Remote Sensing for Radiation Energy Water Balance Studies

RS College 27 November Remote Sensing for Radiation Energy Water Balance Studies Gerbert Roerink Center for Geo-Information (CGI) Alterra, Wageningen-UR Email: Gerbert.Roerink@wur.nl Tel: 0317-474300

Contents Theory of radiation-energy-water balance SSEBI algorithm Examples Introduction to practicum

Contents Theory of radiation-energy-water balance SSEBI algorithm Examples Introduction to practicum

Theory of radiation energy water balance Radiation Balance R n = S S + L L

Theory of radiation energy water balance Radiation Balance R R S S L L n n = S S + L L (W/m 2 ) = net radiation = incoming shortwave solar radiation = outgoing (reflected) shortwave radiation = incoming longwave radiation from atmosphere = outgoing longwave radiation from earth

Theory of radiation energy water balance Energy Balance H λe H R n λe G 0 R n G 0 = G 0 + H + λe

Theory of radiation energy water balance Energy Balance R R G n n 0 = G 0 + H + λe (W/m = net radiation = soil heat flux (warming up of soil) H = sensible heat flux (warming up of surface) λe = latent heat flux (evaporation process) 2 )

Theory of radiation energy water balance Water Balance Θ = P + I R q ETA

Theory of radiation energy water balance Water Balance Θ = P + I R q ETA (mm/d) Θ = soil moisture P = precipitation I = irrigation R = run - off q = percolation ETA = actual evapotranspiration

Theory of radiation energy water balance R a d ia tio n b a la n c e S u rfa c e e n e rg y b a la n c e W a te r b a la n c e (W /m 2 ) (W /m 2 ) (m m /d a y ) S h o rtw a v e R a d ia tio n L o n g w a v e R a d ia tio n K K L L R n N e t R a d ia tio n G 0 S o il H e a t F lu x H S e n s ib le H e a t F lu x R R u n o ff q P e rc o la tio n I Irrig a tio n P P re c ip ita tio n θ S o il M o is tu re S u rfa c e T e m p e ra tu re T 0 E v a p o ra tiv e F ra c tio n R e fle c tio n r 0 S E B I Λ λ E E T A R o u g h n e s s z 0 L a te n t H e a t F lu x A c tu a l E v a p o tra n s p ira tio n

Contents Theory of radiation-energy-water balance SSEBI algorithm Examples Introduction to practicum

SSEBI algorithm SSEBI = Simplified Surface Energy Balance Index SSEBI calculates the evaporative fraction from surface reflectance, temperature (and roughness) Evaporative fraction (Λ) is the part of the available energy at the surface that is used for the evaporation process Assumptions!! - Atmospheric conditions constant over the image - Dry and wet spots available within the image

SSEBI algorithm SSEBI uses the following principle Wet soil: all energy is used for evaporation process Dry soil: all energy is used for warming up of surface Temperature rises with decreasing soil moisture Evaporative fraction: Λ = λe H + λe = λe R n G 0 Λ SSEBI = T T dry dry T T 0 wet

SSEBI algorithm R a d ia tio n b a la n c e S u rfa c e e n e rg y b a la n c e W a te r b a la n c e (W /m 2 ) (W /m 2 ) (m m /d a y ) S h o rtw a v e R a d ia tio n L o n g w a v e R a d ia tio n K K L L R n N e t R a d ia tio n G 0 S o il H e a t F lu x H S e n s ib le H e a t F lu x R R u n o ff q P e rc o la tio n I Irrig a tio n P P re c ip ita tio n θ S o il M o is tu re S u rfa c e T e m p e ra tu re T 0 E v a p o ra tiv e F ra c tio n R e fle c tio n r 0 S E B I Λ λ E E T A R o u g h n e s s z 0 L a te n t H e a t F lu x A c tu a l E v a p o tra n s p ira tio n

Contents Theory of radiation-energy-water balance SSEBI algorithm Examples Introduction to practicum

Examples Evapotranspiration, The Netherlands, Landsat-TM, 10-Mar-97

Examples

Examples Remote sensing: Clouds August 1992 Kakhovska Dnieper August 2001 Kakhovska Clouds Black Sea NCC NCC

Examples Evaporative fraction, Crimea, Ukraine, Landsat-TM, 7-Jul-2001

Examples Dzhankoy district: Farm lay-out Before 1991 Currently

Contents Theory of radiation-energy-water balance SSEBI algorithm Examples Introduction to practicum

Introduction to practicum R a d ia tio n b a la n c e S u rfa c e e n e rg y b a la n c e W a te r b a la n c e (W /m 2 ) (W /m 2 ) (m m /d a y ) S h o rtw a v e R a d ia tio n L o n g w a v e R a d ia tio n K K L L R n N e t R a d ia tio n G 0 S o il H e a t F lu x H S e n s ib le H e a t F lu x R R u n o ff q P e rc o la tio n I Irrig a tio n P P re c ip ita tio n θ S o il M o is tu re S u rfa c e T e m p e ra tu re T 0 E v a p o ra tiv e F ra c tio n R e fle c tio n r 0 S E B I Λ λ E E T A R o u g h n e s s z 0 L a te n t H e a t F lu x A c tu a l E v a p o tra n s p ira tio n

Introduction to practicum Case study: Italy, Landsat-TM, 23-Aug-97 Input materials: Images of surface albedo, temperature, emissivity Paper SSEBI: a simple remote sensing algorithm to estimate the surface energy balance Field data and constants Use Model Maker in ERDAS-Imagine to Step 1: Calculate net radiation Step 2: Calculate evapoative fraction Step 3: Calculate surface energy fluxes