Surface Temperature: Sometimes Things Are Too Simple!

Written by Dr Jerry L Krause on March 28, 2018. Posted in Current News

If you can’t explain it simply, you don’t understand it well enough.  Einstein

In (https://principia-scientific.com/dr-jerry-l-krause-how-stupid-am-i/, 1/18/2018) I wrote:

However, having grown up in northeastern South Dakota where the precipitation was commonly much less than that of Iowa, the result was that our relative humidity was usually significantly less than that of humid Iowa.  So I knew the reason for the warmer nights in Iowa was that dew generally formed on stuff there much earlier in the evening then it did where I grew up.  And sure enough this example of the greenhouse effect quietly disappeared.  And I forgot about dew.

In (http://principia-scientific.org/new-scientific-law-greenhouse-effect/, 10/3/2016) I wrote:

This elementary article could have, and should have, been written and published long ago.  The condensation of water vapor to form dew or frost on solid natural and artificial surfaces is a commonly observed natural phenomenon.  It is well understood that the latent heat released as water vapor condenses slows the radiational cooling of these surfaces during the diurnal temperature cycle.

I had written the latter essay (article) in 2014 and shared it with some Oregon State University chemistry professors emeritus whom I had known in graduate school (1963-1969).  And they told me they couldn’t really comment upon the greenhouse effect because they were not really familiar with this theory.  Except, I was sure it had been taught in their general chemistry classes from the mid-1970s because the fact was I needed to teach about it to my general chemistry classes at a community college since my courses needed to be comparable to the courses being taught at 4-year colleges and universities.

Nicholas (Nick) Schroeder (https://principia-scientific.com/climate-science-what-doesnt-work-and-why/, 3/8/2018) and Carl Brehmer (comments) prompted me to compose this essay.  Both agree that the earth’s ‘solid’ surface temperature (ST) is almost always greater than the temperature of the atmosphere (AT) measured about 1.5 meter above this solid surface.  A more fundamental problem than what Nick and Carl reason is that since 1896, when Svante Arrhenius wrote an article with the title: On the Influence of Carbonic Acid in the Air upon the Temperature of the Ground;  it seems that the AT has been used a proxy for the ST.  So this essay has an importance far beyond settling this disagreement between Nick and myself.

The day before Nick’s posting (https://principia-scientific.com/problem-earth-surface-temperature-measurement/, 3/7/2018) I had written:

The U.S. Climate Reference Network (USCRN) is a system of climate observing stations developed by the National Oceanic and Atmospheric Administration (NOAA).  Its 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.

In addition to the primary air temperature and precipitation instrument sets at a level of 1.5 m, a USCRN station also observes surface skin (radiative) temperature, incoming global solar radiation (at 1.5 m), atmospheric relative humidity (at 1.5 m), wetness due to hydrometeors (at 1.5 m), and a 1.5-m-level wind speed.  The soil-probe configuration is designed to obtain three independent samples of soil moisture and soil temperature for each instrumented soil depth (5, 10, 20, 50, and 100 cm).

Nick’s claim is that the ‘surface skin (radiative) temperature’ cannot be measured because a variable (emissivity) of the Stefan-Boltzmann Radiation Law (S-B Law) is a property of the emitting surface.  Which (the emissivity) in the case of earth’s surface would seem to be very variable from location to location and from season to season and even from day to the next (no snow surface one day and a snow surface the next).

The dates of the postings are important because I was well aware, before Nick’s posting, of the problem of measuring the earth’s surface temperature (ST).  And I have often commented that I am slow and I wanted to document this fact.

I had only recently (maybe a month earlier) learned about the USCRN project and its data which had been available since about 2010.  And I had only recently (maybe 2 years earlier) learned about the US Department of Agriculture’s project titled Soil Climatic Analysis Network (SCAN) and its data (https://www.wcc.nrcs.usda.gov/scan/) which had been available before 2000.  And I had only recently (maybe 5 years earlier) learned about NOAA’s Surface Radiation (SURFRAD) and its data which had also been available before 2000.  A good question is:  Why had I not learned about these three projects and their data earlier?  My answer:  I never read about it so I conclude that the data was hardly being considered and written about by anyone.

So, in this brief essay the reader can read what I have simply overlooked for a couple of years.

Figure 1.  Atmospheric Temperature and Dewpoint Temperature at SCAN site at Essex CA (34^o  40’ N; 115^o 10’ W) 6/22/2014

Figure 2.  Atmospheric Temperature and Dewpoint Temperature at SCAN site at Goodwin Creek  Pasture MS (34^o 15’ N; 89^o 52’ W) 6/23/2014

Figure 3.  Soil Moisture Content at SCAN sites Essex CA (6/22/2014) and Goodwin Creek Pasture MS (6/23/2014)

A comparison of the soil moisture contents at the two sites (Fig. 3) explains the differences seen by comparison of air temperatures and dewpoint temperatures of these two sites (Fig 1 and Fig 2).  Which specific differences that I consider are important are the changes of air temperatures (AT) between midnight and 5am and the values of the dewpoint temperatures (DPT) relative to the values of the air temperatures.

It is easy to see (Fig 1) that the minimum AT between 12pm and 5am is much greater than the maximum DPT during this period.  So, no condensation of water vapor to dew can be occurring.  While, it is easy to see (Fig 2) that the value of the AT is about that of the DPT during this same period so we must consider that condensation of water vapor to dew is likely occurring.  For there could be a question, if we study Figure 2 carefully, we can see that the ATs are slightly less than the DPTs.

But better is to go to the SCAN site and consider the precise numbers of the data file for this day at this SCAN site.  For, this small difference is important to Nick’s and my disagreement.  The DPT is less than the AT during this specific 5 hour period.  It is important because the USCRN project is very similar to the SCAN project except for the greater effort of the USCRN project to validate the measurements being made during the previous hour of the data; which are only recorded on the hour for both projects and for the measurement of the surface skin (radiative) temperature.  The USCRN project does measure relative humidity and the AT, from which the DPT can be calculated (and this calculation cannot be questioned by Nick).  Thus, during the period between midnight and sunrise at USCRN sites, the measured surface temperature can be compared with this calculated DPT.

Which I do not do here because the SCAN data at Goodwin Creek Pasture on 6/23/2018 already refutes Nick’s claim for a 5hr period of this day and this has nothing to do with the emissivity of the surface.  And I know (private communication) that he has plotted figures for several days which illustrate that the USCRN measured surface temperatures are slightly less than the measured air temperatures for a period much greater than 5hr.  Which I do not have the skill to do.  So, I would hope he would share such figures with the readers of PSI.

However, in closing, I do share the soil temperature data measured at depths during 6/22/2014 at the Essex SCAN site.  And ask the question (with the caution:  the maximum and minimum soil temperature is that at a depth of 2in and not the surface temperature):  Do you think that air temperature is a good proxy for the surface temperature?

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