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| 1 | How does the Indian Ocean subtropical dipole trigger the tropical Indian Ocean dipole via the Mascarene high?显示文摘The variation in the Indian Ocean is investigated using Hadley center sea surface temperature(SST)data during the period 1958–2010.All the first empirical orthogonal function(EOF)modes of the SST anomalies(SSTA)in different domains represent the basin-wide warming and are closely related to the Pacific El Ni o–Southern Oscillation(ENSO)phenomenon.Further examination suggests that the impact of ENSO on the tropical Indian Ocean is stronger than that on the southern Indian Ocean.The second EOF modes in different domains show different features.It shows a clear east-west SSTA dipole pattern in the tropical Indian Ocean(Indian Ocean dipole,IOD),and a southwest-northeast SSTA dipole in the southern Indian Ocean(Indian Ocean subtropical dipole,IOSD).It is further revealed that the IOSD is also the main structure of the second EOF mode on the whole basin-scale,in which the IOD pattern does not appear.A correlation analysis indicates that an IOSD event observed during the austral summer is highly correlated to the IOD event peaking about 9 months later.One of the possible physical mechanisms underlying this highly significant statistical relationship is proposed.The IOSD and the IOD can occur in sequence with the help of the Mascarene high.The SSTA in the southwestern Indian Ocean persists for several seasons after the mature phase of the IOSD event,likely due to the positive wind–evaporation–SST feedback mechanism.The Mascarene high will be weakened or intensified by this SSTA,which can affect the atmosphere in the tropical region by teleconnection.The pressure gradient between the Mascarene high and the monsoon trough in the tropical Indian Ocean increases(decreases).Hence,an anticyclone(cyclone)circulation appears over the Arabian Sea-India continent.The easterly or westerly anomalies appear in the equatorial Indian Ocean,inducing the onset stage of the IOD.This study shows that the SSTA associated with the IOSD can lead to the onset of IOD with the aid of atmosphere circulation and also explains why some IOD events in the tropical tend to be followed by IOSD in the southern Indian Ocean. | FENG Junqiao HU Dunxin YU Lejiang | 2014 | Acta Oceanologica Sinica2014，33，1： | 3 |
| 2 | Sensitivity and nonlinearity of Eurasian winter temperature response to recent Arctic sea ice loss显示文摘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 1°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. | SUI Cuijuan ZHANG Zhanhai YU Lejiang LI Yi SONG Mirong | 2017 | Acta Oceanologica Sinica2017，36，8： | 2 |
| 3 | An Unprecedented Record Low Antarctic Sea-ice Extent during Austral Summer 2022显示文摘Seasonal minimum Antarctic sea ice extent(SIE)in 2022 hit a new record low since recordkeeping began in 1978 of 1.9 million km^(2) on 25 February,0.17 million km^(2) lower than the previous record low set in 2017.Significant negative anomalies in the Bellingshausen/Amundsen Seas,the Weddell Sea,and the western Indian Ocean sector led to the new record minimum.The sea ice budget analysis presented here shows that thermodynamic processes dominate sea ice loss in summer through enhanced poleward heat transport and albedo-temperature feedback.In spring,both dynamic and thermodynamic processes contribute to negative sea ice anomalies.Specifically,dynamic ice loss dominates in the Amundsen Sea as evidenced by sea ice thickness(SIT)change,while positive surface heat fluxes contribute most to sea ice melt in the Weddell Sea. | Jinfei WANG Hao LUO Qinghua YANG Jiping LIU Lejiang YU Qian SHI Bo HAN | 2022 | Advances in Atmospheric Sciences2022，39，10： | 1 |
