Image processing/Evapotranspiration - Revision history

⚠️Ychemin: /* Introduction */

2023-12-18T08:01:50Z

Introduction

← Older revision		Revision as of 08:01, 18 December 2023
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	Additionally, a helper module {{AddonCmd\|i.eb.z0m}} is producing an estimation of the surface roughness, necessary in latent heat flux estimation.		Additionally, a helper module {{AddonCmd\|i.eb.z0m}} is producing an estimation of the surface roughness, necessary in latent heat flux estimation.

			For a detailed theory and modelling information behind these modules, please read the following document: [[File:Evaporation_manual_v0.6.7.pdf]]

	== i.evapo.* modules/models are integrated '''models'''==		== i.evapo.* modules/models are integrated '''models'''==

⚠️Ychemin: /* Introduction */

2023-12-02T08:26:11Z

Introduction

← Older revision		Revision as of 08:26, 2 December 2023
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	Atmospheric transfer of '''irradiance''' is subject to atmosphere particles interactions, scattering, diffraction, reflection, etc.		Atmospheric transfer of '''irradiance''' is subject to atmosphere particles interactions, scattering, diffraction, reflection, etc.

	When reaching the planetary surface, is it partially reflected in the shortwave by '''Albedo'''. Surface Albedo is the integrated 0.3-3 micro-meters reflectance, it reflects the shortwave energy coming from the sun by 5% on oceans, 15-25% on vegetation, 35-40% on sand/desert/beach, 60-80% on snow/clouds, roughly. This energy fraction is returned to atmosphere for complex interaction with gas particles again before leaving the atmosphere altogether.		When reaching the planetary surface, is it partially reflected in the shortwave by '''Albedo'''.

			Surface Albedo is the integrated 0.3-3 micro-meters reflectance, it reflects the shortwave energy coming from the sun by 5% on oceans, 15-25% on vegetation, 35-40% on sand/desert/beach, 60-80% on snow/clouds, roughly. This energy fraction is returned to atmosphere for complex interaction with gas particles again before leaving the atmosphere altogether.

	[[File:EnergyBalance.png\|\|500px\|\|Alt="Chemin, 2006, PhD Thesis"]]		[[File:EnergyBalance.png\|\|500px\|\|Alt="Chemin, 2006, PhD Thesis"]]

	As for the shortwave surface balance, the '''energy''' is also received in the longwave, but interacts with the grey-body characteristics of the surface elements. The blackbody to greybody fraction is ruled by emissivity, a hidden component in the thermal spectrum (search for Temperature- Emissivity Separation algorithms). On Earth, emissivity is always above 0.9 (mostly 0.96-0.98). The Stefan-Boltzman equation is dealing with blackbody energy, and multiplying it by Emissivity transforms it to greybody energy emitted.		As for the shortwave surface balance, the '''energy''' is also received in the longwave, but interacts with the grey-body characteristics of the surface elements.

			The blackbody to greybody fraction is ruled by emissivity, a hidden component in the thermal spectrum (search for Temperature- Emissivity Separation algorithms). On Earth, emissivity is always above 0.9 (mostly 0.96-0.98). The Stefan-Boltzman equation is dealing with blackbody energy, and multiplying it by Emissivity transforms it to greybody energy emitted.

			Together, shortwave and longwave '''energy balance''' provide with the net radiation balance at the surface of the planetary body. This crucial term is the total energy available for thermodynamic fluxes to act on the surface of the planet.

	Together, shortwave and longwave '''energy balance''' provide with the net radiation balance at the surface of the planetary body. This crucial term is the total energy available for thermodynamic fluxes to act on the surface of the planet. On a planet like Earth where there is a triple phase of a given molecule (H20, in gas, liquid, solid), energy available is used to transfer phases from lower energy to higher energy (sublimation, liquefaction, evaporation). Thermal transfers also happen as conduction (soil, rocks) and convection (atmosphere, oceans).		On a planet like Earth where there is a triple phase of a given molecule (H20, in gas, liquid, solid), energy available is used to transfer phases from lower energy to higher energy (sublimation, liquefaction, evaporation). Thermal transfers also happen as conduction (soil, rocks) and convection (atmosphere, oceans).

