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Barometric Pressure?

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weather-sa
Posts: 2
Joined: Sun 27 Jan 2019 10:10 am
Weather Station: Vantage Pro
Operating System: Linux

Barometric Pressure?

Post by weather-sa » Tue 19 Feb 2019 12:37 am

I am writing a small program using wind direction and barometric pressure based on 10 years of data I have downloaded/collected from my local official government weather station. This station is at almost the same elevation with terrain very similar to mine and about 3 kms from me. Temperature, wind direction and barometer track very similar over the day compared to my personal station.

Distinct weather patterns can be plotted year by year and month by month from the collected data. Not on the same daythe year or decade previous but certainly the same reported conditions.
I need to refine the +- millibar range for the 24 hours for steady barometer, rising and falling slowly, rising and falling rapidly.
I have found many on line charts for a 3 hour period but nothing for 24 hours.

Thanks
Steve

freddie
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Re: Barometric Pressure?

Post by freddie » Tue 19 Feb 2019 9:05 am

weather-sa wrote:
Tue 19 Feb 2019 12:37 am
I am writing a small program using wind direction and barometric pressure based on 10 years of data I have downloaded/collected from my local official government weather station
What is the output from your program? What is its purpose?
weather-sa wrote:
Tue 19 Feb 2019 12:37 am
Distinct weather patterns can be plotted year by year and month by month from the collected data. Not on the same daythe year or decade previous but certainly the same reported conditions.
The patterns can most likely be linked to meanders in the jet stream. Averaged over time they are known as Rossby waves, and slowly propogate from east to west (counterintuitive, I know!) around the globe.
weather-sa wrote:
Tue 19 Feb 2019 12:37 am
I need to refine the +- millibar range for the 24 hours for steady barometer, rising and falling slowly, rising and falling rapidly.
24-hour pressure tendencies are only of real use at the equator where there is a relatively large (and predictable/consistent) diurnal component to absolute pressure values, when compared to the component of change from dynamical processes high up in the troposphere. Subtraction of the diurnal component enables the dynamical component to be recognised and its progress followed. This would be a futile exercise in a location such as the UK, as the dynamical component is much larger than the diurnal component.
weather-sa wrote:
Tue 19 Feb 2019 12:37 am
I have found many on line charts for a 3 hour period but nothing for 24 hours
This time period is used in Meteorology, as it takes a finite amount of time for a change in a gradient of pressure to result in an observable change in the wind speed and direction at a given point. It also enables tracking of disturbances high in the troposphere associated with the jet stream - which tend to manifest themselves at ground level as a change in air pressure. The scale of these features is small enough to warrant that a relatively short pressure change timespan is used.

At the end of the day, the barometric pressure is just the weight of atmosphere above a point. Whether the pressure is 1000 millibars or 1020 millibars is unlikely to have any effect on the precise weather at that point. Variables such as temperature and water vapour content (humidity) have much more sway in the actual weather experienced at a location. Also, don't forget that the troposphere is three dimensional, so the variables throughout the depth of the troposphere should be considered rather than just those at a single level. This is why supercomputers are needed to model and predict the weather.
Freddie
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