Wednesday, May 20, 2015

Monday, May 18, 2015

On the needles

It started out as an Amiga cardigan, but it was going to become too wide by the time the armholes were deep enough for my squarish shoulders.  Half of the full arm depth, I switched to the slower increase rate I learned in a_simmetrie that worked so well in Not Marsala.

I'm using two strands of the olive cotton/rayon/linen slubby coned yarn I used in the Absorbas shown here1 and here2.

Lest my sister call this fabric sleazy (knit with too large holes for the yarn), I want to assure her that I knit and washed a swatch.  The linen fibers will plump up to make a solid fabric. It will also shrink about 10%, which I took into account when I cast on.

Sunday, May 17, 2015

Does this make me a granny?

I solved my exercise vs. errands dilemma again by running the errands by bike. This time, I tackled some gratuitous hills for added challenge.

I thought I was pretty strong because I barely used the lowest gear on my rear derailleur.  But, the shifts were not as clean as I expected; I checked the gear indicator on the shifters.  I did the first half of my bike ride in the "granny gear"!  (That link is pretty sexist and ageist, but explains why mountain bikers call it the granny gear.  Read this transmission mechanics link for how it works.)

I climbed the uphill without stopping--well, one red traffic light.  On the way down, I stopped to take pictures.

Hauling 50 pounds of groceries uphill to my apartment was a bonus workout.

Read the real reason I stopped to take this picture.

Thursday, May 14, 2015

Me Made May 2015 Day 14

I made my top using Vogue 1071 and a remnant of yummy cotton lawn that I purchased from Poppy Fabrics when I was an undergrad at Berkeley. It only took me 20+ years to sew up the piece.

I did not make my pants, socks, or shoes.

This Calvin Klein for Vogue Patterns top takes very little fabric.  I've made this view three times.  I made another view, but, sent it to Goodwill. Poor fabric choice and my inexperience (years ago) with bias edges in rayon crepe made a real mess.

I think that one of the hardest aspects of learning to sew (or knit) is pairing an appropriate fabric (or yarn) and pattern.  What did you find most difficult as a newbie?

In the background, I'm screening Precision and Accuracy in Geodetic Surveying, which uses surveying to teach the difference between precision and accuracy in general.

Lately, I've been thinking and writing a lot about geophysical data formats and metadata standards. To procrastinate do research, I see how others do it.  ;-)

Wednesday, May 13, 2015

The view from my window

I was looking out the window while waiting for the copier to warm up so I could scan a document.  Look at the brilliancy of that rainbow!  I ran to my office to grab my phone/camera.

From the copier room window.
While I was in my office, I looked out the window and noticed the double rainbow.

Double rainbow looking southeast from my office in Boulder.

I suspected the best view would be in my neighbor's office. It's too bad he is at JPL this week so he couldn't enjoy the view in person. I'll have to send him the photo.
My neighbor's window.
Your eyes do not deceive you. That is a large crack in the glass.
Corner offices have great views, but are also subject to some 'ripping' winds that rattle the windows, sometimes cracking them.

My much smaller window is recessed into an updraft 'wind chimney' so it is less prone to shaking and cracking.

Tuesday, May 12, 2015

Wordless Wednesday

Saturday, May 09, 2015

Mothers' Day Flashback: Lessons in Freeway Calculus

NOTE: I originally wrote this essay for James Fallows' blog in 2011 without compensation.  It was published here.  I retained the copyright and I think Mothers' Day is a particularly good time to repost this essay.

As an immigrant, I hate to see my chosen team (America) dissed by know-nothings. The views of the governor of Pennsylvania, after an Eagles-Vikings playoff game in Philadelphia was postponed because of snow:
We've become a nation of wusses. The Chinese are kicking our butt in everything," he added. "If this was in China do you think the Chinese would have called off the game? People would have been marching down to the stadium, they would have walked and they would have been doing calculus on the way down.
Gov. Ed Rendell clearly doesn't understand calculus. If he did, then he'd know that calculus was basically invented to describe motion. (He should have read Steven Strogatz's Change We Can Believe In.) Therefore, anyone in motion -- whether walking to the stadium or driving in a SUV with heated leather seats -- is doing calculus.

(Thanks to my favorite math website, Wolfram MathWorld, for the figures and theorem info.)

On a more serious note, I want the general public to understand that math is a huge subject encompassing much more than arithmetic. People shouldn't give up their math education too soon just because they don't like arithmetic. Many mathematicians are only so-so at arithmetic.

Truth be told, after I finished the introductory lower-division undergraduate math courses at UC Berkeley, I hardly ever worked with actual numbers. My math homework consisted mainly of Greek symbols and other abstract notation along with copious arguments in English describing the steps of the proofs. It usually ended with relief and a big Q.E.D. as I finally signed off on my homework and could go to sleep.

Math is also so broad that mathematicians do not understand all areas of math. It would be like expecting a historian to know about the history of everything. It can't be done, though it might be fun to try.