	The i.eb.* modules and models deal with:		The i.eb.* modules and models deal with:

⚠️Ychemin: /* See also */

2023-12-02T08:25:00Z

⚠️Ychemin: /* Introduction */

2023-12-02T08:21:40Z

Introduction

← Older revision		Revision as of 08:21, 2 December 2023
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	As for the shortwave surface balance, the '''energy''' is also received in the longwave, but interacts with the grey-body characteristics of the surface elements. The blackbody to greybody fraction is ruled by emissivity, a hidden component in the thermal spectrum (search for Temperature- Emissivity Separation algorithms). On Earth, emissivity is always above 0.9 (mostly 0.96-0.98). The Stefan-Boltzman equation is dealing with blackbody energy, and multiplying it by Emissivity transforms it to greybody energy emitted.		As for the shortwave surface balance, the '''energy''' is also received in the longwave, but interacts with the grey-body characteristics of the surface elements. The blackbody to greybody fraction is ruled by emissivity, a hidden component in the thermal spectrum (search for Temperature- Emissivity Separation algorithms). On Earth, emissivity is always above 0.9 (mostly 0.96-0.98). The Stefan-Boltzman equation is dealing with blackbody energy, and multiplying it by Emissivity transforms it to greybody energy emitted.

	Together, shortwave and longwave '''energy balance''' provide with the net radiation balance at the surface of the planetary body. This crucial term is the total energy available for thermodynamic fluxes to act on the surface of the planet. On a planet like Earth where there is a triple phase of a given molecule (H20, in gas, liquid, solid), energy available is used to transfer phases from lower energy to higher energy (sublimation, liquefaction, evaporation). Thermal transfers also happen as conduction (soil, rocks) and convection (atmosphere, oceans). The i.eb.* modules and models deal with conduction (i.eb.~~g0,~~ for thermal conduction in soils), convection (i.eb.h_* especially, for thermal convection in atmosphere) ~~and by~~ residual method ~~estimate~~ the energy left for evaporation processes ({{cmd\|i.eb.evapfr}}, {{cmd\|i.eb.eta}} are examples). {{AddonCmd\|i.eb.z0m}} is producing an estimation of the surface roughness.		Together, shortwave and longwave '''energy balance''' provide with the net radiation balance at the surface of the planetary body. This crucial term is the total energy available for thermodynamic fluxes to act on the surface of the planet. On a planet like Earth where there is a triple phase of a given molecule (H20, in gas, liquid, solid), energy available is used to transfer phases from lower energy to higher energy (sublimation, liquefaction, evaporation). Thermal transfers also happen as conduction (soil, rocks) and convection (atmosphere, oceans).

			The i.eb.* modules and models deal with:
			* conduction {{cmd\|i.eb.soilheatflux}} (for thermal conduction in soils)
			* convection i.eb.h_* especially (for thermal convection in atmosphere)
			* residual method estimating the energy left for evaporation processes ({{cmd\|i.eb.evapfr}}, {{cmd\|i.eb.eta}} are examples).

			Additionally, a helper module {{AddonCmd\|i.eb.z0m}} is producing an estimation of the surface roughness, necessary in latent heat flux estimation.

	== i.evapo.* modules/models are integrated '''models'''==		== i.evapo.* modules/models are integrated '''models'''==

⚠️Ychemin at 08:17, 2 December 2023

2023-12-02T08:17:32Z

← Older revision		Revision as of 08:17, 2 December 2023
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	~~[[File:EnergyBalance.png\|\|500px\|\|Alt="Chemin, 2006, PhD Thesis"]]~~

	== Introduction ==		== Introduction ==
	The '''radiation''' is coming from the planet's star, Earth has around 1800 W/m2 of incoming radiation from the sun (also called irradiance) at exo-atmospheric altitude.		The '''radiation''' is coming from the planet's star, Earth has around 1800 W/m2 of incoming radiation from the sun (also called irradiance) at exo-atmospheric altitude.
Line 7:		Line 5:

