Simulations of moist convection using the quasi-elastic equations

Abstract

Cloud Resolving Models use microphysics parameterisation schemes for the simulation of clouds. The thesis reports on the introduction of two single-moment Bulk Microphysics Parameterisation (BMP) schemes in the Nonhydrostatic - coordinate Model (NSM). The rst BMP is known as the PURDUE-LIN scheme, and can be used with ve (excluding graupel) or six (including graupel) classes of the water substance. The second scheme was developed using the PURDUELIN scheme as a starting point, and is known as SBU-YLIN. Graupel and snow share a category and processes in the latter scheme. Simulations of two hours in length are made, with convection initiated through inserting a warm thermal into a cooler environment, using a six-class and ve-class PURDUE-LIN and the SBU-YLIN BMPs. The simulations are performed at various horizontal resolutions of 500 m, 1 km and 2 km. The six-class PURDUE-LIN scheme simulates more rainfall than the ve-class PURDUE-LIN and the SBU-YLIN schemes. The SBU-YLIN scheme generally rains the least, looses the least water vapour to hydrometeors and warms up the least. The PURDUE-LIN schemes simulate two convective cells in a no shear environment. The maximum updrafts associated with the rst cell (triggered by the warm perturbation) are similar in all the simulations. The second cell is triggered by a cold pool. While the cold pool is stronger in the six-class PURDUE-LIN scheme simulations, the updrafts in the second cell are stronger in the ve-class PURDUE-LIN simulation. The SBU-YLIN scheme generally simulates just one cell because of a weak cold pool. Simulations were also made for three di erent periods dominated by suppressed convection with deep convection at the beginning and end of the three periods, forced with large scale tendencies observed during the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE). The NSM is able to capture di erences in the suppressed and deep convection periods. Qualitatively, the simulations provide new insight into the interplay between cloud microphysics and cloud dynamics, and points out the potential for better describing the uncertainty range associated with projections of future climate change, through the improvement and stochastic application of cloud microphysics schemes.