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BotB - what's the mechanism for setting up localised thermal circulation in a cloud? Is it always associated with rain? And is it true that the bigger the cumulonimbus (?) and the faster it's bearing down on you, the bigger the squal on the leading edge?
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Originally Posted by simonrp84
(Post 18634984)
Part of my job is looking at clouds (from above, with satellites) and so this thread seems pretty interesting. Keep it up, guys!^
I'm curious if there are now any additional weather satellites or new technology being used to derive weather images? Back in my operational days...we used satellite pictures from Geostationary GOES (US) or METEOSAT (EU) satellites (very high orbiting (22,000 miles above Earth) satellites that used infra-red imaging to provide pictures) ... This is an example of a visual image from an EUMETSAT METEOSAT weather satellite from today over Europe...you can see the low pressure centre off of Brest in France and the cloud that is starting to come in from the South West... http://farm8.staticflickr.com/7083/7...cbc71423_z.jpg nLojcvWRzRtJk by EUMETSAT, on Flickr image copyright 2012 EUMETSAT :) ...There are also Polar Orbiting NOAA (1000 Km above Earth) satellites that use visual black and white images to provide weather information... Has there been developments in this area since? Care to take over the podium to discuss satellite weather images and the issues with trying to figure out if the temperature indicated is a thick cloud or a high cloud? Other issues? Don't mean to put you on the spot! Just curious and wondering if you wish to add to the discussion? Thanks! ^ :) |
Originally Posted by ColdWalker
(Post 18648666)
BotB - what's the mechanism for setting up localised thermal circulation in a cloud? Is it always associated with rain? And is it true that the bigger the cumulonimbus (?) and the faster it's bearing down on you, the bigger the squal on the leading edge?
I'll try a quick version and we can discuss in more detail if you like when we meet at the BA Flight Safety Awareness course coming up ^ during breaks or with a pint afterwards ;) So, I'll assume your question implies some cloud exists already (in which I mean that due to a temperature difference somewhere the imbalance has caused some hot air to rise, cool and saturate, causing cloud...and that the cloud development has been in one direction so far...upwards...which causes growth of the cloud)...please correct me if this is not what you mean or I have misunderstood your question... So, now to the question: what is the trigger to cause the 'in-cloud' localised convection instead of the up until now 'only upwards or vertical' air flow in that same cloud.... The answer is essentially: how long is a piece of string...but to have a stab at it... Change. In other words...some local effect such as wind direction, more heating from the Sun, warmer water or land surface temperatures, more CCN (Cloud Condensation Nuclei) from pollution or an outgoing tide exposing kelp on the rocks for example...etc...any one of these things or a smaller change in a number of them...but at the heart of the matter is that 'something' allows the growth of the cloud to reach a critical point where there is not only upwards motion in cloud but that the cloud has grown enough to allow smaller convective cycles inside the cloud. Once you have a large enough Cumulus cloud for example it can start to have these internal convective cycles which instead of dissipating the cloud, due to the size and whatever is allowing it to be continuously 'fed' it keeps growing and maintaining its size... Once you get that upwards AND downwards motion inside the cloud happening...you get some moisture wrapped around particles (CCN) that are travelling with that parcel of air as it goes up and down and as it is 'pushed' up and down it will collect more 'water' (or will freeze to become solid) as it moves vertically and cools passing through the already saturated air or melts the outer ice and/or dissipate as it warms up and descends...if the vertical channels are sufficiently developed (high enough, repeated often enough) then you start to form precipitation...the drops get bigger and bigger as they get repeated 'spun' around inside the 'saturated' air inside the cloud...until one of two things happen...the cycle changes due to the cloud 'dying' or the impetus that allowed the growth and development changes so the cloud and the internal convection 'decays' OR the drop becomes too heavy for the convective air channels to continue to be able to 'push' it any longer...so it falls... The drop will fall until it either A) hits the surface of the Earth and ends its 'journey' (to be later evaporated and restart the cycle as conditions allow) OR B) the descending warmer air has enough 'potential' to soak up the moisture of the drop as it passes through that air and therefore the precipitation either dries up and dissipates or gets then caught up in some other convective or other wind to move to those conditions...