us CLIVARU.S. CLIVAR

U.S. CLIMATE VARIABILITY AND PREDICTABILITY (CLIVAR)1717 Pennsylvania Avenue, NW, Suite 250, Washington, DC 20006• www.usclivar.org

May 2008, Vol. 6, No. 1

SuccessfulCoordination - Key

to SuccessfulScience Research

by David M. Legler, Director

Over the past few months Iwas reminded again of theimportance of fundamentals

of coordinating research and pro-grammatic activities. Successfulcoordination seems to be mosteffective if all involved are workingunder a shared vision, agree onroles and responsibilities, and thenshare (to some extent) the credit forthe resulting product or finding. Inclimate research we often rely ongroups like WCRP and CLIVAR tobring together scientists and sup-portive research funders to catalyzethe scientific planning required forproducing the vision and guidancefor roles and responsibilities. As cli-mate science evolves and matures,as funding resources becomesincreasingly constrained, and asagency roles change, the need forthis scientific planning becomeseven stronger. Moreover, newopportunities are always opening.For example there are effortsunderway to revise national climateresearch program plans in antici-pation of a new administration in

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VARIATIONS

Atl. Meridional Overturning Circulation ..1ENSO and SAM Teleconnections.............4High Latitude Surface Fluxes WG ...........8Calendar ..................................................10Drought Workshop ..................................12

IN THIS ISSUE

Atlantic Meridional OverturningCirculation shows significant changes

in early data from international monitoring systems at 26.5ºN

Christopher S. Meinen and Molly O. Baringer NOAA/Atlatntic Oceanographic and Meteorological Laboratory

Recent modeling and paleo-ceanographic studies havesuggested strong linksbetween variations in the

Atlantic Meridional OverturningCirculation (AMOC) and changes inimportant climate signal variations suchas precipitation and tropical storms overthe neighboring continents (e.g. Zhangand Delworth, 2006). The broad spatialscale AMOC flows are a primary mech-anism by which heat energy is trans-ferred from the equator to the poles andthese flows are closely linked with theregional climate variability around theAtlantic basin and the globe.Recognition of this key role for theAMOC led to the identification ofimprovements in understanding of theAMOC being designated as one of fourkey short-term priorities in the recentUS interagency Ocean ResearchPriorities Plan. Historically observa-tions of the AMOC have in general beensomewhat sparse either/both in spaceand time. One of the longest-runningprograms to observe components of theAMOC is the NOAA Western BoundaryTime Series (WBTS) program to moni-tor the Florida Current and the DeepWestern Boundary Current near 27ºN,which has been making observationssince 1982. In 2004 the WBTS programbecame the cornerstone of one of themost audacious field programs ever

attempted: the time series observation offull-water-column circulation across anentire ocean basin. Called theMeridional Overturning CirculationHeat-flux Array (MOCHA) by the USparticipants and the Rapid ClimateChange 26ºN Array (RAPID) by the UKand German participants, this line ofmoorings represents the first true effortto accurately capture the complete top-to-bottom AMOC using somethingother than infrequently repeated hydro-graphic sections (see Figure 1).

These joint programs bring togetherscientists from NOAA/AOML (MollyB a r i n g e r, Chris Meinen, and SilviaGarzoli), the University of Miami (BillJohns and Lisa Beal), the Max PlanckInstitute for Meteorology (JochemMarotzke) and the NationalOceanography Centre, S o u t h a m p t o n(Harry Bryden, Stuart Cunningham,Torsten Kanzow, Joel Hirschi, DarrenR a y n e r, Hannah Longworth, andElizabeth Grant). Several articles haverecently been published in the journalScience and elsewhere discussing theearly results from the overlapping arraysof instruments. Among the first resultsis the discovery that contrary to previ-ous expectations, the AMOC shows ahigh degree of variability on time scalesof days to months (Meinen et al., 2006;Cunningham et al., 2007; Kanzow et al.,2007, Johns et al., 2008). This variabil-ity exists at surprisingly short time

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U.S. CLIVAR2009. U.S. CLIVAR has an oppor-tunity to provide input to new plansand we hope to discuss how best tocontribute to this process in thecoming months.

U.S. CLIVAR Summit2008

The U.S. CLIVAR Summit will be held14-17 July 2008 in Irvine,California - minutes away fromJohn Wayne International (OrangeCounty) Airport. Meeting Reportsand logistical details will be avail-able soon. This will be an opportu-nity for the U.S. CLIVAR panels andcommittee to meet in plenary andseparately. Logistical informationand a draft agenda are availableonline. A science symposium willoccur, Monday, July 14. The topic:

Climate Predictions for2018: What can we saynow and with what fideli -

ty/uncertainty? What is ourplan to better predict cli -mate 10 years into the

future?

key results of the recent RAPID/MOCHAarray is that all five snapshot values of theAMOC discussed in the Bryden et al.,(2005) paper are observed within the firstyear of the array data (Figure 3). Thelarge high-frequency variability found inthe first data from the basin-wideR A P I D / M O C H A array illustrates thedanger of analyzing small numbers ofsnapshot sections as provided by thed e c a d e - a n d - l o n g e r-apart repeat hydro-graphic sections. These results illustratewhy more regular observations such asthose being made by theRAPID/MOCHA array will be required toaccurately determine any possible trendor shift in the AMOC. With these over-lapping programs now funded through atleast the year 2014 by a combination offunding from US-NOAA, US-NSF, andUK-NERC there is an assurance that atleast a complete decade of data will becollected, and over the next few years fur-ther analysis with both observations andnumerical models will be taking place toimprove our understanding of A M O Cvariability and plan for the necessaryobserving systems moving forward intothe future.

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VariationsPublished three times per yearU.S. CLIVAR Office1717 Pennsylvania Ave., NWSuite 250, Washington, DC 20006(202) 419-3471usco@usclivar.org

Staff: Dr. David M. Legler, EditorCathy Stephens,Assistant Editor and Staff Writer

© 2008 U.S. CLIVAR Permission to use any scientific material (text and fig -ures) published in this Newsletter should be obtainedfrom the respective authors. Reference to newslettermaterials should appear as follows: AUTHORS, year.Title, U.S. CLIVAR Newsletter, No. pp. (unpublishedmanuscript).

