Sunday, April 26, 2009

An Ocean Full of Low Clouds


Take a look at the visible satellite picture for northeast Pacific Ocean (see image). Notice anything? Something that is quite different than a few months ago? Something that happens virtually every spring?

The answer:
The ocean is covered for thousands of miles by low stratus/stratocumulus clouds.

We are talking about millions of square miles of low clouds. Every spring we see these low clouds blossom and dominate into summer. And it is the movement of these low clouds into our area during June that produces the familiar June gloom (there are other terms but this is a family-oriented web page). And many of the summer phenomena that I talk about in my book (the onshore push, alongshore surge, etc) are connected with the stratus/stratocumulus of the Pacific.

Why the low clouds? A hint can be found in the surface pressure analysis for this morning at 11 AM (see graphic). A large high pressure area has formed over the northeast Pacific. High pressure is associated with sinking air (called subsidence in the business), and sinking air produces warming aloft since air warms when it is compressed (the air is going from low pressure aloft to higher pressure at lower elevations). The sinking weakens towards the surface since air can't go through the surface! With stronger sinking-warming occurring aloft then near the surface the atmosphere becomes more and more stable--which means there is less tendency for vertical mixing. If you think about it this makes sense, warm air is less dense than colder air...and in nature less dense fluids natural rise above dense ones. This is a stable situation. A dense fluid on top of a less dense one is an unstable configuration.

The stable atmosphere allows moisture to accumulate at low levels, leading to low clouds. Another factor, that is particularly strong near the coasts, is that the high pressure produces northerly winds near the coast, which results in upwelling (see my book for an explanation of this), which brings up cool water. Cool water helps saturate the lower atmosphere....that is why the densest stratus is often along the west coast..particularly central CA.
Anyway, getting back to the story, high pressure builds northward out of the subtropics during the spring and the stratus follows . In the wintertime, as the high retreats and cold air moves in aloft behind Pacific systems, the atmosphere is much better mixed and the low clouds don't form.

So watch the satellite pictures and Pacific pressure patterns...you will note a close association of the low clouds and high pressure areas.

Seattle Math Adoption Decision is Still Up in the Air

PS: I will have an update on the current Seattle high school math situation this week. You won't believe what happened at the school board meeting last week...they split 3-3 and will try again on May 5th. I was amazed that three of them are still considering a terrible math series (Discovering Algebra, Discovery Geometry) that was found by the State Board of Education to be unsuitable. And dropped by San Diego as a failure.

5 comments:

Jeff said...

That is very interesting and enlightening. But, will Monday be a good day for golf?

JewelyaZ said...

The UW Probcast for Bellevue calls for 59 and a 10% chance of showers. I'd say that's OK golfing weather unless you're a lizard like me (and most golfers seem not to be the kind who always run cold).

Cliff, I wish the UW Probcast provided one more feature... I want to see a "Yesterday's Actuals" page... box 1, the daytime probcast, box 2, the daytime actual temp and precip; box 3, the nighttime probcast, box 4, the nighttime actuals. Yes, I know that's another page to code, but you guys must be recording the data already, so it's just a matter of writing a script to regurgitate the values.

I'd love to gain an understanding over time of how the Probcast is "usually wrong" -- which direction and how much. My non-scientific perception is that if we get precipitation, it tends to be more than estimated, often even more than the high estimate.

wildbill said...

Heat Retention Q. I built a potato box, about 16 cu ft. I might line the inside of the 2x6 with mylar space blanket or alum foil to block transmission of IR into the wood. This would work but I would still have heat loss from conduction from soil to foil to wood to air plus radiant loss from wood outbound. Because box is above ground, I should be able to conserve heat. Would this work? Would heat retention be good or just some? Cliff: I get cold hands riding and went to Outdoor Research asking about mylar lined gloves and they don't make them. Mylar is outstanding for keeping a growler of beer cold and for keeping a chest full of dry ice cold for many days.

Dorothy said...

A slight correction. The board *said* they were split 3-3, however, they didn't actually vote. They had even rehearsed with the district's parliamentarian how to phrase the postponement. I too was surprised at two of the directors who seemed to favor the adoption and would really have liked it if they had been forced to actually vote their approval (even if they knew in advance it would be a tie).

Anyone interested in writing the directors about the issue can watch the school board meeting on-line, Channel 26 will show it streaming. Then you can be specific in your comments to them.

Two sources for discussion. Director Martin-Morris maintains a blog. And Charlie Mas has written about the wonderful changes the district is promising to go along with the adoption. Although there's no money, the district, acknowledging how unfavorable this adoption is, has promised professional development to help teachers teach parents how to help their kids. They've promised to create a DVD for parents to borrow and watch to learn how to help their kids with homework, they've promised to be more effective partners with universities to get and retain better teachers. They've promised to hire an outside firm to perform a survey and hold focus groups to verify that the series is working -- but there is no money for that and certainly no money for a second adoption within 10 years. Watch the presentation at the school board meeting yourself.

If you write the directors about this issue, you may ask them how the district is going to follow through with these promises, how they are going to enforce the promises and honestly, if we were adopting some plain jane text series that was useful as a reference tool, would the district feel like they had to make these extra promises?

garyLambda said...

My kids just went off to college and both had to take remedial math which they excelled at even though they had nearly failed math in High School. Which is because at the college level they don't teach that fuzzy math stuff. It doesn't work for most students.

What's amazing to me is that all the math we try to teach High School students was known roughly by the time of Newton & Leibniz which is the 1690's. So we've had 400 years to figure out how to teach math and we still make a hash of it!