scholarly journals Building a field- and model-based climatology of local water and energy cycles in the cultivated Sahel – annual budgets and seasonality

2014 ◽  
Vol 11 (5) ◽  
pp. 4753-4808 ◽  
Author(s):  
C. Velluet ◽  
J. Demarty ◽  
B. Cappelaere ◽  
I. Braud ◽  
H. B.-A. Issoufou ◽  
...  
Keyword(s):  
Land Surface ◽  
Regional Climate ◽  
Surface Fluxes ◽  
Process Understanding ◽  
Land Use Types ◽  
Physically Based ◽  
Data Imprecision ◽  
Local Water ◽  
Physical Laws ◽  
And Storage

Abstract. In the African Sahel, energy and water cycling at the land surface is pivotal for regional climate, water resources and land productivity, yet it is still extremely poorly documented. As a step towards a comprehensive climatological description of surface fluxes in this area, this study provides estimates of average annual budgets and seasonal cycles for two main land use types of the cultivated Sahelian belt, rainfed millet crop and fallow bush. These estimates build on the combination of a 7 year field dataset from two typical plots in southwestern Niger with detailed physically-based soil-plant-atmosphere modelling, yielding a continuous, comprehensive set of water and energy flux and storage variables over the 7 year period. In this study case in particular, blending field data with mechanistic modelling is considered as making best use of available data and knowledge for such purpose. It extends observations by reconstructing missing data and extrapolating to unobserved variables or periods. Furthermore, model constraining with observations compromises between extraction of observational information content and integration of process understanding, hence accounting for data imprecision and departure from physical laws. Climatological averages of all water and energy variables, with associated sampling uncertainty, are derived at annual to subseasonal scales from the 7 year series produced. Similarities and differences in the two ecosystems behaviors are highlighted. Mean annual evapotranspiration is found to represent ~82–85% of rainfall for both systems, but with different soil evaporation/plant transpiration partitioning and different seasonal distribution. The remainder consists entirely of runoff for the fallow, whereas drainage and runoff stand in a 40–60% proportion for the millet field. These results should provide a robust reference for the surface energy- and water-related studies needed in this region. The model developed in this context has the potential for reliable simulations outside the reported conditions, including changing climate and land cover.

scholarly journals Effects of Land Surface Schemes on WRF-Simulated Geopotential Heights over China in Summer 2003*

2016 ◽  
Vol 17 (3) ◽  
pp. 829-851 ◽  
Author(s):  
Xin-Min Zeng ◽  
B. Wang ◽  
Y. Zhang ◽  
Y. Zheng ◽  
N. Wang ◽  
...  
Keyword(s):  
Land Surface ◽  
Climate Models ◽  
Regional Climate ◽  
Sensible Heat Flux ◽  
Wrf Model ◽  
Surface Fluxes ◽  
Forecast Errors ◽  
Large Area ◽  
Pressure Fields ◽  
Temperature And Pressure

Abstract To quantify and explain effects of different land surface schemes (LSSs) on simulated geopotential height (GPH) fields, we performed simulations over China for the summer of 2003 using 12-member ensembles with the Weather Research and Forecasting (WRF) Model, version 3. The results show that while the model can generally simulate the seasonal and monthly mean GPH patterns, the effects of the LSS choice on simulated GPH fields are substantial, with the LSS-induced differences exceeding 10 gpm over a large area (especially the northwest) of China, which is very large compared with climate anomalies and forecast errors. In terms of the assessment measures for the four LSS ensembles [namely, the five-layer thermal diffusion scheme (SLAB), the Noah LSS (NOAH), the Rapid Update Cycle LSS (RUC), and the Pleim–Xiu LSS (PLEX)] in the WRF, the PLEX ensemble is the best, followed by the NOAH, RUC, and SLAB ensembles. The sensitivity of the simulated 850-hPa GPH is more significant than that of the 500-hPa GPH, with the 500-hPa GPH difference fields generally characterized by two large areas with opposite signs due to the smoothly varying nature of GPHs. LSS-induced GPH sensitivity is found to be higher than the GPH sensitivity induced by atmospheric boundary layer schemes. Moreover, theoretical analyses show that the LSS-induced GPH sensitivity is mainly caused by changes in surface fluxes (in particular, sensible heat flux), which further modify atmospheric temperature and pressure fields. The temperature and pressure fields generally have opposite contributions to changes in the GPH. This study emphasizes the importance of choosing and improving LSSs for simulating seasonal and monthly GPHs using regional climate models.

