University of Wales Swansea CEH Wallingford CEH Monks Wood University of Durham MetOffice CLASSIC...

University of Wales Swansea CEH Wallingford CEH Monks Wood University of Durham MetOffice

CLASSIC –AMMA

Fieldwork 2005/2006 and modelling activities

Jon Bennie, Claire Damesin, Josiane Seghieri and Lina Mercado


Outline

• Motivation and objectives• About the JULES model• CLASSIC –CESBIO measurements What have we learned from measurements Model evaluation using physiological measurements• 2006 Fieldwork campaign


Aim:

To collect physiological and environmental data to improve the performance of land-surface models, particularly JULES (The Joint UK land atmosphere simulator) in arid environments.

Evaluate the sensitivity of plant physiological processes to temporal and spatial variations in climate.

Sensitivity analysis – what parameters are most important in constraining fluxes in the land surface scheme?

Objectives:


Campaign (2005/2006)

objectives:

Characterise diurnal cycle and spatial variability of surface temperatures (soil and plants) and soil moisture.

Characterise diurnal cycle of Photosynthesis and stomatal conductance – interspecies comparison under the same conditions.

Changes in leaf area index and plant fractional coverduring the measuring period.


What did we measure?

Diurnal cycles of:

Photosynthesis and transpiration (IRGA)

Stomatal conductance (porometer, IRGA)

Leaf water potential

(pressure chamber)

Characterisation of species leaf-level response to light and temperature (IRGA).

Leaf level measurements

on herbaceous and

woody plants


What did we measure?Soil and leaf temperatures :

Tsoil :bare soil, soil under vegetation

Tvegetation: sun/shade leaf

herbaceous woody plants

Tstems

Soil moisture

-Sampled within the flux tower footprint

- Within a 1km transect


Continuous surface and sub-surface temperatures and soil moisture

What did we measure?


What did we measure?LAI , fractional cover and vegetation classifications (CESBIO protocols)


The sun TeamZornia gloghidiata (C3)

Cenchrus biflorus (C4)

Alysicarpus ovalifolus (C3)

0

100

200

300

400

500

600

05:16 07:40 10:04 12:28 14:52 17:16 19:40

Time

gs

(mm

ol

m-2

s-1

)

0.40.50.60.70.80.91.01.1

5:16 7:40 10:04 12:28 14:52 17:16 19:40

LW

P (

MP

a)

Zornia gloghidiata (C3)

Cenchrus Biflorus (C4)

Dactiroctenium (C4)

0

100

200

300

400

500

600

05:16:48 07:40:48 10:04:48 12:28:48 14:52:48 17:16:48 19:40:48

Time

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

05:16 07:40 10:04 12:28 14:52 17:16 19:40

14.08.05 18.08.05

What have we learned ?


Comparison of Gs and LWP among C3 and C4 species

12/08/05

13/08/05

15/08/05

0

100

200

300

400

500

600

1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00

Gs [

mm

ol m

-2 s

-1]

0

0.5

1

1.5

2

2.5

3

Tragus (C4) Alysicarpus (c3) Cenchrus (C4) zornia (C3) Dactiroctenium (C4) Balanites C3 Cmbreton_joung C3 Cmbreton_old C3

LW

P [

Mp

a]

Tragus Alysicarpus Cenchrus Zornia Dact. Balanites Comb. Y Comb. A

C3 C3 C3


The ‘shade’ Team

-10

0

10

20

30

40

50

60

00:00 06:00 12:00 18:00 00:00

time

A (

μm

ol m

-2 s

-1 )

Alysicarpus

Cenchrus

Zornia

0

5

10

15

20

25

30

00:00 06:00 12:00 18:00 00:00

time

Tra

nsp

irat

ion

( m

mo

l m-2 s

-1 )

Alysicarpus

Cenchrus

Zornia

-4

-2

0

2

4

6

8

10

12

14

00:00 06:00 12:00 18:00 00:00

time

Wate

r u

se e

ffic

ien

cy

( μ

mo

l C

O 2 m

mo

l-1 H

2O

)

Alysicarpus

Cenchrus

Zornia


Transect sampling of surface temperature

herbs

bare soil

11th Aug. 05

Sampling along 1 km transects within the footprint of the flux tower


JULES

The Joint UK Land Environment Simulator (JULES), based on MOSES, the original land surface scheme of the Hadley Centre GCM.

JULES is being developed with regular “official” releases (currently JULES v.1.0) and a modular structure.

The flexible structure is intended to allow it to be modified and developed by the community to suit different requirements, spatial scales (from flux-tower to global models) and complexity.


Assessing JULES

-10

0

10

20

30

40

50

60

00:00 06:00 12:00 18:00 00:00

time

A (

μm

ol m

-2 s

-1 )

Cenchrus

C4 modelled

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

00:00 06:00 12:00 18:00 00:00

time

Sto

mat

al c

on

du

ctan

ce (

mo

l m-2 s

-1 ) Cenchrus

C4 modelled

-5

0

5

10

15

20

25

30

35

00:00 06:00 12:00 18:00 00:00

time

A (

μm

ol m

-2 s

-1 )

Zornia

C3 modelled

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

00:00 06:00 12:00 18:00 00:00

time

Sto

mat

al c

on

du

ctan

ce (

mo

l m-2 s

-1 )

C3 Modelled

Zornia


JULES runs using Agoufou met data.

August 14th 2005.

Surface conductance Gross primary productivity

Evapotranspiration


Preliminary analysis suggests:

-Current JULES parameterisation of the Farquhar model of photosynthesis for C3 plants leads to much lower gs than observed in leaf-level field measurements.

-We expect an underestimation of water fluxes from the landscape even when C3 plants are not the dominant functional type.

-e.g. If the ratio of C3/C4 cover is 0.35, mean daily error for July-August 2005 water flux would be 25%.

-Full sensitivity analysis of JULES to soil and plant physiological parameters at the site is planned.


Fieldwork campaign 2006

Continue measurements initiated in 2005

Further diurnal cycles of physiological variables stomatal conductance and photosynthesis

Complete data-set of leaf-level responses for dominant woody and herbaceous species at the site – temperature, PAR, CO2, soil moisture.

Continuous surface measurements (IRT) and (transects within tower flux print and 1km) Soil moisture Plant and soil temperature


Fieldwork campaign 2006

Possible new measurements in 2006 (to discuss)

Within the flux foot print

Leaf optical properties Measurements of reflectance and transmittance to infer leaf absorptance (possible use of Field

spectroradiometer)

Soil properties Bulk density/porosity; soil moisture release data

Heat conductivity and heat capacity Water potential/water content curve


Aknowledgements

Valerie Le Dantec, Eric Mougin,Frank Timouk,

Francois Lavenu, Francoise Guichard, Laurent Kergoat, Colin

Lloyd, Chris Taylor, Caroline Bain, Caroline Houldcroft,Frederic

Baup, Alexi Berg, Richard Dupont,Amusthapha Traore,

Amusthapha , Yacuba,Taraweti

University of Wales Swansea CEH Wallingford CEH Monks Wood University of Durham MetOffice CLASSIC...

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