On the relationship between the mesospheric sodium layer and the meteoric input function

Abstract

Abstract. This study examines the relationship between the concentration of atmospheric sodium and its Meteoric Input Function (MIF). We use the measurements from the Colorado State University (CSU) Lidar and the Andes Lidar Observatory (ALO) with a new numerical model that includes sodium chemistry in the mesosphere and lower thermosphere (MLT) region. The model is based on the continuity equation to treat all sodium-bearing species and runs at a high temporal resolution. The model simulation employs data assimilation to compare the MIF inferred from the meteor radiant and the MIF derived from the new sodium chemistry model. The simulation captures the seasonal variability of sodium number density compared with lidar observations over CSU site. However, there were discrepancies for the ALO site, which is close to the South Atlantic Anomaly (SAA) region, indicating it is challenging for the model to capture the observed sodium over ALO. The CSU site had significantly more lidar observations (27,930 hours) than the ALO sites (1872 hours). The simulation revealed that the uptake of the sodium species on meteoric smoke particles was a critical factor in determining the sodium concentration in MLT, with the sodium removal rate by uptake found to be approximately three times that of the NaHCO₃ dimerization. Overall, the study's findings provide valuable information on the correlation between MIF and sodium concentration in the MLT region, contributing to a better understanding of the complex dynamics in this region. This knowledge can inform future research and guide the development of more accurate models to enhance our comprehension of the MLT region's behavior.