Abstract/Summary

Charge is observed in clouds of all forms, which influences their development and properties. In-cloud charge measurements require a wide dynamic range instrument, extending from charge in aerosols and dusts to that present in thunderstorms. Unexpectedly large charge densities (>200 pCm-3) have recently been detected in layer clouds using balloon-carried linear electrometers. These, however, lead to instrument saturation if sufficient sensitivity for aerosol and droplet charge is maintained. Logarithmic electrometers provide an alternative, but suffer strong non-linear thermal effects. This is a limitation for balloon-carried instruments which encounter temperature changes up to ~100 °C, as full thermal compensation requires complexity inappropriate for disposable devices. Here, a novel hybrid system is described, combining linear and logarithmic electrometers to provide extended dynamic range (±50 pA), employing the negligible (±4%) total temperature drift of the linear device to provide in situ calibration of the logarithmic device. This combination opens up new measurement opportunities for charge in clouds, dusts and aerosols.