Editing Sea surface temperature (section)

==Measurement==
[[File:MODIS and AIRS SST comp fig2.i.jpg|right|thumb|Temperature profile of the surface layer of the ocean (a) at night and (b) during the day]]
There are a variety of techniques for measuring this parameter that can potentially yield different results because different things are actually being measured. Away from the immediate sea surface, general temperature measurements are accompanied by a reference to the specific depth of measurement. This is because of significant differences encountered between measurements made at different depths, especially during the daytime when low wind speed and high sunshine conditions may lead to the formation of a warm layer at the ocean's surface and strong vertical temperature gradients (a diurnal [[thermocline]]).<ref name="space"/> Sea surface temperature measurements are confined to the top portion of the ocean, known as the near-surface layer.<ref>{{cite book|url=https://books.google.com/books?id=tZary8a4HMwC|page=xi|author1=Alexander Soloviev |author2=Roger Lukas |title=The near-surface layer of the ocean: structure, dynamics and applications|journal=The Near-Surface Layer of the Ocean: Structure|isbn=978-1-4020-4052-8|year=2006|publisher=シュプリンガー・ジャパン株式会社|bibcode=2006nslo.book.....S}}</ref>

===Thermometers===
The sea surface temperature was one of the first oceanographic variables to be measured. [[Benjamin Franklin]] suspended a [[mercury thermometer]] from a ship while travelling between the United States and Europe in his survey of the [[Gulf Stream]] in the late eighteenth century. SST was later measured by dipping a [[thermometer]] into a bucket of water that was manually drawn from the sea surface. The first automated technique for determining SST was accomplished by measuring the temperature of water in the intake port of large ships, which was underway by 1963. These observations have a warm bias of around {{convert|0.6|C-change|F-change|sigfig=1}} due to the heat of the engine room.<ref>{{cite book|url=https://books.google.com/books?id=A6ew-bJDIDIC&pg=PA24|pages=24–25|title=Data analysis methods in physical oceanography|author1=William J. Emery |author2=Richard E. Thomson |year=2001|isbn=978-0-444-50757-0|publisher=Elsevier|edition=2nd Revised}}</ref>  

Fixed [[weather buoy]]s measure the water temperature at a depth of {{convert|3|m|ft}}. Measurements of SST have had inconsistencies over the last 130 years due to the way they were taken. In the nineteenth century, measurements were taken in a bucket off a ship. However, there was a slight variation in temperature because of the differences in buckets. Samples were collected in either a wood or an uninsulated canvas bucket, but the canvas bucket cooled quicker than the wood bucket. The sudden change in temperature between 1940 and 1941 was the result of an undocumented change in procedure. The samples were taken near the engine intake because it was too dangerous to use lights to take measurements over the side of the ship at night.<ref>{{cite book|last=Burroughs|first=William James|title=Climate change : a multidisciplinary approach|url=https://archive.org/details/climatechangemul0000burr_p9v1|url-access=registration|year=2007|publisher=Cambridge Univiversity Press|location=Cambridge [u.a.]|isbn=9780521690331|edition=2.}}</ref> 

Many different drifting buoys exist around the world that vary in design, and the location of reliable temperature sensors varies. These measurements are beamed to satellites for automated and immediate data distribution.<ref name="buoy">{{cite book|url=https://books.google.com/books?id=hH2NkL_318wC&pg=PA263|pages=237–238|title=Oceanography from Space: Revisited|author=Vittorio Barale|year=2010|isbn=978-90-481-8680-8|publisher=Springer}}</ref> A large network of coastal buoys in U.S. waters is maintained by the [[National Data Buoy Center]] (NDBC).<ref>{{cite book|page=[https://archive.org/details/meteorologicalbu0000unse/page/11 11]|title=The meteorological buoy and coastal marine automated network for the United States|author=Lance F. Bosart, William A. Sprigg, National Research Council|publisher=National Academies Press|year=1998|isbn=978-0-309-06088-2|url=https://archive.org/details/meteorologicalbu0000unse/page/11}}</ref> Between 1985 and 1994, an extensive array of moored and drifting buoys was deployed across the equatorial Pacific Ocean designed to help monitor and predict the [[El Niño-Southern Oscillation#Effects of ENSO's warm phase (El Niño)|El Niño]] phenomenon.<ref>{{cite book|url=https://books.google.com/books?id=DO5K1NK_ZewC&pg=PA62|title=Global energy and water cycles|author1=K. A. Browning |author2=Robert J. Gurney |page=62|year=1999|publisher=[[Cambridge University Press]]|isbn=978-0-521-56057-3}}</ref>

