Air-earth current density measurements at Lerwick; implications for seasonality in the global electric circuit

作者：Harrison R G; Nicoll K A^*

来源：Atmospheric Research, 2008, 89(1-2): 181-193.

DOI：10.1016/j.atmosres.2008.01.008

• atmospheric electricity
• solar-terrestrial physics

Atmospheric electricity measurements were made at Lerwick Observatory in the Shetland Isles (60 degrees 09'N, 1 degrees 08'W) during most of the 20th century. The Potential Gradient (PG) was measured from 1926 to 84 and the air-earth conduction current (J(c)) was measured during the final decade of the PG measurements. Daily J(c) values (1978-1984) observed at 15 UT are presented here for the first time, with independently-obtained PG measurements used to select valid data. The 15 UT J(c) (1978-1984) spans 0.5-9.5 pA/m(2), with median 2.5 pA/m(2); the columnar resistance at Lerwick is estimated as 70 P Omega m(2). Smoke measurements confirm the low pollution properties of the site. Analysis of the monthly variation of Lerwick J(c) data shows that winter (DJF) J(c) is significantly greater than the summer (JJA) J(c) by 20%. The Lerwick atmospheric electricity seasonality differs from the global lightning seasonality, but J(c) has a similar seasonal phasing to that observed in Nimbostratus clouds globally, suggesting a role for non-thunderstorm rain clouds in the seasonality of the global circuit.

• 出版日期2008-7