You may have noticed that at times rainfall totals in the Almanac section or History page suddenly shift, usually downward. That’s because the automatic rain gauge runs a little wet. Oftentimes, I circle back and correct the amount with what I’ve measured in the manual gauge (~ 6′ away and 3′ lower).
Well, through the wonders of technology (a.k.a. Microsoft Excel), I was able to finally calculate the error and program a correction for it. Over the last 12″ of rainfall, it’s a pretty consistent 4-8% overage. It averages out to +6.5%. So I am subtracting that from realtime readings now. I’ll keep an eye on it to see if it changes over time.
For small events, it may not have any effect whatsoever. But in larger rain storms, it should allow for fewer corrections and, thus, less confusion.
Beginning Monday July 13th the radar will be down for maintenance until sometime on or around Friday July 24th. Technicians will be swapping out the pedestal underneath the radome (giant soccer ball) you see near the old County Airport location on US-41 in Negaunee Township. See this NWS blog article for more information.
The radar is down until approximately 3 PM on Wednesday July 1st for maintenance.
Be aware that starting Monday July 13th the radar will be down for approximately 2 weeks. Technicians will be swapping out the pedestal. See the NWS blog article for more information.
You might have noticed a couple new readings in the “Current Conditions” section of our home page. I’ve installed 2 new sensors on our main weather station, a Davis Vantage Pro2, to measure output from the Sun.
One sensor reads a narrow band of ultraviolet (UV) radiation. The 290 – 390 nm spectrum of the sun’s shortwave energy particularly affects human health. Readings are translated into a universal UV index (1 – 16 scale).
The other sensor measures broad spectrum solar radiation (a.k.a. “solar irradiance”, “solar insolation”) between 300 – 1100 nm. It’s output scale is 0 – 1800 Watts per meter squared (W/m2). This is useful for solar energy management & approximating cloud cover / ambient light. You may wonder “can’t I just look out a window?” If you are in Marquette, yes. If you are elsewhere, no.
Continue reading “Here Comes The Sun”
As noted in the about page, I regularly check our sensors to be sure they are within specifications. Over the last couple weeks I have been conducting tests.
Temperature was right on. That’s typical, as our sensor is pretty bulletproof. I have a platinum RTD digital thermometer that’s accurate to within 0.1° F (best to check on a cloudy, windy night to eliminate radiation as a factor). I also have a laboratory-grade aspirated psychrometer with a dry bulb thermometer that’s extremely accurate. It’s analog, so the biggest challenge is reading between the lines. But my tests show the station’s thermal sensor is within 0.5° during the day which is quite good. There’s also a backup sensor on site as well. At night or on cloudy/rainy days, the two sensors are normally within 0.2° F. During sunny days, height (7 ft vs 21 ft) and shielding differences (active vs passive ventilation) can frequently lead to 1° differences in either direction. 2-3° differences are not out of the question when it’s particularly calm and sunny.
Continue reading “Instrument Calibrations”