The Phenomenon of Mist and Haze
Join Date: Feb 2002
Location: Popham
Posts: 313
Likes: 0
Received 0 Likes
on
0 Posts
A_A wrote:
but if you don't already have a (free) Met Office 'logon', you'll need to get one via the Met Office Aviation Register Page first before using that previously quoted link.
Who knew!!! Just looked it up: http://secure.metoffice.com/aviation...tion=balloonfc
Saw the Haar a lot when I was working in Shetland. Often rather more than a mere 20kts. 20kts was barely a light breeze there. Our limit was 50kts due to door opening limits (although higher windspeeds could be handled if we got the fire truck to park across the nose as a wind break).
It's really weird seeing the fog whip by while expending effort to stand against the wind.
It's really weird seeing the fog whip by while expending effort to stand against the wind.
Spicy Meatball
Thread Starter
Join Date: Jan 2004
Location: Liverpool UK
Age: 41
Posts: 1,115
Likes: 0
Received 0 Likes
on
0 Posts
You guys should talk to my EX re this, he is an expert at throwing up mist and haze to hide the truth
Join Date: Sep 2002
Location: Daventry UK
Posts: 487
Likes: 0
Received 0 Likes
on
0 Posts
What about the 'Warm Sector'? This seems to fit better with the description of persistent haze than mist/fog explanations which surely should vary during the day.
The reduced viz in the warm sector (between warm and cold fronts) can persist for a day or two and make cross country VFR flying impractical despite otherwise stable conditions.
It seems to involve clean maritime (SW) air so I'm not convinced about particulates. But if it is trapped humidity, why doesn't it burn off in the afternoon?
Can someone please explain what causes this reduced viz and where it goes after the passage of the cold front? The idea that the wind just blows it away doesn't quite work for me.
I realise I'm probably displaying cataclysmic ignorance here!
The reduced viz in the warm sector (between warm and cold fronts) can persist for a day or two and make cross country VFR flying impractical despite otherwise stable conditions.
It seems to involve clean maritime (SW) air so I'm not convinced about particulates. But if it is trapped humidity, why doesn't it burn off in the afternoon?
Can someone please explain what causes this reduced viz and where it goes after the passage of the cold front? The idea that the wind just blows it away doesn't quite work for me.
I realise I'm probably displaying cataclysmic ignorance here!
Spicy Meatball
Thread Starter
Join Date: Jan 2004
Location: Liverpool UK
Age: 41
Posts: 1,115
Likes: 0
Received 0 Likes
on
0 Posts
But if it is trapped humidity, why doesn't it burn off in the afternoon?
Join Date: Oct 2002
Location: frozen norff
Posts: 215
Likes: 0
Received 0 Likes
on
0 Posts
Liverpool airport suffers from haze when the wind is from the east round to the south-east; blown from the interior of the country I guess. No idea why the top of the haze-layer varies though; particle size, wind velocity perhaps?
Join Date: May 2005
Location: Suffolk
Posts: 212
Likes: 0
Received 0 Likes
on
0 Posts
mazzy1026 asks why on some murky/hazy warm days the haze (non-technical sense) doesn't burn off in the afternoon.
The answer is the temperature inversion with height. At some point (say 3k ft), the rate at which the air becomes colder with height is lower than the rate at which a parcel of air, heated by the ground, loses heat as it rises.
This means that the warm air rising (or thermal, as we glider pilots say), stops at the inversion. So all the haze remains trapped under the inversion and just recirculates.
If the ground temperature rises high enough, the thermals "break down" the inversion which then disappears. Heated air rises above it to the next inversion, or until it forms cumulus and thereafter runs out of energy at the cloud tops.
If this happens the hazy air below the inversion mixes with the clean air above, and the haze " burns off".
If it never gets hot enough for this to happen (and of course, the haze cuts down solar heating to the ground), the haze remains all day.
A helpful introduction to temperature soundings and forecasting is at:
http://www.itadvice.co.uk/weatherjac...t-snds-01.html
The answer is the temperature inversion with height. At some point (say 3k ft), the rate at which the air becomes colder with height is lower than the rate at which a parcel of air, heated by the ground, loses heat as it rises.
This means that the warm air rising (or thermal, as we glider pilots say), stops at the inversion. So all the haze remains trapped under the inversion and just recirculates.
If the ground temperature rises high enough, the thermals "break down" the inversion which then disappears. Heated air rises above it to the next inversion, or until it forms cumulus and thereafter runs out of energy at the cloud tops.
If this happens the hazy air below the inversion mixes with the clean air above, and the haze " burns off".
If it never gets hot enough for this to happen (and of course, the haze cuts down solar heating to the ground), the haze remains all day.
A helpful introduction to temperature soundings and forecasting is at:
http://www.itadvice.co.uk/weatherjac...t-snds-01.html
Join Date: Nov 2000
Location: Cambridge, England, EU
Posts: 3,443
Likes: 0
Received 1 Like
on
1 Post
Unusual (to me) conditions this lunchtime.
In the past I have encountered either a haze layer or low cloud. Today we had both - low cloud at around 1700', in places, top of haze layer at 3500'. So where there wasn't cloud I could fly above the haze layer in my usual fashion, but where there was cloud I was crawling along at 1500' in horrible visibility.
Still, it's a wasted trip in which you don't learn anything. Today was my first opportunity to refuse an instruction from ATC on the grounds that it would be illegal:
"Expect an overhead join"
"You're joking, I'm not going up to 2000', the cloud is lower than that."
"Er, OK, try a right base join then."
(By which time whilst I wasn't high enough for the overhead join I'd ended up too fast and too high to land from right base, so had to go around. With a first-time-in-light-aircraft passenger, and whilst I'd remembered to stock up on sick bags I'd forgotten to include the "we might have to go around" bit in the pax briefing. Ho hum.)
In the past I have encountered either a haze layer or low cloud. Today we had both - low cloud at around 1700', in places, top of haze layer at 3500'. So where there wasn't cloud I could fly above the haze layer in my usual fashion, but where there was cloud I was crawling along at 1500' in horrible visibility.
Still, it's a wasted trip in which you don't learn anything. Today was my first opportunity to refuse an instruction from ATC on the grounds that it would be illegal:
"Expect an overhead join"
"You're joking, I'm not going up to 2000', the cloud is lower than that."
"Er, OK, try a right base join then."
(By which time whilst I wasn't high enough for the overhead join I'd ended up too fast and too high to land from right base, so had to go around. With a first-time-in-light-aircraft passenger, and whilst I'd remembered to stock up on sick bags I'd forgotten to include the "we might have to go around" bit in the pax briefing. Ho hum.)
Spicy Meatball
Thread Starter
Join Date: Jan 2004
Location: Liverpool UK
Age: 41
Posts: 1,115
Likes: 0
Received 0 Likes
on
0 Posts
I can imagine it's something the weather man may miss out on occasion, due to it's nature - and also, the fact that it can catch you out if your not too careful in the air.......
