Micrometeorological Measurements Research Articles

Winter wheat water requirement and utilization efficiency under simulated climate change conditions: A Penman-Monteith model evaluation

Impact of climate change on water supply and use is a critical issue for dryland crop production. In this study is assessed the potential impact of atmospheric CO2 enrichment (500μmolmol−1, CE) and canopy warming (+2°C, WA) and their combination (CW) on crop water utilization efficiency (WUE) of winter wheat in an open-air field experiment from Southeast China. Micro-meteorological measurement and wheat growth under individual treatments over three executive years of 2012–2015 were used to estimate the crop water requirement (CWR) of wheat using an improved FAO Penman-Monteith equation. Overall, CO2 enrichment slightly decreased the CWR by 8.3%, and increased the WUE of grain production (WUEg) by 23.1%, averaged over the three years. In contrast, warming increased CWR by 19.6% but decreased WUEg by 27.9% over the period. Under CW treatment, however, CWR was increased by 3.1–15.8% but WUEg was decreased by 3.5–18.2% throughout three years. Clearly, the positive impact of CO2 enrichment on WUE was largely negated under canopy warming. Moreover, when assessing with individual year data, inter-annual variability of WUEg was insignificant under WA, smaller under CE but much higher under CW, compared to CK. These results indicated that an interaction by canopy warming overshadowed the potential increase in WUE with CO2 enrichment and enforced yearly fluctuation of the crop production under simulated climate change conditions. Therefore, improving water supply and management in agriculture should thus be endeavored to address the potential constraints with future trends of concurrent atmospheric CO2 enrichment and warming.

The urban heat island effect in Dutch city centres

In the Netherlands awareness regarding the Urban Heat Island (UHI) was raised relatively recently. Because of this recent understanding, there is a lack of consistent urban micro-meteorological measurements to allow a conventional UHI assessment of Dutch cities during heat waves. This paper argues that it is possible to retrieve relevant UHI information – including adaptation guidelines – from satellite imagery. The paper comprises three parts. The first part consists of a study of suited indicators to identify urban heat islands from which a method is presented based on ground heat flux mapping. The second part proposes heat mitigation strategies and identifies the areas where these strategies could be applied within the hotspots identified in the cities of The Hague, Delft, Leiden, Gouda, Utrecht and Den Bosch. The third part estimates the reduction of urban heat generated by the increase of roof albedo in the hotspots of the six cities. The six cities hotspots are located within the boundaries of the 17th century city centres. In order to avoid interference with cultural values of these historical environments most likely UHI mitigation measures regard improving the thermal behaviour of the city roofs. For instance, applying white coatings on bitumen flat roofs (or replacing them by white single-ply membranes) and replacing sloped roof clay tiles by coloured tiles with cool pigments can reduce the urban heat hotspots by approximately 1.5°C. Remote sensing provides high level information that provide urban planners and policy makers with overall design guidelines for the reduction of urban heat.

Contrasting variations in the surface layer structure between the convective and non-convective periods in the summer monsoon season for Bangalore location during PRWONAM

