Evaluation of JULES-crop performance against site observations of irrigated maize from Mead, Nebraska

Williams, Karina; Gornall, Jemma; Harper, Anna; Wiltshire, Andy; Hemming, Debbie; Quaife, Tristan; Arkebauer, T. J.; Scoby, David

doi:10.5194/gmd-10-1291-2017

Cited by 32 publications

(71 citation statements)

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“…A revised parameterization of soil moisture stress or more sophisticated vegetation hydraulics scheme would likely improve the model in these regions. Previous work also pointed to soil moisture stress as a likely culprit for underestimated dry season GPP at two towers in the Brazilian Amazon and for GPP that was too low at a non-irrigated maize site Williams et al, 2017). Another large bias is the prevalence of shrubs in the tundra biome; therefore, more tundra-specific PFTs could improve the simulation in these regions.…”

Section: Discussionmentioning

confidence: 99%

“…When coupled to climate models, these tools enable the study of interactions between climate change, land use patterns, and the terrestrial carbon cycle. Typically, DGVMs either group the world's vegetation types into plant functional types (PFTs), or aggregate vegetation sharing a common biogeography into biomes (Woodward, 1987;Running and Gower, 1991;Prentice et al, 1992). A move towards a PFT approach recognized the differential response of plant function to rapid future climate change (Foley et al, 1996;Sitch et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

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Vegetation distribution and terrestrial carbon cycle in a carbon cycle configuration of JULES4.6 with new plant functional types

et al. 2018

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Abstract. Dynamic global vegetation models (DGVMs) are used for studying historical and future changes to vegetation and the terrestrial carbon cycle. JULES (the Joint UK Land Environment Simulator) represents the land surface in the Hadley Centre climate models and in the UK Earth System Model. Recently the number of plant functional types (PFTs) in JULES was expanded from five to nine to better represent functional diversity in global ecosystems. Here we introduce a more mechanistic representation of vegetation dynamics in TRIFFID, the dynamic vegetation component of JULES, which allows for any number of PFTs to compete based solely on their height; therefore, the previous hardwired dominance hierarchy is removed.With the new set of nine PFTs, JULES is able to more accurately reproduce global vegetation distribution compared to the former five PFT version. Improvements include the coverage of trees within tropical and boreal forests and a reduction in shrubs, the latter of which dominated at high latitudes. We show that JULES is able to realistically represent several aspects of the global carbon (C) cycle. The simulated gross primary productivity (GPP) is within the range of observations, but simulated net primary productivity (NPP) is slightly too high. GPP in JULES from 1982 to 2011 is 133 Pg C yr −1 , compared to observation-based estimates (over the same time period) between 123 ± 8 and 150-175 Pg C yr −1 . NPP from 2000 to 2013 is 72 Pg C yr −1 , compared to satellite-derived NPP of 55 Pg C yr −1 over the same period and independent estimates of 56.2 ± 14.3 Pg C yr −1 .

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Vegetation distribution and terrestrial carbon cycle in a carbon cycle configuration of JULES4.6 with new plant functional types

et al. 2018

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“…surface the soil type is also uniform across each gridbox. The parametrisation of crops in JULES (JULES-crop) is described in detail in Osborne et al (2015) and Williams et al (2017); the main aim of JULES-crop is to improve the simulation of land-atmosphere interactions where crops are a major feature of the land-surface (Osborne et al, 2015).…”

Section: Model Descriptionmentioning

confidence: 99%

“…The setting of p0 and how this affects GPP at the First ISLSCP Field Experiment (FIFE) site in Kansas is discussed in detail in Williams et al (2018). In addition Williams et al (2017) suggest modifying the p0 parameter to be 0.65 for the Mead site in Nebraska. In the simulations shown here p0 is set to 0.5 (see Table 2) modified from the default setting of 0, as recommended by Allen et al (1998).…”