| 4 | The variability of surface radiation fluxes over landfast sea ice near Zhongshan station,east Antarctica during austral spring显示文摘Surface radiative fluxes over landfast sea ice off Zhongshan station have been measured in austral spring for five springs between 2010 and 2015.Downward and upward solar radiation vary diurnally with maximum amplitudes of 473 and 290 W m^(−2),respectively.The maximum and minimum long-wave radiation values of the mean diurnal cycle are 218 and 210 W m^(−2)for downward radiation,277 and 259 W m^(−2)for upward radiation and 125 and−52 W m^(−2)for net radiation.The albedo has a U-shaped mean diurnal cycle with a minimum of 0.64 at noon.Sea ice thickness is in the growth phase for most spring days,but can be disturbed by synoptic processes.The surface temperature largely determines the occurrence of ice melting.Surface downward and upward long-wave radiation show synoptic oscillations with a 5–8 day period and intraseasonal variability with a 12–45 day period.The amplitudes of the diurnal,synoptic and intraseasonal variability show some differences during the five austral springs considered here.The intraseasonal and synoptic variability of downward and upward long-wave radiation are associated with the variability of cloud cover and surface temperature induced by the atmospheric circulation. | Lejiang Yu Qinghua Yang Mingyu Zhou Donald H.Lenschow Xianqiao Wang Jiechen Zhao Qizhen Sun Zhongxiang Tian Hui Shen Lin Zhang | 2019 | International Journal of Digital Earth2019，12，8： | 1 |
| 5 | Investigation of Arctic air temperature extremes at north of 60°N in winter显示文摘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. | SUI Cuijuan ZHANG Zhanhai YU Lejiang LI Yi SONG Mirong | 2017 | Acta Oceanologica Sinica2017，36，11： | 1 |
| 6 | Influence of the Atlantic Multidecadal Oscillation and Interdecadal Pacific Oscillation on Antarctic surface air temperature during 1900 to 2015显示文摘The importance of the Atlantic Multidecadal Oscillation(AMO)and Interdecadal Pacific Oscillation(IPO)in influencing zonally asymmetric changes in Antarctic surface air temperature(SAT)has been established.However,previous studies have primarily concentrated on examining the combined impact of the contrasting phases of the AMO and IPO,which have been dominant since the advent of satellite observations in 1979.This study utilizes long-term reanalysis data to investigate the impact of four combinations of+AMO+IPO,–AMO–IPO,+AMO–IPO,and–AMO+IPO on Antarctic SAT over the past 115 years.The+AMO phase is characterized by a spatial mean temperature amplitude of up to 0.5℃over the North Atlantic Ocean,accompanied by positive sea surface temperature(SST)anomalies in the tropical eastern Pacific and negative SST anomalies in the extratropical-mid-latitude western Pacific,which are indicative of the+IPO phase.The Antarctic SAT exhibits contrasting spatial patterns during the+AMO+IPO and+AMO–IPO periods.However,during the–AMO+IPO period,apart from the Antarctic Peninsula and the vicinity of the Weddell Sea,the entire Antarctic region experiences a warming trend.The most pronounced signal in the SAT anomalies is observed during the austral autumn,whereas the combination of–AMO and–IPO exhibits the smallest magnitude across all the combinations.The wavetrain excited by the SST anomalies associated with the AMO and IPO induces upper-level and surface atmospheric circulation anomalies,which alter the SAT anomalies.Furthermore,downward longwave radiation anomalies related to anomalous cloud cover play a crucial role.In the future,if the phases of AMO and IPO were to reverse(AMO transitioning to a negative phase and IPO transitioning to a positive phase),Antarctica could potentially face more pronounced warming and accelerated melting compared to the current observations. | Cuijuan Sui Lejiang Yu Alexey YuKarpechko Licheng Feng Shan Liu | 2024 | Acta Oceanologica Sinica2024，43，3： | 0 |
| 7 | Characteristics of hydrogen/oxygen isotopes in water masses and implications for spatial distribution of freshwater in the Amundsen Sea,Southern Ocean显示文摘Antarctica’s marginal seas are of great importance to atmosphere-ocean-ice interactions and are sensitive to global climate change.Multiple factors account for the freshwater budget in these regions,including glacier melting,seasonal formation/decay of sea ice,and precipitation.Hydrogen(H)and oxygen(O)isotopes represent useful proxies for determining the distribution and migration of water masses.We analyzed the H and O isotopic compositions of 190 seawater samples collected from the Amundsen Sea during the 34th Chinese Antarctic Research Expedition in 2017/2018.The upper-oceanic structure(<400 m)and freshwater(meteoric water and sea ice melt)distribution in the Amundsen Sea were identified based on conductivity-temperature-depth data and the H and O isotopic composition.Antarctic Surface Water,characterized as cold and fresh with low H and O isotopic ratios,was found distributed mainly in the upper~150 m between the Antarctic