Interesting explanation for higher than normal low temps in northern CA

[elagache]

Dear WeatherCat fans,

These days, we are all looking to the skies with some fear and trepidation whenever the weather appears to depart from our normal expectations.  There has been some odd weather this summer here in northern California, but one aspect of this weirdness got an unexpected explanation that I thought was interesting enough to share with you'all.

The overnight temperatures have been significantly higher than expected for this early in the summer.  Normally the overnight lows are in the mid 50˚s F (10˚C), instead they are struggling to drop below 60˚ F (16˚ C).  Is this another example of the dreaded global warming?  Well, it very well might, but the mechanism is more complex than warmer temperatures.

It turns out the warmer overnight lows are being caused because our "air conditioner" (heat sink) being warmer than usual.  The temperature of California's coastal waters are strongly effected by the cold California current.  That's why scuba diving along all of the Pacific coast of the United States is mostly a desperate struggle to keep warm.  Water's north of San Francisco are a frigid 49˚ F (9.5˚ C) and below.  Monterey bay is bit warmer in the lower to mid 50˚ F.  The weather in coastal California is usually dominated by an onshore flow.  The interior land heats up causing the air above it to rise.  Air that is over those cool ocean waters is drawn inland to replace the rising air.  That is the simple mechanism for the San Francisco Bay Area's own natural air conditioner.

So what has mucked up with our air conditioner?  It turns out that there is an oceanic phenomena necessary for this air conditioner to work called: upwelling.    Here is the Wikipedia article on it:

http://en.wikipedia.org/wiki/Upwelling

Upwelling occurs when water along the coast is moved further out to sea.  When this happens, water from deeper regions of the ocean moves up to the surface to replace the water moving away from the coast.  That water from deep within the ocean is full of nutrients, but is also very cold!  It turns out that the winds that are responsible for upwelling along California's coast are not as strong as normal.  As a result, the waters along the coast are warming up.  Some of the waters off the San Francisco and Monterey bay areas are at hot as 60˚ F, a good deal warmer than usual.  As a result, our natural "air conditioner" isn't blowing as cold as usual and our overnight lows are remaining warmer than I prefer them.

Why the winds aren't blowing as they normally do, now that might be caused by global warming.  However, the next time you discover that things are warmer than you expect, there just might be an interesting explanation for it.

Cheers, Edouard 

P.S. All this has some interesting implications for local scuba divers.  The whole California coast is known for comparatively poor visibility.  The one exception is when there is strong upwelling.  Effectively that upwelling water acts like a blower to move all the plankton from the coastal waters so the water is clearer in diving areas.  Sounds like it is going to be a really rotten summer for scuba diving in northern California.

[Bull Winkus]

Good story Edouard, but either you left out something or my tired ole brain just can't see the whole picture. I'm not sure if I followed the causal relationships correctly, hence I'm confused. I'll regurgitate what I caught, and see if you'll correct me where I'm wrong.

Wind blowing west from east sends surface water out to sea. Cold deepwater upwells to replace it. So, how does the air conditioner get the cold from the water to the land? Wasn't the wind that caused the upwelling blowing the wrong way to air condition the costal land?

[elagache]

Hi Herb and WeatherCat ferris wheel riders,

I'll regurgitate what I caught, and see if you'll correct me where I'm wrong.

Wind blowing west from east sends surface water out to sea. Cold deepwater upwells to replace it.

Hold it right there!    That's the problem.  The winds don't have to be blowing offshore to cause upwelling.  The winds can be blowing along the coast and still have the same effect.  Take a look at the Wikipedia article:

http://en.wikipedia.org/wiki/Upwelling

In the article is the following illustration:



With the following explanation: If the wind blows parallel to the coast in the northern hemisphere (such as the coast of California, where the wind blows South), then Ekman transport can produce a net movement of surface water 90? to the right. This may result in coastal upwelling

One thing that will give you headaches whenever you think about either wind or ocean currents is the Coriolis effect (here is the Wikipedia article on that:)

http://en.wikipedia.org/wiki/Coriolis_effect

There is another illustration from that second article (this time animated:)



With the following explanation: In the inertial frame of reference (upper part of the picture), the black ball moves in a straight line. However, the observer (red dot) who is standing in the rotating/non-inertial frame of reference (lower part of the picture) sees the object as following a curved path due to the Coriolis and centrifugal forces present in this frame.

