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Dublin Airport's micro climate!

  • 09-03-2010 7:54pm
    #1
    Registered Users Posts: 1,035 ✭✭✭


    Does anyone else think that Dublin Airport seems to experience its own little micro climate sometimes?

    Take last night for example. According to Met Éireann, the temperature dropped to a bone-chilling -7.3c at the station, almost colder than anything experienced during the 'Big Freeze' and several degrees colder than any other station recorded last night, even Casement, which is only a few miles away. In fact, Casement recorded a low of 'only' -2.8c. Indeed, for the past few nights the overnight low in Dublin Airport has often been the coldest out of any location. I would have expected that the effects of the Irish sea would have meant that the coldest locations would have been far more inland or at least more northern.

    I remember the same thing happened last year when we got some really good weather around the end of May. On many nights the overnight low recorded at the airport then was often by far the coldest of all the locations monitored on the Met site.

    Anyone any thoughts or explanations?


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Comments

  • Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    compsys wrote: »
    Does anyone else think that Dublin Airport seems to experience its own little micro climate sometimes?

    Take last night for example. According to Met Éireann, the temperature dropped to a bone-chilling -7.3c at the station, almost colder than anything experienced during the 'Big Freeze' and several degrees colder than any other station recorded last night, even Casement, which is only a few miles away. In fact, Casement recorded a low of 'only' -2.8c. Indeed, for the past few nights the overnight low in Dublin Airport has often been the coldest out of any location. I would have expected that the effects of the Irish sea would have meant that the coldest locations would have been far more inland or at least more northern.

    I remember the same thing happened last year when we got some really good weather around the end of May. On many nights the overnight low recorded at the airport then was often by far the coldest of all the locations monitored on the Met site.

    Anyone any thoughts or explanations?

    A good observation Comp. I noticed the same thing myself over the last few days. Coastal Dublin hardly fell to freezing levels, Casement as you say down to a modest -2.8c, yet at the Airport we had temps down to -7c. That seems a huge difference over such a minute area to be honest. I can't give any explanations as to why, but something seems to be not right about it.


  • Moderators, Science, Health & Environment Moderators Posts: 7,144 Mod ✭✭✭✭pistolpetes11


    compsys wrote: »
    Does anyone else think that Dublin Airport seems to experience its own little micro climate sometimes?

    Take last night for example. According to Met Éireann, the temperature dropped to a bone-chilling -7.3c at the station, almost colder than anything experienced during the 'Big Freeze' and several degrees colder than any other station recorded last night, even Casement, which is only a few miles away. In fact, Casement recorded a low of 'only' -2.8c. Indeed, for the past few nights the overnight low in Dublin Airport has often been the coldest out of any location. I would have expected that the effects of the Irish sea would have meant that the coldest locations would have been far more inland or at least more northern.

    I remember the same thing happened last year when we got some really good weather around the end of May. On many nights the overnight low recorded at the airport then was often by far the coldest of all the locations monitored on the Met site.

    Anyone any thoughts or explanations?

    In Newbridge we got down to -6.7 last night (well 5.58am) and casement is usually near enough in temp surprised at the variance myself , The DP's have been something of note also , with a -12.8 recorded yesterday and today was the 3rd day it has not risen above 0, at the moment its -3.9c (DP)


  • Closed Accounts Posts: 873 ✭✭✭InKonspikuou2


    I've noticed a lot airports around the world have microclimates.


  • Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    I seem to remember someone on here before ( I think Mothman, but I could be wrong) saying that the weather station at Dublin Airport was moved to a much cooler area over the last 10 years or so. I do not claim to know the geography of the area that well, but how cool would the airport be compared to nearby areas? It's a tricky one.


  • Registered Users Posts: 14,317 ✭✭✭✭M.T. Cranium


    I notice on the google earth map that the land around the airport is rural and very flat for quite a distance, so in that environment the air could radiate more efficiently than at some other places on a calm clear night. I also noticed that the runways seem to be painted white there. This would add to radiative cooling locally. I am assuming the weather station is located away from the terminal and the control tower but with urban heat islands, there is always a very sharp boundary -- I have done some mobile temperature surveys and at the very edge of a built-up area, there is often a drop of 3 to 5 C degrees on a calm clear night, over the space of less than a hundred metres.

