Improvement of visibility in fogs.

As a result of long-term experimental and theoretical researches executed in Central Aerologic Observatory of Roshydromet, the effective Russian technology of dispersion of the cooled fogs and means necessary for its realizationwas were developed with the purpose of an improvement of visibility at the airports and on motorways. This technology has passed approbation at the airports of Moscow, Kishinev, Mozdok, Alma-Ata and Mineral Waters, and since 1995 is successfully applied in experimental works on improvement of visibility on motorways and at the airports of northern Italy. The application of the technology of dispersion of the cooled fogs at the airports allows to increase visibility in a fog up to meanings allowing to make landing and take-off of aircrafts. The increase of visibility in a fog on motorways increases essentially a safety of traffic.

Increase of visibility in cooled fog on the Venice — Trieste motorway

Fig.1(a). Before cooled fog seeding.

Fig.1(b).One hour after beginning fog dispersion.

The Russian technology of cooled fog dispersion is based on influence on phase instability of cooled fog connected with a long-term existence supercooled liquid droplet in it. At introduction of artificial ice embryonic particles in the cooled fog it begins the process of conversion of water pair from supercooled droplets to ice particles because of saturating an aqueous tension over ice is less than above water and the supercooled fog droplets are evaporated and ice particles grow up to the large sizes and drop out of a fog.
The stationary and mobile generators of fine-dispersed ice particles utilizing a liquid nitrogen (N₂) are applied for artificial improvement of visibility in the cooled fogs. Introduction of a liquid nitrogen (temperature of boiling is -178^oС) in cooled fog causes sharp local decrease of temperatures resulting in freezing of fog droplets in this zone, a transition of water pair from the supercooled droplets to the ice crystals, evaporation of droplets and increase of visibility in a cooled fog.
The stationary generators are used for improvement of visibility on landing way in airports and in outcomes of highways. The generators are placed around of protected territories based on local meteorological conditions (rose of winds, local relief etc.). Automated and semiautomatic control systems including a data-measuring complex, intended for the control and registration of parameters of an atmosphere necessary for acceptance of the decision on seeding, network of stationary generators and system of remote control by generators are developed.

Fig.2(a). The stationary liquid nitrogen generator of fine-dispersed particles of ice.

Fig.2(b). Process of seeding of cooled fog using the stationary generator.

For operative improvement of visibility on motorways the mobile liquid nitrogen generators of fine-dispersed ice particles are used Fig. 3

Fig.3(a). The mobile liquid nitrogen generator of fine-dispersed ice particles.

Fig.3(b). Process of seeding of cooled fog using the mobile generator.