Quantifying Cloud Organization and a First Look at UKMO simulations for MAGIC

Description

Firstly, a quantitative measure of the level of organization, or “apparent randomness”, of a cloud field is derived. This is then applied to one year of satellite cloud masks available every 15 minutes. Diurnal and seasonal cycles in the degree of organization of the clouds are studied over land and sea and over the mid-latitudes and tropics. Over land, the diurnal cycle of apparent randomness peaks several hours before the diurnal cycle of cloud cover. A sharp drop in the apparent randomness is associated with the clouds becoming more organised as the cloud cover continues to increase. Apparent randomness may be a useful quantitative metric when analysing case-studies of mesoscale organization and the temporal evolution of clouds and convection. Secondly, preliminary results are presented from a series of daily 48-hour hindcasts covering the year of the MAGIC campaign. These use the Met Office/HadGEM joint NWP/climate GA6 global model configuration with a grid-length of 30km. Average cross-sections using all the model data between Los Angeles and Hawaii are presented and are compared to cross-sections sub-sampled to mimic the ship transects. Plans for future model evaluation, based on cloud and boundary-layer regimes are discussed.