Slope Front and Polar Front,where it had been affected considerably by upwelled Upper Circumpolar Deep Water(UCDW)between 68°S and 71°S.A three-endmember(meteoric water,sea ice melt,and Circumpolar Deep Water)mixing model indicated that waters with relatively high proportions(>3%)of freshwater generally lie in the upper~50 m and extend from Antarctica to~65°S in the meridional direction(anomalously low freshwater proportion occurred between 68°S and 71°S).Winter Water mainly occupied the layer between 50 and 150 m south of 71°S in the western Amundsen Sea.The water structure and spatial distribution of freshwater in the upper Amundsen Sea were found influenced mainly by the rates of basal and surficial melting of ice shelves,seasonal alternation of sea ice melt/formation,wind forcing,and regional bathymetry.Owing to the distance between heavy sea ice boundary(HSIB)and ice shelves is much shorter in the western HSIB than the east HSIB,the western part of the heavy sea ice boundary includes a higher proportion of freshwater than the eastern region.This study,which highlighted the distribution and extent of freshwater derived from ice(ice shelves and sea ice)melt,provides important evidence that the offshore drift pathway of cold and fresh Antarctic continental shelf water is likely interrupted by upwelled UCDW in the Amundsen Sea. | SHAO Hebin HE Jianfeng LUO Guangfu LAN Musheng YU Lejiang GUO Guijun LIAN Ergang | 2021 | Advances in Polar Science2021，32，3： | 0 |
| 8 | Trends of summertime extreme temperatures in the Arctic显示文摘Extreme temperature events can influence the natural environment and societal activities more so than mean temperature events. This study used daily data from 238 stations north of 60°N, obtained from the Global Summary of the Day dataset for the period 1979–2015, to investigate the trends of summertime extreme temperature. The results revealed most stations north of 60°N with trends of decrease in the number of cold days(nights) and increase in the number of warm days(nights). The regional average results showed trends of consistent decline(rise) of cold days and nights(warm days and nights) in Eurasia and Greenland. Similarly, the trends of the seasonal maximum and minimum values were most significant in these regions. In summer, of three indices considered(i.e., Arctic Oscillation, Arctic dipole, and El Ni?o–Southern Oscillation), the largest contributor to the trends of extreme temperature events was the Arctic dipole. Prevailing southerly winds in summer brought warm moist air across northern Eurasia and Greenland, conducive to increased numbers of warm days(nights) and decreased numbers of cold day(nights). Moreover, we defined extreme events using different thresholds and found the spatial distributions of the trends were similar. | SUI Cuijuan YU Lejiang | 2018 | Advances in Polar Science2018，29，3： | 0 |
| 9 | Features of visibility variation at Great Wall Station,Antarctica显示文摘The variation of visibility at Great Wall Station(GWS)was analyzed using manual observational data for the period of1986 to 2012.Results show that the frequencies of occurrence of high(≥10 km)and low visibility(0-1 km)are 61.0%and8.0%,respectively.Visibility at GWS shows an evident seasonal variation:The highest visibility between November and March,and the lowest visibility from June to October.Sea fog and precipitation are the main factors for low visibility during summer,whereas frequent adverse weather,such as falling snow,blowing snow,or blizzards,are responsible for low visibility in winter.The frequency of occurrence of low visibility has decreased significantly from 1986 to 2012.Conversely,the frequency of occurrence of high visibility has shown a significant increasing trend,especially during winter.The decreasing tendencies of fog,blowing snow,and snowfall have contributed to the increasing trend of high visibility during winter.Visibility at GWS exhibits significant synoptic-scale(2.1 to 8.3 d),annual,and inter-annual periods(2 a,4.1 a,and 6.9 a to 8.2 a),among which the most significant period is 4.1 a.The visibility observed during 2012 indicates that instrumental observation can be applied in the continuous monitoring of visibility at GWS. | YANG Qinghua YU Lejiang WEI Lixin ZHANG Benzheng MENG Shang | 2013 | Advances in Polar Science2013，24，3： | 0 |
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