An attempt has been made here to examine the contrasting variations in mean surface layer parameters including surface fluxes, and in surface layer stability between the convective and non-convective periods in the southwest monsoon season for the Bangalore experiment location (12.54° N, 77.22° E). The micrometeorological measurements analysed during 2009 and 2010 are from the instrumentation network established during the programme, “Prediction of Regional Weather using Observational meso-Network and Atmospheric Modelling (PRWONAM)”.The Short Wave (SW) radiative flux at the surface is observed to be respectively at 799 ± 188 Wm−2 (772 ± 195 Wm−2) and 436 ± 113 Wm−2 (257 ± 101 Wm−2) at 12:00 LT (Local Time, UTC+05:30) during the non-convective and convective periods in 2009 (2010). The significant difference in SW radiative flux is due to the difference of cloud cover between the non-convective and convective periods. This significant reduction of 515 W m−2 at 12:00 LT in SW radiative flux caused maximum cooling in skin temperature (air temperature) by 6.2 °C (3.8 °C) at 12:00 LT (18:30 LT) from 30.8 ± 3.9 °C (27.1 ± 1.4 °C) in the non-convective period. The impact of convection on soil temperature is observed up to 0.2 m deep. The diurnal amplitudes in composites of air temperature are 8.4 °C (8.4 °C) and 5.7 °C (4.7 °C) during the non-convective and convective periods respectively in 2009 (2010); and the amplitudes in relative humidity are 41.5% (39.7%) and 29% (22.8%).Low wind speeds prevailed 63.4% of the time, all through the day and night, in the monsoon season. The diurnal variations in wind speed during the convective period showed higher variability than in non-convective period. The momentum flux varied in accordance with the strength of the wind speed during the monsoon seasons of both the years 2009 and 2010. The peak sensible heat flux in the convective period is noted to be smaller than that in the non-convective period by 128 W m−2 in 2009 and 124 W m−2 in 2010. The moisture flux showed no significant variations between the two periods. Sensible heat and moisture flux peaked up at 334 W m−2 and 258 W m−2 respectively at low wind strong unstable situation.

Early snowmelt significantly enhances boreal springtime carbon uptake

We determine the annual timing of spring recovery from space-borne microwave radiometer observations across northern hemisphere boreal evergreen forests for 1979-2014. We find a trend of advanced spring recovery of carbon uptake for this period, with a total average shift of 8.1 d (2.3 d/decade). We use this trend to estimate the corresponding changes in gross primary production (GPP) by applying in situ carbon flux observations. Micrometeorological CO2 measurements at four sites in northern Europe and North America indicate that such an advance in spring recovery would have increased the January-June GPP sum by 29 g⋅C⋅m-2 [8.4 g⋅C⋅m-2 (3.7%)/decade]. We find this sensitivity of the measured springtime GPP to the spring recovery to be in accordance with the corresponding sensitivity derived from simulations with a land ecosystem model coupled to a global circulation model. The model-predicted increase in springtime cumulative GPP was 0.035 Pg/decade [15.5 g⋅C⋅m-2 (6.8%)/decade] for Eurasian forests and 0.017 Pg/decade for forests in North America [9.8 g⋅C⋅m-2 (4.4%)/decade]. This change in the springtime sum of GPP related to the timing of spring snowmelt is quantified here for boreal evergreen forests.

A New Technique to Estimate Sensible Heat Fluxes around Micrometeorological Towers Using Small Unmanned Aircraft Systems

AbstractUpscaling point measurements from micrometeorological towers is a challenging task that is important for a variety of applications, for example, in process studies of convection initiation, carbon and energy budget studies, and the improvement of model parameterizations. In the present study, a technique was developed to determine the horizontal variability in sensible heat flux H surrounding micrometeorological towers. The technique was evaluated using 15-min flux observations, as well as measurements of land surface temperature and air temperature obtained from small unmanned aircraft systems (sUAS) conducted during a one-day measurement campaign. The computed H was found to be comparable to the micrometeorological measurements to within 5–10 W m−2. Furthermore, when comparing H computed using this technique with H determined using large-eddy simulations (LES), differences of <10 W m−2 were typically found. Thus, implementing this technique using observations from sUAS will help determine sensible heat flux variability at horizontal spatial scales larger than can be provided from flux tower measurements alone.

