scholarly journals Actual evapotranspiration and precipitation measured by lysimeters: a comparison with eddy covariance and tipping bucket

2014 ◽  
Vol 11 (12) ◽  
pp. 13797-13841 ◽  
Author(s):  
S. Gebler ◽  
H.-J. Hendricks Franssen ◽  
T. Pütz ◽  
H. Post ◽  
M. Schmidt ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Precipitation Amount ◽  
Test Site ◽  
Rain Gauge ◽  
Actual Evapotranspiration ◽  
Monthly Basis ◽  
Snow Drift ◽  
Precipitation Difference ◽  
Total Difference ◽  
The Individual

Abstract. This study compares actual evapotranspiration (ETa) measurements by a set of six weighable lysimeters, ETa estimates obtained with the eddy covariance (EC) method, and potential crop evapotranspiration according to FAO (ETc-FAO) for the Rollesbroich site in the Eifel (Western Germany). The comparison of ETa measured by EC (including correction of the energy balance deficit) and by lysimeters is rarely reported in literature and allows more insight into the performance of both methods. An evaluation of ETa for the two methods for the year 2012 shows a good agreement with a total difference of 3.8% (19 mm) between the ETa estimates. The highest agreement and smallest relative differences (<8%) on monthly basis between both methods are found in summer. ETa was close to ETc-FAO, indicating that ET was energy limited and not limited by water availability. ETa differences between lysimeter, ETc-FAO, and EC were mainly related to differences in grass height caused by harvesting management and the EC footprint. The lysimeter data were also used to estimate precipitation amounts in combination with a filter algorithm for high precision lysimeters recently introduced by Peters et al. (2014). The estimated precipitation amounts from the lysimeter data show significant differences compared to the precipitation amounts recorded with a standard rain gauge at the Rollesbroich test site. For the complete year 2012 the lysimeter records show a 16% higher precipitation amount than the tipping bucket. With the help of an on-site camera the precipitation measurements of the lysimeters were analyzed in more detail. It was found that the lysimeters record more precipitation than the tipping bucket in part related to the detection of rime and dew, which contributes 17% to the yearly difference between both methods. In addition, fog and drizzle explain an additional 5.5% of the total difference. Larger differences are also recorded for snow and sleet situations. During snowfall, the tipping bucket device underestimated precipitation severely and these situations contributed also 7.9% to the total difference. However, 36% of the total yearly difference was associated to snow cover without apparent snowfall and under these conditions snow bridges and snow drift seem to explain the strong underestimation of precipitation by the lysimeter. The remaining precipitation difference (about 33%) could not be explained, and did not show a clear relation with wind speed. The variations of the individual lysimeters devices compared to the lysimeter mean of 2012 are small showing variations up to 3% for precipitation and 8% for evapotranspiration.

scholarly journals Actual evapotranspiration and precipitation measured by lysimeters: a comparison with eddy covariance and tipping bucket

2015 ◽  
Vol 19 (5) ◽  
pp. 2145-2161 ◽  
Author(s):  
S. Gebler ◽  
H.-J. Hendricks Franssen ◽  
T. Pütz ◽  
H. Post ◽  
M. Schmidt ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Precipitation Amount ◽  
Test Site ◽  
Rain Gauge ◽  
Actual Evapotranspiration ◽  
Monthly Basis ◽  
Snow Drift ◽  
Precipitation Difference ◽  
Total Difference ◽  
The Individual

