scholarly journals Representation of Water Table Dynamics in a Land Surface Scheme. Part I: Model Development

2005 ◽  
Vol 18 (12) ◽  
pp. 1861-1880 ◽  
Author(s):  
Pat J-F. Yeh ◽  
Elfatih A. B. Eltahir
Keyword(s):  
Water Table ◽  
Land Surface ◽  
Surface States ◽  
Unconfined Aquifer ◽  
Water Table Depth ◽  
Shallow Water Table ◽  
Transfer Scheme ◽  
Land Surface Scheme ◽  
Soil Model ◽  
Surface Scheme

Abstract Most of the current land surface parameterization schemes lack any representation of regional groundwater aquifers. Such a simplified representation of subsurface hydrological processes would result in significant errors in the predicted land surface states and fluxes especially for the shallow water table areas in humid regions. This study attempts to address this deficiency. To incorporate the water table dynamics into a land surface scheme, a lumped unconfined aquifer model is developed to represent the regional unconfined aquifer as a nonlinear reservoir, in which the aquifer simultaneously receives the recharge from the overlying soils and discharges runoff into streams. The aquifer model is linked to the soil model in the land surface scheme [Land Surface Transfer Scheme (LSX)] through the soil drainage flux. The total thickness of the unsaturated zone varies in response to the water table fluctuations, thereby interactively coupling the aquifer model with the soil model. The coupled model (called LSXGW) has been tested in Illinois for an 11-yr period from 1984 to 1994. The results show reasonable agreements with the observations. However, there are still secondary biases in the LSXGW simulation partially resulting from not accounting for the spatial variability of water table depth. The issue of subgrid variability of water table depth will be addressed in a companion paper.

scholarly journals Development of a Coupled Land Surface Hydrologic Model and Evaluation at a Critical Zone Observatory

2013 ◽  
Vol 14 (5) ◽  
pp. 1401-1420 ◽  
Author(s):  
Yuning Shi ◽  
Kenneth J. Davis ◽  
Christopher J. Duffy ◽  
Xuan Yu
Keyword(s):  
Latent Heat ◽  
Water Table ◽  
Land Surface ◽  
Hydrologic Model ◽  
Heat Fluxes ◽  
Water Table Depth ◽  
Surface Model ◽  
Land Surface Scheme ◽  
Model Predictions ◽  
Surface Scheme

Abstract A fully coupled land surface hydrologic model, Flux-PIHM, is developed by incorporating a land surface scheme into the Penn State Integrated Hydrologic Model (PIHM). The land surface scheme is adapted from the Noah land surface model. Because PIHM is capable of simulating lateral water flow and deep groundwater at spatial resolutions sufficient to resolve upland stream networks, Flux-PIHM is able to represent heterogeneities due to topography and soils at high resolution, including spatial structure in the link between groundwater and the surface energy balance (SEB). Flux-PIHM has been implemented at the Shale Hills watershed (0.08 km2) in central Pennsylvania. Multistate observations of discharge, water table depth, soil moisture, soil temperature, and sensible and latent heat fluxes in June and July 2009 are used to manually calibrate Flux-PIHM at hourly temporal resolution. Model predictions from 1 March to 1 December 2009 are evaluated. Both hydrologic predictions and SEB predictions show good agreement with observations. Comparisons of model predictions between Flux-PIHM and the original PIHM show that the inclusion of the complex SEB simulation only brings slight improvement in hourly model discharge predictions. Flux-PIHM adds the ability of simulating SEB to PIHM and does improve the prediction of hourly evapotranspiration, the prediction of total runoff (discharge), and the predictions of some peak discharge events, especially after extended dry periods. Model results reveal that annual average sensible and latent heat fluxes are strongly correlated with water table depth, and the correlation is especially strong for the model grids near the stream.

scholarly journals Representation of Water Table Dynamics in a Land Surface Scheme. Part II: Subgrid Variability

2005 ◽  
Vol 18 (12) ◽  
pp. 1881-1901 ◽  
Author(s):  
Pat J-F. Yeh ◽  
Elfatih A. B. Eltahir
Keyword(s):  
Groundwater Recharge ◽  
Water Table ◽  
Land Surface ◽  
Large Scale ◽  
Climate Models ◽  
Land Surface Scheme ◽  
Groundwater Runoff ◽  
Aquifer Storage ◽  
Mosaic Approach ◽  
Surface Scheme

Abstract A lumped unconfined aquifer model has been developed and interactively coupled to a land surface scheme in a companion paper. Here, the issue of the representation of subgrid variability of water table depths (WTDs) is addressed. A statistical–dynamical (SD) approach is used to account for the effects of the unresolved subgrid variability of WTD in the grid-scale groundwater runoff. The dynamic probability distribution function (PDF) of WTD is specified as a two-parameter gamma distribution based on observations. The grid-scale groundwater rating curve (i.e., aquifer storage–discharge relationship) is derived statistically by integrating a point groundwater runoff model with respect to the PDF of WTD. Next, a mosaic approach is utilized to account for the effects of subgrid variability of WTD in the grid-scale groundwater recharge. A grid cell is categorized into different subgrids based on the PDF of WTD. The grid-scale hydrologic fluxes are computed by averaging all of the subgrid fluxes weighted by their fractions. This new methodology combines the strengths of the SD approach and the mosaic approach. The results of model testing in Illinois from 1984 to 1994 indicate that the simulated hydrologic variables (soil saturation and WTD) and fluxes (evaporation, runoff, and groundwater recharge) agree well with the observations. Because of the paucity of the large-scale observations on WTD, the development of a practical parameter estimation procedure is indispensable before the global implementation of the developed scheme of water table dynamics in climate models.

