南极Dome A至普里兹湾沿岸下降风特征

本文利用我国极地数值天气预报系统和美国南极中尺度预报系统的存档数据,分析了Dome A至普里兹湾沿岸地区下降风风场的时空分布和大气质量通量,给出了该地区下降风的基本特点。该地区下降风受南极冰盖地形影响强烈,艾默里冰架西侧等陡峭地区风速总体较大;下降风随季节变化较大,冬季的下降风较强。强下降风在前进过程中有绝热增温现象,并给艾默里冰架西部带来近表层升温。下降风风速最大处位于地面以上约100~200 m高度,风速较大地区的下降风在垂直方向上分布较为深厚。下降风在普里兹湾沿岸的表层大气质量通量在时空分布上极不均匀,艾默里冰架西侧的下降风气流较强时,普里兹湾海域有较多的中尺度气旋活动。下降风引发普里兹湾中尺度气旋旋生的过程值得关注,需进一步研究下降风引发中尺度气旋的机理。

青贮杂交构树对育肥肉羊生长性能、屠宰性能及器官指数的影响

试验旨在研究不同添加比例青贮杂交构树对育肥肉羊生长性能、屠宰性能及器官指数的影响,探讨青贮杂交构树替代豆粕作为蛋白质原料饲喂肉羊的可行性。试验选取体重(26.25±1.92)kg的杜泊×湖羊F1代公羊48只,随机分为4组,每组12只羊,对照组(CG组)、试验组(LG组、MG组、HG组)分别饲喂添加0%、6%、12%和18%青贮杂交构树而营养水平相同的试验饲粮,试验期90 d。结果表明:(1)CG、LG、MG、HG组间平均日采食量、料肉比、器官指数均无显著差异(P>0.05);(2)HG组屠宰率较CG组降低10.9%(P<0.05);(3)MG组增重最大,料肉比最低,增重盈利比CG组高54.37元。综上,育肥肉羊日粮中用适量青贮杂交构树替代豆粕作为蛋白质饲料是可行的,且可降低饲料成本,适宜的日粮配方可提高动物增重和饲养收益,对发展节粮型肉羊养殖业具有推广价值,本试验条件下,以添加12%青贮杂交构树经济效益最高。

Observed and modelled snow and ice thickness in the Arctic Ocean with CHINARE buoy data

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 during 2014-2015. The total ice thickness increased from an initial August 2014 value of 1.97 m to a maximum value of 2.45 in before the onset of snow melt in May 2015; the last observation was approximately 1 m in late November 2015. 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.

Sensitivity of the Arctic sea ice concentration forecasts to different atmospheric forcing: a case study

A regional Arctic configuration of the Massachusetts Institute of Technology general circulation model （MIT-gcm） is used as the coupled ice-ocean model for forecasting sea ice conditions in the Arctic Ocean at the Na-tional Marine Environmental Forecasting Center of China （NMEFC）, and the numerical weather prediction from the National Center for Environmental Prediction Global Forecast System （NCEP GFS） is used as the atmospheric forcing. To improve the sea ice forecasting, a recently developed Polar Weather Research and Forecasting model （Polar WRF） model prediction is also tested as the atmospheric forcing. Their forecasting performances are evaluated with two different satellite-derived sea ice concentration products as initializa-tions： （1） the Special Sensor Microwave Imager/Sounder （SSMIS） and （2） the Advanced Microwave Scanning Radiometer for EOS （AMSR-E）. Three synoptic cases, which represent the typical atmospheric circulations over the Arctic Ocean in summer 2010, are selected to carry out the Arctic sea ice numerical forecasting experiments. The evaluations suggest that the forecasts of sea ice concentrations using the Polar WRF atmo-spheric forcing show some improvements as compared with that of the NCEP GFS.

