Salar de Uyuni: Difference between revisions

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Salt flats are ideal for calibrating the distance measurement equipment of satellites because they are large, stable surfaces with strong reflection, similar to that of ice sheets. As the largest salt flat on Earth, Salar de Uyuni is especially suitable for this purpose.<ref name="NASA2019" /> In the low-rain period from April to November, due to the absence of industry and its high elevation, the skies above Salar de Uyuni are very clear, and the air is dry (relative humidity is about 30%; rainfall is roughly {{convert|1|mm|disp=or}} per month). It has a stable surface, smoothed by seasonal flooding&nbsp;— water dissolves the salt surface and thus keeps it leveled.<ref>{{cite journal |last1=Borsa |first1=A. A. |last2=Bills |first2=B. G. |last3=Minster |first3=J. B. |year=2008 |title=Modeling the topography of the salar de Uyuni, Bolivia, as an equipotential surface of Earth's gravity field |journal=Journal of Geophysical Research: Solid Earth |volume=113 |issue=B10 |doi=10.1029/2007jb005445|bibcode=2008JGRB..11310408B |s2cid=140609728 |url=https://escholarship.org/content/qt0fr1z3fs/qt0fr1z3fs.pdf?t=lnr314 }}</ref>

As a result, the variation in the surface elevation over the {{convert|10582|sqkm|sp=us|adj=on}} area of Salar de Uyuni is less than {{convert|1|m|sp=us}} normal to the Earth's circumference, and there are few square kilometers on Earth that are as flat. The surface reflectivity ([[albedo]]) for ultraviolet light is relatively high at 0.69 and shows variations of only a few percent during the daytime.<ref name=refl>{{cite journal |journal=Journal of Photochemistry and Photobiology B |volume=87 |issue=1 |year=2007 |pages=1–8 |title=Investigations on the effect of high surface albedo on erythemally effective UV irradiance: Results of a campaign at the Salar de Uyuni, Bolivia |doi=10.1016/j.jphotobiol.2006.12.002 |first1=Joachim |last1=Reuder |url=http://www.lfabolivia.org/wp-content/uploads/2008/12/final-uyuni.pdf |format=free-download pdf |pmid=17227712 |display-authors=1 |last2=Ghezzi |first2=F. |last3=Palenque |first3=E. |last4=Torrez |first4=R. |last5=Andrade |first5=M. |last6=Zaratti |first6=F. |url-status=dead |archive-url=https://web.archive.org/web/20140414175025/http://www.lfabolivia.org/wp-content/uploads/2008/12/final-uyuni.pdf |archive-date=14 April 2014}}</ref> The combination of all these features makes Salar de Uyuni about five times better for satellite calibration than the surface of an ocean.<ref name=nature2>{{Cite news |title=The salt flat with curious curves |first=Eric |last=Hand |date=30 November 2007 |publisher=[[Nature (journal)|Nature]] |url=http://www.nature.com/news/2007/071130/full/news.2007.315.html}}</ref><ref name=geo>{{cite journal |title=Assessment of ICESat performance at the salar de Uyuni, Bolivia |first=H. A. |last=Fricker |journal=[[Geophysical Research Letters]] |volume=32 |page=L21S06 |doi=10.1029/2005GL023423 |year=2005 |issue=21 |bibcode=2005GeoRL..3221S06F |doi-access=free}}</ref><ref name=gpsdaily>{{Cite news |title=The Hills And Valleys Of Earth's Largest Salt Flat |date=29 November 2007 |publisher=GPS Daily |url=http://www.gpsdaily.com/reports/The_Hills_And_Valleys_Of_Earth_Largest_Salt_Flat_999.html}}</ref> Using Salar de Uyuni as the target, ICESat has already achieved the short-term elevation measurement accuracy of below {{convert|2|cm|sp=us}}.<ref>{{cite book

|url=https://books.google.com/books?id=CeLCxydgA8UC&pg=PA22 |page=22 |title=Satellite-based Estimates of Sea Ice Volume Flux: Applications to the Fram Strait Region |first=Gunnar |last=Spreen |publisher=GRIN Verlag |year=2008 |isbn=978-3-640-13064-1}}</ref>