Polarimetric radar & lightning analysis and high resolution simulations to support TRACER science goals

Polarimetric radar & lightning analysis and high resolution simulations to support TRACER science goals

Marcus van Lier-Walqui, Center for Climate Systems Research, Columbia University & NASA Goddard Institute for Space Studies (Principal Investigator)

Toshi Matsui, ESSIC, University of Maryland, Collegepark & NASA Goddard Space Flight Center, (Co-Investigator)

Takamichi Iguchi, ESSIC, University of Maryland, Collegepark & NASA Goddard Space Flight Center, (Co-Investigator)

Eric Bruning, Texas Tech University, (Co-Investigator)

Ann Fridlind, NASA Goddard Institute for Space Studies, (Co-Investigator)

Motivation: It has been controversially hypothesized that climate models are widely missing an important element of anthropogenic radiative forcing by neglecting aerosol

aerosols

Small particles or droplets, such as wildfire smoke, volcanic gases, or salty sea spray, that float in the air. They are emitted by both natural events and human activities.

Source: NASA Global Climate Change Source

impacts on deep convection.

convection

The rising of warm air and the sinking of cool air. Convection can cause local breezes, winds, and thunderstorms.

Source: NASA earth observatory Source

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.