Inter-comparisons of thermodynamic sea-ice modeling results using various parameterizations of radiative flux

Radiative fluxes are of primary importance in the energy and mass balance of the sea-ice cover. Various parameterizations of the radiative fluxes are studied in a thermodynamic sea-ice model. Model outputs of the surface radiative and heat fluxes and mass balance are compared with observations. The contribution of short-wave radiation is limited to a long part of winter. Therefore, simple schemes are often sufficient. Errors in estimations of the short-wave radiation are due mainly to cloud effects and occasionally to multi-reflection between surface and ice crystals in the air. The long-wave radiation plays an important role in the ice surface heat and mass balance during most part of a winter. The effect of clouds on the accuracy of the simple radiative schemes is critical, which needs further attention. In general, the accuracy of an ice model depends on that of the radiative fluxes.

Review of research on Arctic sea ice physics based on the Chinese National Arctic Research Expedition

China launched its Arctic research program and organized the first Chinese National Arctic Research Expedition （CHINARE-Arctic） in 1999. By 2016, six further expeditions had been conducted using the R/V Xuelong. The main region of the expeditions has focused on the Pacific sector of the Arctic Ocean for sea ice observations. The expeditions have used icebreaker, helicopter, boat, floe, and buoy platforms to perform these observations. Some new technologies have been developed, in particular, the underway auto-observing system for sea ice thickness using an electromagnetic instrument. The long-term measurement systems, e.g., the sea ice mass balance buoy, allow observations to extend from summer to winter. Some international cooperation projects have been involved in CHINARE-Arctic, especially the ＂Developing Arctic Modeling and Observing Capabilities for Long-Term Environmental Studies＂ project funded by the European Union during the International Polar Year. Arctic sea ice observations have been used to verify remote sensing products, identify changes in Arctic sea ice, optimize the parameterizations of sea ice physical processes, and assess the accessibility of ice-covered waters, especially around the Northeast Passage. Recommendations are provided as guidance to future CHINARE-Arctic projects. For example, a standardized operation system of sea ice observations should be contracted, and the observations of sea ice dynamics should be enhanced. The upcoming launch of a new Chinese icebreaker will allow increased ship time in support of future CHINARE Arctic oceanographic investigations.

冠状动脉旁路移植术治疗围手术期难治性冠状动脉痉挛临床分析

目的:探讨冠状动脉旁路移植术(CABG)治疗难治性冠状动脉痉挛(CAS)的可行性和有效性。方法:对2018年6月至2019年12月,在临床心脏外科工作中遇到的4例围手术期难治性CAS患者进行回顾性分析。4例患者均为原计划心脏手术完成后并发的急性CAS,出现血流动力学不稳定,药物治疗无效后被迫进行CABG。4例患者年龄43~63岁,男性3例,女性1例。冠状动脉肌桥1例,行冠状动脉前降支肌桥松解术;主动脉瓣重度反流1例,行主动脉瓣置换术;冠心病2支病变1例,行CABG术;急性心肌梗死并发室间隔穿孔(VSR)1例,行VSR旷置术。结果:4例患者均被迫行CABG,术后患者未再出现CAS表现,除AVR患者术后发生急性I型主动脉夹层死亡外,其他3例均恢复良好,随访3~18个月,患者均未再发生CAS表现。结论:CABG可能是治疗难治性CAS—种可行而且有效的外科治疗方法。

Evolution and breaking of a propagating internal wave in stratified ocean

The evolution and breaking of a propagating internal wave are directly numerically simulated using a pseudo-spectral method. The mechanism of PSI （ parametric subharmonic instability） involved in the evolution is testified clearly. It dominates gradually in nonlinear resonant interactions. As a consequence, the energy cascades to a second plant wave packet which has lower frequencies and higher wavenumbers than that of the primary wave. With the growth of this wave packet, wave breaking occurs and causes strongly nonlinear regime, i.e. stratified turbulence. The strong mixing and intermittent of the turbulence can be learned from the evolution of the total energy and kurtosis of vorticity vs. time. Some statistic properties of the stratified turbulence are also analyzed, including the spectra of KE （kinetic energy） and PE （potential energy）. The results show that the PE spectra display a wavenumber range scaling as 0. 2 N^4ky^-3 （N is the Brunt - Vaisala frequency, k, is the vertical wavenumber）, which is called buoyancy sub-range. However, the KE spectra cannot satisfy the negative cubic law of vertical wavenumber, which have a much larger downtrend than that of the PE spectra, for the potential energy is transferred more efficiently toward small scales than the kinetic energy. The Cox number of diapycnal diffusivity is also calculated, and it shows a good consistency with the observations and deductions in the ocean interior, during the stage of the stratified turbulence maintaining a fairly active level.

