MOSES calibration for coniferous forest

Chris Huntingford, Peter Cox, Richard Harding…..

The datasets used

A key biome in the represented in the Hadley Centre land surface model (MOSES/TRIFFID) are needleleaf trees. Two such FLUXNET sites are:

Loobos (Holland)

Tharandt (Germany)

MOSES/TRIFFID structure

TRIFFID output

Parameters to be optimised.

Four parameters associated with photosynthesis [f0, D*, NL0, α]. These affect overall stomatal opening, VPD response, leaf nitrogen level (influencing temperature response) and light response.

Vcrit: Soil moisture content at which vegetation stress starts to occur.

Soil carbon content, Cs (in the GCM this is initial diagnosed from pre-industrial control simulation and balance between turnover and respiration).

A new light response curve (beyond “tuning” the α parameter)?

Optimisation.A full optimisation using a NAg “search” algorithm revealed multiple minima with associated risk of finding the wrong solution. No “feel” for the effect of changing parameters.

Decided instead to simply assess the effect of manually changing a) the photosynthesis parameters, then b) critical soil moisture concentration and finally c) the soil carbon content.

Once “manual” tuning has occurred, then return to NAg routines for final phase of optimisation, and including uncertainty bounds (“E04YCF”).

Once finished, see whether difference between optimised parameters (Loobos vs Tharandt) is smaller than the uncertainty bounds associated with data error.

Loobos optimisation

•Left column: original light dependence•Right column: new light dependence

•Different rows are sensitivity to soil carbon content.

Tharandt optimisation

•Left column: original light dependence•Right column: new light dependence

•Different rows are sensitivity to soil carbon content.

Light dependence.

Current model uses the Sellers (1994?) assumption that everything in the canopy scales with the top leaf level response (and according to Beer’s law).

However, this may be failing to get a smooth transition between light limited response, and other environmental constraints that occur around midday.

Light dependence.

Time of dayMidday

NEP

Measurements

Model

TemperaturelimitedLight

limited