[SkylordRic (OP)]

Greetings.

Ok, I'm new here but after much useless searching and researching, I'm hoping that the Naked Scientists can help me. I'm currently working on my first novel and need some help. I've created a unique world and as such, have run into some problems. Ok, here's the set up:

My planet is very similar to Earth in size. the unique thing about it is that large landmasses are raised up thousands (6000-9000) of feet above sea level.  These are known as the Sky Realms. Between the sky realms and the lower realms, at about 4000 feet, is a permanent cloud layer.  This cloud layer is approximately 50-100 feet thick (ok, ok, it was created magically but is otherwise made of real clouds.) covers all but the polar regions and is roughly 400 years old.

So, of course, I go and create this cloud layer and my story takes a life of its own and now one of my sky realm characters is stuck in the lower realm. Great, I wasn't expecting to do that in this book but now I have to figure out what he's getting himself into.

Questions:

1. What kind of climate would exist in a land that has been under a
 constant layer of clouds for four centuries?  Would the atmosphere be
 thicker, hotter, more humid (super greenhouse) or would the cloud
 cover act more as a 'nuclear winter' and create a colder, thinner,
 more dry environment?
 
2. How would this climate affect flora and fauna?  Would there be a
 proliferation of flora or would it become more sparse?  Would fauna
 be affected adversely with a higher concentration of certain gasses?
 Would the diminished sunlight be beneficial or harmful?  I'm assuming
 that the decreased UV radiation would allow for longer life among
 biological lifeforms and perhaps the thicker atmosphere would allow
 for some lifeforms to grow larger than usual (i.e. the giant sloth
 from our own historical record).  This question has more to do with
 physiology, I know.
 
3. Would areas near the equator be affected more than areas closer to
 the polar regions assuming the cloud layer thickness is constant?
 
4. How would the thickness of the cloud layer affect the lower
 climate?  Would a thicker (closer to 200' ) layer perhaps approach
 more of a 'nuclear winter' scenario assuming a 100' layer is
 creating a 'super-greenhouse' scenario?
 
5. Are there any meteorological impacts above or below the cloud
 layer created by the lower climate?  Perhaps the sunlight reflecting off
 the cloud layer would affect the otherwise normal climate in the sky
 realms?

6. What kind of day-to-day chages would there be compared to normal (Earth-like) environment?
 There would be less sunlight, but would there be more fog becauswe of the humidity? Would storms
 beneath the layer be more intense or weaker?

Of course I also have questions about my characters physiology coming from a high altitude environment to a low one, VERY quickly.  But I can ask those types of questions in a more specialized forum.

I've had absolutely NO LUCK trying to find answers to these questions. Even the folks at NOAA said this was out of the realm of their expertise.  I'd be happy with an informed person's best educational guess. 

Anyway thanks in advance if anyone would be willing to try helping me.  I'd appreciate it.  If I don't get answers soon, I'm gonna have to wing it.

[another_someone]

What is driving the clouds?  Normal water cycles usually are driven by sunlight evaporating water, creating clouds, and then those clouds precipitating elsewhere.  Permanent cloud would mean that this cycle would be more limited, because less sunlight would get through, so less water would be evaporated (and if the cloud remains, then it cannot seriously be depleted by precipitation).  Are these water clouds at all, or clouds of something else?

Generally, since the weather is driven by solar heat, with less solar heat getting through, one would expect less weather (i.e. less winds - although less than what may depend on other factors on the planet; less variation in temperature, etc. - on overcast days, even on Earth, night and daytime temperatures are more similar than on days when you you have clear skies).

Clearly, as there would be little difference between daytime and nightime temperatures, you could not have morning mists, etc.

Another factor is ofcourse terrain.  High mountains can have a significant influence on cloud cover, potentially blocking clouds from getting beyond them.  To have continuous global cloud cover, the clouds must extend higher than the highest mountains (or at least, the highest mountain ranges) on the planet.