    Oddly enough, my version of google earth has a wikipedia link for Chechnya on the grounds of Dublin airport. I wonder if anyone else sees that link? :confused:


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  • Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    I know those areas pretty well. The Dublin met station was moved about 3 years ago, and is now located about 2.5kms further away from the terminal, near the approach end of Runway 10, and "way out in the country"! The old location was much nearer to the terminal, just north of the Bravo taxiways. The old site has now been converted into a paved aircraft parking area. The new site is fully grassed, and around 300m from the nearest large paved taxiway. The ground is relatively flat, so cold sinking is probably not an factor. It's slightly higher (1 or 2m) than the level of the nearby R108 road, which is also a great spot to see the station from.

    107192.jpg

    107193.jpg


    The Casement station is located on the southern end of the field, on very slightly sloping ground, so cold air may drain away easier than at Dublin.


  • Closed Accounts Posts: 6,498 ✭✭✭Mothman


    It's moved again??
    Before that it was moved in May 1994. Not sure where it was before that, but I seem to remember soemone pointing out to me that it was near the main terminal. The multi storey carpark has been constructed since.
    As for reasons for very low temperatures, I've recorded equivalent temperatures (-6.4C & -12C on grass) and I'm 1.6k from the sea. The dry ground is enhancing the radiative loss of heat. Note that wind speed readings are at 10m height, so 5 knots at that heights could be calm at screen level meaning no mixing of air and allowing it to cool.


  • Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    Mothman wrote: »
    It's moved again??
    Before that it was moved in May 1994. Not sure where it was before that, but I seem to remember soemone pointing out to me that it was near the main terminal. The multi storey carpark has been constructed since.
    As for reasons for very low temperatures, I've recorded equivalent temperatures (-6.4C & -12C on grass) and I'm 1.6k from the sea. The dry ground is enhancing the radiative loss of heat. Note that wind speed readings are at 10m height, so 5 knots at that heights could be calm at screen level meaning no mixing of air and allowing it to cool.

    Isn't that the case though for much of country. I would have thought that Casement, being just that little less exposed to the Irish Sea, would naturally record a lower, or at least similar temp, despite being on a very slight incline? Casement regularly records lower than the Airport at this time of the year, and can often have the lowest nationwide values, so isn't it unusual that Dublin Airport would have recorded temps of almost 5.0c cooler?, or to put it another way, isn't it unusual that Casement would be 5.0c warmer under the very same conditions and only a few miles apart.


  • Closed Accounts Posts: 6,498 ✭✭✭Mothman


    It is a large difference and unusual and I don't know nor even guess a plausibale answer, but there must be sound reasonings. Its what make this so facinating!

    Having seen my own figures, I'm not surprised at the low temp at Dublin AP, its the relatively high temp at Casment is more puzzling to me.

    The type of soil can have a bearing with light soild cooling down much more. If the Dublin AP site is in a slight hollow (as I've heard) then perhaps this was the difference on the night. The airport is quite exposed negating the effect of the hollow all the time bar the very odd time, perhaps this night being one.

    The grass temp was lower in Casement close to 10C lower than air temp, a huge difference.


  • Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    Mothman wrote: »
    Having seen my own figures, I'm not surprised at the low temp at Dublin AP, its the relatively high temp at Casment is more puzzling to me.

    Me too! :cool: most areas in the country got -5.0c at least, so Casement's value certainly was a shocker. Even Malin head got down to -2.7c on the same night, although the south coast seems to have got off more lightly.


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  • Registered Users Posts: 1,035 ✭✭✭compsys


    10pm, 3c at Dublin Airport
    11pm, -4!

    That's a temperature drop of 7 degrees within the space of an hour! A bit unusual this late in the night, no? Perhaps if it had occurred just between the hours of sunset and night you could comprehend it, but at 10pm? It almost deserves a thread of its own!

    Deffo something strange goin' on in Dublin Airport!


