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1.
Summary Distributions through the year of temperature, geopotential height and specific humidity, and of their standard deviations, over southern African radiosonde stations are studied through harmonic analysis. Characteristics of annual and semi-annual cycles vary across the subcontinent as a result of thermal and mechanical effects induced by the land mass. Over the interior plateau temperatures and geopotential heights through to 100 hPa respond directly to solar heating of the surface and resultant seasonal changes in surface-at-mosphere heat fluxes. Around the coast temperatures and geopotential heights are additionally influenced by seasonally-varying ocean-atmosphere heat fluxes. Cycles of atmospheric moisture are dependent on properties of the low-level circulation rather than on temperature per se. The results demarcate the two inversions frequently located over the subcontinent and indicate that the local subtropical jet stream is displaced latitudinally on a semi-annual cycle, lying furthest south in February and August.With 12 Figures  相似文献   

2.
An unusual heavy coastal rainfall event (>231?mm?day?1) occurred during the period of 24?C25 June 1987 over the lowland (elevation less than 200?m) and coastal areas in northwest and central Taiwan. The Weather Research and Forecasting (WRF) model is used to investigate the role of synoptic forcing, orographic effects and the diurnal heating cycle on the generation of a prefrontal localized low-level convergence zone offshore leading to the observed coastal rainfall maximum. This case is well simulated by the control experiment initialized at 0000 UTC (0800 LST) 24 June 1987 using the European Centre for Medium-Range Weather Forecasts data. A model sensitivity test without Taiwan??s terrain fails to reproduce the observed coastal rainfall maximum. It is apparent that for this case, synoptic forcing by the Mei-Yu jet/front system is inadequate to initiate deep convection leading to the development of coastal heavy precipitation. The generation of the localized low-level convergence zone is closely related to the simulated strong winds with a large southwesterly wind component (or the barrier jet) along the northwestern coast as the surface front approaches. The development of the simulated barrier jet is due to a 50?C60% increase in the meridional pressure gradient as a result of orographic blocking. The diurnal heating cycle also impacts the strength of the simulated barrier jet over the northwestern Taiwan coast. The simulated barrier jet is stronger (~3?m?s?1) in the early morning than in the afternoon as orographic blocking is most significant when the surface air is the coldest. The representation of the terrain in the model impacts the simulated barrier jet and rainfall. With a coarse horizontal resolution (45?km), orographic blocking is less significant than the control run with a much weaker meridional wind component over the northwestern coast of Taiwan. The coarse resolution model fails to reproduce the observed rainband off the northwestern coast. Thus, to successfully simulate this type of event, high-resolution mesoscale models adequately depicting Taiwan??s terrain are required.  相似文献   

3.
Moisture exchange between the South Atlantic and southern Africa is examined in this study through zonal moisture transport. Along the west coast of southern Africa, a multivariate analysis of the zonal flow of moisture computed from NCEP-DOE AMIP II Re-analyses reveals a primary mode of variability typical of variations in intensity and of the latitudinal migration of the circulation associated with the midlatitude westerlies and the South Atlantic anticyclone. In austral summer (January–February), this mode, referred to as the South Atlantic midlatitude mode, is found to be well correlated with rainfall over southern Africa (i.e. to the south of the upper lands surrounding the Congo basin). Its positive/negative phases are found to correspond with surface pressures changes over the South Atlantic region in austral summer when the South Atlantic anticyclone is shifted northward/southward respectively. Such changes are accompanied by dipole-like SST anomalies in the midlatitude South Atlantic Ocean, while simultaneous SST anomalies with a similar structure are also found over South Indian Ocean regions. In January–February, positive/negative events linked to the South Atlantic midlatitude mode are marked by meridional shifts (northward/southward) and weakening/strengthening of the ITCZ over the southern tropics, together with modulations in intensity (weakened/sustained) of the Angola low, which could act as a tropical source of moisture for Tropical Temperate Troughs (TTTs). In association with a strengthened/weakened zonal component of the southern extension of the African Easterly Jet (AEJ), this could modulate the meridional transfer of moisture south of 15°S to the advantage/detriment of Angolan coastal regions, where above/below rainfall are expected. Variations in the latitudinal position (northward/southward) of the South Atlantic anticyclone, and thus of the midlatitude westerlies, are also found to reduce/favour moisture advection towards southern Africa subtropics allowing the southern Indian trades to penetrate less/more over the subcontinent south of 25°S. This would create a situation where convection processes are inhibited/supported within the SICZ/TTTs region resulting in drier/wetter conditions locally for positive/negative events respectively.  相似文献   

