Studies of the atmosphere remains stationary LIDAR most public sector use of technology. In the world deployed several permanent research networks (inter-state and university), observing atmospheric phenomena.
Measuring the speed and direction of air flow. The theoretical justification for the use of ground Doppler lidar for these measurements was given back in 1980. The first practical development of the use of fixed optical system with a beam directed vertically towards the zenith, in the 1990's were proposed technologies, allowing Doppler lidar to scan a wide viewing angle. In 2001, Alcatel proposed placement of lidar on board the satellites, so that the "constellation" of satellites in orbit can track the movement of air masses in the whole continent, and the potential - on the Earth as a whole. Lidars actively used for monitoring air pollution. A special class of differential lidar (differential absorption lidar, DIAL), while emitting light with different wavelengths can effectively determine the concentration of individual gases, the optical parameters of which depend on the wavelength.
Measuring the temperature of the atmosphere. Developed and put into practice a few basic methods to measure temperature profiles.
The first method uses a resonant scattering on the atoms of alkali metals, in particular, sodium, potassium, and iron. Clouds of metal atoms are located at a height of 85 - 100 km. Temperature is measured by the Doppler broadening of resonance lines with adjustable sensing narrowband laser (used liquid lasers with the active substance in the form of a solution of organic dye). The first measurements were carried out with the help of artificial sodium cloud, threw missiles into the atmosphere. Despite the fact that the method is limited to a range of heights, which are attended by the metal atoms, the scattered signal is relatively large, and this makes it possible to measure the temperature with an accuracy of 1.5 ˚ C.
The second method - the method of Rayleigh scattering (Rayleigh lidar), is based on the non-resonance scattering of light by molecules of air. It was first used in 1953 in experiments with searchlights probing the atmosphere. The method is as follows. If there is no aerosol scattering, the power backscattered signal is directly proportional to the density of air, from which we can Calculate the temperature. Dilution of air with altitude can use the method of Rayleigh scattering at altitudes of less than 90 km. The lower limit of height measurements (about 20-30 km) due to the presence in the boundary layer a large number of aerosol, which greatly increases the scattering, but virtually no effect on the density of air.
The third method is based on the rotational Raman (Raman) scattering by air molecules (Raman lidar). When the temperature increases, the intensity of the transitions with large quantum numbers increases, while the intensity of the lines of the rotational Raman spectrum corresponding to a small quantum numbers, decreases. Transitions with large quantum numbers correspond to the lines of the Raman spectrum, located farther from the center frequency. The temperature is determined using measurements in two spectral regions with different temperature dependence. Maximum height sensing is about 30 km, the measurement error of less than 1 ˚ K to a height of 10 km. Since the receiver line of elastic scattering is suppressed, the measurements can be performed in the presence of significant concentrations of aerosols.
Temperature measurement can be done just by using DIAL lidar, but this method did not gain wide acceptance.
In addition to the scientific goals and meteorological observations, are actively being tested integrated systems for monitoring air flow in areas of airports. Among the proposals of recent years - the automatic control system turbine using lidar to determine the strength and direction of the wind.
Early warnings of forest fires. Lidar, located on a hill (the hill or on a mast) and scanning the horizon, able to distinguish anomalies in the air, generated by the fire. In contrast, passive infrared systems, which recognize only the thermal anomaly, the lidar detects smoke from the anomalies, generated by combustion particles, changing the chemical composition and transparency of the air, etc. The technology to detect smoke in a radius of 20 km was first declared in 1990, active search for optimum system configurations are maintained to this day.