Dynamical downscaling of tropical cyclones from CCSM4 simulations of the Last Glacial Maximum

Abstract

Dynamical downscaling of simulations of the Last Glacial Maximum (LGM) and late twentieth century (20C) were conducted using the Weather Research and Forecasting (WRF) model with the aim of (1) understanding how the downscaled kinematic and thermodynamic variables influence simulated tropical cyclone (TC) activity over the western North Pacific during the LGM and the 20C periods and (2) to test the relevance of TC genesis factors for the colder LGM climate. The results show that, despite the lower temperatures during the LGM, the downscaled TC climatology over the western North Pacific in the LGM simulation does not differ significantly from that in the 20C simulation. Among the TC environmental factors, the TC potential intensity, mid‐tropospheric entropy deficit, and vertical wind shear during the LGM were consistent with previous analyses of TC genesis factors in LGM global climate model simulations. Changes in TC genesis density between the LGM and the 20C simulations seem to be well represented by the ventilation index, a nondimensional measure of the combined effects of vertical wind shear, and thermodynamic properties, suggesting the potential applicability of those factors for TC activity evaluation during the LGM and possibly other climates.

Effects of climate change on probable maximum precipitation: A sensitivity study over the Alabama‐Coosa‐Tallapoosa River Basin

“…The WRF model, a successor of MM5, is a mesoscale numerical weather simulation model designed for both atmospheric research and operational forecasting. In addition, WRF has been widely used to dynamically downscale coarser‐resolution GCM signals into finer‐resolution climate projections that can better represent fine‐scale meteorological processes such as precipitation extremes [e.g., Caldwell et al , ; Lo et al , ; Rasmussen et al , ; Yoo et al , ]. In this study, we used a two‐way nested WRF domain at 9 km and 3 km horizontal spacing, with 110 × 122 and 184 × 220 grids in each domain, respectively (Figure ), and 45 vertical levels to conduct the simulation.…”

Tropical Cyclones and Climate Change Assessment: Part II: Projected Response to Anthropogenic Warming

“…In general, these tend to reinforce the notion that cooler climates are not necessarily periods with fewer TCs, with some model experiments simulating more TCs (e.g., Korty et al 2012;Sugi et al 2015), qualitatively consistent with projections of fewer TCs in a warmer climate, assuming a symmetry of TC frequency response between cooler and warmer climates. Yoo et al (2016), however, simulate little difference between TC incidence for LGM conditions versus current climate. Examples of simulations of enhanced TC activity during past warm climates include Yan et al (2016) and Federov et al (2018).…”

Globally consistent impact of tropical cyclones on the structure of tropical and subtropical forests

“…Although some geomorphological records in TC-prone regions show centennial to millennial variations in local TC frequency and intensity during the Holocene, these variation are pseudo-cyclic and do not indicate long-term trends (e.g., Burn & Palmer, 2015;Haig, Nott, & Reichart, 2014;Nott & Forsyth, 2012;Toomey, Donnelly, & Woodruff, 2013). Instead, global patterns of TCs across different regions vary less on a centennial scale but respond more strongly to major changes in global climate over longer time-scales, such as the Pliocene glaciations (e.g., Yoo, Galewsky, Camargo, Korty, & Zamora, 2016).…”