Decorrelation scales of high resolution turbulent fluxes at the ocean-surface and a method to fill in gaps in satellite data products
Anastasia Romanou(1) and William B. Rossow(2)
Columbia University and NASA-GISS,
New York, NY 10027,
(2) NASA-GISS, 2880 Broadway, New York, NY 10025, United States
In the first part of the paper, a high space-time resolution
(1degree latitude/longitude and daily) dataset of the turbulent fluxes
at the ocean surface is used to estimate and study the seasonal to annual near-global maps of the decorrelation scales of the latent and sensible heat fluxes. The decorrelation scales describe the temporal
and spatial patterns that dominate the flux fields (within a bandpass
window) and hence reveal the dominant variability in the air-sea interaction. Regional comparison to the decorrelation scales of the flux-related variables such as the wind stress, the humidity difference and the SST identifies the main mechanism responsible for the variability in each flux field.
In the second part of the paper, the decorrelation scales
are used to develop a method for filling missing values in the
dataset which result from the incomplete satellite coverage. Weight
coefficients in a linear regression function are
determined from the spatial and temporal decorrelations and are
functions of zonal and meridional distance and time. Therefore they
account for all the spatial and temporal patterns on scales larger than 1day and 1degree latitude/longitude and smaller than 1year and the ocean basin scale. The method is evaluated by simulating the missing-value distribution of the GSSTF2 dataset in the NCEP SST, the ISCCP-FD surface radiation and the GPCP datasets and by comparing the filled datasets to the original ones.
Main advantages of the method are that the decorrelation scales
are unrestricted functions of space and time, only information internal
to the flux field is used in the interpolation scheme and the computation cost of the method is low enough to facilitate its use in similar large datasets.