Designing Thermally Pleasant Open Areas: The Influence of Microclimatic Conditions on Comfort and Adaptation in Midwest Brazil

The increasing temperatures in urban areas can negatively affect the health and comfort of its dwellers. Thus, this study assessed thermal comfort conditions in a public square, located in hot-humid Midwest Brazil, based on the relationship between microclimate conditions, thermal sensations and adaptation. Data used were collected through micrometeorological measurements and questionnaire surveys, which were performed simultaneously in field campaigns during hot and cold seasons. The aim was to propose design guidelines for open areas according to local thermal preferences. An updated regionally-calibrated Physiological Equivalent Temperature (PET) assessment scale is also proposed. Neutral temperatures were estimated on a seasonal basis and critical discomfort hours on a monthly basis. The results reaffirm that psychological and behavioral factors influence the individuals’ assessment of the outdoor thermal environment and therefore should be considered as design criteria. To improve the microclimate of urban open areas in Campo Grande, shading must be provided primarily by trees and resting areas should be protected from wind exposure. The use of water features for evaporative cooling purposes is not recommended, however, drinking fountains should be available in public squares. Such results can be used by landscape architects and urban planners to deliver thermally comfortable open spaces, encouraging greater use and increased length of stay in these areas.

Quantitative biomonitoring of nitrogen deposition with TONIS (Total N Input Biomonitoring System)

Monitoring of air pollutants is an important instrument to detect threats and to observe temporal trends of emissions. Determining the spatial distribution of oxidized and reduced N species via modelling requires sufficient knowledge about innumerous small sources from traffic, settlements and agriculture. Empirical studies are required to validate the model data but measurements of the total N deposition (e.g. micrometeorological measurements) are very expensive.Against this background, the TONIS, a new suitable technique which combines a biomonitoring with plants and technical measurements was developed. During 6 exposures between 2012 and 2016 at different polluted sites in Northwest Germany, TONIS accumulated between 17 and 25 kg N ha-1 yr−1t. The results are feasible compared to simultaneously measured NH3 and NO2 concentration and bulk N deposition. At one site within a peat bog the accumulated N in TONIS was found to be in the range of total N deposition derived from a micrometeorological approach.

A Simple Representation of Plant Water Storage Effects in Coupled Soil Water Flow and Transpiration Stream Modeling

Core Ideas A previous soil water flow model was extended to allow simulation of transient plant water storage. Comparison with measured Norway spruce sap flow data indicates improved model performance. The proposed algorithm can be easily incorporated into existing soil water flow models. When describing the movement of water in a variably saturated plant root zone, most existing hydrological models use the assumption of quasi‐steady‐state flow to relate root water uptake to canopy transpiration, thereby neglecting the effect of changing plant water storage. This approach is known to be problematic, especially when considering relatively large volumes of water stored in the tissues of tall trees. We propose a simple algorithm, based on the concept of whole‐plant hydraulic capacitance, to deal with the problem. The algorithm is implemented in a one‐dimensional soil water flow model involving vertically distributed macroscopic root water uptake. In this study, the proposed transient storage approach was compared with the quasi‐steady‐state approach. Both approaches were used to simulate soil water flow and diurnal variations of transpiration at a forest site covered with Norway spruce [Picea abies (L.) H. Karst.]. The key parameter of the transient storage approach, the plant hydraulic capacitance, is estimated by comparing the variations in the potential transpiration rate, derived from micrometeorological measurements, with observed sap flow intensities. The application of the proposed algorithm leads to more realistic predictions of root water uptake rates at the site of interest. The inclusion of the plant water storage effects improved the ability of the model to capture the anticipated diurnal variations in actual transpiration rates. The algorithm can be easily implemented into existing soil water flow models and used to simulate transpiration stream responses to varying atmospheric and soil moisture conditions including isohydric and partly also anisohydric plant responses to drought stress.

