Athens to experience 50°C during the summer/ Greek Ministry of Climate Change

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Nimbostratus
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Ja temos os dados oficiais de temperatura das estaçaos oficiais gregas no mes de abril (climatic bulletin of April):

http://www.hnms.gr/hnms/english/index_html

Em quanto a Atenas, as 4 estaçaos oficiais da cidade tiveram as seguintes temperaturas medias (longitude, latitude, media, maxima, minima)



Mas calculando a temperatura media coa formula de maxima e minima dividida por 2 (como facemos em Espanha e Portugal), as medias sao:

Elefsina 14,70ºC
Tatoi 12,55ºC
Helliniko 15,05ºC
Spata (é o aeroporto de Atenas) 12,4ºC

No mesmo mes de abril, San Pablo (aeroporto de Sevilla) 20,0ºC. Quase 8ºC mais que o aeroporto de Atenas!!!!!!!!!!!!!! :)
O dado oficial de Sevilla-San Pablo: http://www.ogimet.com/cgi-bin/gclimat?mode=1&state=Spa&ind=&ord=REV&verb=no&year=2011&mes=04&months=


Por outra banda, Rodas teve uma media de 16,7ºC, Karpathos 16,7ºC e Herakleio (Creta) 15,4ºC.
No mesmo periodo, segundo os resumos diarios de AEMET, Fuengirola 19,22ºC, San Fernando 18,96ºC, Rincón de la Victoria 20,13ºC.




Abril foi muito mais quente na peninsula iberica que Grecia, mesmo resultado en marzo e fevereiro. E tambem em maio. Estou totalmente certo que ao final do ano, Rincon de la Victoria, será mais quente que toda Grecia, ilhas asiaticas inclusive.
 

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Cirrus
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Ja temos os dados oficiais de temperatura das estaçaos oficiais gregas no mes de abril (climatic bulletin of April):

http://www.hnms.gr/hnms/english/index_html

Em quanto a Atenas, as 4 estaçaos oficiais da cidade tiveram as seguintes temperaturas medias (longitude, latitude, media, maxima, minima)



Mas calculando a temperatura media coa formula de maxima e minima dividida por 2 (como facemos em Espanha e Portugal), as medias sao:

Elefsina 14,70ºC
Tatoi 12,55ºC
Helliniko 15,05ºC
Spata (é o aeroporto de Atenas) 12,4ºC

No mesmo mes de abril, San Pablo (aeroporto de Sevilla) 20,0ºC. Quase 8ºC mais que o aeroporto de Atenas!!!!!!!!!!!!!! :)
O dado oficial de Sevilla-San Pablo: http://www.ogimet.com/cgi-bin/gclimat?mode=1&state=Spa&ind=&ord=REV&verb=no&year=2011&mes=04&months=


That's interesting. Here are the means of Elefsina for April 2011 computed from synops data:

integration method mean: 14.4°C
NOAA mean = (tmin+tmax)/2: 14.3°C
mean tmin = 9.9°C
mean tmax = 18.7°C

There is something I do not understand in how HNMS treats temperature samples. Mean tmax corresponds but mean tmin does not. Next I try to recompute integration mean after collapsing data by day and hour. Maybe this effect depends on imbalance of sampling between night and day. :confused: In my opinion the best thing to do is emailing Sarantopoulos and asking him.
 

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Cirrus
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:huh:
In April sampling was not terrily unbalanced :huh:

Código:
[FONT="Courier New"]------------------------------------------------
         hh        Freq.     Percent        Cum.
------------------------------------------------
          0           58        4,12        4,12
          1           58        4,12        8,24
          2           58        4,12       12,37
          3           59        4,19       16,56
          4           58        4,12       20,68
          5           58        4,12       24,80
          6           59        4,19       29,00
          7           60        4,26       33,26
          8           60        4,26       37,53
          9           60        4,26       41,79
         10           58        4,12       45,91
         11           59        4,19       50,11
         12           59        4,19       54,30
         13           59        4,19       58,49
         14           58        4,12       62,62
         15           58        4,12       66,74
         16           60        4,26       71,00
         17           58        4,12       75,12
         18           57        4,05       79,18
         19           60        4,26       83,44
         20           60        4,26       87,70
         21           59        4,19       91,90
         22           58        4,12       96,02
         23           56        3,98      100,00
------------------------------------------------
      Total        1.407      100,00
------------------------------------------------[/FONT]
 

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Cirrus
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:huh::huh::huh:

Here are the results after averaging the samples by hour.

Código:
[FONT="Courier New"]
   month        tmed      noaa      tmin      tmax
--------------------------------------------------
       1         9,6       9,8       6,2      13,3
       2        10,0       9,8       6,0      13,7
       3        10,7      10,8       7,0      14,7
       4        14,4      14,3      10,1      18,6
       5        19,4      19,4      14,6      24,2
--------------------------------------------------
    Mean        12,8      12,8       8,8      16,9
--------------------------------------------------[/FONT]

(data of May end yesterday afternoon, when I downloaded the synops).

