Posted by Brandt--San Diego on 5/16/2008, 9:54 pm, in reply to "I read up on this"
75.80.184.205
I think part of the reason Canberra is so much colder in winter is because it's inland--looking at the map, it's about 80 miles from the coast. Somehow I had thought it was higher than 1800'--but I just "googled" the elevation, and sure enough, that's it. Yep--you probably wouldn't find anyplace at 1800' in So-Cal that gets 90 frosts per year (though there certainly are places at/below that elevation here--especially canyons/valleys--that can get hard freezes and are mid-level zone 9).
The big difference with elevation issues between the Northern and Southern Hemisphere is that there's a greater lapse rate in the S.H...so it gets cold faster as you go up in Australia and New Zealand. Note that timberline is 6000' in Australia near Kosciusko (which is as far from the equator as northern New Mexico, which has a timberline of about twice that--and even the Great Smoky Mountains, also at a similar latitude, except North of course, would have a timberline of several thousand feet higher than Kosciusko if they were higher). New Zealand has timberlines in the 3000-4000' range! This is because it's harder to transfer heat high into the atmosphere when you have so much water versus landmasses (yet the S.H. is warmer at sea level in winter for the same reason--hence you have a lot more zone 9/10/11 locations in the mid-latitudes in the S.H. than the N.H.--hence Sydney has a lot of great plants growing).
Also, climatic records indicate that winters last longer in the S.H. (albeit in their milder form), so that helps to add up the number of frosts per year).
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