共查询到20条相似文献，搜索用时 28 毫秒
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Ellsworth G. Dutton John J. DeLuisi Gary Herbert 《Journal of Atmospheric Chemistry》1989,9(1-3):71-79
Measurements of spectral aerosol optical depth in the Alaskan and Canadian Arctic were made from the NOAA Lockheed WP-3D aircraft as part of the second Arctic Gas and Aerosol Sampling Program (AGASP-II) during April 1986. The flight tracks and altitudes flown enabled measurements of the vertical and horizontal distribution of aerosol optical depth in the troposphere as well as direct determination of the stratospheric component. Tropospheric aerosol optical depth ranged from about 0.1 to 0.7. The factor of 7 variability sometimes occurred within 50 km horizontally; comparable variability occurred within less than 1 to 2 km vertically. The Angstrom exponents of the spectral optical depths ranged from 0.5 to 2.0, and some of the variability was apparently related to distinct aerosol regimes. 相似文献
3.
300 hPa北极涡年际及年代际变化特征的研究 总被引：2，自引：2，他引：2
利用NCEP/NCAR 1949—2002年月平均再分析高度场资料,通过线性倾向估计、二项式系数加权平均、Morlet小波分析等诊断方法,系统地讨论了300 hPa北半球极涡面积、强度及中心位置的年际和年代际变化特征,结果表明:(1)年平均北极涡的面积在20世纪70年代中期之前在总的上升趋势中有几次较小的波动,之后在总体下降趋势中有几次较大的起伏;Ⅰ、Ⅱ区的线性变化趋势非常小,Ⅳ区最大,夏季的年际变化相对明显一些,秋季变化最弱,各季节均有线性收缩趋势,冬季幅度最大,秋季最小。(2)年平均极涡强度的年际、年代际变化特征与极涡面积有相似之处,但不同年份存在显著差异;各分区的强度变化与北半球类似(特别是Ⅰ区);夏季的年际变化幅度最大,春、夏季年代际变化的特征明显,秋季最弱。(3)北极涡中心位置通常并不在北极点,各分区极涡总面积所占的百分比有明显差异,且有月际变化,这些差异与海陆热力差异造成的环流的差异密切相关;极涡的主要位置有一定的年际、年代际变化特征;极涡中心位置主要偏向亚洲大陆及太平洋一侧。 相似文献
4.
Arctic sea ice and Eurasian climate: A review 总被引：12，自引：0，他引：12
GAO Yongqi SUN Jianqi LI Fei HE Shengping Stein SANDVEN YAN Qing ZHANG Zhongshi Katja LOHMANN Noel KEENLYSIDE Tore FUREVIK SUO Lingling 《大气科学进展》2015,32(1):92-114
The Arctic plays a fundamental role in the climate system and has shown significant climate change in recent decades,including the Arctic warming and decline of Arctic sea-ice extent and thickness. In contrast to the Arctic warming and reduction of Arctic sea ice, Europe, East Asia and North America have experienced anomalously cold conditions, with record snowfall during recent years. In this paper, we review current understanding of the sea-ice impacts on the Eurasian climate.Paleo, observational and modelling studies are covered to summarize several major themes, including: the variability of Arctic sea ice and its controls; the likely causes and apparent impacts of the Arctic sea-ice decline during the satellite era,as well as past and projected future impacts and trends; the links and feedback mechanisms between the Arctic sea ice and the Arctic Oscillation/North Atlantic Oscillation, the recent Eurasian cooling, winter atmospheric circulation, summer precipitation in East Asia, spring snowfall over Eurasia, East Asian winter monsoon, and midlatitude extreme weather; and the remote climate response(e.g., atmospheric circulation, air temperature) to changes in Arctic sea ice. We conclude with a brief summary and suggestions for future research. 相似文献
5.
Using monthly mean sea ice velocity data obtained from the International Arctic Buoy Programme (IABP) for the period of 1979–1998 and the monthly mean NCEP/NCAR re-analysis dataset (1960–2002), we investigated the spatiotemporal evolution of the leading sea ice motion mode (based on a complex correlation matrix constructed of normalized sea ice motion velocity) and their association with sea level pressure (SLP) and the predominant modes of surface wind field variability. The results indicate that the leadi... 相似文献
6.