	When reaching the planetary surface, is it partially reflected in the shortwave by '''Albedo'''. Surface Albedo is the integrated 0.3-3 micro-meters reflectance, it reflects the shortwave energy coming from the sun by 5% on oceans, 15-25% on vegetation, 35-40% on sand/desert/beach, 60-80% on snow/clouds, roughly. This energy fraction is returned to atmosphere for complex interaction with gas particles again before leaving the atmosphere altogether.		When reaching the planetary surface, is it partially reflected in the shortwave by '''Albedo'''. Surface Albedo is the integrated 0.3-3 micro-meters reflectance, it reflects the shortwave energy coming from the sun by 5% on oceans, 15-25% on vegetation, 35-40% on sand/desert/beach, 60-80% on snow/clouds, roughly. This energy fraction is returned to atmosphere for complex interaction with gas particles again before leaving the atmosphere altogether.

			[[File:EnergyBalance.png\|\|500px\|\|Alt="Chemin, 2006, PhD Thesis"]]

	As for the shortwave surface balance, the '''energy''' is also received in the longwave, but interacts with the grey-body characteristics of the surface elements. The blackbody to greybody fraction is ruled by emissivity, a hidden component in the thermal spectrum (search for Temperature- Emissivity Separation algorithms). On Earth, emissivity is always above 0.9 (mostly 0.96-0.98). The Stefan-Boltzman equation is dealing with blackbody energy, and multiplying it by Emissivity transforms it to greybody energy emitted.		As for the shortwave surface balance, the '''energy''' is also received in the longwave, but interacts with the grey-body characteristics of the surface elements. The blackbody to greybody fraction is ruled by emissivity, a hidden component in the thermal spectrum (search for Temperature- Emissivity Separation algorithms). On Earth, emissivity is always above 0.9 (mostly 0.96-0.98). The Stefan-Boltzman equation is dealing with blackbody energy, and multiplying it by Emissivity transforms it to greybody energy emitted.

⚠️Ychemin: /* i.evapo.* modules/models are integrated models */

2023-12-02T08:16:21Z

i.evapo.* modules/models are integrated models

← Older revision		Revision as of 08:16, 2 December 2023
Line 25:		Line 25:

	Most developed thermodynamic models are:		Most developed thermodynamic models are:
	* TSEB (i.evapo.tseb: Two Source Energy Balance, Schmugge, Kustas, etc., 2000)		* TSEB (i.evapo.tseb: Two Source Energy Balance, Schmugge, Kustas, etc., 2000) Status: Incomplete Module
	* SEBS (i.evapo.sebs: Zhu et al, 2002)		* SEBS (i.evapo.sebs: Zhu et al, 2002) Status: Incomplete Module
	* SEBAL {{cmd\|i.eb.h_sebal01}}, {{cmd\|i.eb.evapfr}}, {{cmd\|i.eb.eta}} (Bastiaanssen et al, 1998, 2001)		* SEBAL {{cmd\|i.eb.h_sebal01}}, {{cmd\|i.eb.evapfr}}, {{cmd\|i.eb.eta}} (Bastiaanssen et al, 1998, 2001)

⚠️Ychemin at 08:13, 2 December 2023

2023-12-02T08:13:20Z

← Older revision		Revision as of 08:13, 2 December 2023
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	[[File:EnergyBalance.png\|\|500px\|\|Alt="Chemin, 2006, PhD Thesis"]]		[[File:EnergyBalance.png\|\|500px\|\|Alt="Chemin, 2006, PhD Thesis"]]

			== Introduction ==
	The '''radiation''' is coming from the planet's star, Earth has around 1800 W/m2 of incoming radiation from the sun (also called irradiance) at exo-atmospheric altitude.		The '''radiation''' is coming from the planet's star, Earth has around 1800 W/m2 of incoming radiation from the sun (also called irradiance) at exo-atmospheric altitude.