Modelling sun-induced fluorescence and photosynthesis with a land surface model at local and regional scales in northern Europe

Abstract. Recent satellite observations of sun-induced chlorophyll fluorescence (SIF) are thought to provide a large-scale proxy for gross primary production (GPP), thus providing a new way to assess the performance of land surface models (LSMs). In this study, we assessed how well SIF is able to predict GPP in the Fenno-Scandinavian region and what potential limitations for its application exist. We implemented a SIF model into the JSBACH LSM and used active leaf-level chlorophyll fluorescence measurements (Chl F) to evaluate the performance of the SIF module at a coniferous forest at Hyytiälä, Finland. We also compared simulated GPP and SIF at four Finnish micrometeorological flux measurement sites to observed GPP as well as to satellite-observed SIF. Finally, we conducted a regional model simulation for the Fenno-Scandinavian region with JSBACH and compared the results to SIF retrievals from the GOME-2 (Global Ozone Monitoring Experiment-2) space-borne spectrometer and to observation-based regional GPP estimates. Both observations and simulations revealed that SIF can be used to estimate GPP at both site and regional scales. At regional scale the model was able to simulate observed SIF averaged over 5 years with r2 of 0.86. The GOME-2-based SIF was a better proxy for GPP than the remotely sensed fAPAR (fraction of absorbed photosynthetic active radiation by vegetation). The observed SIF captured the seasonality of the photosynthesis at site scale and showed feasibility for use in improving of model seasonality at site and regional scale.

Flux-variance and flux-gradient relationships in the roughness sublayer over the Amazon forest

The failure of the Monin–Obukhov Similarity Theory (MOST) in the roughness sublayer is a major problem for the estimation of fluxes over tall forests, whenever indirect methods that rely on MOST, such as flux-gradient or the variance method, are involved. While much research focuses on micrometeorological measurements over temperate-climate forests, very few studies deal with such measurements over tropical forests. In this paper, we show evidence that some similarity functions over the Amazon forest are somewhat different from temperate forests. Comparison of the nondimensional scalar gradients canonical values for the inertial sublayer with our measurements in the roughness sublayer showed smaller deviations than what is usually reported for temperate forests. Although the fluxes of water vapor and CO2 derived from mean profiles show considerable scatter when compared with the eddy covariance measurements, using calibrated dimensionless gradients it is possible to estimate their mean daily cycle during the period of measurement (36 days in May and June, transition between rainy and dry season). Moreover, since mean ozone profiles were available, although without the corresponding eddy covariance measurements, mean daily ozone fluxes were calculated with the flux-gradient method, yielding a nighttime value of −0.05 and a daily peak of −0.45μgm−2s−1 (−1.04 and −9.37nmolm−2s−1, respectively). These values are comparable to previously measured fluxes in the literature for the Amazon forest.

Outdoor thermal comfort in public space in warm-humid Guayaquil, Ecuador

The thermal environment outdoors affects human comfort and health. Mental and physical performance is reduced at high levels of air temperature being a problem especially in tropical climates. This paper deals with human comfort in the warm-humid city of Guayaquil, Ecuador. The main aim was to examine the influence of urban micrometeorological conditions on people’s subjective thermal perception and to compare it with two thermal comfort indices: the physiologically equivalent temperature (PET) and the standard effective temperature (SET*). The outdoor thermal comfort was assessed through micrometeorological measurements of air temperature, humidity, mean radiant temperature and wind speed together with a questionnaire survey consisting of 544 interviews conducted in five public places of the city during both the dry and rainy seasons. The neutral and preferred values as well as the upper comfort limits of PET and SET* were determined. For both indices, the neutral values and upper thermal comfort limits were lower during the rainy season, whereas the preferred values were higher during the rainy season. Regardless of season, the neutral values of PET and SET* are above the theoretical neutral value of each index. The results show that local people accept thermal conditions which are above acceptable comfort limits in temperate climates and that the subjective thermal perception varies within a wide range. It is clear, however, that the majority of the people in Guayaquil experience the outdoor thermal environment during daytime as too warm, and therefore, it is important to promote an urban design which creates shade and ventilation.

Stable Isotopes Reveal Rapid Cycling of Soil Nitrogen after Manure Application.