It would be more productive to think of math as both a liberal art and a science. Not only is math the language of science, giving us a framework for describing our physical world, but it is also a construct of the human mind. As such, lessons learned from math can help us understand the human condition, moving it into the realm of humanities.

A friend who had been an English literature major and I discussed how we thought a book was mainly about one thing, and then reread it years later and thought it was mainly about something else. Was our past judgment so wrong? Or had experience and circumstance changed our perceptions?

Much as I enjoyed Steven Strogatz on the Elements of Math, I hope that readers will go beyond that. I will use the meaning of calculus as an example.

When I first encountered calculus in high school, I mechanically went through the motions of "turning the crank" to learn the rules of differential and integral calculus. I thought that was what it was all about. Sure, there were pages and pages of material about limits in the textbooks, but they were just a prelude to the real stuff of finding the derivative (slope) or the integral (the area under a plot) of a function. So, if you had asked me back then, I would have agreed with Strogatz.

But then a boy that was a year ahead of me in math at Cal told me that he didn't understand calculus until he took math analysis and "proved" calculus. That freaked me out; was I so clueless and shallow that I misunderstood the whole point of calculus?

The panic intensified when I took the class he referred to: Math 104, aka "Real Analysis and Introductory Topology." Our class spent the entire semester on proofs, including six weeks to prove the compactness theorem. What did that have to do with calculus?

Looking back, I can laugh about it. I see now that calculus is such a broad topic, and touches so many aspects of our lives, that it can mean different things in different contexts.

All those weeks spent proving the limit of an infinite series exists and is unique? That tells us that there is a solution of the integral described by the series.

The other weeks spent proving that some limits are reached more quickly than others? The mystery was revealed when I took numerical analysis (solving math problems with computer algorithms). Those fast-approaching limits will converge before lunch. Slower ones may take overnight. The really slowly-converging limits might converge if you made a lucky guess at the initial condition, but will more likely go shooting off into infinity (actually the dreaded floating point overflow error). It's really embarrassing when that happens.

My last big calculus insight occurred while driving across the San Mateo-Hayward Bridge near San Francisco with my daughter. A friend had warned me not to speed on the bridge. She said that cameras photograph the license plates of cars as they enter and exit the bridge; you need not be seen by a cop to receive a speeding ticket by mail.

How can they prove someone was speeding from two photographs? With calculus, using the basic form of the mean-value theorem:
Let f(x) be differentiable on the open interval (a,b) and continuous on the closed interval [a,b]. Then there is at least one point c in (a,b) such that
This is the formula for a derivative on an interval. If a and b are the times your car was photographed (at the entrance and exit of the bridge), and f(a) and f(b) are the locations where your car was photographed, then your average speed is f'(c).

The bridge, or rather the distance between the two camera locations) is a fixed length. If not enough time elapses between the two timestamped photos of your car, then your average speed exceeded the speed limit.

You can compute the average speed with simple algebra; you don't actually need calculus for that. A motorist can try to argue that s/he was not actually observed driving above the speed limit.

But, assuming the time clocks on both cameras were well synced, the mean value theorem says that, even without an observation at the critical time, the motorist must have exceeded the speed limit somewhere along the bridge. The basis of the state's case rests upon a foundation of calculus.

As my daughter and I discussed how this system of cameras might work (and why she should have told me she needed to make a pit stop before we got on the bridge), I had an epiphany.

There is a whole family of mean-value theorems. One in particular leapt to mind, the intermediate value theorem.
If f is continuous on a closed interval [a,b], and c is any number between f(a) and f(b) inclusive, then there is at least one number x in the closed interval such that f(x)=c.
This has major implications in integral calculus, but that is not why I am mentioning it.

I explained herehow I get performance reviews for both my market work (from my boss) and my family work (from my daughter, who claims to be my boss). When I am an ideal worker, putting in long hours at my market (paid) work, I am not at home doing my family work. The opposite is also true.

The term "work-life balance" implies that it is possible to maintain a steady-state ideal balance. In real life, one always gets more than the other, though which one gets more varies  over time. As I oscillate between whichever place demands more of my attention right this instant, I used to feel like I was always failing. But, now, I take solace in calculus.

The intermediate value theorem assures me that -- somewhere between those two positions -- I pass through the state of my ideal self.

Sunday, May 03, 2015

The cheapest aquaduct

Am I the only one who thinks that William Shatner is not completely nuts? He has a point. When California is flush with water, the Pacific Northwest is (relatively dry). When CA is dry the PNW tends to have a surplus of water.

Last week, I read The West without Water (WWW), about the paleoclimatology of the American west.  I read it because I wanted to learn more about the PDO, Pacific Decadal Oscillation that some say is responsible for our drought.  It's not the best book for learning about PDO.

Correlation and anti-correlation of CA and PNW rainfall from The West without Water.
But, HOLY COW!  Paleoclimatology is fascinating.  And droughts like this and even more severe are common occurrences in the American southwest.

WWW deserves a longer and more thoughtful post later, perhaps in tandem with a discussion about Atmospheric Rivers.

I just want to point out that we don't need to literally import/export water between north and south.  It would be much more efficient to ship embedded water in the form of goods.

