Upload File

climatological analysis of alaska blocking patterns, … · widespread surface air temperature...

  • Home
  • Documents
  • CLIMATOLOGICAL ANALYSIS OF ALASKA BLOCKING PATTERNS, … · Widespread surface air temperature (SAT) warming around Alaska has been associated with numerous impacts in the west Arctic,
1
RESEARCH POSTER PRESENTATION DESIGN © 2012 www.PosterPresentations.com ABSTRACT RESULTS: ABI CLIMATOLOGY RESULTS: ABI TRENDS ABI DEVELOPMENT RESULTS: ABI VERSUS PACIFIC TELECONNECTIONS RESULTS: ABI COMPOSITES SUPPORTING DATA AND ANALYSIS Thomas J. Ballinger 1 , Jordan T. McLeod 2 , and Thomas L. Mote 3 CLIMATOLOGICAL ANALYSIS OF ALASKA BLOCKING PATTERNS, 1958-2014 Rapid changes to the climate and environment of greater Alaska are often physically interconnected and linked to oceanic and atmospheric processes that vary across disparate space and time scales. Previous studies have also suggested that synoptic-scale circulation patterns over Alaska have especially profound impacts on the occurrence of temperature and moisture extremes, but there has yet to be a long- term assessment of mid-tropospheric circulation across the region, which may influence the temporal variability of such extreme events. Here, an Alaska Blocking Index (ABI) for the 1958–2014 period is created and analyzed, representing the climatological, mid- tropospheric circulation field over Alaska. This metric is developed over the domain (54–76°N, 125–180°W) by merging daily, gridded 500 hPa geopotential height (GPH) fields derived from the ERA-40 (1958– 1978) and ERA-Interim (1979–2014) reanalyses. Climatological characteristics of the seasonal and annual ABI values are evaluated, and periods of prevalent blocking conditions are identified and subsequently analyzed with respect to a number of reanalysis-derived climate and environmental variables as well as the prominent modes of Pacific climate variability. The ABI has exhibited positive trends since 1979, especially during summer, autumn, and annually. Many of the extreme high ABI values occur since 2000, including the highest annual values in 2013 and 2014. Anomalous blocking patterns in winter and summer are associated with diminished terrestrial snow depth and sea-ice cover, positive near-surface air temperature anomalies, and poleward advection of heat and moisture across Alaska and its bordering seas. Vector wind comparisons at the 500 hPa level between ABI, Pacific North American (PNA) pattern, and Pacific Decadal Oscillation (PDO) extremes reveal distinguishing dynamic characteristics as the ABI center of action and its associated anticyclonic wind field are shifted well north about central Alaska relative to the PNA and PDO. Forthcoming analyses will look further into ABI relationships with regional Arctic change and potential downstream linkages between Alaska blocking and North American mid-latitude climate. INTRODUCTION AND OBJECTIVES CONCLUSIONS AND FUTURE WORK 1 Department of Geography, Texas State University, San Marcos, TX 78130, contact: [email protected] 2 Southeast Regional Climate Center, University of North Carolina, Chapel Hill, NC 3 Department of Geography, University of Georgia, Athens, GA Figure 2. Means (a) and sigmas (b) of the ABI (in meters) by different period divisions for winter (DJF), spring (MAM), summer (JJA), autumn (SON), and annually (Jan–Dec). REFERENCES • Barriopedro D, García-Herrera R, Lupo AR, Hernández E. 2006: A climatology of Northern Hemisphere Blocking. J. Clim. 19: 1042–1063, doi: 10.1175/JCLI3678.1. • Belleflamme A, Fettweis X, Erpicum M. 2015. Recent summer Arctic atmospheric circulation anomalies in a historical perspective. Cryosphere 9: 53–64, doi:10.5194/tc-9-53-2015. • Bieniek PA, Walsh JE, Thoman RL, Bhatt US. 2014. Using climate divisions to analyze variations and trends in Alaskan temperature and precipitation. J. Clim. 27: 2800–2818, doi:10.1175/JCLI-D-13-00342.1. • Dee DP, Uppala SM, Simmons AJ, Berrisford P, Poli P, Kobayashi S, Andrae U, Balmaseda MA, Balsamo G, Bauer P, Bechtold P, Beljaars ACM, van de Berg L, Bidlot J, Bormann N, Delsol C, Dragani R, Fuentes M, Geer AJ, Haimberger L, Healy SB, Hersbach H, Hólm EV, Isaksen L, Kållberg P, Köhler M, Matricardi M, McNally AP, Monge-Sanz BM, Morcrette J-J, Park BK, Peubey C, de Rosnay P, Tavolato C, Thépaut J-N, Vitart F. 2011. The ERA-Interim reanalysis: configuration and performance of the data assimilation system. Q. J. Roy. Meteor. Soc. 137: 553–597, doi:10.1002/qj.828. • Gardner AS, Moholdt G, Cogley JG, Wouters B, Arendt AA, Wahr J, Berthier E, Hock R, Pfeffer WT, Kaser G, Lightenberg SRM, Bolch T, Sharp MJ, Hagen JO, van den Broeke MR, Paul F. 2013. A Reconciled Estimate of Glacier Contributions to Sea Level Rise: 2003 to 2009. Science 340: 852–857, doi:10.1126/science.1234532. • Hanna E, Cropper TE, Hall RJ, Cappelen J. 2016. Greenland Blocking Index 1851–2015: a regional climate change