MJO simulations under a dry environment. (… in a Nudging World). Marcela Ulate M Advisor: Chidong Zhang. Motivation.
(… in a Nudging World)
Marcela Ulate M
Advisor: Chidong Zhang
U850 Anom. ERA-Interim
Periodic Boundary conditions in the east-west
This was the best of our model simulations ….
The model has a dry bias in the mid troposphere i.e. it dries the atmosphere faster than the adjustment time between the wind convergence at lower levels and the rain production by the cumulus scheme. The net effect is to inhibit convection. Therefore, the convective component of the MJO cannot fully develop in the model environment
Model forcing terms
Nudging Tendency term
:analysis field value
: nudging factor ,
: four dimensional weight function,
From Skamarock et al. 2008.
Analysis data (ERA-Interim)
Spatially filter the data
Dependency of the small scales (~100Km)
BUT, Do we need the large scales ….? (See Future Work)
Humidity Tendency due to cumulus scheme - CONTROL
Humidity Tendency due to cumulus scheme MJO-like precipitation simulation
Heating Tendency – MJO-like precipitation simulation
How much nudging is too much nudging?
What if Ga=1 ?
Spectral and grid Nudging of water vapor mixing ratio reduces the model dry-bias and allows the model to produce an improved MJO-like precipitation pattern and wind signal.
The moisture at mid levels of the troposphere is crucial in order to reproduce the convective signal associated with the MJO.
The dependencies of the meridional and zonal scales close to ~100Km are important in order to obtain a better MJO-like simulations.
The prediction of the first MJO event improves when nudging is preformed,whilethe initiation of the second event is not. This suggests that improving the humidity field is one component of the problem, and we need to investigate further on this matter.
Without nudging, the cumulus scheme remains relative inactive i.e. lack of precipitation during the MJO event. This translates to aweak heating profile. When the MJO precipitation pattern improves, the heating profile resembles the results of other studies more closely.
Study more in depth the relationship between the large scale’s moisture role in MJO simulations.
Investigate the general characteristics of the transition between 2 MJO events and the inability of the model to capture abrupt changes in precipitation patterns.
Simulate the MJO using a cloud- resolving version of the WRF (25Km,8Km,3Km resolution) with YOTC data as boundary conditions for the same case of study and the addition of the second MJO event.