Controls on the Vertical Profile of Moistening as a Function of Precipitation Rate
Abstract
The relationship between the profile of total moisture tendency (dq/dt) and precipitation rate has been identified as an important process diagnostic for simulation of the Madden-Julian Oscillation (MJO). Atmospheric general circulation models (AGCMs) with moistening that progressively deepens with precipitation rate generally simulate the MJO with higher fidelity than otherwise (Klingaman, et al., 2015). Here we use the NASA GEOS AGCM to study the moisture budget as a function of precipitation, and understand its sensitivity to model parameter changes, including those affecting deep and shallow convection, rain re-evaporation, cloud-radiative feedbacks and a cold pool scheme. A key finding is that the common approach to enhancing MJO simulation, by increasing deep convective entrainment, tends to increase mid-level moistening at intermediate rain rates and reinforces the pattern of progressively deeper moistening. Model tendencies are compared with MERRA-2 and ERA-5 reanalyses for validation, and their dependence on temporal and spatial averaging is explored. Finally, we consider links between changes in the moistening-precipitation relationship and the model's MJO.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A43S2989A
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 3337 Global climate models;
- ATMOSPHERIC PROCESSES;
- 3371 Tropical convection;
- ATMOSPHERIC PROCESSES;
- 1817 Extreme events;
- HYDROLOGY