signal. Intl. J. Climatology, in press, doi:10.1002/joc.4673. • Hayasaka H, Tanaka HL, Bieniek PA. 2016. Synoptic-scale fire weather conditions in Alaska. Polar Sci., in press, doi:10.1016/j.polar.2016.05.001. • Jorgenson MT, Marcot BG, Swanson DK, Jorgenson JC, DeGrange AP. 2015a. Projected changes in diverse ecosystems from climate warming and biophysical drivers in northwest Alaska. Climatic Change 130: 131–144, doi:10.1007/s10584-014-1302-1. • Leathers DJ, Yarnal B, Palecki MA. 1991. The Pacific/North American Teleconnection Pattern and United States Climate. Part I: Regional Temperature and Precipitation Associations. J. Clim. 4: 517–528. • McLeod JT, Mote TL. 2015. Linking interannual variability in extreme Greenland blocking episodes to the recent increase in summer melting across the Greenland ice sheet. Intl. J. Climatology 36: 1484–1499, doi:10.1002/joc.4440. • Overland JE, Francis J, Hall R, Hanna E, Kim S, Vihma T. 2015. The melting Arctic and mid-latitude weather patterns: Are they connected? J. Clim. 28: 7917–7932. • Renwick JA, Wallace JM. 1996. Relationships between North Pacific wintertime blocking, El Niño, and the PNA pattern. Mon. Wea. Rev. 124: 2071–2076. • Stroeve JC, Markus T, Boisvert L, Miller J, Barrett A. 2014. Changes in Arctic melt season and implications for sea ice loss. Geophys. Res. Lett. 41: 1216–1225, doi:10.1002/2013GL058951. • Uppala SM, Kållberg P, Simmons A, Andrae U, Bechtold V, Fiorino M, Gibson J, Haseler J, Hernandez A, Kelly G. 2005. The ERA- 40 re-analysis. Q. J. Roy. Meteor. Soc. 131: 2961–3012, doi: 10.1256/qj.04.176. • Wang M, Overland JE. 2015. Projected future duration of the sea-ice-free season in the Alaskan Arctic. Prog. Oceanography 136: 50–59, doi:10/1016/j.pocean.2015.01.001. Figure 3. Interannual change in the ABI height values (in meters) by season, 1958–2014. Figure 6. 500 hPa vector wind composites by negative (≤-1 sigma; left column) and positive (≥+1 sigma; right column) anomalies of the ABI (a and b), PDO (c and d), and PNA (e and f). Anomalies are presented with respect to the 1981–2010 climatological mean. Figure 7. Composite anomaly plots of a) SAT, b) SST, c) 500 hPa GPH, d) 500 hPa vector winds, e) IHF, f) IVT, g) snow depth, and h) sea-ice cover based on the difference between the ten highest and lowest ABI summer values (JJA) since 1979. Figure 8. Composite anomaly plots of a) SAT, b) SST, c) 500 hPa GPH, d) 500 hPa vector winds, e) IHF, f) IVT, g) snow depth, and h) sea-ice cover based on the difference between the ten highest and lowest ABI winter values (DJF) since 1979. The development of the ABI allows the mid-tropospheric flow across greater Alaska to be monitored through time, while also providing an atmospheric metric to broadly contextualize weather and climate variability across Alaska and adjacent environments. In our ABI analysis, we identify the seasonal and annual means and interannual variability of the ABI, which are generally increasing over the latter portion of the ABI record, 1979–2014. These positive trends are statistically significant across climatological spring and summer and the yearly time series, and they are characterized by a number of extreme height values since 2005. Mid-level winds during ABI extremes differ in strength, direction, and location from the PNA and PDO modes, suggesting that the upper-level blocking pattern over Alaska distinctly influences the regional climate. Composite ABI differences (in high versus low years) are further linked to a number of climatic and environmental characteristics, including diminished snow and marginal sea-ice cover, warming lower tropospheric air temperatures, and northward (southward) flows of heat and moisture along the Bering Sea (Alaska-Yukon borderlands). These physical characteristics are dynamically linked to the synoptic-scale environment that is defined by the presence of upper-air anticyclones over Alaska. The ABI represents a regional climate indicator that can be compared against other studies that identify Arctic Amplification-related impacts at multiple scales, especially those focused on identifying variations in the shape and strength of the Northern Hemisphere 500 hPa GPH field. ABI applications may also extend to broader-scale analyses involving hemispheric/global climate change effects on regional atmospheric circulation. There has been increasing scientific interest directed toward investigating North American high-latitude warming and its effects on lower latitude climates (Overland et al. 2015). Future research may further explore these themes by evaluating spatial patterns of seasonal tropospheric air temperature across Canada and the contiguous United States by phase of the ABI. Beyond the potential teleconnection with North American climate patterns, this type of analysis will also allow for further comparison against the PNA, which has been shown to strongly influence temperature and