Re:_Back_here,_at_40°C
- Subject: Re:_Back_here,_at_40°C
- From: J* D*
- Date: Thu, 2 Aug 2001 17:15:13 -0700 (PDT)
If you've ever flown from here to Hawaii in the summer
you've seen how our inversion is continuous with
theirs - just shallower and colder on this end (2000
ft. over 50F ocean vs. 5-6000 ft. over 75F ocean).
Very intriguing thought as those of us who appreciate
balmier climes shiver and curse at the fog.
-Jason Dewees, Arecaceae fanatic
--- "Seán_A._O'Hara" <sean@support.net> wrote:
> At 08:32 AM 8/2/01 -0700, Jason D wrote:
> >Here in the San Francisco Bay Area, we've had a
> string of at least three
> >weeks of foggy nights, overcast mornings, and cool
> days - a July pattern
> >that may be typical but always feels a bit gloomy.
> Of course, without it,
> >our redwoods wouldn't survive until the next rainy
> season. We take
> >whatever chance we can get to escape to warmer
> zones, some a half an hour
> >drive inland, or up a mountain, above the chilly
> marine layer.
>
> This caused me to recall when Allesandra came to San
> Francisco last year in
> September to speak at our Gardening Under
> Mediterranean Skies II
> Symposium. She was curious to see "this San
> Francisco Fog" and found she
> was not disappointed, even on her first night!
>
> Many people are perplexed about why we get this fog.
> It has as much to do
> with the complex topography of the Bay Area as it
> does the Pacific Coast
> waters to our west. The fog is created by the
> relatively cool waters of
> the Pacific and the warmer summer air temperatures.
> It often 'hangs about'
> off the coast for weeks (months?) at a time. The
> reason it invades the
> land is due to the heating up of our very large
> central valley. See the
> following satellite image:
>
http://tornado.sfsu.edu/geosciences/California_WebPages/PointReyesEddy.jpeg
> This show fog lying off the coast as well as some
> topographical indication
> of the central valley. Note that the only opening
> out of the central
> valley is through our delta which exits our the
> Golden Gate.
>
> When the interior valley heats up, that mass of air
> rises. The vacuum
> caused by this rising air pulls air in from
> somewhere else - the only
> available place is the Golden Gate. This pulls the
> fog onshore and into
> the delta. Some of our local areas (San Francisco,
> Berkeley, Richmond,
> etc.) lie right in the path of this pull and
> therefore tend to end up with
> foggy days during this effect. If the fog invades
> the interior valley
> enough to have a cooling effect, then this lessens
> the 'pull' and there
> fore the fog effect. Ultimately the valley will
> warm again and start the
> whole thing over.
>
> If there is a warm inversion layer, the fog is kept
> low and to only the
> openings into the interior. One of our favorite
> sightings is on a sunny
> day when the fog is entering through the Golden Gate
> and maintaining a
> distinct 'tunnel' across the bay and into the delta.
> You can see it for
> miles and drive in and then out of it. If the
> inversion layer is less
> successful, the fog can spill over the coastal
> mountains like some huge
> slow-motion wave. All of this usually happens when
> there is warmer weather
> so depending upon where you are that day, you could
> either want to go in
> short sleeves or in your polar fleece!
>
> A view of the fog coming into the Golden Gate
> (viewed from the Bay side):
>
http://www.aerialimages.com/fineart/scenic/Golden_Gate/Golden_Gate_3.jpg
>
> This is what makes the Bay Area so livable - the
> mitigating effect of the
> fog. Without it, we'd be much hotter and much
> drier. While all of the
> above is happening, many of the interior area are
> suffering through intense
> heat that drive people indoors to their
> air-conditioners!
>
> Meanwhile, My garden is loving these moderate days
> (we get the cooling
> effect but little of the actual fog itself),
> especially after numerous
> record-setting heat waves we have this spring and
> early summer!
>
> Seán O.
>
>
> h o r t u l u s a p t u s - 'a garden
> suited to its purpose'
> Seán A. O'Hara fax (707) 667-1173
> sean@support.net
> 710 Jean Street, Oakland, CA 94610-1459, U.S.A.
>
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