Seminar in Atmospheric and Oceanic Sciences
Seminar in Atmospheric and Oceanic Sciences ATOC 6020
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Date Created: 10/29/15
MultiSensor Satellite Retrievals of Sea Surface Temperature Gary A Wick NOAA Earth System Research Laboratory With contributions from many I Outllne MotivationBackground Input Products Issues in Merging SST Products Existing MultiSensor SST Products Summary NOAA ESRL Motivation Increasing demands on SST resolution and accuracy Passive microwave data is highly complementary to traditional infrared sources Infrared provides high resolution and high accuracy but is obscured by clouds Microwave provides coverage through non precipitating clouds but has coarser resolution and generally poorer accuracy Both sensors subject to different error sources NOAA ESRL GODAE HighResolution SST Pilot Project Provide rapidly and regularly distributed global multisensor highquality SST products at a fine spatial and temporal resolution Most promising solution to combine complementary infrared and passive microwave satellite measurements with quality controlled in situ observations from ships and buoys wwwghrsstpporg GHRSST PP GODAE High Reiululinn Sm Stirarr Trmpl39mrurr Film ijm NOAA ESRL The GHRSSTPP Strategy SST ystem quality control and uncertainty estimation Add i 39 quot ancillary M 39 7 quot o LL13 Input SST data SST Obs Analy5s of varied format Products tr 7 r 4 Products 5 amp With no errors dynamic 7 a ags SST gt Applications Slide courtesy Crai Donlon Met Office 5531 http www2hrsstDDor2 The Problem Observations from multiple satellites and sensors with different measurement times different effective measurement depths and different error sources These must be combined into a single consistent product with known accuracy characteristics KCBRK Temperature Pro les Wud 3 0 i 1 i I Dally Average lnsolallon 200 Wm2 ii xi 1 V A c on Depth m Dlumal Warming K o m 6 12 18 44 our NOAA ESRL Definition of SST T mpnalux u Skin SST Subskin SST SSTDepth Foundation SST Interface SST n lt page From C Donlon NOAA ESRL Input SST Products Infrared AVHRR AATSR MODIS GOES Imager SEVIRI MTSAT1R Microwave TMI AMSRE WindSat NOAA ESRL if a Key Blending Issues Correction for sensordependent retrieval errors and bias Effects of wind speed water vapor aerosols atmospheric stability etc Buoys used as accuracy reference Reference retrievals to common time and effective measurement depth Diurnal warming and skin layer effects Daily reference taken as foundation temperature Merging technique Treatment of different resolution Separate provision of diurnal variations NOAA ESRL f ReconCIIIng Sensor Errors 6 NOAA ESRL mm 939 WC Observed Differences Between Infrared and Microwave Products mm may Os Detailed comparisons between infrared and microwave SST products show complex spatial and temporal differences NOAA ESRL Error Characterization Approach Bias and rms error estimates derived from collocations with buoy data Determined dependence of uncertainties on sensor and environmental parameters Uncertainty estimates expressed through multidimensional lookup table Parameter combinations evaluated through reduction in sensorbuoy and sensorsensor differences NOAA ESRL mm uw we sf 39 AVHRR Uncertalnty Sources mm of b Nighttime Bias Dependence NLSST 200 307 i v i quot 7 307 7 257 7 257 7 207 7 207 7 Q Q E 157 7 E 157 7 107 7 7 107 7 n 57 57 0 i w i 0 0 4 1 2 3 1 2 3 Channel 4 7 5 Difference K Channel 4 7 5 Difference K From Castro et al 2008 NOAAESRLCUCKR 5W2 MAVHRR Uncertainty Sources 2 Bif s W IndSp eedP JLSST 2004 7 4 05 i 20 HHHHHHH EJTTTTTTTHHHL m 20 g 40 5 3 1 0 12 14 Wind Speed mls 1 2 3 AVHRR Channel 4 5 K From Castro et al 2008 nu ss m1 c Avlaiu 55 1 L5 Hvee JU Acre uAAwsms Gunman m 99 9111 Uch 11 j 1 Am Pro 7 WWW 39 a WM 7 1 H cu m e 0 Mommy wa W39 V Microwave Uncertalnty