orographic influences on the distribution and generation of atmospheric variability in a gcm abstract the effect of large scale mountains on atmospheric variability is studied in a series of gcm experiments in which a single mountain is varied in height from 0 to 4 km high frequency 30 days variability are largest in the jet exit region while the intermediate frequency 7 30 days variability has its maximum upstream of the mountain where it exhibits enhanced equatorward propagation high and intermediate frequencies change from zonal wave trains to localized wave packets as orographic forcing is increased but they retain their characteristic scale and frequency the dominant pattern of low frequency is variability changes from a zonally symmetric oscillation for which transient eddy zonal flow interaction is the dominant mechanism to a more localized oscillation of the jet downstream of the mountain the transient eddy forcing still plays a significant role in maintaining the variations of this more localized jet however the total amount of wave

a regime view of northern hemisphere atmospheric variability and change under global warming the leading mode of wintertime variability in northern hemisphere sea level pressure slp is the arctic oscillation ao it is usually obtained using linear principal component analysis which produces the optimal although somewhat restrictive linear approximation to the slp data here we use a recently introduced nonlinear principal component analysis to find the optimal nonlinear approximation to slp data produced by a 1001 year integration of the cccma coupled general circulation model cgcm1 this approximation s associated time series is strongly bimodal and partitions the data into two distinct regimes the first and more persistent regime describes a standing oscillation whose signature in the mid troposphere is alternating amplification and attenuation of the climatological ridge over northern europe with associated decreasing and increasing daily variance over northern eurasia the second and more episodic regime describes a split flow south of greenland with much enhanced daily variance in the arctic in a 500 year integration with atmospheric co2 stabilized at concentrations projected for year 2100 the occupation statistics of these preferred modes of variability change such that the episodic split flow regime occurs less frequently while the standing oscillation regime occurs more frequently

timescale dependency of spatial patterns in the variability of the northern hemisphere winter slp field 1 the arctic oscillation ao the north atlantic oscillation nao and the cold ocean warm land pattern cowl have been identified as important modes of variability in the northern hemisphere winter sea level pressure field however which one is most fundamental in describing this variability and the relationship between them are still important open questions a key uncertainty is our lack of knowledge of the linkages between the arctic north atlantic and north pacific oceans that are manifest in these modes in this study the authors investigate these linkages through a frequency dependent decomposition of the variability in the northern hemisphere sea level pressure field in particular the authors show that the spatial expression of the variability in this field has a frequency dependence that results in a nao like pattern on inter annual timescales an ao like pattern on inter decadal timescales and a cowl like pattern on multi decadal timescales

an andosol cambisol toposequence on granite in the austrian bohemian massif in europe non allophanic andosols are linked with hercynian basic and metabasic rocks in smoothed highlands with a cool and humid climate we describe an andosol cambisol toposequence derived from variscan coarse grained granite in northern austria bohemian massif where andosols have formed on plateaus and cambisols on steep slopes the climate is continental cool and humid mean annual temperature and rainfall 5 4 degreesc and 914 mm with a 100 day mean annual period of snow cover the forest is dominated by beech and spruce trees both soils are rich in organic matter and strongly acidic but the andosol is more strongly weathered than the cambisol below the 15 cm thick litter in the andosol the 38 cm thick ab bw solum is dark reddish brown to strong brown has a large c content 9 0 4 4 and meets all the requirements of an andic horizon in these horizons oxalate extractable iron content 1 62 8 fe o represents 76 84 of free iron and is much larger than al o 0 8 1 5 both biotite and plagioclase are sources of fe and al the fort nation of non allophanic andosol from granite was likely due to the combination of the following factors cool and humid climate large accumulation of organic matter high infiltration rate intense water percolation during spring thawing and significant content of weatherable minerals as such conditions are not rare in european highlands andic soils are probably more widespread in europe than is currently thought c 2003 elsevier b v all rights reserved

on the zonal structure of the north atlantic oscillation and annular modes abstract the zonal structure and dynamics of the dipolar patterns of intraseasonal variability in the extratropical atmosphere namely the north atlantic oscillation nao and the so called annular modes of variability are investigated in an idealized general circulation model particular attention is focused on the relationships linking the zonal structure of the stationary waves synoptic variability i e the storm tracks and the zonal structure of the patterns of intraseasonal variability large scale topography and diabatic anomalies are introduced to modify and concentrate the synoptic variability establishing a recipe for a localized storm track comparison of the large scale forcing synoptic variability and patterns of intraseasonal variability suggests a nonlinear relationship between the large scale forcing and the variability it is found that localized nao like patterns arise from the confluence of topographic and diabatic forcing and that the patterns are more localized than one would e

