isentropic analysis

{{short description|Meteorological technique for determining air motion above the planetary boundary layer}}

File:Insentropic analysis and satellite picture of blizzard on 199-10-24 300Kelvin.gif isotrope and the weather satellite image of clouds during a blizzard in Colorado]]

In meteorology, isentropic analysis is a technique used to find the vertical and horizontal motion of airmasses during an adiabatic (i.e. non-heat-exchanging) process above the planetary boundary layer. The change of state of air parcels following isentropic surfaces does not involve exchange of heat with the environment.{{cite web | url= http://www.eumetcal.org/euromet/glossary/isentrop.htm | title= Isentropic analysis | author= World Weather Organization | publisher= Eumetcal | work= Meteorological glossary | accessdate= July 22, 2014 | url-status= dead | archiveurl= https://web.archive.org/web/20140811010144/http://www.eumetcal.org/euromet/glossary/isentrop.htm | archivedate= August 11, 2014 }} Such an analysis can also evaluate the airmass stability in the vertical dimension and whether an air parcel crossing such a surface will result in convective or stratiform clouds. It is based on the study of weather maps or vertical cross-sections of the potential temperature values in the troposphere.{{cite web | url= http://www.eumetcal.org/euromet/glossary/isentro4.htm | archive-url= https://web.archive.org/web/20080204085403/http://www.eumetcal.org/euromet/glossary/isentro4.htm | url-status= dead | archive-date= February 4, 2008 | title= Isentropic surface | author= World Weather Organization | publisher= Eumetcal | work= Meteorological glossary | accessdate= July 22, 2014 }}{{cite web | url= https://www.btb.termiumplus.gc.ca/tpv2alpha/alpha-fra.html?lang=fra&i=1&srchtxt=isentropic+analysis | title= Analyse isentropique | author= Translation Bureau | publisher = Public Works and Government Services Canada | work= Termium | date= 8 October 2009 | accessdate = July 22, 2014 }}

On a synoptic scale, isentropic analysis is associated with weather fronts: warm fronts are found where the wind crosses lines of a chosen potential temperature from lower heights to higher ones, while cold fronts are where the wind crosses descending heights. Synoptic clouds and precipitations can thus be better found with these areas of advection than with conventional isobaric maps. From a mesoscale point of view, an air parcel moving vertically will cross isolines of potential temperature and it will be unstable if the value of those lines decrease with altitude, or stable if they increase.{{Cite web|url=http://www.comet.ucar.edu/class/faculty/Jun05_2000/docs/schneider/htm/index.html|title=Isentropic Analysis|work=COMET|accessdate=July 22, 2014|url-status=dead|archiveurl=https://web.archive.org/web/20120207042729/http://www.comet.ucar.edu/class/faculty/Jun05_2000/docs/schneider/htm/index.html|archivedate=February 7, 2012}}