The physical processes causing nocturnal rainfall over northwest Australia and their representation in high- and low-resolution models with parametrized convection

Ackerley, D. and Birch, C. E. and Garcia-Carreras, L. and Lavender, S. L. and Weller, E. (2018) The physical processes causing nocturnal rainfall over northwest Australia and their representation in high- and low-resolution models with parametrized convection. Quarterly Journal of the Royal Meteorological Society, 144 (711). pp. 511-528. ISSN 0035-9009

Abstract

The diurnal cycle of precipitation in the Tropics is represented poorly in general circulation models (GCMs), which is primarily attributed to the representation of moist convection. Nonetheless, in areas where precipitation is driven by the diurnal cycle in the synoptic-scale flow, GCMs may represent that circulation–rainfall relationship well. Over northwest Australia there is a tendency for precipitation to peak overnight where the diurnal cycle of the heat low circulation leads to the development of strong convergence after local sunset. In order to assess the heat low–precipitation relationship in more detail, a case-study approach is used to investigate the actual ‘weather’ that is responsible for night-time precipitation. The study shows that, where there is sufficient moisture, precipitation typically forms along convergence zones that coincide with boundaries between relatively moist and dry air masses (termed a ‘dryline’). A convergence line detection algorithm is then used to identify the fraction of observed nocturnal rainfall that is associated with any convergence zones. The same evaluation is then undertaken for a relatively high-resolution (MetUM) and low-resolution (ACCESS1.0) GCM, which simulate rainfall-generation processes similar to the observations. Finally, the convergence line detection/precipitation algorithm is run on other GCM data (from CMIP5) to see whether the same processes occur despite different model configurations (i.e. physics), which appears to be the case.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Permanent restricted access to Published version, in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 27 Feb 2019 01:42
Last Modified: 28 Feb 2019 04:23
Uncontrolled Keywords: CMIP5; convergence; dryline; heat low; MetUM; nocturnal; northwest Australia; rainfall; climate models; precipitation (meteorology); Australia; rain
Fields of Research : 04 Earth Sciences > 0401 Atmospheric Sciences > 040107 Meteorology
04 Earth Sciences > 0401 Atmospheric Sciences > 040105 Climatology (excl.Climate Change Processes)
Identification Number or DOI: doe:10.1002/qj.3223
URI: http://eprints.usq.edu.au/id/eprint/35911

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