R.sun - Revision history

Hamish: /* Linke turbidity factor values */

2025-10-29T05:12:52Z

Linke turbidity factor values

← Older revision		Revision as of 05:12, 29 October 2025
Line 112:		Line 112:
	:: '''''"The Linke turbidity factor (TL, for an air mass equal to 2) is a very convenient approximation to model the atmospheric absorption and scattering of the solar radiation under clear skies. It describes the optical thickness of the atmosphere due to both the absorption by the water vapor and the absorption and scattering by the aerosol particles relative to a dry and clean atmosphere. It summarizes the turbidity of the atmosphere, and hence the attenuation of the direct beam solar radiation. The larger TL, the larger the attenuation of the radiation by the clear sky atmosphere.'''''		:: '''''"The Linke turbidity factor (TL, for an air mass equal to 2) is a very convenient approximation to model the atmospheric absorption and scattering of the solar radiation under clear skies. It describes the optical thickness of the atmosphere due to both the absorption by the water vapor and the absorption and scattering by the aerosol particles relative to a dry and clean atmosphere. It summarizes the turbidity of the atmosphere, and hence the attenuation of the direct beam solar radiation. The larger TL, the larger the attenuation of the radiation by the clear sky atmosphere.'''''

	:: '''''The TL denotes the transparency of the cloudless atmosphere. If the sky were perfectly dry and clean, TL would be equal to 1. When the sky is deep blue, the TL is just above 1 and still very small. In summer, in Europe, the water vapour is often large and the blue sky is close to white~~. The~~ TL is larger than 3. In turbid atmosphere, e.g. in polluted cities, the TL is close to 6 - 7."'''''		:: '''''The TL denotes the transparency of the cloudless atmosphere. If the sky were perfectly dry and clean, TL would be equal to 1. When the sky is deep blue, the TL is just above 1 and still very small. In summer, in Europe, the water vapour is often large and the blue sky is close to white -- the TL is larger than 3. In turbid atmosphere, e.g. in polluted cities, the TL is close to 6 - 7."'''''

	== Automation ==		== Automation ==

Hamish: /* Linke turbidity factor values */

2025-10-29T05:11:09Z

Linke turbidity factor values

← Older revision		Revision as of 05:11, 29 October 2025
Line 110:		Line 110:
	* Download 5' global dataset for all months of 2010 as LL/WGS84 GeoTIFF here:		* Download 5' global dataset for all months of 2010 as LL/WGS84 GeoTIFF here:
	: https://www.soda-pro.com/help/general-knowledge/linke-turbidity-factor		: https://www.soda-pro.com/help/general-knowledge/linke-turbidity-factor
	:: '''''"The Linke turbidity factor (TL, for an air mass equal to 2) is a very convenient approximation to model the atmospheric absorption and scattering of the solar radiation under clear skies. It describes the optical thickness of the atmosphere due to both the absorption by the water vapor and the absorption and scattering by the aerosol particles relative to a dry and clean atmosphere. It summarizes the turbidity of the atmosphere, and hence the attenuation of the direct beam solar radiation. The larger TL, the larger the attenuation of the radiation by the clear sky atmosphere.		:: '''''"The Linke turbidity factor (TL, for an air mass equal to 2) is a very convenient approximation to model the atmospheric absorption and scattering of the solar radiation under clear skies. It describes the optical thickness of the atmosphere due to both the absorption by the water vapor and the absorption and scattering by the aerosol particles relative to a dry and clean atmosphere. It summarizes the turbidity of the atmosphere, and hence the attenuation of the direct beam solar radiation. The larger TL, the larger the attenuation of the radiation by the clear sky atmosphere.'''''

	The TL denotes the transparency of the cloudless atmosphere. If the sky were perfectly dry and clean, TL would be equal to 1. When the sky is deep blue, the TL is just above 1 and still very small. In summer, in Europe, the water vapour is often large and the blue sky is close to white. The TL is larger than 3. In turbid atmosphere, e.g. in polluted cities, the TL is close to 6 - 7."'''''		:: '''''The TL denotes the transparency of the cloudless atmosphere. If the sky were perfectly dry and clean, TL would be equal to 1. When the sky is deep blue, the TL is just above 1 and still very small. In summer, in Europe, the water vapour is often large and the blue sky is close to white. The TL is larger than 3. In turbid atmosphere, e.g. in polluted cities, the TL is close to 6 - 7."'''''