Understanding the fate of applied nitrogen (N) in agricultural soils is important for agronomic, environmental, and human health reasons, but it is methodologically difficult to study at the field scale. Natural abundance stable isotope measurements (δN) were used in this field study with micrometeorological measurements of nitrous oxide (NO) emissions to identify the biogeochemical processes responsible for rapid N transformations immediately after application of liquid dairy manure. Fifteen samplings occurred between 16 Mar. 2012 and 5 Apr. 2013, with a focus on spring manure application (before and after) and a winter snowmelt period. Concentrations and δN values of ammonium (NH), nitrate (NO), NO, and total N were measured throughout the year. Approximately 56 (±7)% of the NH-N applied in the spring could not be accounted for 3 d after manure application and was presumably lost by ammonia volatilization before it was tilled into the soil and/or removed from the inorganic N pool by microbial assimilation. Almost all of the remaining manure-NH (95 ± 1.1%) was converted within 3 wk to NO and NO by nitrification and nitrifier-denitrification, respectively. The in situ N isotope effect for nitrification (ε) was calculated to be -32.0 (±5.3)‰. Overall, field-scale measurements of δN at natural abundance provided valuable information that was used to distinguish sources of NH (manure vs. soil organic N) and to follow the production and consumption of NO and the pathways of NO production in soil.

Temporal Downscaling of Crop Coefficients for Winter Wheat in the North China Plain: A Case Study at the Gucheng Agro-Meteorological Experimental Station

The crop coefficient (Kc) is widely used for operational estimation of actual evapotranspiration (ETa) and crop water requirements. The standard method for obtaining Kc is via a lookup table from FAO-56 (Food and Agriculture Organization of the United Nations Irrigation and Drainage Paper No. 56), which broadly treats Kc as a function of four crop-growing stages. However, the distinctive physiological characteristics of overwintering crops, such as winter wheat (Triticum aestivum L.), which is extensively planted in the North China Plain (NCP), are not addressed in this method. In this study, we propose a stage-wise method that accounts for Kc variations for winter wheat at each critical phenological stage, thereby estimating Kc at finer temporal scales. Compared with the conventional FAO method, the proposed stage-wise method successfully captures the bimodal pattern in Kc time series for winter wheat, which is shown at both ten-day and phenological time scales. In addition, the accuracies of the proposed stage-wise Kc method and the FAO method were evaluated using micro-meteorological measurements of ETa collected at the Gucheng agrometeorological experimental station in the NCP. Using a leave-one-out strategy, the evaluation revealed that the stage-wise method significantly outperformed the FAO method at both daily and critical phenological time scales, with root-mean-square errors in ETa for the stage-wise method and the FAO method being 0.07 mm·day-1 and 0.16 mm·day-1, respectively, at the daily time scale, and 0.01 mm·day-1 and 0.27 mm·day-1 at the critical phenological time scale. Generally, the FAO method underestimates ETa during the initial stage and overestimates ETa during both the development and mid-season stages. It is shown that the proposed stage-wise method is important for the water-stressed NCP where precision irrigation is highly desirable, especially during the critical phenological stages. Results from this study provide insight into accurate estimation of water requirements for winter wheat at phenological time scales.

The urban heat island effect in Dutch city centres

In the Netherlands awareness regarding the Urban Heat Island (UHI) was raised relatively recently. Because of this recent understanding, there is a lack of consistent urban micro-meteorological measurements to allow a conventional UHI assessment of Dutch cities during heat waves. This paper argues that it is possible to retrieve relevant UHI information – including adaptation guidelines – from satellite imagery. The paper comprises three parts. The first part consists of a study of suited indicators to identify urban heat islands from which a method is presented based on ground heat flux mapping. The second part proposes heat mitigation strategies and identifies the areas where these strategies could be applied within the hotspots identified in the cities of The Hague, Delft, Leiden, Gouda, Utrecht and Den Bosch. The third part estimates the reduction of urban heat generated by the increase of roof albedo in the hotspots of the six cities. The six cities hotspots are located within the boundaries of the 17th century city centres. In order to avoid interference with cultural values of these historical environments most likely UHI mitigation measures regard improving the thermal behaviour of the city roofs. For instance, applying white coatings on bitumen flat roofs (or replacing them by white single-ply membranes) and replacing sloped roof clay tiles by coloured tiles with cool pigments can reduce the urban heat hotspots by approximately 1.5°C. Remote sensing provides high level information that provide urban planners and policy makers with overall design guidelines for the reduction of urban heat.

