Exploring the ability of the variable-resolution Community Earth System Model to simulate cryospheric–hydrological variables in High Mountain Asia

Abstract

Abstract. Earth system models (ESMs) can help to improve the understanding of climate-induced cryospheric–hydrological impacts in complex mountain regions, such as High Mountain Asia (HMA). Coarse ESM grids, however, have difficulties in representing cryospheric–hydrological processes that vary over short distances in complex mountainous environments. Variable-resolution (VR) ESMs can help to overcome these limitations through targeted grid refinement. This study investigates the ability of the VR Community Earth System Model (VR-CESM) to simulate cryospheric–hydrological variables such as the glacier surface mass balance (SMB) over HMA. To this end, a new VR grid is generated, with a regional grid refinement up to 7 km over HMA. Two coupled atmosphere–land simulations are run for the period 1979–1998. The second simulation is performed with an updated glacier cover dataset and includes snow and glacier model modifications. Comparisons are made to gridded outputs derived from a globally uniform 1∘ CESM grid, observation-, reanalysis-, and satellite-based datasets, and a glacier model forced by a regional climate model (RCM). Climatological biases are generally reduced compared to the coarse-resolution CESM grid, but the glacier SMB is too negative relative to observation-based glaciological and geodetic mass balances, as well as the RCM-forced glacier model output. In the second simulation, the SMB is improved but is still underestimated due to cloud cover and temperature biases, missing model physics, and incomplete land–atmosphere coupling. The outcomes suggest that VR-CESM could be a useful tool to simulate cryospheric–hydrological variables and to study climate change in mountainous environments, but further developments are needed to better simulate the SMB of mountain glaciers.

Resolving Weather Fronts Increases the Large‐Scale Circulation Response to Gulf Stream SST Anomalies in Variable‐Resolution CESM2 Simulations

“…In this work, we use variable‐resolution (VR) simulations, where horizontal resolution is enhanced only in a region of interest, to evaluate the potential benefit of resolving mesoscale processes for atmospheric predictability stemming from persistent midlatitude SSTs. VR modeling is widely used in weather forecasting (e.g., Buizza et al., 2007), but it is only starting to be explored for simulating climate variability and change (e.g., Herrington et al., 2022; Schemm, 2023; van Kampenhout et al., 2019; Wijngaard et al., 2023; Zarzycki & Jablonowski, 2014; Zarzycki et al., 2015). Here, we use VR configurations of the spectral element (SE) dynamical core in the Community Atmosphere Model (CAM‐SE; P. H. Lauritzen et al., 2018), with 14‐km (∼1/8°) or 28‐km (∼1/4°) resolution over the North Atlantic and Europe (Figure 1), to model the large‐scale atmospheric circulation response to idealized North Atlantic SST anomalies.…”