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


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:
– Competition between CarbonSat and FLEX:
– the TROPOMI project:

Julien Chimot
Jun 122015

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



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:

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.


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

More info can be found in:

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.


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,


Mar 252015

The fellows from the ITaRS network met between March 18th-20th 2015 in Barcelona, at UPC (Universitat Politècnica de Catalunya).


The two first days were dedicated on a course about writing skills. Two lecturers from WAS gave us tips and advice to understand better the process of writing a scientific paper. The fellows had to prepare an abstract for a possible article in order to receive direct feedback to improve the understandability of this short text. The interactivity of the lectures made them very interesting. Important to mention is the powerful impact these advice can have on our future scientific publications.

The last day was consecrated to data assimilation. Two researchers from ECMWF (Reading, UK) came to introduce this concept. They explained how observations are useful and important in order to increase the predictability of the weather forecasts. The lectures were very interesting and the quality of their content was at very high scientific level.

MareNostrum3_supercomputer_UPCvisit of supercomputer UPC

We got the chance to visit some of the installations of UPC. We visited the building which houses the impressive supercomputer called MareNostrum (1 petaflop of speed!). The funny fact comes from the original use of this building: it was indeed a former chapel as you can see on the picture.

Finally, it was good to see again all the fellows. We managed to find time to discuss and speak about questions related to ITaRS. We also enjoyed a bit of the nice life of this pretty city.
Ole! :)

Mar 142015

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).