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 . Hopefully, if the clouds are all here, they are not somewhere else.
Melbourne is a pretty good benchmark for poor weather
Don't get him started!!
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.
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.
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.
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.
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.
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.
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.
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.
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.
http://www.myweather2.com/forecastcl...yer.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.
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.
. Hopefully, if the clouds are all here, they are not somewhere else.
