What is scintillation?
You are surely familiar with the shimmering of the air over a hot road in summer or the twinkling of city lights or stars that we observe at night from places outside the light smog. These are all phenomena called scintillation, which is caused by the passage of light (an image) through masses of air of different temperatures and therefore different densities. They are observable with the naked eye, but this scintillation takes place everywhere between the observer and the object, it is just not always visible to the eye.
What do we use scintillation for?
In hydroclimatology, we observe this oscillation over the surface whose energy balance we want to record (for example, over a forest stand, meadow, or field). The shimmering determines the rate of heat transfer from the surface to the atmosphere. This information, together with measurements of soil heat flux and solar radiation, allows us to calculate the individual parts of the energy balance and use them to determine the energy available for actual evapotranspiration (evaporation) over the surface. This is essential information for hydrological modelling, for example.
What is the scintillometer used for? This is where a scintillometer comes in handy. It measures air turbulence (the turbulent movement of the refractive index of light), the intensity of which is influenced by temperature, humidity, and air pressure. The instrument consists of two parts - a transmitter and a receiver. These are positioned above the surface being monitored so that the transmitter can 'see' the receiver and vice versa. The receiver then detects and evaluates variations in the intensity of the transmitted signal, which is called scintillation. The system is complemented by a weather station that measures the remaining components of the energy balance - soil heat flux, solar radiation, pressure, temperature, and humidity.