precipitation regimes across the continental United States (Leathers et al. 1991). Environmental conditions and the climate across Alaska are projected to continue to change substantially during the 21 st century (Wang and Overland 2015). Future work will explore ABI events in greater detail at the seasonal and sub-seasonal timescales, including links to other emerging Arctic climate patterns, as anticyclonic conditions are an increasingly common climatological phenomena across both the Pacific and Atlantic sectors of the Arctic (Belleflamme et al. 2015; Hanna et al. 2016). • Daily mean 500 hPa GPH values created from ERA-40, 1958-1978 (Uppala et al. 2005) and ERA-Interim, 1979-2014 (Dee et al. 2011) by averaging datasets across the standard 6-hourly time steps to create ABI • Datasets are interpolated onto a 0.5° x 0.5° gridded domain over the period of record • A Blackmon low-pass filter is applied to daily ABI to minimize high frequency variability and preserve relevant synoptic-scale features in the 500 hPa GPH field • Similar methods are employed in creating the McLeod and Mote (2015) Greenland Blocking Index (GBI) • ABI seasonal means, standard deviations, and linear trends (for DJF, MAM, JJA, and SON) are calculated Figure 4. Time series of seasonal and annual ABI values (in meters), 1958–2014. A 5-year running mean is fit to each of the time series. Figure 5. Linear trends of seasonal and annual ABI values (in meters/year) for the different period divisions. Bars with asterisks (*) and plus signs (+) indicate significant trends at p < 0.05 and p < 0.01, respectively. McLeod JT, Ballinger TJ, Mote TL. (In review). Assessing the Climatic and Environmental Impacts of Anticyclonic Circulation Patterns over Alaska through the Development of a Regional Blocking Index. International Journal of Climatology. Widespread surface air temperature (SAT) warming around Alaska has been associated with numerous impacts in the west Arctic, including sea and glacial ice losses (Gardner et al. 2013; Stroeve et al. 2014), vegetative increase on the tundra (Jorgenson et al. 2015) and an increase in fire weather conditions and large wildfire events (Hayasaka et al. 2016). Atmospheric blocking, persistent ridging in the mid- tropospheric GPH field common around the North Pacific storm track (Barripedro et al. 2006), has been linked to the Pacific-North American (PNA) pattern in winter (Renwick and Wallace 1996) and relatively short-term changes in regional climate in other seasons. Environmental change stemming from multidecadal temperature trends and associated atmospheric circulation regimes is often linked to low frequency ocean sea surface temperature (SST) shifts, such as those characterized by phases of the Pacific Decadal Oscillation (PDO; Bieniek et al. 2014). In this study, we characterize and evaluate the long-term atmospheric circulation over Alaska through the development of a 500 hPa GPH index about the region, termed the Alaska Blocking Index (ABI). Through the development of the ABI, our goal is to better understand seasonal GPH characteristics and their linkages to ongoing climate and environmental changes around Alaska. We also compare the ABI to the PDO and PNA to assess spatiotemporal links between atmospheric circulation over greater Alaska and large-scale Pacific ocean- atmosphere climate variability. Figure 1. Spatial domain for the Alaska Blocking Index (ABI), centered over Alaska, extending from 54–76°N and 125–180°W. • ERA-Interim SAT, SST, 500 hPa GPH and vector winds, integrated heat flux (IHF), integrated vapor transport (IVT), sea-ice coverage, and terrestrial snow depth over ABI domain are composited by ten highest/lowest ABI years since 1979 (years since 2000 in bold) • PDO (JISAO) and PNA (CPC) indices are compared to ABI through 1) detrended Pearson correlations of seasonal values (below) 2) composite plots of 500 hPa vector winds (see Figure 6) Index PNA PDO ABI DJF +0.20 +0.15 ABI MAM -0.07 +0.15 ABI JJA +0.22 +0.15 ABI SON +0.11 +0.35 ABI Annual +0.13 +0.24 Period Highest Years Lowest Years DJF 2014, 1985, 2013, 2009, 1989, 2005, 1982,1980, 1995, 2003 1999, 2006, 1990, 1987, 2012, 1984, 2002, 2001, 1992, 1991 MAM 2002, 1990, 1996, 1989, 2005, 2013, 2014, 1995, 2004, 1997 1985, 1986, 1982, 1980, 1999, 2001, 1994, 2012, 1984, 1992 JJA 2004, 2007, 2013, 2005, 1989, 1993, 1987, 1979, 2010, 2001 1981, 2011, 1983, 2008, 1996, 1986, 1984, 1988, 2002, 2003 SON 2006, 2012, 2002, 1986, 2014, 1991, 1995, 2013, 2003, 2010 2011, 1994, 1990, 1992, 1983, 1999, 2004, 1987, 1988, 2009 Annual 2014, 2013, 2005, 2004, 1989, 1995, 2002, 1996, 2003, 2009 1999, 1992, 1987, 2011, 1984, 2001, 1994, 1988, 1990, 2008 5100 5200 5300 5400 5500 5600 5700 1955 1965 1975 1985 1995 2005 2015 500 hPa geopotential height (m) Winter (DJF) Spring (MAM) Summer (JJA) Autumn (SON) Annual a b c d e f a b c d e f g h a b c d e f g h Bold value is significant at p < 0.05

