[DSRP Evidence](https://dsrpevidence.org/)

# Global Kilometer-Scale Simulations with ARP-GEM2: Effect of Parameterized Convection and Calibration

Olivier Geoffroy, David Saint-Martin, 2026, Journal of Climate — Climatology

Patterns: [Systems](https://dsrpevidence.org/pattern/systems), [Relationships](https://dsrpevidence.org/pattern/relationships)

## In short

The finding shows that the atmosphere's small-scale convective processes (parts) remain important to the whole system's simulated behavior even as resolution becomes very fine, with the global (whole) climate's mean state and variability shaped by how these smaller-scale parts are represented, involving a trade-off between the two.

## What they found (results)

Parameterized convection continued to significantly affect the model's representation of the mean atmospheric state even at kilometer-scale (2.6 km) resolution, with entrainment/detrainment values driving the gradual reduction of parameterized convection as resolution increased, and a compromise required between representing the mean state well and reproducing climate variability.

## What they set out to do (purpose)

To document a new global atmospheric model (ARP-GEM2) calibrated at kilometer-scale resolution and to test the effect of parameterized convection on the model's representation of mean climate state and variability as resolution increases.

## Abstract

The objective of this paper is twofold. First, it documents the second version of the global atmospheric model ARP-GEM and its calibration at kilometer-scale resolution. The model is currently able to run simulations at a resolution of up to 1.3 km. Second, this paper focuses on multiyear global atmospheric simulations at a 2.6-km resolution with and without parameterized convection and associated calibration. Simulations without deep convection tend to be similar to those with infinite, or at least large, entrainment values. Consistently, entrainment and detrainment can be used as primary drivers for the gradual reduction of convection as resolution increases. The results indicate that, in this hydrostatic model, parameterized convection still plays a significant role in the correct representation of the mean state at the kilometer scale. Additionally, they suggest some added value of high resolution in representing climate variability. However, a compromise between the adequate representation of the mean state and variability is necessary, as both are differently favored by the degree of parameterized convection.

These researchers were not testing DSRP. The finding is theirs; the correspondence to DSRP is drawn by this site.

[Source](https://doi.org/10.1175/JCLI-D-25-0650.1)