[paul.fr]

This layer of cloud, is it what we would class as a cloud (mass of water in sky: a visible mass of water or ice particles in the atmosphere from which rain and other forms of precipitation fall) or something caused by say a nuclear war - a fall out cloud, say?

What happened to the climate to bring about this cloud?

If the cloud is one made of water, then one possible cause for it could be similar to the conditions that caused the great smog in london, 1952. Not just the industrialisation but the weather conditions itself. Like the great smog, you could have an anticyclone centered over part of the whole of your earth like planet. With an absence of any wind, this would / could also produce a temperature inversion.

Temperature inversion
inversion - wikipedia

The climate below the cloud, would be similar to that of the great smog. Not a very nice place to live, but in effect you would have two different worlds. The one below and one above the cloud.

This picture shows radiation fog, this possibly will not work for your scenario, but showes how a lower cloud base may look.
 [ Invalid Attachment ]

[another_someone]

But the smog itself, while severe, was intermittent, and London still got some sun.

Nonetheless, the idea that the clouds were photochemical in origin rather than water evaporation (which chemicals from the surface drifting up to high altitudes, and then subject to reaction from sunlight at high altitudes), would ease the issues about how one adequately drives an evaporative cycle that would require adequate heat at ground level.

Ofcourse, the other option might be that the heat driving the atmosphere is not only solar heat, but substantial volcanism.  This can both pump water directly into the atmosphere, the heat of the volcanoes could cause evaporation of surface water, and particulate matter in the volcanoes could create nucleation points that would make it easier for the water vapour to condense into clouds.

[paul.fr]

But the smog itself, while severe, was intermittent, and London still got some sun.

Yes, but the smog only cleared when a southwesterly wind cleared the air. If the inversion was 'world wide' this could sustain a smog. However, having just reread the original post, i see that the cloud was created by magic.

So the question turns to the possible climate below and within the cloud layer. Assuming you still have a moving wind, i would expect there to be an increase in the frequency of lightning within the cloud as the friction increased. If the cloud layer is always present, that combined with wind should increase the friction and produce more cloud to cloud and cloud to ground lightning.

As for the temperature on the ground, assuming that volcano's are active and other industrial processes. I would think that on the whole the temperature would decrease. If you have high level cirrus clouds and an increase of pollutants such as sulfur dioxide from volcano's, this would increase the albido of those clouds, and eventually you would have global acid rain.

[another_someone]

This is why there needs to be an understanding of exactly what the clouds are composed of, and the overall level of humidity in the atmosphere.

And while it is true that probably the albedo of the planet will rise, and this will lower daytime temperatures, but there would still be less nighttime cooling, and the change in albedo could still be accompanied by a greenhouse effect if the opacity to infrared still exceeded the opacity to visible light.

It also depends on the rainfall, since rain itself will generally cool the environment, while a high humidity without rain could contribute to global warming.

I would agree with the increase in lightning - although again, how much of an increase is dependent on many factors, but increase there will be.

In many ways, the question of warm or cold may not be that relevant, since this will depend on what people are used to.  Someone (on Earth) flying in from a tropical winter to a temperate summer, might still consider the climate cold despite all the locals walking around in skimpy clothing saying how hot it is.  Similarly, someone used to an antarctic summer would still consider an winter in the temperate regions to be balmy and warm.  What is hot and what is cold will depend on what people are used to day to day, and the one thing we can say, whatever the actual temperature, is that it will actually vary very much less than normal temperatures on Earth, so they wont feel their winters cold and their summers warm, because winter and summer will have very much more similar temperatures than we would experience here, and day and night would also have very much more similar temperatures.

[SkylordRic (OP)]

Whew! Okay, I see I have some serious decisions and definitions to make regarding this cloud layer in order to find the results.

Let's say that this layer is created by an inversion (artificially created by elemental magic).  If this were the case and the cloud layer is static at 4000', then the atmospherebelow would be thus: smoggy, dusty, and cold.  (keeping in mind that the tech level for this world is pre-industrial and closer to pre-medieval ages so most pollution would be natural (volcanic, etc.)) Is this correct?