Yutaka Ishizaka Peter V. Hobbs Lawrence F. Radke 《Journal of Atmospheric Chemistry》1989,9(1-3):149-159
Airborne measurements made during August 1985 over Greenland and its environs show that both accumulation-mode (0.1 m D2.0 m) and giant (D2 m) particles were present in relatively high concentrations in arctic haze layers and that the accumulation-mode particles dominated light scattering. Particles with diameters (D) between 1 and 4 m consisted predominately of mixed materials, small and dense inclusions, and probably organic compounds containing sulfur. Many of the particles from 0.1 to 1 m in diameter were also of mixed composition, with sulfuric acid, ammonium sulfate and organics probably the dominant constituents. 相似文献
7.
The second Arctic Gas and Aerosol Sampling Program (AGASP-II) was conducted across the non-Soviet Arctic in March and April 1986, to study the aerosol, gaseous, chemical, and optical properties of Arctic haze. One component of the program was supported with an instrumented NOAA WP-3D atmospheric research aircraft. Measurements of wind, temperature, ozone, water vapor, condensation nucleus concentration, and aerosol scattering extinction coefficient were used to determine the locations and properties of haze layers. The first three NOAA WP-3D research flights were conducted north of Barrow, Alaska, and over the Beaufort Sea northeast of Barter Island, Alaska. The next three sampled conditions in the high Arctic near Alert, Northwest Territories, Canada. All basic meteorological, gas, and aerosol systems are described. The WP-3D flight tracks and operations are presented. 相似文献
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G. E. Shaw 《Journal of Atmospheric Chemistry》1986,4(1):157-171
Results from measurements of the composition and size distribution of aerosol particles advected into central Alaska are reported. It is argued that the aerosol predominant in number, but not necessarily in mass, consists of submicron droplets of sulfuric acid. The major aerosol by mass in arctic air is a removal-resistant accumulation mode (radius 0.3 m) probably to large extent originating from pollution sources 103 km upstream (mostly in central Eurasia) from the site in Alaska. The accumulation mode aerosol disappears when arctic air masses are replaced with relatively warmer air masses flowing in from the northern Pacific. The latter air mass systems have been strongly scavenged by clouds and precipitation associated with the Aleutian low pressure system and with forced orographic uplifting over the Alaska Mountain Range; nevertheless the Pacific air masses contain substantial (i.e., 500–1000 cm-3) quantities of small (several hundredths of a micron in radius) particles. Arctic-derived air masses are enriched in large (i.e, 0.3 ) particles compared to Pacific Marine air masses, whereas the opposite trend is found for smaller, Aitken, particles. The smaller particles are found in greatest abundance in warmer air mass systems, presumably because of the relatively brief time since such air masses were last exposed to sunlight with attendant production of small particles from the gas phase. 相似文献
10.
Observations from the summer Arctic Ocean Experiment 2001 (AOE-2001) are analysed with a focus on the interactions between
mesoscale and boundary-layer dynamics. Wavelet analyses of surface-pressure variations show daylong periods with different
characteristics, some featuring episodes of pronounced high-frequency surface-pressure variability, here hypothesized to be
caused by trapped gravity waves. These episodes are accompanied by enhanced boundary-layer turbulence and an enhanced spectral
gap, but with only minor influence on the surface stress. During these episodes, mesoscale phenomena were often encountered
and usually identified as front-like features in the boundary layer, with a peak in drizzle followed by changing temperature.
These phenomena resemble synoptic fronts, though they are generally shallow, shorter-lasting, have no signs of frontal clouds,
and do not imply a change in air mass. Based on this analysis, we hypothesize that the root cause of the episodes with high-frequency
surface-pressure variance are shallow, mesoscale fronts moving across the pack ice. They may be formed due to local-to-regional
horizontal contrasts, for example, between air with different lifetimes over the Arctic or with perturbations in the cloud
field causing differential cooling of the boundary layer. Thermal contrasts sharpen as the air is transported with the mean
flow. The propagating mesoscale fronts excite gravity waves, which affect the boundary-layer turbulence and also seem to favour
entrainment of free tropospheric air into the boundary layer. 相似文献
11.
