  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.