(typically when a drop passes through a cloud the air is saturated so will continue to fall...however, once below the cloud the air is not saturated (or it would be cloud) and is warming up as it descends so it becomes a race...does it make it to the surface before the atmosphere can absorb the moisture or not! So precipitation does not always accompany such convective motion in cloud in the beginning but if the cloud is able to sustain the internal convection it will usually be later accompanied by precipitation (or VIRGA). The last questions about CB clouds and the size and speed they travel at being correlated to the squall line ahead of that CB...short answer is unfortunately no but as a rule of thumb it is not completely wrong... Put simply...it would depend on location, conditions and air mass. Reason...you can have a very moist, very warm air mass in a Northern (for example UK) region that can have a CB develop to only 30,000 feet but be very intense and have a very strong squall line ahead of the CB especially over water where there is 1/3 less friction...which could be more intense than an Equatorial weaker air mass (say cooler temperatures and less moisture capability) over land that also produces a CB cloud...the cloud could be then be the same height of 30,000 feet but would have more friction to overcome and not sustain itself as well so not have the same intensity wind... But as a general rule of thumb..yes, a bigger CB does denote a higher squall wind as the convective outflow from the cloud on the leading edge would be much more developed as the cloud is thicker and therefore has a higher vertical cycle = more wind. The speed would be an indicator but you need to be careful in that the conditions need to remain the same...i.e. the cloud always remains on water or always on land...when you change from one to the other or have a change in terrain...for example when you move a CB coming off the water West of the UK and it hits the Pennines it will slow down from the 'local' effect and therefore the squall will change as well... Still ended up being a too long answer sorry...but I hope this answers the question you asked ColdWalker? ;) I do hope that the above bit on precipitation is of general interest to others here as well...it is an important bit of how weather forms and is why we can get hail occurring when there is no cloud about! (the vertical convection can develop so strong that the drop moves up and down accumulating in size until it at some point reaches the Jet Stream and then gets blown along that until some condition changes and it then falls out of the Jet and falls to the Earth...causing damage to crops, houses, sensitive BA airplane skin (if the hail is big enough!...see what I did there ;)) |
Just after take off from LCY on the way to SNN on the BA001:
http://i657.photobucket.com/albums/u...n/SL381419.jpg Still on the way to SNN on the A318: http://i657.photobucket.com/albums/u...n/SL381427.jpg Somewhere approaching the US on the BA001: http://i657.photobucket.com/albums/u...n/SL381445.jpg On the New England cost, Ogunquit, ME: http://i657.photobucket.com/albums/u...n/SL381758.jpg From my World Traveller seat (Oh lord, did I really do that...?) departing SFO, with the sun behind us: http://i657.photobucket.com/albums/u...p/SL381117.jpg Somewhere over the Gulf of Mexico on the way to Nicaragua: http://i657.photobucket.com/albums/u...p/SL380989.jpg From an A320 flight deck, somewhere... : http://i657.photobucket.com/albums/u...HR/FDview1.jpg Another one taken on the way to somewhere... Can't remember where: http://i657.photobucket.com/albums/u.../New320Eng.jpg |
Thanks for the explanation BotB.
65,000 feet is quite a height. |
It does answer my question. In fact what a full answer ^
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Brilliant pictures BBB ^
Can't resist commenting on at least some of them...
Originally Posted by BingBongBoy
(Post 18648877)
Somewhere over the Gulf of Mexico on the way to Nicaragua: http://i657.photobucket.com/albums/u...p/SL380989.jpg Good thing I wasn't flying...I would have been porpoising in and out of those cloud tops, screaming like a kid at a water park! :) Another one taken on the way to somewhere... Can't remember where: http://i657.photobucket.com/albums/u.../New320Eng.jpg Hope to see more if you get the chance once in a while between other things with the new long haul flights ^ |
Originally Posted by BotB
(Post 18650242)
Lovely scenery! A good example of how little 'lift' is needed to develop cloud in such warm, hot environments...these are not threatening yet though...friendly little fellows...
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Originally Posted by BotB
(Post 18650242)
Brilliant pictures BBB ^
Originally Posted by BotB
(Post 18650242)
A great, but scary photo :eek: Do you remember how the weather developed after that? Curious if it was just threatening or if you had any thunderstorms / worse!
