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- Title
Evaluating the CoMorph-A parametrization using idealized simulations of the two-way coupling between convection and large-scale dynamics.
- Authors
Daleu, Chimene L.; Plant, Robert S.; Stirling, Alison J.; Whitall, Mike
- Abstract
We present a new methodology to test the interactions of convection schemes with their larger scale environment. A single-column model (SCM) using the new Met Office convection scheme, CoMorph-A, and the new Met Office-Natural Environment Research Council cloud-resolving model (CRM) are coupled to damped-gravity-wave-derived large-scale dynamics. The coupled models are used to investigate convective responses to stimulus forcings under the influence of interactive large-scale dynamics. Within CoMorph-A, the default entrainment varies with the prediction of convection size that is dependent on earlier rainfall, and the sensi-tivity of the SCM results to the entrainment formulation is explored. We demonstrate that the behaviour of the SCM using CoMorph-A is now very similar to that of the CRM. For temperature or moisture stimulus applied separately, the SCM adjusts to a new equilibrium that is similar to that in the CRM, but its transient convective responses to stimuli acting to suppress convection are markedly too fast. For a combination of stimuli acting to enhance convection, the SCM responses are stronger than in the CRM. Finally, convective rainfall in the SCM is relatively insensitive to a combination of stimuli acting to enhance and suppress convection simultaneously, in agreement with the CRM. However, the SCM recovery from a non-precipitating state is overly delayed for the default entrainment formulation but is too rapid when the entrainment rate is fixed at a low rate to represent only the deep convective state. We examined the responses to moisture stimuli of different strengths. Both models produce a monotonic increase of precipitation with column relative humidity (CRH) as well as the sharp increase of precipitation as CRH exceeds a threshold, as seen in observations. Though both models correctly capture the observed CRH threshold, differences from the observed precipitation-CRH relationship are noted. For instance, above the threshold the increase of precipitation with CRH is more abrupt in the SCM than in the CRM and observations. A similar behaviour is obtained in the SCM using low entrainment rate.
- Subjects
GREAT Britain. Meteorological Office; NATURAL Environment Research Council (Great Britain); ENTRAINMENT (Physics); HUMIDITY; SUPPLY chain management; RAIN gauges
- Publication
Quarterly Journal of the Royal Meteorological Society, 2023, Vol 149, Issue 757, p3087
- ISSN
0035-9009
- Publication type
Article
- DOI
10.1002/qj.4547