increasing cloud cover

[Shiraz]

Hi
The first half of this year was disastrous for cloud cover down this way. The same pattern is evident in the RDO Moorook data (which is a wonderful resource). The plot below of Moorook Jan-Jun monthly average clear nights is self explanatory - over about a decade, we have gone from about 2 nights in 3 being clear to about 1 in 3. Included a linear regression - if it keeps up this trend, we will not have any clear nights at all within another decade :P. Hopefully, if the clouds are all here, they are not somewhere else.

[gregbradley]

That's a very interesting plot.

Perhaps a consequence of the higher average temps during the same period?

Or hopefully merely a cyclical phenomena.

Greg.

[coldlegs]

I can explain only the last three months in SA.
http://www.eldersweather.com.au/dam-level/sa/

Cheers
Stephen

[el_draco]

Wanna bet.... :sadeyes:

[billdan]

Well if its any consolation Ray you will not be getting any bad bush fires this season, according to the ABC.

http://www.abc.net.au/news/2016-08-31/south-australia-bushfire-danger-lower-due-to-soil-moisture/7802450

Cheers
Bill

[pgc hunter]

I'm not too far from Moorook and this winter has been nothing short of Melbourne.

[Atmos]

Melbourne is a pretty good benchmark for poor weather :P

[AstralTraveller]

Don't get him started!! :eyepop:

Actually, the east coast hasn't been too bad. Of course there have been weeks of clouds but also some quite good weather in between. Much better than some winters which are a 100% write-off.

[Shiraz]

thanks for the responses. Good to know that the weather in some other places has been OK, even if not everywhere.

My big worry is that the apparent downward trend in sky clarity down here over the last decade could mean that we have a new "normal", as the increasing temps and associated cloud cover begin to bite. That would be a pity. I would not be so concerned if we had the odd bad year, but there looks to be a fairly consistent and strong trend over a fairly long period of time. Ah well, just another thing that is "not as good as the old days". What with light pollution, clouds and the sun+moon, maybe it's time to build a radio telescope.

[Atmos]

I personally don't think that anything over such a short term scale can be used to deduce anything.
My quite limited understanding is that the vast majority of short term weather patterns (years to a couple of decades) is determined by the El Niño and La Niña which can have a dramatic effect on the weather over all Australia.

Medium term (many decades +) are caused by massive geophysical events (the dark ages) or things such as climate change and CO2 emissions.

[Shiraz]

my understanding is also limited Colin, but there were two LaNina events and two ElNino events in the decade in question, so I would have expected cloud cover to fluctuate quite wildly year to year if the SOI was the driver. Instead it seems to have been on quite a stable and steady decline, regardless of ElNino/LaNina. Maybe something more permanent or with a longer timescale is in play?

Anyway, lets hope cloud cover backs off a bit - and quickly.

[silv]

interesting.
China and US have just ratified the Paris climate thingy.
So hopefully, it won't get worse for you as quickly as it did in the past decade.

[HarryD]

Warm air holds more moisture, ie clouds. Global warming in action, get used to it.

[HarryD]

Tonight and tomorrow night look good here in Sydney. Fathers' day present :)

[Peter Ward]

An important factor in calculating a heavy jet’s optimum operating altitide is the ISA deviation. Some 30 years ago this was typically a random variation around the “standard” ISA temperature...I know this to be true...as often I was the young recruit that had to do the calculation to see if we could climb or not. (I’ve probably made hundreds of not thousands of such calculations)

Nowdays a flight management computer works out the optimum level, however the ISA deviation is almost always hotter than ISA. I’ve observed the trend for some years now’and can only conclude the upper atmosphere is several degrees hotter than it used to be. Hence I dont think its unreasonable hypothesis that our earth’s atmosphere is retaining more moisture, hence more cloud.

[Atmos]

This follows the same thing that usually happened over much longer geological time scales (ice ages). What Peter describes is the green house effect, CO2 and water vapour trap heat within the atmosphere instead of allowing the heat to be emitted into space.

The Earth systems are self regulating though, as the Earth heats up more cloud cover forms which slows down heat escape making the Earth even hotter. It is this mechanism that caused Venus' runaway greenhouse effect; Venus had a mass volcanic event causing mass CO2 out gassing.

What staves off a runaway greenhouse on the Earth is that cloud cover reflects sunlight. So, although the Earth is trapping in heat it isn't receiving as much so eventually we end up in an ice age. Due to a lack of heat reaching the Earth through the cloud cover the Earth cools off which eventually means less cloud cover and we're back where we started.

[multiweb]

I'm easy. I'd just be happy with the next new moon begin clear(ish). Not worried too much about the next 10000 years ;)

[Shiraz]

tried looking up global cloud cover. It wanders around, but there is nothing to suggest that a halving of clear nights over the past decade could be down to a global effect. Looks to me like there is a local effect down in the SE corner of Aus that is causing havoc. Possibly due to the warming atmosphere, but local nonetheless. Maybe a meteorologist could comment - could it be clouds from the huge lows in the southern ocean reaching further north, or maybe more wet air being drawn down from northern WA?

