Improving understanding and prediction of the mountain water cycle – overview and initial results from the INARCH Common Observation Period Experiment, 2022–2024

The International Network for Alpine Research Catchment Hydrology (INARCH, https://inarch.usask.ca) is a cross-cutting project of the GEWEX Hydroclimatology Panel (GHP) to better understand alpine cold regions hydrological processes, improve their prediction, diagnose their sensitivities to global change, and find consistent measurement strategies.  At its core is a global network of 38 highly-instrumented mountain observatories and experimental research sites in 18 countries and six continents, which are testbeds for detailed process studies on mountain hydrology and meteorology, developing and evaluating numerical simulation models, validating remotely sensed data, and observing, understanding, and predicting environmental change.  INARCH has completed a Common Observing Period Experiment (COPE) over the period 2022–2024, collecting high-quality measurements along with supplementary observations and remote sensing campaigns, to produce a common, coherent, and well-documented and described data set of mountain meteorology and hydrology.  These data will be used to address key INARCH science questions and for a series of hydrological process diagnostic modelling evaluations and analyses.  The aim is to better understand why models produce various behaviours and to see if models benchmark various known aspects and regimes of the coupled atmospheric-cryospheric-hydrological system.  Model diagnostic evaluations will emphasize atmospheric, snow, glacier, and water processes in high mountain terrain and include sparse forest, non-needleleaf vegetation, glaciated, and alpine windblown sites.  This has not been done globally in alpine regions and could be potentially very powerful.  The presentation will discuss progress in the COPE, an overview of the data management and initial results, and next steps in the analyses.