3.12.1 Overview

The model is forced with climatological wind stress data from Trenberth et al. [1990] and NCEP surface flux data from Kalnay et al. [1996]. Climatological data [Levitus and T.P.Boyer, 1994b] is used to initialize the model hydrography. Levitus and T.P.Boyer seasonal climatology data is also used throughout the calculation to provide additional air-sea fluxes. These fluxes are combined with the NCEP climatological estimates of surface heat flux, resulting in a mixed boundary condition of the style described in Haney [1971]. Altogether, this yields the following forcing applied in the model surface layer.

$\displaystyle {\cal F}_{u}$	$\displaystyle =$	$\displaystyle \frac{\tau_{x}}{\rho_{0} \Delta z_{s}}$	(3.31)
$\displaystyle {\cal F}_{v}$	$\displaystyle =$	$\displaystyle \frac{\tau_{y}}{\rho_{0} \Delta z_{s}}$	(3.32)
$\displaystyle {\cal F}_{\theta}$	$\displaystyle =$	$\displaystyle - \lambda_{\theta} ( \theta - \theta^{\ast} ) - \frac{1}{C_{p} \rho_{0} \Delta z_{s}}{\cal Q}$	(3.33)
$\displaystyle {\cal F}_{s}$	$\displaystyle =$	$\displaystyle - \lambda_{s} ( S - S^{\ast} ) + \frac{S_{0}}{\Delta z_{s}}({\cal E} - {\cal P} - {\cal R})$	(3.34)

where ${\cal F}_{u}$ , ${\cal F}_{v}$ , ${\cal F}_{\theta}$ , ${\cal F}_{s}$ are the forcing terms in the zonal and meridional momentum and in the potential temperature and salinity equations respectively. The term $\Delta z_{s}$ represents the top ocean layer thickness in meters. It is used in conjunction with a reference density, $\rho_{0}$ (here set to $999.8\,{\rm kg\,m^{-3}}$ ), a reference salinity, $S_{0}$ (here set to 35 ppt), and a specific heat capacity, $C_{p}$ (here set to $4000~{\rm J}~^{\circ}{\rm C}^{-1}~{\rm kg}^{-1}$ ), to convert input dataset values into time tendencies of potential temperature (with units of $^{\circ}{\rm C}~{\rm s}^{-1}$ ), salinity (with units ${\rm ppt}~s^{-1}$ ) and velocity (with units ${\rm m}~{\rm s}^{-2}$ ). The externally supplied forcing fields used in this experiment are $\tau_{x}$ , $\tau_{y}$ , $\theta^{\ast}$ , $S^{\ast}$ , $\cal{Q}$ and $\cal{E}-\cal{P}-\cal{R}$ . The wind stress fields ( $\tau_x$ , $\tau_y$ ) have units of ${\rm N}~{\rm m}^{-2}$ . The temperature forcing fields ( $\theta^{\ast}$ and

) have units of $^{\circ}{\rm C}$ and ${\rm W}~{\rm m}^{-2}$ respectively. The salinity forcing fields ( $S^{\ast}$ and $\cal{E}-\cal{P}-\cal{R}$ ) have units of ${\rm ppt}$ and ${\rm m}~{\rm s}^{-1}$ respectively. The source files and procedures for ingesting this data into the simulation are described in the experiment configuration discussion in section 3.12.3.