicles(UAVs)have a large potential to supplement conventional radiosonde sounding observations.Here,we applied UAV and radiosonde sounding observations from an RV Polarstern cruise in the ice-covered Weddell Sea in austral winter 2013 to evaluate the impact of their assimilation in the Polar version of the Weather Research and Forecasting(Polar WRF)model.Our experiments revealed small to moderate impacts of radiosonde and UAV data assimilation.In any case,the assimilation of sounding data from both radiosondes and UAVs improved the analyses of air temperature,wind speed,and humidity at the observation site for most of the time.Further,the impact on the results of 5-day-long Polar WRF experiments was often felt over distances of at least 300 km from the observation site.All experiments succeeded in capturing the main features of the evolution of near-surface variables,but the effects of data assimilation varied between different cases.Due to the limited vertical extent of the UAV observations,the impact of their assimilation was limited to the lowermost 1?2-km layer,and assimilation of radiosonde data was more beneficial for modeled sea level pressure and near-surface wind speed.Qizhen SUN Timo VIHMA Marius OJONASSEN Zhanhai ZHANG 2020Advances in Atmospheric Sciences2020,37,5:1
13An overview of Antarctic polynyas: sea ice production, forcing mechanisms, temporal variability and water mass formation显示文摘Polynyas are irregular open water bodies within the sea ice cover in polar regions under freezing weather conditions.In this study,we reviewed the progress of research work on dynamical forcing,sea ice production(SIP),and water mass formation for both coastal polynyas and open-ocean polynyas in the Southern Ocean,as well as the variability and controlling mechanisms of polynya processes on different time scales.Polynyas play an irreplaceable role in the regulation of global ocean circulation and biological processes in regional ocean ecosystems.The coastal polynyas(latent heat polynyas)are mainly located in the Weddell Sea,the Ross Sea and on the west side of protruding topographic features in East Antarctica.During the formation of coastal polynyas,which are mainly forced by offshore winds or ocean currents,brine rejection triggered by high SIP results in the formation of high salinity shelf water,which is the predecessor of the Antarctic bottom water-the lower limb of the global thermohaline circulation.The open-ocean polynyas(sensible heat polynyas)are mainly found in the Indian sector of the Southern Ocean,which are formed by ocean convection processes generated by topography and negative wind stress curl.The convection processes bring nutrients into the upper ocean,which supports biological production and makes the polynya regions an important sink for atmospheric carbon dioxide.The limitations and challenges in polynya research are also discussed.WEI Zheng ZHANG Zhaoru Timo VIHMA WANG Xiaoqiao CHEN Yuanjie 2021Advances in Polar Science2021,32,4:1
14Effect of weather on the performance of mara- thon runners显示文摘Timo Vihma 2010Int J Biometeorol2010,54,:1
15An outstanding example of cooperation between Arctic and non-Arctic countries in cryosphere and climate research: Sino-Finnish cooperation for more than 30 years显示文摘The cryosphere is interconnected with other components of the climate system through global exchange of water,energy,and carbon.Long-term sustainable and pragmatic scientific and technological cooperation on the cryosphere and climatology in polar and sub-polar regions between China and Finland began in the 1980s.The fields of bilateral cooperation include joint training of young scientists,joint field observations,climatological and ecological researches of polar and sub-polar sea ice,glaciers and frozen lakes,etc.The year 2020 marked the 70th anniversary of the establishment of diplomatic relations between China and Finland.In order to celebrate the great achievements by Chinese and Finnish scientists in the fieldsof cryosphere and climate research,the Advances in Polar Science invited scientists from both sides to jointly organize a Special Issue entitled“Sino-Finnish cooperation on cryosphere and climatology in polar and sub-polar regions”.In this Special Issue,we have collected 10 papers,with most papers created jointly by scientists of both sides.The fruitful scientific achievement is strongly benefited from the sustainability of cooperation.Monitoring,research,prediction,mitigation,and adaptation to the climate change in the polar and sub-polar regions will definitively stay in the focus for many decades to come.A new era of Finnish-Chinese scientific collaboration on cryosphere has begun.Matti LEPPÄRANTA Timo VIHMA Bin CHENG LEI Ruibo 2021Advances in Polar Science2021,32,4:0
16On the turbulent heat fluxes:A comparison among satellite-based estimates,atmospheric reanalyses,and in-situ observations during the winter climate over Arctic sea ice显示文摘The surface energy budget is crucial for Arctic sea ice mass balance calculation and climate systems,among which turbulent heat fluxes significantly affect the airesea exchanges of heat and moisture in the atmospheric boundary layer.Satellite observations(e.g.CERES and APPX)and atmospheric reanalyses(e.g.,ERA5)are often used to represent components of the energy budget at regional and pan-Arctic scales.However,the uncertainties of the satellite-based turbulent heat fluxes are largely unknown,and cross-comparisons with reanalysis data and insitu observations are limited.In this study,satellite-based turbulent heat fluxes were assessed against in-situ observations from the N-ICE2015 drifting ice station(north of