But, if the cloud layer is simply the by-product of the elemental magic, would another climate exist? The clouds are normal, vaporous clouds that are held, unnaturally, at 4000'.  Is the climate still smoggy, dusty and cold or more humid, warm and clear?  Or perhaps a combination of the two?

Keep in mind that the climate above the layer is normal and seasonal. As such, the lower climate still receives rain and wind from upper storms.

By the way, thanks to both of you for answering and discussing this post.  If nothing else at all, I'm beginning to see exactly the problems I have on my hands here.

[paul.fr]

Whew! Okay, I see I have some serious decisions and definitions to make regarding this cloud layer in order to find the results.

Let's say that this layer is created by an inversion (artificially created by elemental magic).  If this were the case and the cloud layer is static at 4000', then the atmospherebelow would be thus: smoggy, dusty, and cold.  (keeping in mind that the tech level for this world is pre-industrial and closer to pre-medieval ages so most pollution would be natural (volcanic, etc.)) Is this correct?

Yes, the daytime weather would be cold smoggy and dusty. Warming slightly at night, as George says.
As for it being set in pre-medieval times, i guess they still burn wood which would add to the atmospheric pollution (trapped by the cloud layer), perhaps George knows more about pre-medieval times than i do and can add more about what types of fuel were used and the possible impact.

But, if the cloud layer is simply the by-product of the elemental magic, would another climate exist? The clouds are normal, vaporous clouds that are held, unnaturally, at 4000'.  Is the climate still smoggy, dusty and cold or more humid, warm and clear?  Or perhaps a combination of the two?

Keep in mind that the climate above the layer is normal and seasonal. As such, the lower climate still receives rain and wind from upper storms.

Yes again, but seeing as it is caused by magic you will have some poetic licence as to the effects caused by the magic within the cloud layer.
You would still expect there to be more frequent and violent thunder in and below the cloud. If it was still raining above the cloud then this would possibly dilute the build up of acidic rain, a sort of washing it out before levels got too high. Of course, the flora and fauna would still suffer, but possibly over a longer time span.

By the way, thanks to both of you for answering and discussing this post.  If nothing else at all, I'm beginning to see exactly the problems I have on my hands here.

No problem, the weather is far more complicated that it first appears, and it gives George and I the opportunity to bounce ideas...

[SkylordRic (OP)]

Whew! Okay, I see I have some serious decisions and definitions to make regarding this cloud layer in order to find the results.

Let's say that this layer is created by an inversion (artificially created by elemental magic).  If this were the case and the cloud layer is static at 4000', then the atmospherebelow would be thus: smoggy, dusty, and cold.  (keeping in mind that the tech level for this world is pre-industrial and closer to pre-medieval ages so most pollution would be natural (volcanic, etc.)) Is this correct?

Yes, the daytime weather would be cold smoggy and dusty. Warming slightly at night, as George says.
As for it being set in pre-medieval times, i guess they still burn wood which would add to the atmospheric pollution (trapped by the cloud layer), perhaps George knows more about pre-medieval times than i do and can add more about what types of fuel were used and the possible impact.

I think I'll stay away from the inversion and its affects.  I think this would create more of a nuclear winter scenario than I'd like.

But, if the cloud layer is simply the by-product of the elemental magic, would another climate exist? The clouds are normal, vaporous clouds that are held, unnaturally, at 4000'.  Is the climate still smoggy, dusty and cold or more humid, warm and clear?  Or perhaps a combination of the two?

Keep in mind that the climate above the layer is normal and seasonal. As such, the lower climate still receives rain and wind from upper storms.

Yes again, but seeing as it is caused by magic you will have some poetic licence as to the effects caused by the magic within the cloud layer.
You would still expect there to be more frequent and violent thunder in and below the cloud. If it was still raining above the cloud then this would possibly dilute the build up of acidic rain, a sort of washing it out before levels got too high. Of course, the flora and fauna would still suffer, but possibly over a longer time span.

