Mar 272017
 

The 11th European Conference on Antennas and Propagation, held in Paris, France, on 19-24 March 2017. Jiapeng Yin, the Ph.D. student in the Atmospheric Remote Sensing Group of the GRS department, made a presentation titled “Spectral Polarimetric Features Analysis of Wind Turbine Clutter in Weather Radar”. This paper was selected to be a finalist for a best paper award, and the finalist papers were requested to present their work in a work in a special poster session dedicated to the Awards. This session took place on Thursday afternoon, March 23, 2017, and gave a possibility for many additional discussions and contacts. Unfortunately, we did not receive the Award.

The increasing size and quantity of wind turbines worldwide provide an environmental-friendly solution to fulfill the growing demand for energy. However, this also brings in a new dynamic clutter named wind turbine clutter (WTC) for weather radars, and it has gradually become a concern because WTC deteriorates the radar performance severely. In this paper, Jiapeng mainly introduced the advanced waveform measurements of WTC using the TUD PARSAX radar. Furthermore, the micro-Doppler signature and the spectral-polarimetric properties of WTC were studied. Finally, a WTC mitigation method was put forward.

Additionally, colleagues from the Microwave Sensing, Signals and Systems Group of EWI, Alexander Yarovoy, Oleg Krasnov, Stefano Medagli, and Sharef Neemat also presented at this meeting.

Mar 212017
 

Retrieving fall streaks within cloud systems using Doppler Radar

 

Abstract: Interaction of the ice crystals with super-cooled liquid droplets in mixed-phase clouds leads to an enhanced growth of the ice particles. However, such processes are still not clearly understood although they are important processes for precipitation formation in mid-latitudes. To better understand how ice particles grow within such clouds, changes of microphysical parameters of a particle population falling through the cloud have to be analyzed. The Transportable Atmospheric Radar (TARA) can retrieve the full 3-D Doppler velocity vector based on a unique three-beam configuration. Using the derived wind information, a new fall streak retrieval technique is proposed so that microphysical changes along those streaks can be studied. The method is based on Doppler measurements only. The shown examples measured during the ACCEPT campaign (Analysis of the Composition of Clouds with Extended Polarization Techniques) demonstrate that the retrieval is able to capture the fall streaks within different cloud systems. These fall streaks can be used to study changes in a single particle population from its generation (at cloud top) till its disintegration. In this study fall streaks are analyzed using radar moments or Doppler spectra. Synergetic measurements with other instruments during ACCEPT allow the detection of liquid layers within the clouds. The estimated microphysical information is used here to get a better understanding of the influence of super-cooled liquid layers on ice crystal growth. This technique offers a new perspective for cloud microphysical studies.

The full text of the paper from L. Pfitzenamier et. al., 2017, can be found in the here on the J-Tech web page

 

Jan 242017
 

This year, 2017, on March 27th – 31st an international workshop on “Turbulence in Stably Stratified planetary boundary layers” will be held at the Delft University of Technology, Netherlands.

This workshop is organized by ATMOS group members; Bas van de Wiel, Sukanta Basu, Peter Baas, Steven van der Linden and Bert Holtslag from Wageningen University and Research.

Purpose of this decennial meeting is to assess the ‘State-of-the-art’ in SBL research and to see in what directions the research field is moving. Moreover, we aim to probe into the contemporary scientific problems and challenges and to find the critical issues that will require extra attention in the near-future.

The meeting is the third in line after successful predecessors of Lovanger (Sweden; 1997) and Sedona (U.S.; 2007). For an overview on those meetings, see the references below.

The setup of the meeting is unlike a ‘regular conference’, in a sense that the latest results from each presenter’s own group will not be the main focus. Rather, for each scientific topic (two) keynote speakers have been invited. Those speakers will give an overview on the topic (for example a brief historical outline) and –identify the challenging questions related to this topic. Next, the questions are collected and discussed in subgroups of participants who will present their findings in one summary slide. Lastly, the topic is wrapped up during a panel discussion.

In addition to the keynote speakers and other participants, PhD students are also invited. They are encouraged to present a poster with challenging questions related to their research. The best poster will receive a prize and its topic will be discussed in subgroups as well.

List of keynote speakers:

Acevedo, Anderson, Angevine, Ansorge, Beyrich, Edwards, Fedorovich, Galperin, Grachev, Holtslag, Jonker, McNider, Mironov, Sorbjan, Steeneveld, Sullivan, Sun, Zilitinkevich

Keywords discussion topics (inter alia): 

Coherent structures and global intermittency (numerical & observational aspects); non-traditional SBLs: MO vs. non-MO similarity; transitional SBLs; radiative SBLs; polar/long-lived SBL; surface heterogeneity & mesoscale effects; urban SBL; recent observational & theoretical developments; total turbulent Energy concepts; atmosphere-surface interactions, gravity waves & turbulence… 

For more information and regristration please visit: www.sbldelft.nl

Photo: Riccardo Riva
Photo: Riccardo Riva

Jan 192017
 

17 February 2017 | 12:45 – 18:00
location: Theaterzaal (Sport & Culture)

 

Please register by sending an email to Secr-grs-citg@tudelft.nl.

The Geoscience & Remote Sensing (GRS) department of TU Delft, the TU Delft Climate institute and he Royal Netherlands Meteorological institute KNMI are pleased to invite you to the seminar Urban Air Quality, to be held at the TU Delft Theaterzaal (Sports & Culture) on Friday afternoon 17th February 2017.