  • Moderators, Science, Health & Environment Moderators Posts: 7,144 Mod ✭✭✭✭pistolpetes11


    Casement is -3 and Saggart is -4.2

    M50 blanch is 0.5 ,

    Some strange readings alrite, would an hour be enough for a cold air to set in ?


  • Registered Users Posts: 919 ✭✭✭n0brain3r


    compsys wrote: »
    10pm, 3c at Dublin Airport

    11pm, -4!



    That's a temperature drop of 7 degrees within the space of an hour! A bit unusual this late in the night, no? Perhaps if it had occurred just between the hours of sunset and night you could comprehend it, but at 10pm? It almost deserves a thread of its own!



    Deffo something strange goin' on in Dublin Airport!




    I've been watching this too maybe the taxi drivers created their own warm front leaving their engines running during the protest and now have gone home;) Am nearly sure Casement dropped from 0 to -3 in the same time dunno if it means anything maybe some else can confirm?


  • Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    Casement is temp -3/ DP -5 at 23Z. I don't know what it was at 22Z.

    Here are the last 3 hours at Dublin, showing a 5 and 4 degree drop in temp and dewpoint, respectively, in 30 minutes. Without being actually out there to see what's going on then I've no idea. Could it be frost formation on the radiation shield, causing cooling due to latent heat of fusion? Anyone live local? Head down there with a torch and report back! :D

    [FONT=Monospace,Courier]EIDW 092330Z 34002KT CAVOK M04/M04 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 092300Z 35002KT CAVOK M04/M04 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 092230Z 34003KT CAVOK M03/M04 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 092200Z 36003KT CAVOK 02/M00 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 092130Z 36003KT 9999 FEW022 01/M00 Q1034 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 092100Z VRB03KT 9999 FEW022 00/M01 Q1033 NOSIG[/FONT]


  • Registered Users Posts: 1,060 ✭✭✭xper


    Obvious related question: how often are official weather station's instruments calibrated and/or checked for faults? Any redundancy/backup/cross-reference instruments?

    I'd noticed the same Dublin airport nocturnal fridge effect over the last week. I would suppose at this stage the operators of the station had noticed too and would have checked for and corrected any problem if they suspected such.

    FWIW: Casement airport altitude is 319ft, Dublin is 242ft asl.

    - Xper


  • Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    Screen grab of IWN temp map showing current temps in the Dublin area:

    107212.jpg

    The airport's figure of -4c looks quite plausible when compared to other values being recorded at nearby stations, but that drop of 7c in one hour at the airport as mentioned by others just does not sit right with me.


  • Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    n0brain3r wrote: »
    I've been watching this too maybe the taxi drivers created their own warm front leaving their engines running during the protest and now have gone home

    Indeed, much cheese burger induced flatulence could have caused the temp to stay up earlier alright. ;)


  • Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    I may have a reason for the sudden drop in temperature and dewpoint at Dublin. It could be due to a decrease in air traffic around 10pm.

    All planes generate wing-tip vortices as they fly, and these are most pronounced on landing and take off, when flaps are down and speed is low. In windy conditions, these vortices are dissipated pretty quickly, but on near calm conditions (eg. last night) they float to the ground unaffected, and can generate localised turbulence.

    As the station is located at the departure end of Runway 28, planes taking off over it would be generating these vortices, and hence ensuring a mixed boundary layer, with warmer air from above being mixed with cold surface air, limiting frost generation on the grass. But around 10pm, most departures have ceased for the night, and so too have the vortices. This allows rapid cooling of the surface layer, generating frost, which takes water vapour from the air, leading to the drop in dewpoints observed.

    The reverse happened this morning at around 0530am when the first of the departures occurred. From 0500 to 0530am there was a marked increase in temperature and dewpoint, due to the same process as above.

