Low heat
A heat depression is a flat, stationary low pressure area with a small extent that is created by strong solar radiation over the continent . The troposphere is warmed from below via the soil warmed by the sun , which leads to a labilization of the lower layers of air and vertical movements. The creation of a heat dip is favored by small horizontal air movements. Heat lows mainly occur in arid or semi-humid climates , which is due to the scarcely available cooling by evaporation .
A special heat low is the monsoon low , which leads to a shift in the intertropical convergence zone (ITC) and thus influences the weather over a large area and leads to monsoon rains .
Normal heat low
Typically, the dew point and relative humidity are low. This means that the amounts of precipitation caused by low temperatures are low. The stability of the upper layers of air limits the vertical expansion of the depth, and a capping inversion often occurs . That is why only sporadic thunderstorms occur in connection with a heat dip .
When the heat is low, there is hardly any orderly, cyclonic flow. The heat depression usually stays in the area in which it developed, and thus covers significantly shorter distances than other low pressure areas.
Monsoon low
Any consistent heat dip that plays a key role in a monsoon circulation is known as a monsoon low . Mainly, however, the term is used for the warming temperatures of the Asian continent in summer with a core over northern India . In the mean air pressure distribution of summer, this low has the lowest air pressure in the northern hemisphere at 995 hPa . It causes a shift of the intertropical convergence zone to the north.
Examples
Large-scale heat troughs often form over the Iberian Peninsula , especially in summer. Due to the strong temperature difference to the relatively cool Atlantic, a very strong north wind , the " Nortada ", often occurs on the west coast of the Iberian Peninsula in the summer months .
Heat lows also occur frequently in the summer months over the southwestern United States . As with the Nortada, this often leads to northerly winds along the west coast of the USA in summer due to the strong temperature contrast to the rather cool western Pacific .
Heat lows also often occur over the Sahara in the summer months.
In the Alps , the air layer above the mountainous orography is on average warmer than the air above the surrounding plains. Relative to the foothills of the Alps, a heat depression with large-scale rising air masses regularly forms over the Alps. The compensating winds thus generated therefore blow characteristically from the foothills of the Alps to the Alps during the day and contribute to the valley wind system in the Alps.
See also
literature
- The Brockhaus. Weather and climate . Brockhaus, Leipzig / Mannheim 2009, ISBN 978-3-7653-3381-1
Individual evidence
- ↑ a b The Brockhaus. Weather and climate . Page 137, see literature
- ↑ American Meteorological Society: Glossary of Meteorology, Thermal Low ( Memento of the original from May 22, 2008 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . Retrieved April 17, 2009
- ↑ www.am.rlp.de: Monsoon depth . Retrieved April 18, 2009
- ↑ The Brockhaus. Weather and climate . Page 230, see literature
- ↑ a b c DWD weather dictionary. In: DWD. Retrieved October 5, 2018 .
- ^ Mass, CF, and MD Albright: Coastal southerlies and alongshore surges of the west coast of North America: Evidence of mesoscale topographically trapped response to synoptic forcing . In: Mon. Wea. Rev. No. 115 , 1987, pp. 1707-1738 .