Originally Posted by BotB
(Post 18650242)
Lovely scenery! A good example of how little 'lift' is needed to develop cloud in such warm, hot environments...these are not threatening yet though...friendly little fellows...
Originally Posted by BotB
(Post 18650242)
Ooh, I want one...:D
Good thing I wasn't flying...I would have been porpoising in and out of those cloud tops, screaming like a kid at a water park! :)
Originally Posted by BotB
(Post 18650242)
An excellent example of the boundary layer...you can clearly see the change in colour and an almost clearly defined line where the sky becomes a nice clean blue and below that a bit fuzzy grey tinge to it....this is where the winds are still producing a turbulent flow and causing some pollution, particles, cloud, etc...but above that...nice and smooth...Very nice!
Hope to see more if you get the chance once in a while between other things with the new long haul flights ^ On another note... All VERY interesting stuff here, keep the information coming! ^ |
Nice cloud-free satellite image of the UK. :cool:
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Jersey Fog
Okay, thought I would get a discussion going about some local weather that is causing some issues today...the Jersey fog which delayed some BA flights from LGW today and may affect some more flights tomorrow! :(
I'll come back to the recent pictures and other questions later but hope this is of interest. The Jersery Met Office website can be found here: http://www.jerseymet.gov.je/ and you can get a general public forecast or go to the Aviation link on the left which will provide a better weather brief for pilots as well as the TAF's (TAF is an acronym for Terminal Aerodrome Forecast) which is very detailed and precise, designed specifically for pilots and airports to best plan their schedules. They are usually valid for 24 hours and are issued 4 times a day (usually) for a specific location and the immediate area. The current TAF for JER is: JERSEY - EGJJ 291657Z 2918/3003 VRB05KT 9000 FEW002 PROB30 TEMPO 2920/2903 0500 FG BKN000 This decodes to say that at Jersey a forecast was issued on the 29th May at 1657 Zulu time (UTC which does not adjust for daylight savings so is one hour behind UK time) covering the period between 29th at 1800 Zulu to the 30th at 0300 Zulu so from 29th at 7 PM local until the 30th at 4 AM....I assume the Met Office closes at night in JER as the TAF is only valid for a short period here...normal is 24 hour if continuously manned...) anyway...back to the TAF... Conditions at 7 PM were variable wind direction at a speed of 5 knots, 9 Km visibility (so a slight reduction already) with a few clouds at 200 feet AGL (above ground level) with a 30 percent probability of temporary periods between 9 PM and 4 AM of visibility reducing to 500 meters in Fog that is effectively cloud on the ground and covering quite a bit of the sky (more than half of the sky appears to be covered in low cloud based on the ground). So 30 percent chance of very low visibility in Fog in the wee hours... What is Fog? As mentioned previously...it is effectively ground based cloud. It can form in several ways (see here for details) and what we are likely seeing at Jersey right now is this advection fog or radiation fog (no, not that kind of radiation!)... Advection fog is where the air passing over the water becomes quite warm and humid from the warm water below it (hence the temperature and humidity are passed through advection to the air above) and then when the air 'hits' land (in this case Jersey) and is forced up (what we call 'orographic lift') it is also forced over cooler land (at night when the Sun is not warming it up any longer and the heat has already been released back into the atmosphere so the ground is now colder than the water was) and forced to rise slightly...this combination makes the air cool and saturate causing 'cloud' or fog as it is still ground based...as long as the winds are forcing the air over the land and the water remains warmer than the land this will continue...once the Sun comes up it starts to 'burn' off the fog and heat the land to a temperature higher than the water so stops the mechanism that causes the fog. Radiation fog happens when you get very strong incoming Sunshine that heats up the land and warms up the air also just above the surface so it can hold more moisture (warm air can hold more moisture than cold air) so the air remains fog free during daylight hours but once the Sun goes down...the Earth radiates the heat back to the atmosphere VERY quickly and the air cools down quickly to the point that it becomes saturated and if the air continues to cool then it will form fog...this is why we have a 'dew point' temperature...this dew point indicator is the temperature you would have completely saturated air if you reduced the temperature instantly to that temperature. For example, on a hot Summer day like today you might find the air temperature is 25 degrees C and the dew point is 12 degrees (so you would need to cool the air at that time down to 12 degrees to have saturated air and start to form fog or cloud)...but the same location at night a few hours after the Sun is gone (so around midnight until the Sun comes up again around 5 AM typically) may have reduced the air temperature very quickly down to the dew point and then continue to fall down a few more degrees as the night goes on...so from say 12 degrees air temperature with a dew point of 11 C and then saturate (11 degrees for both temp and dew point) and then continue to drop as the air cools further creating fog as the temperature continues down to say 8 C air temp with 8 C dew point...