Airborne measurements of the emissions from natural fires, fueled by pyrites and organic materials, at the Smoking Hills in the Northwest Territories, show that they are a regionally significant source of SO2 (0.3 kg s–1 or 104 T yr–1) and particles (0.3 kg s–1). It appears likely that the Smoking Hills are a source for some of the dense, lower-level, haze layers that occur in the North American Arctic. 相似文献
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北极臭氧垂直分布和天气尺度变化的观测研究 总被引：2，自引：0，他引：2
北极地区臭氧对北极气候和环境系统起着重要作用。研究其分布和变化有助于了解北极的气候和环境及其对全球气候系统的影响,有助于气候和环境变化的数值预报。中国北极科学探测1999在北冰洋楚可奇海域成功的进行了大气臭氧观测。通过在中国“雪龙”号破冰船甲板上（于1999年8月18-24日在75°N,160°W附近处）释放大气臭氧探空仪获得了高分辨率的大气垂直结构和臭氧分布资料,可以进行大气尺度的大气臭氧变化研究。分析大气监测资料、TOMS臭氧总量资料和NCEP大气环流资料表明,大气臭氧总量随着对流层顶的低一高一低变化呈高一低一高的变化过程。研究还表明,大气柱的臭氧总量与13公里以下的大气臭氧含量关系密切,而在约20公里处的大气臭氧浓度最大值的变化与整个气柱臭氧的关系不大。500 hPa天气形势图上一个弱一强一弱的西南天气型造成的弱臭氧平流可能是这次臭氧变化的主要原因。 相似文献
14.
利用Hadley海冰密集度资料和NCEP/NCAR再分析资料,分析了北极海冰融冰量及其与大气变量年际关系的年代际变化。结果表明,北极海冰存在显著的年代际变化,且有较强的区域性。东西伯利亚海和波弗特海海冰融冰量的平均值变大且方差增大,格陵兰岛以东洋面海冰融冰量的量值和变率均在减弱。对3个不同气候时段内北极海冰融冰量进行EOF分解,前两个模态均在3个气候时段发生显著的年代际变化,东西伯利亚海海冰融冰量的增加与EOF第一模态年代际变化相关,而EOF第二模态则明显造成了波弗特海海冰的年代际消融。并且,与之相应的大气环流也出现了明显的年代际变化,它们与AO/NAO的年际关系也存在年代际转折,融冰量第二模态与AO的年际关系更为紧密,1960—1990年第二模态与AO的相关系数仅为0.186,而1980—2010年相关系数已升高至0.367。整个北冰洋的海冰融冰量与AO的年际关系也出现了年代际增强,尤其是东西伯利亚地区海冰融冰量与AO的年际关系发生了年代际增强,1980—2010年两者相关达到了0.4以上。而波弗特海融冰量与AO相关系数变化较大,1960—1990年其的相关系数高达-0.488,1980年后却减少至0.161。然而AO却未发生明显的年代际变化。造成北极海冰融冰量及其与大气变量年际关系发生年代际变化的主要因子之一是波弗特高压,其年代际减弱使得极区向东西伯利亚海和波弗特海的海冰输送减弱,导致这两个区域海冰减少,使得AO与北极海冰的年际关系发生了年代际转折。 相似文献
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The nature of the reduction trend and quasi-decadal oscillation in Northern Hemisphere sea-ice extent is investigated. The trend and oscillation that seem to be two separate phenomena have been found in data. This study examines a hypothesis that the Arctic sea-ice reduction trend in the last three decades amplified the quasi-decadal Arctic sea-ice oscillation (ASIO) due to a positive ice/ocean-albedo feedback, based on data analysis and a conceptual model proposed by Ikeda et al. The theoretical, conceptual model predicts that the quasi-decadal oscillation is amplified by the thinning sea-ice, leading to the ASIO, which is driven by the strong positive feedback between the atmosphere and ice-ocean systems. Such oscillation is predicted to be out-of-phase between the Arctic Basin and the Nordic Seas with a phase difference of 3/4, with the Nordic Seas leading the Arctic. The wavelet analysis of the sea ice data reveals that the quasi-decadal ASIO occurred actively since the 1970s following the trend starting in the 1960s (i.e., as sea-ice became thinner and thinner), as the atmosphere experienced quasi-decadal oscillations during the last century. The wavelet analysis also confirms the prediction of such out-of-phase feature between these two basins, which varied from 0.62 in 1960 to 0.25 in 1995. Furthermore, a coupled ice-ocean general circulation model (GCM) was used to simulate two scenarios, one without the greenhouse gas warming and the other having realistic atmospheric forcing along with the warming that leads to sea-ice reduction trend. The quasi-decadal ASIO is excited in the latter case compared to the no-warming case. The wavelet analyses of the simulated ice