Author Archives: Stefano Zanardo Ludovico Nicotina Arno G.J. Hilberts Stephen P. Jewson

About Stefano Zanardo Ludovico Nicotina Arno G.J. Hilberts Stephen P. Jewson

Stefano Zanardo, Principal Modeler, RMS

Stefano joined RMS in 2013 and works in the London model development team. He has worked on various RMS flood models and recently led the development of the RiskLink v18 India Flood model.

Prior to RMS, Stefano was a postdoctoral researcher at UC Berkeley and University of Minnesota. He holds a master’s and a PhD in Civil and Environmental Engineering Sciences from the University of Padova.

Ludovico Nicotina, Senior Director - Modeling, RMS

Based in London, Ludovico has worked at RMS since 2011 developing flood models. He is currently within the hazard development team focusing on European flood risk. Before joining RMS, Ludovico held a post-doctoral position at the Laboratory of Eco-hydrology within the École Polytechnique Fédérale de Lausanne from 2009 to 2011 where he conducted research activities on catchment scale modeling of the hydrologic response. He holds a PhD in Hydrology from the Dept. of Civil and Environmental Engineering at the University of Padova, Italy.

Arno Hilberts, Vice President, Model Development, RMS

Arno leads the surge and flood modeling efforts at RMS. Having joined RMS in 2006, he has been involved in a variety of modeling efforts with the U.S. Flood Model being the most recent one. Arno holds an master's and PhD from Wageningen University, The Netherlands, where his research focused on catchment hydrology.

Beside other peer-reviewed publications, he is also a co-author on a Nature publication on the effects of climatic change on flood phenomena in the U.K.

Steve Jewson, Scientific Research Consultant, RMS

Steve has held senior roles across RMS, including Senior Vice President and head of the Climate Risk Modeling Division. In this position he led a group of 60 mathematical modelers responsible for building models examining the wind, hail, surge and flood damage caused by tropical cyclones, extra-tropical cyclones and severe storms.

Prior to taking this role, Steve led the Weather Derivatives Trading Software business unit at RMS. Before joining RMS Steve was an academic, and worked at the universities of Oxford, Monash, Bologna and Reading. He has a PhD from Oxford in climate research, and a degree from Cambridge in Mathematics. Steve is a frequent speaker on weather risk at academic and industry conferences, and has written over 100 scientific articles on topics related to weather and climate. He is the lead author of the definitive book on weather derivative valuation, published by Cambridge University Press.

European Floods and the Relationship with the North Atlantic Oscillation

Stefano Zanardo, Principal Modeler, RMS

Ludovico Nicotina, Senior Director – Modeling, RMS

Arno Hilberts, Vice President, Model Development, RMS

Steve Jewson, Scientific Research Consultant, RMS

The North Atlantic Oscillation (NAO) describes the fluctuations in the difference of atmospheric pressure at sea level between two semi-permanent centers of low and high pressure in the North Atlantic: the Icelandic Low and the Azores High. Fluctuations between these centers control the strength and direction of westerly winds and location of storm tracks across the North Atlantic.

Why is this important? The NAO signal is Europe’s dominant mode of climate variability and correlates highly with European precipitation patterns. Typically, when the NAO is positive – characterized by a higher than average pressure difference between low and high latitudes of the Northern Hemisphere, Northern Europe experiences strong westerly winds. This causes stormier and wetter than usual conditions in Northern Europe, while Southern Europe is drier and colder than usual.

In contrast, when the NAO is negative, Southern Europe experiences westerly winds and the meteorological pattern is somewhat opposite, with Southern Europe being generally wetter than average. The NAO is significantly stronger in winter than in the other seasons, therefore, most studies on the NAO focus on winter months, when the influence of the NAO on surface temperature and precipitation is highest.

When climate patterns result in changing prevailing conditions, such as increased storm activity and rainfall, it is important to understand their effect in relation to the severity of flood events – responsible for significant property damage, business disruption and loss of life in Europe. And there is a need to understand its ongoing impact as the climate and the distribution of exposures change over time.

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