In meteorology, visibility is a measure of the distance at which an object or light can be clearly discerned. It is reported within surface weather observations and METAR code either in meters or statute miles, depending upon the country. Visibility affects all forms of traffic: roads, sailing and aviation. Meteorological visibility refers to transparency of air: in dark, meteorological visibility is still the same as in daylight for the same air. ICAO Annex 3 Meteorological Service for International Air Navigation contains the following definitions and note: a) the greatest distance at which a black object of suitable dimensions, situated near the ground, can be seen and recognized when observed against a bright background; b) The greatest distance at which lights of 1,000 candelas can be seen and identified against an unlit background. The two distances have different values in air of a given extinction coefficient, and the latter b) varies with the background illumination. The former a) is represented by the meteorological optical range (MOR). Annex 3 also defines Runway Visual Range (RVR) as: The range over which the pilot of an aircraft on the centre line of a runway can see the runway surface markings or the lights delineating the runway or identifying its centre line. In extremely clean air in Arctic or mountainous areas, the visibility can be up to 70 kilometres (43 mi) to 100 kilometres (62 mi). However, visibility is often reduced somewhat by air pollution and high humidity. Various weather stations report this as haze (dry) or mist (moist). Fog and smoke can reduce visibility to near zero, making driving extremely dangerous. The same can happen in a sandstorm in and near desert areas, or with forest fires. Heavy rain such as from a thunderstorm) not only causes low visibility, but the inability to brake quickly due to hydroplaning. Blizzards and ground blizzards (blowing snow) are also defined in part by low visibility.
Meteorological conditions strongly affect the distribution of ozone. ... With increasing distance from Earth's surface the chemical composition of air becomes strongly dependent on altitude and the atmosphere becomes enriched with lighter gases. ... These particles (also known as aerosol) remain airborne for long periods, lowering visibility. ...
An RPV on long distance flight becomes a drone as soon as it is out of radio contact with the ground station and operation on its preprogrammed automatic pilot, which will also guide it to the ground station. ... UAVs with Meteorological Sensor. ... Before launching these, it releases a meteorological sensor to measure local conditions that might affect the delivery accuracy, and to offset the effects of wind. ...
Stakeholder Analysis &Market Based Clean Air Houston-Galveston Region EXECUTIVE SUMMARY: The purpose of this report is to present a stakeholder analysis regarding current clean air initiatives in the Houston-Galveston eight county region. It is not an exhaustive report on clean air initiative...
These blizzards fill the air with powdery snow that buries the camps and reduces visibility to zero. ... They present formidable obstacles to the movement of tracked and wheeled vehicles due to high wind velocity, zero visibility and very high windchill factor. ...
During the winter months, precipitation and fog reduce visibility to as low as 700 meters. ... The Bosphorus is divided into an up lane and a down lane, and with International Maritime Organization regulations over minimum distances for ships to turn, the passage of a large tanker necessitates the closure of one or other of these lanes while the ship passes. ...