(again all as examples). You also need to have calm wind conditions or very light winds as any turbulence or air flow will cause the air to mix and therefore to not be saturated or cool off as quickly...Once the Sun comes back out the air starts to mix and the Sun starts to heat the air to allow it to hold more moisture before becoming saturated and the fog slowly dissipates...until the next evening if the conditions remain the same (such as High Pressure system that has been over an area for a week or so...which keeps cloud away and so allows the very quick cooling at night from such warm saturated daytime conditions. As a system breaks down the high pressure and starts to move in (with wind or cloud, cooler air, etc...) it changes the conditions and therefore the fog doesn't form at night. It looks like the low pressure system over the Bay of Biscay further weakens the high pressure over Scandinavia we will change the conditions enough that the radiation fog and local advection fog will stop. This is also why after a nice week or two of very nice sunny conditions over the UK we start to see more low mist and dew on the grass and some low fog in the fields as well as more haze on the horizon as time progresses until a strong system comes in and breaks down the air mass that created the radiation fog conditions at night... So really a case of too much of a good thing is a bad thing... Should really only be one more day of the fog in the early morning at Jersey from the looks of things and then the systems will have broken the high pressure and start to change the air mass and conditions over Jersey so that it may not be as Sunny but at least it won't be as foggy! Let's see if those low pressures have it in them...:) Hope this was of interest and relevant, especially to those that may be trying to fly to JER from LGW tomorrow or the day after. |
Gatwick Fog
So Gatwick is also fogged in (from the same Radiative fog process described above) this morning...let's have a look at that:
Latest METAR (Meteorological Report) is: (UPDATED 08:40 UK Time) METAR EGKK 300720Z VRB02KT 1200 R26L/P1500 BR BKN002 13/12 Q1018 Report done at 08:20 local time: still light winds but visibility is now 1200 meters and the Sun is starting to have an effect on the Fog...you can see the 1 degree difference between the temperature and dew point which means the Sun is warming the air enough that it can contain more moisture before becoming saturated and therefore can start to dissipate the fog and cloud. As the Sun gets a bit higher it will start to create some local wind as well and this will help things even more...but I digress...back to the METAR...the RVR instrumentation on 26 Left is stating 1500 meters so this is also seeming to be more homogenous and mixing more...the reduction is now MIST instead of FOG as the air is not as saturated and the visibility is improving beyond the traditional 1 Km FOG range limit...The fog is lifting and turning into Stratus that is covering more than half the sky at 200 feet AGL. Pressure remains 1018 hPa. I have left the previous METAR here as it shows the change...so the Sun, once it comes up...does make a big difference in how quickly Fog gets burned off...As long as it is strong enough (seasonal) and the moisture doesn't just lift to form an overcast layer of Stratus (so the Sun can't get at the ground to burn off the rest...(usually a much longer period of such High pressure...say 3 weeks and each night getting radiative cooling going on...) so nothing that bad today and should only be another hour or so before the conditions improve enough for normal operations. An hour ago: METAR EGKK 300620Z VRB02KT 0450 R26L/1400 FG SCT001 OVC002 12/12 Q1018 So on the 30th at 07:20 local time: winds are light and from variable directions (or we wouldn't have radiation fog) with a visibility of only 450 meters. The RVR instrumentation is stating that on Runway 26 Left the visibility is 1400 meters (so may be patchy). The restriction causing this loss of visibility is from FOG. There is some scattered stratus at 100 feet AGL and then it is overcast at 200 feet AGL (this is the fog lifting slightly and being burned off slowly from the Sun and the air starting to mix but not yet completely burning the fog off yet...) The temperature and dew point are both at 12 degrees so the air is still saturated. Pressure is 1018 hPa. and the TAF for Gatwick: TAF EGKK 300500Z 3006/3112 VRB03KT 4000 BR BKN004 TEMPO 3006/3007 0300 FG BKN001 BECMG 3007/3010 24010KT 9999 NSW SCT040 PROB40 TEMPO 3011/3019 6000 SHRA PROB30 TEMPO 3104/3107 BKN011= The forecast valid for 30 hours from 07:00 today until 13:00 tomorrow: light winds with reduced visibility of 4 Km in MIST (not quite FOG but more humid than HAZE) with mostly cloudy conditions at 400 feet AGL. Temporarily between 7 AM and 8 AM there will be reduced visibility periods of 300 meters in FOG and some Stratus at 100 feet AGL. This will become significantly better between 8 AM and 11 AM today as the winds will start to pick up from the Southwest at 10 knots with no visibility restriction and no significant weather. There will be some (less than half the sky) clouds at 4000 feet AGL and there is a 40 % probability that between 12 noon and 8 PM there will be some 6 Km reductions in showers of rain (from the developing Cumulus that is not mentioned). Finally there is a 30 % probability that temporarily between 5 AM tomorrow until 8 AM tomorrow there could be more than half the sky covered in low cloud at 1100 feet AGL. So today seems to be the last of the radiation fog for Gatters as well but this will depend on the low pressure breaking down the high that is over the Southwest UK right now...let's wait and see. Hope this helps and is of use. Let's hope the Sun can get the fog burned off quicker than was anticipated...(and that the maintenance is done in time as well). :) |
