CMIP5-Derived Single-Forcing, Single-Model, and Single-Scenario Wind-Wave Climate Ensemble: Configuration and Performance Evaluation

Alvaro Semedo,Andreas Sterl,Jean-Raymond Bidlot,Arno Behrens,Joanna Staneva,Pedro Miranda,Mikhail Dobrynin,Hylke De Vries,Jens Murawski,Gil Lemos

doi:10.3390/jmse6030090

Abstract

A Coupled Model Intercomparison Project Phase 5 (CMIP5)-derived single-forcing, single-model, and single-scenario dynamic wind-wave climate ensemble is presented, and its historic period (1979–2005) performance in representing the present wave climate is evaluated. A single global climate model (GCM)-forcing wave climate ensemble was produced with the goal of reducing the inter GCM variability inherent in using a multi-forcing approach for the same wave model. Seven CMIP5 EC-Earth ensemble runs were used to force seven WAM wave model realizations, while future wave climate simulations, not analyzed here, were produced using a high-emission representative concentration pathway 8.5 (RCP8.5) set-up. The wave climate ensemble’s historic period was extensively compared against a set of 72 in situ wave-height observations, as well as to ERA-Interim reanalysis and Climate Forecast System Reanalysis (CFSR) hindcast. The agreement between the wave climate ensemble and the in situ measurements and reanalysis of mean and extreme wave heights, mean wave periods, and mean wave directions was good, in line with previous studies or even better in some areas of the global ocean, namely in the extratropical latitudes. These results give a good degree of confidence in the ability of the ensemble to simulate a realistic climate change signal.

Highlights

Climate change extends beyond the scientific community, becoming a key topic in day-to-day public opinion
The atmospheric model is the atmospheric component of the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) cycle 31r1
JJA global climatological means, as seen in the normalized differences shown in Figure 2

Summary

Introduction

Climate change extends beyond the scientific community, becoming a key topic in day-to-day public opinion. The study of the impact of climate change on future wave conditions is done following one of two methods: dynamical, using physically based wave models, and statistical, using statistical models, both relying on a priori GCM simulations. Dynamical wave climate simulations use close-to-the-surface wind speeds (usually at 10-m height; U10) and sea ice coverage (SIC) from GCMs to force a physical wave model. An ensemble of seven independent CMIP5 climate simulations, produced with the same GCM (EC-Earth) [46] was used to force the third generation WAM wave model [47], with U10 winds and SIC. The ensemble described in this study is, a “single forcing-single (wave) model-single scenario” wave climate ensemble, produced with the goal of reducing the variability inherent in using a multi-forcing GCM approach for the same wave model, as in [43], for example.

The EC-Earth GCM

The WAM Wave Model

Experimental Set-Up

Global Evaluation Data

In Situ Evaluation Data

Evaluation of the Wave Climate Simulation in the Historic Period