It turns out that the water motion in Northern California is driven by a phenomena called Elkman transport (yet a third Wikipedia article:)

http://en.wikipedia.org/wiki/Ekman_transport

In a nutshell, Elkman transport works because of the Coriolis effect and the difference in drag between the winds and the water.  The full details are described in painful detail in the article, but the net effect is that the winds blowing along the coast result in water moving away from the shore. 

I guess there is one more fly in the ointment to resolve.  The winds flow in different directions depending on the time of day.  During the day, the winds are more along the shore.  At night the winds are more onshore.  That's why areas just a few miles from water can heat up a lot during the day.  However, they will normally be cooled by the seabreeze at night.  The exception of course is when the winds turn offshore and then we really get blasted by the inland heat! 

So does that help . . . . or did that make it worse? 

Cheers, Edouard 

[Bull Winkus]

Thanks Edouard. So it's that ole bicycle tire effect, again. And, I thought it just carried my meat head down the road when I was a kid.

You ought to see what instrument designers have done with that Coriolis effect.
http://en.wikipedia.org/wiki/Mass_flow_meter

So, I take it that the slip in overnight temperatures is due to less of that all important wind. Wind slows down, water movement slows down, upwelling effect slows down = warmer nights. Your natural AC has lost some of its coolant.

Like the doldrums of the stock market, this too shall pass. Hang in there Edouard. California will get back to being its old self again sooner or later. What's life without a few thrill rides, anyway?

[Blicj11]

Edouard and Herb:

Thanks for the links and the explanations that dumb it down enough for people like me to follow along.

[elagache]

Hi Herb, Blick, and WeatherCat fans,

You ought to see what instrument designers have done with that Coriolis effect.
http://en.wikipedia.org/wiki/Mass_flow_meter

Yes a very elegant use of the Coriolis effect!

Oddly enough, there is very practical application for mass flow meters: automobile engine fuel injection systems.  When I was shopping around for a fuel injection system for my trusty wagon's engine, I was tempted by a system using mass flow meters.  Alas, the company was on the edge of bankruptcy, so it wasn't a reasonable choice.  But the concept was very elegant.  Instead of guesstimating how much gasoline the engine needed to run, the system would literally "weigh out" the fuel needed.  Simple and much more accurate than estimates based on tables of average engine performance.

So, I take it that the slip in overnight temperatures is due to less of that all important wind. Wind slows down, water movement slows down, upwelling effect slows down = warmer nights. Your natural AC has lost some of its coolant.

It doesn't matter all that much since we installed central air, but it is a simple example of how simple intuitions about climate can be very misleading.  I'm having unpleasant flashbacks to the years I lived in San Diego.  The fog in San Diego feels very much like the Bay Area fog does today.  One might naively attribute this to overall temperature increases due to global warming.  However, the reality is actually more interesting.  the Monterey Bay buoy set a record for a water temperature of 67˚ F degrees on Tuesday.  Those are exactly the sort of water temperatures to be found next to San Diego.  The Physics of climate are very complex, but they aren't beyond understanding if you put a little effort into it.

Thanks for the links and the explanations that dumb it down enough for people like me to follow along.

That brings me back to James Burke's Connections series.  We've all got to try to actually understand what is going on.  If we don't we really are at the mercy of experts who don't have our best interests at heart.  We live in a world of unabashed self-interest.  All we can expect is that the experts would have their own best interests at heart.  So if we don't stand up for ourselves - nobody will.

Cheers, Edouard 

[Bull Winkus]

Wise words, Edouard.

I remember an old joke that made the rounds in the blue collar world of plant maintenance. When someone would accuse me of being an expert, my curt but polite answer was, "I'm no expert. Do you know what an expert is?

"What?"

"Well, in Science X stands for the unknown, so an expert must be an unknown drip under pressure."

Life in the 21st Century is getting more complicated each day. It has long been too complicated for any one individual to be completely self dependent in solving all technical issues inherent in day to day living, what with legal, insurance, economic, social, scientific and survival issues all continuously evolving over time. It just can't be done. So, we all have to depend on other people who specialize in this or that to get things done correctly in a timely manner. But, that's not to say that we should trust these specialists implicitly! In my opinion, it is imperative that the individual of today be knowledgable to some extent about almost every aspect of our complex technocracy. Because, as you stated, the technocrats are, as we are, looking out for their own best interests, and both collectively and individually, we ignore that at our peril.