Saturday, May 02, 2015

Interpreting the Water Footprint of Food

I've read some discussions of the LA Times Water Footprint of Food interactive feature, mainly expressing surprise about the comparatively large water footprint of pulses, dried legumes.

When you look at these plots, a beef burger looks only slightly indulgent compared to a falafel (chickpeas).  What's the harm in a burger?  Or the Atkins diet in general?
Water footprints of protein sources calculated by the
I scratched my head when I saw that graphic as I understood that beef is a highly inefficient source of protein compared to plant sources (but several magnitudes more efficient than tuna!).  How was this calculated?  Is the methodology valid?

This weather and climate data consultant dug deeper.

The folks at The Water Footprint Network explain their methodology here.  The LA Times article said, "Below you can see the U.S. water footprints of selected foods as measured by gallon of water per gram of protein produced or per calorie."

So is this country-specific data?  How can you compute the water-intensity of the US chickpea crop when there is nearly no commercial chickpea production in the US?

Later, in the LA Times coverage, they quote Mekonnen and Hoekstra:
"The average water footprint per calorie for beef is 20 times larger than for cereals and starchy roots," they note, referring to global averages, not U.S.-specific figures. "The water footprint per gram of protein for milk, eggs and chicken meat is 1.5 times larger than for pulses," a group of legumes that includes peas, beans and lentils.
Perhaps the LA Times reported GLOBAL (not US) water intensity in US units of gallons? The article wasn't clear.

I searched and found that the EU compiled and mapped some statistics they downloaded from McGill University.

Global acreage used for chickpea production.

Global production of chickpeas in tons per square km.
If the LA Times reported US statistics, then the chickpea data is highly suspect.  It's the classic "statistics of small numbers" problem.  The smaller the sample size, the more variable and unreliable the statistic.

Suppose the LA Times did report the GLOBAL water footprint, then it is important to look at the hydrologic cycle of the areas where chickpeas are farmed.

Luckily, I work at a weather and climate data archive and have access to stuff like this classic paper about the terrestrial seasonal water cycle by Willmott and Rowe.  See and download the Willmott and Rowe data.  I give you permission to play with your food data.

First page of Willmott and Rowe.

Recall that chickpeas are mainly grown in India, the middle east and sub-Saharan Africa.  Hmm, look at the evaporation in those regions in the early summer.  If most of the chickpeas are grown in India, and ground-level evaporation is exceptionally high there (and moderately high in other regions where chickpeas are also grown), then the global water footprint for chickpeas will be high.

Evaporation climatology 1950-1979.  Notice the extremely high evaporation in chickpea-producing areas of India and central America during monsoon season. 
Did the LA Times report rely on a small and unreliable dataset (US chickpea production) or report global statistics and label them as US statistics? I don't know. Either way, their reporting is extremely suspect.

People need protein.  Plant-based proteins such as chickpeas are largely grown and consumed in regions where the resources (land, water, labor) cannot support animal sources of protein.

The water and carbon intensity of crops vary greatly by location.  That's why I don't eat an entirely locavore diet.  Our family enjoys CSA boxes grown with reclaimed water from the Irvine waste treatment plant.  But, we occasionally eat lamb chops imported from New Zealand, where the sheep are raised on rainfall-watered pasture.

Yes, sheep meat has a large water footprint.  But New Zealand has abundant rainfall and doesn't need to artificially irrigate their pastures.  If the lamb is frozen and then shipped via ultra-efficient container ships to a harbor < 15 miles from our home, then the carbon footprint of that lamb chop is much, much lower than a beef burger from the Central Valley of CA.

Early summer evaporation in the American west.  Note the hot spot in the Fresno area.
I took a closer look at the evaporation in California.  Download the data and the Panoply data viewer and play with the data yourself.  Scroll through the months.

The Willmott and Rowe data is based solely on 1950-1979 ground-based station data.  Later datasets rely on satellite data, but WR gives monthly averages, which is important because row crops are not grown year-round.

It's important to note that the evaporation measured by the ground stations are influenced by temperature, winds and water availability.  Water availability depends on both natural sources, e.g. precipitation and surface stream flow, and irrigation.

See that bright yellow hot spot near Fresno, California?  100 kg per square meter is 100 mm or ~4" of water.  Look at Fresno's climatology.  That's nearly all irrigation with water from elsewhere or  groundwater.

This is old data.  The numbers today, with millions of acres planted with permanent tree crops that can't be fallowed during droughts, would be even more scary.

This is why California's central valley is sinking.  This is a slow-motion environmental catastrophe.  It has to stop now.

Friday, May 01, 2015

Me Made May 2015 Day 1

I sat on the fence about joining Me-Made-May 2015 because I have a busy month ahead.   But, I enjoy seeing others' photos from around the world and decided to add my own.

I finished this sweater about two years ago and never got around to blogging about it or putting it on Ravelry.  It's one of my most-worn hand-knit sweaters.  Vitamin D (Ravelry link) and Malabrigo Sock Candombe if you want to replicate it.

My office, and the cool air chimney, are behind me.