Improvements to the Community Land Model and their impact on the hydrological cycle

Oleson, Keith W.; Niu, Guo Yue; Yang, Zong‐Liang; Lawrence, David M.; Thornton, P. E.; Lawrence, P.; Stöckli, Reto; Dickinson, Robert E.; Bonan, Gordon B.; Levis, Samuel; Dai, Aiguo; Qian, Tianchen

doi:10.1029/2007jg000563

Cited by 752 publications

(790 citation statements)

References 54 publications

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“…The land model is defined on the same horizontal grid as the atmosphere and includes components for biogeophysics, biogeochemistry, the hydrologic cycle as well as a dynamic global vegetation model 71,72 . In order to improve the simulation of the land surface hydrology and vegetation cover, new parameterizations for canopy interception and soil evaporation have been implemented into the land component 73 [78][79][80] . In addition, the 38 ka BP ICE-5G continental ice-sheet distribution has been implemented 76 .…”

Section: Numerical Experimentsmentioning

confidence: 99%

North Atlantic forcing of tropical Indian Ocean climate

Mohtadi

Prange

Oppo

et al. 2014

Nature

252

228

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The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells 1-5 , but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic circulation slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during North Atlantic cold spells.In the North Atlantic, the most recent glacial and deglacial periods are characterized by a series of abrupt and severe cold snaps of millennial duration associated with either iceberg instabilities and surges (Heinrich events) or freshwater input from the Arctic Ocean 6 (the Younger Dryas). These abrupt events are of particular interest because they were rapidly communicated through the ocean by a slowdown, or potentially a shutdown, of the Atlantic meridional overturning circulation 7 (AMOC) and through the atmospheric circulation 8 causing climate anomalies worldwide. Climate archives document a significant tropical hydrologic response to these events. Dry Younger Dryas and Heinrich stadials have been reported from various marine and terrestrial archives across the tropical Indian Ocean 4,9-14 .However, a few records suggest wet Younger Dryas or Heinrich stadials over northeast Australia 15 , southern Indonesia 5,16 and southeast Africa 12,17 . Although there seems to be strong evidence that the intertropical convergence zone (ITCZ) moved southwards in the tropical Atlantic 2 , a wide range of mechanisms have been offered to explain the connection between the cooling of the North Atlantic and tropical Indian Ocean hydroclimates: a weakening of the rainfall system in response to regional sea surface cooling 13,14 ; and changes in the monsoon intensity 4,10,16 associated with a southward shift in the mean 1 or winter 4,5,15 position of the ITCZ or in the position of oceanic fronts 18 .How...

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Section: Numerical Experimentsmentioning

confidence: 99%

North Atlantic forcing of tropical Indian Ocean climate

Mohtadi

Prange

Oppo

et al. 2014

Nature

252

228

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“…The main difference can be found in the water cycle module, which simulates the dynamics of inundated surface water extent and water table position Liu et al, 2012. The new water cycle module uses components of previously published models, TOPMODEL (Topography based hydrological model; Beven and Kirkby, 1979), SIMTOP (Simple TOPMODEL; Niu et al, 2005) and CLM (Oleson et al, 2008), to improve its soil and surface water dynamics (Liu et al, 2012).…”

Section: Wetchimp Set-upmentioning

confidence: 99%

Present state of global wetland extent and wetland methane modelling: methodology of a model inter-comparison project (WETCHIMP)

Wania

Melton²,

Hodson³

et al. 2013

Geosci. Model Dev.

189

180

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Abstract. The Wetland and Wetland CH 4 Intercomparison of Models Project (WETCHIMP) was created to evaluate our present ability to simulate large-scale wetland characteristics and corresponding methane (CH 4 ) emissions. A multi-model comparison is essential to evaluate the key uncertainties in the mechanisms and parameters leading to methane emissions. Ten modelling groups joined WETCHIMP to run eight global and two regional models with a common experimental protocol using the same climate and atmospheric carbon dioxide (CO 2 ) forcing datasets. We reported the main conclusions from the intercomparison effort in a companion paper (Melton et al., 2013). Here we provide technical details for the six experiments, which included an equilibrium, a transient, and an optimized run plus three sensitivity experiments (temperature, precipitation, and atmospheric CO 2 concentration). The diversity of approaches used by the models is summarized through a series of conceptual figures, and is used to evaluate the wide range of wetland extent and CH 4 fluxes predicted by the models in the equilibrium run. We discuss relationships among the various approaches and patterns in consistencies of these model predictions. Within this group of models, there are three broad classes of methods used to estimate wetland extent: prescribed based on wetland distribution maps, prognostic relationships between hydrological states based on satellite observations, and explicit hydrological mass balances. A larger variety of approaches was used to estimate the net CH 4 fluxes from wetland systems. Even though modelling of wetland extent and CH 4 emissions has progressed significantly over recent decades, large uncertainties still exist when estimating CH 4 emissions: there is little consensus on model structure or complexity due to knowledge gaps, different aims of the models, and the range of temporal and spatial resolutions of the models.

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“…A detailed description of the physical processes, modification and performance of CLM3.5 was given in Oleson et al (2004Oleson et al ( , 2008 and .…”

Section: Land Surface Model Clm35mentioning

confidence: 99%

Improving simulation of soil moisture in China using a multiple meteorological forcing ensemble approach

Liu

Xie

2013

Hydrol. Earth Syst. Sci.

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Abstract. The quality of soil-moisture simulation using land surface models depends largely on the accuracy of the meteorological forcing data. We investigated how to reduce the uncertainty arising from meteorological forcings in a simulation by adopting a multiple meteorological forcing ensemble approach. Simulations by the Community Land Model version 3.5 (CLM3.5) over mainland China were conducted using four different meteorological forcings, and the four sets of soil-moisture data related to the simulations were then merged using simple arithmetical averaging and Bayesian model averaging (BMA) ensemble approaches. BMA is a statistical post-processing procedure for producing calibrated and sharp predictive probability density functions (PDFs), which is a weighted average of PDFs centered on the biascorrected forecasts from a set of individual ensemble members based on their probabilistic likelihood measures. Compared to in situ observations, the four simulations captured the spatial and seasonal variations of soil moisture in most cases with some mean bias. They performed differently when simulating the seasonal phases in the annual cycle, the interannual variation and the magnitude of observed soil moisture over different subregions of mainland China, but no individual meteorological forcing performed best for all subregions. The simple arithmetical average ensemble product outperformed most, but not all, individual members over most of the subregions. The BMA ensemble product performed better than simple arithmetical averaging, and performed best for all fields over most of the subregions. The BMA ensemble approach applied to the ensemble simulation reproduced anomalies and seasonal variations in observed soil-moisture values, and simulated the mean soil moisture. It is presented here as a promising way for reproducing long-term, highresolution spatial and temporal soil-moisture data.

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Improvements to the Community Land Model and their impact on the hydrological cycle

Cited by 752 publications

References 54 publications

North Atlantic forcing of tropical Indian Ocean climate

North Atlantic forcing of tropical Indian Ocean climate

Present state of global wetland extent and wetland methane modelling: methodology of a model inter-comparison project (WETCHIMP)

Improving simulation of soil moisture in China using a multiple meteorological forcing ensemble approach

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