The Corvallis, OR. USCRN Site: A Natural Laboratory: Part Four

Written by Dr Jerry L Krause (Chemistry) on December 7, 2018. Posted in Current News

Previously someone criticized my figures of the data which has been measured at this Natural Laboratory.  But this comment was not made to any of my essays and I am too lazy to search for it to credit this person for being correct.

I discovered this problem while trying to explain something in these figures whose scales prevented the observation of details.  And details can be critically important as noted by my favorite meteorologist R.C. Sutcliffe.

“All this may seem a far cry from the general circulation of the world’s atmosphere but the detail serves to point the moral, that one cannot explain the broad features of world climate if one does not know the actual mechanisms involved.”  Weather & Climate

“The U.S. Climate Reference Network (USCRN) is a system of climate observing stations developed by the National Oceanic and Atmospheric Administration (NOAA). The USCRN’s primary goal is to provide long-term temperature, precipitation, and soil moisture and temperature observations that are of high quality and are taken in stable settings.” (https://www.ncdc.noaa.gov/crn/overview.html)

If you read further you will find the efforts taken to make this project’s measurements of the highest quality.  They measure the air temperatures at about 1.5 meter above ground with three independently air aspirated temperature sensors so that the environment of these sensors is not being warmed by the solar radiation.

Relative to these three independent sensors, three temperatures are reported for the preceding hour—the average (mean) temperature, the maximum temperature measured, and the minimum temperature measured.

The latter two temperatures are unique because they are the only actual temperatures measured.  Averaging the temperatures measured during the preceding hour is a necessity because the temperatures naturally increase or decrease over a significant range most hours.

However, these actual temperatures allow us to see if the atmosphere is cloudless, or not, during the preceding hour.  For when the atmosphere is cloudless (or uniformly cloudy) and the temperature is increasing, the maximum temperature becomes the minimum temperature (or within a degree) of the next hour and the reverse is the case when the temperature is decreasing.

During the two hours when the transition between increasing and decreasing occurs, neither is the case.

Back to averaged temperatures, the three averaged temperatures are then averaged (as I understand it) to create a ‘super’ averaged temperature for that hour.  This is done (as I understand it) to accomplish two things.

One, to begin to establish a long term trend of average air temperatures measured near the surface such as exist as measured from space for the USA land area.

Two, to possibly validate the long term trend of averaged air temperatures as measured from space.  Happily someone convinced the designers of this project to measure the temperature of a surface as devices (infrared thermometers) became available.

These surface temperatures are measured and reported in the same way the air temperatures, except there is only one instrument.

However, as already reviewed (Part Two), a most important fact about this Natural Laboratory is there is a second FWS (Fish and Wildlife Service) RAWS (Remote Automated Weather Station) weather station, about 50 feet from the USCRN weather station with a device, termed a fuel stick, which measures the mean fuel temperature and the mean moisture content of the stick’s interior for the preceding hour.

For more background about this Natural Laboratory go to Part One (https://principia-scientific.com/the-corvallis-or-uscrn-site-a-natural-laboratory/), Part Two (https://principia-scientific.com/the-corvallis-or-uscrn-site-a-natural-laboratory-part-two/), and Part Three (https://principia-scientific.com/the-corvallis-or-uscrn-site-a-natural-laboratory-part-three/).

We begin, as we did in Part 1, with figures of data for you to read.    However, in this case I will follow these figures with what I have read and my explanations of it.

We begin with Figure 1 to show the limits, to which the average air temperatures are constrained by the actual measurements of the maximum and minimum temperatures when the atmosphere appears to be cloudless.  This documents the quality of the USCRN data.

In Figure 2 we see the agreement between air temperatures measured by two different temperature sensors at two different weather stations.  Which agreement is better than that between the maximum-minimum temperatures of Figure 1.  This reproducibility documents the quality of both stations’ data.

