Jun 272017
 

The Geoscience & Remote Sensing (GRS) Department organised a poster session held on May 12th at the CiTG building. The aims of the poster day were to stimulate interaction and collaboration among the GRS staff and students and to promote our department to the wider CiTG.
The session was very lively and hosted over 30 posters, from graduate students, teaching and supporting staff, which spanned a wide range of topics. This very successful session sparked the idea of extending it next year by including also other Departments within the TU Delft.

 

May 262017
 

Narrow-band Clutter Mitigation in Spectral Polarimetric Weather Radar

Abstract: In this paper, a new clutter suppression method named the moving double spectral linear depolarization ratio (MDsLDR) filter is put forward to mitigate narrow-band clutter in weather radars. The narrow-band clutter observed in the Doppler domain includes: 1) stationary clutter such as ground clutter and 2) non-stationary clutter such as artifacts caused by the radar system itself or external sources. These artifacts are difficult to remove because they are not confined to specific azimuth and range bins. Based on the difference of the spectral-polarization feature and the spectral continuity of precipitation and clutter, MDsLDR filter can remove  ground clutter, artifacts and noise. The performance of the newly proposed filter is assessed by data collected by the Doppler-polarimetric IRCTR Drizzle Radar (IDRA). Three precipitation cases are considered in this paper: moderate/light precipitation, convective precipitation with hook-echo signature and light precipitation with severe artifact contamination. Furthermore, the implementation of the MDsDLR filter requires relatively low computation complexity, so that the MDsLDR filter can be operated in real time.

The full text of the paper from Jiapeng Yin et. al., 2017, can be found here on the IEEE Xplore webpage

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

 

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
Jun 122015
 

RainGain is a project within the Framework of the COP21 Preparation and stands for

“RESEARCHERS & WATER MANAGERS PREPARING CITIES FOR A CHANGING CLIMATE”

Raingain_converence

The EU INTERREG NWE IVB RainGain project has focused on recent remote sensing technologies to achieve a finer urban water management and to build up resilience to weather extremes and climate change. The RainGain conference will address all the issues related to high-resolution rainfall measurement, nowcasting and hydrological modelling, as well as their advanced applications to urban water management and stakeholder’s capacity building.

More info can be found here:

http://www.raingain.eu/en/raingain-final-conference-regitration-open

The poster that was presented was titled: ” Dual-Polarimetric X-Band Weather Radar: Accurate Rainfall Estimation and Storm Observations ” and can be found here.

More RainGain news:

International RainGain Workshop on March 24th 2015 in Rotterdam.

Topics:

  • Extreme rainfall in Jakarta
  • Amsterdam Rainproof
  • Coping with extreme rainfall
  • Added value X-band radar

More info can be found in: http://www.raingain.eu/en/node/4619

http://www.raingain.eu/en/raingain-international-workshop-rotterdam-0

Ricardo_small herman_small

by Ricardo Reinoso Rondinel

Apr 202015
 

Last week Stephanie Prianto Rusli and Lukas Pfitzenmaier presented posters at the European Geoscience Union in Vienna. This conference gave a grate opportunity to meet a brought range of scientists from all kinds of Geoscience and come into discussion. It also gave the opportunity to go into interdisciplinary sessions and generate new ideas.

EGU_2015_2EGU_2015_3EGU_2015_1

Stephanies poster was in the the session: Remote Sensing of Clouds and Aerosols: Techniques and Applications and its title: Multi-sensor approach to retrieving water cloud physical properties and drizzle fraction  (poster here)

Lukas poster could be find in the new session about Observing and modeling processes in moderately supercooled clouds and was dealing with Effect of cloud microphysics on particle growth under mixed phase conditions  (poster here). Discussions and comments within the supercooled cloud community where very fruitful and caused quite some attention. So the changes are high to have a second one in the next EGU 2016.

 

Apr 022015
 

In a few weeks (in the 4th quarter), the third edition of the Atmospheric observation course (CIE4608) will start at the CEG faculty. The course is focusing on the observation of the different atmospheric components that are required for current weather and climate applications at different temporal and spatial scales and from different observation plateforms.

For TU Delft students it is now possible to enrol to the course. More information can be found on the study guide by clicking on this link. I will be leading the course, so feel free to contact me if any further question via the link above.

Find below the flyer for the course this year:

Flyer2015_CIE4608I’m looking forward to see you all soon,

Yann

Nov 272014
 

In the last ITaRS Summer School on “Clouds and Precipitation: Observation and Processes”, which was held in the Jülich Research Center (Germany), the group working on the topic “When does a cloud form?” was selected as the one that made the best work in such a short period of time. The name of the group was “The Transformers” and the integrants were Elisa Adirosi (CNR-ISAC, Rome, Italy), Pilar Gumà-Claramunt (CNR-IMAA, Potenza, Italy), Lukas Pfitzenmaier (TU Delft, The Netherlands), Stefanos Samaras (University of Potsdam, Germany) and Veronika Wolf (DWD, Lindenberg, Germany)

IMG_3940-700

The Transformers were awarded with the possibility to attend the meeting of TOPROF, the acronym of a COST Action standing for “Towards operational ground based profiling with ceilometers, doppler lidars and microwave radiometers for improving weather forecasts”, which was held in the DTU Risø Campus in Roskilde, Denmark. There, the students presented to the participants of the meeting the ITaRS project, the work they did during the Summer School, the Atmospheric Emitted Radiance Interferometer (AERI) instrument and their individual research projects. Furthermore, they attended many interesting talks, participated in the working groups meetings (ceilometers [WG1], Doppler lidars [WG2], Microwave radiometers [WG3] and/or Data assimilation [WG4]) and had the opportunity to discuss with experts in Remote Sensing of the atmosphere.

Finally, the three ITaRS students stayed one day after the meeting to visit Copenhagen

P1060400 P1060407

We would like to thank ITaRS and TOPROF for the opportunity of attending this interesting experience.