This newsletter is supported through contributions tothe U.S. CLIVAR Office by NASA, NOAA—ClimateProgram Office, and NSF.

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scales (days to weeks) near the westernb o u n d a r y, where it is perhaps moreexpected as that is where the strongestmeridional flows exist and where thebaroclinic and barotropic components ofthe transport are often opposing oneanother although they are statisticallyuncorrelated (Figure 2; see also Meinenet al., 2006). However this strong high-frequency variability, and the ‘compensa-tion’ between barotropic and barocliniccomponents of the transport, also existswhen the transports are integrated acrossthe entire basin (Kanzow et al., 2007).

An earlier analysis of snapshot hydro-graphic sections published in Nature(Bryden et al., 2005) suggested that therehad been a 30% decrease in A M O Cstrength over the period from 1957 to2004. While there has been no sign ofsuch a precipitous decrease near the west-ern boundary in the Atlantic over thissame time period (Meinen et al., 2006;Schott et al., 2006), such a significantchange in the basin-wide AMOC wouldlikely result in significant changes in airtemperatures, precipitation and other cli-mactically important quantities through-out the Northern Hemisphere. However,the Bryden et al., (2005) analysis wasbased on only five snapshot data pointsover a 50-year period, and another of the

Figure 1. Idealized representation of the RAPID / MOCHA array of moor-ings along 26.5ºN latitude in the basin interior. Note that the instrumentsin the Straits of Florida and the straits themselves are not shown in thelower illustration. Figure courtesy of Darren Rayner, NationalOceanography Centre, Southampton, UK.

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References:Baringer, M. O. and C. S. Meinen, “The

Meridional Overturning Circulation”, in“Supplement to State of the Climate in2007”, J. Levy, ed., Bull. Am. Met. Soc., (inpress), 2008.

Cunningham, S. A., T. Kanzow, D.Rayner, M. O. Baringer, W. E. Johns, J.Marotzke, H. R. Longworth, E. M. Grant, J.J-M. Hirschi, L. M. Beal, C. S. Meinen, andH. L. Bryden, Temporal Variability of theAtlantic Meridional Overt u r n i n gCirculation at 26.5°N, Science, 317, 935.doi:10.1126/science.1141304, 2007.

Johns, W. E., L. M. Beal, M. O. Baringer,J. R. Molina, S. A. Cunningham, T. Kanzow,and D. Rayner, Variability of Shallow andDeep Western Boundary Currents off theBahamas during 2004–05: Results from the26°N RAPID–MOC A rr a y, J. Phys.Oceanogr., 38 (3), 605-623, 2008.

K a n z o w, T., S. A. Cunningham, D.Rayner, J. J-M. Hirschi, W. E. Johns, M. O.Baringer, H. L. Bryden, L. M. Beal, C. S.Meinen, and J. Marotzke, Observed FlowCompensation Associated with theMeridional Overturning at 26.5°N in theAtlantic, Science, 317, 938. doi:10.1126/sci -ence.1141293, 2007.

Meinen, C. S., M. O. Baringer, and S. L.Garzoli, Variability in Deep We s t e r nBoundary Current transports: Preliminaryresults from 26.5°N in the Atlantic, Geophys.Res. Lett., 33, L17610,doi:10.1029/2006GL026965, 2006.

Schott, F. A., J. Fischer, M. Dengler, andR. Zantopp. Variability of the Deep WesternBoundary Current east of the Grand Banks.Geophys. Res. Lett., 33, L21S07,doi:10.1029/2006GL026563, 2006.

Zhang, R., and T. L. Delworth, Impact ofAtlantic Multidecadal Oscillations onIndia/Sahel rainfall and A t l a n t i cHurricanes, Geophys. Res. Lett., 33 (17),doi: 10.1029/2006GL026267, 2006.

Figure 2. Transport(in Sverdrups) inte-grated between theBahamas Bank and72ºW along 26.5ºNand between 800and 4800 dbar.Variations of thebarotropic (blue),baroclinic (red), andtotal transport areshown. Figure modi-fied from Meinen etal., (2006).

Figure 3. Upper panel – Measured constituents of the meridional trans-port above 1000 m integrated from Florida to Africa. Note that the gapin the Florida Current time series resulted from hurricane damage to therecording system; this gap was interpolated in the later analysis. Lowerpanel – The overturning transport, defined as the net meridional trans-port above 1000 m (green line), and the five snapshot estimates of over-turning calculated from hydrographic sections by Bryden et al., (2005).Note that all time series have been smoothed with a three-day low passfilter. Lower panel modified from Baringer and Meinen (2008).

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southern latitudes include the SouthPacific Ocean, off the coast of We s tAntarctica and in the vicinity of theDrake Passage (Bromwich et al. 2004;Turner 2004; Fogt and Bromwich 2006).As an example, a large blocking highpressure forms over the southeast PacificOcean as a response to El Niño, that is, anENSO warm event (Renwick and Revell1999). Low-frequency variability is read-ily seen in the amplitude of this pressurecenter, which can occur with the Pacific-South American (PSA) pattern (e.g.,Kiladis and Mo 1998). Similar to itscounterpart in the Northern Hemisphere,the Pacific-North American (PNA) pat-tern, the PSA represents a series of alter-nating positive and negative geopotentialheight anomalies extending from thewest-central equatorial Pacific throughAustralia-New Zealand, to the SouthPacific near Antarctica-South America,and then bending northward toward

Africa, following a great circle trajectory.Consequently, the climatic influence ofENSO in high southern latitudes canextend to the Atlantic Ocean sector.