Dry deposition of particles to canopies—A look back and the road forward

AbstractThe so‐called accumulation‐size range of airborne particles is the center of a continuing disagreement about the formulation of dry deposition. Some contemporary meteorological and air quality models use theoretical developments based on early wind tunnel and other controlled experiments, while other models consider the bulk properties of the underlying surface and the ability of atmospheric turbulence to deliver particles to it. This dichotomy arose when the first micrometeorological measurements of particle deposition velocities became available, yielding numbers exceeding the highest expectations of the then‐current models based on assumptions about inertial impaction and interception. The model predictions had previously been shown to be in accord with theoretical treatments of filtration. A common reaction was to distrust the field experimental results, but the experimental findings were supported by subsequent studies. The difference between model predictions and field measurements appears greatest for densely vegetated canopies. Ongoing research is investigating factors that could give rise to the discrepancy, e.g., turbulence intermittency, leaf orientation, leaf morphology, leaf flutter, electrical charges, and a number of phoretic effects. In the meantime, many investigators are faced with a decision as to whether to make use of parameterized field results or theoretical descriptions of behaviors that are not yet well examined. Here the history of the ongoing disagreement is reviewed, and some possible resolutions are presented.

Analyzing the Cooling Effect of Urban Green Areas by Using the Multiple Observation Network in the Seonjeongneung Region of Seoul, Korea

To analyze the cooling effect of urban green areas, we conducted micrometeorological measurements in these areas and their surroundings in Seoul, Korea. From the average hourly temperature measurements through each month for the last two years (March 2013 to February 2015), we found that the maximum...

Verification of micrometeorologically determined nitrous oxide fluxes following controlled release from pasture

We have developed a high-precision micrometeorological system capable of measuring emissions of nitrous oxide (N2O) from up to four adjacent pasture plots. The system can be used to compare the influence of environmental factors and management practice on N2O emissions at the paddock scale. The system is capable of determining a minimum detectable N2O difference of the order of 40 pmol/mol, with an ability to resolve flux differences among plots of ~26 µg (N2O-N)/m2.h. So as to independently verify the emission estimates of the micrometeorological system, we developed a calibrated N2O-release system and compared known release rates with the micrometeorological flux estimates. Adjustable release rates up to the equivalent average surface flux of ~500 µg (N2O-N)/m2.h were achieved using mass flow-controlled input of pure N2O in a compressed air stream over two 1.5-ha plots upwind of flux-measurement masts. The comparison of network release rate with measured emission rate was quite variable and complicated by a significant and varying background emissions of N2O from the soil. For optimal steady-wind cases, the ratio of uncorrected measured flux to known release, including the estimated background, was of the order of 0.4–0.5; this ratio is likely to be influenced by the turbulent Schmidt number. Flux estimates for uncorrected flux gradient and WindTrax backward Lagrangian Stochastic method (which includes Schmidt correction) agreed well with a ratio of 0.54. The experiment highlighted the need for accurate estimates of gas eddy diffusivity in the micrometeorological gradient or difference-based flux measurement of N2O.

