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like already said, the tropical air mass is far more stable than temperate ones with 850mb temps around 20C all the time, temperate air masses are much more variable (temperature and humidty wise). For example the mixing of a hot arid/semi-humid air mass (+25C in 850mb and higher) and a tropical one in the temperate zone results in high indices unheard of in tropical regions, because arid air masses don't exixst near the equator and low latitudes (with a exception of a few african regions and probably NW Australia). So basically the constant humidity of the tropical air mass keeps it relativly cool (record highs and heat waves) compared to temperate climates! If you look at the 850 mb temperature maps, you can clearly see, that the tropical airmass almost never exeeds 22C, while some areas in the temperate regions often top out at 30C and higher! That's because dry air masses heat up quite fast while humid ones have their limit!
BTW: That's also the reason why tropical thunderstorms are much weaker (the only extreme thing is large ammounts of precipitable water, that can result in floodings) than temperate ones, the tropical air mass is relatively uniform from the surface up into the higher atmosphere, while in themperate regions you have that crazy variations in diffrent levels of the atmossphere resulting from diffrent air masses interacting.
Last edited by Mr. Uncut; 03-12-2016 at 06:54 AM..
like already said, the tropical air mass is far more stable than temperate ones with 850mb temps around 20C all the time, temperate air masses are much more variable (temperature and humidty wise). For example the mixing of a hot arid/semi-humid air mass (+25C in 850mb and higher) and a tropical one in the temperate zone results in high indices unheard of in tropical regions, because arid air masses don't exixst near the equator and low latitudes (with a exception of a few african regions and probably NW Australia). So basically the constant humidity of the tropical air mass keeps it relativly cool (record highs and heat waves) compared to temperate climates! If you look at the 850 mb temperature maps, you can clearly see, that the tropical airmass almost never exeeds 22C, while some areas in the temperate regions often top out at 30C and higher! That's because dry air masses heat up quite fast while humid ones have their limit!
BTW: That's also the reason why tropical thunderstorms are much weaker (the only extreme thing is large ammounts of precipitable water, that can result in floodings) than temperate ones, the tropical air mass is relatively uniform from the surface up into the higher atmosphere, while in themperate regions you have that crazy variations in diffrent levels of the atmossphere resulting from diffrent air masses interacting.
Central Brazil gets 850hpa temperatures of 30+ several times a year, and this also happens in Southeast Brazil albeit lesser.
And what you said probably don't apply to Rio, being the city close to Tropic of Capricorn(22ºS) and subject to extreme weather and conflicting air masses.
Central Brazil gets 850hpa temperatures of 30+ several times a year, and this also happens in Southeast Brazil albeit lesser.
Not really, getting temperatures above 30ºC at 850 hPa in the "free atmosphere" in South America is extremely rare. I remember the La Pampa heat wave in Jan 2014 in Central Argentina, the maximum at 850 hPa was about 29ºC, whereas surface temperatures reached up to 45.0ºC.
What I think it may have happened is that as Brazil has many areas lying around 1000/1500 metres (BrasÃlia itself is at 1150 m), the models can forecast >30ºC at 850 hPa over there, figures which are actually heavily influenced by the relativaly close surface heating. It must have happened repeatedly last spring, which was freakingly hot in Central South America.
More on topic, the answer of the thread lies in the general atmospheric circulation. In Equatorial areas the air is forced to go upward due to the heating of the surface, and subtropical latitudes consequently get subsidence that if forced to adiabatic warming will cause such extreme temperatures impossible in Equatorial regions.
Stop looking at record highs or even average highs. You should look at daily averages to assess whether a place is hotter or colder than another.
As i said, Rio is, on average, much hotter than Buenos Aires or Sydney. In fact, Rio is consistently recording temps over 40C several times every year.
Australia is not a hot place. There may be isolated hot locations in Australia but those are the exception, not the norm.
I have to disagree. Australia is a bloody hot place.
Something I would agree with is that none of the major cities of Australia are particularly hot places since they are all coastal, but the interior is quite undoubtedly the hottest part of the world from Nov-March.
Here is what today looks like. You can find it on Wundermap. Judging from data in several places (such as Tibooburra NSW, Alice Springs NT, Newman WA, Giles WA, Oodnadata SA, Charleville QLD, and Rabbit Flat NT, for specific examples) it seems like a typical day for this time of the year. Much of NSW looks some degrees above average, but that's about it.
Mid 30's on a typical day is certainly quite "hot," at least by most people's definition of the word.
Last edited by Shalop; 03-12-2016 at 09:09 PM..
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