Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment (LIAISE): 1st modelling intercomparison

2021 ◽  
Author(s):  
Maria A. Jiménez ◽  
Joan Cuxart ◽  
Antoni Grau ◽  
Aaron Boone ◽  
Sylvie Donier ◽  
...  
Keyword(s):  
Land Surface ◽  
Numerical Models ◽  
Remote Sensing Data ◽  
Arid Environment ◽  
Surface Interactions ◽  
Surface Fluxes ◽  
Atmospheric Measurements ◽  
Pressure System ◽  
Mesoscale Circulations ◽  
Semi Arid

<p>Land surface-atmosphere interactions determine the atmospheric boundary layer  (ABL) features, and in the case of semi-arid regions the water availability in the upper ground strongly conditions the surface energy balance and in general the observed dominant processes. LIAISE (Land surface Interactions with the Atmosphere over the Iberian Semi-arid Environment, eastern Ebro sub-basin) is an observational campaign planned between spring and fall 2021 designed to study the land/atmosphere interactions and the effect of the surface heterogeneities on the ABL in a semi-arid environment enclosing a large irrigated area in summer.</p><p>The combined analysis of the ground-based observations and ABL atmospheric measurements, including aircraft and remote-sensing data, is expected to improve the understanding of processes affecting exchange fluxes between the surface and the atmosphere, especially evapotranspiration, and to allow exploring the local and mesoscale circulations induced by the surface heterogeneities. In this sense, mesoscale simulations will be performed over the eastern Ebro sub-basin to contribute to this understanding while evaluating the representation of the surface features in the numerical models and its impact in the organisation of the flow at lower levels.</p><p>A first mesoscale modelling inter-comparison for a 2016 summer event in the LIAISE area, is under progress, intended to evaluate the performance of the participating models compared to the observations and explore the differences between them, trying to understand the reasons behind them. In this initial phase the models are run at their standard configurations and the comparison is expected to allow improvements in the definitions of the setup of each model for a later phase.</p><p>Four models participate in the inter-comparison: MesoNH, WRF, UKMO Unified Model and MOLOCH. They are run with similar horizontal (2km x 2km and 400m x 400m for the outer and inner domains) and vertical (2m at lower levels and stretched above) grid meshes and, in this first phase, using their default setup. A 48-h integration is made between 16 and 18 July 2016 for a case under a high-pressure system centred over NW France, with well developed thermally-driven circulations in the Ebro Basin. Sea breezes are found at the coast and seem to reach the basin after surmounting the mountain coastal range.</p><p>Preliminary results show that each model has a different representation of the surface heterogeneities affecting the grid values of the surface fluxes. Nevertheless, the mesoscale circulations generated by them do not differ significantly between models, the differences lying mostly at smaller scales, namely the ABL characteristics, the values of the exchange fluxes at the surface or the state of the surface and the soil. The challenge at this point is to relate the observed differences to the particularities of the parameterisations and of the physiographic data bases used by each model.</p><p> </p>

scholarly journals Modeling the Effect of Desert Urbanization on Local Climate and Natural Dust Generation: A Case Study for Erbil, Iraq

Urban Science ◽  
2020 ◽  
Vol 4 (4) ◽  
pp. 46
Author(s):  
Sherzad T. Tahir ◽  
Huei-Ping Huang
Keyword(s):  
Land Surface ◽  
Numerical Models ◽  
Surface Wind ◽  
Surface Fluxes ◽  
Slight Reduction ◽  
Rapid Urbanization ◽  
Near Surface ◽  
Local Climate ◽  
Surface Dust ◽  
Dust Generation

This study uses a suite of meteorological and land-surface models to quantify the changes in local climate and surface dust fluxes associated with desert urbanization. Formulas connecting friction velocity and soil moisture to dust generation are used to quantify surface fluxes for natural wind-blown dust. The models are used to conduct a series of simulations for the desert city of Erbil across a period of rapid urbanization. The results show significant nighttime warming and weak but robust daytime cooling associated with desert urbanization. A slight reduction in near-surface wind speed is also found in the areas undergoing urbanization. These findings are consistent with previous empirical and modeling studies on other desert cities. Numerical models and empirical formulas are used to produce climatological maps of surface dust fluxes as a function of season, and for the pre- and post-urbanization eras. This framework can potentially be used to bridge the gap in observation on the trends in local dust generation associated with land-use changes and urban expansions.