Sources Q NWENYoinf I Nighttime Mean Wind Speed Dependence of Difference AMSR 2004 Blas 13 7 i i i i i i i 7 39o 0 u AMSR Buoy SST Difference K 3 i i i i i 7 i i 7 7 7 7 13 gt Et r Ef SSTC 10 15 E 20 i i i i i i i 39 Z 6 8 10 12 14 Wind Speed ms TMI SST 199972000 TMIABnoy SST Difference deg C 2 3 74 5 Water Vaporg39gc m NOAAESRL CU CCAR 0 5 seaiAjr Tempemtnre Difference deg C 05 O4 03 02 0 00 DJ 01 03 04 05 K AMSRiE TsiTa qsiqa C 415 414 O3 01 01 0 DJ 02 03 04 05 k From Castro et al 2008 604 40 08 06 04 O2 30 02 04 06 08 Lo E x O 60 120 180 120 60 0 05 U4 O3 O2 4H 00 01 02 05 04 05 K NOAA ESRL ff 3 Impact of Bias Corrections AVHRR adjustments applied based on brightness temperature difference SST SZA and aerosol optical depth AMSRE adjustments based on wind speed water vapor SST and atmospheric stability Application of bias adjustments reduced differences between satellite products AMSR E SST AVHRR NLSSTJunE 2004 AMSR SST AVHRR NLSST June 2004 u iiiiiii Hume aaaaaaaaaaaaaaaaaaaaa m Before Bias 009 K After Bias 008 K Adjustment RMS 058 K Adjustment Rms o45K NOAA ESRL Wm f 2 Treatment of Diurnal Warming Each retrieval adjusted to foundation to remove any component of diurnal warming Multiple approaches Exclusion of observations at low wind speeds where warming expected Lookup tables as functions of wind speed and insolation Simplified parameterizations More detailed mixed layer models Challenge Must form estimates based solely on observations available from satellites NOAA ESRL Application of LookUp Tables Local time 135 Local time 135 Developed LUT from idealized and real forcing Applied different formulations m to replicate full model results 5 From idealized forcing tables using instantaneous wind speed overestimate warming Use of integrated wind speed and integrated insolation better replicate model physics Best results obtained with LUT derived from cruise forcing and expressed in terms of instantaneous wind speed and integrated insolation VimWm m whim Diurnall armlrg Kl Sandra Castro DVWG Orlando Overall LUT Representation Accuracy Best overall results again obtained from LUT for instantaneous wind speed and integrated insolation when derived from cruise forcings Errors resulting solely from LUT representation reach approximately 01 K in bias and 03 K in RMS Blas ard RMS K Hourly Model Bias and RMS Low WlHdS lnst U lnst Q U 6 lnst ul lnt c lntU lntQ quot HMS Real LUT lnstU lnt Q a 12 15 15 21 24 HuurLST Results compiled from diverse set of cruise observations and LUT errors in replicating full model determined as a function of local hour Sandra Caxtyo DVWG Orlando 5er Detailed Models for Diurna Wa rmlng Performance of multiple detailed diurnal warming models being evaluated in GHRSST Diurnal Variability Working Group Kantha and Clayson 1995 second moment turbulence closure Fairall et al 1996 simplified bulk warm layer model Global Ocean Turbulence Model GOTM Profiles in Ocean Surface Heating POSH Gentemann 2007 NOAA ESRL c 5 g u m E 0 6391 0 Wm of 5 Amos hfw Bias and RMS K o w 539 Application of New Blended Model 4 A 54 s 9 Full KanthaClayson warming model modified to blend two turbulence schemes Results show improved ability to simulate both cruise and satellite observations of diurnal warming Underlying model accuracy of lt 01 K bias and 1 K rms Hourly Model Bias and HMS Low Winds Baseline Enhanced Mixing 39 Blended 39 21 9 12 15 Hour LST Celsius Skin Layer Effects Nighttime Skin Layer Model 200372004 Assessed M application of AT 015 047 EXP038 u skin layer model with satellite data Developed revised t with Uncertainty 01 K ClRlMS AT T D 4 a m 0 2 A New Wind peej ms observations Skin layer 30 ltgt O estimates 0396 E incorporated in E 3 3 MW L2P data DZ i E on E 704 E O 2 4 l2 i4 8 5le Wind Speed ms I From S Castro NOAA ESRL MultiSensor Analyzed SST Products Many new products now available Most based