	== Automation ==		== Automation ==

Hamish: /* Linke turbidity factor values */

2025-10-29T05:10:12Z

Linke turbidity factor values

← Older revision		Revision as of 05:10, 29 October 2025
Line 110:		Line 110:
	* Download 5' global dataset for all months of 2010 as LL/WGS84 GeoTIFF here:		* Download 5' global dataset for all months of 2010 as LL/WGS84 GeoTIFF here:
	: https://www.soda-pro.com/help/general-knowledge/linke-turbidity-factor		: https://www.soda-pro.com/help/general-knowledge/linke-turbidity-factor
			:: '''''"The Linke turbidity factor (TL, for an air mass equal to 2) is a very convenient approximation to model the atmospheric absorption and scattering of the solar radiation under clear skies. It describes the optical thickness of the atmosphere due to both the absorption by the water vapor and the absorption and scattering by the aerosol particles relative to a dry and clean atmosphere. It summarizes the turbidity of the atmosphere, and hence the attenuation of the direct beam solar radiation. The larger TL, the larger the attenuation of the radiation by the clear sky atmosphere.

			The TL denotes the transparency of the cloudless atmosphere. If the sky were perfectly dry and clean, TL would be equal to 1. When the sky is deep blue, the TL is just above 1 and still very small. In summer, in Europe, the water vapour is often large and the blue sky is close to white. The TL is larger than 3. In turbid atmosphere, e.g. in polluted cities, the TL is close to 6 - 7."'''''

	== Automation ==		== Automation ==

Hamish: /* Automation */

2025-10-29T03:53:26Z

Automation

← Older revision		Revision as of 03:53, 29 October 2025
Line 99:		Line 99:

	The above assumes that your projection's ellipsoid is WGS84. If it isn't, use other proj_out= terms with m.proj as required instead of the -o flag.		The above assumes that your projection's ellipsoid is WGS84. If it isn't, use other proj_out= terms with m.proj as required instead of the -o flag.

			== Linke turbidity factor values ==

			* See Remund et al. (2003) appendix/table 1 for a list of monthly values for many sites around the world:
			: https://www.researchgate.net/publication/42358500_Worldwide_Linke_turbidity_information

			* A good description and recipe for calculating it here: (section 3.3.4, page 22)
			: https://atmosphere.copernicus.eu/sites/default/files/2022-01/CAMS2_73_2021SC1_D3.2.1_2021_UserGuide_v1.pdf

			* Download 5' global dataset for all months of 2010 as LL/WGS84 GeoTIFF here:
			: https://www.soda-pro.com/help/general-knowledge/linke-turbidity-factor


	== Automation ==		== Automation ==

Hamish: /* Minimum number of days needed to summarize a solar year */

2025-09-29T05:08:48Z

Minimum number of days needed to summarize a solar year

← Older revision		Revision as of 05:08, 29 September 2025
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	== Minimum number of days needed to summarize a solar year ==		== Minimum number of days needed to summarize a solar year ==

	You can get ~~a rough~~ curve of daily irradiation throughout the year by running r.sun for e.g. just the middle day of each month, or just for the solstices, equinoxes, and half way between them.		You can get an estimated curve of daily irradiation throughout the year by running r.sun for e.g. just the middle day of each month, or just for the solstices, equinoxes, and half way between them.

	For example:		For example:

Hamish: /* Tips */

2025-09-29T05:06:37Z

Tips

← Older revision		Revision as of 05:06, 29 September 2025
Line 12:		Line 12:
	The <tt>latin</tt> and <tt>longin</tt> maps are generally only needed if you are running r.sun from a simple XY location. In normal use with a known map projection they are not needed.		The <tt>latin</tt> and <tt>longin</tt> maps are generally only needed if you are running r.sun from a simple XY location. In normal use with a known map projection they are not needed.

	If you are in a coastal area you can speed up processing by setting regions of water to NULL in the DEM input raster map. See the {{cmd\|r.null}} module. ~~This~~ may reduce the amount of reflected light in the global and <tt>refl_rad</tt> output maps. I suspect that r.sun does not model glint off water at low sun angles, although you may have luck setting water masses to a high albedo with the <tt>albedo</tt> input raster if that is important to you.		If you are in a coastal area you can speed up processing by setting regions of water to NULL in the DEM input raster map. See the {{cmd\|r.null}} module. Note that this may reduce the amount of reflected light in the global and <tt>refl_rad</tt> output maps. I suspect that r.sun does not model glint off water at low sun angles, although you may have luck setting water masses to a high albedo with the <tt>albedo</tt> input raster if that is important to you.