Svalbard,JanuaryeJune 2015)and ERA5 reanalysis.The turbulent heat fluxes were calculated by two approaches using the satellite-based ice surface temperature and radiative fluxes,surface atmospheric parameters from ERA5,and snow/sea ice thickness from the pan-Arctic Ice Ocean Modeling and Assimilation System(PIOMAS).We found that the bulk-aerodynamic formula based results could better capture the variations of turbulent heat fluxes,while the maximum entropy production based estimates are comparable with ERA5 in terms of root-mean-square error(RMSE).CERES-based estimates outperform the APP-X-based ones but ERA5 performs the best in all seasons(RMSE of 18 and 7 W m^(-2)for sensible and latent heat flux,respectively).The aireice temperature/humidity differences and the surface radiation budget were found the primary driving factors in the bulk-formula method and maximum entropy production(MEP)method,respectively.Furthermore,errors in the surface and near-surface temperature and humidity explain almost 50%of the uncertainties in the estimates based on the bulk-formula,whereas errors in the net radiative fluxes explain more than 50%of the uncertainties in the MEP-based results.Zhi-Lun ZHANG Feng-Ming HUI Timo VIHMA Mats A.GRANSKOG Bin CHENG Zhuo-Qi CHEN Xiao CHENG 2023Advances in Climate Change Research2023,14,3:0
17Snow depth and ice thickness derived from SIMBA ice mass balance buoy data using an automated algorithm显示文摘An ice mass balance buoy(IMB)monitors the evolution of snow and ice cover on seas,ice caps and lakes through the measurement of various variables.The crucial measurement of snow and ice thickness has been achieved using acoustic sounders in early devices but a more recently developed IMB called the Snow and Ice Mass Balance Array(SIMBA)measures vertical temperature profiles through the air-snow-ice-water column using a thermistor string.The determination of snow depth and ice thickness from SIMBA temperature profiles is presently a manual process.We present an automated algorithm to perform this task.The algorithm is based on heat flux continuation,limit ratio between thermal heat conductivity of snow and ice,and minimum resolution(±0.0625°C)of the temperature sensors.The algorithm results are compared with manual analyses,in situ borehole measurements and numerical model simulation.The bias and root mean square error between algorithm and other methods ranged from 1 to 9 cm for ice thickness counting 2%–7%of the mean observed values.The algorithm works well in cold condition but becomes less reliable in warmer conditions where the vertical temperature gradient is reduced.Zeliang Liao Bin Cheng JieChen Zhao Timo Vihma Keith Jackson Qinghua Yang Yu Yang Lin Zhang Zhijun Li Yubao Qiu Xiao Cheng 2019International Journal of Digital Earth2019,12,8:0
18Preface to the Special Issue on Changing Arctic Climate and Low/Mid-latitudes Connections显示文摘The Arctic climate system has changed rapidly during recent decades with a two-four times faster warming rate than the global average subject to the uncertainties of analysis datasets and approaches.These changes have apparently resulted in broader and sizeable impacts within the Arctic,in the low/mid-latitudes,and globally.The importance of these changes and impacts makes the Arctic stand out within the global climate systems,drawing great attention and interests from the climate research community,the general public,and the government sector.One of the persistent,leading-edge topics in climate stud-ies during recent decades has therefore been to improve understanding of the underlying driving mechanisms,evaluate socioe-conomic and ecological impacts,and enhance the ability of the prediction and projections of Arctic climate changes.Xiangdong ZHANG Xianyao CHEN Andrew ORR James EOVERLAND Timo VIHMA Muyin WANG Qinghua YANG Renhe ZHANG 2023Advances in Atmospheric Sciences2023,40,12:0
19Linkages between Arctic sea ice cover,large-scale atmospheric circulation,and weather and ice conditions in the Gulf of Bothnia,Baltic Sea显示文摘During years 1980/1981–2012/2013, inter-annual variations in sea ice and snow thickness in Kemi, in the northern coast of the Gulf of Bothnia, Baltic Sea, depended on the air temperature, snow fall, and rain. Inter-annual variations in the November—April mean air temperature, accumulated total precipitation, snow fall, and rain, as well as ice and snow thickness in Kemi and ice concentration in the Gulf of Bothnia correlated with inter-annual variations of the Pacific Decadal Oscillation(PDO), Arctic Oscillation(AO), North Atlantic Oscillation(NAO), Scandinavian Pattern(SCA), and Polar / Eurasian Pattern(PEU). The strong role of PDO is a new finding. In general, the relationships with PDO were approximately equally strong as those with AO, but rain and sea ice concentration were better correlated with PDO. The correlations with PDO were, however, not persistent; for a study period since 1950 the correlations were much lower. During 1980/1981—2012/2013, also the Pacific / North American Pattern(PNA) and El Nino–Southern Oscillation(ENSO) had statistical connections with the conditions in the Gulf of Bothnia, revealed by analyzing their effects combined with those of PDO and AO. A reduced autumn sea ice area in the Arctic was related to increased rain and total precipitation in the following winter in Kemi. This correlation was significant for the Pan-Arctic sea ice area in September, October, and November, and for the November sea ice area in the Barents / Kara seas.Timo Vihma Bin Cheng Petteri Uotila WEI Lixin QIN Ting 2014Advances in Polar Science2014,25,4:0
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