Resolving surface currents and heat advection with the global drifter array
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Resolving Surface Currents and Heat Advection with the Global Drifter Array. Rick Lumpkin. Atlantic Oceanographic and Meteorological Laboratory, National Oceanic and Atmospheric Administration. NOAA Climate Observation Program 3 rd Annual System Review April 25-27, 2005.

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Resolving Surface Currents and Heat Advection with the Global Drifter Array

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Resolving Surface Currents and Heat Advection with the Global Drifter Array

Rick Lumpkin

Atlantic Oceanographic and Meteorological Laboratory,

National Oceanic and Atmospheric Administration

NOAA Climate Observation Program

3rd Annual System Review

April 25-27, 2005


1. What we can resolve


75% of 1°1°bins!

Time-mean currents


Seasonal variations of SST


Differences with satellite SST products


Differences with satellite SST products


Mean heat advection

SST gradient (°C per degree)

Mean heat advection, upper 30m (W/m2)


Advection of SST anomalies

W/m2

Anomalous heat advection, upper 30m (W/m2)


378 drogued

Surface current anomalies


2. What we aren’t resolving

(Drifters alone: any process happening in data gaps)


Eddy fluxes and anomalous advection of mean SST


Evaluating the drifter array

SST: GOOS evaluated by NOAA/NCDC

SURFACE CURRENTS

Accuracy: 2 cm/s

Resolution: 600 km

Number of measurements per month: 1

From Needler et al. 1999: Action plan for GOOS/GCOS and Sustained Observations for CLIVAR.


Evaluating the drifter array


Before and after


3. How can we improve?


Predicting the array


Predicting the array


Include information from other measurements (altimetry, winds)


170ºE-130ºW, 10ºS-10ºN

OSCAR

Pilot project for a NOAA/NESDIS Operational Surface Current Processing and Data Center

(F. Bonjean, J. Gunn, G. Lagerloef, E. Johnson)


AVISO Altimetry product

Collecte Localisation Satellites (CLS)

Topex/Poseidon, Jason-1, ERS-1 and ERS-2

Aviso


U(t)=U + A u’(t)

Absolute speed (m/s)

Drifters+wind, altimetry

altimeter

(methodology of Niiler et al., 2003)


L

pg

Coriolis

centrifugal

H

Cor

pg

centrifugal

H

L

large Rossby number flow

(centrifugal) (Coriolis) (Pressure gradient)

If we ignore centrifugal

(assume geostrophy), we:

Underestimate Coriolis

(underestimate v)

Overestimate Coriolis

(overestimate v)


1 0.5 0

Drifters: calibrating satellite SSV


Drifters: in-situ calibration to reduce global bias in satellite SSV

R. Lumpkin and G. Goni, NOAA/AOML


Summary: Global Drifter Array

  • What we can resolve:

    • <U>, <SST>, <U>·<SST>,

    • U(x,t) where coverage is sufficient

    • mean eddy statistics

    • Drifter SST(x, t): cal/val of satellite products

    •  <U>· SST’

  • What we can’t resolve:

    • Anything in the “data holes”

    • U(x,t) at sufficient resolution for time series

    • of eddy fluxes

  • What we can do about this:

    • Plan ahead: anticipate gaps

    • Synthesize drifters, winds and altimetry for

      • operational surface currents

    • Drifter U(x,t) cal/val of satellite products

[email protected]


fin


Terms in NINO3 region


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