On the other hand, the SAM is not anexternal forcing, rather it represents thedominant mode of the circulation vari-ability in high southern latitudes. TheSAM is also known as the high-latitudemode, and the Antarctic Oscillation(AAO, Thompson and Wallace 2000). Itappears as the first empirical orthogonalfunction in the month-to month 500-hPageopotential heights or sea level pressure(e.g., Kiladis and Mo 1998). The phe-nomenon is characterized by zonal pres-sure anomalies in the mid-latitudes hav-ing the opposite sign of the zonal pres-sure anomalies over Antarctica and thehigh southern latitudes. The positive(negative) phase of SAM corresponds toa stronger (weaker) circumpolar westerlyatmospheric circulation over the

Dramatic climate change hasbeen observed in polar regionsof both hemispheres duringrecent decade. In contrast,

however, to the well-recognized patternof warming and melting observed in theArctic), the climate change nearAntarctica is much more nuanced (e.g,Turner et al. 2007). Rapid warming hasoccurred since 1950 in the westernAntarctic Peninsula region, and part ofthe Larsen Ice Shelf on the eastern side ofthe peninsula recently collapsed(Shepherd et al. 2003). Yet, cooling isfound over interior Antarctica (e.g.,Monaghan et al. 2008), and in contrast tothe statistically-significant decrease inArctic sea ice since the early 1970s, nostatistically-significant trend is found forAntarctic sea ice extent during the sametime period (Vinnikov et al. 2006). Thesubtleties of Antarctic climate changerequire us to carefully consider the mech-anisms that influence regional climatevariability. In that regard, we considerthe two most pronounced and well-known atmospheric climate phenomenathat impact the Southern Ocean andAntarctica. The two are the El Niño-Southern Oscillation (ENSO) and theSouthern Hemisphere Annular Mode(SAM) (e.g., Bromwich et al. 2000;Thompson and Wallace 2000; Fogt andBromwich 2006; L'Heureux andThompson 2006).

The ENSO is directly associated withcycles of warm and cold sea surface tem-perature anomalies in the central andeastern equatorial Pacific. It impactsglobal climate on interannual and inter-decadal time scales. Beyond the localimpacts on tropical pressure, temperatureand precipitation, ENSO anomaliesextend poleward in both hemispheres(e.g., Trenberth and Caron 2000).Regions where the ENSO teleconnectionappear particularly strong in the high

Recent ENSO and SAM Teleconnections for AntarcticaBy Ryan L. Fogt, National Research Council

David H. Bromwich, The Ohio State UniversityKeith M. Hines, The Ohio State University

Figure 1. Time series of the normalized Tahiti – Darwin Southern OscillationIndex (SOI) and Southern Hemisphere Annular Model (SAM) index averagedover December, January and February (DJF) for 1957/8 to 2007/8. Values,normalized by 1 standard deviation of the variability, are plotted for the yearof December. The most recent values for 2007/8 are striking as they representboth one of the strongest positive SAM events and the second strongest posi-tive SOI event (La Niña) during the last 50 years.

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Southern Ocean.While there is a modest correlation

between ENSO and SAM, the two phe-nomena have displayed considerableindependence within the well-observedperiod that began around 1957. Severalrecent studies have considered how thetwo different phenomena may interactthrough interference and addition withinthe climate anomalies of high southernlatitudes (L'Heureux and T h o m p s o n2006; Fogt and Bromwich 2006; Fogt2007; and Stammerjohn et al. 2008).For example, Fogt and Bromwich exam-ined linked ENSO-SAM behavior with-in the framework of decadal variability.They found strong additive effects whenLa Niño (El Niño) events correspond tothe positive (negative) phase of SAM.Under such conditions, the contributionsto the induced pressure anomalies nearthe Amundsen Sea will tend to have sim-ilar sign, therefore reinforcing theresponse.

Stammerjohn et al. (2008) expandedthe linkage studies between ENSO andSAM to demonstrate that the impact ofSAM on seasonal sea ice retreat andadvance was much stronger when a LaNiña (El Niño) event corresponded tothe positive (negative) phase of SAM. Inparticular, when 1990s La Niña eventscorresponded the positive phase ofSAM, the March-April-May (australautumn) sea ice advance was delayed byan average of 22 days for the westernAntarctic Peninsula and southernBellingshausen Sea. In contrast, thedelay during the positive phase of SAMaveraged 10 days when La Niña was notpresent. The sea ice advance in the west-ern Ross Sea reacts in an opposite way,occurring earlier with the positive phaseof SAM in the 1990s, however the mag-nitudes of the changes in the Ross Seaare half or less than that near theAntarctic Peninsula. These findingsdemonstrate that climate change in highsouthern latitudes needs to be interpret-ed with regard to ENSO and SAM link-ages. Moreover, the increasing positivepolarity of SAM during the well-observed modern satellite era (beginningaround 1979) will strongly modulate theclimate trends (Fogt and Bromwich

2006; Fogt 2007). The following para-graphs demonstrate the most recentexample of SAM/ENSO synchrony, inthis case occurring during austral sum-mer.

The 2007/8 DJF caseThe magnitude and phase of the

ENSO cycle are often measured via thenormalized Tahiti – Darwin SouthernOscillation Index (SOI). Positive val-ues correspond to La Niña with relativecold temperatures over the tropical east-ern Pacific Ocean. For the SAM,Marshall (2003) developed a station-based index that was free of the spuri-ous variations found in some reanalysisfields from southern high latitudes. Atime series of austral summer-averagedSOI and the Marshall SAM index isshown in Figure 1. Values shown areseasonal averages for December,January and February (DJF) during1957/8 to 2007/8. The recent values for2007/8 are striking as they represent oneof five largest positive SAM events andthe second strongest positive SOI event(La Niña) during the last 50 years.Therefore, we expect strong interactionsfor a high southern latitude region nearWest Antarctica extending from theRoss Sea to the Weddell Sea in accor-dance with Fogt and Bromwich (2006)and Stammerjohn et al (2008).Figure 2 displays the surface pressureanomalies during the recent australsummer (2007/8 DJF). The global pro-jection in Figure 2a shows both the trop-ical and southern high latitude features,while the stereographic projection inFigure 2b depicts the high latitudes indetail. The anomaly field is in accor-dance with both a strong La Niña and astrong positive phase for the SAM.Consistent with the strong zonal circula-tion over the Southern Ocean, a nega-tive pressure anomaly is shown overAntarctica. The observed negativeanomaly over Antarctica in comparisonto long-term stations records has maxi-ma of 8.3 hPa at McMurdo and 8.0 hPaat nearby Scott Base, both at the south-west edge of the Ross Sea. The anticor-relation between high latitudes and mid-latitudes is especially robust at these