I have had dew point explained to me many times. But it has taken 50 years for me to understand it. Got it instantly with your explanation BotB^
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I tried to capture some Virginia clouds, but much of the time they looked like this! :D
http://i319.photobucket.com/albums/m...k/IMG_0050.jpg OK, there were a few, but NILSIG as they say … http://i319.photobucket.com/albums/m...k/P1020842.jpg http://i319.photobucket.com/albums/m...k/P1020846.jpg |
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Originally Posted by RedVee
(Post 18665419)
How clever - a bear shaped cloud ;)
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Originally Posted by RedVee
(Post 18665419)
How clever - a bear shaped cloud ;)
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Originally Posted by Globalist
(Post 18665612)
http://www.doobybrain.com/2008/01/24...ways-terminal/ |
Originally Posted by T8191
(Post 18665648)
Globalist :) |
Originally Posted by Globalist
(Post 18665669)
… been struggling to learn how to include pictures via my iPad ...
Now, after 3 weeks of iPad, I keep trying to swipe the screen on the iMac :D :D |
Thanks to those that have posted about the BA Cloud sculpture...:)
It is very aptly named, as a cloud is in perpetual state of change...and the moving disks do represent this constant change (albeit a bit too uniform compared to the clouds in the atmosphere)...so is relevant and I have to admit to staring at it a few times when going up or down the escalators at T5 :D Now if they could only get a sculpture that also changes in size as well as having the disks changing...then they would be on to something! ;) |
Originally Posted by BotB
(Post 18665689)
Thanks to those that have posted about the BA Cloud sculpture...:)
It is very aptly named, as a cloud is in perpetual state of change...and the moving disks do represent this constant change (albeit a bit too uniform compared to the clouds in the atmosphere)...so is relevant and I have to admit to staring at it a few times when going up or down the escalators at T5 :D Now if they could only get a sculpture that also changes in size as well as having the disks changing...then they would be on to something! ;) |
Originally Posted by T8191
(Post 18665692)
Extrapolating your version of reality, the BA Cloud could then generate precipitation … selectively, of course, and only on those who designed and/or permitted the convoluted access route to the Lounges [CCR exempt, of course]
Actually, like your thought...all they would really need to do is have sections that slide and then little electrical cords running down with a few disks hanging between two vertical lines...these disks could then rotate based on magnetic force changes to indicate precipitation falling from the sky as the cloud grows larger vertically from sections that open on top to allow a 'growth' cell expand upward with the same disks... Might be best if I stick to describing the weather...:eek: |
Originally Posted by BotB
(Post 18665689)
Thanks to those that have posted about the BA Cloud sculpture...:)
It is very aptly named, as a cloud is in perpetual state of change...and the moving disks do represent this constant change (albeit a bit too uniform compared to the clouds in the atmosphere)...so is relevant and I have to admit to staring at it a few times when going up or down the escalators at T5 :D If you want a change structure, maybe BA can get a fog machine? :) |
Incidentally, Cloud Leader, I tried to add Cloud Club to my sig block. I find I am space limited, due to the long MUCCI titles awarded by Her PUCCI-ness. I'm not deleting or modifying those - I'm scared of hairbrushes ;)
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Originally Posted by T8191
(Post 18665844)
Incidentally, Cloud Leader, I tried to add Cloud Club to my sig block. I find I am space limited, due to the long MUCCI titles awarded by Her PUCCI-ness. I'm not deleting or modifying those - I'm scared of hairbrushes ;)
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Originally Posted by BotB
(Post 18665869)
:D No problem, you might still put something on your profile page...such as where you can list interests? We'll just call you the hidden T-Cloud. :)
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Originally Posted by T8191
(Post 18650952)
Originally Posted by BingBongBoy
(Post 18648877)
