I am fascinated by the observation-and-interpretation process. Most observations we do - whether scientific or social- are indirect: one never measures the meaning directly, but needs assumptions and models before the interpretation can be made. This is also true for remote sensing. The direct measurement is often expressed in terms of energy or power, but what one wants to know is: how much rain is falling?, or how do aerosols change clouds? This requires a good understanding of the underlying physics, the observation technology and of signal processing. It truly needs a multi-disciplinary approach.
Science and education go hand in hand. Teaching sharpens the scientist's mind, and at the same time educates students within the practice of scientific enterprise. To a large extent science and technology are autonomous enterprises, but the actors- scientists and engineers- share a special responsibility: they should serve mankind. Technical and exact sciences are in many respects the motors that drive the modern society and high quality educational programs are crucial for maintaining the high standard of living, today and in the future. Educational programs should reflect the interaction between science and technology on the one hand, and societal needs on the others. An educational program should put content in context:
it has to unveil the societal relevance of technology;
it has to be open to new developments in the society;
it has to challenge the students to think beyond the boundaries of their scientific disciplines;
it has to make the students enthusiastic and proud.
Climate change: the role of clouds and aerosols in the climate system
Remote sensing of the atmosphere
Forecasting society-disruptive weather
Education in relation to research
Why is the climate changing?
The best understood source for global warming is the increasing level of greenhouse
gases in the atmosphere. The least understood factor is the effect of aerosols
and clouds. Aerosols are fine dust particles in the atmosphere that serve as catalysers formation of water
droplets. An increase of the aerosol concentration, by human activities for
instance, leads to a larger number of cloud particles and longer cloud
lifetime; the resulting cloud reflects more solar radiation. This may cool the
atmosphere in contrast to greenhouse warming. However, the clouds will also
respond to global warming. Cloud decks might open up so that more solar
radiation reaches the surface to warm it. It is largely unknown what clouds
will do in a changing climate: will they counteract global warming, or
How can we measure clouds?
It is difficult to measure physical properties of clouds. Not only do they drift at large heights, but also the cloud droplets are very small - in the order of 10 micrometer. The only way is remote sensing. Radars, lidars and radiometers are the key instruments. A radar and lidar transmit an electromagnetic signal towards the clouds and measure the reflections. A radar operates at a wavelength between 3 mm and 20 cm, whereas a lidar uses a laser beam as the source, usually in the infrared. A radiometer is a passive device, and only measures atmospheric radiation emanating from the atmosphere. But why do we need these different instruments? Is one instrument not enough? No. Sometimes the cloud droplets are too small to be seen by radar, and sometimes the clouds are too thick for lidar signals to penetrate to the cloud top. Only the combination of instruments - sensor synergy - will give a full picture. Central to our work is Cesar Observatory
Experimental remote sensing
Sensor synergy (radar, lidar, radiometry) to measure cloud properties relevant for climate studies
Radar retrieval of rainfall parameters: doppler-polarimetric and dual-frequency techniques.
Space-based retrieval of cloud parameters
Radar Doppler-polarimetry for atmospheric dynamics.
Radar Doppler-polarimetry for mixed-phase clouds studies.
Coherent scattering of radar waves by clouds
Electro-magnetic scattering by the melting layer in precipitation.
Scattering by rain
Multiple scattering of lidar waves by water clouds.
The radar discrepancy: scattering by semi-discrete clouds.
Processing concepts for the TU Delft atmospheric radar systems
Doppler-polarimetric target enhancement
System studies and design
Scientific user strategies of the transportable atmosphere radar TARA
Development of the IRCTR Drizzle radar IDRA
development of courses and course material;
coordination of education activities;
organization of special events (excursions, student symposia, guest lectures);
quality control of the education program;
supervision of graduate students.
I am heading the atmospheric remote sensing group at TU Delft. In this capacity I am supervising a
research and technical team - with an average size of 10 persons - and am
responsible for all managerial tasks related to it:
· Project acquisition and management;
· Quality assurance;
· Recruitment of post-docs, PhD students
and guest scientists;
· Initiating and stimulating (inter)national
· Definition of the research program;
· Communication with scientific partners and
director of the TU Delft Climate Institute, involving all TU Departments that deal
with understanding, mitigation and adaptation of climate change.
From March 2013 to September 2014 I was Director of
Education of the Department of Civil Engineering and Geosciences. The
department hosts 1800 students; 140 staff members are involved in the education
programs. I was responsible for the quality of all education programs the
November 2007 to August 2011 I was Director of Education of the Department of
Electrical Engineering, Mathematics en Computer Science. The department hosts
1700 students; 160 staff members are involved in the education programs. I was
responsible for the quality of all education programs the Department offers.
Full CV on request