on optimal interpolation Wide differences in products combined resolution and regions NOAA ESRL Next Generamen SST Objective Analysis I Merged SST x Created by Hiroshi Kawamura Tohoku University Japan httpWWWoceancaostohokuacj pNadeossst EVUW g W IDDW AA y Anomaly SST Impact from Hurricane Katrina T MJL H anc jar MQAHA J WOperational SST amp Sea Ice AnalySIs NCOF Met Office Daily 120 56km global SST analysis Analysis of the foundation SST pre dawn or below the diurnal warm layer Blend of data sources using satellite microwave amp IR and in situ data Using many GHRSST data products Almost all Medspiration products Now running daily operationally Using a variational scheme with persistence based background Uses sea ice analysis performed by EUMETSAT OSlSAF metno DMI 20070419 UKMKLUUH ndjLU iiiiiiii MeTumcgaam 39 E Vo2 m 7m39pp Sample analysis for 19 Apr 2007 Slide courtesy John Stark Met Of ce wwwncofgovuk BoM Regional Australian MultiSensor SST Analysis System BLUEIinkgt Ocean Furenasling Australia V10 Operational 13 Jun 2007 gt RT input to BoM NWP models V11 Operational 26 Oct 2007 Depth Foundation Resolution Daily 112 Domain 60 E 170 W 20 N 70 S Observation correlation length scale 12 km Background correlation length scale 20 km BGF Combination of previous day s RAMSSA and previous BoM weekly global SSTblend analysis Based on legacy BoM optimal interpolation regional SST analysis system Data Inputs 7 1 km HRPT AVHRR NCAA17 18 7 9 km NESDIS GAC AVHRR NCAA17 18 METOPA 7 25 km AMSRE Aqua L2P 7 16 AATSR EnviSat 7 Buoy and ship obs GT8 7 112 NCEP ice edge analyses Latitude N RAMSSA ssrma Analysis low zomizus 750 so mu Mn izo mo Ho iso iso we mo Longitude E Daily foundation SST analyses available by 0330 UT as netCDF L4 les from and Slide courtesy Helen Beggs BoM Multisensor L3L4 products MERSEA Products Global Monitoran yquot r nnnnnnnnnnn Szurhy g IfremerODYSSEA onvsszn Mumnnw L 06 Jun ma Global ODYS SEA analysis daily 01o AATSR NOAA LACGAC 1718 SEVIRI AMSRE TMI METOP GOES 1112 nearreal u time global multisensor L3 Atlantic analysis daily 005quot AATSR NOAA LACGAC 1718 SEVIRI AMSRE TMI METOP nearreal time global analysis L4 Mediterranean analysis daily 116O IR multisensor near realtime and delayed mode Mediterranean analysis L4 Slide courtesy JeanFrancois Piolle lfremer 9th June 2008 GHRSST9 PerrosGuirec I SST Analyses1 January 2007 RSS OI 111 grid NCEP RTGHD 112 grid UK OSTIA 120 grid NCDC Daily OI AMSR AVHRR 14 grid This is a daily average What spatial scales are justified SST O 1 JAN2007 4 gts 84W 82W BOW 78W 76W 74w 72w 70W 68W ssw Daily 0 1 Global MultiProduct L4 Ensemble 55de K Time Optimal way forward preserves regional autonomy maximises benefits to user community Requires a framework to deliver the ensemble product L4 format descriptor Stimulates better products and scientificproduction interactions GMPE Verification Intercomparisons Uncertainty estimation and confidence building NRT climate monitoring GODAE High Rmmmn Sea Surface Tempmrm mot ham 39 Slide courtesy John Stark Met Office gm 1 httpwwwghrsstDDor2 MetOffIce Users Seasonal forecasting I NinoI 3 from Enstlemble i1 bold 2 bsua 39 lugdSSt Z urn390 r l39SSll lW I39SSHWK39H39 1 AVHRROI fnmoc I gtlt 5 I w 395 T Z 39 E U 0 E 2 O 51 s a I z F i 2 I I I I I l I I l I I I gt I May lV39Iay 2007 2008 Slide courtesy John Stark Met Office http www2hrsstDDor2 600w Hing RemIIIquII Sea Surth TEquot Em are a m 2139 f 2 2 a quot7 mm of a Summary The complementary nature of infrared and microwave data enable exciting new SST products Significant issues include compensating for different error characteristics different measurement times and different effective measurement depths Many new multisensor analyzed SST products are now available Full intercomparison and accuracy evaluation of these products IS now required NOAA ESRL iwaAVHRR Uncertainty Sources 