Evaluation of a Photosynthesis-Based Canopy Resistance Formulation in the Noah Land-Surface Model |
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| Authors: | Email author" target="_blank">Anil?KumarEmail author Fei?Chen Dev?Niyogi Joseph?G?Alfieri Michael?Ek Kenneth?Mitchell |
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| Institution: | (1) Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland;(2) Present address: Climate Services, Climate Analysis, MeteoSwiss, Zurich, Switzerland;(3) Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO, USA |
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| Abstract: | Accurately representing complex land-surface processes balancing complexity and realism remains one challenge that the weather
modelling community is facing nowadays. In this study, a photosynthesis-based Gas-exchange Evapotranspiration Model (GEM)
is integrated into the Noah land-surface model replacing the traditional Jarvis scheme for estimating the canopy resistance
and transpiration. Using 18-month simulations from the High Resolution Land Data Assimilation System (HRLDAS), the impact
of the photosynthesis-based approach on the simulated canopy resistance, surface heat fluxes, soil moisture, and soil temperature
over different vegetation types is evaluated using data from the Atmospheric Radiation Measurement (ARM) site, Oklahoma Mesonet,
2002 International H2O Project (IHOP_2002), and three Ameriflux sites. Incorporation of GEM into Noah improves the surface energy fluxes as well
as the associated diurnal cycle of soil moisture and soil temperature during both wet and dry periods. An analysis of midday,
average canopy resistance shows similar day-to-day trends in the model fields as seen in observed patterns. Bias and standard
deviation analyses for soil temperature and surface fluxes show that GEM responds somewhat better than the Jarvis scheme,
mainly because the Jarvis approach relies on a parametrised minimum canopy resistance and meteorological variables such as
air temperature and incident radiation. The analyses suggest that adding a photosynthesis-based transpiration scheme such
as GEM improves the ability of the land-data assimilation system to simulate evaporation and transpiration under a range of
soil and vegetation conditions. |
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