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

Jul 082015
 
High-Resolution Raindrop Size Distribution Retrieval Based on the Doppler Spectrum in the Case of Slant Profiling Radar

Doppler spectra from vertically profiling radars are usually considered to retrieve the raindrop size distribution (DSD). However, to exploit both fall velocity spectrum and polarimetric measurements, Doppler spectra acquired in slant profiling mode should be explored. Rain DSD samples are obtained from simultaneously measured vertical and slant profile Doppler spectra and evaluated. In particular, the effect of the horizontal wind and the averaging time are investigated.

The Doppler spectrum provides a way to retrieve the DSD, theradial wind,and a spectralbroadening factor by means of a nonlinear optimization technique. For slant profiling of light rain when the horizontal wind is strong, the DSD results can be affected. Such an effect is demonstrated on a study case of stratiform light rain. Adding a wind profiler mode to the radar simultaneously supplies the horizontal wind and Doppler spectra. Before the retrieval procedure, the Doppler spectra are shifted in velocity to remove the mean horizontal wind contribution. The DSD results are considerably improved.

Generally, averaged Doppler spectra are input into this type of algorithm. Instead, high-resolution, low-averaged Doppler spectra are chosen in order to take into account the small-scale variability of the rainfall. Investigating the linear relations at fixed median volume diameter, measured reflectivity-retrieved rainfall rate, for a slant beam, the consistency of the integrated parameters is established for two averaging periods. Nevertheless, the corresponding DSD parameter distributions reveal differences attributed to the averaging of the Doppler spectra.

The new aspects are to obtain the same retrieval quality as vertically profiling and highly average spectra in an automated way.

Link to C. Unals paper can be found here

Jun 222015
 
In view of preparing the future European operational satellite missions  dedicated to the atmosphere sounding, the European Space Agency (ESA) organised the ATMOS 2015 conference in at the university of Crete (Greece – Heraklion). This workshop allowed to exchange about retrieval techniques and harmonization of dataset  derived from past and present space-borne atmospheric missions (e.g. GOME, SCIAMACHY, MIPAS, GOMOS, OMI, IASI etc…) and application projects (e.g. Climate Change Initiative, Copernicus). Different sessions were organised about specific topics (greenhouse gases, reactive trace gases and air quality, limb missions). A strong focus was given on the crucial steps to be led by ESA for the successful  preparations of the Sentinel-4 and Sentinel-5 missions (scheduled between 2020 and 2021), the next TROPOMI mission on Sentinel-5 Precursor (before Summer 2016) and the competition between CarbonSat and FLEX missions with a final decision to be taken in September 2015. Around 200 researchers involved in the measurements of atmospheric trace gases, aerosols and clouds from passive satellite sensors were present.
Julien Chimot, PhD in the Atmosphere research team of the GRS department, had the opportunity to present his poster about the impact of aerosol particles on the quantification of  NO2 concentrations in the troposphere from the OMI measurements. This poster relies on a paper recently submitted to the AMT journal (Atmospheric Measurement Technique).
more information can be found on the following websites:
– 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/

Julien Chimot