Abstract
Abstract. The sixth version of the Model for Interdisciplinary Research on Climate (MIROC), called MIROC6, was cooperatively developed by a Japanese modeling community. In the present paper, simulated mean climate, internal climate variability, and climate sensitivity in MIROC6 are evaluated and briefly summarized in comparison with the previous version of our climate model (MIROC5) and observations. The results show that the overall reproducibility of mean climate and internal climate variability in MIROC6 is better than that in MIROC5. The tropical climate systems (e.g., summertime precipitation in the western Pacific and the eastward-propagating Madden–Julian oscillation) and the midlatitude atmospheric circulation (e.g., the westerlies, the polar night jet, and troposphere–stratosphere interactions) are significantly improved in MIROC6. These improvements can be attributed to the newly implemented parameterization for shallow convective processes and to the inclusion of the stratosphere. While there are significant differences in climates and variabilities between the two models, the effective climate sensitivity of 2.6 K remains the same because the differences in radiative forcing and climate feedback tend to offset each other. With an aim towards contributing to the sixth phase of the Coupled Model Intercomparison Project, designated simulations tackling a wide range of climate science issues, as well as seasonal to decadal climate predictions and future climate projections, are currently ongoing using MIROC6.
Highlights
Because observations are obtained concurrently with the progress of global warming due to increasing anthropogenic radiative forcing, the model climate under preindustrial conditions may not be adequate for use when making comparisons with recent observations
The root mean squared (RMS) errors of typical variables in the climate models with respect to observations are much larger than the RMS differences between the model climatology in the preindustrial simulation and those in the last 30-year-long period in the historical simulations
The sixth version of a climate model, MIROC6, was developed by a Japanese climate modeling community aiming to contribute to CMIP6 through a deeper understanding of a wide range of climate science issues and seasonal to decadal climate predictions and future climate projections
Summary
As global warming due to increasing emissions of anthropogenic greenhouse gases progresses, global and regional patterns of atmospheric circulation and precipitation as well as temperature are projected to be drastically changed by the end of the twenty-first century (e.g., Neelin et al, 2006; Zhang et al, 2007; Bengtsson et al, 2009; Andrews et al, 2010; Scaife et al, 2012); the occurrence frequency of extreme weather events such as heat waves and droughts will be increased, and extratropical cyclones will be stronger than in the present (e.g., Mizuta, 2012; Sillmann et al, 2013; Zappa et al, 2013). MIROC5 is composed of T85L40 atmosphere and 1.4◦L50 ocean but with considerably updated physical and dynamical packages (Watanabe et al, 2010) These models have been used to study various scientific issues such as the detection of natural influences on climate changes (e.g., Nozawa et al, 2005; Mori et al, 2014; Watanabe et al, 2014), uncertainty quantification of climate sensitivity (e.g., Shiogama et al, 2012; Kamae et al, 2016), future projections of regional sea level rises (e.g., Suzuki et al, 2005; Suzuki and Ishii, 2011), and mechanism studies on tropical decadal variability (e.g., Tatebe et al, 2013; Mochizuki et al, 2016). The latest Earth system model version of MIROC with the global carbon cycle, whose physical core will be MIROC6, has been developed for CMIP6 towards a further wide range of issues regarding climate and societal applications (Hajima et al, 2019)
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