Topic: Barani: too good to be true...

[Meteorology fan]

@ Jasper3012 - You will also often have a higher temperature on Apogee near heat emitting sources than on a passive shield. This is natural, because it is due to the reaction time in such a situation and we have tested this.  The passive shield averages this out.

Colleagues what have Apogee TS100 check Davis FARS24H in direct confrontation. As for the side overshoot, side overshoot will occur most days of the year in continental climates.

Today you can see that Apogee has a higher maximum temperature than Davis FARS24H. I would not suspect Apogee of overheating under these conditions. Note the WS90 (small passive shield) and you can see perfectly how it overheated. These are readings from the SHT35 without filters, but there are parallel measurements on loggers with PT1000 4-wire and calibrated.

Here's one of the Apogee vs Davis side-by-side comparisons on the SHT35 without filters.

https://www.ecowitt.net/home/index?id=122831

Each cover has advantages and disadvantages. Hence, he recommends measuring passive shielding (good grade and WMO compliant) and active shielding such as Apogee TS100 and Davis FARS24H.

[Jasper3012]

I acknowledge that this effect will occur much more frequently in continental climates with more sunshine and weaker wind, but even here, once the sun rises higher in the sky and the maximum temperature is achieved, you won’t see this effect. It’s only really in very specific climates and locations where this effect will have a significant effect on the min/max and this over a longer period of time.

[Meteorology fan]

Yes, that's why we see it more often in Poland. Especially in autumn and winter. This disqualifies this cover for climate and long-term studies. It can stay comparatively.

In winter and autumn, with a long period of lingering solar highs, such overestimation can take place for many weeks, projecting daily, weekly and monthly averages. This is a serious problem. This is exacerbated further as snow lies and we have a considerable albedo. Hence, a better choice for studying climate is the Stevenson cage. It may have a different time constant, but it is not sensitive to what Barani is. During frontal transitions, it responds a few minutes faster than the Stevenson, but still the Apogee TS100 is faster than it, even at moderate rotation speed.

I myself have seen Barani in winter and autumn during high and sunny weather show a higher temperature by 2 degrees compared to Apogee TS100 and Davis FARS24H. It can be shocking that during the coldest season the Barani dial at low sun angle can generate such a large error and it happens more often than in summer.

Then I spoke with friends from the state meteorological service and showed charts from colleagues and they decided that such an error is unacceptable when measuring temperature.

I also noticed that the Barani responds slightly faster during the passage of storm fronts relative to the Davis FARS24H. By about 0.2/0.3 deg.C at the passage of storm fronts. Apogee after testing colleagues is faster than Ms Pro III and Davis FARS24H among others in such conditions. Stevenson's cage will respond much later.

[Jasper3012]

Happy to be proven wrong, but I’m pretty sure even in Poland there won’t be a significant overestimation for weeks on end. Maybe somewhere in Siberia, but not Poland.

[Meteorology fan]

It all depends on the atmospheric circulation and the number of days with anticyclone. Last autumn and winter in some regions of my country Barani showed too high for about 10-20 days in the maxima. It was especially bad with the influx of continental and Arctic air masses and sunny weather with weak winds. And when it snowed on top of that, all the plastic shields knelt down and showed a strongly incorrect temperature in relation to the WMO cages and active shields. High albedo in snowy weather doesn't serve passive shields either, and when this is compounded by weak winds, we have a massacre. Barani then fared little better than competing passive radiation shields.

[Meteorology fan]

A hot summer afternoon and the wind speed drops to about 1 m/s in gusts. The Barani Gen III overheated at this point by 0.8 degrees to the Davis FARS24H on SHT35. This is what it looks like on SHT35. I will confirm this further on the calibrated PT1000s in two shields.

A PT1000 is operating simultaneously with the SHT35 in each of the shields. The Barani Gen III overheated by 0.7 degrees C in the afternoon in light winds on sensors PT1000.

PT1000 Davis FARS24H, June 21, 2024: 16:45:00 - 27.77 deg C

Barani on PT1000: 21 Jun 2024 16:45:00 - 28.44 deg.C

[Jasper3012]

That's pretty significant but at the same time very insignificant if it's actually cooler than the Davis with the max 95% of the time... One day of overheating won't do much to the measured long term averages.

[Meteorology fan]

Jasper3012 - this is not quite true. Two days earlier the Barani Gen III overheated again during the summer weather. SHT35 snapshot below, I confirmed it on PT1000 4-wire. Remember that in the case of Barani, the lower temperature is not always true. I think there will be more such periods with significant overheating this summer, and it will depend on wind speed and sunshine strength. At the time of yesterday's overheating, there were gusts of about 1 m/s, but what if there had been total calm, Gen III would have overheated by up to 1.5-2.0 degrees. Note that the situation yesterday and two days ago projects not only the instantaneous measurements, but also the maximum measured values. It happens in the afternoon, when it knocks out the daily peaks around 3 - 4 pm in my climate. The sun goes lower and lower and warms the largest area of the cover, which correlates with the weak wind.

