Showing posts with label rain gauge. Show all posts
Showing posts with label rain gauge. Show all posts

Monday, September 3, 2018

When a Kansas drought ends....

...it really ends.  If you've been wondering where I've been, I've been in Garden Depression-land, with only time to spare on weekends for watering everything that I didn't want to die.  It has been bad between the drought and the winds that took out several trees in my yard, among them my beloved ornamental Red Peach tree.  The only bright-side of my summer has been that I only mowed once from mid-July to late August.  Dry grass is tolerable when the mowee, i.e. me, doesn't have to sit on a roaring lawn mower for several hours each week.  


Two weeks ago, I happened to look in the local newspaper at the weather snapshot, to find out that, as I suspected, around 12+ inches of rain had fallen in Manhattan this year and we were 10+ inches lower than average.  So we had half our normal rainfall and all of our normal hot July temperatures by the middle of August.  I have been collecting weather radar pictures of storms going north and south of us all summer for the purpose of blogging about it, but couldn't bring myself to include you in my depression.  

And then, surprisingly, it started to rain.  Yes, here, in the Flint Hills!  In the past two weeks, we had several 2-3 inch rains that probably totaled 10 inches so I thought we were back on track, although the paper yesterday said that we were still 6 inches behind normal.  I forgot that annual rainfall is a moving target but at least we were catching up.  Suddenly everything is green again and I've had to mow weekly the past two weekends.
But last night the skies fell in!  From midnight to 6 a.m., the rain overwhelmed all my gauges, including the 5" gauge in the front landscaping on the blue hummingbird pole (2nd picture from top) and the 7.5" gauge in the back of the house at the top right. If you can't tell tell from the pictures, both are filled to their rims.   I have no idea how much rain we really had.  The pots with plugged drainage holes, above and to the left, also filled up to their brims, but at that point they were probably splashing out more droplets than were staying in them.  So your guess is as good as mine.  All this water was dumped into what is known as the "Wildcat Creek Basin," flooding an apartment complex, the town soccer fields, and a shopping center on the west side of Manhattan.  We even made the national NBC news tonight!  And now, some chances of rain are forecast 6 days of the next 7.  Can somebody please control the spigot better?

So, I'll try to blog from time-to-time again, since I have a garden and it seems to be green in places.  But I might get caught up in a whole series of new experiences.  For example, this morning, as I walked from the front yard around the house to the back, I was hearing the sound of a waterfall.  Waterfall>? Wait, what?  And then I realized; my neighbor's pond, which doesn't hold water and has been dry all summer, had filled up and was overflowing around the edge.  I, of course, rushed inside immediately to tell Mrs. ProfessorRoush that I had finally gotten her the garden water feature she's been wanting!
Incidentally, I thought about titling this blog entry, "When it rains, it pours."   Too cliche though, right?


Thursday, May 4, 2017

Yes, Size Matters...

...for rain gauges, anyway.  I have no experimental data regarding other subjects.

ProfessorRoush has always been a purchaser of those little cheap 1 inch diameter rain gauges, both for price and for their ability to be mounted easily to a post.  I always wanted them cheap because, as often as not, I leave them open-side-up a little too long and lose one to frozen shatterage nearly every year.  For ages, I had one down at the garden and one up by the house, the nearest for convenience on cold rainy spring mornings and the farthest because the rain in Kansas is so spotty that I thought the second often might have differing readings (though it doesn't).

Then, a couple of years ago, I purchased a 2 inch rain gauge that stuck into the ground on a little metal stand (pictured at left) and I immediately noticed that it commonly registered more rain than the smaller gauges, sometimes double the amount of rain.  What the heck, an inch is an inch in regards to rain, right?

Recently, on an experimental whim, I purchased the rain gauge pictured at the right below this paragraph, which is about halfway between the two previous sizes.  And in the recent rains over several days, the tally was; Biggest gauge, 3.4 inches, medium gauge, 2.7 inches, and two small gauges, 2.1 and 2.2 inches respectively.


What I neglected to previously consider was that rain never falls straight down in Kansas.  It commonly sweeps in at a 30º angle to the ground.  Sometimes, it seems to be completely horizontal and never actually reaches the ground, or thereabouts.  I'm pretty certain that if my face didn't sometimes intercept the path of rain, those individual droplets might make it as far as Missouri before they fell.  So a simple explanation might be that some of the rain is hitting the side of the gauge instead of dropping into it.

Of course, any decent mathematician would have calculated in seconds that the area of a 1 inch circle is πr², or 0.785 square inches.  Held at a 30º angle to oncoming rain (and estimating by eyeball), the apparent opening of the now ellipse is 1 inch X 0.6875 inches.  The formula for the area of an ellipse is πab, or π(semi-major radius)(semi-minor radius).  In this case, that is π(0.5)(0.3438) = 0.54 square inches.  The same amount of rain just doesn't have the same target area, so the gauge doesn't fill as much.  Voila!

Of course, the real "angular diameter" of the gauge to rain that falls at near subtornadic velocity has a more exact formula  (δ=2 arctan(d/2D)), but then you get into arctans and deltas and other things that I don't want to spend time relearning. I'm still confident enough to put the validity of my crude explanation and estimates of rain depth up against the likely validity of a specific 20-year future climate change prediction by any scientist, "settled science" or not.  Bigger IS simply better, regarding rain gauges, and I'm sticking to it.

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