3pm Carslaw 157 Tuesday 20th October Speaker: James Edwards Title: Towards a mathematical understanding of group decision making It is common for individuals belonging to a group to collaborate and reach a collective decisions. Such collaboration need not be through language, for example the actions of decision making individuals may influence those around them, implicitly leading to a decision being made by the group. Examples of this type of individual / group decision making include elections and markets in human society, or foraging and house-hunting in insect society. I will discuss the problem and construct a model to investigate it. Using the model I will show how surprisingly deep insights into group decision making have been found. Speaker: Lewis Mitchell Title: An introduction to data assimilation and ensemble Kalman filtering A fundamental problem in numerical weather prediction is how to estimate the current state of the atmosphere. With the number of observations available generally being orders of magnitude smaller than the model dimension, this is highly non-trivial. Data assimilation is a way of combining imperfect observations of a system with a numerical model to produce an estimate of the state of the system. In this talk, we will introduce one of the state-of-the art tools in data assimilation, the ensemble Kalman filter, and show how it arises from Bayesian estimation and/or variational approaches. We will illustrate its use through some simple climatic models.