Assessment of MPAS variable resolution simulations in the grey-zone of convection against WRF model results and observations

Abstract

Regional weather forecasting models like the Weather Research and Forecasting (WRF) model allow for nested domains to save computational effort and provide detailed results for mesoscale weather phenomena. The sudden resolution change by nesting may cause artefacts in the model results. On the contrary, the novel global Model for Prediction Across Scales (MPAS) runs on Voronoi meshes that allow for smooth resolution transition towards the desired high resolution in the region of interest. This minimises the resolution-related artefacts, while still saving computational effort. We evaluate the MPAS model over Europe focussing on three mesoscale weather events: a synoptic gale over the North Sea, a föhn effect in Switzerland, and a case of organised convection with hail over the Netherlands. We use four different MPAS meshes (60 km global refined to-3 km (60-3 km), analogous 30-3 km, 15-3 km, global 3 km) and compare their results to routine observations and a WRF setup with a single domain of 3 km grid spacing. We also discuss the computational requirements for the different MPAS meshes and the operational WRF setup. In general, the MPAS 3 km and WRF model results correspond to the observations. However, a global model at 3 km resolution as a replacement for WRF is not feasible for operational use. More importantly, all variable-resolution meshes employed in this study show comparable skills in short-term forecasting within the high-resolution area at considerably lower computational costs.

Simulating and Evaluating Atmospheric River‐Induced Precipitation Extremes Along the U.S. Pacific Coast: Case Studies From 1980–2017

“…We further note that the nested downscaling methodology we employ in the present study is not the only possible approach in investigating fine‐scale extreme events. As computing power has increased and numerical model development has advanced rapidly over the past several years, global‐scale modeling tools have improved to the point that high‐resolution weather‐scale simulations are now possible in certain cases including but not limited to variable resolution global models and nonhydrostatic high‐resolution global models (Huang et al, ; Kramer et al, ; Leung et al, ; Satoh et al, ). To date, however, such methods have not been extensively validated with respect to the simulation of extreme AR‐related precipitation events.…”

How well does MPAS-atmosphere simulate the characteristics of the Botswana High?

“…Using MPAS, Skamarock et al (2013) showed the model could produce results similar to the state-of-the-art hydrostatic model at hydrostatic scales (dx > 10km) as well as nonhydrostatic structures (dx ~ few km) such as convective systems, similar to those produced by nonhydrostatic regional models. While the capability of MPAS to simulate different atmospheric features has been shown (Kramer et al 2018), no studies have shown how well MPAS reproduces the characteristics of the Botswana High. Hence, the present study aims to examine how well the MPAS model simulates the characteristics of the Botswana High, especially the in uence of the high on drought over southern Africa.…”

A physically based precipitation separation algorithm for convection‐permitting models over complex topography

“…The first case-study (hereafter called the IOP case) is characterized by multiple slow-moving mesoscale convective systems hitting the French Riviera and the Appenines (described in Duffourg et al, 2016 andMartinet et al, 2017). The second case-study is a foehn event, which had persistent orographic precipitation on the Italian side of the Alps with observed point totals around 500 mm (Kramer et al, 2018).…”