scholarly journals A measurement campaign to assess sources of error in microwave link rainfall estimation

2018 ◽  
Vol 11 (8) ◽  
pp. 4645-4669 ◽  
Author(s):  
Thomas C. van Leth ◽  
Aart Overeem ◽  
Hidde Leijnse ◽  
Remko Uijlenhoet
Keyword(s):  
Communication Networks ◽  
Global Analysis ◽  
Time Lapse ◽  
Rain Gauge ◽  
Operating Conditions ◽  
Retrieval Algorithm ◽  
Measurement Campaign ◽  
Temporal Sampling ◽  
Microwave Link ◽  
Rainfall Retrieval

Abstract. We present a measurement campaign to address several error sources associated with rainfall estimates from microwave links in cellular communication networks. The core of the experiment is provided by three co-located microwave links installed between two major buildings on opposite sides of the small town of Wageningen, approximately 2 km apart: a 38 GHz formerly commercial microwave link, as well as 26 and 38 GHz (dual-polarization) research microwave links. Transmitting and receiving antennas have been attached to masts installed on the roofs of the two buildings, about 30 m above the ground. This setup was complemented with an infrared large-aperture scintillometer, installed over the same path, as well as five laser disdrometers positioned at several locations along the path and an automated rain gauge. Temporal sampling of the received signals was performed at a rate of 20 Hz. The setup was monitored by time-lapse cameras to assess the state of the antennas as well as the atmosphere. The experiment was active between August 2014 and December 2015. Data from an existing automated weather station situated just outside Wageningen was further used to compare and to interpret the findings. In addition to presenting the experiment, we also conduct a preliminary global analysis and show several cases highlighting the different phenomena affecting received signal levels: rainfall, solid precipitation, temperature, fog, antenna wetting due to rain or dew, and clutter. We also briefly explore cases where several phenomena play a role. A rainfall intensity (R) – specific attenuation (k) relationship was derived from the disdrometer data. We find that a basic rainfall retrieval algorithm without corrections already provides a reasonable correlation to rainfall as measured by the disdrometers. However, there are strong systematic overestimations (factors of 1.2–2.1) which cannot be attributed to the R–k relationship. We observe attenuations in the order of 3 dB due to antenna wetting under fog or dew conditions. We also observe fluctuations of a similar magnitude related to changes in temperature. The response of different makes of microwave antennas to many of these phenomena is significantly different even under the exact same operating conditions and configurations.

scholarly journals An urban microwave link rainfall measurement campaign

2017 ◽  
Author(s):  
Thomas C. van Leth ◽  
Aart Overeem ◽  
Remko Uijlenhoet ◽  
Hidde Leijnse
Keyword(s):  
Communication Networks ◽  
Land Surface ◽  
Urban Areas ◽  
Rain Gauge ◽  
Operating Conditions ◽  
Retrieval Algorithm ◽  
Time Variability ◽  
Great Opportunity ◽  
Temporal Sampling ◽  
Microwave Link

Abstract. Microwave links from cellular communication networks have been shown to be able to provide valuable information concerning the space-time variability of rainfall. In particular over urban areas, where network densities are generally high, they have the potential to complement existing dedicated infrastructure to measure rainfall (gauges, radars). In addition, microwave links provide a great opportunity for ground-based rainfall measurement for those land surface areas of the world where gauges and radars are generally lacking. Such information is not only crucial for water management and agriculture, but also for instance for ground validation of space-borne rainfall estimates such as those provided by the GPM (Global Precipitation Measurement) mission. The campaign described in this paper is dedicated to address several errors and uncertainties associated with such quantitative precipitation estimates in detail. The core of the experiment is provided by three co-located microwave links installed between two major buildings on the Wageningen University campus, approximately 2 km apart: a 38 GHz commercial microwave link, and 26 GHz and 38 GHz (dual-polarization) research microwave links. Transmitting and receiving antennas have been attached to masts installed on the roofs of the two buildings, about 30 m above the ground. This setup has been complemented with an infrared large-aperture scintillometer, installed over the same path, as well as 5 laser disdrometers and an automated rain gauge positioned at several locations along the path. Temporal sampling of the received signals was performed at a rate of 20 Hz. The setup is being monitored by time-lapse cameras to assess the state of the antennas as well as the atmosphere. The experiment has been active between August 2014 and December 2015. Data from an existing automated weather station situated just outside Wageningen was further used to compare and to interpret the findings. We find that a basic rainfall retrieval algorithm with no corrections already provides a reasonable correlation to rainfall as measured by the disdrometers. The microwave links do give a significant overestimation. We further investigate several events covering different attenuating phenomena: Rainfall, solid precipitation, temperature, dew, antenna wetting and clutter. We also briefly explore cases where several phenomena play a role. We conclude that the response of different makes of microwave antennas to many of these phenomena is significantly different even under the exact same operating conditions and configuration.