Ah! now here is where I'm getting the answers I'm looking for.
So the climate would be more humid and hot and clear? 
Any acid rain that would exist would come from pre-industrial  (woodfires, lampoil flames, etc.) or natural (volcanoes, forest fires) sources.  So I don't think the event of acid rain would be that common especially with normal storms to wash out the cloud layer as you mentioned. Hmm, I'll have to give this some thought.

But as to the lightening and thunder: How common would this be? Would a lightening storm just appear for a couple minutes or hours or would a person walking the countryside see a lightening strike every five or ten minutes and hear thunder with it?  Or would the entire, global lower realms be in constant danger?  I gotta tell you, I never thought about the cloud friction and thunder and lightening. I love this idea.

By the way, thanks to both of you for answering and discussing this post.  If nothing else at all, I'm beginning to see exactly the problems I have on my hands here.

No problem, the weather is far more complicated that it first appears, and it gives George and I the opportunity to bounce ideas...

Weather is definitely more complicated than I thought and I'm glad there are people out there willing to think outside the box for me. The ideas that come into my head when I read your posts are amazing and I can see the world being created and recreated in my mind's eye.  Your idea-bouncing is more helpful than you can imagine.

And I see over 200 people have read this thread. If any of you have ideas or $.02 to add, I'd love to hear it. 

[another_someone]

Ah! now here is where I'm getting the answers I'm looking for.
So the climate would be more humid and hot and clear? 
Any acid rain that would exist would come from pre-industrial  (woodfires, lampoil flames, etc.) or natural (volcanoes, forest fires) sources.  So I don't think the event of acid rain would be that common especially with normal storms to wash out the cloud layer as you mentioned. Hmm, I'll have to give this some thought.

Not sure that acid rain would actually do anything to reduce vegetation, at least in the long run, but it would change vegetation.  Some vegetation is very tolerant of high acidity, while other vegetation needs a more alkaline soil.

There are many things that can cause acidity in the atmosphere.  Any high sulphur fuel could be burnt to create sulphurous smoke.

The main difference in the pre-industrial world was that far less of anything was burnt - so it was not that the fumes were less acidic (in fact, they were probably more so), but there were just less fumes.  In fact, wood fires can be some of the most polluting fires around, but it is merely the scale of burning since the industrial revolution that has changed things.

That having been said, natural peat fires can cause enormous air pollution, with massive clouds of brown haze having blighted much of Asia a few years ago just from such natural peat fires.

But as to the lightening and thunder: How common would this be? Would a lightening storm just appear for a couple minutes or hours or would a person walking the countryside see a lightening strike every five or ten minutes and hear thunder with it?  Or would the entire, global lower realms be in constant danger?  I gotta tell you, I never thought about the cloud friction and thunder and lightening. I love this idea.

It need not be a lightening storm (depends on the nature of the clouds) - it could be just sheets of lighting without any rain beneath at all.

How much lightening depends on how much energy is stored in the clouds.  Again, with the use of magic - you have quite a bit of flexibility about how the energy builds up and dissipates in the clouds.

Lightening could also happen at different altitudes, depending on the weather (bear in mind that much lightening never actually strikes the ground).

If you have too much lightening, you would probably be dealing with a fair amount of wind as well, since that implies a lot of energy (ofcourse, high altitude wind need not be the same as low altitude wind - this would not be a surprising scenario if you have a lot of lightening, since the wind shear could contribute to the buildup of charge that triggers the lightening).

[paul.fr]

A lot of information since i last looked in, i will not use the quote facility but try and address some of the possible issues. Too many blocks of quotes, i find distracting. Plus i am quite lazy...

