Constraining ecosystem model with adaptive Metropolis algorithm using boreal forest site eddy covariance measurements

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Makela , J , Susiluoto , J , Markkanen , T , Aurela , M , Järvinen , H , Mammarella , I , Hagemann , S & Aalto , T 2016 , ' Constraining ecosystem model with adaptive Metropolis algorithm using boreal forest site eddy covariance measurements ' , Nonlinear processes in geophysics , vol. 23 , no. 6 , pp. 447-465 . https://doi.org/10.5194/npg-23-447-2016

Title: Constraining ecosystem model with adaptive Metropolis algorithm using boreal forest site eddy covariance measurements
Author: Makela, Jarmo; Susiluoto, Jouni; Markkanen, Tiina; Aurela, Mika; Järvinen, Heikki; Mammarella, Ivan; Hagemann, Stefan; Aalto, Tuula
Contributor: University of Helsinki, Department of Physics
University of Helsinki, Department of Physics
Date: 2016-12-09
Language: eng
Number of pages: 19
Belongs to series: Nonlinear processes in geophysics
ISSN: 1023-5809
URI: http://hdl.handle.net/10138/172955
Abstract: We examined parameter optimisation in the JSBACH (Kaminski et al., 2013; Knorr and Kattge, 2005; Reick et al., 2013) ecosystem model, applied to two boreal forest sites (Hyytiala and Sodankyla) in Finland. We identified and tested key parameters in soil hydrology and forest water and carbon-exchange-related formulations, and optimised them using the adaptive Metropolis (AM) algorithm for Hyytil with a 5-year calibration period (2000-2004) followed by a 4-year validation period (2005-2008). Sodankyla acted as an independent validation site, where optimisations were not made. The tuning provided estimates for full distribution of possible parameters, along with information about correlation, sensitivity and identifiability. Some parameters were correlated with each other due to a phenomenological connection between carbon uptake and water stress or other connections due to the set-up of the model formulations. The latter holds especially for vegetation phenology parameters. The least identifiable parameters include phenology parameters, parameters connecting relative humidity and soil dryness, and the field capacity of the skin reservoir. These soil parameters were masked by the large contribution from vegetation transpiration. In addition to leaf area index and the maximum carboxylation rate, the most effective parameters adjusting the gross primary production (GPP) and evapotranspiration (ET) fluxes in seasonal tuning were related to soil wilting point, drainage and moisture stress imposed on vegetation. For daily and half-hourly tunings the most important parameters were the ratio of leaf internal CO2 concentration to external CO2 and the parameter connecting relative humidity and soil dryness. Effectively the seasonal tuning transferred water from soil moisture into ET, and daily and half-hourly tunings reversed this process. The seasonal tuning improved the month-to-month development of GPP and ET, and produced the most stable estimates of water use efficiency. When compared to the seasonal tuning, the daily tuning is worse on the seasonal scale. However, daily parametrisation reproduced the observations for average diurnal cycle best, except for the GPP for Sodankyla validation period, where half-hourly tuned parameters were better. In general, the daily tuning provided the largest reduction in model-data mismatch. The models response to drought was unaffected by our parametrisations and further studies are needed into enhancing the dry response in JSBACH.
Subject: GROSS PRIMARY PRODUCTION
SCOTS PINE FOREST
CARBON-DIOXIDE EXCHANGE
LAND-SURFACE MODELS
EARTH SYSTEM MODEL
FLUX OBSERVATIONS
SOUTHERN FINLAND
CO2 EXCHANGE
MONTE-CARLO
SOIL-WATER
114 Physical sciences
1172 Environmental sciences
116 Chemical sciences
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