4.
An empirical orthogonal functions analysis of the onshore flow of moisture along the west coast of southern Africa using NCEP-DOE AMIP II Re-analyses suggests two dominant modes of variability that are linked to (a) variations in the circulation linked with the South Atlantic anticyclone (b) the intensity of the flow that penetrates from the tropical Atlantic. The second mode, referred as the Equatorial Westerly mode, contributes the most to moisture input from the Atlantic onto the subcontinent at tropical latitudes. Substantial correlations in austral summer between the Atlantic moisture flux in the tropics and rainfall over the upper lands surrounding the Congo basin suggest the potential role played by this zonal mode of water vapour transport. Composites for austral summer months when this Equatorial Westerly mode had a particularly strong expression, show an enhanced moisture input at tropical latitudes that feeds into the deep convection occurring over the Congo basin. Sustained meridional energy fluxes result in above normal rainfall east and south of the Congo belt. During years of reduced equatorial westerly moisture flux, a deficit of available humidity occurs in the southern tropics. A concomitant eastward shift of deep convection to the southwest Indian ocean and southeastern Africa, leads to below normal rainfall over the uplands surrounding the Congo basin.  相似文献   

5.
A quantitative diagnosis is carried out for the upward branch of a local meridional circulation over southern China(SC) during the abnormal snowstorms with severe freezing rain from 10 January to 3 February 2008.The diagnostic study shows that the upward branch is mainly associated with the zonal advection of westerly momentum and meridional temperature advection instead of the latent heating(which is commonly the dominant factor in many other storm cases).The corresponding weather analyses indicate that(1) the zonal advection of westerly momentum represents the effect of the upper-level divergence on the anticyclone-shear side in the entrance of a 200 hPa westerly jet with a westward deviation from its climatological location over southwestern Japan;(2) the meridional temperature advection represents the interaction between the mid-lower layer(850 to 400 hPa) warm advection over SC(ahead of temperature and pressure troughs with the latter trough deeper than the former in the Bay of Bengal) and cold advection over north China(steered by an underlying flow at 500 hPa);(3) the relatively weak vapor transport(compared to that of spring,summer and autumn) from the Bay of Bengal and the South China Sea to SC and the existence of a temperature inversion layer in the lower troposphere over SC diminish the effect of latent heating.With the significant increase of vapor transport after 24 January,the role of latent heating is upgraded to become the third positive contributor to the upward branch over SC.  相似文献   

6.
T. Zhou  Z. Li 《Climate Dynamics》2002,19(2):167-180
The East Asia summer monsoon (EASM) is simulated with a variable resolution global atmospheric general circulation model (GCM) developed at the Laboratoire de Météorologie Dynamique, France. The version used has a local zoom centered on China. This study validates the model's capability in reproducing the fundamental features of the EASM. The monsoon behaviors over East Asia revealed by the ECMWF reanalysis data are also addressed systematically, providing as observational evidence. The mean state of the EASM is generally portrayed well in the model, including the large-scale monsoon airflows, the monsoonal meridional circulation, the cross-equatorial low-level jets, the monsoon trough in the South China Sea, the surface cold high in Australia, and the upper-level northeasterly return flow. While the performance of simulating large-scale monsoonal climate is encouraging, the model's main deficiency lies in the rainfall. The marked rainbelt observed along the Yangtze River Valley is missed in the simulation. This is due to the weakly reproduced monsoonal components in essence and is directly related to the weak western Pacific subtropical high, which leads to a fragile subtropical southwest monsoon on its western flank and results in a weaker convergence of the southwest monsoon flow with the midlatitude westerlies. The excessively westward extension of the high, together with the distorted Indian low, also makes the contribution of the tropical southwest monsoon to the moisture convergence over the Yangtze River Valley too weak in the model. The insufficient plateau heating and the resulting weak land-sea thermal contrast are responsible for the weakly reproduced monsoon. It is the deficiency of the model in handling the low-level cloud cover over the plateau rather than the horizontal resolution and the associated depiction of plateau topography that results in the insufficient plateau heating. Comparison with the simulation employing regular coarser mesh model reveals that the local zoom technique improves, in a general manner, the EASM simulation.  相似文献   

