Numerical models of Earth's climate system have been gaining more and more complexity over the last decades. Therefore, it is important to establish simplified models to improve process understanding. In our study, we present and document the development of a new simplified model set-up within the framework of a complex climate model system that uses the same routines to calculate atmospheric dynamics as the complex model, but is simplified in the representation of clouds and radiation.

Microbes drive carbon (C) and nitrogen (N) transformations in soil, and soil models have started to include explicit microbial physiology and functioning to try to reduce uncertainty in soil-climate feedbacks. Here, we add N cycling to a microbially-explicit soil C model and reproduce C and N dynamics in soil during litter decomposition across a range of sites. We discuss model-generated hypotheses about soil C and N cycling and highlight the need for landscape-scale model evaluation data.

This paper describes the updated submodel AirTraf 2.0 which simulates global air traffic in the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. Nine aircraft routing options have been integrated, including contrail avoidance, minimum economic costs, and minimum climate impact. Example simulations reveal characteristics of various routing options on air traffic performances. The consistency of the AirTraf simulations is also verified with literature data.

This manuscript presents FALL3D-8.0, the last version release of an open-source code with 15+ years of track record and a growing number of users in the volcanological and atmospheric communities. The code, originally conceived for atmospheric dispersal and deposition of tephra particles, has been extended to model other types of particles, aerosols and radionuclides. This paper details the FALL3D-8.0 model physics and the numerical implementation of the code.

Climate models need to capture sea ice complexity to represent it realistically. Here, we test whether the distribution of sea ice in different thickness categories in the NEMO3.6-LIM3 model impacts how sea ice variability is simulated. Comparison between simulations and satellite observations is done using k-means clustering in sea ice concentration in winter and summer between 1979 and 2014 at both poles. Though some improvements are discussed, we recommend the standard number of 5 categories.

Using the super-droplet method, we constructed a detailed numerical model of mixed-phase clouds based on kinetic description and subsequently demonstrated that a large-eddy simulation of a cumulonimbus which predicts ice particle morphology without assuming ice categories or mass-dimension relationships is possible. Our results strongly support the particle-based modeling methodology’s efficacy for simulating mixed-phase clouds.

Our paper describes IPSL-CM5A2, an earth system model that can be integrated for long (several thousands of years) climate simulations. We describe the technical aspects, assess the model computing performances and evaluate the strengths and weaknesses of the model, by comparing pre-industrial and historical runs to the previous generation model simulations and to observations. We also present a Cretaceous simulation as a case-study to show how the model simulate deep time paleoclimates.

Wind farms can briefly impact their near-environment by reducing wind speeds and mixing warmer air down to the surface. The wind farm parameterization (WFP) in the Weather Research and Forecasting (WRF) model is a tool that numerically simulates wind farms and these meteorological impacts. We highlight the importance of choice in model settings and find that sufficiently fine vertical and horizontal grids with turbine-turbulence are needed to accurately simulate wind farm meteorological impacts.

Eight thousand years ago, the N. hemisphere cooled by several degrees for a century, due to the collapse of an ice sheet in N. America that released large amounts of meltwater to the North Atlantic and slowed down its circulation. We numerically model the ice sheet to understand its evolution during this event. Our results match data thanks to good ice dynamics, but depend mostly on surface melt and snowfall. Further work will help us understand how past and future ice melt affects climate.

Performing seasonal simulations on horizontal grid resolutions of a few kilometers over the entire globe remains challenging. We demonstrate the added value of simulating large-scale patterns and feedbacks at 3 km resolution compared to a coarser resolution forecast using the WRF numerical weather model on a latitude-belt domain. Results show an improvement of cloud coverage in the tropics, better representation of teleconnection, and improvements of precipitation patterns in different regions.

Our study aims to include the water needs and uses for both society and nature into a hydrological model, in order to enable world-wide assessments of sustainable water use. The model was extended to include irrigation, drinking-water, industrial, energy and livestock water uses, as well as minimum flow requirement for natural systems. First results showed competition for water resources between society and nature, especially for groundwater withdrawals.