Upload: others

Post on 23-May-2020

3 views

Category:

Documents


0 download

Report

TRANSCRIPT

Page 1: CLIMATOLOGICAL ANALYSIS OF ALASKA BLOCKING PATTERNS, … · Widespread surface air temperature (SAT) warming around Alaska has been associated with numerous impacts in the west Arctic,

RESEARCH POSTER PRESENTATION DESIGN © 2012

www.PosterPresentations.com

ABSTRACT RESULTS:ABICLIMATOLOGY RESULTS:ABITRENDSABIDEVELOPMENT

RESULTS:ABIVERSUSPACIFICTELECONNECTIONS RESULTS:ABICOMPOSITESSUPPORTINGDATAANDANALYSIS

ThomasJ.Ballinger1,JordanT.McLeod2,andThomasL.Mote3CLIMATOLOGICALANALYSISOFALASKABLOCKINGPATTERNS,1958-2014

RapidchangestotheclimateandenvironmentofgreaterAlaskaareoftenphysicallyinterconnectedandlinkedtooceanicandatmosphericprocessesthatvaryacrossdisparatespaceandtimescales.Previousstudieshavealsosuggestedthatsynoptic-scalecirculationpatternsoverAlaskahaveespeciallyprofoundimpactsontheoccurrenceoftemperatureandmoistureextremes,buttherehasyettobealong-termassessmentofmid-troposphericcirculationacrosstheregion,whichmayinfluencethetemporalvariabilityofsuchextremeevents.Here,anAlaskaBlockingIndex(ABI)forthe1958–2014periodiscreatedandanalyzed,representingtheclimatological,mid-troposphericcirculationfieldoverAlaska.Thismetricisdevelopedoverthedomain(54–76°N,125–180°W)bymergingdaily,gridded500hPageopotentialheight(GPH)fieldsderivedfromtheERA-40(1958–1978)andERA-Interim(1979–2014)reanalyses.ClimatologicalcharacteristicsoftheseasonalandannualABIvaluesareevaluated,andperiodsofprevalentblockingconditionsareidentifiedandsubsequentlyanalyzedwithrespecttoanumberofreanalysis-derivedclimateandenvironmentalvariablesaswellastheprominentmodesofPacificclimatevariability.

