The Closure Procedure
for the OMIP-Forcing based on ERA-15
For the OMIP-Forcing the turbulent heat fluxes are calculated by using the formula (including the Naval Research Laboratory Air-Sea Exchange Coefficients (NASEC)) of Kara et al. (2005). To avoid northward heat transports on the Southern Hemisphere, a global scheme for katabatic winds is introduced which shows effects mainly around Antarctica, and the net solar radiation is reduced in agreement with satellite observations (Surface Radiation Budget) and ship measurements (Wendler and Worby 2001). The overestimation of the short and long wave radiations in the subsidence zones is compensated partly by using a global scheme. The budgets of heat and fresh water were closed by using the inverse procedure after Isemer et al. 1989 and da Silva et al. 1994. The forcing dataset (version 2) including the closure procedure and the correction schemes is described in Röske (2006). Parts of Tables 7 and 12 in this article are presented below:
Experiments: Correction Parameters pi Data sw lw se la pr ru Strong everywhere 0.6791 1.1578 0.9768 0.5036 0.3739 0.9381 - Strong only at 80°S (H & F) 0.8608 1.1274 1.1386 0.8606 0.7015 0.9705 - Strong only at 80°S (only F) 0.8856 1.1125 1.1354 0.9061 0.7432 0.9746 KW, SH Strong only at 80°S (H & F) and corr. on Southern Hemisphere (SH) 0.8911 1.1142 1.1487 0.9148 0.7528 0.9756 KW, SH Strong only at 80°S (only F) and radiation corr. in subsid. zones (SZ) 0.8890 1.1036 1.1177 0.9056 0.7427 0.9746 KW, SH, SZ Strong only at 80°S (H & F) and corr. on Southern Hemisphere (SH) and radiation corr. in subsid. zones (SZ) 0.8932 1.1064 1.1322 0.9116 0.7499 0.9753 KW, SH, SZ Strong only at 80°S (H & F) and radiation corr. in subsid. zones (SZ) and short wave rad. +10% at 23°N-23°S (TR) 0.9026 1.0408 1.0181 1.0688 0.8944 0.9896 KW, SH and TR, SZ Range from observations: 0.9 - 1.1 0.8 - 1.2 0.5 - 1.5 Dimensionless correction parameters as suggested by the inverse procedure. 4 digits are necessary for an accuracy of 0.01 PW of the implied meridional heat transport (MHT) especially on the Southern Hemisphere. "Strong" means: the transport observations have strong influence in the inverse procedure. H: Heat, F: Fresh water.
The two experiments "only F" yield non-vanishing MHTs at 80°S. They are reduced to approx. zero by using a correction for the katabatic winds (KW) and reducing short wave radiation by 11% on the Southern Hemisphere at 60°S - 90°S (SH). These steps are not included in the inverse procedure in these experiments, but in that following them.
"sw": short wave radiation. "lw": long wave radiation. "se": sensible heat flux. "la": latent heat flux. "pr": precipitation. "ru": runoff.
The numbers in the sixth row above override those in the second row of Table 12 in Röske (2006) which are wrong.
References:
da Silva, A.M., C.C.Young and S.Levitus, 1994: Atlas of surface marine data, Vol.1-5, NOAA Atlas NESDIS 6-10.
Isemer, H.-J., J. Willebrand, and L. Hasse, 1989: Fine Adjustment of Large Scale Air-Sea Energy Flux Parameterizations by Direct Estimates of Ocean Heat Transport. Journal of Climate, Vol.2, pp.1173-1184.
Kara, A. B., H. E. Hurlburt, A. J. Wallcraft, 2005: Stability-dependent exchange coefficients for air-sea fluxes. J. Atmos. Oceanic Technol., 22, 1077-1091. Download.
Wendler, G. and A.P.Worby, 2001: The surface energy budget in the Antarctic summer sea-ice pack. Annals of Glaciology, Vol. 33, p.275-279.
|
|||
|