BEGIN:VCALENDAR VERSION:2.0 PRODID:-//132.216.98.100//NONSGML kigkonsult.se iCalcreator 2.20.4// BEGIN:VEVENT UID:20260927T065909EDT-2172HtsJve@132.216.98.100 DTSTAMP:20260927T105909Z DESCRIPTION:Atmospheric and Oceanic Sciences Departmental Seminar Series\n \npresents\n\nNumerically simulated orographic convection across multiple grey zones\n\na talk by\n\nProf. Daniel Kirshbaum\n Associate Professor & C hair\, Department of Atmospheric and Oceanic Sciences\, McGill\n\nAs weath er and climate models inexorably move to finer grids\, they traverse so-ca lled “grey zones”\, or ranges of horizontal grid spacings where key proces ses transition from fully parameterized to fully explicit. Within these gr ey zones\, scale-separation between the process of interest and the grid s cale\, a fundamental assumption of most subgrid parameterizations\, breaks down. For the moist convection problem\, which in the real atmosphere is characterized by horizontal scales from O(10 km) down to O(100 m)\, two im portant numerical grey zones exist: (i) the deep convection grey zone [O(1 0 km) to O(1 km)] and the turbulence grey zone [O(1 km) to O(100 m)]. In t his study\, idealized numerical simulations of orographic convection cross ing both grey zones are conducted to quantify the errors stemming from ina dequate resolution of cloud processes. The experiments consider two differ ent mechanisms by which orography commonly initiates moist convection: mec hanical and thermal forcing. To aid the diagnosis\, a new method of diagno sing entrainment/detrainment in large-eddy simulations is proposed. For bo th convection-initiation mechanisms\, cases with parameterized convection exhibit large biases in the timing\, intensity\, and/or horizontal distrib ution of clouds and precipitation. Although the results greatly improve fo r “convection-permitting” grids of O(1 km) and below\, they do not always converge to a robust solution as the grid spacing is decreased. Robust sol utions are found only in flows with well-developed turbulence fields prior to convection initiation. By contrast\, in cumulus fields undergoing turb ulent transition\, the transition itself is highly sensitive to the grid s pacing\, which prevents numerical convergence. For these cases\, O(10 m) o r smaller grids may be required to achieve robust solutions.\n\nMonday Jan 20/ 3:30 PM/ Burnside Hall/ Room 934\n DTSTART:20200120T203000Z DTEND:20200120T220000Z LOCATION:Room 934 SUMMARY:Numerically simulated orographic convection across multiple grey zo nes URL:https://www.mcgill.ca/meteo/channels/event/numerically-simulated-orogra phic-convection-across-multiple-grey-zones-303638 END:VEVENT END:VCALENDAR