Surface Heat Flux Parameterization and Surface Energy Balance

Hindcasting the Madden Julian Oscillation with a New Parameterization of Surface Heat Fluxes

The recently developed maximum entropy production (MEP) model, an alternative parameterization of surface heat fluxes, is incorporated into the Weather Research and Forecasting Model (WRF). A pair of WRF cloud-resolving experiments (5 km grids) using the bulk transfer model (WRF default) and the MEP model of surface heat fluxes are performed to hindcast the October Madden–Julian oscillation (MJO) event observed during the 2011 Dynamics of the MJO (DYNAMO) field campaign. The simulated surface latent and sensible heat fluxes in the MEP and bulk transfer model runs are in general consistent with in-situ observations from two research vessels. Compared to the bulk transfer model, the convection envelope is strengthened in the MEP run and shows a more coherent propagation over the Maritime Continent. The simulated precipitable water in the MEP run is in closer agreement with the observations. Precipitation in the MEP run is enhanced during the active phase of the MJO with significantly reduced regional dry and wet biases. Large-scale ocean evaporation is stronger in the MEP run leading to stronger boundary layer moistening to the east of the convection center, which facilitates the eastward propagation of the MJO.






           Hovmöller diagrams of 3-hourly precipitation (mm day-1) averaged between 7.5°S and 7.5°N latitude from (a) TRMM observation, (b) CTL run, and (c) MEP run.




Time series of daily mean (left) latent heat flux and (right) sensible heat flux based on the observations from the research vessels (top) Mirai and (bottom) Revelle derived from eddy covariance (EC, solid black line), inertial dissipation (ID, long dash black line), and COARE bulk formula (BK, short dash black line). WRF simulated heat fluxes from the CTL run (blue line) and MEP run (red line) are obtained from the model grid points closest to the locations of the vessels.




Time series of (a) precipitable water (kg m-2) from the ERA-Interim (black line), CTL run (blue line), and MEP run (red line); (b) daily precipitation (mm day-1) from the TRMM observation (black line), CTL run (blue line), and MEP run (red line) averaged over the simulation domain (20°S-20°N, 48°-120°E).