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Not if you understand the basics of climate genetics… and how they shape and control climate. I’m glad to explain as I find it as interesting as you do:
Mediterranean (Cs) climates character is really shaped by their geographic location between two unlike climate controls: 1) The stable eastern end of the oceanic subtropical anticyclone (H) equatorward…..and 2) the rain-bringing storms/fronts/jets of the middle latitude westerlies poleward.
In summer, a poleward shifting of the sun /circulation belts brings Mediterranean climates under the control of the stable eastern end of the subtropical highs (H). So in summer Mediterranean climates see subsiding air, temperature inversions, and a dearth of atmospheric disturbances. This gives Mediterranean climates their classic summer weather - one where solar control and very dry weather dominates.
In winter, when the wind and rainfall belts shift to their southernmost limits, Mediterranean climates largely escape the effects of the subtropical highs, and instead come under the effects of the westerlies and their rain brings disturbances (storms/fronts/jets)…hence the increased winter rainfall and often cool(ish) temperatures of the Mediterranean winter.
In the case of Florence (43 North) it doesn't share the same climate genetics as typical Mediterranean climates since it is geographically positioned (like several parts of Cs Europe) at the very edge (high latitude) of where Mediterranean climate controls are genetically found. Instead, the climate genetics of the middle latitudes (i.e. westerlies with their rain bringing disturbances, CAA...etc ) dominate Florence to a greater extent than the typical eastern side subtropical climate controls ( strong subsidence, dearth of weather disturbances, strong solar control at the time of high sun….etc) found in typical Mediterranean climates .
Despite what people think (and I have gently tired to point this out before), even though southern Europe is the region where Mediterranean climates where given their name ….it is really the Near East and North African sectors of the rim lands of the Mediterranean Sea that exhibit Cs/ Mediterranean climate in it’s pure development. Areas on the northern rim lands of the Mediterranean Sea connected to Europe are less true to type and more transitional in nature.
I agree with your last point, regarding the eastern Mediterranean and North Africa, they do seem to exhibit climates which are more stereotypically "Mediterranean" than the sea's northern shores.
Florence has modestly nice climate…however it is not really close to a Med (Cs) climate ….
The working definition for Cs or Mediterranean climate is at least 3 times as much rainfall in the winter half of the year as in the summer half….OR driest summer month receives less than 1.2 inches (3 cm) of rainfall.
This is incorrect, the definition is that the wettest month in winter has 3 times as much as the driest month in summer. Florence does just qualify under this definition.
I doubt the UHI alone could account for an almost 10C difference between the 1956 and 1879 records. Besides, the area around Montsouris was hardly the countryside even in the 19th century. That particular day in December 1879, the overnight low was supposedly -23.9C but the maximum was as high as -6.7C, a difference of about 17C. In fact if you look at the data for that month there are numerous days with such big diurnal ranges, which is surprising given that that month was also supposedly very snowy (and presumably cloudy). I suspect there was a problem with thermometer calibration or exposure. Apparently, the practice of placing thermometers 1.5 metres above ground and inside a screen did not become standard practice until the 1920s. If this was the case, this could easily have distorted readings when there is a lot of snow on the ground. This is why pre-20th century records should be treated cautiously.
As for Florence, the almost 10C difference between the airport and city centre (and also nearby towns) is also quite suspect, unless there is something about the airport's location that makes it prone to low temperatures.
Keep in mind that winters all over Europe and the US were generally colder in the 19th century. I find the reading suspect as well, but once-in-a-lifetime temps may occur. I don't know about France, but here the readings were sometimes rounded up or down a half degree. It wasn't so accurate then, and neither were the equipment. A low of -23.9C and a high of -6.7C is from my experience completely possible. Not perhaps normal, but possible. We had one such day and night this January.
