Total Storm Conduction Currents Derived Using a Global Climate Model

Abstract:

Electrified clouds are known to play a major role in the global electric circuit. These clouds produce upward currents from the top of thunderstorms which help maintain the potential difference between earth’s surface and the upper atmosphere. Previously, currents for different types of electrified clouds were estimated from overflights of the NASA ER-2 aircraft and compared with radar derived dynamical and microphysical properties. In this study, model output from two simulations of the Community Earth System Model (CESM) are compared with conduction currents and other data derived from the lightning imaging sensor (LIS) and precipitation radar (RP) onboard the Tropical Rainfall Measuring Mission (TRMM) satellite. The intention is to determine CESM’s skill at representing these microphysical and dynamical properties of storms as well as to infer the global distributions of conduction currents over different spatial scales.

Several variables from CESM were examined, including convective mass flux, in cloud ice water path, and convective precipitation. All three variables show a relationship with the derived currents based on TRMM measurements, yet these vary across different regimes and spatial scales. As will be shown, using the derived relationships, the total conduction current from CESM represents averaged diurnal variations of the fair weather electric field well. Also, averaged annual, monthly and diurnal variations of conduction currents will be shown for different regions of the world.