3 was of Cloud Proximity Dependence NLSST 2004 NLSST Buoy SST leference K o o o O f T 3 4 E 3 4 F 3 4 3 3 4 3 3 E 41 44 4 44 44 5 10 15 Number of Cloud Free Retn39evals Within 20 km NOAA ESRL CU CCAR MERIDIONAL OVERTURNING CIRCULATION SOME BASICS AND ITS MULTI DECADAL VARIABILITY Gokhan Danabasoglu NaTional CenTer39 for39 ATmospher39ic Research OUTLINE Describe Ther39mohaline and meridional over Turning circulaTions MuITidecadal variabiliTy in The Nor39Th ATlanTic as depicTed by The ATlanTic Meridional Over Turning CirculaTion AMOC Examples of climaTe impacTs and poTenTial pr39edicTabiliTy ResulTs from The NCAR CommuniTy ClimaTe SysTem Model CCSM3 simulaTions Summary WHAT IS THERMOHALINE CIRCULATION THC IT is ThaT parT of The ocean circuIaTion which is driven by densiTy differences as opposed To wind and Tides Because The ocean densiTy is a funcTion of TemperaTure Thermo and saliniTy haline This circuIaTion is referred To as The Themohaline circuIaTion and indicaTes a driving mechanism These densiTy differences are primarily caused by surface fluxes of heaT and freshwaTer and subsequenT inTerior mixing The oceanic densiTy disTribuTion is iTsef affecTed by The currenTs and associaTed mixing Thermohaline and wind driven currenTs inTeracT wiTh each oTher and Therefore cannoT be Truly separaTed THC IS NOT AN OBSERVATIONALLY MEASURABLE QUANTITY THERMOHALINE CIRCULA IION PATHWAYS CONVEYOR BELTquot mammal While Temperature ucfs as The driver salinity provides The break WHAT IS MERIDIONAL OVERTURNING CIRCULATION MOC IT is a relaTed field referring To a sTreamfuncTion on The depTh laTiTude plane IT can be obTained from 0 east II yzt f dz f Vx yztdx Z west where x longiTudinal zonal direcTion ve easTwards y laTiTudinal meridional direcTion ve norThwards z heighT ve upwards T Time V meridional velociTy componenT This field is ofTen used in The modeling communiTy because iT is easy To diagnose MOC INCLUDES WINDDRIVEN CIRCULATION MERIDIONAL OVERTURNING CIRCULATION n WIND DRIVEN GLOBAL E K 3 NORTH ATLANTIC DEEP WATER ATLANTIC E NADW E ANTARCTLC D WATER Units Sverdrup SV 106 m3 squot DEPTH km MERIDIONAL OVERTURNING CIRCULA39IION Depfh Lufifude Plane Densify Lufifude Plane OCEANIC NORTHWARD HEAT TRANSPORT 25 l l I I 20 ICE Derived Tctol Fcciflc 1 u quotnth m Ji39J r Heat Transpa PW Heat Transport PW BO 50 40 20 Q 20 40 60 BO 395 Lafiiude 39N Trenber rh and Caron 2001 SEA SURFACE TEMPERATURE SEA ICE CONCENTRA39IION azu A 27w 7213000 la 1mm n zoo 39c WHAT DRIVES THC MOC MECHANISM II WesTerly winds over The SouThern Ocean No meridional flow can be supporTed aT inTermediaTe depThs aT The aTiTude band of The Drake Passage due To lack of Topographic barriers ThaT can supporT easTwesT pressure gradienTs l I high densi ry SOUTH EQUATOR NORTH Winds direchy supply energy Many coupled general circulafion models CGCMS exhibif mulfidecadal or longer Time scale 20 100 year39s variabilify in Their AMOCS Time seriesof the 39 unmaM presentday I 39 I 200 400 600 EDD moo Bryan 239 a 2006 J 5mm HEAT CONTENT CHANGES beTween mid19903 and mid19503 CCSM3 20 rh CenTury simulaTions 1870 con rr39ol in regr39a rion 0 30 I I l O A O 25 53 g I E 020 O a I Q I 3 E 01 5 L g 3 E O Q m 010 gr g 0 OS D Z E L Q00 L Levi rus e rl al 2005 obger39va rional es ma res 0300m 0 700m 05000m Gen r e r al 2006 J Clima re CHANGE IN SOME FIELDS BETWEEN HIGH AND LOW AMOC PERIODS IN THE GFDL CM21 CONTROL SIMULATION Rainfall cm day39l Ver rical shear of zonal wind m 3391 mm m munmm 23 2007 a 2 N30 300 WE 01753370021 0000 10 01753370026 0000 NOLEAP TTME 01753370021 0000 to OTESEFEDOZG 0000 NOLEAP LATITUDE LATITUDE 40quotW Oquot LONGTTUD E 40quotW 0 7 LONGTTUDE 8640DELTAL22226AVE 1DELTAL2226AVE Vertical shear compu fed for 300 hPa 850 hPa Tom Delwor rh AMOC IN THE 20 rh CENTURY ENSEMBLE INTEGRATIONS Mox NH A ontic Overtummg 3 pt smooth A Mm bBOOEOg E301 J M O Q g 18 