Hydrology, Meteorology, and Complexity

From MHYM to COP21

Achieving the energy and ecological transitions to a smart, resilient, and desirable city, requires qualitative leaps in the observation, analysis, modeling, and monitoring of interactions between urban systems and their environment.

This is a key issue for the implementation of the COP21 conclusions, but the extreme variability in flows (matter, energy) over wide spatiotemporal scales, makes traditional approaches inadequate. This is particularly true for resilience to extremes, water, and climate change. The establishment of the HM&Co unit was the outcome of rapid development in this field within the eponymous LEESU section. That axis itself originated from MHYM (Meteorology, Hydrology, and Multiplicity of Scales) team, set up in 2003 in a collaboration between École des Ponts ParisTech and Météo-France, and rapidly extended as part of the CNRS’s National Hydrological Research Program. MHYM preceded the profound changes in École des Ponts ParisTech’s supervisory Ministry (and in Météo-France), which have gradually become involved in ecological issues, in particular climate change.

Approach and positioning

HM&Co contributes to the development of the most advanced concepts, methods, and technologies to break down current barriers, e.g.:

► passive and active remote sensing, ubiquitous high-resolution networks;

► experimental sites for nature-based solutions in urban environments;

► cross-scale statistical and stochastic physics;

► multifractal analyses and simulations of complex systems;

► hybrid (deterministic/stochastic) and parsimonious modeling;

► interactions between sensitive time and climate for climate change adaptation and reduction;

► intermittency of renewable energy;

► interactions between physio-environmental and socio-economic components;

► communication issues (in particular participation) in innovation transfer.


A cluster of projects on the Fresnel platform

In the last five years, HM&Co has developed different projects, in particular European projects:

► FP7-”SMARTeST”: smart systems for measuring resilience to urban flooding;

► PST Paris-Est, “Ville Numérique” (digital city) program: distributed hydrological modeling of urbanized catchments (Multi-Hydro digital platform);

► FP7-ITN WAUDIT: intermittency and wind power;

Interreg NWE-RainGain and regional RadX@Id : acquisition and installation of a high-resolution hydro-meteorological radar system, development of an associated platform;

► Climate-KIC Blue Green Dream: multifunctional city planning and management, in particular blue and green infrastructures,  experimental use of the Descartes campus’s blue and green wave.

HM&Co is a participant in Japan’s TOMACS research program and a collaborator in the CASA (USA) and WISE (Koea) projects. HM&Co encouraged École des Ponts ParisTech to take part in Climate-KIC and in the European Wind Energy Academy.
These developments benefited greatly from the long-term partnership with Veolia as part of the Chair in Hydrology for a Resilient City. They led to the development of the multiscale Fresnel observation and modeling platform at the School’s Co-Innovation Lab. Fresnel facilitate synergies between research and innovation, as well as the pursuit of theoretical research, the development of the network of international collaborations, and various aspects of data science.


Visit HM&Co website


The COP21-RainGain conference on “Researchers & Water Managers Preparing Cities for a Changing Climate” (École des Ponts ParisTech, 8-9/06/15) brought together more than 200 participants from every continent, in particular for the last two round tables, with speakers including the heads of very large companies and local authorities, and representatives of the European Commission.





A strange attractor (Mandelbrot set) on a strange algebra (the algebra of quaternions, a number system that extends the complex numbers). The latter is used for stochastic simulations of highly intermittent wind fields, an essential characteristic of wind power.






Installed in 2014 within Cité Descartes, the dual-polarization hydro-meteorological X-band radar system is used to observe and forecast precipitation at the scale of a single street and within a one-minute timeframe. This high resolution will improve our understanding and anticipation of intense rain events and their impact on urban environments.






The blue-green wave is a one-hectare area of green roof located opposite the School. This architectural project, originally conceived for aesthetic purposes, has been converted to a research site. Different variables are measured here (raindrop distribution and speed, water content, temperature, and run-off) in order better to understand the hydrological behavior of this type of infrastructure.





Three disdrometers are currently being tested as part of the development of the Fresnel platform. Installed on the roof of the School building, these optical disdrometers measure the size and falling speed of hydrometeors.






Multi-Hydro is a distributed physical model that has been developed from four open-source software applications already used separately by the scientific community. Its modular structure includes a surface module, a ground module, an infiltration module, and a precipitation module. A final module for modeling green roofs has recently been added to study the benefits of these infrastructures. These scenarios produced by Multi-Hydro are converted into 3-D images with the MH3DV visualization software.