TheABIhasexhibitedpositivetrendssince1979,especiallyduringsummer,autumn,andannually.ManyoftheextremehighABIvaluesoccursince2000,includingthehighestannualvaluesin2013and2014.Anomalousblockingpatternsinwinterandsummerareassociatedwithdiminishedterrestrialsnowdepthandsea-icecover,positivenear-surfaceairtemperatureanomalies,andpolewardadvectionofheatandmoistureacrossAlaskaanditsborderingseas.Vectorwindcomparisonsatthe500hPalevelbetweenABI,PacificNorthAmerican(PNA)pattern,andPacificDecadalOscillation(PDO)extremesrevealdistinguishingdynamiccharacteristicsastheABIcenterofactionanditsassociatedanticyclonicwindfieldareshiftedwellnorthaboutcentralAlaskarelativetothePNAandPDO.ForthcominganalyseswilllookfurtherintoABIrelationshipswithregionalArcticchangeandpotentialdownstreamlinkagesbetweenAlaskablockingandNorthAmericanmid-latitudeclimate.

INTRODUCTIONANDOBJECTIVES

CONCLUSIONSANDFUTUREWORK

1DepartmentofGeography,TexasStateUniversity,SanMarcos,TX78130,contact:[email protected],UniversityofNorthCarolina,ChapelHill,NC

3DepartmentofGeography,UniversityofGeorgia,Athens,GA

Figure2.Means(a)andsigmas(b)oftheABI(inmeters)bydifferentperioddivisionsforwinter(DJF),spring(MAM),summer(JJA),autumn(SON),andannually(Jan–Dec).

REFERENCES• BarriopedroD,García-HerreraR,LupoAR,HernándezE.2006:AclimatologyofNorthernHemisphereBlocking.J.Clim. 19:

1042–1063,doi:10.1175/JCLI3678.1.• BelleflammeA,FettweisX,Erpicum M.2015.RecentsummerArcticatmosphericcirculationanomaliesinahistorical

perspective.Cryosphere 9:53–64,doi:10.5194/tc-9-53-2015.• BieniekPA,WalshJE,ThomanRL,BhattUS.2014.UsingclimatedivisionstoanalyzevariationsandtrendsinAlaskan

temperatureandprecipitation.J.Clim. 27:2800–2818,doi:10.1175/JCLI-D-13-00342.1.• DeeDP,UppalaSM,SimmonsAJ,BerrisfordP,PoliP,KobayashiS,AndraeU,BalmasedaMA,BalsamoG,BauerP,BechtoldP,

BeljaarsACM,vandeBergL,BidlotJ,BormannN,DelsolC,DraganiR,FuentesM,GeerAJ,HaimbergerL,HealySB,HersbachH,HólmEV,IsaksenL,KållbergP,KöhlerM,MatricardiM,McNallyAP,Monge-SanzBM,MorcretteJ-J,ParkBK,PeubeyC,deRosnayP,TavolatoC,ThépautJ-N,VitartF.2011.TheERA-Interimreanalysis:configurationandperformanceofthedataassimilationsystem.Q.J.Roy.Meteor.Soc. 137:553–597,doi:10.1002/qj.828.

• GardnerAS,MoholdtG,CogleyJG,WoutersB,ArendtAA,WahrJ,BerthierE,HockR,PfefferWT,KaserG,LightenbergSRM,BolchT,SharpMJ,HagenJO,vandenBroekeMR,PaulF.2013.AReconciledEstimateofGlacierContributionstoSeaLevelRise:2003to2009.Science340:852–857,doi:10.1126/science.1234532.

• HannaE,CropperTE,HallRJ,CappelenJ.2016.GreenlandBlockingIndex1851–2015:aregionalclimatechangesignal.Intl.J.Climatology,inpress,doi:10.1002/joc.4673.

• HayasakaH,TanakaHL,BieniekPA.2016.Synoptic-scalefireweatherconditionsinAlaska.PolarSci.,inpress,doi:10.1016/j.polar.2016.05.001.

• JorgensonMT,MarcotBG,SwansonDK,JorgensonJC,DeGrangeAP.2015a.ProjectedchangesindiverseecosystemsfromclimatewarmingandbiophysicaldriversinnorthwestAlaska.ClimaticChange 130:131–144,doi:10.1007/s10584-014-1302-1.

• LeathersDJ,YarnalB,PaleckiMA.1991.ThePacific/NorthAmericanTeleconnectionPatternandUnitedStatesClimate.PartI:RegionalTemperatureandPrecipitationAssociations.J.Clim. 4:517–528.

• McLeodJT,MoteTL.2015.LinkinginterannualvariabilityinextremeGreenlandblockingepisodestotherecentincreaseinsummermeltingacrosstheGreenlandicesheet.Intl.J.Climatology 36:1484–1499,doi:10.1002/joc.4440.

