Atmospheric rivers (ARs) are dynamically driven, filamentary structures that account for ~90% of poleward water vapor transport outside of the tropics, despite occupying only ~10% of the available longitude. They are often associated with extreme winter storms and heavy precipitation along the western coasts of mid-latitude continents and have the ability to produce major flooding events and/or relieve droughts. Because ARs play such an important role in the global hydrological cycle as well as to regional water resources, understanding how they may vary from subseasonal-to-interannual time scale and change in a warmer climate is critical to advancing understanding and prediction of regional precipitation.

The goal of ARTMIP is to understand and quantify uncertainties in atmospheric river (AR) science based on choice of detection/tracking methodology. The climatological characteristics of ARs, such as AR frequency, duration, intensity, and seasonality, are all strongly dependent on the method used to identify ARs. It is, however, the precipitation attributable to ARs that is perhaps most strongly affected, and this has significant implications for our understanding of how ARs contribute to regional hydroclimate now and in the future.

Goals of the 3rd ARTMIP Workshop are:

• Presentation of results from recent and ongoing ARTMIP research: Tier 1 and beyond (with a focus on Tier 2)

• Working discussion of current and future ARTMIP experiments and papers.

• Solicitation of expert identification of atmospheric rivers and other weather phenomena for machine learning.

The main outcome of the workshop will be to

• Produce a workshop report and summary paper describing the impacts that detection-method-uncertainty has on our understanding of atmospheric rivers – particularly with respect to impacts, variability, and trends.