scholarly journals Interactive coupling of regional atmosphere with biosphere in the new generation regional climate system model REMO-iMOVE

2014 ◽  
Vol 7 (3) ◽  
pp. 1093-1114 ◽  
Author(s):  
C. Wilhelm ◽  
D. Rechid ◽  
D. Jacob
Keyword(s):  
Land Surface ◽  
Regional Climate ◽  
Regional Model ◽  
Horizontal Resolution ◽  
Soil Conditions ◽  
Data Sets ◽  
Vegetation Phenology ◽  
Land Surface Scheme ◽  
New Model ◽  
Surface Scheme

Abstract. The main objective of this study is the coupling of the regional climate model REMO with a new land surface scheme including dynamic vegetation phenology, and the evaluation of the new model version called REMO with interactive MOsaic-based VEgetation: REMO-iMOVE. First, we focus on the documentation of the technical aspects of the new model constituents and the coupling mechanism. The representation of vegetation in iMOVE is based on plant functional types (PFTs). Their geographical distribution is prescribed to the model which can be derived from different land surface data sets. Here, the PFT distribution is derived from the GLOBCOVER 2000 data set which is available on 1 km × 1 km horizontal resolution. Plant physiological processes like photosynthesis, respiration and transpiration are incorporated into the model. The vegetation modules are fully coupled to atmosphere and soil. In this way, plant physiological activity is directly driven by atmospheric and soil conditions at the model time step (two minutes to some seconds). In turn, the vegetation processes and properties influence the exchange of substances, energy and momentum between land and atmosphere. With the new coupled regional model system, dynamic feedbacks between vegetation, soil and atmosphere are represented at regional to local scale. In the evaluation part, we compare simulation results of REMO-iMOVE and of the reference version REMO2009 to multiple observation data sets of temperature, precipitation, latent heat flux, leaf area index and net primary production, in order to investigate the sensitivity of the regional model to the new land surface scheme and to evaluate the performance of both model versions. Simulations for the regional model domain Europe on a horizontal resolution of 0.44° had been carried out for the time period 1995–2005, forced with ECMWF ERA-Interim reanalyses data as lateral boundary conditions. REMO-iMOVE is able to simulate the European climate with the same quality as the parent model REMO2009. Differences in near-surface climate parameters can be restricted to some regions and are mainly related to the new representation of vegetation phenology. The seasonal and interannual variations in growth and senescence of vegetation are captured by the model. The net primary productivity lies in the range of observed values for most European regions. This study reveals the need for implementing vertical soil water dynamics in order to differentiate the access of plants to water due to different rooting depths. This gets especially important if the model will be used in dynamic vegetation studies.

scholarly journals Sensitivity study of the regional climate model RegCM4 to different convective schemes over West Africa

2018 ◽  
Vol 9 (4) ◽  
pp. 1261-1278 ◽  
Author(s):  
Brahima Koné ◽  
Arona Diedhiou ◽  
N'datchoh Evelyne Touré ◽  
Mouhamadou Bamba Sylla ◽  
Filippo Giorgi ◽  
...  
Keyword(s):  
West Africa ◽  
Land Surface ◽  
West African ◽  
Cold Bias ◽  
The West ◽  
Land Surface Scheme ◽  
African Climate ◽  
Sensitivity Studies ◽  
Surface Scheme ◽  
Convective Scheme

Abstract. The latest version of RegCM4 with CLM4.5 as a land surface scheme was used to assess the performance and sensitivity of the simulated West African climate system to different convection schemes. The sensitivity studies were performed over the West African domain from November 2002 to December 2004 at a spatial resolution of 50 km × 50 km and involved five convective schemes: (i) Emanuel; (ii) Grell; (iii) Emanuel over land and Grell over ocean (Mix1); (iv) Grell over land and Emanuel over ocean (Mix2); and (v) Tiedtke. All simulations were forced with ERA-Interim data. Validation of surface temperature at 2 m and precipitation were conducted using data from the Climate Research Unit (CRU), Global Precipitation Climatology Project (GPCP) and the Tropical Rainfall Measurement Mission (TRMM) during June to September (rainy season), while the simulated atmospheric dynamic was compared to ERA-Interim data. It is worth noting that the few previous similar sensitivity studies conducted in the region were performed using BATS as a land surface scheme and involved less convective schemes. Compared with the previous version of RegCM, RegCM4-CLM also shows a general cold bias over West Africa whatever the convective scheme used. This cold bias is more reduced when using the Emanuel convective scheme. In terms of precipitation, the dominant feature in model simulations is a dry bias that is better reduced when using the Emanuel convective scheme. Considering the good performance with respect to a quantitative evaluation of the temperature and precipitation simulations over the entire West African domain and its subregions, the Emanuel convective scheme is recommended for the study of the West African climate system.

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