Section: Avignon Site Simulationmentioning

confidence: 99%

Developing a sequential cropping capability in the JULESvn5.2 land–surface model

Mathison¹,

Challinor²,

Deva³

et al. 2019

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Abstract. Sequential cropping (also known as multiple or double cropping) is a common feature, particularly for tropical regions, where the crop seasons are largely dictated by the main wet season such as the Asian summer monsoon (ASM). The ASM provides the water resources for crops grown for the whole year, thereby influencing crop production outside the ASM period. Land surface models (LSMs) typically simulate a single crop per year, however, in order to understand how sequential cropping influences demand for resources, we need to simulate all of the crops grown within a year in a seamless way. In this paper we implement sequential cropping in a branch of the Joint UK Land Environment Simulator (JULES) and demonstrate its use at Avignon, a site that uses the sequential cropping system and provides over 15-years of continuous flux observations which we use to evaluate JULES with sequential cropping. In order to implement the method in future regional simulations where there may be large variations in growing conditions, we apply the same method to four locations in the North Indian states of Uttar Pradesh and Bihar to simulate the rice--wheat rotation and compare model yields to observations at these locations. JULES is able to simulate sequential cropping at Avignon and the four India locations, representing both crops within one growing season in each of the crop rotations presented. At Avignon the maxima of LAI, above ground biomass and canopy height occur at approximately the correct time for both crops. The magnitudes of biomass, especially for winter wheat, are underestimated and the leaf area index is overestimated. The JULES fluxes are a good fit to observations (r-values greater than 0.7), either using grasses to represent crops or the crop model, implying that both approaches represent the surface coverage correctly. For the India simulations, JULES successfully reproduces observed yields for the eastern locations, however yields are under estimated for the western locations. This development is a step forward in the ability of JULES to simulate crops in tropical regions, where this cropping system is already prevalent, while also providing the opportunity to assess the potential for other regions to implement it as an adaptation to climate change.

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Section: Introductionmentioning

confidence: 99%

Response to reviewers

Harper¹

2018

Preprint

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Dynamic global vegetation models (DGVMs) are used for studying historical and future changes to vegetation and the terrestrial carbon cycle. JULES (the Joint UK Land Environment Simulator) represents the land surface in the Hadley Centre climate models and in the UK Earth System Model. Recently the number of plant functional types (PFTs) in JULES was expanded from five to nine to better represent functional diversity in global ecosystems. Here we introduce a more mechanistic representation of vegetation dynamics in TRIFFID, the dynamic vegetation component of JULES, which allows for any number of PFTs to compete based solely on their height; therefore, the previous hardwired dominance hierarchy is removed. With the new set of nine PFTs, JULES is able to more accurately reproduce global vegetation distribution compared to the former five PFT version. Improvements include the coverage of trees within tropical and boreal forests and a reduction in shrubs, the latter of which dominated at high latitudes. We show that JULES is able to realistically represent several aspects of the global carbon (C) cycle. The simulated gross primary productivity (GPP) is within the range of observations, but simulated net primary productivity (NPP) is slightly too high. GPP in JULES from 1982 to 2011 is 133 Pg C yr −1 , compared to observation-based estimates (over the same time period) between 123 ± 8 and 150-175 Pg C yr −1. NPP from 2000 to 2013 is 72 Pg C yr −1 , compared to satellite-derived NPP of 55 Pg C yr −1 over the same period and independent estimates of 56.2 ± 14.3 Pg C yr −1. The simulated carbon stored in vegetation is 542 Pg C, compared to an observation-based range of 400-600 Pg C. Soil carbon is much lower (1422 Pg C) than estimates from measurements (> 2400 Pg C), with large underestimations of soil carbon in the tropical and boreal forests. We also examined some aspects of the historical terrestrial carbon sink as simulated by JULES. Between the 1900s and 2000s, increased atmospheric carbon dioxide levels enhanced vegetation productivity and litter inputs into the soils, while land use change removed vegetation and reduced soil carbon. The result is a simulated increase in soil carbon of 57 Pg C but a decrease in vegetation carbon of 98 Pg C. The total simulated loss of soil and vegetation carbon due to land use change is 138 Pg C from 1900 to 2009, compared to a recent observationally constrained estimate of 155 ± 50 Pg C from 1901 to 2012. The simulated land carbon sink is 2.0 ± 1.0 Pg C yr −1 from 2000 to 2009, in close agreement with estimates from the IPCC and Global Carbon Project.

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Evaluation of JULES-crop performance against site observations of irrigated maize from Mead, Nebraska

Cited by 32 publications

References 31 publications

Vegetation distribution and terrestrial carbon cycle in a carbon cycle configuration of JULES4.6 with new plant functional types

Vegetation distribution and terrestrial carbon cycle in a carbon cycle configuration of JULES4.6 with new plant functional types

Developing a sequential cropping capability in the JULESvn5.2 land–surface model

Response to reviewers

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