scholarly journals Effects of Surface Coupling Strength in WRF/Noah-MP Model on Regional Climate Simulations Over China

2021 ◽  
Author(s):  
Xia Zhang ◽  
Liang Chen ◽  
Zhuguo Ma ◽  
Jianping Duan ◽  
Danqiong Dai ◽  
...  
Keyword(s):  
Coupling Strength ◽  
Land Surface ◽  
Numerical Models ◽  
Exchange Process ◽  
Regional Climate ◽  
Surface Fluxes ◽  
Surface Model ◽  
Surface Exchange ◽  
Climate Simulations ◽  
Simulated Precipitation

Abstract Land–atmosphere energy and moisture exchange can strongly influence local and regional climate. However, high uncertainty exits in the representation of land–atmosphere interactions in numerical models. The parameterization of surface exchange process is greatly affected by varying the parameter Czil which, however, is typically set to a domain-wide constant value. In this study, we examine the sensitivity of regional climate simulations over China to different surface exchange strengths using three Czil schemes (default without Czil , constant Czil = 0.1, and dynamic canopy-height-dependent Czil -h schemes) in the 13-km-resolution Weather Research and Forecasting model coupled with a Noah land surface model with multi-parameterization options (WRF/Noah-MP). Our results demonstrate that the Czil -h scheme substantially reduces the overestimations of land–atmosphere coupling strength in the other two schemes, and comparisons with the ChinaFLUX observations indicate the capability of the Czil -h scheme to better match the observed surface energy and water variations. The results of the Czil schemes applying to four typical climate zones of China present that the Czil -h simulations are in the closest agreements with the field observations. The Czil -h scheme can narrow the positive discrepancies of simulated precipitation and surface fluxes as well as the negative biases of Ts in areas of Northeast, North China, Eastern Northwest, and Southwest. Especially, the above remarkable improvements produced by the Czil -h scheme are primarily over areas covering short vegetation. Also noted that the precipitation simulated by the Czil -h scheme exhibits more intricate and unclear changes compared with surface fluxes simulations due to the non-local impacts of surface exchange strength resulted from the fluidity of the atmosphere. Overall, our findings highlight the applicability of the dynamical Czil as a better physical alternative to treat the surface exchange process in atmosphere coupling models.

scholarly journals Soil Control on Runoff Response to Climate Change in Regional Climate Model Simulations

2005 ◽  
Vol 18 (17) ◽  
pp. 3536-3551 ◽  
Author(s):  
Bart van den Hurk ◽  
Martin Hirschi ◽  
Christoph Schär ◽  
Geert Lenderink ◽  
Erik van Meijgaard ◽  
...  
Keyword(s):  
Climate Change ◽  
Annual Cycle ◽  
Land Surface ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Water Storage ◽  
Climate Simulation ◽  
Discharge Data ◽  
And Storage

Abstract Simulations with seven regional climate models driven by a common control climate simulation of a GCM carried out for Europe in the context of the (European Union) EU-funded Prediction of Regional scenarios and Uncertainties for Defining European Climate change risks and Effects (PRUDENCE) project were analyzed with respect to land surface hydrology in the Rhine basin. In particular, the annual cycle of the terrestrial water storage was compared to analyses based on the 40-yr ECMWF Re-Analysis (ERA-40) atmospheric convergence and observed Rhine discharge data. In addition, an analysis was made of the partitioning of convergence anomalies over anomalies in runoff and storage. This analysis revealed that most models underestimate the size of the water storage and consequently overestimated the response of runoff to anomalies in net convergence. The partitioning of these anomalies over runoff and storage was indicative for the response of the simulated runoff to a projected climate change consistent with the greenhouse gas A2 Synthesis Report on Emission Scenarios (SRES). In particular, the annual cycle of runoff is affected largely by the terrestrial storage reservoir. Larger storage capacity leads to smaller changes in both wintertime and summertime monthly mean runoff. The sustained summertime evaporation resulting from larger storage reservoirs may have a noticeable impact on the summertime surface temperature projections.

scholarly journals Role of land surface processes and diffuse/direct radiation partitioning in simulating the European climate

2012 ◽  
Vol 9 (5) ◽  
pp. 1695-1707 ◽  
Author(s):  
E. L. Davin ◽  
S. I. Seneviratne
Keyword(s):  
Land Surface ◽  
Regional Climate ◽  
Summer Temperature ◽  
Surface Fluxes ◽  
Surface Processes ◽  
Land Surface Processes ◽  
Direct Radiation ◽  
Atmospheric Component ◽  
Direct Light ◽  
Light Partitioning

