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By accident1 I ended up on the Bytes Daily page Photographs 2013, part 1. I saw an interesting image who's caption reads:

A white shelf cloud caps brownish dirt from a dust storm, or haboob, as it travels across the Indian Ocean near Onslow on the Western Australia coast in this handout image distributed by fishwrecked.com and taken January 9, 2013.

Haboob is described in Wikipedia as follows:

A haboob (Arabic: هَبوب‎, romanized: habūb, lit. 'blasting/drifting') is a type of intense dust storm carried on an atmospheric gravity current, also known as a weather front. Haboobs occur regularly in dry land area regions throughout the world.

Question(s):

  1. Is it rare or unusual for haboobs to travel across the Indian Ocean or other oceans?
  2. Is it rarer or more unusual still for shelf clouds to appear over them?
  3. What conditions are necessary to bring all of this about?

Video links from the Wikipedia article:


1I was doing a reverse image search looking for a larger size of the photo of Earth, Venus and Mars amidst the rings of Saturn when Cassini was in Saturn's shadow, and ended up on this page.


Bytes Daily, 2013: A white shelf cloud caps brownish dirt from a dust storm, or haboob, as it travels across the Indian Ocean near Onslow on the Western Australia coast in this handout image distributed by fishwrecked.com and taken January 9, 2013.

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Dust storms or haboobs traveling over seas and oceans is a common phenomenon, and will occur in any desert (having loose soil and sand) with a coastline. Such deserts include the Sahara, the Arabian desert, parts of the deserts of Australia, etc.

Haboobs are caused by collapsing thunderstorms, when the downdraft of cooler air crashes on the ground and blow away the loose and dry topsoil. The conditions required for the formation of haboobs is those required for the formation of thunderstorms in a desert, i.e., solar insolation heating up surface air and creates an updraft of hot air, which cools down in the higher altitudes and creates a downdraft over time, slamming a column of cooler air on the dry desert surface. This downdraft then carries away the blown dust in directions determined by the air pressure difference. In coastal deserts, the blown dust may often be carried over to the sea or ocean.

In fact, dust storms, or more broadly dust clouds, crossing oceans constitutes one of the most critical processes shaping up the current environment of the earth. This particular process is the Saharan air layer, which carries tens of millions of tons of sand and minerals from the Sahara over the Atlantic ocean all the way to the Amazons in South America. The nutrients play a key role in fertilizing the Amazon rain forest. The particles in the dust cloud cools the Atlantic ocean, and hinders the formation and intensification of cyclones in the Atlantic. This process often creates gigantic dust storms or dust cloud spread over thousands of kilometers across, clearly observable and studied using satellite imagery.

Some of the news related to recent such Saharan dust storms crossing the Atlantic, with associated imagery:

However, as can be observed from the images of the Saharan dust storms, formation of shelf clouds over the dust storms are rare for them. This is because the formation of such clouds require cooler temperature and sufficient moisture, which would not be available in the usual Saharan dust storms over the Atlantic. From the Wikipedia page:

They most frequently form along the leading edge or gust fronts of thunderstorms; some of the most dramatic arcus formations mark the gust fronts of derecho-producing convective systems. Roll clouds may also arise in the absence of thunderstorms, forming along the shallow cold air currents of some sea breeze boundaries and cold fronts.

The formation of cold fronts is often associated with Australian dust storms (1, 2). And such storms occurring in especially the north-western coastal deserts of Australia will have adequate moisture from the Indian Ocean and the cooler air required. Due to this, such spectacular but rare phenomenon is likely to occur more in the Australian deserts compared to the Saharan or the Arabian deserts, which are often too dry for the formation of such clouds.

So the conditions required for the occurrence of this phenomenon are:

  • a coastal hot desert with loose surface soil,
  • temperature not hot enough so that the dust storm does not lift over cooler marine air and becomes a dust cloud, as happens for the Saharan air layer, where even the temperature of the downdraft is so high that the resulting dust storm lifts over the cooler Atlantic marine air and becomes a dust cloud.
  • just enough moisture in the environment for the formation of shelf clouds, but not enough to cause rainfall in the thunderstorm, thereby dissipating the dust storm and the clouds over them.
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    $\begingroup$ @uhoh thank you for your kind words, and thank you for informing me of the other question :) I shall try and see if I can answer that question. $\endgroup$
    – joy
    Feb 17, 2022 at 5:01
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    $\begingroup$ Wrote an answer to that question, @uhoh . Could you please see if that resolves the query? $\endgroup$
    – joy
    Feb 17, 2022 at 12:26
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    $\begingroup$ Hi @uhoh, I was wondering what are the ways this answer falls short to being the acceptable answer to this question. If you please let me know that, I shall try to address them. Please also let me know the same about my other answer you awarded bounty. $\endgroup$
    – joy
    Feb 17, 2022 at 17:10
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    $\begingroup$ @uhoh thank you so much for your kind and very informative responses, I really appreciate them :) I was just wondering if my answers fell short in any way, so I asked you. But no issues, and thank you again. I shall also wait and see forward to gaining knowledge from others if they post answers to the questions :) $\endgroup$
    – joy
    Feb 17, 2022 at 22:39
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    $\begingroup$ Wow thank you @uhoh ! $\endgroup$
    – joy
    Apr 25, 2022 at 0:59

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