The Mediterranean and its odd rainfall patterns... (climate, warm, global warming)

[CairoCanadian]

Lately I've been snooping around the Mediterranean and I've noticed that while much of its shores has the winter wet, summer dry classic ''Med'' climate, there's a lot of strange patterns on its shores, particularly on the European side. The humid subtropical of the northern Adriatic is fairly well known, with cities like Venice and Trieste being good examples:

Venice - Wikipedia, the free encyclopedia

Percipitation patterns here seem very even, with minimums in winter.

Also the ''continental'' Mediterranean weather of the upland regions of Spain:

Albacete - Wikipedia, the free encyclopedia

Here one sees a pattern I notice commonly in the Mediterranean basin: two peaks, one in late spring to early summer, the other in late Fall, with drier winters and summers and a more regionally variable stretch in early spring.

It's a pattern that doesn't just influence the uplands, however, and seems endemic to many north- and east-facing Med locales, sometimes to the point of them being non-Med climates.

Compare three Mediterranean locations in a region's west coast, versus its east:

Iberian Pen:
Lisbon - Wikipedia, the free encyclopedia
Valencia, Spain - Wikipedia, the free encyclopedia
Italian Pen:
Rome - Wikipedia, the free encyclopedia
Rome - Wikipedia, the free encyclopedia
Greece:
Corfu - Wikipedia, the free encyclopedia
Thessaloniki - Wikipedia, the free encyclopedia

In all these examples, the west coast follows the classic winter wet, summer dry pattern with significantly more percipitation that their east coast equivalents ( which makes sense, given the prevailing wet winter westerlies ), but what is more confusing is that the eastern locations often recieve more summer rainfall that their western counterparts ( despite lower overall rainfall ), which makes me think there is a mild wet easterly influence that puts the western areas on the dry side of a summer-only rain-shadow.

Inland and upland areas of Italy show something suprising. Often, instead of just the overall percipitation increasing with altitude, only the summer level rises, giving an oceanic climate rather than a Mediterranean one.

Campobasso, Italy: Climate, Global Warming, and Daylight Charts and Data

The questions I'm left with are:

Where is this mildly wet summer influence coming from? Asian most influences are half a world away.

How come upland regions of Italy, Spain, and the Balkans have such different rainfall patterns from their lowland siblings, rather than just being cooler and wetter?

[nei]

Wet summer influence is probably local convection (dew points aren't that low, compared to say, the American west).

(I might be wrong about this): You tend to get less thunderstorms near the sea (for example, the coast of New England gets the least thunderstorms east of the Rockies). And the sea has a stable high pressure over it; air over land is more unstable.

So maybe the best way to think of it is west coast places in the Mediterranean have a bit more of a Mediterranean weather pattern while east coast have weather patterns with a bit more continental style.

[Trimac20]

Venice doesn't really seem like a Mediterranean climate to be looking at the rainfall and temperature stats. Winters seem a bit cold, and with rainfall even throughout the year that is hardly a sub-tropical wet winter/dry summer pattern. It looks more like a humid sub-tropical regime under Koeppen/Trewartha...in fact I don't think it's considered Med. But maybe you mean the region in general. It's like 44'N or something so no surprise. Most of the Mediterranean above 40'N gets some summer rain: dryless summers of the type familiar in California tends to occur in southern and eastern rim of the Mediterranean, and north Africa to an extent.

[CairoCanadian]

Nei - I like this idea, but my question would be, then how come this doesn't seem to be the case in the Mediterranean areas in the Americas or the Australia ( I couldn't find enough weather stations in South Africa ). Comparing coast and inland cities like Sausalito versus Sacramento, or Valparaiso versus Santiago, inland areas, while being more storm-prone the rest of the year, were typically as dry or drier than their coastal equivalents. Also, the peculiar Italian pattern of oceanic highland areas - locations like Mount Hamilton versus San Jose, while showing a similar temperature drop, show a typically Mediterranean rainfall curve, rather than the strong oceanic influence in central and southern upland Italy.

Trimac - yes, the Po Valley and Istria are humid sub-tropical. I was speaking about the region as a whole, which shows a surprising variety of climates both within and outside of the Mediterranean designation.