There are a few ways that these infant clouds just starting life could have come into being...however, what is most likely is: We have a flow of air from bottom left to upper right and this very warm and very moist air (from being heated by both Sun and warm tropical waters) which can hold more moisture and is being fed as much as it can take by the warm ocean...then is effectively almost cloud already...so all it takes is a very small rise in some landscape such as these Islands to cause the already very moist air to become saturated and start forming cloud...I would guess that this is additionally fuelled by the natural convection caused by a late evening time frame...(as the ocean becomes warmer than the land once the Sun is not as strong in the evening and then the breeze starts to blow out towards the water (which would hold the temperature much longer than land) and then rise which then comes back down over the land as cool air to be warmed up again as it moves back out towards the water...This cloud that was created by just moving up over the very small incline of that line of islands then gets additional fuel to grow a bit more and starts to create the next line of clouds that move on to give showers elsewhere later on...You can almost see the process happening as you see the smaller 'line' of barely there smaller white clouds to the right of the line of Islands which are nearly equally spaced distance to the more developed ones further to the upper right...just as waves build and develop so do the clouds! So this orographic lift is the mechanism to create the cloud here as it is in the UK (so is exactly the same as in the UK, except here the air is much warmer and holds more moisture so forms cloud earlier and without as much forcing of the air upwards as would be needed in the UK (hope that answers your question T8191?) This is then further fuelled by the land breeze that is likely occurring here in this photo which helps the clouds grow bigger as they move towards the upper right side of the photo...(you notice the line of the clouds at both points following the line of Islands here)...
Originally Posted by LondonAndy
(Post 18654789)
Originally Posted by ColdWalker
(Post 18664868)
I have had dew point explained to me many times. But it has taken 50 years for me to understand it. Got it instantly with your explanation BotB^
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Originally Posted by BotB
(Post 18648668)
I'm curious if there are now any additional weather satellites or new technology being used to derive weather images?
Europe's latest satellites are from the early part of the last decade (Meteosat 2nd Gen and Metop) but they're still amongst the most advanced that's out there. We're also hoping to launch another 2nd gen Meteosat next month and another metop on July. If you're used to the 1st gen then there's a lot of changes - 3 visible channels and 8 thermal. Plus one visible band with higher detail. The thermal channels can give a lot of information about cloud type and location - as well as extra info on things like the amount of water and ozone in the atmosphere. The visible channels help clarify cloud location and are also useful for detecting cloud phase (water or ice). The image you posted is from the first of the visible channels, roughly corresponding to the color red. ...There are also Polar Orbiting NOAA (1000 Km above Earth) satellites that use visual black and white images to provide weather information... Has there been developments in this area since? Care to take over the podium to discuss satellite weather images and the issues with trying to figure out if the temperature indicated is a thick cloud or a high cloud? Other issues? Don't mean to put you on the spot! Just curious and wondering if you wish to add to the discussion? With respect to high clouds/thick clouds: It's much easier to discriminate between them now that we have lots of extra thermal channels. The earth's surface contributes some heat at certain wavelengths, so if we expect to see a certain surface temperature but instead measure something much lower then there's a fair chance it's thick cloud. If we measure something in-between then it could well be high thin cloud. There's a lot of simulations run that model what temperature we should see for certain cloud types, and the visible channels help a lot too - the color of clouds is very different to that of ocean/land so during the day they can be used to help check what's cloud and what's not. But right now the biggest problem is multi-layered clouds. If there's a layer of thin-cirrus above a much thicker cumulus layer than quite often we fail to detect one or the other of them. |
Originally Posted by BotB
(Post 18666191)
So this orographic lift is the mechanism to create the cloud here as it is in the UK (so is exactly the same as in the UK, except here the air is much warmer and holds more moisture so forms cloud earlier and without as much forcing of the air upwards as would be needed in the UK (hope that answers your question T8191?) This is then further fuelled by the land breeze that is likely occurring here in this photo which helps the clouds grow bigger as they move towards the upper right side of the photo...(you notice the line of the clouds at both points following the line of Islands here)…
Originally Posted by BotB
(Post 18666191)
The clouds in this picture are actually ones to be watching...Some TCU in there and potential for some good turbulence and precipitation...but as with many things all a matter of size! Small aircraft (helicopter, cessna) could be at considerable risk going through this but larger planes such as a 747 would be okay.