7.
A simultaneous glaciochemical study of methanesulfonic acid (MSA) and non-sea-salt sulfate (nss-SO4 -) has been conducted on the Antarctic plateau (South Pole, Vostok) and in more coastal regions. The objective was to investigate marine sulfur emissions in very remote areas. Firstly, our data suggest that MSA and nss-SO4 present in antarctic ice are mainly marine in origin and that DMS emissions have been significantly modulated by short term (eg. El Nino Southern Oscillation events) as well as long term climatic changes in the past. Secondly, our study of spatial variations of these two sulfur species seems to indicate that the atmosphere of coastal antarctic regions are mainly supplied by local DMS emissions whereas the atmosphere of the high plateau is also influenced by DMS emissions from more temperate marine latitudes. Thirdly, our study of the partitioning between MSA and nss-SO4 suggest that the temperature could have been an important parameter controlling the final composition of the high southern latitude atmosphere over the last climatic cycle; colder temperature favoring the formation of MSA. However, our data also support a possible role played by changes in the transport pattern of marine air to the high antarctic plateau.  相似文献   

8.
基于1982—2013年逐月NCEP资料及GODAS资料,采用回归分析、合成分析以及2.5层简化海洋模式数值模拟等方法,研究了热带东印度洋的大气和海洋过程对印度洋海温偶极子(IOD,Indian Ocean Dipole)东极(IODE,IOD East pole)海温异常的影响。结果表明,IODE海温异常的演变超前IOD西极(IODW,IOD West pole)海温异常的演变,并对IOD事件的生成和发展起到关键作用。初夏,来自阿拉伯海、中南半岛地区以及孟加拉湾西南部的水汽输送,导致孟加拉湾东部出现强降水。降水释放的潜热在热带东印度形成了一个跨越赤道的经向环流,有利于加强赤道东印度洋的过赤道气流,并在苏门答腊沿岸形成偏南风异常。该异常偏南风通过影响混合层垂向夹卷混合过程和纬向平流过程,导致IODE海温迅速下降。随后赤道东南印度洋异常东南风迅速增强以及赤道中印度洋东风异常的出现,增强了自东南印度洋向西印度洋的水汽输送,削弱了向孟加拉湾的水汽输送,使西南印度洋的降水增强,孟加拉湾东部的降水减弱。因此,IOD达到盛期前孟加拉湾东部的降水通过局地经向环流在苏门答腊沿岸形成偏南风异常,导致苏门答腊沿岸迅速的降温,并最终导致IOD事件的发生。  相似文献   

9.
We report results of preliminary high-resolution in situ atmospheric measurements through the boundary layer and lower atmosphere over the southern coast of Perú. This region of the coast is of particular interest because it lies adjacent to the northern coastal edge of the sub-tropical south-eastern Pacific, a very large area of ocean having a persistent stratus deck located just below the marine boundary layer (MBL) inversion. Typically, the boundary layer in this region during winter is topped by a quasi-permanent, well-defined, and very large temperature gradient. The data presented herein examine fine-scale details of the coastal atmosphere at a point where the edge of this MBL extends over the coastline as a result of persistent onshore flow. Atmospheric data were gathered using a recently-developed in-house constructed, GPS-controlled, micro-autonomous-vehicle aircraft (the DataHawk). Measured quantities include high-resolution profiles of temperature, wind, and turbulence structure from the surface to 1,300 m.  相似文献   

10.
On interannual time scales, quasi-cyclic activity in the troposphere is generally thought to arise from chaotic feedback processes, and therefore to be unpredictable in nature. Here, evidence is presented for periodic ??clockwork?? climate behavior, seen as a stable quasi-biennial (QB) oscillation in Western US winter precipitation, estimated at a period of 2.16?±?~0.05?years. In the Western US, the QB precipitation mode has an influence comparable to that of ENSO, with strongest effects observed at central latitudes of the region. The oscillation displays systematic phase-shifting with respect to the annual cycle, signifying a stable, nonseasonal and strongly periodic QB mechanism. The cycle in precipitation results proximally from a meridional standing pressure wave over the North American Pacific coast. Analysis of monthly pressure data confirms the nonseasonal, periodic character of the oscillation, which appears to have maintained phase from the mid-20th century to recent years. The regional QB pressure cycle is traced to a quasi-synchronous pulsation of meridional pressure waves in the extratropics of both hemispheres, termed a Biennial Annular Mode Oscillation (BAMO). The BAMO oscillates in quadrature with a weaker ~26-month signal in the tropical Southern Oscillation. Due to a shorter period, both oscillations operate independently of the stratospheric Quasi-biennial Oscillation (QBO).  相似文献   

