Thursday, June 23, 2016

Corn in the backyard, 2016 -- weeks 6, 7, & 8

June 5

The week before June 5th was warmer each day than the historical average, accumulating 34% more heating degree days than normal. The plants cooperated by leaping up to 24 inches tall on average, which is about average for this time of year, and consistent with 2010 when the planting date was about the same as this year.

You may have heard the phrase, "knee-high by the Fourth of July" when referring to corn growth. In our backyard, the knee-high phase is typically passed by the Fourth of June, as was the case this year. Here's photographic proof.

June 12

The week prior to June 12 saw five of the seven days average warmer temperatures than the historical average, but rainfall only managed a trace.  Heating degree days totaled 23% more than average and the corn plants continued to match historical norms by reaching 40 inches tall.

June 19

I wouldn't say the corn plants looked bad on June 19, but continued hot weather with minimal rain showed its effect on the grass in my yard, and the corn around it. You'll notice the leaves have a slightly spiky appearance that is the result of dry, hot weather as the plant attempts to conserve moisture. All seven days of the week were warmer than average, resulting in 31% more growing degree days than normal, while the plants continued to grow at a normal pace, reaching 57 inches tall.

The other item worthy of note is the fact that the farm across the highway is barely visible now, and the vehicles on the highway are fully hidden from view.

Monday, June 20, 2016

A Simple Family Tree

Is there any object in your house that makes you smile every time you look at it? Several years ago, Karen found this tree and we gathered photos, made copies in appropriate sizes, and populated the frames as you see in these two photos. Even though I've been looking at these photos almost every day for years now, I still find joy in the beauty and memories captured in this project.

Karen's side includes a darling picture of her as a preschooler at the top, and images of her parents immediately below revealing her mother as a huggable toddler, and her father sporting an impish grin that was probably well known to his parents. Karen's grandparents are on the next row down, both shown in their wedding photos. At the bottom, Karen's father's maternal grandparents are pictured in their engagement photo on the left while Karen's mother's paternal grandparents are shown in a semi-candid shot later in their marriage.

My side of the tree includes a shot of me as a preschooler at the top, and photos of my parents as teenagers just below mine. We included my mother's parents' engagement picture on the next row, along with the wedding picture of my father's parents. The bottom row has two candid shots, showing my mother's maternal grandparents on the left and my father's paternal grandparents on the right (an image that has graced this other post on this blog).

It's probably good that the tree doesn't have four frames on the bottom branches as I'm not aware of any photos of the great-grandparents that are missing from the tree now. I only have recollection of one of my great-grandparents, and since Karen and I both lost at least one grandparent before we were born there are plenty of people on this tree we've never met. Nonetheless, my heart is warmed by this reminder of the people that have made us who we are.

Wednesday, June 1, 2016

Corn in the backyard, 2016 -- weeks 4 & 5

May 22

The week leading up to May 22 was quite a bit colder than normal, and recorded a bit more than half the historical average for growing degree days. Consequently, the plants only grew a couple inches that week. Special thanks to my trusty assistant, Lily, for taking photos for me while I was out of town on the 22nd.

May 30

The next week turned warmer and provided decent rain such that the plants sprouted up to 15 inches tall while enjoying 49% more growing degree days than average. Like most years, it appears that the plants won't have any trouble reaching knee high by the fourth of June.

Wednesday, May 18, 2016

Does the Wind Affect MPG?

Cars today are so powerful that we rarely notice winds as we hurtle along at highway speeds, but believe it or not, your vehicle uses more fuel driving into the wind versus driving through calm air. Need proof? I believe the data below can prove it.

A Little Overview
Previously, I shared my evidence that air temperature affects fuel economy, and my evidence for wind speed comes from the same source. I've recorded the miles per gallon (MPG) I achieve on my commute to work each morning, and combined that data with wind speed measurements recorded by weather services reporting on the internet. Bear with me as I try to show the correlation I think is evident in the data.

The Simplified Analysis
This first chart compares the wind speed reported by a weather station in my area with the MPG recorded by my car. As you can see there's no real correlation between fuel economy and wind speed. What's missing is the direction of the wind relative to the car.

Intuitively, we expect a headwind to lower fuel economy while a tailwind should increase it. Without a directional component to the data, it appears to be random, and one might conclude that fuel economy is independent of wind speed.