gap filling of missing data for viirs global ocean color products using the dineof method ocean color data are critical for the monitoring and understanding of biological and ecological processes and phenomena and the data are also important sources of input data for physical and biogeochemical ocean models the visible infrared imaging radiometer suite viirs onboard the suomi national polar orbiting partnership has continued to provide global ocean color data since its launch in october 2011 however there are always many missing pixels in the original viirs measured ocean color images due to clouds and various other reasons the data interpolating empirical orthogonal functions dineof is a method to reconstruct gap filling missing data in geophysical data sets based on the empirical orthogonal function in this paper the dineof is applied to viirs derived global level 3 binned ocean color data of 9 km spatial resolution and the dineof reconstructed ocean color data are used to fill the gaps of missing data in particular daily eight day and monthly viirs global level 3 binned ocean color data including chlorophyll a concentration diffuse attenuation coefficient at 490 nm k d 490 and normalized water leaving radiance spectra nl w lambda at the five viirs visible bands are tested and evaluated to validate and evaluate the gap filled data a set of original valid nonmissing pixels in the viirs images are selected randomly and treated as missing pixels in the dineof process so that the reconstructed pixels can be compared with the original data results show that the dineof method can successfully reconstruct and gap fill meso scale and large scale spatial ocean features in the global viirs level 3 images as well as capture the temporal variations of these features

comparison of quantification methods to measure fire derived black elemental carbon in soils and sediments using reference materials from soil water sediment and the atmosphere black carbon bc the product of incomplete combustion of fossil fuels and biomass called elemental carbon ec in atmospheric sciences was quantified in 12 different materials by 17 laboratories from different disciplines using seven different methods the materials were divided into three classes 1 potentially interfering materials 2 laboratory produced bc rich materials and 3 bc containing environmental matrices from soil water sediment and atmosphere this is the first comprehensive intercomparison of this type multimethod multilab and multisample focusing mainly on methods used for soil and sediment bc studies results for the potentially interfering materials which by definition contained no fire derived organic carbon highlighted situations where individual methods may overestimate bc concentrations results for the bc rich materials one soot and two chars showed that some of the methods identified most of the carbon in all three materials as bc whereas other methods identified only soot carbon as bc the different methods also gave widely different bc contents for the environmental matrices however these variations could be understood in the light of the findings for the other two groups of materials i e that some methods incorrectly identify non bc carbon as bc and that the detection efficiency of each technique varies across the bc continuum we found that atmospheric bc quantification methods are not ideal for soil and sediment studies as in their methodology these incorporate the definition of bc as light absorbing material irrespective of its origin leading to biases when applied to terrestrial and sedimentary materials this study shows that any attempt to merge data generated via different methods must consider the different operationally defined analytical windows of the bc continuum detected by each technique as well as the limitations and potential biases of each technique a major goal of this ring trial was to provide a basis on which to choose between the different bc quantification methods in soil and sediment studies in this paper we summarize the advantages and disadvantages of each method in future studies we strongly recommend the evaluation of all methods analyzing for bc in soils and sediments against the set of bc reference materials analyzed here

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

satellite detection of an unusual intrusion of salty slope water into a marginal sea using smap to monitor gulf of maine inflows abstract satellite salinity from the soil moisture active passive smap mission and in situ observations are used to diagnose the source of a significant increase in warm and salty surface water entering the gulf of maine gom in the winter of 2017 2018 smap salinity anomaly data indicate that this event was related to a salty feature that moved along the northwestern atlantic shelf break from near the grand banks southwest towards the gom over eight months before entering the gulf in december 2017 to january 2018 satellite altimetry sea surface salinity and sea surface temperature data suggest that before entering the gom the salty feature interacted with gulf stream meanders and eddies several times helping to sustain the water mass it is likely that feature interactions with a warm gulf stream meander took place in the fall of 2017 helping to advect high salinity water onto the shelf and then into the gom as a surface trapped feature in late fall 2017 according to satellite salinity data this episode led to significant salinification about 1 psu in the northeastern gom interior gom buoy salinity data agree in showing four months of increased gom salinity of the upper 50 m starting in november 2017 buoy t s analyses characterize this surface inflow as modified warm atlantic slope water typically seen only below 100 m and previously unobserved at the surface in the 15 year buoy record this new salty water circulated cyclonically along the gom coastline and mixed into the deeper gulf through february 2018 its intrusion may have also enhanced the cyclonic winter circulation in the gulf gom surface salinity anomalies ended abruptly in early march 2018 coincident with the occurrence of a bomb cyclone and its associated strong upper ocean mixing