Acid Rain.
Although this is preindustrial, i still think that acid rain could be both a problem and a solution, due to the cloud layer. The problem would be possible devastation to your woodlands and other fauna, although this does not have to be a global event, it could be centered around large or abandoned villages where they burned wood and had a high frequency of peat fires. Or simply around areas of large volcanic activity.

It could also serve as a solution to introduce new, strange and wonderful plants, flowers, etc. For the reasons George stated, with the acidity of the soil changing.

Thunder and Lightning.
Again thunder, lightning and it's intensity and frequency need not be global. If the clouds are made by magic, and your world does not have strong persistant winds, then perhaps there is a local event (a magical hot spot) or rip in the cloud which causes the wind. The thunder and lightning would be centered on this region. This would explain the winds and the friction within the clouds

Earlier we discussed the albedo of the clouds, and in the link given above it states:

"Most thunderstorms are associated with towering clouds known as cumulonimbus. The right conditions for the formation of a thunderstorm are (a) unstable air and (b) a mechanism for causing air to rise.

Air is said to be unstable when a 'parcel' of air continues to rise of its own accord after being given an upward impetus. This instability is the result of a rapid fall of temperature with height as well as a considerable amount of moisture. The mechanism may be provided by a sufficiently warm surface; the air near the surface being forced to rise over higher ground; or instability in the large-scale ascent within a front."

The break within the cloud or the albedo of the cloud, caused by the rip/magical event could give you these conditions. If there was such a rip/event then you could effectively control the thunder and lightning by the power needed to open or control the rip/event.

The greater the power, the stronger the wind, the stronger the wind the greater the thunder.......

[another_someone]

It could also serve as a solution to introduce new, strange and wonderful plants, flowers, etc. For the reasons George stated, with the acidity of the soil changing.

http://en.wikipedia.org/wiki/Ericaceae

The plant family Ericaceae (also called the heath family or ericaceous plants) are mostly lime-hating or calcifuge plants that thrive in acid soils. The family Ericaceae includes numerous plants from mostly temperate climates: cranberry, blueberry, heath, heather, huckleberry, azalea and rhododendron are well-known examples.

I am not saying these are the only plants, but they were the ones that came to mind.

[SkylordRic (OP)]

I can't thank you two guys enough for all the information you've given me here.  This has helped so much and the links you've both provided have been invaluable and really helped me clarify a few things.  So I've really just got one more question.

When the cloud layer is destroyed (later, not in THIS book) what will be the immediate affect on the global weather?  Having all of this massive heat and humidity suddenly released I imagine would result in widespread thunderstorms?  Would there be tornadoes, hurricanes, possibly blizzards in the winter hemisphere?  With all of that hot, humid air suddenly rising to meet the cooler upper atmospheric weather I can just see lots and lots of rain and flooding.  Am I on the right track?

[paul.fr]

Now that is a tricky one, i will have to think (always a dangerous thing) and reply over the weekend.
For your storyline, is there an outcome that you would prefer? Perhaps George and I could try and work a possible scenario to fit.

[SkylordRic (OP)]

Nope, nothing specific. It's going to happen so I really don't need any one thing to happen but I do want to be realistic with it. I can imagine how massive an event it has the potential to be and that it would last for days IF anything happens at all.

[another_someone]

The first thing I can imagine that would happen with the sudden removal of the clouds is a massive increase in the amount of sunshine reaching ground level.  For life that has evolved to cope with relative low levels of diffuse light, the sudden increase in light could be scorching (note that I am not talking about the higher air temperature, although that would be an issue, but the more severe issue would the the damage caused by direct light radiation - to humans, this would be sunburn on pale skin that is not used to sunlight, but to plants it could be even more deadly).  They would also find the nights freezing cold (particularly in winter), but coping with the sun I would imagine to be the greater problem.

Bear in mind also that the nature of the rivers would change also.  The ground would become dryer and less water logged, and having wider ranges of temperature and more seasonal rainfall (although the cloud cover would not prevent there being a rainy season and a relatively dry season, but there would be unlikely to have been a really dry season, just a less rainy season), but with the removal of the clouds, you could get faster running rivers that would swell more when the rains come, but get quite short of water in the dry seasons.

