Re: Atene, che forno!
Si,ma dal link che hai fornito per l'isola di calore urbana di Atene, č ovvio che l'isola di calore urbana č quasi inesistente in Thiseio. le medie sono esattamente l stesse con 1860 quando Atene era meno di 50.000 inhabitantiOriginariamente Scritto da dedalus27
Cosė, per il periodo 1971-2000 e per le stazioni WMO Atene,Thiseio č il pių caldo posto in Europa durante l'estate, anche se prendiamo in considerazione l'isola di calore urbana in Thiseio!!!
Re: Atene, che forno!
I have set up that table I mentioned, regarding the differences between the urban and the rural stations in Athens.
First, the orginal table:
The stations there are located at different altitudes, so the comparisons can not be too straightforward. Let me adjust the monthly and yearly mean differences in tmin reported in the table by adding the general -6.5°C / 1000 meters altitude difference between stations. I did that only for urban-vs-rural comparisons, but the same would apply for the other comparisons. I put there also the mean between the two comparisons because averaging more data-points performs better in achieving systematic results than using a single data-point most of the times. Systematic results typically are less precise then specific results, but they apply to a broader range of cases and conditions.
What we see is that altitude difference effects in the tmin mean differences exist, but they seem smaller than the sum of all other effects, and among the other effects we have UHI.
What we do not see is that doing the same calculations for other comparisons (rural vs rural, suburban vs suburban) we find residual mean differences not accounted for by altitude differences, and then not all the mean difference between the Athens urban station and the rural stations of Peania and Tatoi may be imputed to urban heat island. That's obvious, because kind of ground, exposure, slope or flat, shadow etc etc have systematic effects on tmin, effects that in some cases may be strong (especially slope vs flat vs concave vs convex ground) and stronger than moderate differences in altitude (see for instance the extreme frost events in sinkholes compared to flat ground or slopes).
The differences between rural-and-rural and those between suburban-and-suburban are however smaller than those between urban and rural, and that is what we expect under UHI hypothesis.
Re: Atene, che forno!
Thank you for your time with Athens.I also see you involve your self with analysis in the most cold city of Italy thread,so I guess you must have a flare for this.
While in theory I agree with the calculations(I mean mathematically they are correct) we have to be extremely careful with the application.Even the Observatory of Athens team have avoided to do so in a sense because of this extremely complex or even unique(?) geomorphology of Athens basin
I am not sure if you have seen this bit over here
Athens basin.jpg
Another important element that they also note is the winds issue...This seems in a way to eradicate the UHI in the higher altitude and this can be particulary true for the case of Thiseio since in Athens we do not have any skyscrapers (because of Greece's extreme seismicity)to block the winds.
Look what they note here for example
winds.jpg
Also I was thinking another interesting question....What happens for example with the warm temperature records?I dont know if you are aware of it but Tatoi and Elefsina were the stations that recorded the 48.0C in 1977.
Is there anyway for us to examine what the value would be should the UHI did not exist?(Mainly for Elefsina) and given that we already know that the UHI in Athens causes a tremendous Tmax decrease....What is your opinion?
EDIT:Do you think it would be beneficial to look at cities that have the same geomorphology like Athens?For example the only city that ''slighly'' resembles the Athens basin in terms of geomorphology is Los Angeles but to a far less complicated level compared to Athens
Re: Atene, che forno!
Oggi, 23 Luglio 2010, temperature massima giornaliera:
Enna e Sigonella 39ēC, Alexandrov-Gaj (Rusia) 39ēC, Mostar (Bosnia) 39ēC.