Pacific longitudes. Correspondingly,Figure 2 shows a positive anomaly in thevicinity of New Zealand. The series ofanomalies including the negative anom-aly over the Southern Ocean near 50°S,120°W and positive anomaly east ofSouth America resemble a PSA patterncharacteristic of La Niña. The non-zonally-symmetric componentof the pressure anomalies are also con-sistent with a positive SAM, which typi-cally includes an enhanced low near theAmundsen and Bellingshausen Seas(Lefebvre et al. 2004; Kwok and Comiso2002). To the east of the AntarcticPeninsula, the anomaly pattern suggestsenhanced zonal flow over the northernWeddell Sea, and offshore flow near0°longitude. The austral summer case of2007/8 appears to be an ideal case tostudy the combined contributions ofENSO and SAM.

Sea iceThe sea ice pattern for DJF 2007/8 is

now considered as both ENSO and SAMare important for modulating the sea icecover of the Southern Ocean. SouthernHemisphere sea ice anomalies have anincreased climatological significanceduring austral summer when solar inso-lation is large. Sea ice anomalies provid-ed by the Arctic Climate Research groupat the University of Illinois

The U.S. CLIVAR web site gets afacelift. Check out all the latestnews and informtion at:www.usclivar.org

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( h t t p : / / a r c t i c . a t m o s . u i u c . e d u / c r y o s-p h e r e / I M A G E S / c u r r e n t . 3 6 5 . s o u t h . j p g )reveal a huge positive anomaly thatreaches values as large as 2.0?106 km2during summer 2007/8 even while theclimatological sea ice extent rapidlydecreases at this time of year. The anom-alous sea ice processes, however, havemoderated the reduction this summerproducing an anomaly that can reach25% of the actual value. The Ekman driftdue to surface wind stress is believed tobe an important modulator for SouthernOcean sea ice. Hall and Visbeck (2002)demonstrate that the Ekman drift inducedby the increased westerly drag during the

positive SAM phase enhances the north-ward flow of sea ice and contributes togreater areal coverage. Thus the enhancedEkman drift associated with the strongzonal circulation during 2007/8 is sug-gested as contributor to the positive seaice anomaly for the Southern Hemisphere.Furthermore, the decadal trend towardspositive polarity of the SAM can con-tribute to the different trend for Antarcticsea ice in contrast to the observeddecrease in the Arctic.

Figure 3 shows the SouthernHemisphere sea ice extent anomaly forDecember 2007. A representation of theAntarctic Dipole can be seen with a nega-

tive anomaly in sea ice extent (blue area)near the peninsula, and a positive anom-aly (red area) near the eastern Ross Sea.Yuan and Martinson (2001) demonstrat-ed that the Antarctic Dipole is linked toENSO forcing and appears as sea iceextent anomalies of contrasting signs thatextend from the Ross Sea to the WeddellSea. Additionally, Figure 3a shows anextended area with a positive sea iceanomaly that includes the northernWeddell Sea and the region near 0° lon-gitude. The anomaly could be explainedby enhanced Ekman drift over theWeddell Sea and northward wind stressnear 0° longitude. The large area cov-ered by this regional sea ice anomalyindicates that it is especially importantfor the net positive Antarctic anomaly.Figure 3b shows the net anomaly isextremely large by climatological stan-dards. The extension of the teleconnec-tion pattern deep into the Atlantic sectorwas hinted at by Fogt and Bromwich(2006) and Fogt (2007) when they founda coherent ENSO response extendingmuch farther east during the 1990s whenthe SAM tended to the positive phasethan during the 1980s when the SAMtended toward its negative phase. Thestrong synchronized contribution of bothLa Niña and SAM appears to enhancingthis striking sea ice anomaly during therecent summer. The linkage between theENSO and SAM phenomena, however, isnuanced and still poorly understood.New efforts are required to gain a robustunderstanding of this teleconnection.

AcknowledgementsThanks to Gareth Marshall for the SAMIndex. This work is supported by NSFgrant ATM-0751291.

ReferencesB romwich, D. H., A. N. Rogers, P.

Kållberg, R. I. Cullather, J. W. C. White, andK. J. Kreutz, 2000: ECMWF analysis andreanalyses depiction of ENSO signal inAntarctic precipitation. J. Climate, 13, 1406-1420.

Bromwich, D. H., A. J. Monaghan, and Z.Guo, 2004: Modeling the ENSO modulationof Antarctic climate in the late 1990s withPolar MM5. J. Climate, 17, 109-132.

Figure 2. The 2007/8 surfacepressure anomaly during DJFfor (a) both hemispheres, and(b) southern high latitudescompared to the 1979-2007mean. Values are from theNCEP/NCAR Reanalysis andnormalized by 1 standarddeviation (color scale in stan-dard deviations). The patternshows a combination of (1)an ENSO cold event (LaNiña) over the Pacific andSouthern Oceans, and (2) thepositive phase of the SAM.Antarctic stations McMurdoand Scott Base are near theblack circle in (b).

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Fogt, R. L., 2007: Investigation of theSouthern Annular Mode and the El NiÀo -Southern Oscillation Interactions. Ph.D.Thesis, The Ohio State University. 212 pp.

Fogt, R. L., and D. H. Bromwich, 2006:Decadal variability of the ENSO teleconnec -tion to the high latitude South Pacific gov -erned by coupling with the Southern AnnularMode. J. Climate, 19, 979-997.

Hall, A., and M. Visbeck, 2002:S y n c h ronous variability in the SouthernHemisphere atmosphere, sea ice and oceanresulting from the Annular Mode. J. Climate,15, 3043-3057.

