In a conversation in comments below this answer to the question in Space Exploration Could we see the surface of Venus after the explosion of a H-bomb in its atmosphere? we're speculating about what terms like sulfuric clouds and sulfuric haze mean, and in particular if they are both made of aerosols based on water.

What might be the difference between sulfuric clouds and sulfuric haze, and do both still require water in the form of an aerosol?

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    This may be of use: space.com/5011-mysterious-haze-venus.html – farrenthorpe May 12 at 16:09
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    Surprised this wasn't suggested for moving to Astronomy SE based upon the topic. Though the atmospheric focus might well truly see more knowledgeable experts attentive around here. – JeopardyTempest May 26 at 14:14
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    @JeopardyTempest I know what you mean. For planetary science type questions, Astronomy, Space Exploration, and Earth Science SE are all potential candidates. I was hoping that "cloud vs. haze" might have a planet-independent answer, or that someone here might know enough about atmospheres to better interpret what's been published about Venus' atmosphere. To many people in Space Exploration SE, atmospheres are just something to get out of as quickly as possible, or to use for aerobraking. – uhoh May 26 at 14:24
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    Thanks to the Earth Science SE for its tolerance for our sister planet ! – Conelisinspace Jun 1 at 14:12
  • @uhoh Clouds and haze are aerosols, so what do you mean with "water in the form of an aerosol" ? – Conelisinspace Jun 2 at 11:01
up vote 3 down vote accepted
+100

According to Wikipedia, haze is an atmospheric phenomenon in which dry particulates obscure the clarity of the sky.

Whereas haze is thought of as a phenomenon of dry air, mist formation is a phenomenon of humid air.

However, haze particles may act as condensation nuclei for the subsequent formation of mist droplets; such forms of haze are known as "wet haze".

In meteorological literature, the word haze is generally used to denote visibility-reducing aerosols of the wet type.

According to Wikipedia, a cloud is an aerosol with a visible mass of liquid droplets, frozen crystals or particals suspended in the atmosphere, and the droplets don't have to be made of water.

This article states that standard cloud models for Venus consider that all clouds and hazes are composed of liquid droplets of sulfuric acid mixed with water, with sulfuric acid making accounting for 75% to 96% by weight of the cloud composition. However, other minor constituents may make up the cloud particles.

Clearly regarding the mixture of water and sulfuric acid there is no distinction between clouds and hazes on Venus.

In another article it can be seen on images that the altitude from 30-48 km of the atmosphere of Venus is named "the thin haze region ", whereas the altitude from 48-50 km is called "lower cloud region ".

The figure on page 14 of the dissertation of Yeon Joo Lee also shows that below the cloud layers there is this "thin haze region" which has almost a thousandfold less extinction coëfficiënt than the clouds above it.

Apparently this huge difference in absorbing the light explains the difference and appearance between sulfuric clouds and sulfuric haze on Venus.

Figure 4 of Bullock and Grinspoon 2001 (paywalled) The Recent Evolution of Climate on Venus (Icarus 150, 1, Mar. 2001, pp 19-37) shows the abundances of H$_2$SO$_4$ and H$_2$O in the cloud region of the atmosphere of Venus. A non-paywalled version can be found with an internet search, but since it does not use https I won't include the link explicitly here.

Fig 4 Bullock & Grinspoon 2001 Venus aerosols

Explicitely it shows H$_2$SO$_4$ as a gas in the thin haze region and only in the cloud region there is a mixture of water and sulfuric acid liquid.

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    That's just good practice throughout most science and fact-based SE sites. One reason, though there are others, is that it helps people know you are not making stuff up (which you are of course not in this case). Adding links to sources of quoted and cited information is almost standard, you can look through other answers and see it's almost universal. – uhoh May 13 at 9:17
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    Wikipedia is really, really, really big! You might have read this in an article about meteorology, or one about clouds, or one about pollution, or one about haze, or one about sulfuric haze, or one about Venus, or one about atmosphere of Venus... "According to Wikipedia" by itself is not really helpful because it's impossible to check. – uhoh May 13 at 9:28
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    I appreciate your recommending, but i just wanted to explain my point of view. So since it's just good practice, i think you are allowed to edit my answer. It's good to have exchange of thoughts on this site ! – Conelisinspace May 13 at 11:52
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    @uhoh I'm sorry if i offended you, i can be rather unwilling sometimes. So i've added a link on my answer. And please, don't stop recommending how to write good Stack Exchange answers, we might learn from them ! – Conelisinspace May 26 at 14:20
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    @uhoh I came upon an article that gave me more insight in the atmosphere of Venus so i've changed the conclusion in my answer – Conelisinspace Jun 1 at 10:16

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