Modeling of middle atmosphere dynamics with LIMA

Applying LIMA we are able to simulate in situ wind reversals of the mesospheric jets and cold summer mesopause states without applying any gravity wave parametrization. In the summer season the mesospheric wind reversal of the westward zonal wind is in the order of +5-10 m/s which implies that the resolved eddy fields and hence EP-flux divergences, determining the momentum budget of the mesopause region, are underestimated by approximately a factor of two. On the other hand the thermal structure of the summer mesopause, and hence at least the balance of the energy budget in the summer mesopause region, is reproduced. E.g. during early July the observed mesopause temperature from rocket (falling spheres) experiments over ALOMAR (69∘N, 16∘E) is 131 K at 88 km compared to corresponding model temperature of 133 K at 88 km. The results of our numerical simulations suggest (1) that the intrinsic variability of the mesosphere is indeed determined by the lower atmosphere variability, and (2) that the simulated eddy fields may be interpreted as some fraction of inertia gravity waves resolved by the model (λxy⩾500km, 2h⩽T⩽12h).