Direct comparison between a non orographic gravity wave drag scheme and constant level balloons
Résumé
The parameterization scheme that represents gravity waves due to convection in LMDz A, the atmospheric components of the IPSL coupled climate model (IPSLCM), is di rectly compared to Strateole- balloon observations made in the lower tropical strato sphere from November to February.
The input meteorological fields necessary to run the parameterization offline are extracted from the ERA reanalysis and corre spond to the instantaneous meteorological conditions found underneath the balloons. In general, we find a fair agreement between measurements of the momentum fluxes due to waves with periods less than hr and the parameterization. The correlation of the daily values between the observations and the results of the parameterization is around which is statistically elevated considering that we consider around days of data and surprisingly good considering that the parameterization has not been tuned: the scheme is just the standard one that helps producing a Quasi-Biennial Oscillation in the IPSLCM model. Online simulations also show that the measured values of the momentum fluxes are also well representative of the zonally and averaged values of momentum fluxes needed in LMDz-A to simulate a QBO. The observations also tell that longer waves with pe riods smaller than a day roughly carry about twice as much fluxes as waves with peri ods smaller than an hour, which is a potential problems since low period waves that make the difference are potentially in the “grey zone” of most climate models.
Domaines
Sciences de l'environnement
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