A Citizen Observatory at schools to train a rainfall retrieval algorithm based on Earth Observation

2020 ◽  
Author(s):  
Sandra de Vries ◽  
Monica Estebanez Camarena
Keyword(s):  
Climate Change ◽  
Data Collection ◽  
West Africa ◽  
Rain Gauge ◽  
Earth Observation ◽  
Rainfall Data ◽  
Northern Ghana ◽  
Retrieval Algorithm ◽  
Educational Module ◽  
Rainfall Retrieval

<p>West Africa’s economy is mainly sustained on agriculture and over 70% of crops are rain-fed. Economic growth and food security in this region is therefore highly dependent on the knowledge of rainfall patterns. According to the IPCC, the Global South will seriously suffer from climate change. As traditional rainfall patterns shift, accurate rainfall information becomes crucial for farmers to optimize food production.</p><p>The scarce rain gauge distribution and data transmission challenges make rainfall analysis difficult in these regions. Satellites could offer a solution to this problem, but present satellite products do not account for local characteristics and perform poorly in West Africa.</p><p>A rainfall retrieval algorithm, developed within the Schools and Satellites (SaS) project, could overcome the lack of ground data and good rainfall satellite products through earth observation and advanced machine learning. However, to validate such an algorithm requires a high amount of rainfall data from ground stations. Since rain gauges are scarce in West Africa, a (temporary) high density observation network is necessary to strengthen the training and validation dataset provided by TAHMO and GMet ground measurements. SaS therefore engages with schools in Northern Ghana to build a Citizen Observatory. </p><p>SaS is being funded by the European Space Agency as one of the pilot projects of CSEOL (Citizen Science and Earth Observation Lab). It is being developed in a cooperation between TU Delft, PULSAQUA, TAHMO Ghana, Smartphones4Water (S4W) and GMet. The Proof-of-Concept Algorithm will be fed with data collected in the Citizen Observatory during the rainy season of 2020.</p><p>This Citizen Observatory will be built around the already existing infrastructure of a classroom where Climate Change is amongst the topics in the Ghanaian teaching curriculum. We aim to provide a Climate Change educational module that can be used directly by the teachers. The educational module incorporates the building of their own low-cost rain gauge to be used for manual rainfall data collection. This rainfall collection method has already been highly tested by S4W in Nepal. Students will design their own research around the daily rainfall measurements, which they will submit via a web application called Open Data Kit (ODK). The data is being validated by including a picture of the rainfall measurement that is checked with the number passed on by the citizen scientist.</p><p>The Citizen Observatory will be placed under the existing TAHMO and S4W infrastructures to respectively continue the interaction with schools and to continue data collection, -validation and -visualization. If the algorithm proofs to indeed perform better than current satellite products for the pilot area in Northern Ghana, the Citizen Observatory could in the future help to validate and improve the product for the whole of West-Africa.</p><p>To enable the use of this Citizen Observatory for management of water resources and in this case more and better rainfall data, much effort is needed. We will demonstrate which measures we have taken to ensure that the Citizen Observatory performs with enough quality, and how (if done well) it has the potential to increase the impact of this study.</p>

A scattering-based over-land rainfall retrieval algorithm for South Korea using GCOM-W1/AMSR-2 data