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

frequency of ring separations from the loop current in the gulf of mexico a revised estimate the most energetic events in the circulation of the gulf of mexico are the separation of large anticyclonic rings from the loop current building on previous work the authors examine all the apparent rings since july 1973 this new dataset includes the satellite altimetry since 1992 providing a set of 34 consecutive ring formations the primary advantage of altimetry is that the data remain available in the summer one finding is that the ambiguity of whether or not a ring has separated is reduced but not eliminated the uncertainty with which separation events can be specified remains approximately 4 weeks even with nearly continuous data primary peaks in the distribution of separation intervals are found at 6 and 11 months with a smaller peak at 9 months if the spectrum is smoothed heavily enough a peak in the distribution can be formed nearer 12 months but this near annual peak is a result more of the smoothing than of the data

northern hemisphere winter circulation associated with the north atlantic oscillation and stratospheric polar night jet the interannual variability of the atmospheric winter circulation as characterized by the geopotential height at 500 hpa and temperature at 850 hpa associated with the north atlantic oscillation nao and stratospheric polar night jet pnj is examined it is suggested that the wintertime atmospheric circulation related to the nao index can be separated into two different modes of variability one is a regional mode characterized by a meridional dipole type pattern in the 500 hpa geopotential height anomaly field over the atlantic region the other having more zonal structure extends over wider region of the northern hemisphere this is also related to the lower stratospheric polar night jet air temperature near the surface over the eastern part of the eurasian continent is more closely correlated with the above mentioned hemispheric mode of variability than the regional nao

analysis and modeling of the arctic oscillation using a simple barotropic model with baroclinic eddy forcing abstract in this study a numerical simulation of the arctic oscillation ao is conducted using a simple barotropic model that considers the barotropic baroclinic interactions as the external forcing the model is referred to as a barotropic s model since the external forcing is obtained statistically from the long term historical data solving an inverse problem the barotropic s model has been integrated for 51 years under a perpetual january condition and the dominant empirical orthogonal function eof modes in the model have been analyzed the results are compared with the eof analysis of the barotropic component of the real atmosphere based on the daily ncep ncar reanalysis for 50 yr from 1950 to 1999 according to the result the first eof of the model atmosphere appears to be the ao similar to the observation the annular structure of the ao and the two centers of action at pacific and atlantic are simulated nicely by the barotropic s model therefore the atmospheric low frequency variabilities

8000 yr of black carbon accumulation in a colluvial soil from nw spain analytical pyrolysis gc ms and solid state 13c nmr nuclear magnetic resonance were applied to the naoh extractable organic matter fraction of a colluvial soil from galicia nw spain that represents more than 8500 yr of accumulation while molecular indicators of vegetation change were looked for it seemed likely that any such signal was disturbed by the intense fire regime of the area this conclusion was drawn from 1 the presence of three charcoal layers 2 the high proportion of aryl c in nmr spectra non quantitative and 3 the prevalence of benzenes and polycyclic aromatic hydrocarbons pahs in the chromatograms 38 6 of total identified peak area also in charcoal poor samples if this conclusion is accurate the area has been subjected to burning episodes for at least 8000 yr additionally the results indicate that biomass burning residues black carbon bc may become naoh extractable after long periods of degradation in mineral soil these results add to our knowledge of the long term fate of bc in soil which is a potential agent in the global c cycle

radiogenic isotopic compositions of low concentration dust and aerosol from the gisp2 ice core abstract we have produced a record of radiogenic isotope compositions of particulate and soluble dust fractions from the gisp2 ice core from basal ice to the surface for each respective dust fraction we measured sr and nd isotope values to constrain the provenance of mineral dust and sea salt aerosol transported to the greenland ice sheet we have produced high precision measurements of end values on sub ng quantities of nd in ice core samples via tims with 1013 ohm resistors the range of measured end values of soluble material 12 9 2 6 to 7 3 0 9 is interpreted to represent sea salt aerosol based on sr isotope compositions that resemble seawater values 0 711007 0 000030 to 0 709416 0 000072 therefore the end potentially provides important insights to the atmospheric circulation patterns at high latitudes at least through mis 5 we compare end values of surface seawater from ocean basins and deltas at high latitudes to alternating relatively radiogenic and unradiogenic end at gisp2 we suggest these changes represent transitions between a climate system dominated by enhanced and persistent arctic oscillation positive anomalies as determined from sea level and ocean bottom pressure measurements and a state representative of modern atmospheric circulation which typically exhibits either negative anomalies or none altogether

northern hemisphere teleconnection patterns during extreme phases of the zonal mean circulation abstract regional climate anomalies associated with year to year changes in the tropospheric zonal mean zonal wind are examined this study focuses on the wintertime northern hemisphere extratropics and compares seasonal mean anomalies associated with to those associated with the el nino southern oscillation during the 1947 94 period dynamical model experiments indicate that a single zonal index characterized by out of phase anomalies at 35 and 55 n is of primary importance for zonal flow stationary wave interactions in the northern hemisphere extratropies such fluctuations in the zonal mean zonal flow are shown to occur independently of tropical sst variability consistent with earlier studies dynamical model experiments and regression analyses of the historical data indicate that such a zonal index explains a significant fraction of the wintertime stationary wave variability in several regions the principal centers of action reside within wave trains over the north pacific north american

