Saturation Effects in Narrowband Resonance Lidar Measurements, Part 2: Potassium Lidar Systems and Experimental Results

Abstract

Resonance lidars targeting the resonance line of potassium at 770 nm have been employed over the past 5 decades to yield numerous insights into the dynamics of the middle and upper atmosphere. It has long been recognized that these measurements can be severely affected by nonlinear behavior in the scattering process, that is, saturation effects, particularly when high pulse energies, narrow beam divergences, and narrow laser linewidths are employed. The measurements by the potassium resonance lidars developed at the Leibniz Institute of Atmospheric Physics are in this respect unique—these are the only systems for which saturation effects have been detected. However, the observed degree of saturation is inconsistent with theoretical estimations thus far. A new method of calculating the degree of saturation, previously applied only to the line of sodium, is described in a companion paper (Geach & Kaifler, 2026, https://doi.org/10.1029/2026JA035269 ); here, we apply the method to the resonance line of potassium. We show that the observed degree of saturation, approximately 70%, is consistent with the model; we show that a spectral signature of saturation effects, predicted by the model, is consistent with the observations; we present the saturation‐induced biases on temperature and wind measurements; and we discuss the implications of saturation on ideal instrument design.