	== Testing ==		== Testing ==

Hamish: /* Minimum number of days needed to summarize a solar year */

2025-09-29T05:02:20Z

Minimum number of days needed to summarize a solar year

← Older revision		Revision as of 05:02, 29 September 2025
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	! Day !! DOY !! Comment		! Day !! DOY !! Comment
	\|-		\|-
	\| Feb 5th \|\| 036 \|\| mid		\| Feb 5th \|\| 036 \|\| ''mid''
	\|-		\|-
	\| Mar 21st \|\| 080 \|\| equinox		\| Mar 21st \|\| 080 \|\| equinox
	\|-		\|-
	\| May 6th \|\| 126 \|\| mid		\| May 6th \|\| 126 \|\| ''mid''
	\|-		\|-
	\| Jun 21st \|\| 172 \|\| solstice		\| Jun 21st \|\| 172 \|\| solstice
	\|-		\|-
	\| Aug 6th \|\| 218 \|\| mid		\| Aug 6th \|\| 218 \|\| ''mid''
	\|-		\|-
	\| Sept 21st \|\| 264 \|\| equinox		\| Sept 21st \|\| 264 \|\| equinox
	\|-		\|-
	\| Nov 6th \|\| 310 \|\| mid		\| Nov 6th \|\| 310 \|\| ''mid''
	\|-		\|-
	\| Dec 21st \|\| 355 \|\| solstice		\| Dec 21st \|\| 355 \|\| solstice

Hamish: /* Optional input maps */

2025-09-29T05:01:58Z

Optional input maps

← Older revision		Revision as of 05:01, 29 September 2025
Line 63:		Line 63:
	* horizon= and horizonstep= options: Pre-calculate horizon shadows by creating a series of horizon rasters with the {{cmd\|r.horizon}} module.		* horizon= and horizonstep= options: Pre-calculate horizon shadows by creating a series of horizon rasters with the {{cmd\|r.horizon}} module.
	: Results may not be as smooth as without using this option?? See {{trac\|498}}.		: Results may not be as smooth as without using this option?? See {{trac\|498}}.
	: Estimated speedup: ?%. Depends on the number of horizon maps. Note for accuracy you might want a large number of pre-calculated horizon maps, but that comes with the downside of it taking a long time and lots of memory to load them off the disk. Calculating horizons in real-time in the CPU may in fact be both more accurate 'and' faster. More tests are needed to clarify this issue.		: Estimated speedup: ?%. Depends on the number of horizon maps. Note for accuracy you might want a large number of pre-calculated horizon maps, but that comes with the downside of it taking a long time and lots of memory to load them off the disk. Calculating horizons in real-time in the CPU may in fact be both more accurate ''and'' faster. More tests are needed to clarify this issue.

Hamish: /* Minimum number of days needed to summarize a solar year */

2025-09-29T04:58:34Z

Minimum number of days needed to summarize a solar year

← Older revision		Revision as of 04:58, 29 September 2025
Line 162:		Line 162:
	== Minimum number of days needed to summarize a solar year ==		== Minimum number of days needed to summarize a solar year ==

	You can get a rough curve of daily irradiation throughout the year by running r.sun for e.g. just the middle day of each month, or just for the solstices, equinoxes, and half way between them. For example:		You can get a rough curve of daily irradiation throughout the year by running r.sun for e.g. just the middle day of each month, or just for the solstices, equinoxes, and half way between them.

			For example:

	:{\| class="wikitable"		:{\| class="wikitable"
Line 187:		Line 189:

	You may want to duplicate the results from Dec. 21st as day -10 when you fit the curve in your plot.		You may want to duplicate the results from Dec. 21st as day -10 when you fit the curve in your plot.


	== Overview of monthly maps ==		== Overview of monthly maps ==

Hamish: /* Overview of monthly maps */

2025-09-29T04:57:58Z

Overview of monthly maps

← Older revision		Revision as of 04:57, 29 September 2025
Line 159:		Line 159:

	* For a r.sun Mode 1 loop, see the [[Parallelizing Scripts]] page.		* For a r.sun Mode 1 loop, see the [[Parallelizing Scripts]] page.

			== Minimum number of days needed to summarize a solar year ==

			You can get a rough curve of daily irradiation throughout the year by running r.sun for e.g. just the middle day of each month, or just for the solstices, equinoxes, and half way between them. For example:

			:{\| class="wikitable"
			\|+ Day of year for minimal annual summary
			\|-
			! Day !! DOY !! Comment
			\|-
			\| Feb 5th \|\| 036 \|\| mid
			\|-
			\| Mar 21st \|\| 080 \|\| equinox
			\|-
			\| May 6th \|\| 126 \|\| mid
			\|-
			\| Jun 21st \|\| 172 \|\| solstice
			\|-
			\| Aug 6th \|\| 218 \|\| mid
			\|-
			\| Sept 21st \|\| 264 \|\| equinox
			\|-
			\| Nov 6th \|\| 310 \|\| mid
			\|-
			\| Dec 21st \|\| 355 \|\| solstice
			\|}

			You may want to duplicate the results from Dec. 21st as day -10 when you fit the curve in your plot.


	== Overview of monthly maps ==		== Overview of monthly maps ==