Study Summary
Continuous monitoring of the atmospheric electric field at diverse locations around the world is essential for understanding the Global Electric Circuit (GEC), the planetary-scale system of electrical currents maintained by thunderstorms and electrified clouds worldwide. Despite the importance of expanding the global observation network, few long-term measurement stations exist in tropical and arid regions of South America. This study presents the first comprehensive analysis of the atmospheric potential gradient (PG) recorded at a station in Ica, Peru, filling an important observational gap.
The measurements were collected continuously from March 2018 to December 2022 using a Boltek EFM-100 electric field mill installed at the CIEASEST research facility of the Universidad Nacional San Luis Gonzaga. Ica is located on the south-central coast of Peru at 406 meters above sea level, in a hyper-arid desert environment surrounded by mountain ranges, sand dunes, and the extensive Pampas desert. The climate is warm and dry, with minimal rainfall and strong wind activity, conditions that make the site particularly interesting for studying the interaction between dust transport, sea breeze circulation, and the atmospheric electric field.
A central finding is the identification of a critical wind speed threshold of 3.5 m/s. Below this threshold, the PG behaves in a way consistent with fair-weather conditions suitable for studying the global circuit. Above it, the electric field shows significant perturbations caused by the lifting and transport of dust and sand particles by the wind. The study distinguishes between two dominant wind regimes at the station: strong northwest winds associated with sea breeze circulation, and strong south-southeast winds linked to Paracas dust storms, the regional phenomenon that periodically reduces visibility and deposits large quantities of sand and dust across the Ica valley.
The research also establishes the characteristic diurnal PG curve (standard curve) for fair-weather conditions at this tropical arid station and examines its monthly, seasonal, and annual variability. Wavelet spectral analysis reveals periodicities at 1 day, approximately 188 days, and 360 days, corresponding to diurnal, semiannual, and annual cycles. An intense period of approximately 45 days observed between January and March 2018 is associated with one of the strongest Madden-Julian Oscillation events recorded globally. These results provide a comprehensive baseline for future studies of atmospheric electricity in arid coastal regions and contribute to the growing global network of PG measurement sites.
How to cite this work:
Romero, R., et al., Variation of the atmospheric potential gradient at a tropical station in South America (Ica, Peru): first results. Journal of Atmospheric and Solar-Terrestrial Physics, 256, 106198 (2024). DOI: 10.1016/j.jastp.2024.106198