b30030b ESOW bEOVOBOfES OW 350 400 450 500 550 6 Year O O Mox NH A omtic Overturnmg 3 pt smooth ws LN UT O 07 O O Frank Bryan Time series of AMOC maximum from 5 members of a 30 member39 ensemble of ccsms T42x1 AlB scenario simulations i i i i i 2000 2010 2020 2030 2040 2050 2060 YEAR 20002007 year trend in annual AMOC timeseries 20072016 year trend in annual AMOC timeseries Frequency 9 9 a 8 7 7 6 gt 6 U C 5 Cl 5 3 D39 4 i 9 4 LL 3 3 2 I 2 1 I 1 II 20162025 year trend in annual AMOE timeseries 54321o19 14 012345 5v l39ime in l39er val 8 7 gt 6 O C a 5 3 039 93 4 7 7 LL 3 2 1 Max MOC 25 NSV TIME SERIES OF NORTH ATLANTIC MOC AT 25 N 25 0 Br deneT L 2005 Y 0 I 2000 ECCO 50y 444444 ECCO4GODAE 444444 INGV 1990 ATLANTIC MUL39II DECADAL OSCILLA39I39JION AMO AMO INDEX AMO INDEX SST C I I x x v x meo moo 1920 mm 950 1950 2000 Trenberth Slt Shea 2006 Sutton Slt Hudson 2005 QUESTIONS Since Delwor39Th eT al 1993 sTudy There is a broad consensus ThaT The densiTy anomalies in The sinking regionquot of The AMOC dr39ives This var39iabiliTy However39 many fundamenTal quesTions sTi remain largely unanswered mechanism naTur39e of This mode role of aTmospheric var39iabiliTy robusTness of mechanism Timescale implicaTions for39 iniTiaIizaTion and pr39edicTabiliTy implicaTions for our assessmenTs of 20 rh cenTury fuTure scenar39io eTc cimaTes AMOC IN CCSMS T85gtlt1 RESOLUTI IMUL AMOC MAXIMUM TIME SERIES TION ON PRESENTDAY CONTROL sv a 051m m E E E s 0 mm mm am new 2D Dunabasoglu 2003 J Climate 2039s 0 2w 4cm SEI39N POWER SPECTRUM am a m mowch weary SEA SURFACE TEMPERATURE SST 337 mm varl243 1531 gem IIME SIERIES39 150 200 250 300 350 450 455 YEAR AM DC lagging AMOC leading 15 10 5 5 IO 15 0 LAD year NORTHSOUTH GYRE BOUNDARY FLUCTUATION and WIND STRESS CURL SIMULTANEOUS REGRESSION MARCH MEAN BOUNDARY LAYER DEPTH BLD a om var444 DENSITY REGRESSIONS WITH AMOC PCl UME SERIES a LAERADOR SEA REG ON 004 a A a 04127 1 f E 4102 E BLD and 70m AMOC aggmg AMOC eadmg AMOC 4n 75 5 P61 Ti me series as 7m 7 5 u 5 m 5 was WIND STRESS CURL misc E0ff1 gu0r257 j ISQHEOH POWER SEECTRUM 9570 I 39 99 1 39 I 001 010 FREOUENCY 1year New POWER SPEC TRUM l 95 199 39I 39 501 519 FREQUENCY 1quotyeur1l SUMMARY AlThough They refer To differenT concest THC and MOC are ofTen used as synonyms There are no longTerm observaTionaI esTimaTes of The MOC TransporT Many CGCMs exhibiT mulTidecadal or longer Time scale variabiIiTy in Their AMOCs This variabiliTy is usually associaTed wiTh variaTions in The ocean heaT TransporT ocean heaT conTenT NorTh ATIanTic SSTs eg AMO climaTe changes over NorTh America WesTern Europe and Africa There are indicaTions of poTenTiaI predicTabiliTy IN CCSM3 T85x1 RESOLUTION PRESENTDAI SIMULATION This mulTidecadal var39iabiliTy shows r39aTher39 lar39ge ampliTudes in boTh AMOC and SST Comparisons of The aTTer wiTh observaTions indicaTe ThaT neiTher39 The paTTern nor39 The magniTude of The SST anomalies is realisTic However39 The role of The meansTaTe biases remains unclear39 These SST anomalies are cr39eaTed by The flucTuaTions of The subTropical subpoar39 gyr39e boundary driven by small scale WSC anomalies The pr39esenT r39esulTs do noT suppor39T an ocean mode ThaT relies on a phase lagged r39elaTionship beTween Temper39aTur39e and saliniTy in Their39 conTribuTions To The ToTa densiTy in The model39s associaTed deep waTer39 for39maTion r39egion ATmospher39ic var39iabiliTy associaTed wiTh The model39s NAO appear39s To play a pr39ominenT role in mainTaining This var39iabiliTy IT is likely ThaT The processes seTTing The 21year Time scale have oceanic or39igins ATLANTIC NORTHWARD HEAT TRANSPORT NHT PW AC yccrs a TVS MEAN Nt T 12 103 083 06 D 09 00 3ng vls yo 310 RESLRESS ON MOC leaping quot 25quot 39quot39 V 4 quot quot39 equot l 4 V VVIV rvv PW AMOC PCl variance LABRADOR SEA ADVECTJIVE HEAT FLUX REGRESSIONS WITH AMOC PCl TIME SERIES WOO logging