Lidar Observations of Upper Atmosphere Dynamics

Lidar techniques have revolutionised the study of the upper atmosphere by providing high‐resolution profiles of temperature, wind and constituent layers between roughly 50 km and 300 km altitude. By emitting laser pulses at specific wavelengths and analysing backscattered signals from atoms and molecules, researchers can resolve fine‐scale structures associated with gravity waves, planetary and tidal oscillations, chemical layering and space‐weather phenomena. In particular, Doppler lidar methods measure frequency shifts to infer wind speeds and thermal broadening, while resonance fluorescence techniques enable direct detection of trace species such as sodium, iron and metastable helium. Together, these approaches have illuminated processes in the mesosphere and lower thermosphere (MLT), including nonmigrating diurnal tides, metal atom layering and ion–neutral interactions. Recent advances in laser technology, spectral filtering and retrieval algorithms have extended observation windows into daytime and to higher altitudes, opening a window on global circulation patterns, wave forcing and the coupling between the lower atmosphere and near‐space environment. Such insights underpin predictive models of climate variability and space‐weather impacts on satellite operations and radio communications.

Research from Nature Portfolio

Researchers have demonstrated a pioneering lidar instrument that actively stimulates and measures the thermospheric metastable helium layer. By tuning a laser to the He(23S) resonance at 1083 nm and detecting the induced fluorescence, they obtained vertical profiles of He(23S) density from 200 km up to 500 km, quadrupling the altitude range accessible to profiling lidars. These observations validate model predictions of peak densities near 1 cm⁻³ and reveal variations with solar zenith angle and season. The successful retrieval of neutral wind speeds and temperatures via Doppler shift and line‐broadening analysis holds promise for real‐time monitoring of space‐weather drivers, offering crucial data for the calibration of ionospheric and thermospheric models used to safeguard satellites and ground‐based technologies.

Lidar Observations of Upper Atmosphere Dynamics publication trend

The graph below shows the total number of articles in lidar observations of upper atmosphere dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Lidar: Light detection and ranging technique for probing atmospheric constituents and dynamics by emitting laser pulses and analysing backscattered signals.

Doppler lidar: Lidar modality that measures the frequency shift of backscattered light to infer wind velocities and thermal structure.

Resonance fluorescence: Emission process in which atoms absorb laser light at a resonant frequency and re-emit photons, allowing density profiling of specific species.

Nonmigrating diurnal tides: Atmospheric wave modes with a 24-hour period that remain fixed in longitude and modulate upper-atmosphere temperatures and constituent layers.

Metastable helium (He(23S)): Long-lived excited state of helium in the thermosphere that can be excited by lidar to yield density, wind and temperature profiles.

Mesosphere and lower thermosphere (MLT): Atmospheric region between approximately 50 km and 110 km altitude characterised by complex tidal and wave coupling processes.

References

1. Effects of nonmigrating diurnal tides on the Na layer in the mesosphere and lower thermosphere. Atmospheric Chemistry and Physics (2024).
2. Design of a Data Acquisition, Correction and Retrieval of Na Doppler Lidar for Diurnal Measurement of Temperature and Wind in the Mesosphere and Lower Thermosphere Region. Remote Sensing (2023).
3. Measurements of metastable helium in Earth’s atmosphere by resonance lidar. Nature Communications (2022).