Abstract
Abstract. The Nonhydrostatic ICosahedral Atmospheric Model (NICAM), a global model with an icosahedral grid system, has been under development for nearly two decades. This paper describes NICAM16-S, the latest stable version of NICAM (NICAM.16), modified for the Coupled Model Intercomparison Project Phase 6, High Resolution Model Intercomparison Project (HighResMIP). Major updates of NICAM.12, a previous version used for climate simulations, included updates of the cloud microphysics scheme and land surface model, introduction of natural and anthropogenic aerosols and a subgrid-scale orographic gravity wave drag scheme, and improvement of the coupling between the cloud microphysics and the radiation schemes. External forcings were updated to follow the protocol of the HighResMIP. A series of short-term sensitivity experiments were performed to determine and understand the impacts of these various model updates on the simulated mean states. The NICAM16-S simulations demonstrated improvements in the ice water content, high cloud amount, surface air temperature over the Arctic region, location and strength of zonal mean subtropical jet, and shortwave radiation over Africa and South Asia. Some long-standing biases, such as the double intertropical convergence zone and smaller low cloud amount, still exist or are even worse in some cases, suggesting further necessity for understanding their mechanisms, upgrading schemes and parameter settings, and enhancing horizontal and vertical resolutions.
Highlights
Moist processes play a crucial role in the formation of the earth’s climate
The most noticeable impact was an increase in ice water content (IWC) by more than 2-fold (Fig. 5e), and this mostly accounts for the snow category in the cloud microphysics scheme
NICAM16-S still shows strong negative biases in outgoing longwave radiation (OLR) over the tropical to subtropical regions and outgoing shortwave radiation (OSR) over the subtropical high-pressure belt at the TOA compared with the Clouds and Earth’s Radiant Energy Systems (CERES) product (Fig. 8, black versus red curves), and these biases are qualitatively similar to those simulated in Nonhydrostatic ICosahedral Atmospheric Model (NICAM).12 (Kodama et al, 2015)
Summary
Moist processes play a crucial role in the formation of the earth’s climate. Moist convection redistributes mass, energy, and momentum of the atmosphere to form large-scale circulation. Kodama et al (2015) and Satoh et al (2015) provided brief descriptions of the model (hereafter referred to as NICAM.12) and experimental design of the climate simulations This unique dataset of the high-resolution climate simulation, whose overall performance was reported. NICAM. has been further modified to support the external forcings of natural and anthropogenic aerosols and the solar cycle defined in the Coupled Model Intercomparison Project Phase 6 (CMIP6) High Resolution Model Intercomparison Project (HighResMIP) protocol (Haarsma et al, 2016). This special version of NICAM. for HighResMIP is labeled NICAM16-S, where “-S” represents the use of a single-moment cloud microphysics scheme.
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