2017 ◽  
Vol 53 (3) ◽  
pp. 385-392 ◽  
Author(s):  
Young-Joo Kwon ◽  
Hayan Shin ◽  
Hyunju Ban ◽  
Yang-Won Lee ◽  
Kyung-Ae Park ◽  
...  
Keyword(s):  
South Korea ◽  
Retrieval Algorithm ◽  
Rainfall Retrieval

scholarly journals Understanding Hydrodechlorination of Chloromethanes. Past and Future of the Technology

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1462
Author(s):  
Sichen Liu ◽  
Javier A. Otero ◽  
Maria Martin-Martinez ◽  
Daniel Rodriguez-Franco ◽  
Juan J. Rodriguez ◽  
...  
Keyword(s):  
Catalyst Deactivation ◽  
Global Analysis ◽  
Catalytic Performance ◽  
Operating Conditions ◽  
Light Olefins ◽  
Synthesis Methods ◽  
Chlorinated Pollutants ◽  
New Perspective ◽  
Kinetics Of ◽  
Experimental And Theoretical Studies

Chloromethanes are a group of volatile organic compounds that are harmful to the environment and human health. Abundant studies have verified that hydrodechlorination might be an effective treatment to remove these chlorinated pollutants. The most outstanding advantages of this technique are the moderate operating conditions used and the possibility of obtaining less hazardous valuable products. This review presents a global analysis of experimental and theoretical studies regarding the hydrodechlorination of chloromethanes. The catalysts used and their synthesis methods are summarized. Their physicochemical properties are analyzed in order to deeply understand their influence on the catalytic performance. Moreover, the main causes of the catalyst deactivation are explained, and prevention and regeneration methods are suggested. The reaction systems used and the effect of the operating conditions on the catalytic activity are also analyzed. Besides, the mechanisms and kinetics of the process at the atomic level are reviewed. Finally, a new perspective for the upgrading of chloromethanes, via hydrodechlorination, to valuable hydrocarbons for industry, such as light olefins, is discussed.

scholarly journals Total ozone column intercomparison of Brewers, Dobsons, and BTS-Solar at Hohenpeißenberg and Davos in 2019/2020

2021 ◽  
Vol 14 (7) ◽  
pp. 4915-4928
Author(s):  
Ralf Zuber ◽  
Ulf Köhler ◽  
Luca Egli ◽  
Mario Ribnitzky ◽  
Wolfgang Steinbrecht ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Standard Deviation ◽  
Total Ozone ◽  
Retrieval Algorithm ◽  
Measurement Campaign ◽  
Total Ozone Column ◽  
Stratospheric Temperature ◽  
Retrieval Algorithms ◽  
Double Monochromator ◽  
Ozone Column

Abstract. During the 2019/2020 measurement campaign at Hohenpeißenberg (Germany) and Davos (Switzerland) we compared the well-established Dobson and Brewer spectrometers (single- and double-monochromator Brewer) with newer BTS array-spectroradiometer-based systems in terms of total ozone column (TOC) determination. The aim of this study is to validate the BTS performance in a longer-term TOC analysis over more than 1 year with seasonal and weather influences. Two different BTS setups have been used – a fibre-coupled entrance optic version by PMOD/WRC called Koherent and a diffusor optic version from Gigahertz Optik GmbH called BTS-Solar, which proved to be simpler in terms of calibration. The array-spectrometer-based BTS systems have been calibrated with traceability to NMI, and both versions of TOC retrieval algorithms are based on spectral measurements in the range of 305 to 350 nm instead of single-wavelength or wavelength pair measurements as per Brewer or Dobson. The two BTS-based systems, however, used fundamentally different retrieval algorithms for the TOC assessment, whereby the retrieval of the BTS-Solar turned out to achieve significantly smaller seasonal drifts. The intercomparison showed a difference of the BTS-Solar to Brewers of < 0.1 % with an expanded standard deviation (k=2) of < 1.5 % over the whole measurement campaign. Koherent showed a difference of 1.7 % with an expanded standard deviation (k=2) of 2.7 % mostly caused by a significant seasonal variation. To summarize, the BTS-Solar performed at the level of Brewers in the comparison in Hohenpeißenberg. The BTS-Solar showed very small dependence on the slant path column compared to the double-monochromator Brewer and performed better than the single-monochromator Brewer. Koherent showed a strong seasonal variation in Davos due to the sensitivity of its ozone retrieval algorithm to stratospheric temperature.

