1979年以来南极平流层冬季变暖

极地气候比其他区域有着更为显著的变化,这不仅反映在极地近地面和对流层,也同样反映在平流层。使用NCEP/NCAR、NCEP/DOE和ERA40月平均再分析资料,研究了南极平流层温度和位势高度的年代际变化趋势。结果表明,自1979年以来在冬季南极平流层存在变暖的趋势。分析NCEP/NCAR和NCEP/DOE再分析资料的结果是变暖主要出现在7—10月,最大增温位于30hPa,27a(1979—2005年)的最大增温幅度超过7℃。分析ERA40的结果是变暖主要出现在6—9月,较NCEP/NCAR和NCEP/DOE早1个月,最大增温位于平流层上层(5和3hPa),23a(1979—2001年)的最大增温幅度超过10℃。在平流层高层,最大增温位于极区中心;在平流层中低层,最大增温位于极区外围偏向澳大利亚一侧。伴随着温度的升高,南极平流层的位势高度也存在升高的趋势。在NCEP/NCAR和NCEP/DOE再分析资料中,最大位势高度升高位于10hPa,27a里的升高幅度超过450m。ERA40给出的结果相对弱一些,23a里的最大升高幅度接近300m。进一步的计算结果表明,进入南半球平流层的波动通量也有增加的趋势,可能是平流层波动增强导致了向南极的残余环流增强,与之相关的极圈内下沉运动也随之增强,下沉运动产生绝热加热,从而造成南极平流层增温和位势高度升高。     

Physical properties of aerosols at Maitri,Antarctica

Measurements of the submicron aerosol size distribution made at the Indian Antarctic station, Maitri (70‡45′S, 11‡44′E) from January 10th to February 24th, 1997, are reported. Total aerosol concentrations normally range from 800 to 1200 particles cm⁻³ which are typical values for the coastal stations at Antarctica in summer. Aerosol size distributions are generally trimodal and open-ended with a peak between 75 and 133 nm and two minima at 42 and 420 nm. Size distributions remain almost similar for several hours or even days in absence of any meteorological disturbance. Total aerosol concentration increases by approximately an order of magnitude whenever a low pressure system passes over the station. Based on the evolution of aerosol size-distributions during such aerosol enhancement periods, three types of cases have been identified. The nucleation mode in all three cases has been suggested to result from the photochemical conversion of the DMS emissions transported either by the marine air or by the air from the ice-melt regions around Maitri. Subsidence of midtropospheric air during the weakening of radiative inversion is suggested as a possible source of the nucleation mode particles in the third case. Growth of the nucleation mode particles by condensation, coagulation and/or by cloud processes has been suggested to be responsible for other modes in size distributions.     

Rapid decrease in Antarctic sea ice in recent years

A 41-year Antarctic sea ice concentration(SIC) dataset derived from satellite passive microwave radiometers during the period of 1979–2019 has been used to analyze sea ice changes in recent decades. The trends of SIC and sea ice extent(SIE) are calculated during the periods of 1979–2019, 1979–2013, and 2014–2019. The trends show regionally dependent features. The SIC shows an increasing trend in most of the regions except the Bellingshausen Sea and Amundsen Sea(BA) during 1979–2019 and 1979–2013. The SIE trend shows a decreasing or decelerating trend in the period of 1979–2019((6 835±2 210) km2/a) compared with the 1979–2013 period((18 600±2 203) km~2/a). In recent years(2014–2019), the SIC and SIE have exhibited decreasing trends(–(34 567±3 521) km~2/month), especially in the Weddell Sea(WS) and Ross Sea(RS) during summer and autumn. The trends are related to regionally dependent causes. The analyses show that the SIC and SIE decreased in response to the warming trend of 2 m air temperature(T_(a-2m)) and have exhibited a good relationship with T_(a-2m) in summer and autumn in recent years. The sea ice decrease in the Antarctic is mainly caused by increases in absorbed energy and southward energy transportation in recent years, such as the increase in gained solar radiation and moist static energy from the south, which demonstrate notable regional characteristics. In the WS region, the local positive feedback from the additional absorbed solar radiation, resulting in warmer air and reduced sea ice, is the main reason for the sea ice decrease in recent years. The increase in southward energy transport has also favored a decrease in sea ice. In the RS region, the increase in southward-transported moist static energy has contributed to the decrease in sea ice, and the increases in cloud cover and longwave radiation have prevented sea ice growth.     

