Effect of ice particles on the mesospheric potassium layer at Spitsbergen (78°N)

This paper quantitatively evaluates the influence of ice particles on the K layer by using radar and lidar measurements. The methodology involves determination of the volumetric surface area [Aice] of the ice particles in a noctilucent cloud by combining a microphysical ice particle model with a charging model to produce an empirical proxy for polar mesosphere summer echoes (PMSE) based on the properties of the charged aerosol particles. The altitudinal variation of [Aice] reveals peak values of about 2.2 × 10−8 cm−1 around 85 km. The first-order loss rate of atomic K due to uptake on the ice particles maximizes close to 2.2 × 10−4 s−1 at 85 km. To examine the variability of [Aice] on background parameters, a sensitivity study showed that a ±10% variation in [Aice] can result from either a ±5 K shift in the temperatures relative to a background profile or from a ±30% change in the water vapor concentration. We found that the peak [Aice] remains constant for a change of +4 to –6 K temperature fluctuations over the altitude range of 83–85 km. Finally, a new atmospheric model of potassium predicts profiles of the K layer in early May and July that are in good agreement with the observations, when the seasonally averaged K ablation flux at 79°N is set to 160 atom cm−2 s−1. This study reveals that both the vertical wind and ice particles play a significant role in controlling the K layer distribution at high latitudes.