I assume the thermal lift is generated by the millions of acres of concrete and asphalt in and around DC, which when combined with the moisture from Chesapeake Bay and the larger rivers in the area leads to bumblies having an easy gestation period ;) |
Originally Posted by simonrp84
(Post 18666692)
<snip, although of great personal interest!>
With respect to high clouds/thick clouds: It's much easier to discriminate between them now that we have lots of extra thermal channels. The earth's surface contributes some heat at certain wavelengths, so if we expect to see a certain surface temperature but instead measure something much lower then there's a fair chance it's thick cloud. If we measure something in-between then it could well be high thin cloud. There's a lot of simulations run that model what temperature we should see for certain cloud types, and the visible channels help a lot too - the color of clouds is very different to that of ocean/land so during the day they can be used to help check what's cloud and what's not. But right now the biggest problem is multi-layered clouds. If there's a layer of thin-cirrus above a much thicker cumulus layer than quite often we fail to detect one or the other of them. I follow you on the ability to use the thermal imaging at select bandwidths to help discern the difference between land/water and cloud, especially in warmer conditions or daylight with visible images...what is the concept used when the Earth's surface is cold such as in Winter or particularly when you have snow on the ground? (I can remember nearly going mad trying to figure out sometimes if I was looking at snow on the ground or low stratus...especially in valleys in Winter where inversions would often occur! and ground temperatures were quite cold and constantly frozen) With todays technology...and trying to deal with the multiple layer of cloud issue...have you considered using tephigram plots to provide the potential layers of moisture associated with air masses to help with identifying where multiple layers of cloud may be? (what with the processing times and ability to grab info... it likely has been looked at...but if not...that could help? I am hoping to talk about satellite imagery regarding not only weather (and how it has helped enormously to progress the science and give data coverage where there are no stations) but also about how it is now being used to provide other environmental parameters which is also very good news, maybe you'll be willing to help me out here when I get into a dry spell of clouds :D...Definitely feel free to post away about any aspect of this 'newer' area of technology! ;) I for one would be greatly interested...but of course, I also understand not everyone wishes to discuss work so will leave you alone to come along fro the ride if you wish and correct me if I get things wrong! :) Thanks again, very interesting ^ |
For those not aware, the UK research community has an aircraft that they use to do in flight measurements and is quite fascinating to see what is being done and how it is achieved...
Here is a link to the FAAM site which I hope will be of interest to everyone reading this thread: http://www.faam.ac.uk/ There are a few others worldwide as well and they do provide excellent insight into areas we can't traditionally get measurements to check the forecast models, satellite images, etc... |
Originally Posted by BotB
(Post 18666973)
I am hoping to talk about satellite imagery regarding not only weather (and how it has helped enormously to progress the science and give data coverage where there are no stations) but also about how it is now being used to provide other environmental parameters which is also very good news...