MODIS海冰数据监测中山站附近海冰的季节性变化

本文利用中分辨率成像光谱仪(Moderate Resolution Imaging Spectroradiometer,即MODIS)的海冰数据,监测中山站附近区域海冰的季节性(尤其是夏季)的消融与冻结情况及海冰表面温度的变化。文中先对MODIS的海冰数据进行影像分层、数据合成,分时间段计算海冰范围,然后提取海冰表面温度信息,最后对获取的数据进行分析。研究结果表明,中山站附近区域在每年10月至翌年2月中上旬为海冰消融期;2月中下旬至4月为海冰冻结非密封期;5月至9月为海冰冻结密封期。海冰范围2月份最小;海冰表面温度1月份最低,8月份最高。     

南极特别保护区的现状与展望

通过梳理南极条约协商会议(ATCM)形成的相关文件,概述了南极特别保护区设立的发展和南极特别保护区管理计划(草案)的编写与批准流程。对已批准设立的67个南极特别保护区进行统计分析发现,目前保护区总面积超过2700平方千米,分别由13个南极条约协商国提请设立,其中,美国、英国、澳大利亚、新西兰、智利等国提出的占绝大多数;1966年和1985年为保护区设立的两个高峰年份。这些保护区主要以动植物、动植物栖息地或者生态系统为保护内容、以科学价值为保护目标。此外,简要地分析保护区建设的现状、问题和未来发展,介绍我国的南极特别保护区申报工作。     

南极红藻Iridaea cordata和Curdiea racovitzae转录组分析及其极端光环境适应相关基因的挖掘

南极红藻具有重要的生态学功能和开发利用价值。南极极端环境赋予了其独特的生理耐受机制,也是发现新基因和代谢途径的理想材料。我们测序分析了南极产胶红藻Iridaea cordata (Turner) Bory和Curdiea racovitzae Hariot的转录组序列,并与其常温近缘种进行了比较,同时挖掘了其与光限制和强紫外线辐射等光环境适应相关的基因。I. cordata和C. racovitzae的转录组序列分别拼接成了14 055条和12 006条非冗余基因,平均长度分别为1 473 bp和1 448 bp。在I. cordata转录组中发现多条与绿藻基因同源的捕光复合物LHC基因Lhca2、Lhca6和Lhcb,并且在两种南极红藻中都各发现了1条编码结合岩藻黄质和Chl a/c蛋白的Lhcf基因,目前尚未在其他红藻中发现这类基因。光裂解酶修复紫外线诱导DNA损伤,在I. cordata的转录组序列中发现了6-4光裂解酶,光裂解酶CPD Ⅰ和CPD Ⅱ基因,而C. racovitzae转录组序列中仅找到了光裂解酶CPD Ⅱ基因。尽管南极红藻中这些特有基因的功能有待进一步的验证,但...     

Impact of Assimilation of Radiosonde and UAV Observations from the Southern Ocean in the Polar WRF Model

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 rad...     

Stratospheric Ozone-induced Cloud Radiative Effects on Antarctic Sea Ice

Recent studies demonstrate that the Antarctic Ozone Hole has important influences on Antarctic sea ice. While most of these works have focused on effects associated with atmospheric and oceanic dynamic processes caused by stratospheric ozone changes, here we show that stratospheric ozone-induced cloud radiative effects also play important roles in causing changes in Antarctic sea ice. Our simulations demonstrate that the recovery of the Antarctic Ozone Hole causes decreases in clouds over Southe...     

基于FY-3C微波辐射计数据的极区海冰密集度反演方法研究

极区海冰影响大气和海洋环流,对全球气候变化起着重要的作用。海冰密集度是表征海冰时空变化特征的重要参数之一。本文研究了利用FY-3C微波扫描辐射计亮温数据反演极区海冰密集度的方法。经过时空匹配、线性回归,修正了FY-3C微波辐射计亮温数据。使用两种天气滤波器和海冰掩模滤除了大气影响所造成的开阔海域虚假海冰;使用最小密集度模板去除陆地污染效应。通过计算2016年、2017年极区海冰面积及范围两个参数,对得到的海冰密集度产品进行了验证,两年的海冰范围和面积趋势基本与NSIDC产品一致,平均差异小于3%。本研究结果为发布我国自主卫星的极区海冰密集度业务化产品奠定了基础,制作的产品可保障面临中断的40多年极区海冰记录的连续性。     

南极对流层-平流层下部气候变化特征及其原因

利用南极16站30余年地面至30hPa10层月平均气温距平序列资料,采用最大熵功率谱方法,研究了南极对流层至平流层下部气候变化的长期趋势和周期性特征,并讨论了平流层(对流层)气候变化与南极臭氧总量(南半球500hPa环流)变化之间的联系。指出:南极气温具有明显的长期趋势和周期性变化;平流层下部显着变冷、对流层增暖,变化最大层高度在100、700hPa,最大降冷速率远大于增暖速率,气层稳定度趋于减弱;30、50hPa气温具有准两年周期,100hPa上下具有显着的年周期,对流层是以3.5年甚低频周期为主;对流层顶气温无显着趋势变化和周期性变化;南极最大臭氧层高度显着变冷与近15年来臭氧层损耗有关。南半球对流层中部极涡及绕极气流减弱是南极对流层气候变暖的直接原因。