mixed-layer model Peter Bosman, Maarten Krol Overview of internship - - PowerPoint PPT Presentation

Inverse modelling with a coupled COS-CO2 mixed-layer model

Peter Bosman, Maarten Krol Jan 27, 2020

Overview of internship + current work in progress

Vegetation uptake

2

Leaf stomata

CO2 COS CO2 CO2 COS CO2 CO2 COS CO2 COS

Largest COS sink Uptake by diffusion COS within leaves destroyed by enzymes

3

COS uptake and photosynthesis coupled to stomatal conductance -> crucial link between COS and photosynthesis A-gs approach: CO2 and COS often coupled via ratio of deposition velocities, in this study coupled via conductance

!"#$ = &'()#&*+(&, ∗ (&'(&,(*/+*0'( 0( +0/ − 0(*,/(+" &'(&,(*/+*0'()

CO2 COS

Stomatal + internal Canopy scale: integration over leaf area index Low for COS

Inverse modelling vegetation fluxes with a coupled COS-CO2 mixed-layer model

Peter Bosman, Maarten Krol Jan 27, 2020

Overview of internship + current work in progress

The model

5

Height Scalar (potential temperature, specific humidity, chemical species) Mixed layer model CLASS

The model

6

Mixed layer Soil + vegetation Free troposphere Entrainment Photosynthesis (A-gs) Respiration COS exchange Surface heat fluxes Soil COS diffusion-reaction model implemented Dynamic height

This research

7

Specific aim: Build an inverse modelling framework with a flexible cost function that allows for optimising different types of variables, including variables relating to the boundary layer dynamics simple approach!

The optimisation

8

(max) 4 parameters optimised in this study:

• alfa_plant à scaling conductance

influences COS and CO2 uptake Main link with boundary layer dynamics removed

• alfa_soil à scaling soil COS uptake/emission

influences COS uptake only

• FTC_COS à free tropospheric concentration of COS
• FTC_CO2_scale à scale for free tropospheric

concentration of CO2

9

Observations - Hyytiälä

Dataset from boreal forest in Finland – Linda Kooijmans COS and CO2 mixing ratios at 125 m eddy-covariance fluxes at 23 m +… Averaged over 7 sunny August days

10

Observations - Hyytiälä

11

Observations - Hyytiälä

Cost function prior: 2067.45 Cost function optimised: 3.95

12

Observations - Hyytiälä

Fluxes can be improved

• -> Add to cost function!

13

With net COS flux in cost function:

14

With net COS flux and gpp in cost function:

Challenges

15

Cost function Parameter x

A B

Derivative is approximated numerically (forward perturbation only) Analytical derivative requires construction of the adjoint model ≈ "# − "% Δ' Derivative at xA

Challenges

16

Derivative is approximated numerically (forward perturbation only) Analytical derivative requires construction of the adjoint model Model is non-linear

Benefits of the framework

17

Cost function can contain any variable with observations Any parameter can be optimised Future goal: No more messing with manual parameter fitting!! Challenges remain àSwitch to analytical derivative?

Free troposphere Photosynthesis (A-gs) COS uptake by vegetation Mixed layer Surface layer Soil + vegetation Entrainment: COS, CO2 exchange CO2 respiration Soil COS exchange [COS], [CO2] Dynamic height Soil COS diffusion, production and destruction Height

Current work

Novelties and challenges

19

Cost function Prior In between ecosystem and global study Incorporate several type of obs Strongly nonlinear model Parameter dependency x

20

Current work

Analytical derivative : construction of the mixed-layer adjoint

Adjoint modelling

! = 3 ∗ % + 5 ∗ ( )! = 3 ∗ )% + 5 ∗ )( )! )( )% = 5 3 1 1 )! )( )% ,)! ,)( ,)% = 5 1 3 1 ,)! ,)( ,)% Model code: Tangent linear model code: Transpose matrix: adA = 3* adC + adA adB = 5* adC + adB adC = 0 Adjoint model code:

Adjoint model code example

Adjoint modelling

24

Extra slides

COS conductance issues

25

Assume canopy consists of three leaves of same size, different stom resistance And C_air = 10 +

5 10 4 2

• +

5

• 2

2 2 10 4

≠

Potential of the framework

26

Mixed layer Entrainment flux Plant COS flux Soil COS flux Soil + vegetation Free troposphere: d [COS] !" = $%" &'() *+, ℎ%./ℎ" Free tropospheric concentration

Potential of the framework

27

Mixed layer Entrainment flux Free troposphere: d [COS] !" = $%" &'() *+, ℎ%./ℎ" Free tropospheric concentration Soil + vegetation Plant COS flux Soil COS flux

28

COS conductance issues

Assume canopy consists of three leaves of same size, different stom resistance And C_air = 10 ri: 2 2 2 rs: 3 8 2 rtot 5 10 4 Flux(= C_air/rtot) 2 1 2.5 Flux_avg 1.8333 Tot flux 3* 1.8333 rs_avg 4.3333 rtot_avg 6.3333 flux_avg 1.578947 Tot flux 3*1.578947

29

Parameters Harvard

Harvard four parameters optimised, two fluxes in cost function

alfa_plant alfa_soil FTC_COS (ppb) FTC_CO2_scale Prior

0.8 0.5 0.380 1 (364 ppm)

Optimised

0.822

• 4.674

0.361 1.063 (387 ppm)

30

Optimiser performance test

Now three parameters

alfa_plant alfa_soil FTC_COS Truth 1 1 0.37 ppb Prior 23

• 1

0.3 ppb Optimised

31

Optimiser performance test

Now three parameters

alfa_plant alfa_soil FTC_COS Truth 1 1 0.37 ppb Prior 23

• 1

0.3 ppb Optimised

• 1.10
• 94.62

0.364 ppb

33

Current coupling COS-CO2

34

Soil flux Hyytiala

Potential of the framework

35

Mixed layer Entrainment flux Free troposphere: d [COS] !" = $%" &'() *+, ℎ%./ℎ" Free tropospheric concentration

CO2!!

Soil + vegetation Plant COS flux Soil COS flux

Vegetation uptake

36

COS uptake and photosynthesis coupled to stomatal conductance -> crucial link between COS and photosynthesis Often a simple relation assumed:

!ℎ#$#%&'$ℎ(%)% = +,- .!$/0( 123 +,4 +,-

LRU = Leaf Relative Uptake COS in leaves destroyed by enzymes, with limited backward diffusion CO2 in leaves often assimilated, but backward diffusion can be significant

37