On 3 Feb 2010, at 23:31, Michael Mace wrote: > We all know what a Mediterranean climate is -- it's dry warm summers and > cool wet winters. A local botanist, Hans Roemer, developed graphs of rainfall and temperature over the course of the year. He found that if the two vertical axes were scaled and aligned "just so", it showed the summer dry period, both its length and the intensity of the drought. In essence, this scaling and aligning converted the termperature graph to one of transpiration, so the result showed periods when transpiration exceeded precipitation and vice versa. He found that Victoria's climate, in this analysis, is resembled most closely a city on the Dalmation coast of modern Croatia. The trouble with trying to put all this on one geographic map is that you want to capture three elements each of the precipitation and temperature regime: the annual average, the width of variation around that average, and the locations of the annual minima and maxima. This might be doable since pixel values in graphics can be specified using hue, saturation, and brightness. By restricting precipitation to one range of hues and temperature to another non-overlapping range, you could in theory color the map in a way that represents all six parameters of the climate in this simple model. Maybe! At any rate, it's quite correct to say that not all Mediterranean climates are the same. Unfortunately, there are other factors that influence "what plants grow where", soil texture and subsurface drainage being a particular issue. Those who garden on stiff badly drained clays are well aware that a different cohort of plants likes their gardens than like gardens on loose, sandy, sharply drained soil. I rather wonder if a simpler approach might be to select a range of indicator plants and then display a map colored wrt how well they grow in different areas. -- Rodger Whitlock Victoria, British Columbia, Canada Maritime Zone 8, a cool Mediterranean climate on beautiful Vancouver Island http://maps.google.ca/maps/…