Subj : Daily APOD Report
To   : All
From : Alan Ianson
Date : Sun Aug 17 2025 00:21:00

                        Astronomy Picture of the Day

    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
   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: 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 meteorological doom.
   Formally recognized as a distinct cloud type only last year, asperitas
   clouds can be stunning in appearance, unusual in occurrence, and are
   relatively unstudied. Whereas most low cloud decks are flat bottomed,
   asperitas clouds appear to have significant vertical structure
   underneath. Speculation therefore holds that asperitas clouds might be
   related to lenticular clouds that form near mountains, or mammatus
   clouds associated with thunderstorms, or perhaps a foehn -- a type of
   dry downward wind that flows off mountains. Clouds from such a wind
   called the Canterbury arch stream toward the east coast of New
   Zealand's South Island. The featured image, taken above Hanmer Springs
   in Canterbury, New Zealand in 2005, shows great detail partly because
   sunlight illuminates the undulating clouds from the side.

                     Tomorrow's picture: working spiral
     __________________________________________________________________

       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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                      A service of: ASD at NASA / GSFC,
                           NASA Science Activation
                             & Michigan Tech. U.

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