Kiladis, G. N., and K. C. Mo, 1998:Interannual and intraseasonal variability inthe Southern Hemisphere. Meteorology of theSouthern Hemisphere, D.J. Karoly and D.G.Vincent, Eds., Amer. Meteor. Soc., 307-336.

Kwok, R., and J. C. Comiso, 2002: Spatialpatterns of variability in Antarctic surfacet e m p e r a t u re: Connections to the SouthernHemisphere Annular Mode and the SouthernOscillation. Geophys. Res. Lett., 29(14),1705, doi:10.1029/2002GL015415.

Lefebvre, W., H. Goosse, R. Timmermann,and T. Fichefet, 2004: Influence of theSouthern Annular Mode on the sea ice - oceansystem. J. Geophys. Res., 109, C09005,doi:10.1029/2004JC002403.

L'Heureux, M. L., and D. W. J. Thompson,2006: Observed relationships between the ElNiño - Southern Oscillation and the extrat -ropical zonal mean circulation. J. Climate,19, 276-287.

Marshall, G. J., 2003: Trends in theSouthern Annular Mode from observationsand reanalyses. J. Climate, 16, 4134-4143.

Monaghan, A. J., D. H. Bromwich, W.Chapman, and J. C. Comiso, 2008: Recentvariability and trends of Antarctic near-sur -face temperature. J. Geophys. Res., 11 3 ,D04105, doi:10.1029/2007JD009094.

Renwick, J. A., and M. J. Revell, 1999:Blocking over the South Pacific and Rossbywave propagation. Mon. Wea. Rev., 127,2233–2247.

Scambos, T. A., S. Barreira, S. Colwell, J.Turner, R. L. Fogt, H. Liu, R. A. Massom, A.Monaghan, D. Bromwich, K. Jezek, P. A.Newman, P. Reid, S. Stammerjohn, and L.Wang, 2008: State of the climate 2007 –Antarctica. Bull. Amer. Meteorol. Soc., 89, inpress.

Shepherd, A., D. Wingham, T. Payne, P.Skvarca, 2003: Larsen Ice Shelf has progres -sively thinned. Science, 302, 856.

Stammerjohn, S. E., D. G. Martinson, R.C. Smith, X. Yuan, and D. Rind, 2008: Trendsin A n t a rctic annual sea ice re t reat andadvance and their relation to El Niño-Southern Oscillation and Southern AnnularMode variability. J. Geophys. Res., 11 3 ,

Figure 3. Antarctic sea ice anomalies for December extracted from Scamboset al. (2008) including (a) the horizontal distribution of sea ice concentrationanomaly during December 2007 via a color scale. Positive (negative) anom-alies are red (blue). The largest positive contribution is located near theAtlantic Sector east of the Antarctic Peninsula. A secondary positive contribu-tion is found near the Ross Sea. The pattern reflects the combined contribu-tions of La Nina and SAM. In (b) the time series is shown of the overallAntarctic sea ice extent anomaly from the late 1970s to 2007. December2007 has one of the largest positive anomalies during this time span, corre-sponding to the very strong ENSO and SAM events.

C03S90, doi:10.1029/2007JC004269.Thompson, D. W. J., and J. M. Wallace,

2000: Annual modes in the extratropical cir -culation, Part I: month-to-month variability.J. Climate, 13, 1000-1016.

Trenberth, K. E., and. J. M. Caron, 2000:The Southern Oscillation revisited: Sea levelpressure, surface temperatures and precipi -tation. J. Climate, 13, 4358-4365.

Turner, J., 2004: Review: The El Niño-Southern Oscillation and Antarctica. Int. J.Climatol., 24, 1-31.

Turner, J., J. E. Overland, and J. E.Walsh, 2007: An Arctic and Antarctic per -spective on recent climate change. Int. J.

Climatol., 27, 277-293.Vinnikov, K. Y., D. J. Cavalieri, and C. L.

Parkinson, 2006: A model assessment ofsatellite observed trends in polar sea iceextents. Geophys. Res. Lett., 33, L05704,doi:10.1029/2005GL02528.

Yuan, X., and D. G. Martinson, 2001:The Antarctic Dipole and its predictability.Geophys. Res. Lett., 28, 3609-3612

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U.S. CLIVAR has established aWorking Group on HighLatitude Surface Fluxes this

year, with the particular goal of address-ing some of the myriad challenges asso-ciated with air-sea and air- i c e - o c e a nexchanges in Arctic, Antarctic, andSouthern Ocean regions. The workinggroup activities are motivated by severalidentified deficiencies in estimates ofhigh latitude surface fluxes (e.g., sensi-ble and latent heat, radiative fluxes,stress, and gas fluxes).

First, in situ observations of fluxesare difficult to obtain because high lati-tude regions are remote and requireinstrumentation able to withstand highwinds, extremely rough seas, and coldtemperatures. Such observations arevital for satellite calibration, which isone approach to filling the void of tradi-tional observations.

Second, the unique conditions in highlatitude regions mean that lessonslearned in equatorial and subtropicalregions do not necessarily translate intoimprovements in high latitude fluxes.For example, winds over the SouthernOcean are among the strongest in theworld, both in magnitude and frequencyof occurrence, and can exceed the speedsfor which scatterometer wind retrievalalgorithms have been tested and therange of validity for standard drag coef-ficients. Northern Hemisphere, high-lat-itude, extreme marine storms occur lessoften, but tend to strengthen much morerapidly. Ocean and atmospheric stratifi-cation in high latitude regions can beextremely weak, resulting in deep mixedlayers, and it can be extremely strong,pushing the limits of existing stabilityparameterizations. High latitude regionsare also characterized by ice andice/water mixes, which add additionalcomplexity to calculating and applying

fluxes. Third, since high latitude regions are

u n d e r-going rapid climate change,marked by rapidly diminishing icecover, we expect that the character ofhigh latitude fluxes is also changing.That is, flux climatologies are evolvingin regions where the characteristics ofeither the overlying atmosphere or theupper ocean are changing. Fluxesthrough an ice-free Arctic Ocean, forexample, are distinctly different fromfluxes through a high-albedo, ice-cov-ered Arctic Ocean. A substantial reduc-

tion in the extent of an ice sheet willmodify the fluxes in a wider area thanthat of the changing ice sheet, due tomodification of the overlying air mass.These fluxes are expected to have alarge influence on both atmospheric andoceanographic circulation and merid-ional energy transfer, which will impactglobal climate in fundamental ways: asexamples, high latitude surface fluxescontrol meridional overturning circula-tion in the ocean, ocean uptake of CO2,and meridional transport of heat in theatmosphere.

