# iGen: The automated generation of a parameterisation of entrainment in marine stratocumulus

Tang, D.F. and Dobbie, S. (2011) iGen: The automated generation of a parameterisation of entrainment in marine stratocumulus. [MIMS Preprint]

In a previous paper we described a new technique for automatically generating parameterisations using a program called iGen. iGen generates parameterisations by analysing the source code of a high resolution model that resolves the physics to be parameterised. In order to demonstrate that this technique works with a model of realistic complexity we have used iGen to generate a parameterisation of entrainment in marine stratocumulus. We present details of our technique in which iGen was used to analyse the source code of a cloud resolving model and generate a parameterisation of the mean and standard deviation of entrainment velocity in marine stratocumulus in terms of the large-scale state of the boundary layer. The parameterisation was tested against results from the DYCOMS-II intercomparison of cloud resolving models and the parameterisation of mean entrainment velocity was found to be $5.27\times 10 ^{-3} \pm 0.62 \times 10^{-3}ms^{-1}$ compared to $5.2 \times 10^{-3} \pm 0.8 \times 10^{-3} ms^{-1}$ for the ensemble of cloud resolving models