Polarimetric Radar & Lightning Analysis and High Resolution Simulations to Support TRACER Science Goals

Lead PI: Dr. Marcus van Lier-Walqui

Unit Affiliation: Center for Climate Systems Research (CCSR)

September 2020 - September 2021
Project Type: Research

DESCRIPTION: It has been controversially hypothesized that climate models are widely missing an important element of anthropogenic radiative forcing by neglecting aerosol impacts on deep convection. At the same time, increasing evidence indicates that commonly dominant ice crystal generation mechanisms are missing from even the most detailed microphysics schemes. In addition, the dynamical foundations of many convective parameterizations (plume physics) are being revisited, with increasing evidence that the physics of thermals better describe the fundamental aspects of convective dynamical processes. DOE’s Tracking Aerosol Convection Interactions ExpeRiment (TRACER) campaign has been designed to simultaneously address these knowledge gaps by providing measurements that will constrain aerosol properties in the vicinity of isolated convective cells that will be simultaneously observed with a multi-wavelength polarimetric radar network, including rapid scan approaches that should be able to directly observe dynamical processes in fine detail. Since rapid scanning of tracked isolated cells has rarely been attempted, however, — and never to our knowledge with the additional objective of detecting response to varying aerosol — optimal scanning strategies have not yet been established. A related objective of TRACER is rapid and high-resolution detection of lightning flash rate, size, and energy, which are coupled to the kinematic and microphysical spectra of mixed-phase clouds, via Lightning Mapping Array (LMA) observations. Here we propose to establish an initial science framework that connects cell-tracking radar measurements, lightning measurements, and high-resolution forecast modeling during the TRACER campaign. Objectives will be to better establish leading observational targets before the IOP period (e.g., most relevant height range for radar scanning, general size of identifiable observable elements, relationship to flash activity), conduct daily forecast simulations during the IOP period for operational readiness, and evaluate initial results and troubleshoot as the IOP period progresses. This will be accomplished by enhancements to the Houston LMA (2 additional stations), detailed analysis of lighting and polarimetric radar, and a comprehensive modeling study using the NASA-Unified Weather Research and Forecasting (NU-WRF) model with lighting-predicting microphysics. Thunderstorms will be tracked in two dimensions, and three-dimensional thermal tracking will be performed on simulated storms. Analysis will be organized around a conceptual model for the microphysical and dynamical evolution of isolated thunderstorm cells in the Houston region.

OUTCOMES: Our work will shed light on poorly-understood processes that occur in isolated thunderstorms, linking the dynamical features of updraft thermals to their associated microphysical processes (e.g. initial formation of rain, glaciation, and production of graupel through riming), as well as the closely related processes of thunderstorm electrification, and their modulation by environmental aerosols. Observational and modeling analysis will be linked through a conceptual model of updrafts and isolated thunderstorm evolution. This will effectively inform targeting of observational resources during the TRACER field campaign. Enhanced gridded radar and lightning products will be produced, and a large database of high-resolution, lighting-aware, modeling studies will also be made available to the community.