Multi-decadal CESM2-Large Ensemble direct downscaled reference and mid 21st century hydroclimate simulations Alaska and the Yukon at 4 kilometer (km) resolution

### Access
Files be accessed and downloaded from the directory via: [http://arcticdata.io/data/10.18739/A2DJ58J94](http://arcticdata.io/data/10.18739/A2DJ58J94).
### Overview
We present a novel, high-resolution land-atmosphere regional climate model (RCM) configuration for Alaska and Yukon River basin. The Regional Arctic System Model (RASM) was reconfigured from its 50 kilometer (km) grid-spacing to 4 km and coupled to the Community Terrestrial Systems Model (CTSM) with hydrology specific optimization providing improved treatment of orographic precipitation, spatial heterogeneity of the landscape, and improved surface and sub-surface processes particularly tailored to cold regions. The new RASM configuration was used to dynamically downscale four Community Earth System Model version 2-Large Ensemble (CESM2-LE) climate model members for reference (model timestamp water year (WY) 1991-2021) and mid-century (WY2035-2065) time-slices. We performed a simple bias correction to the CESM2-LE specific humidity, with vertical variations, to reduce a high precipitation bias when using the CESM2-LE data directly. The simulations have resulted in a unique high-resolution small ensemble of the hydroclimate over Alaska and the Yukon that can be used for studying atmospheric and hydrologic processes, and assessing impacts related to climate variability and change across the region. Hourly, three-hourly, daily, and monthly outputs are available for surface precipitation, temperature, streamflow, and snowpack, among many other variables. A companion dataset (https://doi.org/10.5065/ZPSB-PS82) is available that provides an ERA5 forced historical (WY1991-2021) and two future pseudo global warming simulations with the same outputs and future time slices.
### Model Scripts and Example Run
An example of model inputs, scripts, and outputs are available through the Arctic Data Center at [https://doi.org/10.18739/A2RN3094N](https://doi.org/10.18739/A2RN3094N).
### Citation
The corresponding description paper is Newman et al. (2026) and we appreciate it if users cite both this dataset and the description paper when basing outcomes or analysis on this work.