Submitted as: development and technical paper
15 Jul 2022
Submitted as: development and technical paper | 15 Jul 2022
Status: this preprint is currently under review for the journal GMD.

The pseudo-global-warming (PGW) approach: Methodology, software package PGW4ERA5 v1.1, validation and sensitivity analyses

Roman Brogli1,2, Christoph Heim1, Silje Lund Sørland1,3, and Christoph Schär1 Roman Brogli et al.
  • 1Institute for Atmospheric and Climate Science, ETH Zurich, Universitätstrasse 16, 8092 Zurich, Switzerland
  • 2SRF Meteo, 8052 Zurich, Switzerland
  • 3NORCE, Jahnebakken 5, 5007 Bergen, Norway

Abstract. The term pseudo-global warming (PGW) refers to a simulation strategy in regional climate modeling. The strategy consists of directly imposing large-scale changes in the climate system on a control regional climate simulation (usually representing current conditions) by modifying the boundary conditions. This differs from the traditional dynamic downscaling technique where output from a global climate model (GCM) is used to drive regional climate models (RCM). The PGW climate changes are usually derived from a transient global climate model (GCM) simulation. The PGW approach offers several benefits such as lowering computational requirements, flexibility in the simulation design, and avoiding biases from global climate models. Yet, implementing a PGW simulation is non-trivial and care must be taken not to deteriorate the physics of the regional climate model when modifying the boundary conditions. To simplify the preparation of PGW simulations, we present a detailed description of the methodology and provide the companion software PGW4ERA5 facilitating the preparation of PGW simulations. In describing the methodology, particular attention is devoted to the adjustment of the pressure and geopotential fields. Such an adjustment is required when ensuring consistency between thermodynamical (temperature and humidity) changes on the one hand, and dynamical changes on the other hand. It is demonstrated that this adjustment is important in the extratropics, and highly essential in tropical and sub-tropical regions. We show that climate projections of PGW simulations prepared using the presented methodology are closely comparable to traditional dynamic downscaling for most climatological variables.

Roman Brogli et al.

Status: open (until 09 Sep 2022)

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Roman Brogli et al.

Roman Brogli et al.


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Short summary
The pseudo-global warming (PGW) approach is a downscaling methodology that imposes the large-scale GCM-based climate-change signal upon the boundary conditions of a regional climate simulation. It offers several benefits in comparison to conventional downscaling. We present a detailed description of the methodology, provide companion software to facilitate the preparation of PGW simulations, and present validation and sensitivity studies.