The Finnish Meteorological Institute swears that the old Finnish records are accurate, with readings from two thermometers, and at least since 1900 they have been inside a screen and above the ground. I don't know what equipment the French used, but probably not poorer than the Finns. I wouldn't dismiss 19th century readings, but as you said, treated cautiously.
On the actual subject, Florence is notorious for both heat and cold. June-July of 2010 recorded 29 consecutive days above 30C, often 35C, and I find it a bit excessive. What makes it worse is that often temps didn't go below 20C during the night.
According to meteociel, January 1985 had two readings below -20C, so they are probably correct. The airport is just a few miles from the downtown, so I wouldn't suspect a frost hollow.
A friend of mine worked a winter in nearby Pisa, and he said that frost was fairly common, and as the houses were poorly insulated, it felt like hell. One crappy radiator in the living room, and you had to keep your coat on even inside. Ice days seem very rare, but nights can go below freezing for several nights in a row.
I don't know what to give this climate. I'm tempted for a B, but the summer are too much and the winters are just plain boring. C+
The few days I spent in Florence, it was very smoggy. I wonder if it's a common problem there or if it was bad luck. The location in a valley probably doesn't help.
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Originally Posted by Superluminal
I doubt the UHI alone could account for an almost 10C difference between the 1956 and 1879 records.
Why would it account for all the difference? What if 1879 was actually colder? No scenes like this in 1956, far from it.
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Besides, the area around Montsouris was hardly the countryside even in the 19th century.
It was definitely not countryside, but the city was still a different beast. Here are two population maps, from 1876 and 1954, the red dot is the location of the weather station. It would be dishonest to affirm that the local climate hadn't warmed compared to the surround contryside in that timeframe.
Quote:
That particular day in December 1879, the overnight low was supposedly -23.9C but the maximum was as high as -6.7C, a difference of about 17C. In fact if you look at the data for that month there are numerous days with such big diurnal ranges, which is surprising given that that month was also supposedly very snowy (and presumably cloudy).
Conditions were similar, snow on the ground and an anticyclone. But in 2009 the layer was a couple inches deep, while it was more than a foot in 1879. Btw, the day after, the low was apparently only -7.5°C, so the "mild" high may have been caused by a temporary warm incursion. Also, that month wasn't very snowy, the layer formed in one snowstorm, followed by settled weather. The average pressure was 1029 hPa, 1034 hPa on that litigiously cold day and no trace precipitation for 18 days in a row.
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I suspect there was a problem with thermometer calibration or exposure. Apparently, the practice of placing thermometers 1.5 metres above ground and inside a screen did not become standard practice until the 1920s. If this was the case, this could easily have distorted readings when there is a lot of snow on the ground. This is why pre-20th century records should be treated cautiously.
As for Florence, the almost 10C difference between the airport and city centre (and also nearby towns) is also quite suspect, unless there is something about the airport's location that makes it prone to low temperatures.
On clear nights with snowy ground, the difference between rural and urban weather stations can be massive. For example, on November 23rd, 2010, Edmonton Mun went down to -27.5°C whereas Edmonton Int'l got to -35.6°C. Edmonton Mun is located in a suburban-like area, the city centre was probably significantly warmer.
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This is incorrect, the definition is that the wettest month in winter has 3 times as much as the driest month in summer. Florence does just qualify under this definition.
I checked the book (An Introduction to Climate – 5th Edition Trewartha and Horn - 1980):
You’re definitely correct: It appears they are one in the same or one is considered an alternative definition.
On page 260 it says; Cs = Dry season in summer of the respective hemisphere. At least three times as much rainfall in the winter half or the year as in the summer half of the year. Driest summer month receives less than 3 cm (1.2 inches).
On page 402 it says Cs = Summer Dry; At least three times as much rainfall in the wettest month of winter as in the driest month of summer*2, the driest month of summer receives less than 3 cm (1.2 in.) of rain. (Bottom of page)*2 = Alternative definition: 70 % or more of the average annual rainfall is received in the winter 6 months.