seasonal changes in molecular composition of organic matter in lake sediment trap material from nylandssjon sweden the origin and degradation preservation state of organic matter om in lacustrine systems can be studied using its molecular composition pyrolysis gas chromatography mass spectrometry py gc ms

contribution of organic matter molecular proxies to interpretation of the last 55ka of the lynch s crater record ne australia the lynch s crater ne australia deposit is a key information source on late quaternary palaeoenvironmental change including human induced deforestation since the arrival of aboriginals megaherbivore extinction and southern hemisphere tropical climate dynamics this study adds to the important dataset available for the site by assessing the molecular composition of organic matter in the record using pyrolysis gc ms to elucidate ecological and hydrological conditions since 55 ka bp pyrolysates were dominated by methylene chain compounds mccs and lignin products methoxyphenols concomitant increases in mccs and aquatic source indicators biogenic opaline silica si al ratio sem visible debris of sponges and diatoms and aquatic pollen taxa which roughly coincide with abrupt climate events in gisp2 18o heinrich event h3 h1 8 2ka and oscillations at 33 36ka bp reflect transitions from peat dominated by lignin from terrestrial plants to lacustrine mccs from aquatic plants conditions the evidence points towards wet conditions causing the accumulation of layers rich in inorganic sediment during h events favouring the hypothesis of a southward itcz shift rather than an enso induced northward shift as the underlying mechanism this contradicts previous studies using the degree of peat humification index dph we measured dph and the extracts and residues by py gc ms to better understand the validity of this surface moisture proxy paradoxically high dph corresponds to the relatively young 15ka ombrotrophic peat environment as dph relies on the proportion of extractable carbohydrates concentrated in this part of the core while deeper and unarguably more evolved layers are comprised of alkali inextricable lignin and mccs therefore dph does not accurately reflect humidity controlled degradation preservation dynamics and its use for studying climate change in complex records such as lynch s crater is cautioned finally the decoupling of humidity conditions from changes in regional arboreal vegetation supports the hypothesis of an anthropogenic rather than climate driven shift towards sclerophyllous vegetation since 45ka but the hydroseral complexity of the system demands caution on this matter

propagation of the arctic oscillation from the stratosphere to the troposphere geopotential anomalies ranging from the earth s surface to the middle stratosphere in the northern hemisphere are dominated by a mode of variability known as the arctic oscillation ao the ao is represented herein by the leading mode the first empirical orthogonal function of low frequency variability of wintertime geopotential between 1000 and 10 hpa in the middle stratosphere the signature of the ao is a nearly zonally symmetric pattern representing a strong or weak polar vortex at 1000 hpa the ao is similar to the north atlantic oscillation but with more zonal symmetry especially at high latitudes in zonal mean zonal wind the ao is seen as a north south dipole centered on 40 45 n in zonal mean temperature it is seen as a deep warm or cold polar anomaly from the upper troposphere to 10 hpa the association of the ao pattern in the troposphere with modulation of the strength of the stratospheric polar vortex provides perhaps the best measure of coupling between the stratosphere and the troposphere by examining separately time series of ao signatures at tropospheric and stratospheric levels it is shown that ao anomalies typically appear first in the stratosphere and propagate downward the midwinter correlation between the 90 day low pass filtered 10 hpa anomaly and the 1000 hpa anomaly exceeds 0 65 when the surface anomaly time series is lagged by about three weeks the tropospheric signature of the ao anomaly is characterized by substantial changes to the storm tracks and strength of the midtropospheric flow especially over the north atlantic and europe the implications of large stratospheric anomalies as precursors to changes in tropospheric weather patterns are discussed

a detailed pyrolysis gc ms analysis of a black carbon rich acidic colluvial soil atlantic ranker from nw spain abstract despite the potentially large contribution of black carbon bc to the recalcitrant soil organic matter pool the molecular level composition of aged bc has hardly been investigated pyrolysis gc ms which provides structural information on complex mixtures of organic matter was applied to the naoh extractable organic matter of an acidic colluvial soil atlantic ranker sampled with high resolution 5 cm that harbours a fire record of at least 8 5 ka additionally 5 charcoal samples from selected soil layers were characterised using pyrolysis gc ms for comparison pyrolysis gc ms allowed distinguishing between bc and non charred organic matter it is argued that a large proportion of the polycyclic aromatic hydrocarbons pahs benzenes and benzonitrile in the pyrolysates of the extractable organic matter together accounting for 21 54 of total identified peak area derived from bc in charcoal samples these compounds accounted for 60 98 of the pyrolysis products the large quantity of bc in almost all samples suggested a key role of fire in holocene soil evolution the high c content of the soil up to 136 g c kg 1 soil may be attributed to the presence of recalcitrant organic c as bc in addition to the sorptive preservation processes traditionally held responsible for long term c storage in acid soils interactions between reactive al hydroxides and bc could explain the longevity of bc in the soil this work is the first thorough pyrolysis gc ms based study on ancient fire affected organic matter