11.
The adjustment of airflow across sea-surface temperature changes is examinedusing aircraft eddy-correlation data. Major features of the observed flow adjustmentare not included in the theory of internal boundary layers. However, the data samplesize and coverage are not sufficient to accurately quantify the additional influences.With flow from warm water over cooler water, substantial turbulence intermittentlydevelops above the newly formed surface inversion layer. The corresponding,spatially-averaged, downward momentum flux is stronger than that close to the surface.With stably stratified flow over modest increases of sea-surface temperature, areduction of stratification can trigger episodic shear generation of turbulence. Inthese cases, the primary role of increasing surface temperature in the downwinddirection is to induce shear generation of turbulence. With larger increases ofsurface temperature, upward heat flux generates turbulence, warms the air and generates a significant horizontal gradient of hydrostatic pressure. This contributionto the pressure field appears to strongly modify the flow. Major inadequacies inexisting data and future needs are noted.  相似文献   

12.
利用NCEP逐日再分析资料、Micaps系统提供的气象观测资料及局地经向环流线性诊断模式，定量分析了2003年夏季东亚地区局地经向环流的演变情况。结果表明：(1)东亚地区夏季雨带的移动与局地经向环流的演变紧密联系。当淮河流域发生强降水时，在淮河流域上升和华南地区下沉的副热带季风环流圈尤为显著，该环流圈主要由潜热加热、热量垂直输送、温度平流和西风动量经向输送等物理因子所驱动；(2)潜热加热主要影响副热带季风环流上升支的强度，反映了梅雨锋对流系统的重要作用；(3)热量垂直输送、温度平流及西风动量经向输送则主要影响副热带季风环流上升支的北移，其中热量垂直输送、与强(弱)斜压槽活动有关的经向温度平流和涡动西风动量经向输送(纬向温度平流和平均西风动量经向输送)对上升支北移的作用在华南地区汛期后期(在其余夏季降水阶段)较突出。以上这些物理因子具有预报东亚地区局地经向环流演变和雨带移动的参考价值。  相似文献   

13.
The boundary currents over the Western Australian continental shelf and slope consist of the poleward flowing Leeuwin Current (LC) and the equatorward flowing Leeuwin Undercurrent (LUC). Key properties of the LC are its poleward strengthening, deepening to the south, and shelfbreak intensification. The alongshore flow reverses direction below about 300 m, forming the LUC at greater depths. To investigate the processes that cause these features, we obtain solutions to an idealized, regional ocean model of the South Indian Ocean. Solutions are forced by relaxing surface density to a prescribed, meridionally varying density profile ρ*(y) with a timescale of δt. In addition, vertical diffusion is intensified near the ocean surface. This diffusion establishes the minimum thickness over which density is well-mixed. We define this thickness as the “upper layer”. Solutions are obtained with and without a continental shelf and slope off Western Australia and for a range of values of δt and mixing parameters. Within this upper layer, there is a meridional density gradient that balances a near-surface, eastward geostrophic flow. The eastward current downwells near the eastern boundary, leading to westward flow at depth. The upper layer's meridional structure and zonal currents crucially depend on coastal processes, including the presence of topography near the eastern boundary. Kelvin waves inhibit the upper layer from deepening at the coast. Rossby waves propagate the coastal density structure offshore, hence modifying the interior currents. A comparison of the solutions with or without a continental shelf and slope demonstrate that topographic trapping of Rossby waves is a necessary process for maintaining realistic eastern boundary current speeds. Significant poleward speeds occur only onshore of where the upper layer intersects the slope, that is, at a grounding line. Its poleward transport increases when surface-enhanced vertical mixing is applied over a greater depth. When the timescale δt is sufficiently short, the poleward current is nearly barotropic. The current's spatial structure over the shelf is controlled by horizontal mixing, having the structure of a Munk layer. Increasing vertical diffusion deepens the upper layer thickness and strengthens the alongshore current speed. Bottom drag leads to an offshore flow along the bottom, reducing the net onshore transport and weakening the current's poleward acceleration. When δt is long, poleward advection of buoyancy forms a density front near the shelf break, intensifying poleward speeds near the surface. With bottom drag, a bottom Ekman flow advects density offshore, shifting the jet core offshore of the shelf break. The resulting cross-shelf density gradient reverses the meridional current's direction at depth, leading to an equatorward undercurrent.  相似文献   