AMOC leading N a w sow 40w 20w u 20 v nwpm MEAN SST BIAS OBS Levi rus e r 0 1998 Xx S reele e r al 2001 BA ROTROPIC STREAMFUNCTION iSf v39e Yeager and Markus Jochum NCJAR 60 W 30quotW ssmA C From a Fully couped 39CC S M315 VZO fh century simula ion OUTLINE Expected Features of fhe Nor rh A r lan r ilc Circulation The Gulf S r ream in the 1 POP model A Ocean only HindCias r B Oceanicehin39d casf C Fully coupled The connec rion be rween rhe rhermOhaline circula rion and the gyre circulation vgt rhe in uence of rhe deep wes rern boundary curren r DWBC Wha r se rs rhe s rren rh of rhe DWB C Gyre Spintup and the role of mixed boundary condi rion Feedbacks Wafer mass transformation in the Subpolar seas Conclusion m 132 A Burexroplc Slreamlnnclion am ifs3 7 KW Q m aaj f m 7w 59 40 EID 25 20 45 l 5 o smlszozsacwsoeu Mmmps gamma E 111 3 0 Maria w i F m ES jg 1off 1 F W a w o m f xmm 1mm k umm cc W r i r EK39EW o wmm F M Q W W W WW 0 nglm ig M mm w i mm m 3199 32QXQQ 5M am N gr WEE W LevitusTEMPl755rn 9 3957 U 1 Y I71e00to 2059401 by 100 4990 I Western Boundary TransPor rs SCho r r e r al 2004 2006i 0 Deep WeSfern Boundary CurremL DWBC and Norfh Aflam ic CurremL NAC 43 VN DWBC ow gt 10 SV 06 gt 2768 kgm3 NAC ow gt100 Sv 9 igni1 1camL soufhward franspor r below IOOOm cur re mL speed 10 cms DWBC 60 cms NA C PLOP 1 Experiments oceanOnly hi ndcas r bulk lux Forcing with prescfibed 19492006 atmosphere diagnostic sea ice model 9 prescribes daily observed LSiSMI ice ex renf r 84 iceocean rhermjohaline uxes based on ocean melfr po ren ri39al B coupled oceanice Ah i ndcasjl bulk ux Forcing wi r h prescriber 19492006 ai rmosphe re39 CICE model a Freely evolving sea 39ice dynamics thermodynamics Fully coupled CCSM35 20 1 century simula rion COREvZ Large and Yeager 2008 C Fully coupled s 175m WQWEWD So m 4 by 3 WW g9 mm 70 5 mn IMum a mmch wwegc mm a m 43mm a meow WodegC zan u Jzu39 w ruecvoom Mammy azupsu D m Hszmom Emewohy azupsu W m g m As 3 54 mums 3 may 4w 5 n mm 7022 om zan m mm M so m m 0 H mm gt0 5w 4 urn urn 750 mm 4 3w 4mm MW Wage WW 533am WW WW WW 1m Mm ans WWW mg m m m am am om 5w om 4 I mm mm 7 2 quot 2quot 3w 3w u Jzu39 w ruecvoom Mammy azupsu u Jzu39 w Hosmom Mmewohy 020525 D m Hszmom Emewohy azupsu grams 0 oi V75V5m 5 SaHn39Ry psu m 17mm I r m m V am mm V39a w 3 gm x wwm 63 W g W Wm Q 6 l NALd h ta d m i39EZ39CEL a magmmwmmm 3 ugmwmwm c defuchmenl nart wu d hmnsar as m A ntic rlge W g m lt Wuhwm Na 20 Zhang 82 Va lliis 2007 show that a s rrong downslope DWBtC easf of rhe Grand Banks induces bio r fom Vor rex s rre rching which enhances rhe s rreng rhs 0F fhe NRG and NAC wB z ugVH is very large and negafiVe Where us and VH are both large and aligned Grand Banks shelF Vertical lyin regra red vorticity equa om Maw8x f5wB WE lt O 2 increase in local no r fhward baro r rop ic Flow NA C 11 1pw wa dxquot wB lt 0 gt basin i n regral contribu res to 11 lt o NR6 WE WWQQWW WWW Ln 32039 30539 WE WWQQWW WWW Ln 32039 30539 11 xm V 1M Asfw w 4739w as w 2m wa ms 3419 n 3943 a 4A 1531 N man man NR 1 H mun mun Depth m mun out WELmsgl 4911 39743 mam mum w Mama by 500mm H QMJSAV 39743 a L m man 2 a as mm a mm mm mu n mu n 500 u m n ma n 200 n ma u u u Depth 710 B S 5 8 4mm Improved Simulation 0F the North Atlantic in a low viscosity noneddy resolving ocean model BSF s rronger and partial lya r rached NAC stronger NRG reduced upper ocean lem pera r u re and salin ij ry bias is closely lied lo increased DW BC s r reng rh and density The connec rions be rween rhe DWBC and rhe Nor rh A rlan ric gyre circula rion appear ro be exPlained by bo r rom 39vor rex slrefrcihi ng associa redquotwi39 rh a s rrong downslope DWBC Zhang and Vallis 2007 39Wha r defermines DIWBC sa rreng rh 39in We model lam Wm mm we in 152 maniacs mimemjemm A omtmrwwm I96 MIMI am WM I IIIIIIIIIIEr 2 1 05 urFace bias years 54 58 Spurious positive surface bias