Remote Sensing for Radiation Energy Water Balance Studies

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Else Holm
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1 RS College 27 November Remote Sensing for Radiation Energy Water Balance Studies Gerbert Roerink Center for Geo-Information (CGI) Alterra, Wageningen-UR Tel:

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

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

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

5 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

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

7 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 )

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

9 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

10 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

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

12 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

$warming up of surface Temperature rises with decreasing soil moisture Evaporative fraction: Λ = λe H + λe = λe R n G 0 Λ SSEBI = T T dry dry T$

13 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

14 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

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

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

17 Examples

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

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

20 Examples Dzhankoy district: Farm lay-out Before 1991 Currently

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

22 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

23 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

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