Line 11:		Line 12:
	Together, shortwave and longwave '''energy balance''' provide with the net radiation balance at the surface of the planetary body. This crucial term is the total energy available for thermodynamic fluxes to act on the surface of the planet. On a planet like Earth where there is a triple phase of a given molecule (H20, in gas, liquid, solid), energy available is used to transfer phases from lower energy to higher energy (sublimation, liquefaction, evaporation). Thermal transfers also happen as conduction (soil, rocks) and convection (atmosphere, oceans). The i.eb.* modules and models deal with conduction (i.eb.g0, for thermal conduction in soils), convection (i.eb.h_* especially, for thermal convection in atmosphere) and by residual method estimate the energy left for evaporation processes ({{cmd\|i.eb.evapfr}}, {{cmd\|i.eb.eta}} are examples). {{AddonCmd\|i.eb.z0m}} is producing an estimation of the surface roughness.		Together, shortwave and longwave '''energy balance''' provide with the net radiation balance at the surface of the planetary body. This crucial term is the total energy available for thermodynamic fluxes to act on the surface of the planet. On a planet like Earth where there is a triple phase of a given molecule (H20, in gas, liquid, solid), energy available is used to transfer phases from lower energy to higher energy (sublimation, liquefaction, evaporation). Thermal transfers also happen as conduction (soil, rocks) and convection (atmosphere, oceans). The i.eb.* modules and models deal with conduction (i.eb.g0, for thermal conduction in soils), convection (i.eb.h_* especially, for thermal convection in atmosphere) and by residual method estimate the energy left for evaporation processes ({{cmd\|i.eb.evapfr}}, {{cmd\|i.eb.eta}} are examples). {{AddonCmd\|i.eb.z0m}} is producing an estimation of the surface roughness.

	i.evapo.* modules/models are integrated '''models'''.		== i.evapo.* modules/models are integrated '''models'''==

	from the oldest that are not based on energy balance, but are computing some form of evapotranspiration (ETo: Evapotranspiration for a reference of 20cm well-watered grass, see FAO no56 report of Richard Allen)		from the oldest that are not based on energy balance, but are computing some form of evapotranspiration (ETo: Evapotranspiration for a reference of 20cm well-watered grass, see FAO no56 report of Richard Allen)
Line 29:		Line 30:

	and some newer models like RESET and others. The list of models using thermodynamic principles is large now, and any willing to submit a code for any of them is most welcome.		and some newer models like RESET and others. The list of models using thermodynamic principles is large now, and any willing to submit a code for any of them is most welcome.

			== Temporal Integration of Evapotranspiration ==

	When integrated in time {{cmd\|i.evapo.time}}, seasonal evapotranspiration can be computed and therefore permit a full monitoring of vegetation growth over the period. This is also a basis of crop yield estimation (see {{cmd\|i.biomass}}).		When integrated in time {{cmd\|i.evapo.time}}, seasonal evapotranspiration can be computed and therefore permit a full monitoring of vegetation growth over the period. This is also a basis of crop yield estimation (see {{cmd\|i.biomass}}).

