Alison Stirling

A pan-Africa convection-permitting regional climate simulation with the Met Office Unified Model: CP4-Africa

AbstractA convection-permitting multiyear regional climate simulation using the Met Office Unified Model has been run for the first time on an Africa-wide domain. The model has been run as part of the Future Climate for Africa (FCFA) Improving Model Processes for African Climate (IMPALA) project, and its configuration, domain, and forcing data are described here in detail. The model [Pan-African Convection-Permitting Regional Climate Simulation with the Met Office UM (CP4-Africa)] uses a 4.5-km horizontal grid spacing at the equator and is run without a convection parameterization, nested within a global atmospheric model driven by observations at the sea surface, which does include a convection scheme. An additional regional simulation, with identical resolution and physical parameterizations to the global model, but with the domain, land surface, and aerosol climatologies of CP4-Africa, has been run to aid in the understanding of the differences between the CP4-Africa and global model, in particular to ...

Phase correction for ALMA

We discuss the use of the water vapour radiometry technique for atmospheric phase correction as applied to the Atacama Large Millimetre Array (ALMA). The atmospheric conditions derived from site test instrumentation are summarised, and the nature of the phase correction problem quantified. We then present calculations of the expected errors in the radiometrically-corrected atmospheric phase, based on estimates of the radiometer sensitivity. These results indicate how well we need to know the atmospheric structure in order to make accurate phase estimates, and have implications for the meteorological instruments needed on the site. Finally we present the results of simulations of daytime turbulence on the site, and use these to predict the phase fluctuations due to wet and dry air, and discuss their implications for phase correction at Chajnantor.