Simultaneous Observation of Sporadic Potassium and Sodium Layers Over São José dos Campos, Brazil (23.1°S, 45.9°W)

Abstract Sporadic potassium (K s ) and sodium (Na s ) layers were investigated using more than 1,500 h of simultaneous Na/K LIDAR data at São José dos Campos, Brazil (23.1°S, 45.9°W). These events were observed on more than 88% of the analyzed nights. Although Na and K are both alkali metals, their sporadic layers show different behaviors. The Na s layers were in general 0.7 km wider and occurred ∼2 km higher than K s layers. Moreover, the Na s layers progression is faster than that of K s layers not only in the process of reaching their maximum amplitude but also in terms of dissipation. Our study showed that most N s events (80% of K s layers and 90% of Na s layers) have a strength factor of upto 5. Moreover, on average, K s presented a strength factor ∼1.3 times stronger than that of Na s . The relative frequency of occurrence for both K s and Na s layers exhibits an almost semiannual variation, with maxima in January/October and February/September, respectively. On the other hand, no similar variation was observed in the peak density or in the peak height. The peak density shows an annual variation, with a maximum occurring during winter for K s events and a semiannual variation with a maxima occurring at the equinoxes for Na s . Different seasonal behaviors were also seen in the peak height of the identified layers, with K s presenting a semiannual variation with maxima around January/October, while an annual variation occurred in Na s with lower layers occurring around winter.