Using TRMM Latent Heat as a Source to Estimate Convection Induced Gravity Wave Momentum Flux in the Lower Stratosphere
Model and observational studies suggest that convectively generated gravity waves contribute about 50% of the total forcing to the eastward phase and the majority of the westward forcing of the Quasi-biennial Oscillation (QBO). Accurate estimates of gravity wave momentum flux in the lower stratosphere can hence improve their representation in global models and lead to a more accurate representation of the QBO and their teleconnections. Here we for the first time estimate the geographical distribution of gravity wave momentum flux at 100 hPa in the tropics and subtropics. We applied the links between the gravity wave momentum flux and convective heating directly to TRMM observations.
We show that eastward momentum flux is much greater in the tropics than westward momentum flux and that the majority of the gravity wave momentum flux comes from the intense convection over the oceans. A comparison of momentum flux derived from observations and parameterized gravity wave momentum flux in WACCM6 reveals large differences between gravity wave momentum flux derived from observations and those in the model, due to deficiencies in the representation of convection in the model.
In this study, we examine for the first time estimate the geographical distribution of gravity wave momentum flux at 100 hPa in the tropics and subtropics utilizing links between the gravity wave momentum flux and convective heating directly from TRMM observations. Subsequently, we compare the gravity wave momentum flux derived from observations to the parameterized gravity wave momentum flux in WACCM6. We find large differences in the convective gravity wave momentum flux between TRMM and WACCM6 due to the representation of convection in the model