Abstract. The influence of land processes and in particular of diffuse/direct radiation partitioning on surface fluxes and associated regional-scale climate feedbacks is investigated using ERA-40 driven simulations over Europe performed with the COSMO-CLM2 Regional Climate Model (RCM). Two alternative Land Surface Models (LSMs), a 2nd generation LSM (TERRA_ML) and a more advanced 3rd generation LSM (Community Land Model version 3.5), and two versions of the atmospheric component are tested, as well as a revised coupling procedure allowing for variations in diffuse/direct light partitioning at the surface, and their accounting by the land surface component. Overall, the RCM performance for various variables (e.g., surface fluxes, temperature and precipitation) is improved when using the more advanced 3rd generation LSM. These improvements are of the same order of magnitude as those arising from a new version of the atmospheric component, demonstrating the benefit of using a realistic representation of land surface processes for regional climate simulations. Taking into account the variability in diffuse/direct light partitioning at the surface further improves the model performance in terms of summer temperature variability at the monthly and daily time scales. Comparisons with observations show that the RCM realistically captures temporal variations in diffuse/direct light partitioning as well as the evapotranspiration sensitivity to these variations. Our results suggest that a modest but consistent fraction (up to 3 %) of the overall variability in summer temperature can be explained by variations in the diffuse to direct ratio.

scholarly journals The impact of snow loss and soil moisture on convective precipitation over the Rocky Mountains under climate warming

2021 ◽  
Author(s):  
Brendan Wallace ◽  
Justin R. Minder
Keyword(s):  
Soil Moisture ◽  
Snow Cover ◽  
Rocky Mountains ◽  
Land Surface ◽  
Regional Climate ◽  
Warm Season ◽  
Surface Fluxes ◽  
Convective Precipitation ◽  
Precipitation Frequency ◽  
The Impact

AbstractWarm season moist diurnal convection can be particularly sensitive to changes in land surface characteristics such as snow cover and soil moisture. Over regions of mountainous terrain, climate change is expected to reduce snow cover along the low-elevation seasonal snowpack margin. These snow reductions alter surface albedo and soil moisture content, leading to changes in surface fluxes and alterations in mesoscale orographic circulations that act to transport moisture and provide ascent. A set of convection-permitting regional climate simulations centered on the Rocky Mountains of Colorado are conducted from April through July across a period of 12 years (2002–2013). These include a reanalysis forced control run (CTR), a pseudo global warming run (PGW), and an additional altered land surface run (DSURF) used to isolate the effects of the snow albedo and soil moisture changes on orographic convection. Over the mountains, daytime hourly precipitation accumulation (0900–1800 MST) decreased in PGW by an average of 4.2% while precipitation in DSURF increased by 12.5%. On days with weak synoptic forcing, the PGW response more closely follow the DSURF response with daytime hourly increases averaging 29.7% for PGW and 28.7% for DSURF. For PGW, hourly daytime precipitation intensity increases of up to 82% overcome reductions in precipitation frequency to produce higher accumulations. DSURF shows smaller increases in intensity of up to 23% and broad increases in daytime frequency indicating that surface changes act to moderate reductions in the frequency of convective precipitation. Reduced snow cover contributes to this convective response by increasing convective instability and boundary layer moisture and decreasing lifting condensation level over the high terrain. Alterations in orographic thermal circulations contribute to this response by converging moisture over the high terrain and enhancing mesoscale ascent.

scholarly journals Hydroclimatology of the Nile: results from a regional climate model

2005 ◽  
Vol 2 (1) ◽  
pp. 319-364 ◽  
Author(s):  
Y. A. Mohamed ◽  
B. J. J. M. van den Hurk ◽  
H. H. G. Savenije ◽  
W. G. M. Bastiaanssen
Keyword(s):  
Land Surface ◽  
Climate Model ◽  
Water Cycle ◽  
Regional Climate ◽  
Hydrologic Model ◽  
Surface Fluxes ◽  
Monthly Precipitation ◽  
Moisture Recycling ◽  
White Nile ◽  
Regional Water