U.S. CLIVAR Working Group on High Latitude SurfaceFluxes

Mark A. Bourassa, Florida State University andSarah Gille, Scripps Institute of Oceanography (co-chairs)

Figure 1. Distributions (5th, 25th, 50th, 75th, and 95th percentiles) of contribu-tions to zonally averaged Atlantic sensible heat fluxes. Reanalysis productsinclude NCEPR2 (Kanamitsu et al. 2002), JRA25 (Onogi et al. 2007), andERA40 (Uppalla et al. 2005). Satellite derived products include IFREMER andHOAPS2 (based on method of Grassl et al. 2000). The HOAPS2 variablesexamined herein are identical in the HOAPS3 product. Products based on shipand buoy observations include FSU3 (adapted from the method of Bourassa etal. 2005) and NOC1.1 (formerly SOC; Josey et al. 1998). Hybrid NWPmodel and satellite products include WHOI (Yu and Weller 2007) and GSSTF2(Chou et al. 2003). These products were chosen because they are freely avail-able, reasonably easy to obtain, and reasonably homogeneous throughout acommon comparison period. The common period of March 1993 throughDecember 2000 is examined.

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VARIATIONSFlux products that include high lati-

tudes can differ substantially, even intheir climatological annual averages, andthey do not resolve small-scale featuresthat are present in sea surface temperatureor wind fields. For example, monthlyaveraged sensible and latent heat fluxeswere compared for nine research qualityproducts, and found to differ by >40Wm-2 in both sensible (Fig. 1) and latent (Fig.2) heat fluxes for the high latitude (icefree) southern and northern portions ofthe Atlantic basin. In particular, sensibleheat fluxes in the Southern Ocean have arelatively large spread among productscompared to the rest of the Atlantic basin(for at least the 5th through 75th per-centiles of fluxes over what is consideredto be year-around open water). Latentheat fluxes have a relatively small spreadin the high southern latitudes due to therelatively small values of this flux; how-ever, the spread in the high northern lati-tudes is rather wide for the strongerevents. The wide range of values for thesefluxes is a major issue for high latitudee n e rgy budgets. In contrast, monthlystress products are in relatively goodagreement; however, synoptic scale (andfiner) variability in reanalysis products ishighly suspect in the Southern Ocean(Hilburn et al. 2003). This findingappears to be partially related to a verystrong dependence on rawindsonde datain these products (Langland et al. 2008).The strengths and weaknesses of fluxproducts differ from product to product,and are not sufficiently well described.

At this point, it is not clear to thedevelopers of flux products what accura-cies and resolutions are required to studykey processes in high latitudes. Whileconcerns about fluxes are common, therehas not always been extensive communi-cation between the users of flux products,who hope for accurate gridded fields, andthe observers of fluxes, who concernthemselves with the details of turbulentboundary layer physics. The physics con-sidered in flux parameterizations alsochanges the distribution of extreme forc-ing events (Fig. 3), which have a dispro-portionately large impact on some atmos-phere and ocean processes.

Furthermore, there is often a discon-

nect with the producers of gridded fluxfields and large segments of the userc o m m u n i t y. Similarly, Arctic andAntarctic specialists rely on somewhatdifferent funding streams and have tend-ed not to interact; analogous issues applyfor meteorologists and oceanographers.However, there appears to be much com-mon ground.

The International Polar Year (IPY)intensive observing period (2007-09) isnow underway, and several high latitudeflux programs are just beginning.Spurred by IPY, planning is starting forArctic and Southern Ocean observingsystems. While IPY has drawn the atten-tion of a large number of internationalcommittees, there has been comparative-ly little focused effort on high latitudefluxes. These fluxes are of interest for awide range of oceanographic, atmos-pheric, and over-ice applications. Thisprovides a particular impetus for the USCLIVAR working group. ObjectivesThe High Latitude Surface Flux WorkingGroup has a largely scientific focus,aimed at evaluating the current state ofknowledge for high latitude fluxes, dis-seminating our evaluation to the broaderscientific community, and layinggroundwork for improved flux estimates.The working group will consider air-seafluxes of momentum, heat, radiation,freshwater, and gas. It will also evaluate

fluxes through open ocean, ice coveredregimes as well as transition zones, andwill consider both Arctic andAntarctic/Southern Ocean regions.

The group has two specific goals thatit intends to address in its two year life-time:A. Assess status of flux products formomentum and heat in high-latituderegimes, providing an honest assessmentof the state of flux products; evaluatecommonalities between Arctic andAntarctic. These will be assessed on avariety of spatial/temporal scales that areimportant to the user community.B. On the basis of the flux assessment,identify priorities for continued fluxobservations, parameterizations, andrequirements for updated reanalyses andgridded flux products.

The working group is beginning tomake plans for a workshop focused onhigh latitude surface fluxes. A key goalfor this workshop is to engage a broaderrange of perspectives.Participation

The co-chairs are Mark Bourassa(Florida State University, FSU) andSarah Gille (Scripps Institution ofOceanography, SIO). The other membersof the working group are Cecilia Bitz(University of Washington), DaveCarlson (IPY, British Antarctic Survey),

Figure 2. Asfor Fig. 1,except forthe latentheat flux.