volume were also conducted to derive decadal ASIO and similar phase relationship between the Arctic Ocean and the Nordic Seas. An independent data source was used to confirm such decadal oscillation in the upper layer (or freshwater) thickness, which is consistent with the model simulation. A modified feedback loop for the sea-ice trend and ASIO was proposed based on the previous one by Mysak and Venegas and the ice/albedo and cloud/albedo feedabcks, which are responsible for the sea ice reduction trend. 相似文献
16.
Synoptic-scale atmospheric circulation patterns drive wind forcing of dynamic and thermodynamic processes in Arctic sea ice. Synoptic typing and compositing are common techniques used to identify a limited number of prevailing weather classifications that govern a region's climate. This work investigates atmospheric circulation patterns (surface to 250?hPa) for the southern Beaufort Sea and corresponding surface wind regimes within each synoptic type. Significant changes (p?<?0.05) in relative frequencies of a number of synoptic types were attributed to declining summer sea ice. Corresponding upper-level circulation anomalies show increasingly meridional atmospheric circulation. Synoptic Types 9 and 11 were identified as key October-November-December circulation features that represent deepening of the Aleutian low with concomitant strengthening of pressure gradients over the southern Beaufort Sea. Classification of coastal-based wind observations shows a shift towards increased easterly wind forcing. A case study of surface wind data from the CCGS Amundsen (2009–2011) provided a direct example of the surface wind regime within the marginal ice zone within each synoptic type during a period of reduced Arctic sea-ice cover. 相似文献
17.
Starting in mid-November,China was hit by several cold events during the early winter of 2020/21.The lowest temperature observed at Beijing station on 7 January reached?19.6°C.In this paper,we show that the outbreak of the record-breaking extreme cold event can be attributed to a huge merging Ural blocking(UB)ridge over the Eurasian region.The sea-ice cover in the Kara and East Siberia Seas(KESS)in autumn was at its lowest value since 1979,which could have served as a precursor signal.Further analysis shows that several successive UB episodes occurred from 1 September 2020 to 10 January 2021.The persistent UB that occurred in late September/early October 2020 may have made an important contribution to the October historical minimum of sea ice in the KESS region.Our results also show that,after each UB episode in winter,significant upward propagation of wave activity occurred around 60°E,which resulted in weakening the stratospheric vortex.Meanwhile,each UB episode also caused a significant reduction in sea-ice extent in KESS and a significant weakening of the westerly jet in mid-high-latitude Eurasia.Results suggest that the Arctic vortex,which is supposed to enhance seasonally,became weaker and more unstable than the climatic mean under the seasonal cumulative effects of UB episodes,KESS warming,and long-lasting negative-phase North Atlantic Oscillation(NAO-).Those seasonal cumulative effects,combined with the impact of La Ni?a winter,led to the frequent occurrence of extreme cold events. 相似文献
18.
