Droplet charging in stratiform clouds

TL;DR

This study investigates droplet charge in stratiform clouds using remote sensing and balloon data, revealing typical negative polarity at cloud bases and variability in charge distribution, which impacts cloud microphysics and climate models.

Contribution

The paper introduces a new remote sensing method to measure droplet charge and provides detailed vertical charge structure data for stratiform clouds.

Findings

Charge at cloud base is typically negative.

Vertical charge structure aligns with theoretical predictions.

Observed variability in droplet charge distribution.

Abstract

The role of droplet charge in stratiform clouds is one of the least well understood areas in cloud microphysics and is thought to affect cloud radiative and precipitation processes. Layer clouds cover a large proportion of the Earth's surface and are important in regulating the planetary radiation budget. Using a new remote sensing method developed at our University Observatory, we demonstrate that charge in the base of stratiform clouds is typically of negative polarity, as expected from theory considering the vertical current flow into and out of the cloud. More detailed vertical charge structure of layer clouds can be found using balloon-carried instruments. Our previous research using in situ balloon observations has demonstrated that, on average, the bulk charge polarity and location agrees with theoretical predictions of positive charge at the upper edge and negative charge at the lower edge. Here we present optical and charge measurements of droplets from a variety of stratiform clouds, demonstrating the typical variability which is observed.