Identification of Sources of Precipitation through an International Research Effort (INSPIRE)

Abstract

Extreme precipitation events can have severe impacts on society and the environment. Understanding what causes these events is a vital step toward better prediction and improved disaster preparedness. One research direction is to answer the question: Where did the moisture that rained here come from? The moisture sources for precipitation (i.e., where the moisture originally evaporated) cannot be measured directly and, therefore, a variety of different moisture-tracking methods have been developed and evolved over time. To better understand the uncertainty of these methods, we unite the community to advance common understanding and guidelines. As the first step, in this study, we quantify moisture sources of three extreme precipitation events using methods obtained from 14 different research groups. These three events cover different meteorological conditions: monsoon precipitation in Pakistan, convective precipitation in Australia, and atmospheric river-associated precipitation over Scotland. We find that for the three cases, the different moisture-tracking methods qualitatively agree in moisture source patterns, but there are regional and quantitative differences. For example, for the Pakistan case, the recycling ratio shows a multimethod spread of 2%–20%. We also find similar behavior across methods for the three different events, where methods consistently show either more recycling or more sources further away from the precipitation region. This coordinated model intercomparison facilitates the explanation and quantification of uncertainty, acting as a point of reference and inspiration for future work and literature on moisture tracking.