woitalia Situazione attuale Europa
LUGLIO 2010 Temperature massime giornaliere in Spagna, Italia e Grecia, ordinati in ordine decrescente:
23/07/2010: Enna/Sigonella 39ēC, Cordoba 38ēC, Zante/Lamia/Larissa/Hellinikon 37ēC (Elefsina 36ēC)
22/07/2010: Capo Frasca 38ēC, Malaga 37ēC, Hellinikon 37ēC (Elefsina 36ēC)
21/07/2010: Malaga 37ēC, Sigonella 36ēC, Elefsina 35ēC
20/07/2010: Decimomannu 37ēC, Saragozza 36ēC, Hellenikon 36ēC (Elefsina 35ēC)
19/07/2010: Siviglia 38ēC, Decimomannu 36ēC, Samo 35ēC (Elefsina 34ēC)
18/07/2010: Cordoba 40ēC, Guidonia 38ēC, Lamia 36ēC (Elefsina 35ēC)
17/07/2010: Cordoba/Siviglia 40ēC, Decimomannu 40ēC, Araxos 36ēC (Elefsina 35ēC)
16/07/2010: Amendola 39ēC, Murcia 37ēC, Araxos 37ēC (Elefsina 33ēC)
15/07/2010: Decimomannu 40ēC, Lamia 38ēC (Elefsina 37ēC), Murcia 37ēC
14/07/2010: Murcia 39ēC, Trapani 38ēC, Elefsina 37ēC
13/07/2010: Malaga 38ēC, Alghero 37ēC, Larissa 36ēC (Elefsina 34ēC)
12/07/2010: Cordoba 38ēC, Larissa 36ēC (Elefsina 34ēC), Sigonella 35ēC
11/07/2010: Saragozza 39ēC, Decimomannu 38ēC, Larissa 34ēC (Elefsina 33ēC)
10/07/2010: Cordoba 41ēC, Roma-Urbe 37ēC, Lamia 33ēC (Elefsina 32ēC)
09/07/2010: Saragozza 40ēC, Firenze-Peretola 35ēC, Lamia 33ēC (Elefsina 30ēC)
08/07/2010: Saragozza/Almeria 40ēC, Firenze-Peretola 37ēC, Kalamata 33ēC (Elefsina 29ēC)
07/07/2010: Siviglia 40ēC, Decimomannu 36ēC, Elefsina 35ēC
06/07/2010: Cordoba 40ēC, Larissa 35ēC (Elefsina 33ēC), Decimomannu 34ēC
05/07/2010: Cordoba/Siviglia 41ēC, Amendola 37ēC, Elefsina 35ēC
04/07/2010: Cordoba/Siviglia 40ēC, Decimomannu 37ēC, Lamia 35ēC (Elefsina 34ēC)
03/07/2010: Cordoba 36ēC, Guidonia 35ēC, Elefsina 33ēC
02/07/2010: Cordoba 38ēC, Grosseto 35ēC, Mitilini 34ēC (Elefsina 33ēC)
01/07/2010: Cordoba/Badajoz 39ēC, Grosseto 35ēC, Samo 33ēC (Elefsina 31ēC)
La Grecia non ha ottenuto il primo posto nessun giorno nel mese di luglio:
Spagna: 17 giorni
Italia: 5 giorni
Spagna/Italia (stessa temperatura): 1 giorno
Grecia: 0 giorno
Ultima modifica di dedalus27; 23/07/2010 alle 22:46
Re: Atene, che forno!
I you have reported sentences mentioning UHI eradication and fading away and decresing (close to the sea, they mean) but you are not reporting those about its presence and intensity. Notice that the wind you mention as a potential cause of UHI removal, for a place in a hill with city all around may be a good cause of UHI: wind may lead there heat coming from other parts of the city.
You show the table with the means of the observatory and say that as they did not change much since late 19th century then there is not urban heat island, and argue that at the observatory there is not UHI, when the regression line suggests instead that the temperatures (tmin) measured by that observatory rise with a rate of
tmin = 8.1 + 0.03*population^(1/4)
that is indication of UHI at the observatory. This table shows some estimates of the impact of Athens population (size of city) on athens tmin based on that regression line (temperature measured ad the observatory I suppose).
I find quite surprising that the values are so small. In fact results reported here regarding Palma de Mallorca indicate +2°C at 400.000 population. Athors of the Greek article (Katsoulis and Theoharatos 1985) say about 2-3°C at least. A study in Barcelona reports +3°C.Codice:--------------------------------- population effect* tmin** (units) (°C) (°C) --------------------------------- 50.000 0,45 8,59 100.000 0,53 8,68 500.000 0,80 8,94 1.000.000 0,95 9,09 2.000.000 1,13 9,27 3.000.000 1,25 9,39 4.000.000 1,34 9,49 5.000.000 1,42 9,56 6.000.000 1,48 9,63 --------------------------------- * effect = 0.03*population^(1/4) ** tmin = 8.146 + effect
In my opinion the position of Athens observatory on the top of the hill partially protects it from UHI (just 0.5°C at 100.000 population, just 1°C at 1.000.000 population). The observatory, at contemporary 4 millions population, perhaps has a +1.3/1.4°C urban heat island effect on tmin, that is much less than I would expect for a so large city.
Why dont'y you go for a trip to the Observatory and you get back with some photographs of the station?
Re: Atene, che forno!
Thanks for the hypothetic calculations.But bear in mind that while the authors say 2-3 increase in minimums they stress that it is difficult to be exact because of the extremely complex issues Athens faces.