Florence does just make the Cs definition cut (driest month 1.4 inches/wettest month 4.4 inches). However, using either definition there is still no month that receives less than 1.2 inches of rainfall. So technically,. I’m not sure. I think this another case where the whole climate picture has to be examined. Even if Florence did have one month that had less than 1.2 inches of rainfall, just looking at the amount and rhythms of the rainfall the rest of the year shows how borderline Cs the climate really is.
Quote:
Originally Posted by Joe90
Wiki mentions convection, not westerlies as the primary rain source of rainfall in Florence. The sunshine hours during summer, 300-330, would indicate that high pressure still dominates. It seems like it could just be a Mediterranean climate with high summer convectional rainfall. If not, it must be a Humid Subtropical climate.
Does that mean that Humid Subtropical climates are really just Med climates, with increased convectional rainfall in summer?
As a general rule, as you work your way northward in Italy, seasonal rainfall profiles change shape from a strong winter maximum in far southern Italy/Sicily….to a fall/winter maximum in southern –south central Italy….to a strong fall maximum in central and northern Italy. In the case of Florence (far northern Italy),in the fall months the air is cooling but the Med Sea is still warm, and the effect of the warm sea surface helps to make the air unstable and showery, creating the fall maximum of rainfall (again the rest of the year is far from dry in Florence). The northern Med Sea is an important route for fall /winter cyclones and their associated rainfall.
Perhaps in summer, warm airmasses that are semi-humid (due to the Med Sea) orographically produce some convective rains in Florence. However, the hallmark of a Cs/Med climate is STRONG subsidence at the time of high sun (meaning NO chance for convection). So if there are frequent convective rains in Florence in summer – that is even more for the case that it is not a Cs/Med climate at all.
I didn’t see the sunshine hrs for Florence – but climatically I’m sure they are quite high at the time of high sun…and high pressure is no doubt responsible for much of this. Whether Florence is Cs or Cfa (more likely) 40 – 43 latitude is still far enough southward (at least in the summer months) that the subtropical highs (whether the stable east side…or unstable west side) still have an impact at the time of high sun. I live near 40 – 41 north, and in the summer the subtropical high (on the unstable western side) still can produce long bouts of dry weather and sunshine, with only spotty convective thundershowers late in the day.
As far as Humid Subtropical climates really being just Med climates, with increased convectional rainfall in summer...no doubt they share many of the same genetics, as both are subtropical climates, with several similar controls. The biggest difference is that one (Cs/Med climates) are located at the time of high sun near the stable eastern sides of the subtropical highs....while the other (Cf/Humid Subtropical) are located at the time of high sun near the unstable western sides of the subtropical highs.
Last edited by wavehunter007; 04-22-2013 at 08:32 AM..
I checked the book (An Introduction to Climate – 5th Edition Trewartha and Horn - 1980):
You’re definitely correct: It appears they are one in the same or one is considered an alternative definition.
On page 260 it says; Cs = Dry season in summer of the respective hemisphere. At least three times as much rainfall in the winter half or the year as in the summer half of the year. Driest summer month receives less than 3 cm (1.2 inches).
On page 402 it says Cs = Summer Dry; At least three times as much rainfall in the wettest month of winter as in the driest month of summer*2, the driest month of summer receives less than 3 cm (1.2 in.) of rain. (Bottom of page)*2 = Alternative definition: 70 % or more of the average annual rainfall is received in the winter 6 months.
Florence does just make the Cs definition cut (driest month 1.4 inches/wettest month 4.4 inches). However, using either definition there is still no month that receives less than 1.2 inches of rainfall. So technically,. I’m not sure. I think this another case where the whole climate picture has to be examined. Even if Florence did have one month that had less than 1.2 inches of rainfall, just looking at the amount and rhythms of the rainfall the rest of the year shows how borderline Cs the climate really is.
