Abstract

It is well established that using km scale grid resolution for simulations of weather systems in weather and climate models enhances their realism. This study explores heavy and extreme precipitation characteristics over the Nordic region generated by the regional climate model, HARMONIE-Climate (HCLIM). Two model setups of HCLIM are used: ERA-Interim driven HCLIM12 covering Europe at 12 km resolution with parameterized convection and HCLIM3 covering the Nordic region with 3 km resolution and explicit deep convection. The HCLIM simulations are evaluated against several gridded and in situ observation datasets for the warm season from April to September regarding their ability to reproduce sub-daily and daily heavy precipitation statistics across the Nordic region. Both model setups are able to capture the daily heavy precipitation characteristics in the analyzed region. At sub-daily scale, HCLIM3 clearly improves the statistics of occurrence of the most intense heavy precipitation events, as well as the timing and amplitude of the diurnal cycle of these events compared to its forcing HCLIM12. Extreme value analysis shows that HCLIM3 provides added value in capturing sub-daily return levels compared to HCLIM12, which fails to produce the most extreme events. The results indicate clear benefits of the convection-permitting model in simulating heavy and extreme precipitation in the present-day climate, therefore, offering a motivating way forward to investigate the climate change impacts in the region.

Highlights

  • Precipitation extremes represent a major environmental and socioeconomic hazard worldwide, and the Nordic region is no exception

  • This study explores heavy and extreme precipitation characteristics over the Nordic region 15 generated by the regional climate model, HARMONIE-Climate (HCLIM)

  • Two model setups of HCLIM are used: ERAInterim driven HCLIM12 spanning over Europe at 12 km grid spacing with a convection parameterization scheme and HCLIM3 spanning over the Nordic region with 3 km grid spacing and explicitly resolved deep convection

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Summary

Introduction

Precipitation extremes represent a major environmental and socioeconomic hazard worldwide, and the Nordic region is no exception. Fosser et al (2015), Lind et al (2016), Kendon et al (2017), Leutwyler et al (2017), Berthou et al (2020), Fumière et al (2020), Ban et al (2021), and Caillaud et al (2021) have found an added value of models with explicit convection compared to their coarser RCM counterparts with parameterized convection, especially in 55 the ability of the CPRCMs to represent sub-daily rainfall characteristics over Europe. Lind et al (2020) focused mainly on general model evaluation, while Olsson et al (2021a) evaluated heavy and extreme 70 precipitation events only over the southern part of Sweden Both studies found an added value of the convection-permitting HCLIM38 model setup in simulating the intensities and frequencies of mean and heavy precipitation events at sub-daily time scales. The current study deepens the understanding of the benefits of convection-permitting climate modeling over Northern Europe by extending the analysis by Olsson et al (2021a) over the 75 whole model domain and by studying extreme precipitation events with generalized extreme value (GEV) theory

Model and experiment set-up
Observations
Evaluation metrics of heavy precipitation
Extreme value analysis
Evaluation of heavy daily precipitation
Evaluation of extreme daily precipitation
Evaluation of heavy hourly precipitation
Evaluation of extreme hourly precipitation
Seasonality of hourly and daily annual maximum precipitation
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