A novel drone-based radar calibration experiment is carried out by Jiapeng Yin, Jinliang Li and Fred van der Zwan on Novermber 1st and 3rd. The research aims to develop and implement the new technology in calibration for the next generation of weather radars. This is urgent and timely research as the current weather radars are not the optimum information sources for water management in urban areas – so prone to the increased occurrence of extreme rainfall. This research will use a micro-drone hexacopter to carry the metal sphere and fly over two radars (S-band TARA and X-band IDRA) to complete the process in Cabauw.
Assessment of the rain drop inertia effect for radar-based turbulence intensity retrievals
A new model is proposed on how to account for the inertia of scatterers in radar-based turbulence intensity retrieval techniques. Rain drop inertial parameters are derived from fundamental physical laws, which are gravity, the buoyancy force, and the drag force. The inertial distance is introduced, which is a typical distance at which a particle obtains the same wind velocity as its surroundings throughout its trajectory. For the measurement of turbulence intensity, either the Doppler spectral width or the variance of Doppler mean velocities is used. The relative scales of the inertial distance and the radar resolution volume determine whether the variance of velocities is increased or decreased for the same turbulence intensity. A decrease can be attributed to the effect that inertial particles are less responsive to the variations of wind velocities. An increase can be attributed to inertial particles that have wind velocities corresponding to an average of wind velocities over their backward trajectories, which extend outside the radar resolution volume. Simulations are done for the calculation of measured radar velocity variance, given a 3-D homogeneous isotropic turbulence field, which provides valuable insight in the correct tuning of parameters for the new model.
The full paper from A. Oude Nijhuis et. al. can be found here
– ATMOS 2015: http://seom.esa.int/atmos2015/
– Competition between CarbonSat and FLEX: http://www.esa.int/Our_Activities/Observing_the_Earth/Save_the_date_selection_of_ESA_s_eighth_Earth_Explorer
– the TROPOMI project: http://www.tropomi.eu/
On Wednesday 29th October 2014 was the official kick-off meeting of Waterlab which took place in the Science Center of TU Delft (link1, link2). Almost 300 pupils from primary schools of Delft had a first hint about science and rain measurements.
Currently, four primary schools in Delft area are involved in the project. The teachers and pupils measure local precipitations with handmade raingauges and compile all measurements to a dedicated website called MijnWaterlab. Besides these observations, rainfall intensities are also measured continuously since September 2014 with weather stations located in each of these schools (see picture on the right) in order to have a better idea about the variability of precipitation at the scale of a city. Easy comparisons can be made between each dataset.
On the other hand, in the upcoming weeks, students from secondary schools from Delft will integrate the project and the roof of these lyceums will be equipped with a station for measuring rainfalls. The students there will have to deal with scientific projects in relation with the analysis of these observations.
Since today, another weather station is also located in the Science Center to continue with the densification of the network of stations in Delft. The particularity of this station is that the data are collected automatically via wired internet connection with the use of a RaspberryPi-based system (see picture on the right) that was under development during the last months.
A quasi-similar configuration (using 3G wireless internet connection) will be applied very soon to the stations installed in schools (currently a visit to each school is needed to manually collect the data).
On March 27th started the WaterLab Delft project.
This project is a collaboration between different organizations:
– Gemeente Delft and Gemeente Rotterdam,
– HH van Delfland and HH van Schieland en de Krimpenerwaard,
– Unie van Waterschappen,
– Hogeschool Rotterdam,
– UNESCO-Institute for Water Education,
– TNO, Deltares and TU Delft.
It consists in a better understanding of the water cycle in urban areas. It involves specialists of the water cycle and of the atmosphere and also students/pupils. It implies education and improvement of knowledge.
Edouard Martins from our group is currently working with three TU Delft students (David Kester, Ingo Schilken, Tim Gebraad). Their current work is to deal with the calibration of sensors mounted on several weather stations for a better accuracy of meteorological parameters (temperature, pressure, humidity, rain, wind, radiation) and for a better assessment of the impact of urban features (buildings, trees) in the measurement of these quantities.
The next step is to deploy several calibrated weather stations in high schools located in Rotterdam and Delft to have a better representation of the variability of these meteorological parameters in the urban areas of South Holland.
You can find more information in the official webpage of the project (in dutch).
More updates and pictures will come soon.
On Wednesday we had an atmosphere observations day. Our colleagues from Met Office Iceland, Richard and Hermann, have demonstrated a mobile X-band unit, used during the expected volcanic eruptions in Iceland. Students have deployed the radar and launched a radiosonde from a mobile launcher. We visited our weather stations to collect the data and 2 out of 8 were knocked out due to strong wind.
Students have placed the 4 weather stations near lake Myvatn to study the atmospheric variability within this region. Locations are around a hill approximately 500m elevation and two around it near its base. One station is placed on the coast of a small lake next to this hill. The next part of the measurements is planned for Thursday by hiking up one of the higher hills with the sensors.
14 MSc students from TU Delft and University of Reykjavik are together with our PhD students Lukas and Igor as instructors in Iceland, setting up atmospheric measurements, alongside geodetic measurements, during the next 2 weeks. They will use 8 identical Davis Vantage Pro2 weather stations to capture the spatial horizontal variability of meteorological parameters east of lake Myvatn. The area has many small hot lakes and very little change of the nature by humans, making it a challenge to reach strategically desired locations, that they will select. On Wednesday, our meteorological colleagues from Met Office Iceland will visit us for a radiosonde launch, with which the students will determine the cloud base height, and compare it with another 4 methods to do the same (ceilometer laser, stereo cloud cameras, tachymetry and the theoretical approach using the theoretical temperature lapse rate and ground measured dew point temperature) to see how they rank and which one is the most useful for specific purposes.
For the update of the measurements outside the atmospheric part, visit our sister blog here: https://grsiceland.weblog.tudelft.nl
Since October 1st, students from the hymex-TU Delft DRI envi initiative have starting learning how to operate the TARA radar in order to take measurements during precipitation events during the HyMEx campaign. They will stay on site for the next 1-2 weeks.
You can follow their activities on the hymex weblog.
Already more than one month, our meteorological radar TARA is placed in Southern France to support the measurement of the Mediterrainean hydrological cycle in the frame of the HYMEX campaign (HYdrological cycle in the Mediterranean EXperiment).
We already collected quite some data of clouds and precipitation (quicklooks of the data collected are available here).
Today we are happy to add also a radar measurement of fog. This is quite a rare occasion, because the radiation fog that we have in Cabauw (Netherlands) is usually a much thinner layer, and too close to TARA to be measured. Instead the advection fog we are currently observing in France reaches up to heights of about 500m.