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 Assessment of actual evapotranspiration over a semi-arid heterogeneous land surface by means of coupled low resolution remote sensing data with energy balance model: comparison to extra Large Aperture Scintillometer measurements

2017 ◽  
Author(s):  
Sameh Saadi ◽  
Gilles Boulet ◽  
Malik Bahir ◽  
Aurore Brut ◽  
Bernard Mougenot ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Heat Flux ◽  
Water Stress ◽  
Latent Heat ◽  
Water Availability ◽  
Land Surface ◽  
Remote Sensing Data ◽  
Sparse Model ◽  
Sensing Data ◽  
Semi Arid

Abstract. In semi-arid areas, agricultural production is restricted by water availability; hence efficient agricultural water management is a major issue. The design of tools providing regional estimates of evapotranspiration (ET), one of the most relevant water balance fluxes, may help the sustainable management of water resources. Remote sensing provides periodic data about actual vegetation temporal dynamics (through the Normalized Difference Vegetation Index NDVI) and water availability under water stress (through the land surface temperature LST) which are crucial factors controlling ET. In this study, spatially distributed estimates of ET (or its energy equivalent, the latent heat fluxes LE) in the Kairouan plain (Central Tunisia) were computed by applying the Soil Plant Atmosphere and Remote Sensing Evapotraspiration (SPARSE) model fed by low resolution remote sensing data (Terra and Aqua MODIS). The work goal was to assess the operational use of the SPARSE model and the accuracy of the modelled i) sensible heat flux (H) and ii) daily ET over a heterogeneous semi-arid landscape with a complex land cover (i.e. trees, winter cereals, summer vegetables). The SPARSE's layer approach was run to compute instantaneous estimates of H and LE fluxes at the satellite overpass time. The good correspondence (R2 = 0.60 and 0.63 and RMSE = 57.89 W/m-2 and 53.85 W/m-2; for Terra and Aqua, respectively) between instantaneous H estimates and large aperture scintillometer (XLAS)'s H measurements along a pathlength of 4 km over the study area showed that the SPARSE model presents satisfactory accuracy. Results showed that, despite the fairly large scatter, the instantaneous LE can be suitably estimated at large scale (RMSE = 47.20 W/m-2 and 43.20 W/m-2; for Terra and Aqua, respectively and R2 = 0.55 for both satellites). Additionally, water stress was investigated by comparing modelled (SPARSE derived) to observed (XLAS derived) water stress values; we found that most points were located within a 0.2 confidence interval, thus the general tendencies are well reproduced. Even though extrapolation of instantaneous latent heat flux values to daily totals was less obvious, daily ET estimates are deemed acceptable.

scholarly journals Quantifying the impact of groundwater depth on evapotranspiration in a semi-arid grassland region

2011 ◽  
Vol 15 (3) ◽  
pp. 787-806 ◽  
Author(s):  
M. E. Soylu ◽  
E. Istanbulluoglu ◽  
J. D. Lenters ◽  
T. Wang
Keyword(s):  
Soil Moisture ◽  
Water Table ◽  
Soil Texture ◽  
Land Surface ◽  
Surface Interactions ◽  
Water Table Depth ◽  
Richards Equation ◽  
Hydraulic Parameter ◽  
Soil Hydraulic ◽  
Semi Arid

Abstract. Interactions between shallow groundwater and land surface processes play an important role in the ecohydrology of riparian zones. Some recent land surface models (LSMs) incorporate groundwater-land surface interactions using parameterizations at varying levels of detail. In this paper, we examine the sensitivity of land surface evapotranspiration (ET) to water table depth, soil texture, and two commonly used soil hydraulic parameter datasets using four models with varying levels of complexity. The selected models are Hydrus-1D, which solves the pressure-based Richards equation, the Integrated Biosphere Simulator (IBIS), which simulates interactions among multiple soil layers using a (water-content) variant of the Richards equation, and two forms of a steady-state capillary flux model coupled with a single-bucket soil moisture model. These models are first evaluated using field observations of climate, soil moisture, and groundwater levels at a semi-arid site in south-central Nebraska, USA. All four models are found to compare reasonably well with observations, particularly when the effects of groundwater are included. We then examine the sensitivity of modelled ET to water table depth for various model formulations, node spacings, and soil textures (using soil hydraulic parameter values from two different sources, namely Rawls and Clapp-Hornberger). The results indicate a strong influence of soil texture and water table depth on groundwater contributions to ET. Furthermore, differences in texture-specific, class-averaged soil parameters obtained from the two literature sources lead to large differences in the simulated depth and thickness of the "critical zone" (i.e., the zone within which variations in water table depth strongly impact surface ET). Depending on the depth-to-groundwater, this can also lead to large discrepancies in simulated ET (in some cases by more than a factor of two). When the Clapp-Hornberger soil parameter dataset is used, the critical zone becomes significantly deeper, and surface ET rates become much higher, resulting in a stronger influence of deep groundwater on the land surface energy and water balance. In general, we find that the simulated sensitivity of ET to the choice of soil hydraulic parameter dataset is greater than the sensitivity to soil texture defined within each dataset, or even to the choice of model formulation. Thus, our findings underscore the need for future modelling and field-based studies to improve the predictability of groundwater-land surface interactions in numerical models, particularly as it relates to the parameterization of soil hydraulic properties.

