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Temperature gradients at Skerries

Using two thermo couples (TC) and a thermometer (Signtek 6802 II, which can measure the temperature difference) the temperature gradient was measured for a few days near a house wall. The height of TC2 was at around 0.85m (from a cement surface and hanging in plants) and TC1 was at a height of 3.65m, 2.8m above TC2. The TCs were some 50 cm from the house wall. The house wall could reflect heat or be a heat sink/source. No cars or people can get near the location. The TCs are not aspirated and are not protected from rain and Sun's irradiance on the TC by using for instance a gill setup. This is planned to the near future, using this method.
If the Sun is visible, it can touch the TCs between Sunrise (around 6:30) and 4 hours later when the Sun goes behind the house (until around 10:30). In most instances clouds were though present.

Weather information near Skerries, Ireland (Dublin airport is some 20km to the South) can be found here.

Make sure one understands the ins and outs of TC measurements. A good introduction on TCs and their errors, please read here and here.

So this is not a free standing environment (which might be needed for a 'laboratory' circumstance). But this setup might also provide an idea of the variability and a real live situation near an ancient monument.

The measurements

Some 80 measurements have been done over six days at Skerries, Ireland (some 400m from the Irish sea).
The minimum, maximum and averaged temperature differences (T1 - T2) were derived over a period of at least 10 minutes. The aim was to measure every hour, but due to work and sleep this was not always possible. The average values within this period of 10 minutes are quiet stable  (so no real drift). The difference between minimum and maximum value have been used to give an idea of the error: assumed to be a difference of 6 sigma.
From these temperature values, the temperature gradients are derived (divided by the height difference [2.8m] and times 100m). The temperature and the average temperature gradient (including 1sigma error bars) are provided in below picture (grey areas are night times):
Temeprature Gradient at Skerries house

Other atmospheric parameters (pressure, wind speed, wind direction and humidity) are recorded as per Wunderground's Dublin Airport data. The cloud cover, cloud height and temperature at the location and moment of observations are also recorded. This makes sure the important parameters around boundary layers and NRI Stability Classes are available.

Some points that came up during the measurements:

Comparison with other sources

Below are the temperature gradients seen in other sources:

Comparign difference sources of lapse rate measurements

In the label the location is mentioned first in each row:
 After the location, the highest height used to determine the temperature gradient is given (e.g. 7.6m for Thom's).

The lower the highest height (normally meaning a smaller height difference for measurements): the larger variation of temperature gradient will be, e.g. Skerries (e.g height difference 2.8m).
Sites that are in a warmer climate have a tendency to have larger variations: e.g. Ismailia under same height difference.
After the height, one can see if the bar is showing the min&max values (100%), the averaged/smoothed or with bottom&top 5% removed (90%).
It looks that averaged, smoothed and 90% have similar values. The 100% bars have a higher variability: compare Ismailia 100% and 90%.
Also interesting to see that sometimes the positive gradient is larger than the negative gradient (depending on location, height and/or sample).

Conclusions

The Temperature Gradient varies between -22 to 50 [K/100m] in Skerries Ireland in the month August. Again this is not a laboratory environment (near a wall and a small height difference) and it is only over a period of a few days. The variation though is not that far off compared to other measurements. The temperature gradient near sunset and sunrise looks to be close to the expected value of around 2.5 K/100m and a wind speed of around 2 to 4m/s (Stability Class E).

Temperature profile seen by the light: the RPTP  Profiler

This section is move to where it belongs.

References

Flower, W.D. 1937. 'An investigation into the variation of the lapse rate of temperate in the atmosphere near the ground at Ismailia, Egypt.', Geophysical memoirs, Vol 71.
Johnson, N.K. 1929. "A study of the vertical gradient of temperature in the atmosphere near the ground." in Geophysical memoirs, Vol 46. Meteorological Office.
Knoch, K. 1909. Ein Beitrag zur Kenntnis der Temperatur- unde Feuchtigkeitsverhaltnisse in verschiedener Hohe uber den Erdboden (Berlin: Springer-Verlag).
Reijs, Victor M.M., 2017a, "Geniet: Thom's terrestrial refraction observations", http://www.archaeocosmology.org/eng/Thom-refraction.htm
Reijs, Victor M.M., 2017b, "Geniet: Temperature gradients at Skerries", http://www.archaeocosmology.org/eng/TempGradientSkerries.htm
Thom, Alexander. 1956. "Notebook.", MS/430/64, Edinburgh: Historic Environment Scotland.
Thom, Alexander. 1958. 'An empirical investigation of atmospheric refraction', Empire Survey Review, Vol 14: pp. 248-62.

Acknowledgements

I would like to thank people, such as Marcel Tschudin and others for their help and constructive feedback. Any remaining errors in methodology or results are my responsibility of course!!! If you want to provide constructive feedback, let me know.
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Major content related changes: August 30, 2017