Linear Parks along Urban Rivers: Perceptions of Thermal Comfort and Climate Change Adaptation in Cyprus

The development of green space along urban rivers could mitigate urban heat island effects, enhance the physical and mental well-being of city dwellers, and improve flood resilience. A linear park has been recently created along the ephemeral Pedieos River in the urban area of Nicosia, Cyprus. Questionnaire surveys and micrometeorological measurements were conducted to explore people’s perceptions and satisfaction regarding the services of the urban park. People’s main reasons to visit the park were physical activity and exercise (67%), nature (13%), and cooling (4%). The micrometeorological measurements in and near the park revealed a relatively low cooling effect (0.5 °C) of the park. However, the majority of the visitors (84%) were satisfied or very satisfied with the cooling effect of the park. Logistic regression analysis indicated that the odds of individuals feeling very comfortable under a projected 3 °C future increase in temperature would be 0.34 times lower than the odds of feeling less comfortable. The discrepancies between the observed thermal comfort index and people’s perceptions revealed that people in semi-arid environments are adapted to the hot climatic conditions; 63% of the park visitors did not feel uncomfortable at temperatures between 27 °C and 37 °C. Further research is needed to assess other key ecosystems services of this urban green river corridor, such as flood protection, air quality regulation, and biodiversity conservation, to contribute to integrated climate change adaptation planning.

Towards a Climate-Responsive Vertical Pedestrian System: An Empirical Study on an Elevated Walkway in Shanghai China

Elevated walkways can bring pedestrian-friendly urban space back to high-density urban centers that are planned largely for vehicle traffic—for instance, the Lujiazui CBD in Shanghai. Most studies on elevated walkways have focused on transportation planning, structural safety as well as urban form and design. Few have paid attention to thermal conditions and pedestrian comfort issues on elevated levels. Considering all of the environmental factors that influence human thermal comfort, one could claim that there will be more breezes on elevated levels compared to sidewalks at the ground levels, but they can be exposed to increased solar radiation and thus higher radiant temperatures, if not properly shaded. The overall effect of the change in elevation on human thermal comfort is thus unknown. This study attempts to investigate the microclimate and human thermal comfort of a recently completed Lujiazui Elevated Walkway (LEW) system in the Lujiazui CBD, Shanghai, under a hot-humid sub-tropical climate. Micrometeorological measurements and a guided questionnaire survey were carried out on peak summer days. The data analysis indicates that the LEW is thermally more uncomfortable than its ground level counterpart. Air temperature was higher, whereas wind velocity is lower on the skywalk level than on the ground level, which is counter-intuitive. The resultant physiological equivalent temperature (PET) indicates warm conditions on the ground level (with good shading) while there are hot conditions on the skywalk. Based on the empirical findings, design strategies are proposed to improve the thermal comfort conditions on the LEW, and to better support pedestrian activities in this typical high-rise high-density urban area.

Analysis and simulation of the water and energy balance of intense agriculture in the Upper Rhine valley, south-west Germany

The Upper Rhine valley (SW Germany) belongs to one of the agriculturally most intense used regions in Germany. Climatic favourable conditions with mild winters, early springs and warm autumns lead to long vegetation periods and high agricultural productivity. One limiting factor is the water supply because of a negative annual climatic water balance, which has been increasing by −10 mm per decade in the last 50 years to −150 mm at present. Thus irrigation measures become more and more important for agricultural production in this region. Aim of this study was to measure and simulate water and energy fluxes on farm level in respect to the effects of irrigation measures in a region where farm sizes are small and diversity of land use high. In future these results will be used to conduct studies of energy and water fluxes on spatial scale (e.g. water catchments). The dynamics of the water and energy balance was observed with micrometeorological measurements using the eddy covariance methodology. Our investigation area had a size of about 6.5 ha and was cultivated with spring barley (Hordeum vulgare L.). Continuous measurements of all components of the water and energy balance as well as the vegetation specific-parameters, such as LAI, crop height and phenological macrostages, were conducted during the growing season which lasted from the beginning of April to 16 July 2014 (95 days). Additional irrigation was applied three times in this period by using a mobile sprinkler irrigation system. The observed dynamics were simulated with the physically based hydrological model TRAIN, which uses the Penman–Monteith approach for evapotranspiration simulation. Model efficiency was evaluated with Nash–Sutcliffe coefficient (NS). The TRAIN model was performing the simulations well with an r 2 = 0.72 with an slope of 1 and a NS = 0.77.