Development and Release of CESM2

Development and Release of CESM2

A new version of the Community Earth System Model (version 2; CESM2) was released to the community in early June 2018. This new version contains many substantial science and infrastructure improvements and capabilities for use of the broader CESM and international community. These new advancements include: an atmospheric model component that incorporates significant improvements to its turbulence and convection representations, opening the way for an analysis of how these small-scale processes can impact the climate; improved ability to simulate modes of tropical variability that can span seasons and affect global weather patterns; a land ice sheet model component for Greenland that can simulate the complex way the ice sheet moves and does a better job of simulating calving of the ice into the ocean; a global crop model component that can simulate both how cropland affects regional climate, including the impacts of increased irrigation, and how the changing climate will affect crop productivity; a wave model component that simulates how wind creates waves on the ocean, an important mechanism for mixing of the upper ocean; an updated river model component that simulates surface flows across hill sides and into tributaries before entering the main river channel; and a new set of infrastructure utilities that provide many new capabilities for easier portability, case generation and user customization, testing functionality, and greatly increased robustness and flexibility. A full list of updates with more technical descriptions is available at:
http://www.cesm.ucar.edu/models/cesm2/whatsnew.html

An incremental release of CESM2 (CESM2.1) is planned for late November 2018. This release will include additional model configurations, forcing data sets, and diagnostics output needed for Coupled Model Intercomparison Project phase 6 (CMIP6) and various Model Intercomparison Project (MIP) simulations that the CESM community is participating in.

Figure: Image from a global CESM2 historical simulation
Figure: This image from a global CESM2 historical simulation shows key aspects of the Arctic climate system. The speed at which simulated glacier ice flows over Greenland is represented, with warmer colors indicating faster speeds. The September 2005 sea ice concentration is depicted in gray scale, with white indicating higher ice concentrations. The time series of September mean sea ice extent simulated by CESM2 is in good agreement with the satellite observations provided by the National Snow and Ice Data Center for the late 20th century and early 21st century, with both showing the recent sea ice decline.