Abstract. This study compares actual evapotranspiration (ETa) measurements by a set of six weighable lysimeters, ETa estimates obtained with the eddy covariance (EC) method, and evapotranspiration calculated with the full-form Penman–Monteith equation (ETPM) for the Rollesbroich site in the Eifel (western Germany). The comparison of ETa measured by EC (including correction of the energy balance deficit) and by lysimeters is rarely reported in the literature and allows more insight into the performance of both methods. An evaluation of ETa for the two methods for the year 2012 shows a good agreement with a total difference of 3.8% (19 mm) between the ETa estimates. The highest agreement and smallest relative differences (< 8%) on a monthly basis between both methods are found in summer. ETa was close to ETPM, indicating that ET was energy limited and not limited by water availability. ETa differences between lysimeter and EC were mainly related to differences in grass height caused by harvest and the EC footprint. The lysimeter data were also used to estimate precipitation amounts in combination with a filter algorithm for the high-precision lysimeters recently introduced by Peters et al. (2014). The estimated precipitation amounts from the lysimeter data differ significantly from precipitation amounts recorded with a standard rain gauge at the Rollesbroich test site. For the complete year 2012 the lysimeter records show a 16 % higher precipitation amount than the tipping bucket. After a correction of the tipping bucket measurements by the method of Richter (1995) this amount was reduced to 3%. With the help of an on-site camera the precipitation measurements of the lysimeters were analyzed in more detail. It was found that the lysimeters record more precipitation than the tipping bucket, in part related to the detection of rime and dew, which contribute 17% to the yearly difference between both methods. In addition, fog and drizzle explain an additional 5.5% of the total difference. Larger differences are also recorded for snow and sleet situations. During snowfall, the tipping bucket device underestimated precipitation severely, and these situations contributed also 7.9% to the total difference. However, 36% of the total yearly difference was associated with snow cover without apparent snowfall, and under these conditions snow bridges and snow drift seem to explain the strong overestimation of precipitation by the lysimeter. The remaining precipitation difference (about 33%) could not be explained and did not show a clear relation to wind speed. The variation of the individual lysimeters devices compared to the lysimeter mean are small, showing variations up to 3% for precipitation and 8% for evapotranspiration.

Peakedness of Wave Systems Observed on the French Wave Energy Test Site (SEM-REV) Using a Spectral Partitioning Algorithm

2013 ◽  
Author(s):  
Jean-Baptiste Saulnier ◽  
Izan Le Crom
Keyword(s):  
Wave Energy ◽  
Test Site ◽  
Extreme Conditions ◽  
Multiple Wave ◽  
Wave Energy Converters ◽  
Marine Energy ◽  
Partitioning Algorithm ◽  
Spectral Partitioning ◽  
The Individual ◽  
Energy Converters

Located off the Guérande peninsula, SEM-REV is the French maritime facility dedicated to the testing of wave energy converters and related components. Lead by Ecole Centrale de Nantes through the LHEEA laboratory, its aim is to promote research alongside the development of new offshore technologies. To this end, the 1km2, grid-connected zone is equipped with a comprehensive instruments network sensing met-ocean processes and especially waves, with two identical directional Waverider buoys deployed on the site since 2009. For the design of moored floating structures and, a fortiori, floating marine energy converters, the knowledge of the main wave resource — for regular operation — but also extreme conditions — for moorings and device survivability — has to be as precise as possible. Also, the consideration of the multiple wave systems (swell, wind sea) making up the sea state is a key asset for the support of developers before and during the testing phase. To this end, a spectral partitioning algorithm has been implemented which enables the individual characterisation of wave systems, in particular that of their spectral peakedness which is especially addressed in this work. Peakedness has been shown to be strongly related to the groupiness of large waves and is defined here as the standard JONSWAP’s peak enhancement factor γ. Statistics related to this quantity are derived from the measurement network, with a particular focus on the extreme conditions reported on SEM-REV (Joachim storm).

scholarly journals Optimization of Rain Gauge Networks for Arid Regions Based on Remote Sensing Data

2021 ◽  
Vol 13 (21) ◽  
pp. 4243
Author(s):  
Mona Morsy ◽  
Ruhollah Taghizadeh-Mehrjardi ◽  
Silas Michaelides ◽  
Thomas Scholten ◽  
Peter Dietrich ◽  
...  
Keyword(s):  
Arid Regions ◽  
Flash Flood ◽  
Primary Source ◽  
Remote Sensing Data ◽  
Test Site ◽  
Rain Gauge ◽  
Cumulative Distribution ◽  
Climatic Data ◽  
Empirical Cumulative Distribution Function ◽  
Rain Gauges