spring neap tidal effects on satellite ocean color observations in the bohai sea yellow sea and east china sea 1 eight year ocean color observations between 2002 and 2009 from the moderate resolution imaging spectroradiometer modis onboard the aqua satellite are used to quantitatively assess the spring neap tidal effects on variability of ocean optical and biogeochemical properties in the bohai sea yellow sea and east china sea we demonstrate that spring neap tidal variation is one of important ocean processes that drive both the synoptic scale and mesoscale changes of the ocean optical biological and biogeochemical properties in the coastal region normalized water leaving radiance spectra nlw water diffuse attenuation coefficient at the wavelength of 490 nm kd 490 and total suspended matter tsm concentration show significant spring neap variations in the coastal region within a lunar cycle of 29 53 days in the open ocean however spring neap tidal effects on ocean color data are negligible the entire areal coverage of the turbid waters kd 490 0 3 m 1 showing significant spring neap tidal variations is 4 5 105 km2 similar coverage of moderately turbid waters 0 1 kd 490 0 3 m 1 is also impacted by the spring neap tides the magnitude of the spring neap tidal effects on the variations of the satellite ocean color properties e g kd 490 and tsm is in the same order as the seasonal variations in the coastal region highest kd 490 and largest turbid water coverage lag the new moon or full moon about 2 3 days while the lowest kd 490 and smallest turbid water coverage are also 2 3 days behind the one quarter or three quarter moon this is attributed to the seawater inertia and the friction against the seabed as well as the sediment resuspension process

fossil redox conditions influence organic matter composition in loess paleosols the soil memory recorded in paleosols of loess paleosol sequences is an important contributor to our understanding of past climatic conditions molecular proxies based on the organic matter preserved in paleosols form an essential part of this record but the long term preservation of som is poorly understood especially for sediment traps and slope profiles this paper addresses the composition of organic material from the early weichselian a horizons of the rocourt paleosol a major paleostratigraphic marker for the eemian and early weichselian in western europe naoh extractable organic matter from an exceptionally thick rocourt profile in the kesselt quarry belgian loess belt was analyzed by pyrolysis gas chromatography mass spectrometry pyrolysis gc ms and the results evaluated against paleopedological data the molecular composition of the organic matter at kesselt was compared with reference samples from two nearby quarries including the type locality at veldwezelt hezerwater and to a sample from the contemporary nussloch sequence in germany the som composition found at the four sites indicated a large content of microbial matter and was dominated by carbohydrates and n compounds many of which were not reported before from som pyrolysates differences in the molecular composition between samples both within profiles and between sites coincided with differences in landscape position slope shoulder plateau and fossil redox conditions surface gleys samples form drier and more upland situations contained more burnt material while samples from slope profiles and surface gleys contained even more microbial material in particular chitin results therefore suggest that the admixture of microbial som is considerable in loess paleosols and that differences in edaphic conditions in particular slope position and soil moisture and occurrence of wildfires are important for the long term preservation of som these should therefore be considered when interpreting biogeochemical proxies

the preferred structure of variability of the northern hemisphere atmospheric circulation a nonlinear generalisation of principal component analysis pca is applied to the 500mb geopotential height field of the northern hemisphere extratropical atmosphere it is found that the low frequency variability of the mid troposphere is characterised by three distinct quasi stationary states the states are described and compared to those obtained from applications of cluster analyses and linear pca to the height field evidence is provided that modes obtained through pca notably the arctic oscillation ao are not independent dynamical modes of variability of the northern hemisphere extratropics rather they arise as the optimal linear compromise between the preferred quasi stationary states of the circulation

the interannual variability of the surface eddy kinetic energy in the labrador sea abstract the variability of the surface eddy kinetic energy eke in the labrador sea is investigated with a suite of numerical integrations using a regional ocean model simulations are performed over the period 1980 2001 and are compared to satellite observations over the last 9 years the surface eke pattern in the basin is dominated by a region along the west coast of greenland where eddies mainly anticyclonic are formed by instability of the main currents flowing over the continental slope consistent with previous idealized results here the interannual changes are linked to the shear of the incoming boundary current system imposed as boundary condition to the model domain the highly variable strength of the east greenland current at the northeast boundary derived from the simple ocean data assimilation soda reanalysis strongly influences the vortex formation in the center of the labrador sea where deep convection occurs a statistically significant portion of the modeled interannual surface eke variability is correlated with the local atmospheric forcing and both heat and wind fluxes play an important role and can be adopted as predictors at a lag of 2 3 months the arctic oscillation index can also be used as a remote indicator of the atmospheric fluxes but with lower skill than local measurements in contrast the north atlantic oscillation index does not correlate significantly with the surface eke at intraseasonal and interannual scales the analysis of altimeter data over the 1993 2001 supports the existence of this asymmetry between the regime locally forced by the atmosphere in the central basin and the regime remotely forced by the incoming boundary current along the west greenland coast those results have important implications for monitoring and predicting the surface eddy kinetic energy variability in the labrador sea

