Improved representation of plant functional types and physiology in the
Joint UK Land Environment Simulator (JULES v4.2) using plant trait
information

Harper, Anna; Cox, Peter M.; Friedlingstein, Pierre; Wiltshire, Andy; Jones, Chris D.; Sitch, Stephen; Mercado, Lina M.; Groenendijk, M.; Robertson, Eddy; Kattge, Jens; Bönisch, Gerhard; Atkin, Owen K.; Bahn, Michael; Cornelissen, Johannes H. C.; Niinemets, Ülo; Onipchenko, V. G.; Peñuelas, Josep; Poorter, Lourens; Reich, Peter B.; Soudzilovskaia, Nadjeda A.; Bodegom, Peter M. van

doi:10.5194/gmd-9-2415-2016

Cited by 136 publications

(156 citation statements)

References 83 publications

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“…In the version of JULES used in this study (3.4.1), each model grid box is composed of nine different surface types and five of these are PFTs. Since model version 4.2, each JULES grid box contains nine PFTS (tropical broadleaf evergreen, temperate broadleaf evergreen, broadleaf deciduous, needleleaf evergreen, needleleaf deciduous, C3, C4, evergreen shrub, deciduous shrub; Harper et al, 2016). In addition to these PFTs, a phenology model which can simulate LAI in both temperate and tropical regions would help to reduce differences between modelsimulated and observation-based estimates of GPP in the dry and wet tropics.…”

Section: Discussionmentioning

confidence: 99%

“…Model grid boxes can consist entirely of a mixture of the first eight surface types or only land ice. Since model version 4.2, each JULES grid box can contain nine PFTS (tropical broadleaf evergreen, temperate broadleaf evergreen, broadleaf deciduous, needleleaf evergreen, needleleaf deciduous, C3, C4, evergreen shrub, deciduous shrub; Harper et al, 2016).…”

Section: Model Descriptionmentioning

confidence: 99%

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Global evaluation of gross primary productivity in the JULES land surface model v3.4.1

et al. 2017

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Abstract. This study evaluates the ability of the JULES land surface model (LSM) to simulate gross primary productivity (GPP) on regional and global scales for [2001][2002][2003][2004][2005][2006][2007][2008][2009][2010]. Model simulations, performed at various spatial resolutions and driven with a variety of meteorological datasets (WFDEI-GPCC, WFDEI-CRU and PRINCETON), were compared to the MODIS GPP product, spatially gridded estimates of upscaled GPP from the FLUXNET network (FLUXNET-MTE) and the CARDAMOM terrestrial carbon cycle analysis. Firstly, when JULES was driven with the WFDEI-GPCC dataset (at 0.5 • × 0.5 • spatial resolution), the annual average global GPP simulated by JULES for 2001-2010 was higher than the observation-based estimates (MODIS and FLUXNET-MTE), by 25 and 8 %, respectively, and CAR-DAMOM estimates by 23 %. JULES was able to simulate the standard deviation of monthly GPP fluxes compared to CARDAMOM and the observation-based estimates on global scales. Secondly, GPP simulated by JULES for various biomes (forests, grasslands and shrubs) on global and regional scales were compared. Differences among JULES, MODIS, FLUXNET-MTE and CARDAMOM on global scales were due to differences in simulated GPP in the tropics. Thirdly, it was shown that spatial resolution (0.5 • × 0.5 • , 1 • × 1 • and 2 • × 2 • ) had little impact on simulated GPP on these large scales, with global GPP ranging from 140 to 142 PgC year −1 . Finally, the sensitivity of JULES to meteorological driving data, a major source of model uncertainty, was examined. Estimates of annual average global GPP were higher when JULES was driven with the PRINCETON meteorological dataset than when driven with the WFDEI-GPCC dataset by 3 PgC year −1 . On regional scales, differences between the two were observed, with the WFDEI-GPCC-driven model simulations estimating higher GPP in the tropics (5 • N-5 • S) and the PRINCETON-driven model simulations estimating higher GPP in the extratropics (30-60 • N).

