Utility for Improved Cloud and Precipitation Process Modeling

Executive Summary Water is necessary for all life on Earth. Thus it is vital for all civilization to know where, when and how clouds form, whether they precipitate or not, and how those patterns may change in a future climate. Central to this required knowledge are better predictions of atmospheric water at all scales. This necessitates a paradigm shift away from our current practices that largely observe states to future observing strategies that can deliver information on both states and the processes that govern model physics and prediction skill. The new insights afforded by these process-oriented measurements can inform the next generation of cloud and precipitation models for weather forecasting and climate change. Our Earth Science Objective is to considerably improve the accuracy of cloud-precipitation processes in Earth system models at scales from microphysical to regional to global. Currently in 2016, Cloud Resolving Models (CRMs, i.e., any numerical model that explicitly resolves convective motions and/or microphysics) are at a roadblock and cannot improve without observational constraints to assess the fidelity of existing microphysical schemes and processes (e.g., Hagos et al., 2014, Bassill 2014, Stephens and Ellis, 2008), or to point in the direction of new ground breaking formulations. The geophysical variables we aim to measure include cloud and precipitation particle vertical velocities and microphysical properties, particularly of ice particles. These are key for improving climate and weather forecasting models currently and in the coming decades when these models will be able to explicitly resolve microphysical processes at convective updraft scales (e.g., Hagos et al., 2014, Popkin, 2014). The importance of these observations comes in their ability to inform and constrain models so as to better understand and predict the Earth’s Water and Energy cycles for our everyday lives and long-term future. The utility of the proposed measurements brings much needed constraints to allow for improvements in our ability to assess the availability of fresh water from precipitation and to examine the occurrence and characteristics of extreme-weather. The quality of the measurements to address these shortcomings is high. Indeed we contend that without these measurements models cannot measurably improve. In terms of affordability, the specifications for our geophysical measurements remain flexible and we are committed to finding the most cost effective approach to meet our baseline science objectives. This Cloud and Precipitation input to the 2017-2027 Earth Science Decadal Survey Request for Information (RFI#2) is drawn from nearly 3 years of team discussions and several workshops from what we are calling the Cloud and Precipitation Process Measurements (CAPPM) group (URL http://pmm.nasa.gov/CAPPM). The traceability from science requirements to measurements has benefitted from the activities funded by the Aerosol, Cloud, Ecosystem (ACE) study, a mission recommended by the 2007 Decadal Survey. This CAPPM RFI is complementary to Aerosol-Cloud RFI inputs. Our key geophysical measurements of cloud and precipitation processes needed for models are cross cutting for the following Decadal Survey theme panels: I. Global Hydrological Cycles and Water Resources, II. Weather and Air Quality: Minutes to Subseasonal, and IV. Climate Variability and Change: Seasonal to Centennial. Precipitation and clouds are inherently linked to these three theme panels.