Fortunately, the wind speed data sources used for this analysis include the direction of the wind. Given the wind speed and direction, the resultant direction of my commute based on the start and end points, and the average speed of the vehicle, we can calculate what I call the "Average Relative Headwind Speed." In simple terms it's the average speed of the air striking the car as it traveled over the entire commute, and combines the effect of the wind speed with the speed of the car.

This plot shows a stronger trend than the first plot, indicating that as relative headwind speeds decrease, fuel economy increases. You might also notice that it's difficult to represent the trend with one simple curve (shown here as a solid red curve). I believe that's because fuel economy is dependent on other factors besides wind speed, or temperature for that matter. In a future post, I'll try to combine all these factors in a way that better represents the connection between multiple weather conditions and fuel economy.

More Details on Assumptions, Methods, and Data
As I mentioned earlier, this data was gathered while commuting to work each morning in my 2013 Volkswagen Passat TDI SE which has a diesel engine and manual transmission. The MPG readings were provided by a dashboard monitor that computes average MPG over the course of a trip. I don't know how VW programs that calculation, but presumably it's a function of distance traveled and fuel flow to the engine.

The data presented here was gathered between February 9 and July 2, 2015 so that the date range matches my previous post, Does Outside Air Temperature Affect MPG? In that post, I noted that the route was consistent each morning until April 2, when road construction added a detour that included a longer 45 mph zone each day until the end of the data period. I've continued gathering data since then, so more data is available and will likely be shared in the future. As traffic and road conditions allowed, I attempted to maintain the same speed on each section of road each day, and tried to make my accelerations and braking consistent between commutes. Because I commute before 6 AM, traffic rarely interfered with my ability to maintain a consistent pace.

The direction of my route is simply based on a straight line drawn between the start and end points of my commute. The angle of that line relative to true north was calculated, and compared to the average wind direction during the commute to determine the angle of incidence with which the wind struck the car. Wind speed and direction were gathered from weather stations reported on, and chosen for their proximity to my route and ability to reflect the conditions my car experiences.  Unfortunately, winds can change speed and direction over the course of a 40-minute drive, so without more sophisticated ways of recording and calculating based on those changes, my results will suffer some amount of error due to this variation in the wind. I'm sure that shows up as some of the scatter in the data, but I don't currently know how to estimate that effect.

The Average Relative Headwind Speed (ARHS) was calculated by representing the car's average speed and direction as one vector, and the wind's speed and direction as another vector. The vector resulting from adding the two is the ARHS. When both vectors are pointing the same direction, the magnitude of the resulting vector is simply the sum of the two. When my car is driving directly into the wind, the magnitude of the ARHS is the difference of the two. Any angular difference in the direction of my car and the wind requires some trigonometry to achieve the ARHS.

The polynomial trendline shown on the second chart above was calculated by Microsoft Excel, and I chose a second-order polynomial because I know the force of the wind on an object is directly related to the square of the speed of the wind. I think fuel economy is probably linearly related to that force, so approximating the relationship between fuel economy and relative wind speed as a second-order polynomial made sense to me. I've wondered about the effect of the outliers on this approximation, but I'll leave that analysis for another day.

The effect of wind speed on fuel economy is evident in the data. The scatter in the data is greater than I'd desire, but likely exists because (a) my analysis ignored a variable(s) that also has a strong effect on fuel economy, and/or (b) my assumptions and measurement methods are too general. I am pleasantly surprised that the data shows the basic shape of a second-order polynomial, even if the coefficient of determination is rather low.

The next time we visit the MPG topic, we'll look at the effect of water on the road, and possibly some conclusions based on multiple variables.

Related post:
Does Outside Air Temperature Affect MPG?

Monday, May 16, 2016

Corn in the backyard, 2016 -- weeks 2 & 3

May 8

Although we had a generous amount of rain leading up to May 8, we accumulated about 20% fewer growing degree days than normal for this time of year.  Nonetheless, the corn plants grew to 2.5 inches, maintaining a reasonable pace, albeit slower than most years.

 May 15

For the week prior to May 15, our rainfall was adequate, and growing degree days were very close to average, resulting in growth that put the tallest plants at about 5 inches. Historically, that's below average for the third week's measurement, but about average for the middle of May. No reason for concern yet, especially considering the temperatures have been so cool.

The May 15 photos also prove that our days have not all been cloudy this spring.