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U.S. CLIVAR

Course on Satellite Oceanography2008 3-23 August 2008Ensenada, MexicoContact: http://www.ioc.unesco.org

NOAA OCO Annual Meeting 3-5 September 2008Silver Spring, MDAttendance: InvitedContact: http://www.oco.noaa.gov

NOAA CPPA PI Meeting29 September - 1 October 2008Silver Spring, MDAttendance: InvitedContact: http://www.climate.noaa.gov

Third CLIVAR/GODAE Meeting onOcean Synthesis Evaluation6-7 October 2008Tokyo, JapanAttendance: InvitedContact: http://www.clivar.org

CLIVAR Drought Workshop and NOAAClimate Diagnostics and PredictionWorkshop 20-24 October 2008Lincoln, NebraskaAttendance: OpenContact:http://www.cpc.ncep.noaa.gov/products/outreach/CDPW33.shtml

WMO Commission for AtmosphericSciences (CAS) - Fourth InternationalWorkshop on Monsoons (IWM-IV)20-25 October 2008Beijing, ChinaAttendance: OpenContact: http://www.wmo.int

Workshop on Uncertainties in High-Resolution Climate Proxy Data9-11 June 2008Trieste, ItalyAttendance: InvitedContact: http://www.clivar.org

2nd Joint Global Ocean SurfaceUnderway Data (GOSUD)/ShipboardAutomated Meteorological andOceanographic System(SAMOS)Workshop10-12 June 2008Seattle, WashingtonAttendance: OpenContact: Shawn Smith(smith@coaps.fsu.edu)

Workshop on Uncertainties in High-Resolution Climate Proxy Data9-11 June 2008Trieste, ItalyAttendance: InvitedContact: http://www.clivar.org

PAGES-CLIVAR Panel Meeting12 June 2008Trieste, ItalyAttendance: InvitedContact: http://www.clivar.org

CCSM Annual Meeting17-19 June 2008Breckinridge, ColoradoAttendance: InvitedContact: http://www.ccsm.ucar.edu

2008 IEEE International Geoscience &Remote Sensing Symposium 6-11 July 2008Boston, MAAttendance: OpenContact: http://www.igarss08.org/

Summer School on ENSO: Dynamicsand Predictability 14-23 June 2008Puna, HawaiiAttendance: LimitedContact: http://www.clivar.org

Conference on Global AtmosphericCirculation during the Past 100 Years 15-20 June 2008Monte Verita, SwitzerlandAttendance: OpenContact: http://www.clivar.org

International Workshop on EarthObservation and Remote SensingApplications30 June - 2 July 2008Beijing, ChinaAttendance: OpenContact: http://www.2008eorsa.org/

SCAR/IASC IPY Open ScienceConference: "Polar Research - Arcticand Antarctic Perspectives in theInternational Polar Year"8-11 July 2008St. Petersburg, RussiaAttendance: OpenContact:http://www.scar-iasc-ipy2008.org/

IGARSS 2008 7-11 July 2008Boston, MassachusettsAttendance: OpenContact: http://www.igarss08.org

US CLIVAR Science Symposium onClimate in 2018 14 July 2008Irvine, CAAttendance: LimitedContact: http://www.usclivar.org

US CLIVAR Summit 15-17 July 2008Irvine, CAAttendance: InvitedContact: http://www.usclivar.org

Western Pacific Geophysics Meeting29 July - 1 August 2008Cairns, AustraliaAttendance: OpenContact:http://www.agu.org/meetings/wp08/

Calendar of CLIVAR and CLIVAR-related meetingsFurther details are available on the U.S. CLIVAR and International CLIVAR web sites: www.usclivar.org and www.clivar.org

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Will Drennan (University of Miami),Chris Fairall (NOAA, Boulder), RossH o ffman (Atmospheric andEnvironmental Research, Inc.), GudrunMagnusdottir (University of California,Irvine), Mark Serreze (University ofColorado), Kevin Speer (FSU), LynneTalley (SIO), Gary Wick (NOAA,Boulder), .

The working group welcomes inputfrom others and expects to coordinatewith programmatic groups focusedboth on surface fluxes and on the Arcticand Antarctic regions, including IPY,the Study of Environmental A r c t i cChange (SEARCH), the Climate andCryosphere Project (CliC), theCliC/International CLIVAR A r c t i cClimate Panel, the International CLI-VAR Southern Ocean Panel, the ArcticOcean Model Intercomparison Project(AOMIP), the Southern Ice-OceanModel Intercomparison Project(SIOMIP), the Global Energy andWater Cycle Experiment (GEWEX),the Arctic Observing Network, theSouthern Ocean Observing System,SEAFLUX, Shipboard A u t o m a t e dMeteorological and OceanographicSystems (SAMOS), the World ClimateResearch Program Working Group onSurface Fluxes, the Surface Ocean—Lower Atmosphere Study (SOLAS),and the Southern Ocean Gas ExchangeExperiment (GasEx).

Further information about the work-ing group is available on the web: h t t p : / / w w w. u s c l i v a r. o rg / O rg a n i z a t i o n / hlatwg.htmlReferences

Bourassa, M. A., 2006: Satellite-basedobservations of surface turbulent stress dur -ing severe weather, Atmosphere - oceaninteractions, Vol. 2., W. Perrie, Ed., WessexInstitute of Technology Press, 35 – 52 pp.

Bourassa, M. A., R. Romero, S. R.Smith, and J. J. O’Brien, 2005: A new FSUwinds climatology. J. Climate, 18, 3686-3698.

Chou, S.-H., E. Nelkin, J. Ardizzone, R.M. Atlas, and C.-L. Shie, 2003: Surface tur -bulent heat and momentum fluxes overglobal oceans based on the Goddard satel -lite retrievals, version 2 (GSSTF2). J.Climate, 16, 3256-3273.

Fairall, C. W., E. F. Bradley, J. E. Hare,A. A. Grachev, and J. B. Edson, 2003: Bulkparameterizations of air-sea fluxes: updates

and verification for the COARE algorithm. J.Climate., 16, 571-591.