scholarly journals The MSG Technique: Improving Commercial Microwave Link Rainfall Intensity by Using Rain Area Detection from Meteosat Second Generation

2021 ◽  
Vol 13 (16) ◽  
pp. 3274
Author(s):  
Kingsley K. Kumah ◽  
Joost C. B. Hoedjes ◽  
Noam David ◽  
Ben H. P. Maathuis ◽  
H. Oliver Gao ◽  
...  
Keyword(s):  
Second Generation ◽  
Rainfall Intensity ◽  
Rain Gauge ◽  
Conventional Technique ◽  
Rain Area ◽  
Evaluation Scores ◽  
Rain Events ◽  
Spatially Varying ◽  
Microwave Link ◽  
Rainfall Estimates

Commercial microwave link (MWL) used by mobile telecom operators for data transmission can provide hydro-meteorologically valid rainfall estimates according to studies in the past decade. For the first time, this study investigated a new method, the MSG technique, that uses Meteosat Second Generation (MSG) satellite data to improve MWL rainfall estimates. The investigation, conducted during daytime, used MSG optical (VIS0.6) and near IR (NIR1.6) data to estimate rain areas along a 15 GHz, 9.88 km MWL for classifying the MWL signal into wet–dry periods and estimate the baseline level. Additionally, the MSG technique estimated a new parameter, wet path length, representing the length of the MWL that was wet during wet periods. Finally, MWL rainfall intensity estimates from this new MSG and conventional techniques were compared to rain gauge estimates. The results show that the MSG technique is robust and can estimate gauge comparable rainfall estimates. The evaluation scores every three hours of RMSD, relative bias, and r2 based on the entire evaluation period results of the MSG technique were 2.61 mm h−1, 0.47, and 0.81, compared to 2.09 mm h−1, 0.04, and 0.84 of the conventional technique, respectively. For convective rain events with high intensity spatially varying rainfall, the results show that the MSG technique may approximate the actual mean rainfall estimates better than the conventional technique.

scholarly journals Alignment of scanning lidars in offshore wind farms

2021 ◽  
Author(s):  
Andreas Rott ◽  
Jörge Schneemann ◽  
Frauke Theuer ◽  
Juan José Trujillo Quintero ◽  
Martin Kühn
Keyword(s):  
Wind Turbine ◽  
Long Range ◽  
Wind Farms ◽  
Operating Conditions ◽  
Offshore Wind ◽  
Alignment Error ◽  
Position Information ◽  
Measurement Campaign ◽  
Scanning Lidar ◽  
Range Scanning

Abstract. Long-range Doppler wind lidars are applied more and more for high resolution areal measurements in and around wind farms. Proper alignment, or at least knowledge on how the systems are aligned, is of great relevance here. The paper describes in detail two methods that allow a very accurate alignment of a long-range scanning lidar without the use of extra equipment or sensors. The well-known so-called Hard Targeting allows a very precise positioning and north alignment of the lidar using the known positions of the surrounding obstacles, e.g. wind turbine towers. Considering multiple hard targets instead of only one with a given position in an optimization algorithm allows to increase the position information of the lidar device and minimizes the consequences of using erroneous input data. The method, referred to as Sea Surface Leveling, determines the leveling of the device during offshore campaigns in terms of roll and pitch angle based on distance measurements to the water surface. This is particularly well suited during the installation of the systems to minimize alignment error from the start, but it can also be used remotely during the measurement campaign for verification purposes. We applied and validated these methods to data of an offshore measurement campaign, where a commercial long-range scanning lidar was installed on the transition piece platform of a wind turbine. In addition, we present a model that estimates the quasi-static inclination of the device due to the thrust loading of the wind turbine at different operating conditions. The results show reliable outcomes with a very high accuracy in the range of 0.02° in determining the leveling. The importance of the exact alignment as well as the possible applications are discussed in this paper. In conclusion, these methods are useful tools that can be applied without extra effort and contribute significantly to the quality of successful measurement campaigns.

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