Interesting observation Peter - haven't seen that mentioned anywhere else.

[silv]

http://www.myweather2.com/forecastcloud/player.aspx?fc=47
not historical data, I know. but one can learn something about the cloud forming source, how the earth turns beneath it and swirls it around - until a land mass forms a suction pipe or funnel (pressure, temperature difference) and clouds end up over SE Oz, guided there by the seductive geology of the hanging land belly and Tasmania.

if you say this behaviour was different 10 years ago - then what one can see in the animation in the link is suggesting that the cloud source, i.e. the skies over the outskirts of Antarctica, is more productive, nowadays.

Maybe, for the same reason or due to some other factor, the land mass to the North and West of SE could have changed its weather forming pattern, as well, adding to the funnel effect.

Very interesting.

[Atmos]

My day job gets me working outside, I have noticed in the last 2-3 winters that we have had very few frosts compared to 5-10 years prior. I remember when I was walking to primary school (500m away) in the late 90's we'd have an entire week of frosts every morning.

In the North Eastern Burbs of Melbourne this year I think I have counted 3 frosts in total.

[silv]

it's fascinating yet far too complex for me.
I used to donate my CPU power to a BOINC project called "climateprediction".
https://boinc.berkeley.edu/projects.php

Mind blowing climate models were computed from prehistoric times all the way through into the future and you were able to view those models on a rotating earth.

[silv]

http://neo.sci.gsfc.nasa.gov/view.php?datasetId=MODAL2_D_CLD_FR&date=2015-04-01 is a 1 snapshot per day example of historical cloud cover data available.

an archive of all daily snapshots since 2000 is available in bulk here:
http://neo.sci.gsfc.nasa.gov/about/ftp.php
the folder to get is MODAL2_D_CLD_FR

I used Filezilla as ftp-client to download the big folder because the web-download did not complete as is common with such big packages.

Unfortunately, neither my slideshow-making approach (Aperture 3.5 and iPhoto) nor my movie editing approach (FinalCut Pro 7) would yield a usable and sharable file.
But that is due to the limitations of those programs and my not willing to spend even more time working around those issues.

But the visual data IS there and could be converted into something usable by someone else, I'm sure.

There are also .csv files available of the same time period. I haven't had a look at those, though, because I assumed it would take more time for me to figure out how to use that numeric data and find out how to combine it to make it answer our question.

[Shiraz]

thanks Silv - great links:thumbsup:.

Now to see what the data actually says:) - should be fun. regards Ray

[multiweb]

Looking at the monthly range it is easy to see why you'd choose Atacama or Namibia as prime spots for astro photography.

[silv]

:)
and don't ever move to Iceland!

what 1 daily snapshot, taken during daytime, does not show is locally forming clouds - and of course what happens when temperature drops during nightfall and after.

on the side: I realized that I have no lenghty cloud cover experience in any one place/country/hemisphere since 2000.
Wherever I live I do profit from having observed and pondered the heavens previously from somewhere else.
But memory and experience does not at all suffice to understand or even predict because new local conditions, geography, use of the land, are such significant factors.

[coldlegs]

I seem to recall reading about the "southern forties" heading north due to the circular wind pattern around the antarctic getting bigger or was it faster. Can't remember which. That might explain the increase in southern cloud cover.
Cheers
Stephen

[cfn]

As a feature included in the launch of myCFN (http://www.cloudfreenight.com/member.login) in late spring 2016 you will have access to a number of radar locations ranging from 512km down to 128km or 64km where available along with a few hours of animations in six minutes increments.

I also encourage you to check the new high resolution forecast maps (http://www.iceinspace.com.au/forum/showpost.php?p=1271345&postcount=53) up to 36h.

[silv]

saw a pretty animation (https://youtu.be/-hJmjoowwGU) of the water currents around Europe.


looked for similar animation for Antarctica, didn't find any.
Found The Global Conveyor Belt animation.

anyway, before this, I had only looked towards Antarctica itself as worsening cloud source in the past 10 years.

But of course, the changing water temperatures in the more Northerly parts of the planet and the slow currents add heaps to the observed change in cloud cover.

Actually, the water temperature change - and cloud cover change - which affects you now, might have begun 500 - 1000 years ago.

:jawdrop:

And indeed: there was a temperature rise (https://en.wikipedia.org/wiki/Temperature_record_of_the_past_1000 _years#/media/File:2000_Year_Temperature_Comparis on.png) back then!
That also means it's not them Volkswagen Diesel motors!

And it means that, come the waters of the "Little Ice Age" to South Eastern Australia, your cloud problem will disappear.

[silv]

in about ~600 years time.