Grassl, H., V. Jost, J. Schulz, M. R.Ramesh Kumar, P. Bauer, and P. Schluessel,2000: The Hamburg Ocean-AtmosphereParameters and Fluxes from Satellite Data(HOAPS): A Climatological Atlas ofSatellite-Derived A i r-Sea InteractionParameters over the World Oceans. ReportNo. 312, ISSN 0937-1060, Max PlankInstitute for Meteoro l o g y, Hamburg , .[Available at http://www.hoaps.zmaw.de/]

Hilburn, K. A., M. A. Bourassa, and J. J.O'Brien, 2003: Scattero m e t e r- d e r i v e dresearch-quality surface pressure fields forthe Southern Ocean. J. Geophys. Res., 108,10.1029/2003JC001772.

Josey, S. A., E. C. Kent, and P. K. Taylor,1998: The Southampton OceanographyC e n t re (SOC) Ocean-Atmosphere Heat,Momentum and Freshwater Flux A t l a s .Southampton Oceanography Centre Rep. 6,Southampton, UK, 30pp + figs. [Available ath t t p : / / w w w. n o c . s o t o n . a c . u k / J R D / M E T / P D F /SOC_flux_atlas.pdf]

Kanamitsu, M., W. Ebisuzaki, J. Woollen,S.-K. Yang, J. J. Hnilo, M. Fiorino, and G. L.P o t t e r, 2002: NCEP-DOE A M I P - I IReanalysis (R-2). Bull. Amer. Meteor. Soc.,83, 1631-1643.

Kara, A. B., H. E. Hurlburt, and A. J.Wallcraft, 2005: Stability-dependentexchange coefficients for air-sea fluxes. J.Atmos. and Oceanic Technol., 22, 1080-1094.

Langland, R. H., R. N. Maue, and C. H.Bishop, 2008: Uncertainty in AtmosphericTemperature analysis. Tellus. (in revision).

Large, W. G., and S. Pond, 1981: Openocean momentum flux measurements in mod -erate to strong winds. J. Phys. Oceanogr., 11,324-336.

______, and ______, 1982: Sensible andlatent heat flux measurements over theocean. J. Phys. Oceanogr.: 12, 464–482.

______, J. C. McWilliams, and S. C.Doney, 1994: Oceanic vertical mixing: areview and a model with a nonlocal bound -ary layer parameterization. Rev. Geophys.,32. 363-403.

Onogi, K., and coauthors, 2007: TheJRA-25 Reanalysis. J. Meteor. Soc. Japan,85, 369-432.

Smith, S. D., 1980: Coefficients for seasurface wind stress, heat flux, and wind pro -files as a function of wind speed and temper -ature. J. Geophys. Res., 93, 15,467-15,472.

______, R. J. Anderson, W. A. Oost, C.Kraan, N. Maat, J. DeCosmo, K. B.Katsaros, K. L. Davidson, K. Bumke, L.Hasse, and H. M. Chadwick, 1992: Sea sur -face wind stress and drag coefficients: theHEXOS results. Bound.-Layer. Meteoro., 60,109-142.

Taylor, P. K., and M. J. Yelland, 2001:The Dependence of sea surface roughness onthe height and steepness of the waves. J.Phys. Oceanogr., 31, 572-590.

Uppala, S. M., and coauthors, 2005: TheERA-40 re-analysis. Quart. J. Roy. Meteor.Soc., 131, 2961-3012.

Yu, L., and R. A. We l l e r, 2007:Objectively analyzed air-sea heat fluxes forthe global ice-free oceans (1981-2005). Bull.Amer. Meteor. Soc., 88, 527-539.

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Figure 3. Latent heat flux probability distributions for various models. Six of themodels (Large and Pone 1981; Smith 1988, Large et al. 1994; HEXOS: Smith etal. 1992; Taylor and Yelland 2001; and Bourassa 2006) have been coded todiffer only in their stress related parameterization (drag coefficient or roughnesslength). Two models are used as coded: COAREv3 (Fairall et al. 2003) andKara et al. (2005).

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Subscription requests, and changes of address should be sent to the attention of the U.S. CLIVAR Office (cstephens@usclivar.org)

U.S. CLIVAR Drought Working Group WorkshopIn Conjunction with NOAA’s 33rd Climate Diagnostics and Prediction workshop.

20-24 October 2008

The workshop will be hosted by the NationalDrought Mitigation Center, University of Nebraska, Lincoln;and co-sponsored by the Climate Prediction Center (CPC) ofthe National Centers for Environmental Prediction / NOAAand the U.S. Climate Variability and Predictability (U.S. CLI-VAR) Program. The AMS is a cooperating sponsor.

The workshop will focus on the status and prospectsfor advancing climate monitoring, assessment and predic-tion, with major emphasis on drought. This includes threemajor themes: (i) improving climate predictions / pre-dictability, (ii) understanding and attribution of drought andits impacts, and (iii) incorporating climate predictions / pro-jections in the development and delivery of drought prod-ucts. Note that in a departure from past years, the 2008CDPW will address drought across multiple time scales(weekly through decadal to centennial and longer) and formultiple regions (North America, South America, Africa,Asia, etc.). Thus, papers that assess the role of ocean, land,and seasonal cycle in multi-year droughts as evidenced incoupled models (especially from IPCC CMEP-3 runs) to com-plement DRiCOMP and U.S. CLIVAR drought working groupresearch results, and that link drought research and societalneeds (e.g. the NIDIS program) are strongly encouraged.

U.S. CLIVAR OFFICE1717 Pennsylvania Avenue, NWSuite 250Washington, DC 20006

U.S. CLIVAR contributes to the CLIVAR Program and isa member of the World Climate Research Programme

U.S. CLIVAR

The results from DRiCOMP investigations and the U.S. CLI-VAR Drought Working Group will also be presented anddiscussed. The Workshop will feature focused oral sessionswith a mix of invited and submitted presentations, thematicposter sessions (including an evening reception), and adrought Town Hall discussion. The majority of contributedpapers will be presented in poster sessions.

The outcome of this year's workshop will be anassessment of our current understanding and ability to pre-dict drought, including identifying opportunities foradvances, and exploring new products to support regionaldecision making.

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