A study of processes controlling convection over complex terrain (UK-COPS)

Lead Research Organisation: University of Leeds
Department Name: School of Earth and Environment


Flooding caused by heavy convective rain is a serious problem in the UK. Flash floods in hilly terrain can be particularly damaging. The Convective Orographically-induced Precipitation Study (COPS) is an international project designed to address this problem and to improve predictions of heavy convective precipitation. This proposal is the UK component of COPS which adds specific objectives complementary to those of other COPS partners. It will produce an understanding of the processes that control the formation and development of convective precipitation over hilly terrain which will be used by scientists within the Mesoscale Modelling group of the Met Office in reducing uncertainty in predictability of convection over complex terrain with the Unified Model (UM). This will be achieved by synthesising COPS data alongside modelling activities focussed on interpreting the data. The problem involves five integrated parts that need to be tackled together. (1) The thermally driven flows in complex terrain depends critically on the surface exchanges of heat and water. (2) The composition and size distribution of the aerosol particles have a crucial influence on the microphysics and dynamics of the convective clouds and particularly the amount of precipitation. (3) The thermals and other features in the boundary layer that transport heat, moisture and aerosols to the convective clouds. (4) The development of precipitation depends critically on the detailed microphysics and dynamics of the convective clouds. (5) Finally, reducing uncertainty in predictability of the location and timing of convective storms in hilly terrain with the UM, depends on the knowledge gained from these four parts. In particular the relative contributions of different sources of uncertainty in predictability of convective storms in hilly terrain will be quantified, thus providing the basis for an ensemble forecast system.


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Bennett L (2011) Initiation of convection over the Black Forest mountains during COPS IOP15a Convection Over the Black Forest in Quarterly Journal of the Royal Meteorological Society

Description Influence of detailed features in orography on the initiation of convection.

Role of venting of water vapour and pollutants out of boundary layer on the behaviour of convection.

Role of aerosols on precipitation. Unexpected behaviour: more precipitation with more aerosols in complex cloud systems because of cold pools being formed in the early convection that generates new and more vigorous convection.

Short-circuiting of glaciation process if rain is first produced with no ice in the cloud (the so-called warm rain process). The raindrops play an important role in the subsequent development of ice and precipitation particles, particularly in clouds that can produce short, sharp, heavy rainfall.

High resolution models (100-200m) needed to capture the features in complex terrain.
Exploitation Route Improved forecasts of flash flooding from convective storms, particularly over complex terrain. Results will be used in numerical weather prediction models and eventually in climate models when parametrisation schemes based on the results have been developed.
Sectors Environment

Description The results have shown the particular physical processes that need to be represented better in NWP models, and also the resolutions that are required to capture the processes in such complex terrain. Also, the project provided an important and unique dataset for the evaluation, and hence improvement of models.
First Year Of Impact 2010
Sector Environment
Impact Types Societal