in mung FreShenmg the subpolar seas associated with erroneous northward transports I advection errors generate positive SSD bias re ecting SSA I and retreat oF winter ice edge in B in the mm mm Labrador 560 54424 a 2 3 4 5 s 4312 416 o 05 12 15 42 os 0 06 12 aaurc Larger bias in B is an artifact oF spurious melt uxes in A along Labrador Coast ice shelF B 1111111111311 mm 65745724012 s 4 5 5 431205 0 05123 42 415 o 03 12 Mixed The rm ohalizne Boundary Condifi goin39s dQAdsT Wr E C Strong restoring of SST with we saw 60w 1on on restoring of 55 Mixed boundary condifio39ns Forcing wiffh bulk ux formulae WhitHuSQ m de l SST results in s f39ffong efffe c rive damping of model SQS T error 310 Wm Ci hroqg39hou Norfh Aa1anic There is no ux Feedback on 55 The only damping of 55 emr cfo m egs me an arlfii cidl weak restoring term VP 50mg4 Excess nor rhWard h eiaffs ialf ranspof gives rise 0 1 piosifi ve MOC feedback quot Atlantic M00 Gr39i39f es39 al 2008quot 1 bafhymefry Some Mefri cs 0 Regional ayerages Labrador Sea Nor rh A r lan cquot Norwegian Sea baro rropic heat salt and mass rranspdr rs across 48 N mass ranspor rs across 43 N soow MOW DWBC 39ampNA bo r rom veloci ry WE sou rheas r oFL rhe Grand Banks NR6 s rreng rh 9 MOCVs rreng rh maximum nor rh oFLZBPN below 460m am am am A ocean only Tlme evoluhon B ocean ice 0 Rise in Lab Sea surface bias in B due lo advecfion error regional average bias in A sfays low inifially due lo spurious melf uXes Warm sall39y Wesl39 Greenland currenl wafer enhances conveclive aclivily wilhin rsf decade in bofh simulafions Infially small DWBC fransporf near observed levels achieved in B afler 10 years Labrador coasf ice edge prevenfs DWBC increase in A wan Forrng Year A ocean only B ocean ice Time evolu on 0 Bulk of DWBC fransporf in B denser fhan 00278 kgms dense DWBC is minimal in A o Spinup of fhe dense DWBC in B reverses fhe weakening frend in offshore NAC fransporf 0 High correlafion befween DWBC NAC and B magnifude of hindcasf inferannual and inferdecadal MOC variafions is sfrongly dependenf on boundary condifion choices wv 13 ampW w i950 use me wan was man Forrng Year Time evolu on AEQ w so 950 A ocean only B ocean ice Bl ocean ice s rrong salini ry res roring BZ ocean ice repeal annual Forcing 0 Adding slrong salinily resloring lo B removes lhe mixed boundary condilion Feedback SSTA is minimized as well as SSSA lhe Labrador coasl ice edge is relained deep mixing is damped and lhe DWBC is 05 0 Desirable variabilily is also losl eg lhe Greal Salinily Anomalyquot in lhe ale 196039s Dickson el al 1988 0 Spurious ice mell in A has lhe eFFecl of a lemperaluresalinily resl oring Flux i explains much of lhe difference belween A and B spinup Gyre spinup highligh rs fher role 0F the mixed boundary condi ri on Feedback in they THC spiln up in B wifh CQ39rrela red GS piath 39v ariafri o ns n How and where is DWBJC water generated 4 I m mm W We W To al mam W f mamm m ln e gamma 033239 meb i igav as e eess hermal Ibge 71 r1271uarer47202 4 5 510121415 Surface Diapycnal TransformaTion raTe Sv ToTal Spear and Tzipennan 1992 Themquot Large and Nurser 20m Hallne Haline MelT Norm moms Nnmcg mn m I all subpolar regions show 30 l excess posiTive Thermal 25 a w TransformaTion aT Too high I a 5 A densiTy in boTh A and B m 5 Thermal ux dominaTes LJ L M dense waTer FormaTion gt haline uxes melT 3D m dominaTe lighT waTer 25 f a w FormaTion 5 u 5 B EssenTial difference 2 2 A if beTween A and B is in The v r a f Labrador Sea T 7 7 7 7 Times Too large in B 3 n W Times Too large in A 25 5 0 2 8 A was hence The sTrong dense M 5 DWBC in B 5 2 W 72 25 ES 27 2H 72 25 25 27 25 2 7 25 25 27 26 41 mm mm v Wm Improved Simulation oF the North Atlantic in a low Viscosity n oneeddy resoIVing ocean model BSF stronger and partiallyattached NAC stronger NRG reduced upper ocean temperature and salinity biaS is closely