• OverlandJE,FrancisJ,HallR,HannaE,KimS,VihmaT.2015.ThemeltingArcticandmid-latitudeweatherpatterns:Aretheyconnected?J.Clim.28:7917–7932.

• RenwickJA,WallaceJM.1996.RelationshipsbetweenNorthPacificwintertimeblocking,ElNiño,andthePNApattern.Mon.Wea.Rev.124: 2071–2076.

• StroeveJC,MarkusT,BoisvertL,MillerJ,BarrettA.2014.ChangesinArcticmeltseasonandimplicationsforseaiceloss.Geophys.Res.Lett. 41: 1216–1225,doi:10.1002/2013GL058951.

• UppalaSM,KållbergP,SimmonsA,AndraeU,BechtoldV,FiorinoM,GibsonJ,HaselerJ,HernandezA,KellyG.2005.TheERA-40re-analysis.Q.J.Roy.Meteor.Soc. 131: 2961–3012,doi:10.1256/qj.04.176.

• WangM,OverlandJE.2015.Projectedfuturedurationofthesea-ice-freeseasonintheAlaskanArctic.Prog.Oceanography136:50–59,doi:10/1016/j.pocean.2015.01.001.

Figure3.InterannualchangeintheABIheightvalues(inmeters)byseason,1958–2014.

Figure6.500hPavectorwindcompositesbynegative(≤-1sigma;leftcolumn)andpositive(≥+1sigma;rightcolumn)anomaliesoftheABI(aandb),PDO(candd),andPNA(eandf).Anomaliesarepresentedwithrespecttothe1981–2010climatologicalmean.

Figure7.Compositeanomalyplotsofa)SAT,b)SST,c)500hPaGPH,d)500hPavectorwinds,e)IHF,f)IVT,g)snowdepth,andh)sea-icecoverbasedonthedifferencebetweenthetenhighestandlowestABIsummervalues(JJA)since1979.

Figure8. Compositeanomalyplotsofa)SAT,b)SST,c)500hPaGPH,d)500hPavectorwinds,e)IHF,f)IVT,g)snowdepth,andh)sea-icecoverbasedonthedifferencebetweenthetenhighestandlowestABIwintervalues(DJF)since1979.

ThedevelopmentoftheABIallowsthemid-troposphericflowacrossgreaterAlaskatobemonitoredthroughtime,whilealsoprovidinganatmosphericmetrictobroadlycontextualizeweatherandclimatevariabilityacrossAlaskaandadjacentenvironments.InourABIanalysis,weidentifytheseasonalandannualmeansandinterannualvariabilityoftheABI,whicharegenerallyincreasingoverthelatterportionoftheABIrecord,1979–2014.Thesepositivetrendsarestatisticallysignificantacrossclimatologicalspringandsummerandtheyearlytimeseries,andtheyarecharacterizedbyanumberofextremeheightvaluessince2005.Mid-levelwindsduringABIextremesdifferinstrength,direction,andlocationfromthePNAandPDOmodes,suggestingthattheupper-levelblockingpatternoverAlaskadistinctlyinfluencestheregionalclimate.CompositeABIdifferences(inhighversuslowyears)arefurtherlinkedtoanumberofclimaticandenvironmentalcharacteristics,includingdiminishedsnowandmarginalsea-icecover,warminglowertroposphericairtemperatures,andnorthward(southward)flowsofheatandmoisturealongtheBeringSea(Alaska-Yukonborderlands).Thesephysicalcharacteristicsaredynamicallylinkedtothesynoptic-scaleenvironmentthatisdefinedbythepresenceofupper-airanticyclonesoverAlaska.

TheABIrepresentsaregionalclimateindicatorthatcanbecomparedagainstotherstudiesthatidentifyArcticAmplification-relatedimpactsatmultiplescales,especiallythosefocusedonidentifyingvariationsintheshapeandstrengthoftheNorthernHemisphere500hPaGPHfield.ABIapplicationsmayalsoextendtobroader-scaleanalysesinvolvinghemispheric/globalclimatechangeeffectsonregionalatmosphericcirculation.TherehasbeenincreasingscientificinterestdirectedtowardinvestigatingNorthAmericanhigh-latitudewarminganditseffectsonlowerlatitudeclimates(Overlandetal.2015).FutureresearchmayfurtherexplorethesethemesbyevaluatingspatialpatternsofseasonaltroposphericairtemperatureacrossCanadaandthecontiguousUnitedStatesbyphaseoftheABI.BeyondthepotentialteleconnectionwithNorthAmericanclimatepatterns,thistypeofanalysiswillalsoallowforfurthercomparisonagainstthePNA,whichhasbeenshowntostronglyinfluencetemperatureandprecipitationregimesacrossthecontinentalUnitedStates(Leathersetal.1991).

