Chapter 9
SURFACE FLUXES FOR PRACTITIONERS
OF GLOBAL OCEAN DATA ASSIMILATION
William B. Large
National Center for Atmospheric Research, Boulder, Colorado, USA
Abstract
The ability of available ocean surface fluxes to meet the demands of the
Global Ocean Data Assimilation Experiment (GODAE) for global, near
real time, fields of known uncertainty is examined. Surface flux problems
that are discussed in detail include the lack of direct surface measurements to serve as a standard, the difference between fluxes measured
at height above the sea and the desired surface fluxes, the complications posed by the need for ocean-ice fluxes, and the large number of
global fields required to describe the fluxes. The formulation of the airsea, ocean-ice and air-ice fluxes of momentum, heat and freshwater, in
terms of these fields is detailed from the measurements (including satellite based flux estimates) to the parameterizations. Air-ice fluxes are
included to cover the possibility of coupling a sea-ice model within the
data assimilation system. The position that there is no one set of flux
products that represents the best possible choice for GODAE in all regions and all components is adopted. An alternative merger of a variety
of different datasets is described along with objective corrections based
on regional and/or short term observations, and ocean model behavior.
A flux climatology based on these datasets and observed sea surface
temperature is presented as the mean and variability from the seasonal
to inter-annual, that GODA flux products should strive to reproduce.
The necessary condition of near zero net global heat and freshwater
climatological fluxes is demonstrated.
Keywords: Ocean flux measurement, parameterization, fields, climatology.
1.
Introduction
Global Ocean Data Assimilation Experiment (GODAE) places rigorous demands on the surface flux forcing, not all of which can be entirely
met. Most obvious, is the need for global coverage, including the poorly
229
E. P. Chassignet and J. Verron (eds.), Ocean Weather Forecasting, 229-270.
© 2006 Springe . Printed in the Netherlands.
r
SURFACE FLUXES FOR PRACTITIONERS
OF GLOBAL OCEAN DATA ASSIMILATION
William B. Large
National Center for Atmospheric Research, Boulder, Colorado, USA
Abstract
The ability of available ocean surface fluxes to meet the demands of the
Global Ocean Data Assimilation Experiment (GODAE) for global, near
real time, fields of known uncertainty is examined. Surface flux problems
that are discussed in detail include the lack of direct surface measurements to serve as a standard, the difference between fluxes measured
at height above the sea and the desired surface fluxes, the complications posed by the need for ocean-ice fluxes, and the large number of
global fields required to describe the fluxes. The formulation of the airsea, ocean-ice and air-ice fluxes of momentum, heat and freshwater, in
terms of these fields is detailed from the measurements (including satellite based flux estimates) to the parameterizations. Air-ice fluxes are
included to cover the possibility of coupling a sea-ice model within the
data assimilation system. The position that there is no one set of flux
products that represents the best possible choice for GODAE in all regions and all components is adopted. An alternative merger of a variety
of different datasets is described along with objective corrections based
on regional and/or short term observations, and ocean model behavior.
A flux climatology based on these datasets and observed sea surface
temperature is presented as the mean and variability from the seasonal
to inter-annual, that GODA flux products should strive to reproduce.
The necessary condition of near zero net global heat and freshwater
climatological fluxes is demonstrated.
Keywords: Ocean flux measurement, parameterization, fields, climatology.
1.
Introduction
Global Ocean Data Assimilation Experiment (GODAE) places rigorous demands on the surface flux forcing, not all of which can be entirely
met. Most obvious, is the need for global coverage, including the poorly
229
E. P. Chassignet and J. Verron (eds.), Ocean Weather Forecasting, 229-270.
© 2006 Springe . Printed in the Netherlands.
r