Abstract
As part of the CORDEX project, the fifth-generation Canadian Regional Climate Model (CRCM5) is used over the Arctic for climate simulations driven by reanalyses and by the MPI-ESM-MR coupled global climate model (CGCM) under the RCP8.5 scenario. The CRCM5 shows adequate skills capturing general features of mean sea level pressure (MSLP) for all seasons. Evaluating 2-m temperature (T2m) and precipitation is more problematic, because of inconsistencies between observational reference datasets over the Arctic that suffer of a sparse distribution of weather stations. In our study, we additionally investigated the effect of large-scale spectral nudging (SN) on the hindcast simulation driven by reanalyses. The analysis shows that SN is effective in reducing the spring MSLP bias, but otherwise it has little impact. We have also conducted another experiment in which the CGCM-simulated sea-surface temperature (SST) is empirically corrected and used as lower boundary conditions over the ocean for an atmosphere-only global simulation (AGCM), which in turn provides the atmospheric lateral boundary conditions to drive the CRCM5 simulation. This approach, so-called 3-step approach of dynamical downscaling (CGCM-AGCM-RCM), which had considerably improved the CRCM5 historical simulations over Africa, exhibits reduced impact over the Arctic domain. The most notable positive effect over the Arctic is a reduction of the T2m bias over the North Pacific Ocean and the North Atlantic Ocean in all seasons. Future projections using this method are compared with the results obtained with the traditional 2-step dynamical downscaling (CGCM-RCM) to assess the impact of correcting systematic biases of SST upon future-climate projections. The future projections are mostly similar for the two methods, except for precipitation.
Highlights
Arctic regions have experienced amplified warming at twice the rate of the global average (ACIA 2004; IPCC 2013)
The aim of this study is to evaluate the performance of the CRCM5 over the Arctic domain following the CORDEX protocol
The skill of CRCM5 hindcast simulations driven by ERA-Interim reanalysis, the effectiveness of the large-scale spectral nudging (SN), and future climatechange projections using 2- and 3-step dynamical downscaling over the CORDEX Arctic domain were investigated
Summary
Arctic regions have experienced amplified warming at twice the rate of the global average (ACIA 2004; IPCC 2013). The Arctic sea ice has been in a sharp decline during the past decades. Km of Arctic sea ice loss per year is observed using satellites records (Ramsayer 2014). According to IPCC, the annual mean Arctic sea ice extent decreased over the period 1979–2012 with a rate of 3.5–4.1% per decade, and the decrease is more than three times larger (9.4–13.6%) for the summer sea ice minimum (IPCC 2013). The national snow and ice data center located in Colorado announced that Arctic sea ice extent in September 2016 is recorded as the second lowest yearly minimum since satellites record beginning in 1978, with 4.14 million
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