14.
OBSERVATION AND ANALYSIS OF SEA SURFACE WIND OVER THE QIONGZHOU STRAIT   总被引：1，自引：1，他引：0  
The spatial variation and diurnal fluctuation of sea surface wind over the Qiongzhou Strait were described using verified datasets from automatic weather stations on board a ferry, buoys, and on the coast. Results are as follows: (1) On average, sea surface wind speed is 3–4 m/s larger over the Qiongzhou Strait than in the coastal area. Sea surface wind speeds of 8.0 m/s or above (on Beaufort scale five) in the coastal area are associated with speeds 5–6 m/s greater over the surface of the Qiongzhou Strait. (2) Gust coefficients for the Qiongzhou Strait decrease along with increasing wind speeds. When coastal wind speed is less than scale five, the average gust coefficient over the sea surface is between 1.4 and 1.5; when wind speed is equal to scale five or above, the average gust coefficient is about 1.35. (3) In autumn and winter, the diurnal differences of average wind speed and wind consistency over the strait are less than those in the coastal area; when wind speed is 10.8 m/s (scale six) or above, the diurnal difference of average wind speed decreases while wind consistency increases for both the strait and the coast.  相似文献   

15.
Biases in AMIP model simulations of the east China monsoon system   总被引：6，自引：0，他引：6  
 AMIP model simulations of the east China (5–50°N; 105–122°E) monsoon system are analyzed to study coherent relationships between rainfall and wind annual cycle biases. A comparison with observed interannual variability patterns is carried out to identify the physical processes that explain the biases. The analyses show that poleward displacement of the simulated east Asian jet stream causes the ascending branch of the jet-induced transverse circulation to move north and, as a consequence, produces negative (positive) rainfall biases occur in central (northeast) China. The model simulations show decreased southwesterly flow and ITCZ rainfall over the South China Sea when weaker (versus observations) summer Hadley and Walker circulations are present. This results from diminished model tropical disturbance activity, and highlights the importance of air-sea interactions. In addition, during October–January, intensified model low-level easterlies enhance moisture transport and produce positive local rainfall biases over central and northeast China. Biases in the east China monsoon system are concurrently reflected in the planetary circulation. Enhanced northeast China rainfall results from increased surface pressure over the North Pacific and an amplified zonal pressure gradient along the east China coast. This bias pattern is associated with differences in model representations of topography. On the other hand, the South China Sea experiences an extensive elongated meridional rainfall bias dipole structure that straddles the equator. This is accompanied by a baroclinic vertical pattern over the tropics as well as a barotropic wave train that extends from Australia to the Antarctic, where the teleconnection is likely a direct atmospheric response to tropical convective heating. Received: 20 June 2000 / Accepted: 17 September 2000  相似文献   

16.
基于JRA55再分析资料、观测的降水量和海表温度等数据,利用统计诊断方法分析了华南冬季气候准静止锋的主要变异特征,并探讨了其与环流、海温及东亚气候的联系。华南冬季气候准静止锋的主要变异模态表现为强度变异模态和经向位置变异模态,它们以年际变化为主。类东部型ENSO海温异常及热带中西印度洋海温异常对华南准静止锋强度的年际变异有显著影响;而类中部型ENSO海温异常型显著影响着华南气候准静止锋的南北位置。华南冬季准静止锋的强度变异对东亚副热带地区的降水、以及我国东部内陆地区的近地面气温有显著影响;华南冬季准静止锋南北位置变异则显著影响我国江淮流域降水、以及我国华南至东南沿海一带的近地面气温。华南冬季准静止锋的强度变异模态对东亚的降水和近地面气温的影响范围较位置变异模态都要大。  相似文献   

17.
Summary The Southerly Change Experiment (SOUCHEX) was conducted to examine the influence of the New Zealand Southern Alps on the structure and evolution of cold fronts, locally called southerly changes, as they travel up the east coast. The extensive data obtained by the augmented surface weather station network is used to examine in detail the mesoscale wind field associated with the events observed during the experiment. A comparison of the wind fields observed during the different events illustrates the influence of local dynamic and thermal factors. In particular, lee trough-induced northeasterlies and thermally developed diurnal wind systems are seen to interact with the wind field created by the passage of the front over the Southern Alps.It is apparent that the wind field associated with southerly changes responds to a variety of factors as the cold fronts propagate northwards. For example, there is a tendency for the flow to turn onshore producing a southeast wind during daytime over the Canterbury Plains south of Banks Peninsula probably due to diabatic heating of the mountains and plains. This onshore flow is in direct opposition to pre-frontal foehn northwesterly flow which often continues in the mountain regions and aloft after the front has moved up the coast. The interaction of these air masses over Canterbury creates difficulties for local forecasting. Also, the nocturnal passage of a southerly change is often difficult to detect in surface anemograph traces because of the decoupling of the boundary layer air from that above, producing low level drainage flow over the Canterbury Plains. The overall effect is to create a complex mesoscale wind field resulting from interaction of cold fronts with regional orographic and thermal influences.With 8 Figures  相似文献   