Snow and sea ice thermodynamics in the Arctic:Model validation and sensitivity study against SHEBA data

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.

Interaction of an anticyclonic eddy with sea ice in the western Arctic Ocean:an eddy-resolving model study

The dramatic decline of summer sea ice extent and thickness has been witnessed in the western Arctic Ocean in recent decades, which has motivated scientists to search for possible factors driving the sea ice variability. An eddy-resolving, ice-ocean coupled model covering the entire Arctic Ocean is implemented, with focus on the western Arctic Ocean. Special attention is paid to the summer Maskan coastal current （ACC）, which has a high temperature （up to 5℃ or more） in the upper layer due to the solar radiation over the open water at the lower latitude. Downstream of the ACC after Barrow Point, a surface-intensified anticyclonic eddy is frequently generated and propagate towards the Canada Basin during the summer season when sea ice has retreated away from the coast. Such an eddy has a warm core, and its source is high-temperature ACC water. A typical warm-core eddy is traced. It is trapped just below summer sea ice melt water and has a thickness about 60 m. Temperature in the eddy core reaches 2-3℃, and most water inside the eddy has a temperature over 1℃. With a definition of the eddy boundary, an eddy heat is calculated, which can melt 1 600 km2 of 1 m thick sea ice under extreme conditions.

Sensitivity and nonlinearity of Eurasian winter temperature response to recent Arctic sea ice loss

The recent decline in the Arctic sea ice has coincided with more cold winters in Eurasia. It has been hypothesized that the Arctic sea ice loss is causing more mid-latitude cold extremes and cold winters, yet there is lack of consensus in modeling studies on the impact of Arctic sea ice loss. Here we conducted modeling experiments with Community Atmosphere Model Version 5 （CAM5） to investigate the sensitivity and linearity of Eurasian winter temperature response to the Atlantic sector and Pacific sector of the Arctic sea ice loss. Our experiments indicate that the Arctic sea ice reduction can significantly affect the atmospheric circulation by strengthening the Siberian High, exciting the stationary Rossby wave train, and weakening the polar jet stream, which in turn induce the cooling in Eurasia. The temperature decreases by more than I^C in response to the ice loss in the Atlantic sector and the cooling is less and more shifts southward in response to the ice loss in the Pacific sector. More interestingly, sea ice loss in the Atlantic and Pacific sectors together barely induces cold temperatures in Eurasia, suggesting the nonlinearity of the atmospheric response to the Arctic sea ice loss.

Arctic autumn sea ice decline and Asian winter temperature anomaly

Associations between the autumn Arctic sea ice concentration （SIC） and Asian winter temperature are discussed using the singular value decomposition analysis. Results show that in recent 33 years reduced autumn Arctic sea ice is accompanied by Asian winter temperature decrease except in the Tibetan plateau and the Arctic Ocean and the North Pacific Ocean coast. The autumn SIC reduction excites two geopotential height centers in Eurasia and the north Arctic Ocean, which are persistent from autumn to winter. The negative center is in Barents Sea/Kara Sea. The positive center is located in Mongolia. The anomalous winds are associated with geopotential height centers, providing favorable clod air for the Asian winter temperature decreasing in recent 33 years. This relationship indicates a potential long-term outlook for the Asian winter temperature decrease as the decline of the autumn sea ice in the Arctic Ocean is expected to continue as climate warms.