Water depletion is a growing problem in the world’s arid and semi-arid areas, where groundwater is the primary source of fresh water. Accurate climatic data must be obtained to protect municipal water budgets. Unfortunately, the majority of these arid regions have a sparsely distributed number of rain gauges, which reduces the reliability of the spatio-temporal fields generated. The current research proposes a series of measures to address the problem of data scarcity, in particular regarding in-situ measurements of precipitation. Once the issue of improving the network of ground precipitation measurements is settled, this may pave the way for much-needed hydrological research on topics such as the spatiotemporal distribution of precipitation, flash flood prevention, and soil erosion reduction. In this study, a k-means cluster analysis is used to determine new locations for the rain gauge network at the Eastern side of the Gulf of Suez in Sinai. The clustering procedure adopted is based on integrating a digital elevation model obtained from The Shuttle Radar Topography Mission (SRTM 90 × 90 m) and Integrated Multi-Satellite Retrievals for GPM (IMERG) for four rainy events. This procedure enabled the determination of the potential centroids for three different cluster sizes (3, 6, and 9). Subsequently, each number was tested using the Empirical Cumulative Distribution Function (ECDF) in an effort to determine the optimal one. However, all the tested centroids exhibited gaps in covering the whole range of elevations and precipitation of the test site. The nine centroids with the five existing rain gauges were used as a basis to calculate the error kriging. This procedure enabled decreasing the error by increasing the number of the proposed gauges. The resulting points were tested again by ECDF and this confirmed the optimum of thirty-one suggested additional gauges in covering the whole range of elevations and precipitation records at the study site.

Advanced distributed modelling of slope stability using root reinforcement and geostatistical parameterization of geotechnical soil properties

2020 ◽  
Author(s):  
Elena Benedetta Masi ◽  
Anita Stagnozzi ◽  
Silvia Stagnozzi ◽  
Gianluigi Tonelli ◽  
Francesco Veneri ◽  
...  
Keyword(s):  
Slope Stability ◽  
Central Italy ◽  
Image Interpretation ◽  
Test Site ◽  
Rain Gauge ◽  
Rainfall Event ◽  
Unit Weight ◽  
Future Research ◽  
Time Step ◽  
Soil Thickness

&lt;p&gt;A physically based model for shallow landslide triggering (HIRESSS &amp;#8211; HIgh REsolution Soil Stability Simulator) was applied in a 100 km&lt;sup&gt;2&lt;/sup&gt; test site in Central Italy (Urbino, Marche region). The objectives were assessing &amp;#160;the influence of additional cohesion provided by roots and testing the effectiveness of a geotechnical characterization performed in an another area, but on similar lithologies.&lt;/p&gt;&lt;p&gt;We performed two different simulations considering the rainfall event of January-February 2006, which triggered 14 landslides in the area. For both the simulations, rainfall data were fed into the model using the measurements at hourly time step of a nearby rain gauge station, while soil thickness was estimated using a state-of-the-art empirical model based on geomorphological parameters derived from curvature, slope gradient, lithology and relative position within the hillslope profile. Geotechnical input data were varied among the two simulations. In the first one, a few in-situ and laboratory tests were performed to characterize the main lithologies, while the remaining lithologies were characterized using literature data. In the second simulation, the main geotechnical and hydrological parameters (cohesion, internal friction angle, soil unit weight, hydraulic conductivity) were fed into the model using a geostatistical characterization performed on hundreds of measurements carried out in another Italian region, with similar lithologies. Furthermore, in the second simulation the additional cohesion provided by the plant roots was also taken into account.&lt;/p&gt;&lt;p&gt;The results obtained with the two simulations were validated considering the landslide dataset collected by field work and image interpretation shortly after the rainfall event studied. We discovered that the second simulation provided much more reliable results, with the areas surrounding the landslide locations characterized by much higher values of failure probability.&lt;/p&gt;&lt;p&gt;The outcome is very important to address future research in distributed slope stability modelling because it proved that: (i) additional root cohesion is an important factor that can be used to get more reliable results; (ii) when in need of characterizing the geotechnical parameters of the study area, instead of using just a few measurements performed therein, it is preferable to integrate also data coming from different areas but with similar lithologies if they were robustly characterized in geostatistical terms purposely for distributed slope stability studies.&lt;/p&gt;

