The Austausch Coefficient in Relation to the Meridional Eddy Transport of Heat

[摘要] The Austausch coefficient K which is used in the so-called zonally averaged model for the discussion of climate change is usually considered as constant with time. However, K is regarded as time dependent variable in this paper. And the relation between the meanvalue of K(τ) averaged over the time intervalτ, K(τ), and the standard deviation of K(τ), √K' (τ)2, is discussed as a function of τ. The result shows that √K' (τ)2/K(τ) decrease as 1/√τ and it is necessary to take the longer time inverval more than τ=30 days if we wish to obtain the small value of √K'2/K that is less than 1/10.In the latter part of this paper, the seasonal change of zonally averaged surface temperature, To and mean temperature in the vertical column of the atmosphere, [T] is computed by making use of the zonally averaged model for the temperature. The value of K in the model is treated as a function of time with the assumed standard deviation of, √K'2(τ) (τ=1 day). The difference between [T] in case of K=const. with time and that in case of K=variable with time is compared. The difference is large in high latitude while the small value is obtained in the tropics. Taking the time average of the difference mentioned above over the period of τ=30 days, we compute the latitudinal variance of [T] for τ=30 days in the zonally averaged model and it is compared with the latitudinal so-called noise level of zonally averaged 1.5 km temperature forτ=29 days obtained by the NCAR GCM.

[学科分类] 大气科学