Added Value of Atmosphere-Ocean Coupling in a Century-Long Regional Climate Simulation

Kelemen, Fanni Dóra; Primo, Cristina; Feldmann, Hendrik; Ahrens, Bodo

doi:10.3390/atmos10090537

Cited by 18 publications

(22 citation statements)

References 33 publications

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“…Using a similar set up Primo et al (2019) demonstrated a better representation of extreme temperatures in coupled runs for the twentieth century compared to uncoupled runs. Kelemen et al (2019) showed significant effects on European continental precipitation in twentieth century simulations by driving the model in coupled mode and by prescribed passive SST fields. More recently, climate studies for the Mediterranean region (Med-CORDEX) were carried out with coupled regional atmosphere-ocean models (e.g.…”

Section: Purpose Of the Present Studymentioning

confidence: 99%

Is interactive air sea coupling relevant for simulating the future climate of Europe?

2020

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The majority of regional climate change assessments for the Euro-CORDEX region is based on high resolution atmosphere models. These models use prescribed lower boundary conditions, such as sea surface temperatures (SST) from global ocean General Circulation Models (GCMs), that do not respond to changes simulated by the regional atmosphere model, thus lacking an important feedback to the atmosphere. However, research during the past decade indicated that the use of coupled atmosphere–ocean models can lead to significantly altered model solutions compared to standalone atmosphere models for the present day climate imposing some uncertainty on the widely used uncoupled future scenarios. We here present the first multi-model and multi scenario (RCP2.6, RCP4.5, RCP8.5) ensemble of future climate change scenarios downscaled with a coupled atmosphere—ocean model in which sea surface temperature and sea ice fields are explicitly simulated by a coupled state-of-the-art high resolution ocean model and communicated to the atmosphere at 3-hourly time steps. Our ensemble generally confirms results of previous uncoupled ensembles over land areas implying that the coupling effect is restricted mainly to the coupled area and the adjacent coastal zone. By contrast, over the North Sea and Baltic Sea small scale processes point to important coupling effects that mediate the response to climate change and that can not be simulated by uncoupled models. Our results therefore impose general uncertainty on the usage of regional climate change data from uncoupled ensembles over marine areas such as for purposes of offshore wind or mussel farming, the planing of marine protected areas, and marine recreation along the coastal zone. It further sets in question the usage of uncoupled scenario data (such as Euro-CORDEX) to force high resolution ocean models. Comparing coupled and uncoupled hindcast simulations reveals that the coupling effect over land is most pronounced during the warm season when prescribed and modelled sea surface temperatures (SST) differ strongest. In addition, a generally weaker wind regime in summer damps the heat dispersion in the atmosphere so that air temperature anomalies can extent further over land compared to winter. Future projections are discussed under consideration of land-sea warming characteristics for selected climate indices as well as mean seasonal climate change. At the end of the century a clear land-sea pattern is seen in all scenarios with stronger warming over land than over open sea areas. On average land areas warm at a rate 1.5 times faster than areas over the open ocean. Over the coupled area, i.e. the North Sea and Baltic Sea tropical nights are impacted strongest and the Baltic Sea turns out to be a hot spot in future climate. This has been unrecognized in previous studies using high resolution atmosphere models with prescribed SSTs from global models which do not represent small scale ocean processes in the Baltic Sea adequately.

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Section: Purpose Of the Present Studymentioning

confidence: 99%

Is interactive air sea coupling relevant for simulating the future climate of Europe?

