Dry line
The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. (March 2018) |
A dry line (also called a dew point line, or Marfa front, after Marfa, Texas)[1] is a line across a continent that separates moist air and dry air. One of the most prominent examples of such a separation occurs in central North America, especially Texas, Oklahoma, and Kansas, where the moist air from the Gulf of Mexico meets dry air from the desert south-western states. The dry line is an important factor in severe weather frequency in the Great Plains of North America. It typically lies north-south across the High Plains states in the warm sector of an extratropical cyclone and stretches into the Canadian Prairies during the spring and early summer.[citation needed] The dry line is also important for severe convective storms in other regions of the world, such as northern India and Southern Africa.[2] In general, thunderstorms and other forms of severe weather occur on the moist side of the dryline.
Characteristics
Near the surface, warm dry air is denser than warm moist air of lesser or similar temperature, and thus the warm dry air wedges under the moist air like a cold front.[3][4] At higher altitudes, the warm moist air is less dense than the cooler, drier air and the boundary slope reverses. In the vicinity of the reversal aloft, severe weather is possible, especially when a triple point is formed with a
Daily progression in North America
The dry line typically advances eastward during the afternoon and retreats westward at night, mainly due to the increased mixing down to the surface of moist air aloft, rather than the air mass' surface density contrast. The movement of the dry line during daylight hours is quickest in areas where low level moisture is most shallow, as dryline movement slows in areas with deeper low-level moisture. Weaker winds aloft also slow its progression.
Associated weather
In the dry sector west of the dry line, clear skies are the rule due to the dryness of the
See also
References
- ^ Scott Girhard (2007-05-04). "Lecture 3 - Thunderstorms". San Antonio College. Archived from the original on 2007-09-27. Retrieved 2008-03-15.
- ^ >Howard, E., and R. Washington, 2019: Drylines in Southern Africa: Rediscovering the Congo Air Boundary. J. Climate, 32, 8223–8242, https://doi.org/10.1175/JCLI-D-19-0437.1.
- ^ Carlson and Ludlam, "Conditions for the occurrence of severe local storms", orig. Tellus, Vol.20, No.2, pp.203-226 (May 1968), republished online at Wiley Online Library, March 18, 2010
- University of California Los Angeles. Archived from the originalon 2008-01-20. Retrieved 2006-12-05.
- ^ Glossary of Meteorology (June 2000). "Dryline". American Meteorological Society. Archived from the original on 2011-06-06. Retrieved 2010-04-25.
- ^ Daniel Dix (June 2000). "Dryline Thunderstorms". The Weather Channel. Archived from the original on 2007-07-29. Retrieved 2010-04-25.
- ^ ISBN 978-0-04-551116-7.
- doi:10.1002/qj.49709841704. Archived from the originalon 2013-01-05. Retrieved 2010-04-25.
- ^ ISSN 0026-1165.
- ^ Todd Lindley (1997-09-01). "Effects of Texas Panhandle Topography on Dryline Movement". National Weather Service Southern Region Headquarters. Retrieved 2010-04-25.
- ^ National Severe Storms Laboratory (2006-10-11). "Tornado Climatology". National Oceanic and Atmospheric Administration. Archived from the original on 2012-03-20. Retrieved 2010-04-25.
- ISBN 978-0-07-012031-0. Retrieved 2010-04-25.