Future master projects (proposals for the year 2021-2022)

1. The role of circulation in summer floods in Europe

This research project is concerned with the question in how far the recent floods of July 2021 can be attributed to "greenhouse warming", which is the explanation given in the press. This simple explanation states that, because a warmer atmosphere can "hold" more water vapour, extreme precipitation events will occur more frequently. This is obviously not the whole story and is even incorrect. The average precipitable water content in the atmosphere in summer over central Europe is in the order of 30 kg. per sq. metre. Observed precipitation over a 24 hr period on 14 July 2021, for example, was much larger, i.e. about 100 kg. per sq. metre or more over a huge area covering the mountains of the Eifel, Ardennes and Vosges in Germany, Belgium and France. Where did this water come from? It came from the Baltic North Seas under influence of the circulation of a stationary cold core low (cyclone) over Central Germany. Was this event extreme and unique? We think not. Similar events occurred in Central Europe in the summers of 1997 (Czech republic, Poland and Germany), of 2002 (Austria, Czech republic and Germany), August 2005, May and June 2010 and August 2016, etc. In this research project you will study and compare the meteorology of past flood-events in summer over Central Europe and try to identify, using ERA-reanalysis data, the role of "greenhouse warming" in these events relative to the role of circulation and the associated moisture flux convergence, which must have played a decisive role in causing the floods of July 2021.

2. Climate Change in Early Spring: the Role of the Hadley Circulation

In spring the intense winter Hadley cell weakens and becomes a so-called summer cell. This transition typically occurs in April in the Northern Hemisphere. Is this transition occurring later in spring this century than before? If so, this may explain the more intense subsiding motion over Western Europe in the middle troposphere in April in this century. This may also explain the increase of sunshine duration and much higher temperatures in April in Western Europe this century. In this project you will investigate the spring-transition of the Hadley cell, using ERA-reanalysis data, and try to explain the spectacular change of April climate in the Netherlands and neighbouring countries in the past 20 years.

3. The meridional residual circulation and the Annular Mode (NAM)

This project investigates the relation between the meridional residual circulation of mass and the Annular Mode, both in Northern and in the Southern Hemisphere.