In Figure 3 we see the general agreement between the Surface Temperature and the Fuel Temperature, except near their maximum and minimum temperatures as measured by two different devices of two different things.  One thing the interior temperature of the fuel stick about 1 foot above the ground and the other thing is the surface temperature of the ground with the sparse grass growing on it.  If we look back at Figure 5 of Part One and see that the maximum temperature of the soil at the 5cm soil depth is about 15^oC, it is simple to explain how the FT is greater than the ST. and its minimum temperature is about 10^oC, it seems obvious that during midday the surface is being cooled by the soil beneath it.

However we cannot not use the same simple reasoning to explain how it is that the FT is still greater than that of the ST during the nighttime.  So, while I do not forget this unexplained problem, we move on to Figure 4 in which we add the dew point temperature (DPT) calculated from the AT and relative humidity measured by the RAWS station at 1.5m above the ground to the ATs of Figure 2.

In Figure 4 we can plainly see that the DPT rapidly increases a little after sunrise from its minimum value a little before sunrise to eventually achieve its greatest value of the day.  At some time, maybe little before sunset, the value of the DPT begins a steady decrease so that the ATs never cool below the DPTs.  For as I reviewed in Part 2, it is a scientific law that the atmosphere has never been observed to be supersaturated with water vapor.

The consequence of which is the atmosphere’s temperature can never cool to below its DPT.  Which, to repeat, is exactly what we see in Figure 4 .

But we see something else which I consider important.  It is that during the four last morning, the values of the ATs and the DPT, shortly begin to rapidly increase together for  together for about 3 hours.

I consider that the steady decrease in the values of the DPT in the nighttime is evidence of the formation of dew and the rapid increase of the values of the DPT after sunrise is evidence that the dew, or frost, is being evaporated by the solar radiation in the morning.  As I had considered in Part Two.

In Figure 5 the DPTs are added to Figure 3.  It is easy to see that the STs and FTs cool to and cross below the DPTs.  As this crossing occurs, we see that the DPT begins its steady decrease which we have just noted in the case of Figure 4.

We have only one more thing to explain:  How is the FT greater than the ST from sunset, or even before, until after sunrise?  In Figure A Part Two, we see evidence that the water vapor diffusing into the fuel stick’s interior during maybe the afternoon, begins to condense.

Thus, the latent heat of condensation slows its cooling by thermal conduction to its (the fuel stick) colder exterior.  But there is a problem with this explanation because I have not considered surface and the warmer soil just beneath it.

Nor have I considered the decreasing value of the DPT during the nighttime.  Which consequence is that the water vapor’s pressure is decreasing during the nighttime as the dew is formed.  I almost forgot, it is DPT at 1.5m which is decreasing.  And I forgot that the minimum air temperature, measured at 1.5m above the surface is about 3^oC greater than that of the ST.

Hence, a simple answer, as to how the FT is greater than ST, is there must be an atmospheric temperature difference between the ground and 1.5m.  Hence, this would simply explain how the fuel stick at 1foot above the ground should (could) be warmer than the ground’s surface.

The latter seems to be my best answer at this point.  Be glad to read anyone else’s answer that they consider to be better.

I close with this figure to show that the general agreement seen previously between the mean surface temperatures and the fuel temperature was fortuitous, even if it was real.

My explanation for the difference seen here is due to the lower temperature of the soil at 5cm depth and its relationship to the surface temperature 5cm above it.  Hence, we can see the seasonal climatic influence of the soil’s storage (trapping) of sensible heat upon the air temperature; which air is contact with the ground surface.

And we can see that the air temperature is not a significant influence upon the Fuel Temperature of an artificial device which is not in direct contact with the surface (soil).

And we can see that one can learn more if one continuously studies the actual data. (https://www1.ncdc.noaa.gov/pub/data/uscrn/products/hourly02/2018/CRNH0203-2018-OR_Corvallis_10_SSW.txt) and (https://wrcc.dri.edu/cgi-bin/rawMAIN.pl?orOFIN)

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