Air – Sea Measurements from Ships:Fluxes, Time Series, Remote Sensing

Dr. Jeff HareCIRES – University of Coloradoand NOAA Earth Systems Research Lab

jeff.hare@noaa.gov

CSU ATS 650 Measurements Systems and Theory

Fasullo and Trenberth, J.Clim. 2008

SI = Solar InsulationASR = Absorbed SolarOLR = Outgoing LongwaveFS = Net Surface FluxRT = Net RadiationFA = Energy transport (atm)

NOAA Ship Ronald H. Brown

Turbulent fluxes (direct covariance)

Latent heat ρLv <w’q’> [W/m2]Sensible heat ρCp <w’T’> [W/m2]Momentum ρ <u’w’> [N/m2]Gas (etc) <w’c’>

Instruments:Sonic anemometer (wind, temperature)Infrared gas analyzer (humidity, CO2, etc)Motion (roll, pitch, yaw, heave, surge, sway)GPS/Compass/Doppler speed

t1 = L / (c + v) ; t2 = L / (c - v); v = 0.5 L (1/t1 – 1/t2); c = 0.5 L (1/t1 + 1/t2);Ts = c2 / 403; T = Ts / (1 + 0.32 e / p)

L = path lengtht = time of flightc = speed of soundv = wind velocityT = temperatureTs = “virtual” tempp = pressuree = water vapor

pressure

Absorptance of a particular gas α = 1 – A / Ao

A = power received at absorbing wavelength

Ao = power received at non-absorbing wavelength

ρ = Pe f(α / Pe) [mol m-3] number densityρ = Pe f([1 – z A / Ao ] S / Pe); Pe is equivalent pressure

S is ‘span’Channels available for water vapor and CO2

Infrared Gas Analyzer (IRGA)

Ƭ = ρ <u’w’> + ρ <v’w’> + ρ <u~w~> streamwise transverse wave stress

U = <u> + u’ + u~

V = <v> + v’ + v~

W = <w> + w’ + w~

Wind stress (momentum flux) drives currentsand waves, thus driving heat transport in theocean.

Wind Stress

Hs = ρ Cp <w’θ’> Sensible heat fluxHL = ρ Lv <w’q’> Latent heat flux

T = <Θ> + θ’Q = <q> + q’

Heat transfer between the sea surface and atmosphere is another primary driver of ocean circulation

Heat Fluxes

Using advanced techniques for direct measurementof air-sea fluxes, we have obtained data from oceansaround the world.

This data has been used to develop parameterizationsto estimate air-sea fluxes from mean state variables (wind speed, air temperature, sea temperature, humidity, etc).

Air-sea fluxes of heat (latent/sensible) are also fundamental to cloud development (hence, surfaceenergy budget, precipitation, etc).

Ron Brown Mast

NOAA/ESRL Turbulent Flux System

Example of power spectra for wind velocity components

Flow distortion study

Energy Budget

QNET = QS↑ + QS↓ + QL↑ + QL↓ + HS + HL + Storage

Net at the surfaceShortwave up/down (albedo)Longwave up/downSensible turbulent heat fluxLatent turbulent heat flux

QL↑ = ε(σT4-QL↓)

Surface energy budget study from Stratus 2003

Radiative fluxes / Clouds / Water vapor / Boundary layer profiles

Downwelling solar Downwelling IR Cloud base height, cloud fraction T / RH / wind profiles

InstrumentsPyrgeometer (PSP)Pyranometer (PIR)Ceilometer60 GHz scanning microwave radiometerC-band radarWind profiling radar (915 MHz)Cloud radars (35 GHz [Ka], 94 GHz [W])

Eppley PIR (longwave) Eppley PSP (shortwave)

Issues with roll, pitch of ship are resolved with stabilized platform

TAO/PACS Heat Fluxes95 & 110˚W

Model

TAO buoy

WHOI (1984-2002)[Yu and Weller 2007]

CORE (1984-2004)[Large and Yeager 2004]

NOAA ship observations(1999-2002) [Fairall et al. 2008]

GFDL CM2.1

late

nt

sensi

ble

longw

ave

sola

rnet

IROAM

-12 -8 -4 0 4 8 12

-160

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-12 -8 -4 0 4 8 12

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-12 -8 -4 0 4 8 12-75

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-12 -8 -4 0 4 8 12100

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north latitude

-12 -8 -4 0 4 8 12

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NOAA Ship Ronald H. Brown

Ron Brown C-band Radar reflectivity 08:00 UTC 08/01/2004

Ron Brown C-band Precip Radar

Radiometers and raingauge

Radiosonde launch can be difficult

ceilometer

Radiometers

23 – 32 GHz

Passive “Mailbox” -> integrated water vapor, liquid, brightness temperature

Radiometrics Model 150022-30 GHz Continuous water vapor profiles up to 10km, integrated liquid water.NOAA ESRL also has a Model WVR-1100 (mailbox)

TeraScan visible image with Stratus Buoy (NOAA-18, 20:43 UTC 10/19/2006)GOES, NOAA, DMSP, SeaWiFS, Aqua, etc

Ron Brown 915-MHz Wind Profiler

Water-side measurements

CurrentsTemperature and salinity profilesWave measurement systems

InstrumentsConductivity temperature depth (CTD)Acoustic Doppler current profiler (ADCP)WAMOSLaser altimeter

CTD

Strain gauge pressure sensorThermistor to measure temperatureConductivity = Current / Voltage (1/R)

Uses a bridge circuit to detect smallchanges in resistance

CTD and watersampling bottle array ADCP

WAMOS (Wave and Surface Current Monitoring System)

Significant wave height (height of the highest 1/3 of waves)

Hs = 4 < ζ2 >1/2

ζ is the standard deviation of surface displacement.

ω = 2 π f ω is wave frequency (f is in Hz)ω = 2 π / T T is wave periodk = 2 π / L L is wave lengthω2 = g k Deep waterc = (g/k)1/2 Phase velocity

PACS Synthesis ExamplesPACS Synthesis Examples

Liquid and vapor water columndiurnalsampling

diurnalsampling

250

618

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-85 -82.5 -80 -77.5 -750

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degrees longitude

heig

ht

(km

)

surface LCL

cloud base

cloud top

Cloud height

cloud base 10% higherthan LCL

Cloud base above 900 m decoupled from surface layer

Effect of stratification and mixing on cloud base

“Sea Snake”Surface temperature measurement