The results from a few days ago, when the Barani fell again. In addition, the side radiation and weak wind did not serve him in the evening. It overheated steadily by about 0.5, sometimes 0.7 degrees during this time.

This shield needs a strong flow, otherwise it gets a stagnation of warm air and no helix will help here, when the wind oscillates around 0.5 m/s - 2 m/s and we have strong sunshine and unfavorable sun angle. Then it becomes a toy at Apogee TS100 and Davis FARS24H.

[Jasper3012]

The lower temperature in the Barani is, beside maybe 0.1-0.2C, true and I’ve explained why about a thousand times now… And I’m not sure what’s not true about my statement? If you look at 1 month for example, if you have 28 days where the Barani is 0.2C cooler and then 2 days where it’s 0.5C warmer, the Barani will still have a lower mean max if you simply do the maths… I haven’t updated my sheet in a while but if I suddenly added 2 days where the Barani is 0.5C warmer, it won’t undo the 30+ days where the Barani averaged 0.28C cooler. For the effect you describe to have an actual impact on climate stats, this would need to occur over multiple days to even weeks and this is simply not going to happen in our climate, maybe slightly more where you live but still not significantly so.

[hmderek]

I constantly see comparisons between active and passive shields. Surely important, but shouldn’t the more interesting comparison be between passive shields? All passive shields overheat. My Baranis consistently do so below 0.5 m/s in high sun, but this is no surprise. The question is how it then compares with other passives, and the Barani does very well in that battle. At least in my location.

[Meteorology fan]

This is important, because on the active we will find out when the covers overheat without active ventilation. For me, it's a comparison and I know when what's happening. I will not give up the passive and leave the active alone because of the risk of failure of the fan, for example.

Apogee TS100 also in windy conditions can show a higher temperature than even Davis FARS24H. This may even be due to the response time. In windless conditions, the Apogee TS100 can be cooler than the Davis FARS by 0.1/0.2 degrees relative to the TS100, as colleagues have already verified. Then the passives are overheated by 1-1.5 degrees.

I am interested in the actual or close air temperature. And not the shield temperature, but the air temperature in equilibrium with the outside temperature. In my valley often flow problems and Barani extremely often overheats. In the Belgian and Dutch climates, there may be fewer such days, due to higher wind speeds.

The worst thing about the Barani Meteoshield Pro III is that it shines from the side and overestimates by up to 1-1.5 degrees when the wind blows weakly around 1 m/s. This is a serious flaw in this shield that J. Barani does not talk about. We checked and the WMO Screnn does not suffer from it. Apogee TS100 doesn't either, and the same for Davis FARS24H.

[hmderek]

Have you considered scenarios where the actives may be overcooling? Nice to have more than 1 active by the way. Still considering getting an RM young.

Sure want want the theoretical “real” air  temperature, but all shields are going to give you a wrong picture at some point or other. So the question should be how good or bad the shield is, not if it overheats under certain circumstances. The Barani can overheat, but as far as passive shields go none of mine have performed better than the Barani.

Having more issues recently with my TS100 than the passives by the way. All the rain and humidity is really hurting it (that is the PT100s inside) combined with strong evaporation when the June sun comes out.

[Jasper3012]

I’m honestly just going to stop replying to you @Meteorology fan, you repeat the same points over and over and over again and you just straight up ignore any input from others. Like I’ve explained a thousand times why response time isn’t the only explanation for the FARS overheating like 0.3-0.5C compared to the Barani and yet you repeat that same narrative over and over again, it’s like talking to a brick wall… You have made all your arguments very clear and I accept them, we just disagree on how significant they are. I just look at the stats and I see that the periodic error on the Barani has zero effect on the long term averages where I live, so for me, it’s not a dealbreaker by any means. For you, it is and that’s fine.

[Meteorology fan]

For me, Barani is no indicator of accuracy in all conditions. What J. Barani is pushing as the successor to the Stevenson cage is not true, that it is the most accurate in all conditions, because it is not. I have it as a comparison and most of the time it coincides with the ventilated one.

The Apogee TS100 is more susceptible to humidity than the Davis FARS24H. This we know from tests in the country.

[mauro63]

They are extremely rare, this is a very difficult field, personally I have been passionate about it for decades, but I have not yet managed, perhaps due to inability, to understand which of my instruments is giving me the real temperature of the air passing through it, so I am not one of those select few, who I said are extremely rare, who know the truth.