EnvironmentalconditionsandtheclimateacrossAlaskaareprojectedtocontinuetochangesubstantiallyduringthe21st century(WangandOverland2015). FutureworkwillexploreABIeventsingreaterdetailattheseasonalandsub-seasonaltimescales,includinglinkstootheremergingArcticclimatepatterns,asanticyclonicconditionsareanincreasinglycommonclimatologicalphenomenaacrossboththePacificandAtlanticsectorsoftheArctic(Belleflammeetal.2015;Hannaetal.2016).

• Dailymean500hPaGPHvaluescreatedfromERA-40,1958-1978(Uppalaetal.2005)andERA-Interim,1979-2014(Deeetal.2011)byaveragingdatasetsacrossthestandard6-hourlytimestepstocreateABI

• Datasetsareinterpolatedontoa0.5° x0.5° griddeddomainovertheperiodofrecord

• ABlackmonlow-passfilterisappliedtodailyABItominimizehighfrequencyvariabilityandpreserverelevantsynoptic-scalefeaturesinthe500hPaGPHfield

• SimilarmethodsareemployedincreatingtheMcLeodandMote(2015)GreenlandBlockingIndex(GBI)

• ABIseasonalmeans,standarddeviations,andlineartrends(forDJF,MAM,JJA,andSON)arecalculated

Figure4.TimeseriesofseasonalandannualABIvalues(inmeters),1958–2014.A5-yearrunningmeanisfittoeachofthetimeseries.

Figure5.LineartrendsofseasonalandannualABIvalues(inmeters/year)forthedifferentperioddivisions.Barswithasterisks(*)andplussigns(+)indicatesignificanttrendsatp< 0.05andp<0.01,respectively.

McLeodJT,BallingerTJ,MoteTL.(Inreview).AssessingtheClimaticandEnvironmentalImpactsofAnticyclonicCirculationPatternsoverAlaskathroughtheDevelopmentofaRegionalBlockingIndex.InternationalJournalofClimatology.

Widespreadsurfaceairtemperature(SAT)warmingaroundAlaskahasbeenassociatedwithnumerousimpactsinthewestArctic,includingseaandglacialicelosses(Gardneretal.2013;Stroeveetal.2014),vegetativeincreaseonthetundra(Jorgensonetal.2015)andanincreaseinfireweatherconditionsandlargewildfireevents(Hayasakaetal.2016).Atmosphericblocking,persistentridginginthemid-troposphericGPHfieldcommonaroundtheNorthPacificstormtrack(Barripedroetal.2006),hasbeenlinkedtothePacific-NorthAmerican(PNA)patterninwinter(RenwickandWallace1996)andrelativelyshort-termchangesinregionalclimateinotherseasons.Environmentalchangestemmingfrommultidecadaltemperaturetrendsandassociatedatmosphericcirculationregimesisoftenlinkedtolowfrequencyoceanseasurfacetemperature(SST)shifts,suchasthosecharacterizedbyphasesofthePacificDecadalOscillation(PDO;Bienieketal.2014).

Inthisstudy,wecharacterizeandevaluatethelong-termatmosphericcirculationoverAlaskathroughthedevelopmentofa500hPaGPHindexabouttheregion,termedtheAlaskaBlockingIndex(ABI).ThroughthedevelopmentoftheABI,ourgoalistobetterunderstandseasonalGPHcharacteristicsandtheirlinkagestoongoingclimateandenvironmentalchangesaroundAlaska.WealsocomparetheABItothePDOandPNAtoassessspatiotemporallinksbetweenatmosphericcirculationovergreaterAlaskaandlarge-scalePacificocean-atmosphereclimatevariability.

Figure1.SpatialdomainfortheAlaskaBlockingIndex(ABI),centeredoverAlaska,extendingfrom54–76°Nand125–180°W.