⚠️Ychemin at 08:11, 2 December 2023

2023-12-02T08:11:41Z

@@ Line 11: / Line 11: @@
 Together, shortwave and longwave '''energy balance''' provide with the net radiation balance at the surface of the planetary body. This crucial term is the total energy available for thermodynamic fluxes to act on the surface of the planet. On a planet like Earth where there is a triple phase of a given molecule (H20, in gas, liquid, solid), energy available is used to transfer phases from lower energy to higher energy (sublimation, liquefaction, evaporation). Thermal transfers also happen as conduction (soil, rocks) and convection (atmosphere, oceans). The i.eb.* modules and models deal with conduction (i.eb.g0, for thermal conduction in soils), convection (i.eb.h_* especially, for thermal convection in atmosphere) and by residual method estimate the energy left for evaporation processes ({{cmd|i.eb.evapfr}}, {{cmd|i.eb.eta}} are examples). {{AddonCmd|i.eb.z0m}} is producing an estimation of the surface roughness.
-i.evapo.* modules/models are integrated '''models''', from the oldest (Penman-Monteith {{cmd|i.evapo.pm}}, Priestley-Taylor {{cmd|i.evapo.pt}}, Hargreaves {{cmd|i.evapo.mh}}, etc) that are not based on energy balance, but are computing some form of evapotranspiration (ETo: Evapotranspiration for a reference of 20cm well-watered grass, see FAO no56 report of Richard Allen) to newer that area in some form or another linked to thermal processes ({{cmd|i.evapo.senay}}: uses a thermal index), biome thermal processes ({{cmd|i.evapo.zk}}: global model based on typical info from biomes Albedo/soil heat flux) or more thermodynamic processes ({{cmd|i.evapo.potrad}}: potential ET if not water stress, based on astronomical equations only). Most developed thermodynamic models are TSEB (i.evapo.tseb: Two Source Energy Balance, Schmugge, Kustas, etc., 2000), SEBS (i.evapo.sebs: Zhu et al, 2002), SEBAL ({{cmd|i.eb.h_sebal01}}, {{cmd|i.eb.evapfr}}, {{cmd|i.eb.eta}}: Bastiaanssen et al, 1998, 2001), and some newer models like RESET and others. The list of models using thermodynamic principles is large now, and any willing to submit a code for any of them is most welcome.
+i.evapo.* modules/models are integrated '''models'''.
-When integrated in time {{cmd|i.evapo.time}}, seasonal evapotranspiration can be computed and therefore permit a full monitoring of vegetation growth over the period. This is also a basis of crop yield estimation (see {{cmd|i.biomass}}.
+from the oldest that are not based on energy balance, but are computing some form of evapotranspiration (ETo: Evapotranspiration for a reference of 20cm well-watered grass, see FAO no56 report of Richard Allen)
 [[File:I_evapo_time.png||800px||Alt="Temporal integration of ETa with data from a weather station"]]

⚠️Ychemin at 08:05, 2 December 2023

2023-12-02T08:05:14Z

← Older revision		Revision as of 08:05, 2 December 2023
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	i.evapo.* modules/models are integrated '''models''', from the oldest (Penman-Monteith {{cmd\|i.evapo.pm}}, Priestley-Taylor {{cmd\|i.evapo.pt}}, Hargreaves {{cmd\|i.evapo.mh}}, etc) that are not based on energy balance, but are computing some form of evapotranspiration (ETo: Evapotranspiration for a reference of 20cm well-watered grass, see FAO no56 report of Richard Allen) to newer that area in some form or another linked to thermal processes ({{cmd\|i.evapo.senay}}: uses a thermal index), biome thermal processes ({{cmd\|i.evapo.zk}}: global model based on typical info from biomes Albedo/soil heat flux) or more thermodynamic processes ({{cmd\|i.evapo.potrad}}: potential ET if not water stress, based on astronomical equations only). Most developed thermodynamic models are TSEB (i.evapo.tseb: Two Source Energy Balance, Schmugge, Kustas, etc., 2000), SEBS (i.evapo.sebs: Zhu et al, 2002), SEBAL ({{cmd\|i.eb.h_sebal01}}, {{cmd\|i.eb.evapfr}}, {{cmd\|i.eb.eta}}: Bastiaanssen et al, 1998, 2001), and some newer models like RESET and others. The list of models using thermodynamic principles is large now, and any willing to submit a code for any of them is most welcome.		i.evapo.* modules/models are integrated '''models''', from the oldest (Penman-Monteith {{cmd\|i.evapo.pm}}, Priestley-Taylor {{cmd\|i.evapo.pt}}, Hargreaves {{cmd\|i.evapo.mh}}, etc) that are not based on energy balance, but are computing some form of evapotranspiration (ETo: Evapotranspiration for a reference of 20cm well-watered grass, see FAO no56 report of Richard Allen) to newer that area in some form or another linked to thermal processes ({{cmd\|i.evapo.senay}}: uses a thermal index), biome thermal processes ({{cmd\|i.evapo.zk}}: global model based on typical info from biomes Albedo/soil heat flux) or more thermodynamic processes ({{cmd\|i.evapo.potrad}}: potential ET if not water stress, based on astronomical equations only). Most developed thermodynamic models are TSEB (i.evapo.tseb: Two Source Energy Balance, Schmugge, Kustas, etc., 2000), SEBS (i.evapo.sebs: Zhu et al, 2002), SEBAL ({{cmd\|i.eb.h_sebal01}}, {{cmd\|i.eb.evapfr}}, {{cmd\|i.eb.eta}}: Bastiaanssen et al, 1998, 2001), and some newer models like RESET and others. The list of models using thermodynamic principles is large now, and any willing to submit a code for any of them is most welcome.