    [FONT=Monospace,Courier]EIDW 100730Z 36005KT 9999 FEW017 BKN042 01/00 Q1032 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100700Z VRB03KT 9999 FEW017 SCT038 BKN043 M00/M00 Q1032 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100630Z VRB02KT 9999 FEW017 BKN043 M00/M00 Q1032 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100600Z 35004KT 9999 FEW017 BKN043 M00/M00 Q1032 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100530Z 35004KT 9999 FEW017 BKN042 M00/M00 Q1032 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100500Z 35003KT 9999 SCT043 M02/M03 Q1032 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100430Z 35003KT 9999 SCT042 M03/M03 Q1032 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100400Z 36004KT 9999 BKN045 M05/M05 Q1032 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100330Z 01004KT 9999 SCT045 M05/M05 Q1032 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100300Z 36003KT 9999 SCT045 M04/M04 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100230Z 34002KT 9999 SCT045 M02/M03 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100200Z 01003KT CAVOK M03/M04 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100130Z 36004KT CAVOK M04/M04 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100100Z 34002KT CAVOK M03/M03 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100030Z 33003KT CAVOK M01/M02 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 100000Z 36003KT CAVOK M02/M02 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 092330Z 34002KT CAVOK M04/M04 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 092300Z 35002KT CAVOK M04/M04 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 092230Z 34003KT CAVOK M03/M04 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 092200Z 36003KT CAVOK 02/M00 Q1033 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 092130Z 36003KT 9999 FEW022 01/M00 Q1034 NOSIG[/FONT]
    [FONT=Monospace,Courier]EIDW 092100Z VRB03KT 9999 FEW022 00/M01 Q1033 NOSIG[/FONT]


  • Registered Users Posts: 8,504 ✭✭✭Speak Now


    If this is correct Su Campu them met Eireann need to stop using the station....remember the reason they gave for not using the Kilkenny station anymore!


  • Closed Accounts Posts: 6,498 ✭✭✭Mothman


    I had a rise in temperature at 5am this morning due to cloud cover moving over.

    And if there is something in the wing tip vortice theory then why did the temp drop to -1.3C at 8pm before rising again to +2.6C at 10pm?


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  • Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    Thinking about it a bit more I'm less and less convinced about the vortex theory, there's usually a simple explanation! :rolleyes:

    Looking at the METARs I posted above, the temperature drops and rises coincide with the dissipation and appearance, respectively, of low level clouds (went from Scattered at 2200ft to clear at 10pm, and from Scattered 4300ft to Few at 1700ft at 530am).

    So I think we can put it down to radiative effects.


  • Registered Users Posts: 8,913 ✭✭✭Danno


    PHEW! I'd hate to see them having to close the station. :P


  • Registered Users Posts: 1,009 ✭✭✭Neddyusa


    Been driving around these areas of rural north Dublin/South Meath these past few frosty nights and noticed this huge variation in temps over short distances. Temp was going up and down like a yoyo between +1 and -5 over the space of less than half a mile and all in rural areas. I was observing only the thermometer on the car which I know may not be greatly accurate but from past experience I know it not to be too sensitive and have never seen it to fluctuate so much like that.
    Something about these current frosty nights that the low temperatures are much more localised than during the frosts of 'The Big Freeze' ...any explainations? Differing soil types, some of which are retaining the heat from the sunny days maybe???


  • Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    With little or no wind, cold pooling is a big factor. The cold air, being denser, accumulates in lower lying areas, so as you're driving along, going upslope a few meters could take you out of one of these cold pools and into the warmer air above.


  • Registered Users Posts: 6,127 ✭✭✭highdef


    Well when I was driving to work on the M50 this morning over the N2, I was glancing towards the city (the views are often nice of the city from this elevated position of almost 100 metres) and could see that there was a definite inversion over the city. The Dublin mountains were about as clear as I've ever seen them and the sky was a deep blue. The snow still very apparent and as it was so clear, the mountains appeared so much closer than normal. However, the lower levels of the Dublin basin were completely covered in a misty haze and it appeared that I was just above this inversion. At this point, I noted the temp being at 4.0c.

    By the time I entered the Phoenix Park at castleknock, the temp was at 3.5. Half way down the park and travelling downhill, I entered the haze that I saw from the M50 and the temperature dropped further. It was 2.0 as I left the park. However, this does happen a lot where the temperature at the lower end of the park can be 2c or more lower than the upper end.