2020

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“…This highlights that regional air-sea interactions play a more relevant role for temperature in summer. In this reduction, an important role is played by the modi cation of the heat uxes through the interactive ocean, as part of the energy coming from the atmosphere is advected or mixed down to the deeper ocean, changing the turbulent heat uxes calculated by the stand alone atmospheric model (e.g., Li et al 2014;Kelemen et al 2019).…”

Section: Effect Of Air-sea Interactions On the 2-m Air Temperaturementioning

confidence: 99%

Impact of Air-Sea Coupling on the Climate Change Signal Over The Iberian Peninsula

Vara

Cabos

Sein

et al. 2021

Preprint

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In this work we use a regional ocean-atmosphere coupled model (RAOCM) and its stand-alone atmospheric component to gain insight into the impact of atmosphere-ocean coupling on the climate change signal over the Iberian Peninsula (IP). The IP is a well suited location for this study as high-resolution models are required to realistically reproduce its current and future climate. We find that under the RCP8.5 scenario, the generalized 2-m air temperature (T2M) increase by the end of the 21st century (2070-2099) in the atmospheric-only simulation is tempered by the coupling. The impact of coupling is specially seen in summer, when the warming is stronger. Precipitation shows regionally-dependent changes in winter, whilst a drier climate is found in summer. The coupling generally reduces the magnitude of the changes. Differences in T2M and precipitation between coupled and uncoupled simulations are caused by changes in the Atlantic large-scale circulation and in the Mediterranean Sea. Additionally, the differences in projected changes of T2M and precipitation with the RAOCM under the RCP8.5 and RCP4.5 scenarios are tackled. Results show that in winter and summer T2M increases less and precipitation changes are of a smaller magnitude with the RCP4.5. Whilst in summer changes present a similar regional distribution in both runs, in winter there are some differences in the NW of the IP due to differences in the North Atlantic circulation. The differences in the climate change signal from the RAOCM and the driving Global Coupled Model shows the added value of regionalization in terms of higher resolution over the land and ocean.

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“…The Black Sea and river runoff water inputs were prescribed from the climatological average of interannual data from Ludwig et al (2009). Water exchange was in good approximation of a closed Mediterranean Ocean basin, with the Atlantic Ocean relaxed to the Levitus et al (2005) climatology prescribed in the buffer zone.…”

Section: Ocean Modelmentioning

confidence: 99%

“…The figure shows that both the coupled and uncoupled systems represent a similar positive trend and have strongly intercorrelated time series. To better understand how the 2 m air temperature of the coupled system responds to changes in the SST, Kelemen et al (2019) ran a few sensitivity experiments using perturbed SST in the uncoupled system. They showed a positively oriented impact of SST disturbance on 2 m air temperatures.…”

Section: M Air Temperaturementioning

confidence: 99%

A regional atmosphere–ocean climate system model (CCLMv5.0clm7-NEMOv3.3-NEMOv3.6) over Europe including three marginal seas: on its stability and performance

et al. 2019

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Abstract. The frequency of extreme events has changed, having a direct impact on human lives. Regional climate models help us to predict these regional climate changes. This work presents an atmosphere–ocean coupled regional climate system model (RCSM; with the atmospheric component COSMO-CLM and the ocean component NEMO) over the European domain, including three marginal seas: the Mediterranean, North, and Baltic Sea. To test the model, we evaluate a simulation of more than 100 years (1900–2009) with a spatial grid resolution of about 25 km. The simulation was nested into a coupled global simulation with the model MPI-ESM in a low-resolution configuration, whose ocean temperature and salinity were nudged to the ocean–ice component of the MPI-ESM forced with the NOAA 20th Century Reanalysis (20CR). The evaluation shows the robustness of the RCSM and discusses the added value by the coupled marginal seas over an atmosphere-only simulation. The coupled system is stable for the complete 20th century and provides a better representation of extreme temperatures compared to the atmosphere-only model. The produced long-term dataset will help us to better understand the processes leading to meteorological and climate extremes.

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Added Value of Atmosphere-Ocean Coupling in a Century-Long Regional Climate Simulation

Cited by 18 publications

References 33 publications

Is interactive air sea coupling relevant for simulating the future climate of Europe?

Is interactive air sea coupling relevant for simulating the future climate of Europe?

Impact of Air-Sea Coupling on the Climate Change Signal Over The Iberian Peninsula

A regional atmosphere–ocean climate system model (CCLMv5.0clm7-NEMOv3.3-NEMOv3.6) over Europe including three marginal seas: on its stability and performance

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