I you have reported sentences mentioning UHI eradication and fading away and decresing (close to the sea, they mean) but you are not reporting those about its presence and intensity. Notice that the wind you mention as a potential cause of UHI removal, for a place in a hill with city all around may be a good cause of UHI: wind may lead there heat coming from other parts of the city.
You show the table with the means of the observatory and say that as they did not change much since late 19th century then there is not urban heat island, and argue that at the observatory there is not UHI, when the regression line suggests instead that the temperatures (tmin) measured by that observatory rise with a rate of
tmin = 8.1 + 0.03*population^(1/4)
that is indication of UHI at the observatory. This table shows some estimates of the impact of Athens population (size of city) on athens tmin based on that regression line (temperature measured ad the observatory I suppose).
I find quite surprising that the values are so small. In fact results reported here regarding Palma de Mallorca indicate +2°C at 400.000 population. Athors of the Greek article (Katsoulis and Theoharatos 1985) say about 2-3°C at least. A study in Barcelona reports +3°C.Codice:--------------------------------- population effect* tmin** (units) (°C) (°C) --------------------------------- 50.000 0,45 8,59 100.000 0,53 8,68 500.000 0,80 8,94 1.000.000 0,95 9,09 2.000.000 1,13 9,27 3.000.000 1,25 9,39 4.000.000 1,34 9,49 5.000.000 1,42 9,56 6.000.000 1,48 9,63 --------------------------------- * effect = 0.03*population^(1/4) ** tmin = 8.146 + effect
In my opinion the position of Athens observatory on the top of the hill partially protects it from UHI (just 0.5°C at 100.000 population, just 1°C at 1.000.000 population). The observatory, at contemporary 4 millions population, perhaps has a +1.3/1.4°C urban heat island effect on tmin, that is much less than I would expect for a so large city.
Why dont'y you go for a trip to the Observatory and you get back with some photographs of the station?
Besides I am referring to the Observatory and the temperatures they give are astonishing.Look at the similarities of the summer temps!Merely 0.02C change from 1860!
The winds clearly help eradicate the UHI specially in the hill as the authors mention since in Athens we get the famous northerly Meltemi winds.Are you aware of the Meltemi winds?
I think Thiseio is a trully golden station because firstly there is a good chance the UHI is eradicated totally in terms of the averages monthly temperatures and secondly we are talking about the warmest WMO station in Europe in the summer so it does need further investigation
Ultima modifica di mesogeiakos; 24/07/2010 alle 11:02
Re: Atene, che forno!
Si, ma guarda come Atene ancora una volta fa la piu alta Tmed in Europa
Ieri tmax in Atene 36.6 Tmin 28.2!!!
Ancora una volta Atene fare una media di livello di Mar Rosso e la piu alta media in Europa con 32.4 media!!Siviglia ha fatto una media ieri solo di 28.9 secondo AEMET
Ecco i minime veramente insoportabille di Atene ancora una volta
Atene.jpg
Ultima modifica di mesogeiakos; 24/07/2010 alle 11:09
Re: Atene, che forno!
The hypotetic calculations are done not with hypothetical data and hypothetical relations, but based on empircal data measured at that observatory. Data are not from New Caledonia or Kinshasa, they are Atens population and Athens tmin. That is a specific result that applies straightforward to the case of the specific observatory. The population-UHI relation there is extracted from the Observatory data and Athens population. In the range of population covered by observed population, that estimates are descriptive, not estimates. They become estimates in the range of population not covered by empirical observations; but the relation used in estimating values is extracted from empirical Athens data.
Sure that in some parts of Athens it is less than the "at least 2-3°C" and in some parts it is more than "at least 2-3°C", but they estimate "at least 2-3°C". Those empiric (and not hypotetical) results on the observatory indicate the estimates on that table above I reproduce here.
This is the scatterpolot with the interpolation regression lineCodice:--------------------------------- population effect* tmin** (units) (°C) (°C) --------------------------------- 0 0,00 8,18 50.000 0,45 8,59 100.000 0,53 8,68 500.000 0,80 8,94 1.000.000 0,95 9,09 2.000.000 1,13 9,27 3.000.000 1,25 9,39 4.000.000 1,34 9,49 5.000.000 1,42 9,56 6.000.000 1,48 9,63 --------------------------------- * effect = 0.03*population^(1/4) ** tmin = 8.146 + effect
That's Athens, not Calcutta.
Now an argument you seem to like. We have academic publication on peer-review international jurnal about UHI in Athens and at Athens National Observatory estimating 2-3°C urban heat island in Athens il 1985 and showing empircal evidence of 1-2°C UHI at the National Observatory.