Abstract. This paper is the result of the first regional coupled climatic and hydrologic model of the Nile. For the first time the interaction between the climatic processes and the hydrological processes on the land surface have been fully coupled. The hydrological model is driven by the rainfall and the energy available for evaporation generated in the climate model, and the runoff generated in the catchment is again routed over the wetlands of the Nile to supply moisture for atmospheric feedback. The results obtained are surprisingly accurate given the extremely low runoff coefficients in the catchment. The paper presents model results over the sub-basins: Blue Nile, White Nile, Atbara river and the Main Nile for the period 1995 to 2000, but focuses on the Sudd swamp. Limitations in both the observational data and the model are discussed. It is concluded that the model provides a sound representation of the regional water cycle over the Nile. The model is used to describe the regional water cycle in the Nile basin in terms of atmospheric fluxes, land surface fluxes and land surface-climate feedbacks. The monthly moisture recycling ratio (i.e. locally generated/total precipitation) over the Nile varies between 8 and 14%, with an annual mean of 11%, which implies that 89% of the Nile water resources originates from outside the basin physical boundaries. The monthly precipitation efficiency varies between 12 and 53%, and the annual mean is 28%. The mean annual result of the Nile regional water cycle is compared to that of the Amazon and the Mississippi basins.

scholarly journals Role of land surface processes and diffuse/direct radiation partitioning in simulating the European climate

2011 ◽  
Vol 8 (6) ◽  
pp. 11601-11630 ◽  
Author(s):  
E. L. Davin ◽  
S. I. Seneviratne
Keyword(s):  
Land Surface ◽  
Regional Climate ◽  
Summer Temperature ◽  
Surface Fluxes ◽  
Surface Processes ◽  
Land Surface Processes ◽  
Direct Radiation ◽  
Atmospheric Component ◽  
Direct Light ◽  
Light Partitioning

Abstract. The influence of land processes and in particular of diffuse/direct radiation partitioning on surface fluxes and associated regional-scale climate feedbacks is investigated. ERA-40 driven simulations over Europe are performed using the COSMO-CLM2 Regional Climate Model (RCM). Two alternative Land Surface Models (LSMs), a 2nd generation LSM (TERRA_ML) and a more advanced 3rd generation LSM (Community Land Model version 3.5), and two versions of the atmospheric component are tested, as well as a revised coupling procedure allowing for variations in diffuse/direct light partitioning at the surface, and their accounting by the land surface component. Overall, the RCM performance for various variables (e.g., surface fluxes, temperature and precipitation) is improved when using the more advanced 3rd generation LSM. These improvements are of the same order of magnitude as those arising from a new version of the atmospheric component, demonstrating the benefit of using a realistic representation of land surface processes for regional climate simulations. Taking into account variability in diffuse/direct light partitioning at the surface further improves the model performance in terms of summer temperature variability at the monthly and daily time scales. Comparisons with observations show that the RCM realistically captures temporal variations in diffuse/direct light partitioning as well as the evapotranspiration sensitivity to these variations. Our results suggest that a modest but consistent fraction (up to 3 %) of the overall variability in summer temperature can be explained by variations in the diffuse to direct ratio.

scholarly journals Building a field- and model-based climatology of local water and energy cycles in the cultivated Sahel – annual budgets and seasonality

2014 ◽  
Vol 18 (12) ◽  
pp. 5001-5024 ◽  
Author(s):  
C. Velluet ◽  
J. Demarty ◽  
B. Cappelaere ◽  
I. Braud ◽  
H. B.-A. Issoufou ◽  
...  
Keyword(s):  
Time Series ◽  
Land Surface ◽  
Field Data ◽  
Model Simulation ◽  
Regional Climate ◽  
Multivariate Time Series ◽  
Surface Fluxes ◽  
Mechanistic Modeling ◽  
Data Set ◽  
Sub Saharan

Abstract. In the sub-Saharan Sahel, energy and water cycling at the land surface is pivotal for the regional climate, water resources and land productivity, yet it is still very poorly documented. As a step towards a comprehensive climatological description of surface fluxes in this area, this study provides estimates of long-term average annual budgets and seasonal cycles for two main land use types of the cultivated Sahelian belt: rainfed millet crop and fallow bush. These estimates build on the combination of a 7-year field data set from two typical plots in southwestern Niger with detailed physically based soil–plant–atmosphere modeling, yielding a continuous, comprehensive set of water and energy flux and storage variables over this multiyear period. In the present case in particular, blending field data with mechanistic modeling makes the best use of available data and knowledge for the construction of the multivariate time series. Rather than using the model only to gap-fill observations into a composite series, model–data integration is generalized homogeneously over time by generating the whole series with the entire data-constrained model simulation. Climatological averages of all water and energy variables, with associated sampling uncertainty, are derived at annual to sub-seasonal scales from the time series produced. Similarities and differences in the two ecosystem behaviors are highlighted. Mean annual evapotranspiration is found to represent ~82–85% of rainfall for both systems, but with different soil evaporation/plant transpiration partitioning and different seasonal distribution. The remainder consists entirely of runoff for the fallow, whereas drainage and runoff stand in a 40–60% proportion for the millet field. These results should provide a robust reference for the surface energy- and water-related studies needed in this region. Their significance and the benefits they gain from the innovative data–model integration approach are thoroughly discussed. The model developed in this context has the potential for reliable simulations outside the reported conditions, including changing climate and land cover.

