Ever wondered why some mountains and forests appear shrouded in a mystical blue mist?
Blue haze is a natural phenomenon primarily found in forested areas, composed largely of organic aerosols. These aerosols are essentially organic particles larger than molecules but still light enough to remain airborne for extended periods. They mainly consist of hydrocarbons - combinations of hydrogen and carbon.
These organic compounds typically evaporate from vegetation, entering the atmosphere as vapors. When sunlight hits these hydrocarbon vapors, it triggers reactions with other naturally present elements, leading to the formation of larger particles. As these particles increase in size, they begin to scatter light, with blue light scattering most effectively, giving the haze its characteristic color.
Estimates suggest that natural organic haze can be 5 to 500 times more prevalent than anthropogenic (human-made) haze, though in industrial areas, human contributions can dominate.
The scarcity of blue haze at higher latitudes can be attributed to cooler summer temperatures, which reduce the rate at which organic vapors are released from plants. Additionally, the lower angle of the sun at these latitudes minimizes the ultraviolet light exposure, further reducing aerosol formation. In coastal areas, frequent rainfall helps wash away both natural and man-made aerosols, as they are soluble in water.
The enduring presence of blue haze in certain temperate forest regions is reflected in the names of geographical features such as West Virginia's Blue Ridge Mountains, the Great Smoky Mountains of North Carolina and Tennessee, and the Blue Mountains of Oregon and Washington, all named long before the advent of industrial pollutants.
What about the Blue Mountains in Australia?
Eucalyptus oil droplets emitted from the forests combine with dust particles and water vapor, scattering short wavelength rays of light which are predominantly blue in color.
Σχόλια