The Joint IPWG/GEWEX Precipitation Assessment

This report is a result of an interesting journey that originated in discussions between Rémy Roca, chair of Global Energy and Water Exchanges (GEWEX) Data and Analysis Panel (GDAP), and Ziad Haddad, chair of International Precipitation Working Group (IPWG), during visits to Toulouse and to Pasadena as well as during many of the various workshops and conferences dedicated to precipitation. It culminated in the present report built from contributions by more than 20 scientists from all over the world. The first written draft was completed immediately following an open meeting for interested contributors that took place on a Saturday morning in a public library in the heights of San Diego (Haddad and Roca, 21 October 2017). From this initial plan, many objectives were successfully achieved without modification, while a few required maturation before we were able to include them in the completed assessment, all of this in spite of the ongoing pandemic. The current report completes the GEWEX assessment portfolio and follows the previous IPWG assessment by 10+ years (Gruber and Levizzani, 2008). Hopefully it is the first of a more frequent and regular series of precipitation assessments.