Monday, February 5, 2018

Behavior of Tides of San Francisco Bay

I'm not going to not write much about these graphs.  I had assumed that as one moves into the Bay, tide range would be attenuated.  So I was surprized to read the following bit from An Introduction to the San Francisco Estuary by Andrew Cohen and Jack Laws:

In the northern reach the tidal range (the difference in height between high water and low water) drops with distance from the ocean, from a mean range of about five-and-a-half feet at the Golden Gate to only three feet at Sacramento.    In contrast, in the southern reach’s more enclosed basin the tides cause the water to slosh back and forth like water in a bathtub, amplifying the range at the southern end to eight-and-one-half feet.

I wanted to explore this, so I graphed several sites in the Northern Reach, and five in the Southern Reach.  These are a work in progress.

The predictions that are graphed here are from Xtide:

In the legend, stations are listed  in order from the Entrance  to the most distant. 

"San Francisco" is the Fort Point station. 

Tuesday, December 26, 2017

"Inconcievably heavy snowfall" in Alaska's Banana Belt

 During my short time in Cordova, AK, I learned that Southern Alaska is "The Banana Belt" of Alaska.  It rained much, hardly ever did the sun shine, but if it snowed, it wasn't a great amount.  Our recent experience with climate/weather on the West Coast prompted this comment on the California Weather Blog:

"...  recently, the bigger & stronger West Coast ridge has pushed the Pacific storm track even further north. Remarkably, this powerful ridge has forced several very moist atmospheric river storms over the mid-Pacific to make a hard “left turn” over the open ocean–veering directly northward and bringing almost inconceivably heavy snowfall to the coastal mountains of southern Alaska."
The link it to an Anchorage Times article.

Thursday, December 21, 2017

Seasons: 23.44° Solstice "Sun Standing Still"

"Solstice" comes from the Latin word solstitium, meaning "sun standing still".

Wikipedia: "Solstice"

 The seasons occur because the Earth's axis of rotation is not perpendicular to its orbital plane (the “plane of the ecliptic”) but currently makes an angle of about 23.44° (called the "obliquity of the ecliptic"), and because the axis keeps its orientation with respect to an inertial frame of reference. As a consequence, for half the year the Northern Hemisphere is inclined toward the Sun while for the other half year the Southern Hemisphere has this distinction. The two moments when the inclination of Earth's rotational axis has maximum effect are the solstices.

 Wikipedia: Season

 In tropical and subtropical regions there is little annual fluctuation of sunlight. However, there are seasonal shifts of a rainy global-scale low pressure belt called the Intertropical convergence zone. As a result, the amount of precipitation tends to vary more dramatically than the average temperature. When the convergence zone is north of the equator, the tropical areas of the northern hemisphere experience their wet season while the tropics south of the equator have their dry season. This pattern reverses when the convergence zone migrates to a position south of the equator.

Tuesday, October 3, 2017

It is impossible that humans will engineer an airtight security system of any kind

It is Impossible!

Human intellect evolved to solve problems, leading to incremental advancements of knowledge.  Note the plethora of innovations that were independently invented simultaneously or nearly simultaneously.  Tim Wu has developed this idea in his book about eyeballs: _The Attention Merchants_.  Industrial Psychologists have understood something like this for a long time: error rates in assembly lines increase over the shift.  There are limits.  Remember the unsinkable ship and prisons from which it would be impossible to escape? 

Why is it a surprize that major online databases are hackable? 

I take it that the human brain lacks the capacity to understand any system sufficiently well to foresee any or all possible shortcomings of that system. 

What are the philosophical ramifications of my statement?

Wednesday, July 19, 2017

A nifty trick for seeing without glasses