scholarly journals Land surface spinup for episodic modeling

2014 ◽  
Vol 14 (15) ◽  
pp. 8165-8172 ◽  
Author(s):  
W. M. Angevine ◽  
E. Bazile ◽  
D. Legain ◽  
D. Pino
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Spatial Variability ◽  
Land Surface ◽  
Large Scale ◽  
Layer Structure ◽  
Numerical Models ◽  
Surface Fluxes ◽  
Boundary Layer Structure ◽  
Soil Variables

Abstract. Soil moisture strongly controls the surface fluxes in mesoscale numerical models, and thereby influences the boundary layer structure. Proper initialization of soil moisture is therefore critical for faithful simulations. In many applications, such as air quality or process studies, the model is run for short, discrete periods (a day to a month). This paper describes one method for soil initialization in these cases – self-spinup. In self-spinup, the model is initialized with a coarse-resolution operational model or reanalysis output, and run for a month, cycling its own soil variables. This allows the soil variables to develop appropriate spatial variability, and may improve the actual values. The month (or other period) can be run more than once if needed. The case shown is for the Boundary Layer Late Afternoon and Sunset Turbulence experiment, conducted in France in 2011. Self-spinup adds spatial variability, which improves the representation of soil moisture patterns around the experiment location, which is quite near the Pyrenees Mountains. The self-spinup also corrects a wet bias in the large-scale analysis. The overall result is a much-improved simulation of boundary layer structure, evaluated by comparison with soundings from the field site. Self-spinup is not recommended as a substitute for multi-year spinup with an offline land data assimilation system in circumstances where the data sets required for such spinup are available at the required resolution. Self-spinup may fail if the modeled precipitation is poorly simulated. It is an expedient for cases when resources are not available to allow a better method to be used.

scholarly journals Mapping irrigated areas using multi-sensor remote sensing data in a Mediterranean environment

2017 ◽  
Author(s):  
Pasquale Nino ◽  
Silvia Vanino ◽  
Flavio Lupia ◽  
Guido D'Urso ◽  
Carlo De Michele ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Remote Sensing Data ◽  
Arid Environment ◽  
Earth Observation ◽  
Irrigation District ◽  
Landsat 8 ◽  
Vegetation Development ◽  
Vegetation Growth ◽  
Growing Seasons ◽  
Semi Arid

Water managers need map of irrigated areas (defined as the identification of their location and their areal extent) to plan a rational use of water under limited availability and to prevent the unauthorized withdrawals. Many authors have shown that the Earth Observation techniques are an effective tool for mapping irrigated areas worldwide at different spatial scales (global/regional/and local). This study presents a methodology for mapping irrigated areas in semi-arid environment based on Earth Observation techniques and by fully exploiting datasets freely available processed by open source software and tools. Data acquired with the Landsat 8 Operational Land Imager (OLI) and the new Sentinel 2A MultiSpectral Instrument (MSI) sensors were integrated to obtain cloud free dense time series allowing to monitor the vegetation development throughout the growing seasons. Irrigated areas were identified by analysing the growing patterns under water deficit conditions from NDVI values under the assumption that, in arid and semi-arid environment (like the Mediterranean Region), high trend of vegetation growth are compatible only with irrigation. The method was applied inside the Cixerri Consortium Irrigation District located in South of Sardinia (Italy).

scholarly journals Mapping irrigated areas using multi-sensor remote sensing data in a Mediterranean environment

2017 ◽  
Author(s):  
Pasquale Nino ◽  
Silvia Vanino ◽  
Flavio Lupia ◽  
Guido D'Urso ◽  
Carlo De Michele ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Remote Sensing Data ◽  
Arid Environment ◽  
Earth Observation ◽  
Irrigation District ◽  
Landsat 8 ◽  
Vegetation Development ◽  
Vegetation Growth ◽  
Growing Seasons ◽  
Semi Arid

Water managers need map of irrigated areas (defined as the identification of their location and their areal extent) to plan a rational use of water under limited availability and to prevent the unauthorized withdrawals. Many authors have shown that the Earth Observation techniques are an effective tool for mapping irrigated areas worldwide at different spatial scales (global/regional/and local). This study presents a methodology for mapping irrigated areas in semi-arid environment based on Earth Observation techniques and by fully exploiting datasets freely available processed by open source software and tools. Data acquired with the Landsat 8 Operational Land Imager (OLI) and the new Sentinel 2A MultiSpectral Instrument (MSI) sensors were integrated to obtain cloud free dense time series allowing to monitor the vegetation development throughout the growing seasons. Irrigated areas were identified by analysing the growing patterns under water deficit conditions from NDVI values under the assumption that, in arid and semi-arid environment (like the Mediterranean Region), high trend of vegetation growth are compatible only with irrigation. The method was applied inside the Cixerri Consortium Irrigation District located in South of Sardinia (Italy).

Sign in / Sign up

Export Citation Format

Share Document