Maybe Paul has some ideas about how much seasonal variation you could get in rainfall when under perpetual cloud, but I would imagine far less than you would get when the clouds are removed.

In the short term, the sudden removal of the clouds would be an ecological disaster in a world that had adapted to continual cloud cover.

One benefit of the sunlight would probably the reduction of insect borne disease, as the ground is less water logged; but this would probably be more than offset by the starvation caused by crop failures, as all the existing crops would die off, and until new crops could be introduced that were more suited to the new climate.

Very small point, but a world without a cloudless sky is also a world without strong shadows, so with the removal of the clouds, it would be the first time these people (if they had no artificial light) would have seen strong shadows.  Even the colours of things would change (our eyes are used to seeing things under both cloudy skies, and sunny skies, so we are used to adapting to the differences - in the first instance, the colours might seem strange to people who are not used to them, although they would quickly adapt).  Textures would certainly seem different because of the effect of shadows.

Shadows are not only for small things, but even the shadow a mountain has over a nearby valley would be a strange effect to them.

Also, think about the nightime sky.  It is the first time people would have seen the stars, and even if they had seen a faint outline of the moon, it would never have been a clear image.  This is critically important in a world without artificial light, and with limited navigation tools.  In the days before artificial light, moonlight made a lot of difference if you were out and about during hours of darkness, so people would more likely go out on a moonlit night, but stay in during the nights of a new moon.  This is also true of other animals, besides humans - hence stories of wolves and alike roaming during the full moon - they did this, because they too could see by the moonlight.

Another thing you would probably find is that while on a cloudless evening, darkness would come a little later, it would come more suddenly; so for people who were used to waiting until the light started to fail, and then rushing home, and getting home just as it was finally fully dark, might now get caught out in total darkness.

[paul.fr]

Just a few quick things that have been rolling around. I have not fully read your last reply George, but it seems we have approached this from different angles. Which is quite interesting.

I thought of this, the cloud being removed, as a violent event. The few idea's that i do have, may not be too clever, but I have my daughter for the weekend, and may not have much time to give this too much thought until the beginning of next week. So i thought i would just throw this out and see what you both make of it. I will properly read your reply/ies over the weekend, George.

1. On the assumption that the cloud layer is destroyed in a violent manner, there could be a large buildup of friction and heat, resulting in severe and devastating storms (hail, rain,wind, thunder and lightning).

2. The newly released moisture in to the atmosphere can do one of two things. One some of the land it may rise to both form and enlarge the thunderhead (Cumulonimbus clouds), these would release both hail and then rain. With the possibility of creating tornado's.
Or the moisture forms high level cirrus clouds, damping down the storm. Again, both events can take place in different parts of the surface.

3. Would or even could the wind generated by the distruction of the cloud cause a jetstream effect? Or Possibly a nuclear winter effect?

4. In the area's where great storms are present, the lightning could set fire to whole area's of forrest / woodland. This would release smoke, ash and particles in to the air, resulting in a drop in temperature and precipitation. Something like a nuclear winter, this can be localised to a continent.

5. Area's spared of the thunder and lightning, but still subjected to storms would see crops fail and flooding caused by both hail and rain.

Sorry that this is not more concise, but like i said above, i thought i would just get some notes down so they can be picked over. And yes, my 'world' seems far more gloomy than Georges

[another_someone]

I think the differences are between the short term view Paul has looked at - what happens in the days or weeks over which the cloud disappears, whereas I was looking at what happens after the cloud has gone.

Much has to depend on how quickly the transition occurs.

[paul.fr]

Another quick reply:
"when the cloud layer is destroyed what will be the immediate affect on the global weather?"

How is the cloud layer destroyed? I know you used the word destroyed, so is this simply an act of magic 'poof, the cloud is gone'. Or something violent, say an explosion?