Unfortunately I limit myself to silly assessments on the radiative error, concentrating in the time slot from 12pm to 6pm when, on summer days, the maximum temperature has already been reached and remains more or less stable in the following hours, the solar radiation has presumably already reached its maximum level and I try to understand something about it, they are not the ideal adiabatic conditions but they are the least turbulent ones.

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Outside that range, the differences in time constants, in the timing of the detection systems, in the different behaviors with respect to the variation of heat exchanges, make it impossible for me to be part of the selects.

M.

[Meteorology fan]

Yesterday I had stormy and dynamic weather. The Barani Gen III showed 0.3 deg.C more against the Davis FARS24H. I checked the wind and at the moment of overheating at about 10m there were 5.4 km/h gusts, while the average wind speed was around 1 km/h. At the very ground, where I have covers, the wind could have been even weaker.

I checked two independent sensors. The Sensirion SHT35 overlapped with the calibrated PT1000 4-wire, and I know that an overheating of 0.3 deg.C relative to the active one occurred.

The phenomenon of overheating of the passive shields is not uncommon, including during summer, humid and stormy weather, when there will be more sun in the first half of the day.

[Jasper3012]

The Davis overheats by 0.3C pretty much every single day here, in fact today it’s 0.6C warmer with the max than the Barani! The average difference during the time interval that the 0.6C occurred was only 0.3C, so probably 0.3C of the 0.6C was an error and the other 0.3C due to a better response time.

[Meteorology fan]

How can you be sure it's definitely overheating? On windy days, Apogee and Davis FARS24H can show higher than passive shielding and this we have tested with colleagues in Poland for many months, also having high-end PT100 and PT1000 resistive sensors. Today I have a windy day and it is blowing from the northwest. Davis FARS shows a higher max of 0.4/0.5 deg.C, while Barani is cooler. Remember that the lower temperature is not always true.

It's hard for me to explain why this happens. At my place, usually Barani Gen III has lower than active, when there is a moderate/strong wind, what's more, the wind is from the side not heated by the sun, which can walk on solar days cover. This is hard to explain. When the wind is not there, the Barani stands out strongly from the Davis FARS24H on a sunny day.

[Jasper3012]

If there was no overheating vs the Barani and the only reason for the higher max on FARS would be a better response time, then you would in fact see a higher max but the average temp would be identical to the Barani, since the min would be cooler due to the quicker response time and that would cancel out the higher max. What I’m actually seeing during sunny afternoon weather is a higher min, max and avg temp than on the Barani, which is indicative of overheating. It also doesn’t make sense to me that you are claiming that the Barani is 0.4-0.5C too cool during windy weather. Shouldn’t strong wind cause the error on passive shields to decrease to near zero and the response time to match that of an actively ventilated shield? The error on the Barani is near zero with strong wind and high angle sunshine so if the FARS is running 0.5C warmer in such conditions, then I’d be quite confident in saying the 0.5C represents an error on the FARS, instead of the opposite. A potential reason for errors on shields with active ventilation during strong wind is that the wind disrupts the airflow generated by the fan and therefore harming/nullifying the typical benefit of active ventilation.

[mauro63]

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Davis Pro is 24h fars version 

M.

[Jasper3012]

That's showing the difference between MS Pro and Davis FARS 24/7? In the meantime, a very calm and clear evening here with a sharp temperature drop and the FARS responded much more quickly, as much as 0.8C colder at some point. This didn't last long but still, further confirmation that the response time on the FARS is much quicker during light wind and with the sun down. This is actually the third time I've observed this much sharper temp drop in the FARS compared to the Barani, whilst I've only observed that low angle solar radiation error on the Barani just once. This is probably because the wind speed is generally much weaker once the sun is down/at night and so that's when the active ventilation plays a bigger role. By day, it is generally quite windy here and the benefit is non-existent, the opposite even.

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[JCA433]

IF the wind disrupted the air flow through the FARS the error would likely be far larger than 0.6C.  I think a more likely explanation for the differences in measured temperatures is radiative energy flux from the sun.

[CW2274]

A potential reason for errors on shields with active ventilation during strong wind is that the wind disrupts the airflow generated by the fan and therefore harming/nullifying the typical benefit of active ventilation.

None of you guys use a case fan on the Davis, just the stock fan, right? You folks have the best comparisons going, so if not, it'd be nice to see the results if someone did.

[Jasper3012]

I just have the stock fan, yeah.

The Barani had a real struggle this morning with light wind and sunshine, frequent errors of 0.5C+, peaking at 1C. Slight wind and high angle sunshine has now reversed the situation, with the Barani 0.4C cooler. No impact on the min/max expected.

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[Meteorology fan]

The maxima are also sometimes overestimated and by 0.5/1.5 deg.C. In summer and spring seasons with calm winds at Barani Ms Pro III.