1. Large Eddy Simulations of Entrainment and Inversion Structure
Alison Fowler
Supervisor: Ian Brooks

2. Convectively driven entrainment

3. Example of LES

4. The IMPORTANCE of the EZ
The EZ is responsible for the growth of the ML
The depth of the ML is important for determining concentrations of variables within, for example, pollution.
Formation and distribution of clouds

5. Defining the EZ i)
However, Entrainment is a localised event: these definitions are area averaged so may not be useful for fully understanding individual entrainment events.
Davis, K. J., D. H. Lenshow, S. P. Oncley, C. Kiemle, G. Ehret, A. Giez, J. Mann, 1997: Role of entrainment in surface- atmosphere interactions over the boreal forest. J. Geophys. Res., 120,

6. Defining the EZ ii)
Brooks, I. M., 2003: Finding Boundary Layer Top: Application of a Wavelet Covariance Transform to Lidar Backscatter Profiles. J. Atmos. Ocean. Tech., 20,

7. Comparison of Definitions
Comparing relationship with the convective Richardson number :
Large Ri => little turbulence, there will be no entrainment unless it is strongly influenced from below
small Ri =>the interface is dynamically unstable and may become or remain turbulent entraining without any influence from large eddies bellow

8. Statistics of the EZ

9. Statistics of the EZ

10. Statistics of the EZ

11. Conclusions
Definitions of the EZ using area-averaged profiles cannot help in understanding entrainment events
The variability of the EZ top and bottom important for estimating Ri
Ri important for understanding dynamics of BL and has been used in parameterizations of the entrainment velocity.
Sullivan, P. P., C.-H. Moeng, B. Stevens, D. H. Lenshow and S. D. Mayor, 1998: Structure of the Entrainment Zone Capping the Convective Boundary Layer. J. Atmos. Sci,. 55,
Entrainment velocity is important in modelling cloud distribution and the budgets of pollution and heat.