Measuring Vertical Mass Flux in Convection: Lessons Learned from a Convection-Resolving Ensemble

The vertical transport of water and air in deep convection is a critical component of many types of severe weather, and has a substantial influence on the Earth’s climate system. Despite decades of research, the representation of vertical transport remains a major source of error in weather and climate models. This is due in large part to the fact that there are no global observations of vertical mass transport in deep convection. The 2017 National Academies Decadal Survey for Earth Science and Applications from Space has placed a high priority on observations of convective mass transport, and several novel measurement approaches are currently being considered.

Development of new measurement techniques often includes observing system simulation experiments (OSSEs), based on numerical weather prediction (NWP) models and metrics derived from data assimilation systems. However, use of NWP OSSEs for deep convection suffers from limitations in both forecast models and DA systems. Our approach uses a large ensemble of high resolution simulations of deep convection in a variety of different environments, and for a spectrum of convective morphologies, to evaluate potential measurement techniques. This ensemble, when coupled with instrument simulators, allows quantitative evaluation of the effectiveness of various observations related to convective vertical mass flux.

This presentation will provide an overview of our ensemble simulation methodology, as well as various approaches that may be used to evaluate new measurement techniques. We base our analysis on the fundamentals of convective dynamics, relating measurements of vertical mass flux to terms in the water budget of deep convection. Our results indicate robust relationships between net vertical flux of water and time resolved space-borne measurements.