A revolutionary new Lagrangian model for convective clouds

This project will contribute to the development of a revolutionary new cloud model, EPIC (the Ellipsoidal Parcel-In-Cell model). Here, we will use EPIC for the simulation of convective precipitation and cloud-climate feedbacks. The model takes a new, Lagrangian approach to the simulation of clouds and precipitation. We will carry out this work in close collaboration with the Met Office. The project will be aligned with the Met Office/NERC programme on turbulent processes and an existing EPSRC project with David Dritschel (University of St Andrews), Leeds, EPCC and the Met Office.


The behaviour of turbulence and microphysical processes largely determines the timing and intensity of precipitation in weather and climate models. These processes also determine cloud properties which are important to climate change, but remain difficult to model even at high resolution. Droplets and hydrometeors interact to form precipitation along Lagrangian flow trajectories (small particles) or fall trajectories (larger particles, influenced by the ambient wind). EPIC deals with the dynamics of clouds by advecting parcels of fluid. Here, we propose to use EPIC to study precipitation in realistic clouds, such as those observed in the recent EUREC4A field campaign in Barbados.

Applying the parcel-based approach to cloud droplets and extending it to rain will make accurate simulation of regions in the cloud where rain forms possible. Our overall aim is to develop EPIC to the stage where it can outperform traditional cloud models by certain measures, and to generate publications in leading journals demonstrating this performance. Achieving this aim will make EPIC a viable choice of model by a wide international community of scientists, and may offer new solutions for improving weather and climate prediction models. This will result in reduced uncertainty in climate sensitivity and in weather forecasts of e.g. flooding. EPIC presents a radically different approach to the simulation of clouds, which will teach us about the interplay between mixing processes and microphysics in a way that is not possible in traditional models. EPIC also allows for a Lagrangian analysis which is consistent with the model dynamics and cloud processes.

Proposed work

A first step will be to implement a simplified microphysics scheme and compare results to the same case run using a traditional cloud model, to demonstrate the viability of the EPIC for microphysical analysis. Cloud dynamical and microphysical properties will also be compared against LES using the Cloud AeroSol Interactions Microphysics (CASIM) scheme, which was largely developed at the Met Office with collaboration from the University of Leeds. Subsequent work may address cloud-aerosol interactions.

A non-precipitating cloud simulated with the Parcel-in-Cell approach.