Boundary-layer measurements made from the Swedish icebreaker Oden during the Arctic Ocean Experiment 2001 (AOE-2001) are analysed. They refer mainly to ice drift in the central Arctic during
the period 2–21 August 2001. On board Oden a remote sensing array with a wind profiler, cloud radar and a scanning microwave radiometer, and a regular weather station
operated continuously; soundings were also released during research stations. Turbulence and profile measurements on an 18-m
mast were deployed on the ice, along with two sodar systems, a microbarograph array and a tethered sounding system. Surface
flux and meteorological stations were also deployed on nearby ice floes. There is a clear diurnal cycle in radiation and also
in wind speed, cloud base and visibility. It is absent in temperature and humidity, probably due to the very strong control
by melting/ freezing ice and snow. In the advection of warm air, latent heat of melting maintains the surface temperature
at 0 °C, while with a negative energy balance the latent heat of freezing of the salty ocean water acts to maintain the surface
temperature > −2 °C. The constant presence of water at the surface maintains a relative humidity close to 100%, and this is
also often facilitated by an increasing specific humidity through the capping inversion, making entrainment a moisture source.
This ensures cloudy conditions, with low cloud and fog prevailing most of the time. Intrusions of warm and moist air from
beyond the ice edge are frequent, but the local Arctic boundary layer remains at a relatively constant temperature, and is
shallow and well mixed with strong capping inversions. Power spectra of surface-layer wind speed sometimes show large variance
at low frequency. A scanning radiometer provides a monitoring of the vertical thermal structure with a spatial and temporal
resolution not seen before in the Arctic. There are often two inversions, an elevated main inversion and a weak surface inversion,
and occasionally additional inversions occur. Enhanced entrainment across the main inversion appears to occur during frontal
passages. Variance of the scanning radiometer temperatures occurs in large pulses rather than varying smoothly, and the height
to the maximum variance appears to be a reasonable proxy for the boundary-layer depth. 相似文献
19.
Charles A. Brock Lawrence F. Radke Jamie H. Lyons Peter V. Hobbs 《Journal of Atmospheric Chemistry》1989,9(1-3):129-148
Airborne observations during August 1985 over Greenland and the North American Arctic revealed that dense, discrete haze layers were common above 850 mb. No such hazes were found near the surface in areas remote from local sources of particles. The haze layers aloft were characterized by large light-scattering coefficients due to dry particles (maximum value 1.24 × 10–4m–1) and relatively high total particle concentrations (maximum value 3100 cm–3). Sulfate was the dominant ionic component of the aerosol (0.06 – 1.9 g m–3); carbon soot was also present. Evidence for relatively fresh aerosols, accompanied by NO2 and O3 depletion, was found near, but not within, the haze layers. The hazes probably derived from anthropogenic sources and/or biomass burning at midlatitudes.It is hypothesized that the scavenging of particles by stratus clouds plays an important role in reducing the frequency and intensity of hazes at the surface in the Arctic in summer. Since the detection of haze layers aloft through measurements of column-integrated parameters from the surface (e.g., by lidar) cannot be carried out reliably when clouds are present, such measurements have likely underestimated the occurrence of haze layers in the Arctic, particularly in summer. 相似文献
20.
This study examined wintertime （November-April） cold wave frequency （CWF） in northern China during the last 42 years and its association with Arctic Oscillation （AO） through analysis of daily mean surface temperature from 280 stations across northern China and European Centre for Medium-Range Weather Forecasts （ECMWF） 40-Year Re-analysis ERA-40 data. The leading empirical orthogonal function EOF mode of wintertime CWF （CWF-EOF1） indicates an identical signal over most northern China, with the characteristic trend of linear decline for the leading principal component （CWF-PC1）. After the linear trend is removed, remarkable inter-annual variability is found to be the dominant feature of the CWF-PC1. The regression map for sea level pressure based on CWF-PC1 corresponds to the negative phase of AO. Correlation analysis further proves that CWF-PC1 has a significant negative correlation with AO at the inter-annual time scale. The relationship between AO and global surface air temperature is also investigated in order to understand its association with cold air activity over East Asia, and it is suggested that the anomalies of atmospheric circulation in Siberia may serve as a bridge for interaction between AO and CWF in northern China during wintertime. 相似文献