scholarly journals Hydroclimatology of the Nile: results from a regional climate model

2005 ◽  
Vol 9 (3) ◽  
pp. 263-278 ◽  
Author(s):  
Y. A. Mohamed ◽  
B. J. J. M. van den Hurk ◽  
H. H. G. Savenije ◽  
W. G. M. Bastiaanssen
Keyword(s):  
Land Surface ◽  
Climate Model ◽  
Water Cycle ◽  
Regional Climate ◽  
Hydrologic Model ◽  
Surface Fluxes ◽  
Monthly Precipitation ◽  
Nile Basin ◽  
Moisture Recycling ◽  
Regional Water

Abstract. This paper presents the result of the regional coupled climatic and hydrologic model of the Nile Basin. For the first time the interaction between the climatic processes and the hydrological processes on the land surface have been fully coupled. The hydrological model is driven by the rainfall and the energy available for evaporation generated in the climate model, and the runoff generated in the catchment is again routed over the wetlands of the Nile to supply moisture for atmospheric feedback. The results obtained are quite satisfactory given the extremely low runoff coefficients in the catchment. The paper presents the validation results over the sub-basins: Blue Nile, White Nile, Atbara river, the Sudd swamps, and the Main Nile for the period 1995 to 2000. Observational datasets were used to evaluate the model results including radiation, precipitation, runoff and evaporation data. The evaporation data were derived from satellite images over a major part of the Upper Nile. Limitations in both the observational data and the model are discussed. It is concluded that the model provides a sound representation of the regional water cycle over the Nile. The sources of atmospheric moisture to the basin, and location of convergence/divergence fields could be accurately illustrated. The model is used to describe the regional water cycle in the Nile basin in terms of atmospheric fluxes, land surface fluxes and land surface-climate feedbacks. The monthly moisture recycling ratio (i.e. locally generated/total precipitation) over the Nile varies between 8 and 14%, with an annual mean of 11%, which implies that 89% of the Nile water resources originates from outside the basin physical boundaries. The monthly precipitation efficiency varies between 12 and 53%, and the annual mean is 28%. The mean annual result of the Nile regional water cycle is compared to that of the Amazon and the Mississippi basins.

scholarly journals SCOPE 2.0: A model to simulate vegetated land surface fluxes and satellite signals

2020 ◽  
Author(s):  
Peiqi Yang ◽  
Egor Prikaziuk ◽  
Wout Verhoef ◽  
Christiaan van der Tol
Keyword(s):  
Remote Sensing ◽  
Land Surface ◽  
Heat Dissipation ◽  
Chlorophyll Concentration ◽  
Vertical Gradient ◽  
Surface Fluxes ◽  
Canopy Reflectance ◽  
Physically Based ◽  
Vegetation Canopies ◽  
Definition Of

Abstract. The Soil Canopy Observation of Photosynthesis and Energy fluxes (SCOPE) model aims at linking satellite observations in the visible, infrared and thermal domains with land surface processes in a physically based manner, and quantifying the micro-climate in the canopy. It simulates radiative transfer in the soil, leaves and vegetation canopies, as well as photosynthesis and non-radiative heat dissipation through convection and mechanical turbulence. Since the first publication 11 years ago, SCOPE has been applied in remote sensing studies of solar-induced chlorophyll fluorescence (SIF), energy balance fluxes, gross primary productivity (GPP) and directional thermal signals. Here we present a thoroughly revised version, SCOPE 2.0, which features a number of new elements: (1) It enables the definition of layers consisting of leaves with different properties, thus enabling the simulation of vegetation with an understory or with a vertical gradient in leaf chlorophyll concentration; (2) It enables the simulation of soil reflectance; (3) It includes the simulation of leaf and canopy reflectance changes induced by the xanthophyll cycle; and (4) The computation speed has been reduced by 90 % compared to earlier versions due to a fundamental optimization of the model. These new features improve the capability of the model to represent complex canopies and to explore the response of remote sensing signals to vegetation physiology. The improvements in the computational efficiency make it possible to use SCOPE 2.0 routinely for the simulation of satellite data and land surface fluxes. It also strengthens the operability for the numerical retrieval of land surface products from satellite or airborne data.

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