tied to increased DW BC strength and den Sity The connections between the DWBC and the North Atlantic gyre circulation appear to be explained by bottom Vortex stretCJhing asSociatedwilth a strong downSIope DWBC along the Grand Banks sbevlFWlZQtianig and Vallis 200739 The strength of the DWBICfis related to winter buoyancy loss in the Labrador Sea In pres cribed atmosphere con gurations with bulk ux Forcing and Weak salinity restoring mixed th ermohaline boundary condition Feedbacks exacerbate the model tendency to transport too much warm salty subtropical water into ther SMbPOIdr seas The result is excessive thermal transformation oF overly dense surFace water particularly in the Labrador Sea and THC spinup The Feedback is strengthened in oceanice con gurations due to ice edge retreat Spuripus airsea density Flux it is weakened in oceanonly con gurations due to spurious melt ux Strong salinity restoring dam ps un physical boundary condition Feedbacks but this d065 notquot improve the delity OF hindC Sf North Atlanticvariability Unanswered questions Why is unrealistic surface water mass transformation required to generate realistic DWBC transport What causes the initial NAC detachment From the Grand Banks ShelF Would improved initial conditions strong DWBC FloW prevent NAG detachment What mechanism maintains the pressure gradients in the NW Corner region Wq rer mass Forma rion Surface Densiy ux DO kgmZs where Ha rear h 4 n New Fr Maw ux SSS pa 1000 Iltgvn3cP 399639Jk gKtu 494ap 3T 35 pquotBp5539 Surface Diapycnal ransfor39ma onltraeT Sv Wafer mass accumulafion rafe Sv Speg r and Tziperman 1992 Largeand Nyurser 2001 Meridional rranspor r across 48 N Simula on year Muss 5v Sa t Svgkg Heat m 01 s 73w 5 mo 73 f m a 0 0 mus 05 m 5 4m m we rm 5 mo 45 m as o o mus 05 5 4m 390 m ms 7m 5 mo 7 m as o o mus 05 m 5 4m us me 735 5 we 77 mm 77 o 39 o mus 05 5 4m 390 m 750 750 4m 73039 720 4v a few 75039 740 7w 72039 w v 750 750 74039 7w 7w 40 9 Wm WM Wm a1 ww m lb fwg 3mm y 42 415 o 05 12 A ocean only Time evolu on e 2 Bl ocean ice s rrong salini ry res roring BZ ocean ice repea r annual Forcing A NA M j R MN A I w qu j 39 J v W3 1 waj v VN v 34 K7AQa gq7g 30 HA t UATVLAVQA ma sss qwl 2 AYT Qamp M w v was man wan was man was man we wan Forrmg Year Forrmg Year 1 gn V L k 392 c39en fravl Lab S39AJg39xi ng Lab S 4 a39norfhe39rn LabJSea gt Back North Auan c mummy Sea Numgm Sen 1a a w a A 1 5 A 2 k 4 N a 5 j E z k m a m a n 5 j was z 25 25 27 23 7 25 25 27 23 7 25 26 27 2s a kgm39 a kgrm a Van9 North Amn c mmam Sea Numeg mn Sea 3 1a 1 North Auan c mummy Sea Numeg mn Sen m a 0 a 5 A o I JL m a 5 E I K m H 5 was k z 25 25 27 23 7 25 25 27 23 z 7 25 26 27 2s a kgm39 17VqMv a Van9 mm mm mm 5 quotWm 5m w 5 52 B3 NSEF rned OFF asr g3j19 1 39743 Weaker subpolarNRG Weakerlighfer DWBC very anemic NAC uu Jzu39 eavssum m Hamm by m 5n Higher T39 mm m BB Normal Year Forcing asr g3j19 1 39743 Weaker subpolarNRG Weakerlighfer DWBC Shallow NAC Higher T39 msql 1911 39 43 Amaqu v B40 40 verficallevels 3100 100 verfical levels SF 65 amum bb 29mm by bus 5n mean 7L7 1 ESFgSj 19 1dI6 2 m as guggm 39743 r 229 729 o soo JDD39 Jzu39 m 400 fleaum m mum by bus 5n 5u o 30039 12039 30 asseWI to 34e01 by 5700 3v 4419qu to 414elt11 by 500 3v 10039 12039 w Qw CMDW cz mean 22 mm BF 9351901 39743 D as g351g12 39743 soul azu zqacuv m aimm by 500 5v CEVSSCMJI to 435am by 500 Sn mnbm 10 905am by 500 Sv man H175 mono HMXL m 934319 1e vs 20 WWW mm mm 565ewuw mummy mum nun L 30039 32039 ZEEV39 JDD 32039 W E lsA nuoxc 541D by W um memento msgmny 50mm auu39 leuemum 647eDzhy swam ll hw m ngwzay soaum high viscosify asr g3j19 1 5720 0 Drama c redu Hon oF gyre sfrengfhs 0 GS Fails 0 separafe by DWBC nonexishamL TEMP anam V755m 93549 m U640 D TEMP unam 175m QMJSAVe 5720 w W 0 N 7 0 Low T39 For he wro 9 reason 1
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