Cold pools in small valleys: structure and influence of synoptic conditions

Cold pools which form in small valleys represent a localised threat to road safety and agriculture, but are not resolved by current numerical weather prediction (NWP) models. The COLd Air Pooling EXperiment (COLPEX) used intensive near-surface and upper air measurements to study cold pools in such terrain over a 15 month period in Shropshire, UK, in order to understand the processes involved in and conditions necessary for their formation.

This study examines the dependence of cold pool strength on synoptic conditions to establish relationships that may be used to downscale NWP temperature forecasts. Previous idealised two-dimensional modelling results have shown how the degree of sheltering, and its dependence on the synoptic background (via wind speed and stability) and valley characteristics, control the strength of cold pools. In this study, the above results are successfully adapted to three-dimensional valleys by examining the typical structure of real cold pools and establishing observational analogues to the modelled quantities.