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Delaware National Estuarine Research Reserve


      

Of Rain Gauges & Rainfall Averages

Written on: March 3rd, 2017 in Guest BlogNERRResearchSt. Jones Reserve

To add variety to the blog and to offer a fresh perspective from our visitors, we are inviting guest bloggers to write posts describing their visits and thoughts while at the Reserve. This guest blog is Part II to December’s post by M.L. Christmas about her interview with Research Coordinator Dr. Kari St. Laurent. Enjoy! (Johanna Hripto, DNERR Assistant Education Coordinator & Blog Editor)

The interview with Dr. Kari St.Laurent, in December 2016, contained more information than could fit in any one blog. Makes sense, does it not? Weather is “big stuff,” and just like everything else in life, there is often a lot more going on than initially meets the eye.

Home sweet home-based rain-gauge! It’s functional, but not always pretty. Despite cleaning it out from time to time, this writer still finds moldering leaf bits, tinges of algae, and the occasional spider web (sometimes occupied!).

Home sweet home-based rain-gauge! It’s functional, but not always pretty. Despite cleaning it out from time to time, this writer still finds moldering leaf bits, tinges of algae, and the occasional spider web (sometimes occupied!).

The following is some “overflow” from that interview. Not to be skeptical, buuuuut…the delay allowed this guest-blogger to set out to prove (or disprove) something she had heard.

MLC: Your spikey chart is based on the Dover Air Force Base data. Though our house is just a few miles from the Base — and from the St. Jones Reserve — we often receive a different rainfall amount in our backyard rain gauge. We used to refer to the DAFB measurements for gardening purposes, but now that we have our own gauge, we feel we have a better idea what is really going on in our yard.

Checking for any obstructions (or special guests) before emptying the gauge.

Checking for any obstructions (or special guests) before emptying the gauge.

KSL: It might seem that way to you, but in fact, rainfall amounts will all even-out within a region! A single-day event can be very variable per location, but the amount of rain in one area is usually very similar throughout the region over the course of a year.

MLC (not completely understanding KSL and still stewing about the seeming inequality of it all): I have also wondered about the possibility that rain amounts in our front yard and back yard could be different! The rain/no-rain line has to fall somewhere, and might even be between us and our neighbor’s house. Installing a rain gauge out front, to supplement the one in back, might not be sufficient to give a fully accurate picture of the rainfall in our yard. I have jokingly thought that we could fill our yard solid with hundreds or even thousands of rain gauges, placed shoulder to shoulder, and still not know for sure what our conditions are.

KSL (somewhat easing the mind of the fretting guest-blogger): Think about the flow of water in your yard. A big rain that falls in the back yard is going to follow the gradient to the lowest point — a river, the ocean. Where rain falls, and where it flows, are two different things. But again, the rainfall totals within a region will all even-out.

Hindrance number 1: Keep rain gauges away from the sheltering effect of trees!

Hindrance number 1: Keep rain gauges away from the
sheltering effect of trees!

That is why the most important thing, M.L., is not how many rain gauges you might have in your yard, but how the one rain gauge you do have is situated. For ideal placement of a rain gauge, the location very much matters: not under a tree, or next to a big building where the wind goes only in one direction. A big open space, ideally, is where a rain gauge should be sited, like at an air force base.

 Dr. St.Laurent’s official, educated pronouncement should have marked the end of the matter: So much for our household’s friendly rainfall-rivalry with DAFB! Or was it still unresolved? This business about the rainfall averaging-out may sound good, on the surface, but in the interim, this guest-blogger decided to dig into her notebooks to see if she could prove otherwise.

Hindrance number 2: Keep rain gauges at a distance from homes, buildings, fences, sheds, etc.!

Hindrance number 2: Keep rain gauges at a distance from homes, buildings, fences, sheds, etc.!

Here are the stats. I crunched the numbers for 2016, based on our household notes about the rain received in our gauge versus the levels reported at DAFB. (This does not include data for weeks we were out of town or were hindered for other reasons from making a comparison.) The disparity in total rain amounts, between our yard and what was reported at DAFB, over the course of the entire year, came down to a difference of just over an inch in our backyard’s favor. That one-inch advantage might well have netted out in the aforementioned intervals for which we had no comparison-data; and putting additional years’ comparison-data into the mix might only further flatten any backyard-versus-DAFB discrepancies.

So there you have it. I could have sworn we’d have come in significantly ahead of DAFB in the precipitation department, no matter what DNERR’s in‑house meteorologist might claim. Good thing I didn’t make a wager on Dr. St.Laurent’s being wrong, or I would have been on the losing side of that bet: say, having to take a wince‑inducing, mid-winter swig from a muck-bottomed, backyard rain gauge.

 

 Text and photos by M.L. Christmas

* * * *

M.L. Christmas, MSM, is a freelance writer/editor living in the Dover area. She is a longtime member of Delaware Press Association and the National Federation of Press Women.


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