Fair weather criteria for atmospheric electricity measurements

• Published in: Journal of atmospheric and solar-terrestrial physics Vol. 179; pp. 239 - 250
• Main Authors: Harrison, R.G., Nicoll, K.A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2018
• ISSN: 1364-6826; 1879-1824
• DOI: 10.1016/j.jastp.2018.07.008

The global atmospheric electric circuit, which links the space environment with terrestrial weather, has mostly been investigated using fair-weather surface atmospheric electricity measurements. Retrieving global circuit information, however, requires the selection of “fair weather” data, to avoid local meteorological disturbances. The research results presented here challenge the applicability of long-standing definitions of electrically fair weather atmospheric conditions. From detailed new measurements and theory, three improved requirements (FW1 to FW3) for fair weather atmospheric electricity conditions are described. These are: (FW1) absence of hydrometeors, aerosol and haze, as apparent through the visual range exceeding 2 km, (FW2) negligible cumuliform cloud and no extensive stratus cloud with cloud base below 1500 m, and (FW3) surface wind speed between 1 m s−1 and 8 m s−1. Automatic and manual measurement approaches to identifying these requirements are given. Through applying these criteria at the many measurements sites now operating, the noise from meteorological variability will be reduced, leading to data more representative of the global electric circuit. •Approaches to selecting atmospheric electricity data are reviewed.•New criteria for identifying fair weather conditions are presented.•Low altitude clouds are shown to obscure globally valid potential gradient measurements.•Visibility is demonstrated to provide a robust and useful parameter at a range of sites.