• ERA-InterimSAT,SST,500hPaGPHandvectorwinds,integratedheatflux(IHF),integratedvaportransport(IVT),sea-icecoverage,andterrestrialsnowdepthoverABIdomainarecompositedbytenhighest/lowestABIyearssince1979(yearssince2000inbold)

• PDO(JISAO)andPNA(CPC)indicesarecomparedtoABIthrough1)detrendedPearsoncorrelationsofseasonalvalues(below)2)compositeplotsof500hPavectorwinds(seeFigure6)

Index PNA PDO

ABIDJF +0.20 +0.15

ABIMAM -0.07 +0.15

ABIJJA +0.22 +0.15

ABISON +0.11 +0.35

ABIAnnual +0.13 +0.24

Period HighestYears LowestYearsDJF 2014,1985,2013,2009,1989,

2005,1982,1980,1995,20031999,2006,1990,1987,2012,1984,2002,2001,1992,1991

MAM 2002,1990,1996,1989,2005,2013,2014,1995,2004,1997

1985,1986,1982,1980,1999,2001,1994,2012,1984,1992

JJA 2004,2007,2013,2005,1989,1993,1987,1979,2010,2001

1981,2011,1983,2008,1996,1986,1984,1988,2002,2003

SON 2006,2012,2002,1986,2014,1991,1995,2013,2003,2010

2011,1994,1990,1992,1983,1999,2004,1987,1988,2009

Annual 2014,2013,2005,2004,1989,1995,2002,1996,2003,2009

1999,1992,1987,2011,1984,2001,1994,1988,1990,2008

5100

5200

5300

5400

5500

5600

5700

1955 1965 1975 1985 1995 2005 2015

500

hPa

geop

oten

tial h

eigh

t (m

)

Winter (DJF) Spring (MAM) Summer (JJA)Autumn (SON) Annual

a b

c d

e f

a b c d

e f g h

a b c d

e f g h

Boldvalueissignificantatp<0.05

Climatological Summaries May 2008

Climatological Extremes

METEOROLOGICAL SERVICES - Mauritiusmetservice.intnet.mu/pdfs/monthly-climatological-summaries.pdf · meteorological services monthly bulletin of climatological summaries may 2008

First evaluation of the climatological calibration

Verilog Blocking and Non Blocking

mapping climatological precipitation over mountainous terrain

DOWNSCALING NASA CLIMATOLOGICAL DATA TO PRODUCE …

Climatological Mean

a climatological perspective

Blocking - Habitat Denver of Blocking we install: • Ladder blocking • Deadwood (drywall nailers) • Fire blocking • Kitchen cabinet blocking • Bathroom vanity & cabinet blocking

CLIMATE Basic Meteorology Oklahoma Climatological Survey

Climatological Characteristics of Atmospheric Rivers and ...cw3e.ucsd.edu/wp-content/uploads/2014/05/Rutz_etal_2014_MWR.pdf · Climatological Characteristics of Atmospheric Rivers

Research Article Climatological Features of Korea

A Method for Developing Climatological Rainfall

Climatological Siganls of Paleogroundwater in Jordan

Hurricane Katrina, A Climatological Perspective

Physiographically sensitive mapping of climatological ... · PDF filePhysiographically sensitive mapping of climatological temperature and precipitation across the conterminous

Understanding Verilog Blocking and Non-blocking Assignments

AERODROME CLIMATOLOGICAL SUMMARY TABULAR FORM …

WMO: Guide to Climatological Practices

The Climatological Relationships Between

Meteorological and climatological factors affecting ... · Meteorological and climatological factors affecting transport ... Meteorological and climatological factors affecting transport

EMERGENCY CLIMATOLOGICAL BULLETIN

BLOCKING IT ALL STARTS HERE. BLOCKING Today, we will focus on blocking. Why? Because blocking is offense and offense is blocking – Period. There are two

Lab 1 { The UBC Climatological Station

Climatological Features of Cutoff Low Systems in the ...ephyslab.uvigo.es/publica/documents/file_1379-Climatological... · Climatological Features of Cutoff Low Systems in the Northern

Effective Zone Blocking Techniques - kihuenergia.kihu.fi. jalkapallo_380... · What is Zone Blocking? Zone blocking is simply a style of blocking that allows for those blocking to

Write Blocking CSC 485/585. Objectives Understand the concept of write blocking Understand hardware write blocking Understand software write blocking

USAID Climatological Overview - Peru - Squarespacestatic1.squarespace.com/static/5332efd0e4b05a9dc9a9171a/t/533e1... · USAID Climatological Overview - Peru Gina Stovall, Colin Gannon,

Time Series Analyses of Climatological Records from Auke Bay, Alaska

Non-Blocking Communications · Blocking and Non-Blocking Send and receive can be blocking or non-blocking. A blocking send can be used with a non-blocking receive, and vice-versa

Physiographically sensitive mapping of climatological

LATE PLEISTOCENE GLACIO-CLIMATOLOGICAL CONDITIONS

Zone Blocking Part II - Footwork, Blocking Schemes

Climatological simulations of ozone and atmospheric