Severe winter weather as a response to the lowest Arctic sea-ice anomalies

Possible impact of reduced Arctic sea-ice on winter severe weather in China is investigated regarding the snowstorm over southern China in January 2008. The sea-ice conditions in the summer （July-September） and fall （September-November） of 2007 show that the sea-ice is the lowest that year. During the summer and fall of 2007, sea ice displayed a significant decrease in the East Siberian, the northern Chukchi Sea, the western Beaufort Sea, the Barents Sea, and the Kara Sea. A ECHAM5.4 atmospheric general circula- tion model is forced with realistic sea-ice conditions and strong thermal responses with warmer surface air temperature and higher-than-normal heat flux associated with the sea-ice anomalies are found. The model shows remote atmospheric responses over East Asia in January 2008, which result in severe snowstorm over southern China. Strong water-vapor transported from the Bay of Bengal and from the Pacific Ocean related to Arctic sea-ice anomalies in the fall （instead of summer） of 2007 is considered as one of the main causes of the snowstorm formation.

Western Indian Ocean SST signal and anomalous Antarctic sea-ice concentration variation

Teleconnection between El Nino/La Nina-Southern Oscillation （ENSO） phenomenon and anomalous Antarctic sea-ice variation has been studied extensively.In this study,impacts of sea surface temperature in the Indian Ocean on Antarctic sea-ice change were investigated during Janaury 1979 and October 2009.Based on previous research results,sea areas in the western Indian Ocean （WIO;50°–70°E,10 °–20 °S） are selected for the resreach.All variables showed 1-10 year interannual timescales by Fast Founer Tranaform （FFT） transformation.Results show that i） strong WIO signals emerged in the anomalous changes of Antarctic sea-ice concentration;ii） significant positive correlations occurred around the Antarctic Peninsula,Ross Sea and its northwest peripheral sea region iii） negative correlation occurred in the Indian Ocean section of the Southern Ocean,Amundsen Seas,and the sea area over northern Ross Sea;and iv） the atmospheric anomalies associated with the WIO including wind,meridional heat flux,and surface air temperature over southern high latitudes were the possible factors for the teleconnection.

Dominant climate factors influencing the Arctic runoff and association between the Arctic runoff and sea ice

By using the Arctic runoff data from R-ArcticNET V4.0 and ArcticRIMS,trends of four major rivers flowing into the Arctic Ocean,whose climate factor plays an important role in determining the variability of the Arctic runoff,are investigated.The results show that for the past 30 years,the trend of the Arctic runoff is seasonally dependent.There is a significant trend in spring and winter and a significant decreasing trend in summer,leading to the reduced seasonal cycle.In spring,surface air temperature is the dominant factor influencing the four rivers.In summer,precipitation is the most important factor for Lena and Mackenzie,while snow cover is the most important factor for Yenisei and Ob.For Mackenzie,atmospheric circulation does play an important role for all the seasons,which is not the case for the Eurasian rivers.The authors further discuss the relationships between the Arctic runoff and sea ice.Significant negative correlation is found at the mouth of the rivers into the Arctic Ocean in spring,while significant positive correlation is observed just at the north of the mouths of the rivers into the Arctic in summer.In addition,each river has different relationship with sea ice in the eastern Greenland Sea.

Meteorological observations and weather forecasting services of the CHINARE

By 2018, China had conducted 34 scientific explorations in Antarctica spearheaded by the Chinese National Antarctic Research Expedition(CHINARE). Since the first CHINARE over 30 years ago, considerable work has been undertaken to promote the development of techniques for the observation of surface and upper-air meteorological elements, and satellite image and data reception systems at Chinese Antarctic stations and onboard Chinese icebreakers have played critical roles in this endeavor. The upgrade of in situ and remote sensing measurement methods and the improvement of weather forecasting skill have enabled forecasters to achieve reliable on-site weather forecasting for the CHINARE. Nowadays, the routing of icebreakers, navigation of aircraft, and activities at Chinese Antarctic stations all benefit from the accurate weather forecasting service. In this paper, a review of the conventional meteorological measurement and operational weather forecasting services of the CHINARE is presented.