So tmin are means of coolest hour (on average), tmax are means of warmest hours (on average), tmed are means of hourly means and noaa are simple means of warmest and coolest hours. This operation does not reconciliate the results with the HNMS bulletin. I do not understand what they do with their temperature samples. :huh::huh:
They do not use hourly means instead of absolute tmin and tmax, but their tmin are higher than absolute mins extracted from synops.
 

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Nimbostratus
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That's interesting. Here are the means of Elefsina for April 2011 computed from synops data:

integration method mean: 14.4°C
NOAA mean = (tmin+tmax)/2: 14.3°C
mean tmin = 9.9°C
mean tmax = 18.7°C

There is something I do not understand in how HNMS treats temperature samples. Mean tmax corresponds but mean tmin does not. Next I try to recompute integration mean after collapsing data by day and hour. Maybe this effect depends on imbalance of sampling between night and day. :confused: In my opinion the best thing to do is emailing Sarantopoulos and asking him.



Yes, it is strange. It would be interesting to contact with Mr. Sarantopoulos, but we'll see if he responds to your email. I hope you keep us informed!
 

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Cirrus
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Here a scientific article saying that there is motived expectation for increasing extreme events, hot days and warm nights in Athens in the future.

Giannakopoulos C., Hatzai M., Kostopoulou E., McCarty M., Goodess C. (2010). "The impact of climate change and urban heat islands on the occurrence of extreme events in cities. The Athens case". Proc. of the 10th International Conference on Meteorology, Climatology and Atmospheric Physics, Patras, Greece, May 25th–28th, 2010, pp. 745–752.


The article can be retrieved by downlading the Comecap 2010 conference proceedings at http://www.comecap10.upatras.gr/ and then in the next page select "conference proceedings". Notice that it is a huge file (74 mb)

Abstract:
An assessment of the cumulative impacts of urban heat islands, climate change and anthropogenic heat emissions on the occurrence of extreme events in Athens is presented. Towards this aim, novel climate model simulations of HadRM3 model are used, including the sub-grid urban land-surface model MOSES2.2. Experiments are explored both for the present (1971-1990) and future climate (2041-2060) under the A1B emission scenario, including the influence of the urban surface and anthropogenic heat emissions. The frequency of extreme temperatures, the number of hot days and nights, and the UHI magnitude are analysed. It is found that the UHI increases the number of hot nights and days in both present and future climates.


Conclusion:
We have presented an analysis of the influence of the urban land surface and urban anthropogenic heat emissions for the city of Athens. A simple urban surface exchange scheme is found to capture the main meteorological characteristics of a Mediterranean urban heat island, when compared to an analysis of observational data for Athens. Temperature changes in response to an SRES A1B climate change scenario by the 2050s are similar for urban and nonurban surfaces. UHI responds significantly to changes in the anthropogenic heat emissions of a city. The study has shown that elevating this heating from 15Wm-2 to 45Wm-2 (UrbAnthr and Urb3Anthr simulations, respectively) can increase the average UHI by one class. These heat emissions values are probably reasonable at the scale of the regional climate model, but within the core of large cities heat emissions can be orders of magnitude larger than these (Ichinose et al. 1999).
The cumulative impact of climate change and urban heat islands on the frequency of extreme events has been presented. It became evident from this sensitivity study that in order to assess potential risks to people and infrastructure within our cities it is essential to consider the combined role of global warming and local urban warming.



I am just slightly skeptical about the use of the Tanagra station as a rural reference station for the evaluation of the UHI of the NOA station. But 3 authors over 5 are researchers of the National Observatory of Athens, so I assume that they know what they do and they have their reasons for doing so. ;)
 

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Cirrus
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Yes, it is strange. It would be interesting to contact with Mr. Sarantopoulos, but we'll see if he responds to your email. I hope you keep us informed!

I do not think he is replying to me again.

However the issue of the difference between "Greek" means and NOAA means (simple means of minimum and maximum temperatures) goes on, and not only for the NOA station. Something similar happens for the Athens-Hellinikon weather station.
Código:
 Athens Hellinikon, means 1961-1990
[FONT="Courier New"] ---------------------------------------------
[b]            tmax      tmin   tmedgre      tmed[/b]
 ---------------------------------------------
   Jan      13,4       7,0      10,2      10,2
   Feb      13,9       7,3      10,5      10,6
   Mar      15,8       8,6      12,4      12,2
   Apr      19,4      11,7      16,0      15,6
   May      24,0      15,8      20,6      19,9
   Jun      28,5      20,0      25,0      24,3
   Jul      31,6      22,8      27,8      27,2
   Aug      31,4      22,6      27,6      27,0
   Sep      28,2      19,7      24,3      24,0
   Oct      23,0      15,5      19,3      19,3
   Nov      18,9      12,0      15,4      15,5
   Dec      15,2       8,9      12,0      12,1
 ---------------------------------------------
[b]  Mean      21,9      14,3      18,4      18,1[/b]
 ---------------------------------------------
(Source of data ftp://dossier.ogp.noaa.gov/GCOS/WMO-Normals/RA-VI/GR/16716.TXT): [/FONT]
But in this case, NOAA means are lower than the means computed by the use of the Greek formula. This stuff is quite obscure. :huh:
 