I used to do some research using the ASTER data to identify the lithology of exposed rocks in NW Scotland using spectrometry of light. ASTER was particularly useful as it broke down the wavelengths into the right bands at the right spatial resolution for me for further analysis. I was taken aback how much the salt spray has covered inland near some of the more exposed coasts, and nearly messed up my research. :D The fun part was going out and about in NW Scotland with my own geological map and a hammer, finding my samples were very well correlated with the spectrometry. And kissing some rocks to see if they tasted of salt, but that's another story. :) At the time, there was only one team working on it in Canada, and I was just a mere undergrad at the time with little support except from a cartographic/GIS specialist from another department. |
Originally Posted by henkybaby
(Post 18650995)
https://fbcdn-sphotos-a.akamaihd.net..._5759985_n.jpg
That is just a great photo henkybaby ^ https://fbcdn-sphotos-a.akamaihd.net...69605453_n.jpg I really like the Cirrus in this photo...I am not sure why but you only really tend to see this type of very long, straight, crisp white, hooked cirrus around the equator regions, especially against a brilliant blue sky...Will be an interesting challenge to figure out why! Possibly related to the lack of pollution (relative) and high troposphere heights over the equator allowing clear blue skies and higher height Cirrus which in turn may be colder so the way the sunshine reacts?...(I appreciate this picture may be slightly altered but still you do see the strong contrast just like this sometimes... https://fbcdn-sphotos-a.akamaihd.net...57601977_n.jpg This one may have our first Cirrocumulus clouds on the thead (or very high based Altocumulus castellanus)...you can see the very flat base, horizontally drawn out cloud in the background and it has some vertical 'tufts' showing (almost like little bumps extending upwards but not downwards)...which could be small Cumulus 'castellanus' turrets here...showing instability at the higher levels... https://fbcdn-sphotos-a.akamaihd.net...73572327_n.jpg Nice picture ^ https://fbcdn-sphotos-a.akamaihd.net...03806406_n.jpg Another great example of the Cirrus I mentioned above...really strong 'ribbons' of concentrated ice crystals here...great ^ Hope to see something like this in person sometime! (where was it?) I am guessing somewhere quite dry and arid so again a fairly high troposphere height allowing higher Cirrus heights? https://fbcdn-sphotos-a.akamaihd.net..._6492424_n.jpg A perfect example of a leading edge of a warm front...some high Cirrus above, then a clear line of Cirrostratus coming from right to left (same as the front) with some daytime convection Cumulus below (unrelated to the warm front) nice contrast with the colours here :) https://fbcdn-sphotos-a.akamaihd.net..._7550566_n.jpg A good example of AC undulates. https://fbcdn-sphotos-a.akamaihd.net..._5971277_n.jpg A good example of AC floccus. Also showing how you can have pockets with less vertical extent as well as some pockets with more vertical development (less is nearly transparent cloud, more is effectively the white 'blob' with clear air around it, again indicating that white where the vertical motion is upwards and clear air where the vertical motion is downwards.) https://fbcdn-sphotos-a.akamaihd.net..._1793051_n.jpg And as is sometimes necessary...it all ends in tears...well precipitation in this case...some good daytime convection and what we call an mT air mass... maritime Tropical air mass producing Cumulus development...and later some TCU or possibly CB clouds with good light shows and cooling rain to balance out the energy system! Sorry, got carried away... :) |
Wow, great to see this area really develop...would love to hear more about the development of the technology and where this is going next! (will have to hope to catch up with you sometime over a drink or gently coerce you into it here! I follow you on the ability to use the thermal imaging at select bandwidths to help discern the difference between land/water and cloud, especially in warmer conditions or daylight with visible images...what is the concept used when the Earth's surface is cold such as in Winter or particularly when you have snow on the ground? (I can remember nearly going mad trying to figure out sometimes if I was looking at snow on the ground or low stratus...especially in valleys in Winter where inversions would often occur! and ground temperatures were quite cold and constantly frozen) With todays technology...and trying to deal with the multiple layer of cloud issue...have you considered using tephigram plots to provide the potential layers of moisture associated with air masses to help with identifying where multiple layers of cloud may be? (what with the processing times and ability to grab info... it likely has been looked at...but if not...that could help? |
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@herman ze German.
That is a very unusual picture! LHR with sunshine and fair weather Cu! To be specific cumulus flufia lamius if I'm am not mistaken ;) |
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