===Weather satellites===
{{See also|Weather satellite|Satellite temperature measurement}}
[[File:MODIS sst.png|thumb|2003–2011 SST based on [[Moderate-Resolution Imaging Spectroradiometer|MODIS]] Aqua data]]
Weather satellites have been available to determine sea surface temperature information since 1967, with the first global composites created during 1970.<ref>{{cite journal|url=http://docs.lib.noaa.gov/rescue/mwr/100/mwr-100-01-0010.pdf|title=Global Sea-Surface Temperature Distribution Determined From an Environmental Satellite|author=P. Krishna Rao, W. L. Smith, and R. Koffler|pages=10–14|journal=[[Monthly Weather Review]]|volume=100|date=January 1972|access-date=2011-01-09|issue=1|doi=10.1175/1520-0493(1972)100<0010:GSTDDF>2.3.CO;2|bibcode = 1972MWRv..100...10K}}</ref> Since 1982,<ref>{{cite book|url=https://books.google.com/books?id=qzYrAAAAYAAJ&pg=PA2|page=2|author=National Research Council (U.S.). NII 2000 Steering Committee|title=The unpredictable certainty: information infrastructure through 2000; white papers|publisher=National Academies|year=1997|isbn=9780309060363}}</ref> [[satellite]]s have been increasingly utilized to measure SST and have allowed its [[Spatial variability|spatial]] and [[time|temporal]] variation to be viewed more fully. [[Satellite temperature measurement|Satellite measurements of SST]] are in reasonable agreement with [[in situ]] temperature measurements.<ref>{{cite journal|journal=[[Journal of Geophysical Research]]|date=2001-02-15|volume=106|author1=W. J. Emery|author2=D. J. Baldwin|author3=Peter Schlüssel|author4=R. W. Reynolds|name-list-style=amp|title=Accuracy of in situ sea surface temperatures used to calibrate infrared satellite measurements|page=2387|issue=C2|bibcode=2001JGR...106.2387E|doi=10.1029/2000JC000246|doi-access=free}}</ref>  The satellite measurement is made by sensing the ocean [[radiation]] in two or more wavelengths within the [[infrared]] part of the [[electromagnetic spectrum]] or other parts of the spectrum which can then be empirically related to SST.<ref name="John">{{cite web|url=http://www2.hawaii.edu/~jmaurer/sst/|title=Infrared and microwave remote sensing of sea surface temperature (SST)|author=John Maurer|date=October 2002|publisher=[[University of Hawai{{okina}}i]]|access-date=2011-01-09}}</ref> These wavelengths are chosen because they are:

# within the peak of the [[blackbody radiation]] expected from the Earth,<ref>{{cite journal|url=http://www.wamis.org/agm/pubs/agm8/Paper-4.pdf|page=73|journal=Satellite Remote Sensing and GIS Applications in Agricultural Meteorology|title=Meteorological Satellites|author=C. M. Kishtawal|date=2005-08-06|access-date=2011-01-27|archive-date=2020-02-15|archive-url=https://web.archive.org/web/20200215044026/http://www.wamis.org/agm/pubs/agm8/Paper-4.pdf|url-status=dead}}</ref> and
# able to transmit adequately well through the [[Earth's atmosphere|atmosphere]]<ref>{{cite journal|journal=New Scientist|date=1971-09-16|title=Mapping the Atmosphere From Space|author= Robert Harwood|page=623|volume=51|issue=769}}</ref>

The satellite-measured SST provides both a [[synoptic scale|synoptic view]] of the ocean and a high frequency of repeat views,<ref>{{cite book|page=510|url=https://books.google.com/books?id=Y0iX2z48qkUC&pg=PA509|author1=David E. Alexander |author2=Rhodes Whitmore Fairbridge |title=Encyclopedia of environmental science|year=1999|publisher=Springer|isbn=978-0-412-74050-3}}</ref> allowing the examination of basin-wide upper [[ocean]] dynamics not possible with ships or buoys. <span class="plainlinks">[http://www.nasa.gov/ NASA's]</span> (National Aeronautic and Space Administration) <span class="plainlinks">[http://modis.gsfc.nasa.gov/ Moderate Resolution Imaging Spectroradiometer (MODIS)]</span> SST satellites have been providing global SST data since 2000, available with a one-day lag. NOAA's <span class="plainlinks">[http://www.goes.noaa.gov/ GOES (Geostationary Orbiting Earth Satellites)] {{Webarchive|url=https://web.archive.org/web/20200817111624/http://www.goes.noaa.gov/ |date=2020-08-17 }}</span> satellites are [[geostationary orbit|geo-stationary]] above the Western Hemisphere which enables them to deliver SST data on an hourly basis with only a few hours of lag time.

There are several difficulties with satellite-based absolute SST measurements. First, in infrared remote sensing methodology the radiation emanates from the [[Sea surface microlayer|top "skin" of the ocean]], approximately the top 0.01 [[millimetre|mm]] or less, which may not represent the [[bulk temperature]] of the upper meter of ocean due primarily to effects of solar surface heating during the daytime, reflected radiation, as well as sensible heat loss and surface evaporation. All these factors make it somewhat difficult to compare satellite data to measurements from buoys or shipboard methods, complicating ground truth <!-- clarify -->efforts.<ref>{{cite book|url=https://books.google.com/books?id=jk1fIo51uwMC&pg=PA278|page=279|author=Ian Stuart Robinson|title=Measuring the oceans from space: the principles and methods of satellite oceanography|publisher=Springer|year=2004|isbn=978-3-540-42647-9}}</ref>  Secondly, the satellite cannot look through clouds, creating a cool bias in satellite-derived SSTs within cloudy areas.<ref name="space"/>  However, passive microwave techniques can accurately measure SST and penetrate cloud cover.<ref name="John"/>  Within atmospheric sounder channels on [[weather satellite]]s, which peak just above the ocean's surface, knowledge of the sea surface temperature is important to their calibration.<ref name="space"/>