If it is a violent event then i would say that the release of energy would more than likely produce greater winds, storms and the thunder stated previously. Although I don't think this will actually be an event that lasts for any considerable length of time, the winds that are created in the 'explosion' would also have the effect of neutralising the thunderheads, ripping them apart. Any tornadoes or hurricanes would also be 'snuffed out' due to the windshear. You could end up with less hurricane activity, over a given year, but increased power of those hurricanes.

Now that your cloud layer has gone, the immediate effects of it's destruction are over, what next?...

In addition to what George has already written, i would add the following.

For starters you are now going to have a totally different climate. When the cloud layer was there, most of the solar radiation was blocked (incoming) and terrestrial radiation was also blocked (outgoing). Where before you had cloudy days (these are cooler than sunny ones) and cloudy nights (warmer than clear ones), you now have a mixture - cloudless sunny days bringing the heat, cloudless nights loosing heat or a mixture in different parts of the 'Earth'

Will you still have cloud, natural cloud? Well yes, you have already said that the upper world has normal seasons and rainfall, not knowing the layout or how this upper world looks and operates, now makes this harder.

The lower world is now going to be creating cloud in both the lower and upper worlds, but more of it. You are going to have more water in the atmosphere from evaporation (water from the oceans, lakes, seas and sodden land) and transpiration(plants, trees, crops). All of that increased water will lead to more rain, this could be devastating to low lying land,(IIRC) an annual rainfall of 1 inch gives you just over 66,500 tonnes of water per square mile. Of course this would also benefit more tropical and higher elevated areas. Where in one area you have crop failures you may have a bountiful harvest in another.

Most of the extra rain would end up in your oceans and rivers, either directly or as natural run off. You may also have the benefit of richer soil through percolation. You then have faster running rivers that would allow speedier travel for anyone that uses boats.

With all that new heat, you would also expect there to be greater convection and thermals. This could help migrating birds.

Now that you have more 'natural' weather, you would begin to have climate zones. Not sure how long it would take to establish these, but magic could solve that. Of course, you will also have variations and freak weather even in established climate zones. Think of our own weather, daffodils in February, snow in June...

So what are the climate zones? If yours are anything like what we have then this is a somewhat rough guide:

Tropical
Dry
Temporate
Continental, and
Polar.

As George has said

Bear in mind also that the nature of the rivers would change also.  The ground would become dryer and less water logged, and having wider ranges of temperature and more seasonal rainfall (although the cloud cover would not prevent there being a rainy season and a relatively dry season, but there would be unlikely to have been a really dry season, just a less rainy season), but with the removal of the clouds, you could get faster running rivers that would swell more when the rains come, but get quite short of water in the dry seasons.

Which i hope i have covered, in part. But it's not all a rain - flood cycle, because you are going to create those climate zones mentioned above. So you will have desert, more lush tropics and greater temporate climates.

As you can see from what George and I have said, your climate is going to change and the impact upon the population could be great. Again this will be both a benefit in some areas and devastating to others. It all depends on how you want to go and also what is happening to and in the area that was above the cloud.

Don't forget the seasons. Are your characters based on different hemespheres? If so they will have different weather systems, if not, then you get to choose what their weather is. Say arid and pestilent in a continent during it's first summer in 400 years, or struggling through the harshest winter of that time.

Is there a new 'magic' in play - for good or ill?

[SkylordRic (OP)]

You guys are awesome.  I had thought of some of that stuff but you guys went beyond that and I thank you for it. 

The destruction of the cloud layer will be one of the last events in this story arc so I'll probably not have to worry too much about the lasting effects, just the immediate.  And the 'destruction' of the cloud layer I envision more as a quick dissipation rather than explosive or poof!-and-it's-gone.

You guys have given me tons to think about.  I never thought a simple climate question would involve so much.  I have a new respect for meteorologists and climatologists. But I've been able to shape a pretty morbid world out of all this info so I hope it translates well into the writing.  It ought to be fun.