Human activities, including industry, traffic, energy generation and food production, have an adverse impact on air quality. This is especially the case in urban areas, where more than half of the world populations lives. Ground based and satellite observations show that policies to reduce the emissions of pollutants are successful in improving air quality. However, is enough done to protect the health of the people in the cities and what can cities in developing countries learn from these successes?

This symposium will bring together experts in the field of  health effects, policy, emission monitoring, ground based observations and satellite remote sensing. It targets a broad audience from students in diverse topics, public, industries, policy makers and researchers. In addition to presentations, there will be possibilities for interactive discussions with the speakers.

See the program below

Dec 092016
 

The increasing size and quantity of wind turbines worldwide provide an environmental-friendly solution to fulfill the growing demand for energy. However, this also brings in a new dynamic clutter named wind turbine clutter (WTC) for weather radars, and it has gradually become a concern because WTC deteriorates the radar performance severely. During December 6-7, to bring together the increasing number of experts and researchers in the field of electromagnetic waves within the context of wind energy plants and to offer a platform to discuss arising and existing problems, the focus days EMWT’16 provide a fitting platform. In contrast to other conferences EMWT’16 will cover the whole field of electromagnetic waves and wind energy in one specialist meeting in Fraunhofer Institute for High Frequency Physics and Radar Techniques .

Jiapeng Yin, the Ph.D. student in the Atmospheric Remote Sensing Group of the GRS department, made a presentation named “Signatures Study of Wind Turbine Clutter in Polarimetric Doppler Weather Radar” . He mainly introduced the micro-Doppler signature and the spectral-polarimetric properties of WTC based on the measurements of the PARSAX radar in TU Delft campus. This work relies on a recently-accepted conference processing of European Conference on Antennas and Propagation.

Additionally, colleagues from the Microwave Sensing, Signals and Systems Group of EWI, Oleg Krasnov, Faruk Uysal and Stefano Medagli also presented in this meeting. More information can be found on the following websites:

http://www.fhr.fraunhofer.de/en/events/emwt-2016.html

IMG_0674             IMG_0635               IMG_0617

Dec 082016
 

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.

DSC04278   IMG_0393  IMG_0291

Dec 012016
 

The Buys Ballot Research School (BBOS) 2016 organized by the IMAU was held in Oranjewoud . This symposium is aimed on PhD students at dutch universities working on fundamental and applied studies of the climate system.

This year PhD students from the GRS-department and the ATMOS group contributed on a wide range of topics:

  • Julien Chimot – Presentation : Retrieving aerosol height from space: A neural network approach applied to OMI O2-O2 measurements PDF
  • Steven van der Linden – Presenation : 1001 nights, a Fairy Tale at Cabauw
  • Thomas Frederikse – Presentation : Closing the Sea Level Budget at a Regional Scale
  • Dimitra Mamali – Poster : Atmospheric particles size distribution and hygroscopicity at Cabauw for the period 2008-2014
  • Antoon van Hooft- Poster : LES is More
    This poster won the award for ‘Best Poster Presentation’ according to the jury and can be viewed here: PDF

We hope to see you at the next BBOS symposium!

Sep 232016
 

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

Nov 182015
 

Members of the ATMOSpheric remote sensing groupe contrubuted to the AMS conference, 14-18 September 2015, Norman OK, USA

Ricardo Reinoso Rondinel contributed presenting a poster:

Title: “High resolution estimation of specific differential phase and backscatter differential phase for polarimetric X-band weather radars

  • An advanced method to estimate the specific differential phase (Kdp) and backscatter differential phase (dhv) from rain at X-band frequencies is proposed. The method aims to obtain high spatial resolution of Kdp and dhv estimators while controlling their inherent bias-variance dilemma. In addition, the variance of Kdp was mathematically formulated for quality control.
  • Poster and abstract link here
  • This poster was awarded as the 3rd best student poster presentation.

Albert Oude Nijhuis  presented a poster, too:

Title: “Turbulence intensity retrieval in precipitation via optimal estimation using polarimetric radar

Summary and a pdf version of his paster can be found here

The talks of Lukas Pfitzenmaier

Title: “Correcting radar Doppler spectra for atmospheric dynamics to study microphysics within mixed phase clouds” (here)

and Yunlong Li

Title: “A Novel Radar-Based Visibility Estimator

are also avilable online (here)

Aug 242015
 

londonreading

During the last 4 weeks I was for a secondment at the University of Reading. Main goal was to learn more about microphysical retrievals of cloud properties. But also exchanging knowledge and ideas was on the agenda. So I was very glad that I got the chance to work with Chris Westbrook and his colleagues.

houseSince the very successful ACCEPT campaign I have plenty of data to look into and develop ideas. One of them was to retrieve mean ice particle size using the wavelength ration of the operated radars  (3 GHz and 35 GHz). The group in Reading was really helpful in answering questions and discuss first preliminary results. They already had experience with such retrievals.

Discussion with other PhDs and Scientists brought also some very fruitful and promising input. I exchange some of the ACCEPT and hope that the collaboration will go on in the future. An improvement of my retrieval for retrieving fall-streaks within radar data was tested on a different data set. This improved the understanding of my own retrieval and helped to validate it.

So all in all a successful exchange for both sides. I thank once again the colleagues from Reading for the collaboration and all the rest. And I hope that the collaboration will go on in the future