With Best Regards: Closing Your Letter. June 17, 2014 by. When writing professional or informal emails and letters, it is often considered proper etiquette to complete your correspondence with an appropriate closing signature.
What two conditions are needed for clouds to form? Air must be cooled to its dew point and particles must be present in the air When are clouds formed by ice crystals instead of drops of liquid water?
The clouds can also be associated with very high surface winds which may indicate the presence of, or induce, winds and waves in the stratosphere. They form at temperatures of around minus 85ÂºC, colder than average lower stratophere temperatures, and are comprised of ice particles ~10Âµm across. The clouds must be composed of similar sized crystals to produce the characteristic bright iridescent colours by diffraction and interference.