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The impact of surface heterogeneity on the diurnal cycle of deep convection

Harvey, N. J. ORCID: https://orcid.org/0000-0003-0973-5794, Daleu, C. L., Stratton, R. A., Plant, R. S. ORCID: https://orcid.org/0000-0001-8808-0022, Woolnough, S. J. ORCID: https://orcid.org/0000-0003-0500-8514 and Stirling, A. J. (2022) The impact of surface heterogeneity on the diurnal cycle of deep convection. Quarterly Journal of the Royal Meteorological Society. ISSN 1477-870X (In Press)

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To link to this item DOI: 10.1002/qj.4371

Abstract/Summary

Despite some recent improvements, there remain major deficiencies in model simulations using parameterised convection in capturing both the phase and amplitude of the daily cycle of precipitation in tropical regions. The difficulties are particularly acute in regions of heterogeneous surface conditions, since the simulations need not only to respond appropriately to the local forcing from surface fluxes but also to capture the interactions with near-surface mesoscale circulations. Here we examine such a situation by means of idealised cloud-resolving simulations of deep convection over a heterogeneous surface, performed using the cloud-resolving simulation model MONC. In these simulations, we show that precipitation forms preferentially over dry and warm patches ("DRY") as compared to wet and cold patches ("WET"), with the peak precipitation rates differing by a factor of approximately 4. The initiation of precipitation occurs approximately 1.5 hours earlier in the DRY patches compared to the WET. Moreover, within the WET and DRY patches there are marked differences in the spatial distribution of the precipitation. These cloud-resolving simulations are then used as a benchmark to assess the behaviour of simulations using parameterised convection, performed using the idealised configuration of the MetUM. The MetUM simulations do produce a response with some qualitative similarities to the cloud-resolving simulations. In particular, although the simulations with parameterised convection initiate precipitation too early they are capable of capturing the relative amounts of daily-mean precipitation in the DRY and WET patches. We propose that the cloud-resolving simulations could be further used to investigate the impact of fully interactive surface schemes and as benchmark simulations to evaluate new parameterisation schemes.

Item Type:Article
Refereed:Yes
Divisions:Science > School of Mathematical, Physical and Computational Sciences > NCAS
Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:107101
Uncontrolled Keywords:cloud resolving models, convective parameterisation, land-atmosphere interaction, rainfall
Publisher:Royal Meteorological Society

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