Identification of the ITCZ Using Ocean Vector Wind Fields ... · PDF fileIdentification of the...
Transcript of Identification of the ITCZ Using Ocean Vector Wind Fields ... · PDF fileIdentification of the...
IdentificationoftheITCZUsingOceanVectorWindFieldsDuringSPURS-2
AaronC.Paget&JamesB.EdsonDepartmentofMarineSciences,UniversityofConnecticut
InternationalOceanVectorWindsScienceTeamMeeting2-4May2017,LaJolla,California
ImageSource:ShadesofBlue,SPURS-2NotesfromtheField
Episode:SPURS-IITHEFATEOFFRESHWATER
NASASPURS-2(SalinityProcessesintheUpperOceanRegionalStudy-2)Tostudythefateoffreshwater(Precipitation)• IntheIntertropicalConvergenceZone(ITCZ)• Cruisedates:August– September2016• WHOIBuoyMooringat10°N,125°W• Atmosphereandoceanobservation• Otherresourcesdeployedaswell
AtmosphericSoundings
DivergenceTerm(negativeconvergence)
𝜕𝑊𝜕𝑡 +
𝜕(𝑢𝑊)𝜕𝑥 +
𝜕(𝑣𝑊)𝜕𝑦 = 𝐸 − 𝑃
Dominguezetal.2006
Small
Wistheprecipitable watervaporintheatmospherePisprecipitationEisEvaporationu,v arethemoisture-weightedvelocitiesthatcontainboththemean
andeddycomponentsforzonalandmeridionalwindspeeds
Basicwatervaporconservationrecyclingmodel
Convergenceisrelatedtoprecipitation
MoistAir
NorthSouth TheoreticalITCZintheSPURS-2Region
Evaporation Evaporation
Condensation
PacificOcean
NearSurfaceWindNearSurfaceWindConvergence
Divergence
Can10-mwindsbeusedtoapproximatesurfaceconvergence?
GPCPPrecipitationandCCMPWind(V1)Convergence(Daily,1°)
ForSPURS-2analysisregion(30°N– 10°S,145°W– 100°W)(1996-2011)• 60%ofthePrecipitationrateis0mm/day
65
4
32
10
x105 x105
-10-4 010-4 s-1
2.5
2
1.5
1
0.5
0-10-4 010-4 s-1
ConvergentDivergent ConvergentDivergent
Coun
t
Coun
t
CCMP(Precip =0)* CCMP(Precip >0)
0 20 40 60 80mmday-1
106
104
102
100
GPCPPrecipitation
Coun
t *Duringsubsidence,weexpectsurfacedivergenceandnorain
AnalysisDomain
CorrelationCoefficients*Daily– -0.477day– -0.6414day– -0.70Monthly– -0.743Month– -0.78
*allsignificantcorrelations
MedianMonthlyPrecipitationRateforGPCP(1996-2016)15
10
5
0
mm/day
GaussianCurveFittoPrecipitationalong125WforSeptember
2σ
1σ
GaussianCurveGPCPdata
Latitude
𝑦 =1
𝜎 2𝜋� 𝑒5(657)89:8
MedianMonthlyProbabilityDistributionFunction(PDF)ofPrecipitation(GPCP1996-2016) MaximumNorthwardVelocity
0.42Degrees/Month
MaximumSouthwardVelocity0.62Degrees/Month
ITCZWidth(2σ)Δ6° – Δ8° Latitude
20
15
10
5
0
-5
Latitud
e
JanFebMarAprMayJunJulAugSepOctNovDec
Max +/- σ +/- 2σ
ITCZGuidance:• Centeredabout8°N
+/- 1° – 2° Latitude• Widthof6° – 8°
Along125°W
WindSat ASCAT
Convergenceof10-mWindsfromWindSat andASCAT23August2016– Swaths
GPCPTotalPrecipitationPeakat11.5°N
σ=2.85Range:8.6°N– 14.4°N(1σ)
5.8°N– 17.2°N(2σ)
QuikSCAT Convergent9°N– 16°N
During14dayperiod,ITCZshiftingNorth
QuikSCAT L3– 14Day(0.25x0.25)duringAugust200825
20
15
10
5
0
-5
25
20
15
10
5
0
-5
-145-135-125-115-105
-145-135-125-115-105
-50 510152025
-50 510152025
10-4 s-1
0
-10-4
mm25
20
15
10
5
0
4
2
0
-2
-4
-6
-8
x10-5 s-1
0.12
0.08
0.04
0
Median
Total
Divergence
Convergence
GPCPTotalPrecipitationPeakat10.4°N
σ=3.2Range:7.2°N– 13.6°N(1σ)
4.0°N– 16.8°N(2σ)
QuikSCAT Convergent8°N– 15°N
During28dayperiod,ITCZshiftingNorth
QuikSCAT L3– 28Day(0.5°x0.5°)duringAugust200825
20
15
10
5
0
-5
25
20
15
10
5
0
-5
-145-135-125-115-105
-145-135-125-115-105
-50 510152025
-50 510152025
10-4 s-1
0
-10-4
mm500
400
300
200
100
0
2
1
0
-1
-2
x10-5 s-1
0.15
0.1
0.05
0
Divergence
Convergence
PreliminaryConclusions• PrecipitationandConvergencearesignificantly
correlatedondaily– seasonaltimescales
• Onamonthlytimescale,theprecipitationhasanormaldistributionNorthtoSouthintheSPURS-2region
• PrecipitationmaximummeandersNorthandSouthatarateofupto+/- 0.5° month-1
• 10-mwindconvergencedoesnotperfectlymatchtheprecipitationpattern
• Weneedtoconsiderevaporationandatmosphericmoistureinourbalance
• Themoisturebudgetrequiresverticallyintegratedwinds– frommodels?- MERRA-2,ERA-Interim,NCEP-NCAR
• SPURS-2soundingsaretoocoarseforthebudget,butcanbeusedtovalidatemodels
• MoreinformationwillbesharedattheSalinityWorkshopatWHOI(22-26May)
FuturePlans
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