17

Mark's answer about mercury barometers is correct - but it is not the complete story. Barometers were initially constructed using water, not mercury, on the manometer principle. Water is lighter than mercury, so a water barometer requires a 10.3m tube. 1mbar is therefore roughly 1cm, and 0.1mbar measurement is clearly trivial using a ruler with 1mm ...


9

A mercury barometer is a simple, easy-to-build barometer that turns the problem of calibrating a pressure standard into one of calibrating a length standard. Accuracy of length standards has long been a concern of merchants and those regulating them; in 1692, the standard would probably have been a brass prototype yard in the possession of the Royal Society....


8

The WMO report Instruments and Methods of Observation has a chapter on Measurement of humidity and a separate chapter on Measurement of upper-air pressure, temperature, humidity. The first deals with instruments used for surface measurements. The second deals with instruments used for measuring vertical profiles, which have to deal with a larger range of ...


6

We use something like an Onset HOBO electronic sensor. They've got logging (and in some cases, networking) built in. They'll typically log both temperature and relative humidity at regular intervals specified by the user. Humidity sensors have a tendency to wander off calibration, so you will need to take that into account when designing your monitoring ...


6

I don't think they are using that level of accuracy for the old readings. Reporting pressure, in hPa, to one decimal place is being done for recent measurements. There are no values given for very old readings. As for the record reading of 1053.6 hPa for 1902, I suspect that is a mathematical conversion of a reading that was most likely recorded in inches ...


5

You can use the fact that the Earth's rotation period is known. Then divide that period (use the solar day of 24 hrs 00 minutes instead of the sidereal day of 23 hrs 56 minutes) by the actual amount of time between your two solar noons and multiply the resulting factor by your 1260 km distance. The result is the circumference ... of your latitude circle. ...


5

Doing a quick calculation that looks to be around the wet-bulb temperature at the time of observation so that thermometer on the right side should be a hygrometer. Hygrometers measure the level of moisture in the air as opposed to a thermometer that measures the temperature level. Edit: The calculation was based on a recorded observation scoured from here ...


4

I'm going to go old school with this one. The following pictures are the relevant pages from: Environmental Engineering in South African Mines, The Mine Ventilation Society of South Africa, 1989, pp 451-455. They give the psychometric equations that are required to calculate relative humidity from wet & dry bulb temperatures. For simplicity, I use the ...


3

How are barometric pressure measurements traceable over centuries to 100 parts per million accuracy? To compare records of barometric temperature, this standard doesn't necessarily have to be met. Recording barometric pressure to 100 parts per million precision has been possible for centuries because it's reasonably trivial to observe movement of the level ...


3

Welcome to Earth Science SE! Given that the crisis is still ongoing, I doubt we know the full extent of the impact (forecasting the weather is hard enough, forecasting the impact of a pandemic is outside my expertise). But, at least one conference was supposed t o go to was cancelled. And I know the lack of airplane obs is impacting data assimilation. ...


3

As a very rough approximation, one could start with equation (9) from Arbab (2009), https://arxiv.org/abs/physics/0304093 to get the effective number of days per year: $$T_{\text{eff.}} = T_0 \left(\frac{t_0-t}{t_0} \right)^{-2.6}$$ with $t$ the time difference between now and then $T_0 = 365.25$ the current number of days per year $t_0=(13.799 \pm 0....


2

The Bureau of Meteorology in Australia traditionally uses wet and dry bulb thermometers read by humans, when measuring temperature. However, for remote automated weather stations, electrical equipment is used. The dry bulb temperature is measured using a resistance temperature device (RTD) and relative humidity is measured using relative humidity probe. The ...


2

If waves would travel only through a medium while keeping their form (i.e., P-waves remain P-waves and S-waves remain S-waves), you would obtain something a bit like this video: https://www.youtube.com/watch?v=YctV5crEXyM . However, standard models for wave propagation are more complicated than that. Upon hitting an interface, P-waves both reflect off and ...


2

The ECMWF (European Centre for Medium-Range Weather Forecasts) has published an article about the topic on 24 March 2020: By 23 March there was a reduction of 65% in [European aircraft] reports received compared to 3 March. Globally the reduction was about 42%. [...] In 2019 a test was run: a series of forecasts without using aircraft reports (but ...


2

Is there a project that tracks and publishes data regarding weather prediction errors on a regular basis that would help with analyzing the correlation between incoming data and prediction error? The World Meteorological Organization has several initiatives that track forecast performance. See for example here. The data is a bit delayed, as of today (Apr 5, ...


2

The mediterranian do in a way create its own climate and is partly protected from the north saharan desert by the dominating wind direction in the area. The dominating wind direction is from west and northwest,The wind blows into the saharan desert in the direction of the equator in the winter,This creates the mild winters the mediterranian is known for. ...


2

Land that has been heavily disturbed by humans in most developed countries, such as urban and rural regions will have been surveyed for topographical & sub-division purposes. Such data allows for a digital terrain model (DTM) to be created for such regions. When subsidence occurs, the subsided area can be resurveyed & compared to the original DTM to ...


1

The maximum reading was taken at Aberdeen Observatory and they still have a barometer which was in use during the period the reading was taken (the inscriptions dates it to 1888 and after 1922 it was still in use). It's not a mercury one - mercury is relevant as the article states records go back to 1692, before aneroid barometers were invented, though does ...


1

Several methods are employed to measure ground subsidence: Spirit leveling, GPS (GNSS), Remote Sensing, Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging to name a few. In the case of modeling subsidence caused by water and oil extraction, the most common measuring methods seem to be Spirit leveling, GPS and Remote Sensing (Interferometric ...


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