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For managing the content of the CSIRO Linked Data Registry http://registry.it.csiro.au/
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Unit definition for MegaJoule per Square Meter #3

Open ashleysommer opened 7 years ago

ashleysommer commented 7 years ago

Proposal:

Add a new term

http://registry.it.csiro.au/def/environment/unit/MegaJoulePerSquareMeter symbol: MJ/m2

This is an alternative unit of measurement for Solar Irradiance (http://registry.it.csiro.au/def/qudt/1.1/qudt-quantity/Irradiance) QUDT provides a unit for Watts/m2 but not MJ/m2.

Silo weather stations API provides Solar Radiation (irradiance) values in MJ/m2.

https://www.longpaddock.qld.gov.au/silo/data_format.html https://en.wikipedia.org/wiki/Solar_irradiance

dr-shorthair commented 6 years ago

Do #7 first?

ashleysommer commented 6 years ago

@dr-shorthair Definitely keen to get some forms in, as per #7 that will make it much easier to submit new terms. But getting these terms in is a higher priority right now, so hopefully we can clear these to go in, then we can get to looking at how to get the forms done.

dr-shorthair commented 6 years ago

On to the substantive proposal: MJ/m2 has dimensionality M(1)T(-2) Watts/m2 has dimensionality M(1)T(-3) So these units cannot apply to the same quantity kind. Please check/clarify.

ashleysommer commented 6 years ago

Ah yes, you're right, I didn't catch that. I will think about this some more.

ashleysommer commented 6 years ago

I found a definition for this on the BOM site:

Radiation quantities are generally expressed in terms of either irradiance or radiant exposure. Irradiance is a measure of the rate of energy received per unit area, and has units of watts per square metre (W/m2), where 1 watt (W) is equal to 1 Joule (J) per second. Radiant exposure is a time integral (or sum) of irradiance. Thus a 1 minute radiant exposure is a measure of the energy received per square metre over a period of 1 minute. Therefore a 1-minute radiant exposure = mean irradiance (W/m2) x 60(s), and has units of joule(s) per square metre (J/m2). A half-hour radiant exposure would then be the sum of 30 one-minute (or 1800 one-second) radiant exposures. For example: a mean irradiance of 500 W/m2 over 1 minute yields a radiant exposure of 30 000 J/m2 or 30 KJ/m2. The output of the Bureau of Meteorology's computer model, which estimates the daily global solar exposure from satellite data, provides irradiance integrated over a period of a day i.e. radiant or global exposure, with units of megajoule(s) per square metre. In terms of remote sensing by satellite, radiance refers to energy received by a satellite sensor and is the rate of energy received per unit area per unit of solid angle (with units of watt(s) per square metre per steradian).

http://www.bom.gov.au/climate/austmaps/solar-radiation-glossary.shtml (under Radiation Units)

Silo gives us a daily "radiation" variable, with units MJ/m2. So it looks like the term Irradiance that Im using as the ObservedProperty is incorrect, because that is an instantanetos property. Radiation is accumulated irradiance over time (in this case over a day).

Looks like I should submit a new proposal for a new environmental property called Radiation, that can have MJ/m2 for its unit.

dr-shorthair commented 6 years ago

Could you make a separate request for 'radiant exposure'. "radiation" is a phenomenon, not really a quantity-kind.

dr-shorthair commented 6 years ago

@ashleysommer where are we up to with this?

dr-shorthair commented 6 years ago

Ping @ashleysommer BTW - there is a form available for creating uom http://registry.it.csiro.au/ui/registration?register=/sandbox/environment/unit&return=/sandbox/environment/_unit#entry-form