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Cirrus
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It is not the first time I investigate this point. I have tried to apply a couple of "Greek" forumulas for mean computation to my data in order to see what happens. I have tested on my 2010 data (5 minute instantaneous samples with passive Davis shield) the differences between NOAA means and integration means (tmed), and two "Greek" methods: 1) means of temperatures measured at 8, 14 and 21h; 2) means of temperatures measured at 8, 14 and 21h plus tmin and tmax, that is the formula used by Katsoulis & Theoharatos in their study about Athens UHI.
Here are the deviations of these means from the NOAA mean, so (tmin+tmax)/2



I had already done this previously, with the use of my 2009 data, and the results were slightly different. However we see that with my climatic conditions the two "Greek" means are reasonably similar to NOAA means (appreciable difference only in May), and they perform all very very poorly compared to the integration method ones: they are junk statistics all the year long but not worse than NOAA means under my climatic conditions. The overestimation compared to integration mean is clear and systematic but not greater for Greek means than for NOAA means.
And this surprises me once again, as the analysis of the HNMS monthly bulletins reveals that their way to compute means quite systematically overestimates the NOAA means; maybe this depends on prevailing Greek climatic conditions, but it can depend also on data construction, measurement technique (shielding, temperature sensors response etc).
 

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Cirrus
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Ja temos os dados oficiais de temperatura das estaçaos oficiais gregas no mes de abril (climatic bulletin of April):

http://www.hnms.gr/hnms/english/index_html

Em quanto a Atenas, as 4 estaçaos oficiais da cidade tiveram as seguintes temperaturas medias (longitude, latitude, media, maxima, minima)



Mas calculando a temperatura media coa formula de maxima e minima dividida por 2 (como facemos em Espanha e Portugal), as medias sao:

Elefsina 14,70ºC
Tatoi 12,55ºC
Helliniko 15,05ºC
Spata (é o aeroporto de Atenas) 12,4ºC

No mesmo mes de abril, San Pablo (aeroporto de Sevilla) 20,0ºC. Quase 8ºC mais que o aeroporto de Atenas!!!!!!!!!!!!!! :)
O dado oficial de Sevilla-San Pablo: http://www.ogimet.com/cgi-bin/gclimat?mode=1&state=Spa&ind=&ord=REV&verb=no&year=2011&mes=04&months=


Por outra banda, Rodas teve uma media de 16,7ºC, Karpathos 16,7ºC e Herakleio (Creta) 15,4ºC.
No mesmo periodo, segundo os resumos diarios de AEMET, Fuengirola 19,22ºC, San Fernando 18,96ºC, Rincón de la Victoria 20,13ºC.




Abril foi muito mais quente na peninsula iberica que Grecia, mesmo resultado en marzo e fevereiro. E tambem em maio. Estou totalmente certo que ao final do ano, Rincon de la Victoria, será mais quente que toda Grecia, ilhas asiaticas inclusive.

This is also interesting. Take a look of the mean of the Meteoclub ham station at Nea Filadelfia for April 2011:
http://www.wunderground.com/weather...D=IU0391U03&year=2011&month=4&graphspan=month

14.5°C.

Exactly as Kassomenos & Katsoulis (2006) said. Elefsina records most of the time temperatures higher than the urban areas of Athens. Unfortunately the ham station at Aspropyrgos (next to Elefsina) does not report and its website is down. It would be a very interesting comparison.
 

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Super Célula
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This is also interesting. Take a look of the mean of the Meteoclub ham station at Nea Filadelfia for April 2011:
http://www.wunderground.com/weather...D=IU0391U03&year=2011&month=4&graphspan=month

14.5°C.

Exactly as Kassomenos & Katsoulis (2006) said. Elefsina records most of the time temperatures higher than the urban areas of Athens. Unfortunately the ham station at Aspropyrgos (next to Elefsina) does not report and its website is down. It would be a very interesting comparison.

Em Portugal o Instituto de Meteorologia utiliza a média composta.
 

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Cirrus
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Extremely interesting article about temperature distributions inside Athens: http://kkccyu.cjb.net/science/article/pii/S2210670710000041

Full-text pdf: http://kkccyu.cjb.net/science?_ob=M...2a53c2845b6edb133c040b48b7b&ie=/sdarticle.pdf

(not sure that the full-text link is static, just clic PDF (2762 K) in the previous page).
Cross and finger, it seems that the warmest part of Athens is Peristeri in average summer temperatures and in average tmax mean temperatures (notice the +40°C in July 2009 and +40.6°C in August 2009 means).

So now we know where Athens' +50°C will most likely fall: in Peristeri. Very fortunately there are some ham stations in Peristeri, so we will have the pleasure to see that +50°C in realtime.
The maps of temperatures distributions the authors present are very very interesting.
Very correctly the authors say that not all that heat is UHI, they acknowledge a role of orography in favouring the development of intense heat in Athens.
 
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