First results of the potential gradient variation in a tropical station in South America (Ica, Peru)

Measurements of the potential gradient (PG) under fair weather conditions at new locations are crucial for monitoring the global electric circuit. In this study, we analyzed the variations in PG recorded in Ica city, Peru, during the period from March 2018 to December 2022. Our analysis involved a detailed comparison of PG with various meteorological parameters such as rainfall, wind speed and direction, dust storms, dust devils and fog to establish the characteristic PG curve under fair weather conditions (referred to as the standard curve). We identified a significant threshold of 3.5 m/s for strong winds, which helps prevent the influence of sea breeze and dust lifting on PG. Our results showed the impact of 'Paracas' dust storms on PG, which aligns with patterns observed in other arid regions worldwide. Subsequently, we calculated monthly, seasonal, and annual averages of the standard curve which showed a response likely associated with local convective processes on the PG diurnal variation. Furthermore, the seasonal variation of PG reveals higher values during June, July, and August compared to December, January, and February. These differences are attributed to seasonal changes in aerosol concentrations, potentially influenced by biomass-burning activities in Peru. Additionally, we performed a wavelet transform analysis of PG hourly values. We found the periodicities of 1 day, ∼188 days, and 360 days which are related to the diurnal, semiannual and annual periods. During the months between January and March 2018 was found an intense period of ∼45-day likely associated with one of the strongest Madden-Julian Oscillation events. Through this comprehensive investigation, we deepen our understanding of the intricate relationships among meteorological conditions, sea breeze, dust storms, and the PG in arid regions like Ica.