This special issue serves as a collection point for articles describing datasets associated with field campaigns taking place across the East River Watershed of Colorado over the last few years. This includes the Study of Precipitation, the Lower Atmosphere, and Surface for Hydrometeorology (SPLASH), the Surface Atmosphere Integrated Field Laboratory (SAIL), the Sublimation of Snow (SOS) Project, and activities associated with the Watershed Function Science Focus Area (SFA) program. These projects have jointly supported the development of one of the most heavily observed mountainous watersheds in North America by collaboratively collecting observations of atmospheric and surface processes that influence mountainous hydrology in the Upper Colorado River Basin. These projects, primarily sponsored by the National Oceanic and Atmospheric Administration (NOAA), the U.S. Department of Energy (DOE), and the National Science Foundation (NSF), deployed a wide variety of instruments focused on a ~30 km transect around Crested Butte, Colorado, including surface based in situ and remote sensors, as well as mobile sensor systems on aircraft and surface vehicles. Additional data were collected across the broader region using aircraft to offer context for the observations collected in the East River watershed. Instrumentation was deployed by numerous groups, including four different NOAA laboratories, the DOE Atmospheric Radiation Measurement (ARM) program, the National Center for Atmospheric Research (NCAR) Earth Observing Laboratory (EOL), Lawrence Berkeley National Laboratory, US and international university partners, and private industry. In addition, several groups have completed numerical simulations over the operational area in connection with these projects. Informal collaborations have been additionally supported by the formation of a SPLASH–SAIL–SOS (S3) research community to advance atmospheric and surface science with these datasets. This S3 group has already undertaken an initial workshop, held in Boulder, Colorado, in November 2023, to plan scientific research that can leverage data from these different projects. This Earth System Science Data special issue enables a comprehensive survey of the diverse set of observations, datasets, and modeling results that have already been produced and is timely and necessary to serve as a central reference for both project participants and the international mountain hydrology and hydrometeorology research communities. The special issue includes invited and contributed papers related to datasets collected and developed as part of the projects listed above.

Review process: all papers of this special issue underwent the regular interactive peer-review process of Earth System Science Data handled by members of the editorial board as well as guest editors designated by the ESSD chief editors.

Guest editor details:

Gijs de Boer is the PI for the recently-completed Study of Precipitation, the Lower Atmosphere, and Surface for Hydrometeorology (SPLASH) project. SPLASH took place in the East River Watershed and is a significant source of data in this region. Dr. de Boer has an extensive scientific publication record on lower atmospheric processes, including over 80 peer-reviewed publications and several data papers. Additionally, he has previously served as a guest editor for two other ESSD special issues, and has extensive experience with the collection, curation, and publication of data.

Jessica Lundquist is the PI for the NSF-funded Sublimation of Snow (SOS) field campaign in the East River Watershed, and is currently working on two Department of Energy projects in the same location. Professor Lundquist is the author of over 110 peer-reviewed publications, with an h-index of 50. She has served as an Editor of Water Resources Research, during which time she was lead editor on a special issue on snow, and as an Associate Editor for the Journal of Hydrometeorology, for which she was awarded the Editor's award for the quality of her reviews. Professor Lundquist has extensive experience with data papers, through both publishing her own datasets and as the editor in charge of reviewing others' datasets.

Daniel Feldman is the PI for the DOE-funded Surface Atmosphere Integrated field Laboratory (SAIL) field campaign in the East River Watershed, and is currently working with the Department of Energy's Atmospheric System Research (ASR) and the Atmospheric Radiation Measurement (ARM) Programs on advancing science using a wide variety of the SAIL datasets. Dr. Feldman is the author of over 30 peer-reviewed publications He has served as an Associate Editor of the Journal of the Atmospheric Sciences, a Guest Editor for Remote Sensing, and currently serves on the Editorial Board in Frontiers in Environmental Science. Dr. Feldman has written and participated in data papers, and he works closely with and advises the Department of Energy's ARM Data Center that provides data, metadata, and resources to analyze those data to the public. He also works with the Department of Energy's Environmental System Science Data Infrastructure for a Virtual Ecosystem (ESS-DIVE) and other agencies, including NASA, NOAA, and NSF to support the dissemination of data and the provision of information on those data in peer-reviewed publication.

Charuleka Varadharajan is the PI for U.S. Department of Energy's data repository, the Environmental Systems Science Data Infrastructure for a Virtual Environment (ESS-DIVE). She also leads the hydrology and data management components for the DOE's Watershed Function SFA, which has collected extensive, interdisciplinary measurements in the region since 2015 and produced several public datasets. Dr. Varadharajan has published extensively on topics related to hydrology, biogeochemistry and data sciences, and specifically has published a data paper on some of the measurements in the region. As PI of a data repository and lead of large DOE project data science and management teams, she has extensive experience with the curation, and publication of data.