variations in near global sea level pressure abstract analysis of a near global sea level pressure slp data set for the period 1951 80 was carried out in terms of complex empirical orthogonal function a large scale propagating slp signal was discovered that seems to include variability previously associated with the southern oscillation monsoons and tropical midlatitude teleconnection patterns in this sense the new feature offers an empirical framework for many of the well known features of the global climate system extensive comparisons show the feature to be observable in the raw data field and thus not a figment of the analysis technique the large slp signal may have its origins in a slp snow feedback loop that acts over the region from siberia to india it is suggested that the maintenance of the slp signal involves slp precipation feedbacks and more importantly the excitation of a major natural mode of climate variation the slp signal is only excited at time scales larger than about 18 mouths i e time scales characteristic of ocea

on the teleconnectivity of the arctic oscillation the term arctic oscillation ao has recently been introduced to describe the leading structure of slp variability over the northern hemisphere a key feature of the ao is its zonally symmetric appearance with a primary center of action over the arctic and opposing anomalies in midlatitudes does the ao s annular appearance result from significant temporal correlations between slp anomalies at distant longitudes the results presented indicate that the temporal coherence between the arctic and midlatitudes is strongest over the atlantic sector with weak correlations between the atlantic and pacific midlatitudes both on intraseasonal and interannual time scales during the past 50 yrs hence the annular character of the ao is more a reflection of the dominance of its arctic center of action than any coordinated behavior of the atlantic and pacific centers of action in the slp field the ao is nearly indistinguishable from the leading structure of variability in the atlantic sector e g the north atlantic oscillation their temporal correlation is 0 95 for monthly data

arctic oscillation or north atlantic oscillation abstract the definition and interpretation of the arctic oscillation ao are examined and compared with those of the north atlantic oscillation nao it is shown that the nao reflects the correlations between the surface pressure variability at its centers of action whereas this is not the case for the ao the nao pattern can be identified in a physically consistent way in principal component analysis applied to various fields in the euro atlantic region a similar identification is found in the pacific region for the pacific north american pna pattern but no such identification is found here for the ao the ao does reflect the tendency for the zonal winds at 35 and 55 n to anticorrelate in both the atlantic and pacific regions associated with the nao and pna because climatological features in the two ocean basins are at different latitudes the zonally symmetric nature of the ao does not mean that it represents a simple modulation of the circumpolar flow an increase in the ao or nao implies stro

black carbon in soils and sediments analysis distribution implications and current challenges this review highlights the ubiquity of black carbon bc produced by incomplete combustion of plant material and fossil fuels in peats soils and lacustrine and marine sediments we examine various definitions and analytical approaches and seek to provide a common language bc represents a continuum from partly charred material to graphite and soot particles with no general agreement on clear cut boundaries formation of bc can occur in two fundamentally different ways volatiles recondense to highly graphitized soot bc whereas the solid residues form char bc both forms of bc are relatively inert and are distributed globally by water and wind via fluvial and atmospheric transport we summarize chronologically the ubiquity of bc in soils and sediments since devonian times differentiating between bc from vegetation fires and from fossil fuel combustion bc has important implications for various biological geochemical and environmental processes as examples bc may represent a significant sink in the global carbon cycle affect the earth s radiative heat balance be a useful tracer for earth s fire history build up a significant fraction of carbon buried in soils and sediments and carry organic pollutants on land bc seems to be abundant in dark colored soils affected by frequent vegetation burning and fossil fuel combustion thus probably contributing to the highly stable aromatic components of soil organic matter we discuss challenges for future research despite the great importance of bc only limited progress has been made in calibrating analytical techniques progress in the quantification of bc is likely to come from systematic intercomparison using bcs from different sources and in different natural matrices bc identification could benefit from isotopic and spectroscopic techniques applied at the bulk and molecular levels the key to estimating bc stocks in soils and sediments is an understanding of the processes involved in bc degradation on a molecular level a promising approach would be the combination of short term laboratory experiments and long term field trials