As a general rule, as you work your way northward in Italy, seasonal rainfall profiles change shape from a strong winter maximum in far southern Italy/Sicily….to a fall/winter maximum in southern –south central Italy….to a strong fall maximum in central and northern Italy. In the case of Florence (far northern Italy),in the fall months the air is cooling but the Med Sea is still warm, and the effect of the warm sea surface helps to make the air unstable and showery, creating the fall maximum of rainfall (again the rest of the year is far from dry in Florence). The northern Med Sea is an important route for fall /winter cyclones and their associated rainfall.
Perhaps in summer, warm airmasses that are semi-humid (due to the Med Sea) orographically produce some convective rains in Florence. However, the hallmark of a Cs/Med climate is STRONG subsidence at the time of high sun (meaning NO chance for convection). So if there are frequent convective rains in Florence in summer – that is even more for the case that it is not a Cs/Med climate at all.
I didn’t see the sunshine hrs for Florence – but climatically I’m sure they are quite high at the time of high sun…and high pressure is no doubt responsible for much of this. Whether Florence is Cs or Cfa (more likely) 40 – 43 latitude is still far enough southward (at least in the summer months) that the subtropical highs (whether the stable east side…or unstable west side) still have an impact at the time of high sun. I live near 40 – 41 north, and in the summer the subtropical high (on the unstable western side) still can produce long bouts of dry weather and sunshine, with only spotty convective thundershowers late in the day.
As far as Humid Subtropical climates really being just Med climates, with increased convectional rainfall in summer...no doubt they share many of the same genetics, as both are subtropical climates, with several similar controls. The biggest difference is that one (Cs/Med climates) are located at the time of high sun near the stable eastern sides of the subtropical highs....while the other (Cf/Humid Subtropical) are located at the time of high sun near the unstable western sides of the subtropical highs.
Thanks. That cleared up the differences for me, between the two climattes
Since Seattle clearly fits the mediterranean genetics and rainfall distribution, does that make it a subtropical climate?
Thanks. That cleared up the differences for me, between the two climattes
Since Seattle clearly fits the mediterranean genetics and rainfall distribution, does that make it a subtropical climate?
Subtropical climates (either Cs or Cf) have 8 or more months with a mean temp of 10 C/50 F or higher. Seattle has only 7 months (the same as NYC or Seoul, for example) when mean temps are 10 C or higher. So Seattle is not a subtropical climate.
As far as the rainfall spread, Seattle DOES have a dry (er) summer, which is characteristic of Cs/Med climates. The North Pacific High has a subcenter (shaped like an arm) that reaches up toward BC from June to late September. Though no months are fully dry in Seattle, there is less rainfall from late May to early September. However, as anyone who looks over the long term data for Seattle can tell (or anyone who has lived there any length of time), the high latitude of Seattle often is too high for the subtropical high to reach in some years (or the Highs is weaker in a particular year), and there is a wet(ish) summer or summer months. Last summer the NPH was a bit weaker, Seattle had between 3 and 4 inches of rainfall in June of 2012 - which is quite wet.
Keep in mind that winters all over Europe and the US were generally colder in the 19th century. I find the reading suspect as well, but once-in-a-lifetime temps may occur. I don't know about France, but here the readings were sometimes rounded up or down a half degree. It wasn't so accurate then, and neither were the equipment. A low of -23.9C and a high of -6.7C is from my experience completely possible. Not perhaps normal, but possible. We had one such day and night this January.
Yes, it's completely possible, even commonplace, in Finland. Western and southern Europe is another matter.
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), even though southern Europe is the region where Mediterranean climates where given their name ….it is really the Near East and North African sectors of the rim lands of the Mediterranean Sea that exhibit Cs/ Mediterranean climate in it’s pure development. Areas on the northern rim lands of the Mediterranean Sea connected to Europe are less true to type and more transitional in nature. 
Ice days seem very rare, but nights can go below freezing for several nights in a row.
