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Potassium Resonance Lidar
The potassium Doppler-Resonance lidar at Arecibo Observatory was primarily developed for the purpose of measuring the temperature in the mesosphere and lower thermosphere (MLT) region by probing the spectral shape and width of the resonance line of mesospheric potassium atoms. With the so-called three frequency technique, it is possible to derive the atmospheric temperature, wind, and potassium density from these measurements. The transmitter unit includes an alexandrite power laser, a seeding laser that is locked to the Doppler-free spectrum of the potassium D1 spectral line, and acousto-optic modulators to tune the emitted wavelengths to three specific points at the spectral shape of the resonance line. The receiver unit consists of an 800 mm diameter telescope mirror that collects the backscattered light from the atmosphere and focuses it on a fiber cable. On the detection bench, the light is then filtered and converted to electronic signals for data recording and analyzing.
Long-term seasonal studies for the climatology of the nighttime mesopause temperature and potassium density. This ongoing study is expected to reach 30 years of observations as ‘Climatology’ is defined by the World Meteorological Organization (WMO) or at least cover two solar cycles.
A short time series of 33 months of temperature observations has been published here:
A longer time series of the mesospheric potassium layer is published here:
These time series are already giving valuable information; however, it needs to be continued to understand, for example, the influence of the solar cycle on temperature and density.
Tidal and gravity waves are a major driver of the atmosphere. Short-term (during one or several consecutive nights) observations of the temperature (and wind) structure of the mesopause give valuable information on the gravity wave spectrum, wave-breaking, and tidal motions. A general overview of the gravity waves activities is given in this publication . However, the tidal activities and the coupling between the different atmospheric layers is missing. In future efforts, it is planned to combine the Rayleigh lidar and Resonance lidar measurements to gather a temperature profile from around 30 to 105km. With this, the coupling and wave activities in the stratosphere and mesosphere can be investigated. This can also help to understand the forcing from the MLT system into the ionosphere from below. A rare example of simultaneous observation of the neutral and ionized atmosphere can be found here:
The formation of neutral atomic layer enhancements, sometimes called "sporadic" or "sudden" layers, are still debatable. Resonance measurements can retrieve temperature profiles of these layers and look for wind shears or other dynamics that may lead to their formation. Working in combination with the multi-metals lidar and Sodium lidar (see separate tap please insert link), we can also gain inside to the chemical reactions taking place within the layers.
Set up of the Potassium Resonance Lidar