Potential and limitations of convection-permitting CNRM-AROME climate modelling in the French Alps

Abstract

<p>Despite continued progress and a growing literature assessing regional climate change worldwide, modeling and assessing climate characteristics in mountainous regions remain challenging. Yet the stakes are high in these regions. As significant changes affect glaciers and snowpack, having<br>cascading effects on regional hydrology, quantifying them as accurately as possible is necessary for societal actors to adapt and reduce the growing climate risks.</p><p>Convection permitting climate modelling is a promising avenue for climate change research and services, particularly in mountainous regions. Work is required to evaluate the results of high resolution simulations against relevant reference dataset and put them in a broader context against coarser resolution modeling frameworks.</p><p>Our research assesses the potentials and limitations of high resolution climate models to represent past and future changes in snow conditions in the European Alps.</p><p>Here, we present an insight from the convection permitting climate model (CPRCM) CNRM-AROME ran at 2.5 km horizontal resolution over a large pan-Alpine domain in the European Alps, using either the ERA-Interim or CNRM-CM5 output as boundary conditions.</p><p>Annual and seasonal characteristics of four variables (2m temperature, total precipitation, solid fraction of precipitation and snow depths) are compared over the French Alps with the local reanalysis S2M, and raw or adjusted, with the ADAMONT method, simulations of the regional<br>climate model CNRM-ALADIN driven either by the ERA-Interim reanalysis or the CNRM-CM5 global climate model.</p><p>The study generally highlights similar differences in past and future climate between the datasets, as well as obstacles to the use of some CNRM-AROME outputs as they stand. These consist of excessive accumulation of snow on the ground above 1800 m a.s.l., as well as lower temperature<br>values at same elevations than the S2M reanalysis and the ADAMONT-adjusted outputs.</p><p>Nevertheless, clear advantages of CNRM-AROME simulations compared to raw CNRM-ALADIN outputs appear, concerning the temperature fields, the better representation of precipitations, as well as the spatial variability closer to the reference data.</p>

Evaluation of the convection-permitting regional climate model CNRM-AROME41t1 over northwestern Europe

“…In their study comparing 4-, 12-and 36-km RCM simulations, Mendoza et al (2016) highlighted the effect of the RCM's horizontal resolution on basin-averaged precipitation amounts, which in turns also affects the river flow simulations of three high-elevation catchments of the Colorado River basin. Finally, Monteiro et al (2022) highlighted clear advantages of 2.5-km CNRM-AROME compared to 12-km CNRM-ALADIN for 2-meter temperature and accumulated precipitation, especially over higher altitudes where they recognized that the simulated precipitation could be sometimes more realistic than their reanalysis reference, but with an excessive accumulation of snow above 1800 meters.…”

“…Then, this version showed clear added value with respect to the RCM CNRM-ALADIN through the improvement of the localization and intensity of extreme Mediterranean heavy precipitation events on a daily and hourly time scales (Fumière et al 2020). Since these early developments, a new version of the CNRM-AROME based on the cycle 41t1 has been developed and used for several years (Caillaud et al 2021;Monteiro et al 2022).…”

Reply on RC1

“…All computations were performed with Python software version 3.9.13. The codes and snow depth simulations for each CNRM-AROME experiments are available from a zenodo repository (Monteiro et al, 2024). It includes the snow depth simulations for each CNRM-AROME experiments used in the study as well as scripts (in a notebook form) for the following tasks : performing all data preprocessing, reading the different data sources, statistical analyses and figures making.…”