	When integrated in time {{cmd\|\|i.evapo.time}}, seasonal evapotranspiration can be computed and therefore permit a full monitoring of vegetation growth over the period. This is also a basis of crop yield estimation (see {{cmd\|\|i.biomass}}.		When integrated in time {{cmd\|i.evapo.time}}, seasonal evapotranspiration can be computed and therefore permit a full monitoring of vegetation growth over the period. This is also a basis of crop yield estimation (see {{cmd\|i.biomass}}.

	[[File:I_evapo_time.png\|\|800px\|\|Alt="Temporal integration of ETa with data from a weather station"]]		[[File:I_evapo_time.png\|\|800px\|\|Alt="Temporal integration of ETa with data from a weather station"]]

⚠️Ychemin at 08:04, 2 December 2023

2023-12-02T08:04:10Z

← Older revision		Revision as of 08:04, 2 December 2023
Line 1:		Line 1:
	[[File:EnergyBalance.png\|\|~~800px~~\|\|Alt="Chemin, 2006, PhD Thesis"]]		[[File:EnergyBalance.png\|\|500px\|\|Alt="Chemin, 2006, PhD Thesis"]]

	The '''radiation''' is coming from the planet's star, Earth has around 1800 W/m2 of incoming radiation from the sun (also called irradiance) at exo-atmospheric altitude.		The '''radiation''' is coming from the planet's star, Earth has around 1800 W/m2 of incoming radiation from the sun (also called irradiance) at exo-atmospheric altitude.
Line 15:		Line 15:
	When integrated in time {{cmd\|\|i.evapo.time}}, seasonal evapotranspiration can be computed and therefore permit a full monitoring of vegetation growth over the period. This is also a basis of crop yield estimation (see {{cmd\|\|i.biomass}}.		When integrated in time {{cmd\|\|i.evapo.time}}, seasonal evapotranspiration can be computed and therefore permit a full monitoring of vegetation growth over the period. This is also a basis of crop yield estimation (see {{cmd\|\|i.biomass}}.

	[[File:I_evapo_time.png\|\|~~500px~~\|\|Alt="Temporal integration of ETa with data from a weather station"]]		[[File:I_evapo_time.png\|\|800px\|\|Alt="Temporal integration of ETa with data from a weather station"]]

	== See also ==		== See also ==

← Older revision		Revision as of 08:25, 2 December 2023
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	* Manual pages:		* Manual pages:
	** http://grass.osgeo.org/~~grass70~~/manuals/topic_energy_balance.html		** http://grass.osgeo.org/grass-stable/manuals/topic_energy_balance.html
	** http://grass.osgeo.org/~~grass70~~/manuals/topic_evapotranspiration.html		** http://grass.osgeo.org/grass-stable/manuals/topic_evapotranspiration.html
	** http://grass.osgeo.org/~~grass70~~/manuals/keywords.html#evaporative%20fraction		** http://grass.osgeo.org/grass-stable/manuals/keywords.html#evaporative%20fraction
	* [https://svn.osgeo.org/grass/grass-promo/tutorials/grass_landsat_ETa/ Evapotranspiration mapping with Landsat 5TM in GRASS GIS]		* [https://svn.osgeo.org/grass/grass-promo/tutorials/grass_landsat_ETa/ Evapotranspiration mapping with Landsat 5TM in GRASS GIS]