Association between Arctic autumn sea ice concentration and early winter precipitation in China

Associations between autumn Arctic sea ice concentration（SIC） and early winter precipitation in China are studied using singular value decomposition analysis. The results show that a reduced SIC almost everywhere in the Arctic Ocean, except the northern Greenland Sea and Canadian Basin, are accompanied by dry conditions over central China, extending northeast from the Tibetan Plateau toward the Japan Sea, the Bohai Sea and the Yellow Sea, and wet conditions over South China and North China. Atmospheric circulation anomalies associated with SIC variability show two wave-train structures, which are persistent from autumn to winter, leading to the identified relationship between autumn Arctic SIC and early winter precipitation in China. Given that the decline in autumn SIC in the Arctic Ocean is expected to continue as the climate warms, this relationship provides a possible long-term outlook for early winter precipitation in China.

Investigation of Arctic air temperature extremes at north of 60°N in winter

Air temperature is a key index reflecting climate change. Air temperature extremes are very important because they strongly influence the natural environment and societal activities. The Arctic air temperature extremes north of 60°N are investigated in the winter. Daily data from 238 stations at north of 60°N from the global summary of the day for the period 1979–2015 are used to study the trends of cold days, cold nights, warm days and warm nights during the wintertime. The results show a decreasing trend of cold days and nights（rate of –0.2 to –0.3 d/a） and an increasing trend of warm days and nights（rate of ＋0.2 to ＋0.3 d/a） in the Arctic. The mean temperature increases,which contributes to the increasing（decreasing） occurrence of warm（cold） days and nights. On the other hand,the variance at most stations decreased, leading to a reduced number of cold events. A positive AO（Arctic Oscillation） index leads to an increased（decreased） number of warm（cold） days and nights over northern Europe and western Russia and an increased（decreased） number of cold（warm） days and nights over the Bering Strait and Greenland. The lower extent of Arctic autumn sea ice leads to a decreased number of cold days and nights.The occurrences of abrupt changes are detected using the Mann-Kendall method for cold nights occurring in Canada in 1998 and for warm nights occurring in northwestern Eurasia in 1988. This abrupt change mainly resulted from the mean warming induced by south winds and an increased North Atlantic sea surface temperature.

The rise of sea ice research collaboration between China and Finland

Collaboration between China and Finland in marine sciences was commenced in winter 1988.The main topic was then short-term sea ice forecasting in the seasonal sea ice zone(SSIZ),particularly in the Bohai Sea in China and the Baltic Sea in Finland.The sea ice in SSIZ is thin and highly dynamic so that ice conditions may change rapidly.While the length scales of the Baltic Sea and the Bohai Sea are similar,the main difference between them is that the former is brackish and non-tidal while the latter is oceanic for the salinity and possesses a large tidal amplitude.The Bohai Sea is located at latitudes 37°N-41°N,and the Baltic Sea is located at latitudes 55°N-66°N.However,the same sea ice model is applicable for both.The main application field of sea ice forecasting was winter shipping in Finland and oil drilling in China.The collaboration was successful and in late 1990s the research was expanded to polar seas,lakes,and to climate change applications.

Thermodynamic processes of lake ice and landfast ice around Zhongshan Station, Antarctica

Thermodynamic processes of ice in three lakes and landfast ice around Zhongshan Station, Antarctica, were observed in 2006. The mass balance of lake ice was compared with that of landfast ice. The responses of lake ice and sea ice temperatures to the local surface air temperature are explored. Vertical conductive heat fluxes at varying depths of lake ice and sea ice were derived from vertical temperature profiles. The freeze up of lake ice and landfast ice occurred from late February to early March. Maximum lake ice thicknesses occurred from late September to early October, with values of 156-177 cm. The maximum sea ice thicknesses of 167-174 cm occurred relatively later, from late October to late November. Temporal variations of lake ice and landfast ice internal temperatures lagged those of air temperatures. High-frequency variations of air temperature were evidently attenuated by ice cover. The temporal lag and the high-frequency attenuation were greater for sea ice than for lake ice, and more distinct for the deeper ice layer than for the upper ice layer. This induced a smaller conductive heat flux through sea ice than lake ice, at the same depth and under the same atmospheric forcing, and a smoother fluctuation in the conductive heat flux for the deeper ice layer than for the upper ice layer. Enhanced desalination during the melt season increased the melting point temperature within sea ice, making it different from fresh lake ice.