    Anyway, I'm digressing. Is it possible that the inversion level (presuming my observations this morning were of an inversion) has recently been at the approximate height of the weather station at Dublin airport? When I was on the M50 at Finglas this morning, I would have estimated that I was only a couple of dozen metres above the inversion, at most.....purely going by the upper levels of the mist/haze. Also, at this point I would have been not much more than 10 metres or so above the height of the station in Dublin Airport.

    If, hypothetically, the weather station was right at the borderline of the inversion level, could it be possible that slight mixing of the low level air above could be enough to greatly change the temperature? The proximity of the planes taking off and landing could indeed have something to do with it too.

    On a personal note, I was driving down the N32 eastbound a few nights ago. At the start of the N32, it was 4.5. After the first roundabout at Baskin, it dropped to 4.0. Then a few hundred metres later it dropped straight down to 1.0 - I've never seen it drop that much so quickly before. And by the time I got to the Malahide Road, it was back to 3.5 and then 4.5 at home in Baldoyle.


  • Closed Accounts Posts: 4,279 ✭✭✭Su Campu


    If you look at Valentia's 6am sounding this morning you can see the difference a few meters makes.

    107340.JPG


  • Registered Users Posts: 8,913 ✭✭✭Danno


    Thats some difference SC!!! Some incredibly dry air about there - for Valentia!!!


  • Registered Users Posts: 1,035 ✭✭✭compsys


    I see from looking at the Met Éireann site over the past few days that Dublin Airport's mico-climate is back in full force. As was the case in early March, the official lowest observed temperature has been recorded at the station on many of the past few nights.

    Can someone explain though how a coastal area can consistently have one of the lowest day-time AND night-time temps in late spring? I thought coastal areas were supposed to be kept cooler because of the sea during the daytime but then slightly warmer at night?

    At Dublin Airport over the past two weeks or so we've seen certainly the cooler daytime temps in operation due to the sometimes stiff easterly breeze, but we've also seen significantly colder night-time temperatures as well. This has led to a current mean monthly temp at Dublin Airport of over 1 degree below average, despite every other station recording an above average mean temp so far!


  • Registered Users Posts: 1,035 ✭✭✭compsys


    Interesting to see from Met Eiréann's latest monthly statistics that the Dublin Airport station recorded its first above-average mean monthly temperature since November of last year. This means that the station has had six consecutive months of below average temps: a record perhaps?

    However, the mean monthly temperature for June of 14.1 C was 'only' 0.7 degrees above the monthly average for the station, compared to a temperature of 1 - 2 degrees above average for almost every other station in the country. This continues Dublin Airport's unusual trend of being significantly colder than almost any of Met Eireann's other stations, despite having long-term mean temperatures that state it should be one of the milder locations.

    Again, it seems to be the unusually cold night-time temperatures recorded at the station (especially on clear nights with no wind) that are responsible for the cold statistics.


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  • Registered Users Posts: 1,035 ✭✭✭compsys


    Just looking at the stats for June and it really hits home once more how bad a location the 'new' Dublin airport station is in.

    As is usual, the station recorded some extremely low minimum temperatures during the month of June and on many nights was the coldest station in the country.

    DA recorded an average temp of only 12.7 for June, over one degree below average and way below the 13.8 recorded at Phoenix Park, only a few kms away. A difference in monthly temps of over one degree is actually huge, even more so for two stations within practically the same area!

    What annoys me though is that this station tends to be the official station for Dublin, despite its bad location. Most weather apps and sites worldwide seem to refer to it when giving a forecast for Dublin and yet it's giving pretty inaccurate temperatures. Even during the day, because it gets affected by the sea breeze, it gives temps that are usually a fair bit lower than what anyone in the city or in the Western suburbs is experiencing.

    You have to wonder whether Met E should stop using the station altogether. Indeed, the Met E June Monthly Summary seems to suggest they already are. It says: 'Coldest conditions compared to Long-Term Average (LTA) were at Sherkin Island with a mean temperature of 13.1°C, -0.8°C below its June normal'. However, DA's mean temperature was 12.7, or -0.9C below its June LTA so they appear to have excluded DA's temperature stats altogether (and rightly so!)


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