IORAS activities for DRAKKAR in 2006General topic: Development of long-term flux data set for interdecadal simulations with DRAKKAR models

Task: Using 2ePDF to derive homogeneous time series of turbulent fluxes at least in the North Atlantic.

What means homogeneous?

Sampling in 1960s+ should be as bad as before WW2 Impact of parameterizations should be minimized to the extent possible Impact of changes in observational practices should be minimized as well

Result expected: The fluxes will not be correct, but their variability might be reliable

Data: all VOS data from ICOADS (1880-2005)

RandomVOS-like sub-samplingReal-timeVOS-like sub-samplingRandom sampling errorTotal sampling errorObjectiveanalysis error6-hourly NWP individual variables Re-computation of surface fluxesusing bulk formulae Bulkparameteri-zationsHomogenization of sampling in space:

Sampling errors in fluxes:Double exponentialdistribution(2ePDF)10-3

Homogenization of sampling in time: MC-sub-sampling for n=7,15,25,50 per 5x5, 2x2 boxper 5x5 box

Parameterizations: COARE-3.0 (no skin, no free convection, instead - 4/3 convection scheme for calm winds, no mature turbulence scheme)Parameters: Wind Beaufort only, WMO1100 => to Lindau (1995) scale SST buckets only, no engine intakes Air temperature all

Production iterative run for every month: 1st guess - 2eWPDF derivation of monthly means for 10-degree boxes south of 40N and for gerrymander network north of 40N 2ePDF computation for 5x5 degree boxes, if the PDF does not fit at 95% level, use the 1st guess for the thresholds on the parameters then repeat the procedure again

123-yr (1880-2002) climatology

Climatological differences between 2ePDF-derived and traditionally averaged fluxes

Linear tends, sensible + latent, winter

Regional time series of winter sensible + latent heat flux1234

Winter (JFM) EOFs

Link of the leading mode in turbulent fluxes with NAO index:30-yr running correlation changes over time considerably

NAO is a dominant signal in driving NA circulation?NAO-based reconstructions of forcing are possible

Eden and Willebrand 2001, Eden and Jung 2001Eden and Willebrand 2001, J. ClimateEden and Jung 2001, J. ClimateHEAT FORCING IS IMPORTANTReconstruction for 1865-1997:MHT, 48N

Canonical correlation of the heat fluxes with HADSLP for different periods

Conclusions:5-degree 123-yr homogeneous time series of turbulentfluxes (1880-2002) were derived using 2ePDF integration multi-decadal variability is visible

Product is available at 2-degree resolution for 1910-1940 and 1948-2005

Individual variables are also available, so that use offorcing based on bulk formulae is possible

During the period 1915/20 1950/55 winter surface turbulent fluxes are just loosely connected with NAO, being closely related to NAO during the decades before and after this periodForcing long-term runs of ocean GCMs in [still] coarse resolutionPotential application

Other activities: validation of NOAA blendedsatellite winds 11 satellites, 0.25x0.25 resolution, global, 1987-onwards,

6-hourly effectively from 1994

Zhang et al. 2006

Validation of NOAA blended satellite winds 06:0018:00Much more detailed structure than ERA40

More reliable tropical winds than in both NCEP and ERA40

Good representationof coastal patterns

Computation of humidity:Strategy:

Statistical multiregression approach (not a neural network yet) for the decade of 1960s Deviations from seasonal climatology are considered Exponential functions + polynomials for Ta, V, SLP Done locally, for every month and every box

Effect in latent heat flux estimates:RMS = 7 W/m2

Slope = 0.996

Intercept = + 1.4 W/m2

Precipitation from NWP:Threshold on small precipitation, associated with the spin-up effect: 0.02 0.1 mm/day up to 10-12 mm/month in subpolar latitudes CMORPH 0.25x0.25, daily, satellites + model, 2001-onwards

WindsCardone (Oceanweather Inc.) kinematically corrected winds, up to 0.2 degree, 3-hourly (wind workstation)