[elagache]

Hi Herb and WeatherCat armchair philosophers,

Life in the 21st Century is getting more complicated each day. It has long been too complicated for any one individual to be completely self dependent in solving all technical issues inherent in day to day living, what with legal, insurance, economic, social, scientific and survival issues all continuously evolving over time. It just can't be done. So, we all have to depend on other people who specialize in this or that to get things done correctly in a timely manner. But, that's not to say that we should trust these specialists implicitly! In my opinion, it is imperative that the individual of today be knowledgable to some extent about almost every aspect of our complex technocracy. Because, as you stated, the technocrats are, as we are, looking out for their own best interests, and both collectively and individually, we ignore that at our peril.

Your point is well taken Herb, but I don't think it goes far enough.  I decided to go through the James Burke's Connections series once more and every viewing is a chance to learn some more.  Someone has posted on You-Tube a pithy 7 minute segment from the first episode of Connections:

http://youtu.be/4sb7bOljBAQ

The point Burke is making in this snippet is one that really needs to hit home for everyone dependent on technology: technology is our life-support system.  What keeps us alive in the modern world is a complex web of interconnected technology and even seemingly modest calamities (like a power failure) could cause the web to start imploding upon itself.  When that happens as Burke dramatizes in this snippet from the first episode, the only hope any human being would have is going back to the most primitive technologies humans first came up with - because only those simple technologies would be free of all those dependencies that have now unraveled.

So as the 7 minute segment so compellingly argues, we truly live in denial of our complete dependency on technology we can neither understand or control.  Such denial won't prevent bad things from happening because we live as if such catastrophes are impossible.

Definitely food for thought.

Edouard 

[Bull Winkus]

Your point is well taken Herb, but I don't think it goes far enough.

I somehow knew you wouldn't.

The point Burke is making in this snippet is one that really needs to hit home for everyone dependent on technology: technology is our life-support system.  What keeps us alive in the modern world is a complex web of interconnected technology and even seemingly modest calamities (like a power failure) could cause the web to start imploding upon itself.  When that happens as Burke dramatizes in this snippet from the first episode, the only hope any human being would have is going back to the most primitive technologies humans first came up with - because only those simple technologies would be free of all those dependencies that have now unraveled.

So as the 7 minute segment so compellingly argues, we truly live in denial of our complete dependency on technology we can neither understand or control.  Such denial won't prevent bad things from happening because we live as if such catastrophes are impossible.

Definitely food for thought.

Edouard

Aaaaa? So very clear, now. And, true too! I was there to see what happened during a 21st Century blackout in the suburban townships of Detroit. It lasted less than 24 hours, if I recall correctly. But, people were full on panic buying bottled water in no time.

Yep! When infrastructure evolves around a matrix of dependencies, a seemingly insignificant event can become the fulcrum to a lot of hurt. In fact, most investigations of manmade disasters reveal just that. An improvised strap falls off an airplane during takeoff, which, during the next takeoff on the same runway, leads to the entire flight, crew and passengers of the Concord being lost in a ball of fire, and the planes all becoming grounded indefinitely.

It happens all too easily.

[elagache]

Howdy Herb and WeatherCat armchair philosophers,

Your point is well taken Herb, but I don't think it goes far enough.

I somehow knew you wouldn't.

Awe shucks, you know me too well!! 

So as the 7 minute segment so compellingly argues, we truly live in denial of our complete dependency on technology we can neither understand or control.

Aaaaa? So very clear, now. And, true too! I was there to see what happened during a 21st Century blackout in the suburban townships of Detroit. It lasted less than 24 hours, if I recall correctly. But, people were full on panic buying bottled water in no time.

As pessimistic as it is, I'm amazed nothing has seriously unraveled yet.  Hurricanes Katrina and Sandy certainly pushed the respective regions right up to the edge, but people didn't disintegrate into an "every man for himself" mentality.  Over a decade after 9/11, the condition of our societal life support system is clearly more fragile - not less.  Worse still, the most fragile part of all is information technology.  I wonder how young people addicted to Facebook and Twitter will react to being cut off in a crisis.  It is yet another potential trigger for panic when we have way too many triggers as it is.

I'm sure Burke would change the ending for his series "The Day the Universe Changed" if he could have a chance.

Oh well, . . . . .

Edouard

P.S. The overnight lows are still running about 5˚ F above normal so I suppose the coastal water still hasn't been cooled down by any upwelling.