a review of charcoal analysis as a tool for assessing quaternary and tertiary environments achievements and limits abstract identification of charcoal fragments 2 mm using reflected light microscopy is routinely carried out to study former natural ecosystems assess changes in vegetation communities over time and identify the influence and patterns of behaviour of human populations on vegetation material studied comes either from archaeological horizons or soil profiles despite undeniable limits informative results have been obtained in the last 25 years mostly in southwestern europe where charcoal analysis has been widely applied in quaternary studies examples of these achievements are provided focusing on the major vegetation trends since the upper palaeolithic to the middle ages the techniques used for charcoal analysis in the reconstruction of quaternary vegetation are now being used to study tertiary charcoal and lignites the study of fossil charcoal can be a highly informative method for interpreting ancient ecosystems as species easily degraded may be preserved by charcoalification some results from the lower rhine embayment germany are presented here

definition of antarctic oscillation index following walker s work about his thmous three oscillations published during the 1920 30s many papers were written about atmospheric oscillations a iburth atmospheric oscillation in the middle and high southern latitudes was lbund and nanted the grotarctic oscillation ao a refiers to a large scale alternation of atmospheric mass between the mid latitudes and high latitudes surthce pressure in order to understand the spatial structure of sea level pressure variation in detail empirical orthogonal fitnction analysis is applied an objective index of the antarctic oscillation index aoi is defined as the diffierence of zonal mean sea level pressure between 40os and 65os the aoi has the potential tbr clarifying climate regimes in the southern hemisphere similar to how the na and the npo has been used in the northern hemisphere were there other oscillation s besides nao npo and s especially in the southern hemisphere it had been supposed that there might be other atmospheric oscillation s in the high southern latitudes although as early as in the first quarter of this century walker 1928 had stated that just as in the north atlantic there is a pressure opposition between the azores and iceland there is an opposition between the high pressure belt across chile and the argentine on the one hand and the low pressure area of weddell sea and the bellingshausen sea on the other the scarcity of data in the southern hemisphere hindered the search tbr new oscillation s during the last two decades more comprehensive data over the southern hemisphere became available and more analyses were carried out see kidson 1975 rogers and van loon 1982 mo and l 7 ite 1985 2 4o 1986 connolley 1997 gong and wang 1998 a tburth atmospheric oscillation in the middle and high southern latitudes was tbund and nanted as the antarctic oscillation a wang 1992 gong and wang 1998 the term ao relrs to a large scale alternation of atmospheric mass between the mid latitude sur hce pressure

organic geochemical approaches to identifying formation processes for middens and charcoal rich features abstract charcoal is an important component of archaeological sites that can yield fundamental information useful in understanding past human activities we applied a suite of organic geochemical tools to identify and quantify anthropogenic molecular charcoal fragments in an archaeological site in panola county n texas to determine the provenance of a buried melanic horizon the site is a small middle late caddo occupation inhabited principally between ca 1450 and 1600 ad we tested three molecular techniques to determine their ability to constrain site formation processes solid state 13 c nuclear magnetic resonance spectroscopy nmr lignin free phenols and lignin oxidation products lops and anhydrosugar analysis we demonstrated that in conjunction the three afforded the identification and quantification of anthropogenic molecular charcoal fragments at this archaeological site the approach allowed reconstruction of the fire history and vegetation type around the site during the occupation period the nmr and anhydrosugar analysis pointed to temperature conditions associated with thermal refuse in different contexts in particular geochemical signatures in a smudge pit indicated a higher combustion temperature than for the charcoals in the other paleosol samples suggesting multiple fire uses the data also showed differential persistence of fire signals in environmental samples likely as a result of differential decomposition rate and solubility which may lead to heterogeneous fates of different forms of pyrogenic c in the environment the techniques expand the tool kit available to archaeologists and soil scientists in detecting the human footprint in soil formation especially in warm humid climates where decomposition is rapid

the influence of loop current perturbations on the formation and evolution of tortugas eddies in the southern straits of florida large cyclonic eddies on the northern edge of the florida current are the dominant mesoscale features within the southern straits of florida the most prominent of these features is a quasi stationary eddy that forms near the dry tortugas our observations compiled from 3 years of advanced very high resolution radiometer measurements in the straits of florida and gulf of mexico demonstrate a strong relationship between the generation of anticyclonic rings from the gulf of mexico loop current and the evolution of tortugas eddies within the southern straits of florida in six cases tortugas eddies evolve from cyclonic frontal eddies which form along the boundary of the loop current the eddies remain stationary near the dry tortugas until they are impacted by an approaching loop current frontal eddy the length of time an eddy spends near the dry tortugas is increased when the loop current sheds an anticyclonic ring the involvement of a loop current frontal eddy in the ring shedding process results in a delay in its and hence the tortugas eddy s downstream propagation results suggest that the lifetime of a tortugas eddy can be as long as 140 days when a ring shedding event occurs or as short as 50 days in the absence of any ring shedding events upon entering the straits of florida the tortugas eddies are deformed by the narrowing topography and shrink to approximately 55 of their original size as they propagated downstream the shrinking of these eddies is accompanied by an accelerated translation from 5 km d in the western straits of florida to 16 km d in the east

