Astronomy Picture of the Day

   [1]Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                               2025 August 17
    [2]Trees and mountains line the bottom of a landscape image with blue
      sky visible above. The sky is otherwise dominated by a large and
   unusual cloud that is brown and gold and has many waves and structures.
          Please see the explanation for more detailed information.

                      Asperitas Clouds Over New Zealand
                 Image Credit & Copyright: [3]Witta Priester

   Explanation: What kind of clouds are these? Although their cause is
   presently unknown, such unusual atmospheric structures, as menacing as
   they might seem, do not appear to be harbingers of [4]meteorological
   doom. Formally recognized as a distinct [5]cloud type only last year,
   [6]asperitas clouds can be stunning in appearance, unusual in
   occurrence, and are relatively unstudied. Whereas most low cloud decks
   are [7]flat bottomed, [8]asperitas clouds appear to have significant
   [9]vertical structure underneath. Speculation therefore holds that
   [10]asperitas clouds might be related to [11]lenticular clouds that
   form near mountains, or [12]mammatus clouds associated with
   thunderstorms, or perhaps a [13]foehn -- a type of dry downward wind
   that flows off mountains. Clouds from [14]such a wind called the
   [15]Canterbury arch stream toward the east coast of New Zealand's
   [16]South Island. The [17]featured image, taken above [18]Hanmer
   Springs in [19]Canterbury, [20]New Zealand in 2005, shows great detail
   partly because sunlight illuminates the undulating [21]clouds from the
   side.

                     Tomorrow's picture: working spiral
     __________________________________________________________________

      [22]< | [23]Archive | [24]Submissions | [25]Index | [26]Search |
   [27]Calendar | [28]RSS | [29]Education | [30]About APOD | [31]Discuss |
                                    [32]>
     __________________________________________________________________

    Authors & editors: [33]Robert Nemiroff ([34]MTU) & [35]Jerry Bonnell
                                 ([36]UMCP)
          NASA Official: Amber Straughn [37]Specific rights apply.
            [38]NASA Web Privacy, [39]Accessibility, [40]Notices;
                A service of: [41]ASD at [42]NASA / [43]GSFC,
                         [44]NASA Science Activation
                           & [45]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2508/asperatus_priester_1024.jpg
   3. http://www.flickr.com/people/wittap/
   4. https://apod.nasa.gov/apod/ap170226.html
   5. https://scied.ucar.edu/webweather/clouds/cloud-types
   6. https://en.wikipedia.org/wiki/Asperitas_(cloud)
   7. https://physics.stackexchange.com/questions/277662/why-do-clouds-generally-look-flat-at-the-bottom
   8. http://cloudappreciationsociety.org/asperatus-update/comment-page-2/
   9. https://www.boredpanda.com/blog/wp-content/uploads/2014/03/funny-cats-dogs-stuck-furniture-31.jpg
  10. http://www.usatoday.com/story/weather/2015/06/20/asperatus-cloud-atlas/28994525/
  11. https://apod.nasa.gov/apod/ap090121.html
  12. https://apod.nasa.gov/apod/ap230212.html
  13. http://en.wikipedia.org/wiki/Foehn_wind
  14. http://en.wikipedia.org/wiki/Nor'west_arch
  15. http://en.wikipedia.org/wiki/Canterbury_arch
  16. http://en.wikipedia.org/wiki/South_Island,_New_Zealand
  17. http://www.flickr.com/photos/wittap/4406137868/in/set-72157623581503907
  18. https://www.youtube.com/watch?v=gn7ck-N53k0
  19. http://en.wikipedia.org/wiki/Canterbury_Region
  20. http://en.wikipedia.org/wiki/New_Zealand
  21. https://climatekids.nasa.gov/cloud-formation/
  22. https://apod.nasa.gov/apod/ap250816.html
  23. https://apod.nasa.gov/apod/archivepix.html
  24. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  25. https://apod.nasa.gov/apod/lib/aptree.html
  26. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  27. https://apod.nasa.gov/apod/calendar/allyears.html
  28. https://apod.com/feed.rss
  29. https://apod.nasa.gov/apod/lib/edlinks.html
  30. https://apod.nasa.gov/apod/lib/about_apod.html
  31. https://asterisk.apod.com/discuss_apod.php?date=250817
  32. https://apod.nasa.gov/apod/ap250818.html
  33. http://www.phy.mtu.edu/faculty/Nemiroff.html
  34. http://www.phy.mtu.edu/
  35. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  36. http://www.astro.umd.edu/
  37. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  38. https://www.nasa.gov/about/highlights/HP_Privacy.html
  39. https://www.nasa.gov/general/accessibility/
  40. https://www.nasa.gov/privacy/
  41. https://astrophysics.gsfc.nasa.gov/
  42. https://www.nasa.gov/
  43. https://www.nasa.gov/centers/goddard/
  44. https://science.nasa.gov/learners
  45. http://www.mtu.edu/