scholarly journals Observing Actual Evapotranspiration from Flux Tower Eddy Covariance Measurements within a Hilly Watershed: Case Study of the Kamech Site, Cap Bon Peninsula, Tunisia

Atmosphere ◽  
2018 ◽  
Vol 9 (2) ◽  
pp. 68 ◽  
Author(s):  
Rim Zitouna-Chebbi ◽  
Laurent Prévot ◽  
Amal Chakhar ◽  
Manel Marniche-Ben Abdallah ◽  
Frederic Jacob
Keyword(s):  
Eddy Covariance ◽  
Actual Evapotranspiration ◽  
Flux Tower ◽  
Eddy Covariance Measurements ◽  
Hilly Watershed

scholarly journals Mixing ratios and eddy covariance flux measurements of volatile organic compounds from an urban canopy (Manchester, UK)

2008 ◽  
Vol 8 (1) ◽  
pp. 245-284 ◽  
Author(s):  
B. Langford ◽  
B. Davison ◽  
E. Nemitz ◽  
C. N. Hewitt
Keyword(s):  
Volatile Organic Compounds ◽  
Eddy Covariance ◽  
Organic Compounds ◽  
Urban Canopy ◽  
Proton Transfer Reaction ◽  
Anthropogenic Sources ◽  
Emissions Inventory ◽  
Mixing Ratios ◽  
Volatile Organic ◽  
The Individual

Abstract. Concentrations and fluxes of six volatile organic compounds (VOC) were measured above the city of Manchester (UK) during the summer of 2006. A proton transfer reaction-mass spectrometer was used for the measurement of concentrations, and fluxes were calculated using both the disjunct and the virtual disjunct eddy covariance techniques. The two flux systems, which operated in alternate half hours, showed reasonable agreement, with R2 values ranging between 0.2 and 0.8 for the individual analytes. On average, fluxes measured in the disjunct mode were lower than those measured in the virtual mode by approximately 19%, of which at least 8% can be attributed to the differing measurement frequencies of the two systems and the subsequent attenuation of high frequency flux contributions. Observed fluxes are thought to be largely controlled by anthropogenic sources, with vehicle emissions the major contributor. However both evaporative and biogenic emissions may account for a fraction of the isoprene present. Fluxes of the oxygenated compounds were highest on average, ranging between 60–89 μg m−2 h−1, whereas the fluxes of aromatic compounds were lower, between 19–42 μg m−2 h−1. The observed fluxes of benzene were up-scaled to give a city wide emission estimate which was found to be significantly lower than that of the National Atmospheric Emissions Inventory (NAEI).

scholarly journals Physicochemical and microbiological characteristics of goat milk from animals grown in a mountainous area in Bulgaria

2020 ◽  
Vol 12 (3) ◽  
pp. 277-281
Author(s):  
D. Pamukova ◽  
N. Rusenova ◽  
T. Kolev ◽  
S. Chobanova ◽  
N. Naydenova
Keyword(s):  
Milk Fat ◽  
Bacterial Species ◽  
Goat Milk ◽  
Dairy Goat ◽  
Mountainous Area ◽  
Coagulase Negative Staphylococci ◽  
Monthly Basis ◽  
Milk Samples ◽  
Microbiological Characteristics ◽  
The Individual