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Section: Discussionmentioning

confidence: 99%

Section: Model Descriptionmentioning

confidence: 99%

Global evaluation of gross primary productivity in the JULES land surface model v3.4.1

et al. 2017

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“…It is a community model with many users and ongoing developments. For recent developments see, for example, Harper et al (2016) and Chadburn et al (2015a).…”

Section: Jules Model Descriptionmentioning

confidence: 99%

“…Here we assess the multiannual mean NPP for the period 2000 to 2012. Three notable biomes were identified based on 14 World Wildlife Fund terrestrial regions (Olson et al, 2001;Harper et al, 2016): tundra; boreal and coniferous forest; and tropical forest.…”

Section: Evaluation Data Setsmentioning

confidence: 99%

“…Nine plant functional types (PFTs) were used: tropical broadleaf evergreen trees (BET-Tr), temperate broadleaf evergreen trees (BETTe), broadleaf deciduous trees (BDT), needleleaf evergreen trees (NET), needleleaf deciduous trees (NDT), C3 and C4 grass, evergreen shrubs (ESh), and deciduous shrubs (DSh). These were parametrized following Harper et al (2016). Plant competition was allowed, with TRIFFID updating vegetation fractions on a daily time step.…”

Section: Jules Simulationsmentioning

confidence: 99%

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A vertical representation of soil carbon in the JULES land surface scheme (vn4.3_permafrost) with a focus on permafrost regions

2017

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Abstract. An improved representation of the carbon cycle in permafrost regions will enable more realistic projections of the future climate-carbon system. Currently JULES (the Joint UK Land Environment Simulator) -the land surface model of the UK Earth System Model (UKESM) -uses the standard four-pool RothC soil carbon model. This paper describes a new version of JULES (vn4.3_permafrost) in which the soil vertical dimension is added to the soil carbon model, with a set of four pools in every soil layer. The respiration rate in each soil layer depends on the temperature and moisture conditions in that layer. Cryoturbation/bioturbation processes, which transfer soil carbon between layers, are represented by diffusive mixing. The litter inputs and the soil respiration are both parametrized to decrease with increasing depth. The model now includes a tracer so that selected soil carbon can be labelled and tracked through a simulation. Simulations show an improvement in the large-scale horizontal and vertical distribution of soil carbon over the standard version of JULES (vn4.3). Like the standard version of JULES, the vertically discretized model is still unable to simulate enough soil carbon in the tundra regions. This is in part because JULES underestimates the plant productivity over the tundra, but also because not all of the processes relevant for the accumulation of permafrost carbon, such as peat development, are included in the model. In comparison with the standard model, the vertically discretized model shows a delay in the onset of soil respiration in the spring, resulting in an increased net uptake of carbon during this time. In order to provide a more suitable representation of permafrost carbon for quantifying the permafrost carbon feedback within UKESM, the deep soil carbon in the permafrost region (below 1 m) was initialized using the observed soil carbon. There is now a slight drift in the soil carbon ( < 0.018 % decade −1 ), but the change in simulated soil carbon over the 20th century, when there is little climate change, is comparable to the original vertically discretized model and significantly larger than the drift.

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Multi vegetation model evaluation of the Green Sahara climate regime

Hopcroft

Valdes

Harper

et al. 2017

Geophysical Research Letters

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During the Quaternary, the Sahara desert was periodically colonized by vegetation, likely because of orbitally induced rainfall increases. However, the estimated hydrological change is not reproduced in climate model simulations, undermining confidence in projections of future rainfall. We evaluated the relationship between the qualitative information on past vegetation coverage and climate for the mid‐Holocene using three different dynamic vegetation models. Compared with two available vegetation reconstructions, the models require 500–800 mm of rainfall over 20°–25°N, which is significantly larger than inferred from pollen but largely in agreement with more recent leaf wax biomarker reconstructions. The magnitude of the response also suggests that required rainfall regime of the early to middle Holocene is far from being correctly represented in general circulation models. However, intermodel differences related to moisture stress parameterizations, biases in simulated present‐day vegetation, and uncertainties about paleosoil distributions introduce uncertainties, and these are also relevant to Earth system model simulations of African humid periods.

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Improved representation of plant functional types and physiology in the Joint UK Land Environment Simulator (JULES v4.2) using plant trait information

Cited by 136 publications

References 83 publications

Global evaluation of gross primary productivity in the JULES land surface model v3.4.1

Global evaluation of gross primary productivity in the JULES land surface model v3.4.1

A vertical representation of soil carbon in the JULES land surface scheme (vn4.3_permafrost) with a focus on permafrost regions

Multi vegetation model evaluation of the Green Sahara climate regime

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