18.
Characteristics of the winter boundary layer over the (elevation 1600 m) in the vicinity of Johannesburg, 26 ° S, 29 ° E, are described in relation to air pollution potential by means of doppler sounder observations and background climatological data. Regional mean winds for the 800 h Pa level show that the winter boundary layer is dominated by a cell of high pressure over the Limpopo River Valley to the northeast of Johannesburg. To the south of Johannesburg, westerly circumpolar flow is prevalent and encroaches onto the plateau during the passage of frontal perturbations. Doppler sounder wind and turbulence profiles, averaged for the months of August 1984 and June 1985, are presented to establish a boundary-layer climatology. Diurnally averaged doppler sounder profiles for both months revealed a very consistent convective/day — stable/night cycle in the very dry winter conditions. A sharp radiation inversion formed just after sunset up to the 150–200 m level and grew in depth to reach 300 m on average near sunrise. The inversion caused a reduction in frictional drag and the formation of nocturnal low level jet during westerly encroachment. A case study is evaluated to determine the detailed structure of the low level jet near Johannesburg. The thermal wind plays a role in the nocturnal acceleration; mechanisms for its development and maintenance are explored. Additional work is presented on the synoptic cycle and its influence on air pollution dispersion over the African Plateau.  相似文献   

19.
Abstract

A numerical model, the Parallel Ocean Program (POP) was used to run a 46-year simulation of the North Pacific Ocean beginning in January 1960. The model had a horizontal resolution of 0.25°, 28 vertical levels, and employed spectral nudging that, unlike standard nudging, nudges only specific frequency and wavenumber bands. This simulation was nudged to the mean and monthly Levitus climatology of potential temperature and absolute salinity (SA). The model was forced with the mean monthly winds, sea level pressure, net heat flux, and precipitation from the National Centers for Environmental Prediction (NCEP).

The simulation was used to examine the anomalous intrusions, previously observed from 2001 to 2002, of cooler and fresher (less spicy) water flowing southward along the coast of western North America. The simulated anomaly began in 1999 in the North Pacific, progressed southeastward towards the coast and then southward, at least as far south as southern California. The southward velocity signal, modulated by a strong annual cycle, reached Point Conception in 2000 while the temperature and SA anomalies arrived later, in 2002–03. The simulated velocity anomalies were eastward at about 3?cm s?1 in the northeast Pacific near 47°N in agreement with observations. Simulated coastal southward flow speeds reached 10–20?cm s?1 during the summer from 2000 to 2002.

This intrusion was by far the largest to occur over the entire length of the simulation. It was also the only time during the simulation when the Victoria mode was positive (associated with enhanced flow to the east via the North Pacific Gyre Oscillation (NPGO)) and the Multivariate El Niño-Southern Oscillation (ENSO) Index (MEI) was negative (La Niña conditions), tending to cause a southward flow anomaly along the coast.  相似文献   

20.
Stable isotopes in water have been measured along a very high accumulation ice core from Law Dome on the east Antarctic coast. These enable a detailed comparison of the isotopic records over sixty years (1934–1992) with local (Antarctic station data) and remote meteorological observations (atmospheric reanalyses and sea-surface temperature estimates) on a seasonal to inter-annual time scale. Using both observations and isotopic atmospheric general circulation model (GCM) results, we quantify the relationships between stable isotopes (d 18O, dD and deuterium excess; d = dD –8 × d 18O) with site and source temperature at seasonal and decadal time scales, showing the large imprint of source conditions on Law Dome isotopes. These calibrations provide new insights for the quantitative interpretation of temporal isotopic fluctuations from coastal Antarctic ice cores. An abrupt change in the local meridional atmospheric circulation is clearly identified from Law Dome deuterium excess during the 1970s and analysed using GCM simulations.  相似文献   

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