Abstract. The aim of the study was to determine the goat milk quality from animals grown in a mountainous area in Bulgaria based on physicochemical and microbiological parameters. The study was carried out in a farm that breeds local goats and goats of the Bulgarian White Dairy Goat (BWD). Individual milk samples were taken on a monthly basis from morning milking. A total of 100 individual and 10 bulk milk samples were examined for fat, solids non fat, protein and density. A total of 62 samples were collected at a time to determine the microbiological characteristics of milk. For the period May-September 2017, the percentage of fat in the milk of local goats averaged 3.61% and of goats from BWD goat – 3.54%. The solids non fat were 8.27% and 8.19%, total protein – 3.13% and 3.10%, and the dry matter – 11.89% and 11.74%, respectively. For the period May-August 2017 the individual constituents of milk changed to varying degrees with the most variable being milk fat (decrease of 0.97% in local goats’ milk and 1.09% in milk from BWD goat) followed by solids non fat (0.56% and 0.7%, respectively). The slightest change was in protein – 0.21% and 0.26%, respectively. Coagulase-negative staphylococci were the predominant bacterial species in the goats’ milk samples.

scholarly journals Evaluation of INCA precipitation analysis using a very dense rain gauge network in southeast Austria

2021 ◽  
Author(s):  
Esmail Ghaemi ◽  
Ulrich Foelsche ◽  
Alexander Kann ◽  
Jürgen Fuchsberger
Keyword(s):  
Precipitation Amount ◽  
Rain Gauge ◽  
Accurate Estimate ◽  
Time Shift ◽  
Grid Cells ◽  
Wet Season ◽  
Event Time ◽  
Peak Intensity ◽  
Precipitation Analysis ◽  
Rain Gauge Network

Abstract. An accurate estimate of precipitation is essential to improve the reliability of hydrological models and helps for decision-making in agriculture and economy. Merged radar–rain-gauge products provide precipitation estimates at high spatial and temporal resolution. In this study, we assess the ability of the INCA (Integrated Nowcasting through Comprehensive Analysis) precipitation analysis product provided by ZAMG (the Austrian Central Institute for Meteorology and Geodynamics) in detecting and estimating precipitation for 12 years in southeast Austria. The blended radar–rain-gauge INCA precipitation analyses are evaluated using WegenerNet – a very dense rain gauge network with about 1 station per 2 km2 – as true precipitation. We analyze annual, seasonal, and extreme precipitation of the 1 km × 1 km INCA product and its development from 2007 to 2018. Based on the results, the performance of INCA can be divided into three different periods. From 2007 to 2011, the annual area-mean precipitation in INCA was slightly higher than WegenerNet, except in 2009. However, INCA underestimates precipitation in grid cells farther away from the two ZAMG meteorological stations in the study area (which are used as input for INCA), especially from May to September (wet season). From 2012 to 2014, INCA's overestimation of the annual-mean precipitation amount is even higher, with an average of 25 %, but INCA performs better close to the two ZAMG stations. From 2015 onwards, the overestimation is still dominant in most cells but less pronounced than during the second period, with an average of 12.5 %. Regarding precipitation detection, INCA performs better during the wet seasons. Generally, false events in INCA happen less frequently in the cells closer to the ZAMG stations than in other cells. The number of true events, however, is comparably low closer to the ZAMG stations. The difference between INCA and WegenerNet estimates is more noticeable for extremes. We separate individual events using a 1-hour minimum inter-event time (MIT) and demonstrate that INCA underestimates the events' peak intensity until 2012 and overestimates this value after mid-2012 in most cases. The overestimation of the peak-intensity is more pronounced during July. In general, the precipitation rate and the number of grid cells with precipitation are higher in INCA. Furthermore, 40 % of the individual events start earlier, and 50 % end later in INCA. Considering four extreme convective short-duration events, there is a time shift in peak intensity detection. The relative differences in the peak intensity in these events can change from approximately −40 % to 40 %. The results of this study can be used for further improvements of INCA products as well as for future hydrological studies in this area.

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