(I'm just kidding of course, I have academic education and I know well how it works in that environment; I do not trust academics more than I trust fish sellers at the harbor market)
Ultima modifica di Borat; 24/07/2010 alle 11:25
Re: Atene, che forno!
Υes but regardless if the UHI is even 10C in the minimums what I am stressing and it is crystal clear from the paper is that mean temperature is not affected almost at all and since this is the case Athens,Thiseio is the warmest area in Europe according to WMO stations and that is extremely importantThe hypotetic calculations are done not with hypothetical data and hypothetical relations, but based on empircal data measured at that observatory. Data are not from New Caledonia or Kinshasa, they are Atens population and Athens tmin. That is a specific result that applies straightforward to the case of the specific observatory. The population-UHI relation there is extracted from the Observatory data and Athens population. In the range of population covered by observed population, that estimates are descriptive, not estimates. They become estimates in the range of population not covered by empirical observations; but the relation used in estimating values is extracted from empirical Athens data.
Sure that in some parts of Athens it is less than the "at least 2-3°C" and in some parts it is more than "at least 2-3°C", but they estimate "at least 2-3°C". Those empiric (and not hypotetical) results on the observatory indicate the estimates on that table above I reproduce here.
This is the scatterpolot with the interpolation regression lineCodice:--------------------------------- population effect* tmin** (units) (°C) (°C) --------------------------------- 0 0,00 8,18 50.000 0,45 8,59 100.000 0,53 8,68 500.000 0,80 8,94 1.000.000 0,95 9,09 2.000.000 1,13 9,27 3.000.000 1,25 9,39 4.000.000 1,34 9,49 5.000.000 1,42 9,56 6.000.000 1,48 9,63 --------------------------------- * effect = 0.03*population^(1/4) ** tmin = 8.146 + effect
Immagine
That's Athens, not Calcutta.
Now an argument you seem to like. We have academic publication on peer-review international jurnal about UHI in Athens and at Athens National Observatory estimating 2-3°C urban heat island in Athens il 1985 and showing empircal evidence of 1-2°C UHI at the National Observatory.
(I'm just kidding of course, I have academic education and I know well how it works in that environment; I do not trust academics more than I trust fish sellers at the harbor market)
Let us not go in to circles.By retaining an average of about 1860 era the argument that Athens is the warmest city in Europe in the summer based at least from the oldest dataset of Greece and the most historic meteorological station of the country seems much more valid now.
Re: Atene, che forno!
The Katsoulis and Theoharatos (1985) article describes into detail how the National Athens Observatory mean temperatures are computed. This method is not averaging 3 hours interval observations, but instead the mean of 5 daily observations:
1) tmin
2) tmax
3) temperature at 8.00
4) temperature at 14.00
5) temperature at 20.00
so it is the mean of 3 observations 6 hours spaced, tmin and tmax. Note that there is not a 2.00 am observations, so the day-time observations are more than the night-time observations, and this will lead to a mean temperature estimate inflation of course, as night is very often cooler than day.
I have tried to apply this method to my 2008 data in order to compare its results with the NOAA method corresponding to the calculation of (tmin+tmax) / 2.
In the table below I show the monthly and yearly mean difference between my integral 5 minutes interval mean (integration method), my NOAA method mean given by (tmin+tmax)/2 ("extremes"), and the method used in the Athens Observatory ("Greek")
My conditions for 2008 are Oregon WMR 968 with Davis passive radiation shield.Codice:Differences between two means estimation methods and integration method. Year 2008. ------------------------------- Mean calculation method ------------------- Month Extremes “Greek” ------------------------------- 1 0,4 0,3 2 0,9 0,7 3 0,4 0,4 4 0,5 0,7 5 0,5 0,8 6 0,9 0,9 7 0,8 1,0 8 0,6 0,8 9 1,0 0,9 10 0,7 0,9 11 0,5 0,3 12 0,6 0,4 ------------------------------- Year 2008 0,6 0,7 -------------------------------
Results are that this "Greek" method (with my geographic, orographic and climatic conditions) perform almost exactly as the simple NOAA method or averaging daily tmin and tmax. Hence the Athens Observatory means should not be compared to integral means (as they are inflated next to them) but to the NOAA (tmin+tmax)/2 method means. So when you compare Thiseio with stations in Tutiempo, check the number of samples in Tutiempo because it often reports means that approximate far better an integration method mean.
Of course I am quite far away from Athens and the results here can be not applicable there. I can download the 5 minutes data from an amateur station in Athens and repeat calculations using its data, so different conditions are ruled out and results apply to Athens straight. If I find a station in Wunderground from Athens and I find photos of the station showing it is installed at least reasonably, I'll proceed.
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