Extreme rainfall is a high impact weather phenomenon that profoundly affects people around the world, but our fundamental understanding and quantitative forecast skill for these events remains limited. To address these important scientific and forecast challenges, the Prediction of Rainfall Extremes Campaign In the Pacific (PRECIP) in summer 2020 will be conducted to improve our understanding of the multi-scale dynamic, thermodynamic, and microphysical processes that produce extreme precipitation. Observations will be collected by the NSF/National Center for Atmospheric Research's S-PolKa and Colorado State University's SEA-POL radars, radiosondes, and disdrometers from 25 May to 10 August 2019 during the latter period of the Meiyu season over Taiwan and transition to the early period of the tropical cyclone (TC) season.
The experimental design of PRECIP is motivated by four key factors: 1) a moisture-rich environment, 2) the presence of both complex terrain and an oceanic environment, 3) a dense operational observing network to augment the specialized field observations, and 4) a high frequency of a variety of heavy rainfall events. Taiwan and the western North Pacific region are a natural laboratory that optimizes all four of these criteria. With high total column water vapor in the region as a fundamental precondition, field observations will be used to test hypotheses related to the presence and roles of key ingredients and processes across scales in different heavy rainfall scenarios. PRECIP will be conducted in collaboration with the Taiwan-area Atmospheric and Hydrological Observation and Prediction Experiment (TAHOPE) and Japanese Tropical cyclones Pacific Asian Research Campaign for Improvement of Intensity estimations/forecasts (T-PARCII) to add additional synergistic research observations to the campaign.
PRECIP seeks to improve our fundamental understanding and prediction of the processes that produce extreme precipitation through an ingredients-based physical framework. Research observations will be collected in four event types that meet a global definition of 'extreme' across a spectrum of rainfall intensity and duration: deep convective cores, wide convective cores, broad stratiform regions, and TCs. The field campaign is innovative in its approach to investigate the universal aspects of extreme rainfall by testing hypotheses that are not directed at only one weather phenomenon, and are therefore transferable to rainfall events that affect the United States. The experiment is designed to maximize the chances of observing a variety of heavy rainfall events in the moisture-rich natural laboratory of Taiwan and western North Pacific in order to find the commonalities. The primary objective is to simplify the complexity of multi-scale interactions by identifying key ingredients and processes in the limiting cases of high intensity and long duration events in a moisture-rich environment. Field measurements will be made to address basic research questions about key ingredients, physical processes, mesoscale structures, and prediction improvement. The core observations will consist of multi-frequency radars, radiosondes, disdrometers, and the Taiwan operational weather network that will be integrated with modeling and data analysis and assimilation to better understand the mechanisms that produce extreme rainfall.
Improved forecasts and understanding of the predictability of heavy rainfall will lead to better warnings and risk communication that will have a strong positive impact on society. Improvements to our understanding of orographic and non-orographic precipitation, physical processes, and model capabilities will have broad application to improve other related weather and climate predictions. The PRECIP dataset will also lead to positive impacts in precipitation estimation, data assimilation, radar meteorology, and hydrology. Concurrent projects with TAHOPE and T-PARCII will strengthen international science collaboration in our common goal of improved extreme weather prediction and will help facilitate the application of the campaign findings toward operations in the future. The joint projects will occur during the period leading up to and including the 2020 Tokyo Olympics. The Olympics will naturally enhance the broader impacts of the PRECIP research, and will provide a focal point for education and outreach promoting the positive role of science to address global problems such as extreme weather. Additional positive broader impacts are expected for graduate students, early career scientists, and underrepresented groups through mentoring, international science collaborations, and leadership opportunities in the field.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