an analysis of daily maximum wind speed in northwestern europe using generalized linear models abstract the basic climatological pattern and recent trends in daily maximum wind speed dmws for the region 47 5 65 n and 12 5 w 22 5 e are studied using gamma distributions within a generalized linear model between 1958 and 1998 dmws has increased over the ocean in winter but weakened over continental europe in summer large scale circulation changes such as those of the north atlantic oscillation nao and arctic oscillation ao account for the strengthening wind over the ocean global warming may have impacted the regional wind climate in particular southern hemisphere temperature exhibits a significant effect on the distinct oceanic and continental trends in dmws it is suggested that the steady warming of the southern hemisphere during the last few decades may have forced the north atlantic storm track to shift in such a way that storms are enhanced toward the northwestern oceanic area but weakened throughout most of the european continent

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

fire history and human activity revealed through poly cyclic aromatic hydrocarbon pah records at archaeological sites in the middle reaches of the yellow river drainage basin china abstract disentangling the role of natural and anthropogenic factors is a major challenge in paleofire studies here we introduce the molecular biomarkers of polycyclic aromatic hydrocarbon pahs combined with charcoal and black carbon in sediments of archaeological sites to identify anthropogenic signals of environmental change during the middle holocene in the prehistoric period an intensified fire regime period inferred on the basis of pahs char and macro charcoal levels has been attributed to intensified anthropogenic biomass burning from dry crop cultivation between 6500 and 5000 and 3900 3600 yr bp corresponding to the earliest chinese settlements during the miaodigou banpo iv culture and the development of the erlitou culture under drier climate conditions subsequently the fire frequency decreased notably between 4500 and 4000 yr bp as the climate became wetter and there were shifts in the frequency of high magnitude floods corresponding to the abandonment of late neolithic settlements in the floodplain changes in the pah fluxes in sediments are positively correlated with intensified fire regime periods consistent with the charcoal and black carbon fluxes during those periods principal component analysis of pah fluxes suggests that these intensified fire events have a pyrogenic signature implying that the pahs were derived from biomass burning of fuelwood and other woody plants in this study pahs in loess sediments have been used as the indicators of anthropogenic biomass burning through time meanwhile pahs also record the shift of modes of production and the evolution of human settlements as well as the choices made in response to limited natural resources to comprehensively analyze the paleofire records of pahs charcoal and black carbon combined with multiproxy evidence are needed to understand wildfire history as well as human land use and social and cultural development across the study regions in depth

analysis of ocean diurnal variations from the korean geostationary ocean color imager measurements using the dineof method abstract high frequency images of the water diffuse attenuation coefficient at the wavelength of 490 nm kd 490 derived from the korean geostationary ocean color imager goci provide a unique opportunity to study diurnal variation of water turbidity in coastal regions of the bohai sea yellow sea and east china sea however there are many missing pixels in the original goci derived kd 490 images due to clouds and various other reasons data interpolating empirical orthogonal function dineof is a method to reconstruct missing data in geophysical datasets based on the empirical orthogonal function eof it utilizes both temporal and spatial coherencies of data to infer a solution at the missing locations in this study the dineof is applied to goci derived kd 490 data in the yangtze river mouth and the yellow river mouth regions and the dineof reconstructed kd 490 data are used to fill in the missing pixels in fact dineof has been used to fill in gaps in ocean color chlorophyll a and turbidity data from the sea viewing wide field of view sensor seawifs moderate resolution imaging spectroradiometer modis and spinning enhanced visible and infrared imager seviri in previous studies our goci validation results show that the bias between the reconstructed data and the original kd 490 value is quite small

holocene vegetation changes in nw iberia revealed by anthracological and palynological records from a colluvial soil macroscopic charcoal pollen and non pollen palynomorphs were isolated from a colluvial soil located on a small hill in campo lameiro nw spain in order to elucidate the vegetation history of the area and its relation to fire and human activities the presence of macroscopic charcoal throughout the 2 10 m thick soil 42 samples is evidence of frequent fires during the last c 6300 years the charcoal record was dominated by quercus probably q robur ericaceae probably arbutus unedo and erica arborea and fabaceae mainly genista type abrupt changes in the charcoal assemblage are less explicit in the pollen sequence probably as a result of pollen inflow from the downhill surroundings of the study site combined results indicated that the original oak woodland was gradually replaced by pyrophytic shrubs ericaceae and fabaceae as a result of fire recurrence non pollen palynomorphs strongly suggested that vegetation was deliberately ignited by past human societies to facilitate grazing no evidence of local agricultural practices was found episodes of accel erated shrubland expansion occurred c 6000 5500 cal bp c 4000 3500 cal bp and c 1700 cal bp the latter of which caused the definitive settlement of shrublands dominated by ericaceae and fabaceae which are nowadays widespread in nw iberia