Wednesday 24 Sep 2014CliMathNet e-seminar: Transforming weather into changing climate: Mapping the dynamics of the full distribution of temperature and precipitation

Sandra Chapman - University of Warwick

Harrison 209 16:00-17:00

Estimates of how our climate is changing are needed locally in order to inform adaptation planning decisions. This requires quantifying the geographical patterns in changes at specific quantiles in distributions of variables such as daily temperature or precipitation. Here we focus on these local changes and on a method to transform daily observations into patterns of local climate change. We develop a method[1] for analysing local climatic timeseries to assess which quantiles of the local climatic distribution show the greatest and most robust changes. This can also be cast in terms of the change in return times of events. Long tailed distributed variables, such as daily precipitation, have specific challenges in quantifying their extremes. As well as daily observed values, we examine quantities that can be extracted from the data that characterize the changes in time of the likelihood of total daily precipitation above a threshold and of the relative amount of precipitation in those heavy precipitation days. Our method is a simple mathematical deconstruction of how the difference between two observations from two different time periods can be assigned to the combination of natural statistical variability and/or the consequences of secular climate change. This deconstruction facilitates an assessment of how fast different quantiles of precipitation distributions are changing. This involves both determining which quantiles and geographical locations show the greatest change but also, those at which any change is highly uncertain. We demonstrate this approach using E-OBS gridded data[2] timeseries of local daily temperature and precipitation from specific locations across Europe over the last 60 years.

(delivered by live video-link)

[1] S C Chapman, D A Stainforth, N W Watkins, 2013, On Estimating Local Long Term Climate Trends, Phil. Trans. R. Soc. A, 371 20120287; D. A. Stainforth, ,S. C. Chapman, N. W. Watkins, 2013, Mapping climate change in European temperature distributions, Environ. Res. Lett. 8, 034031

[2] Haylock, M.R., N. Hofstra, A.M.G. Klein Tank, E.J. Klok, P.D. Jones and M. New. 2008: A European daily high-resolution gridded dataset of surface temperature and precipitation. J. Geophys. Res (Atmospheres), 113, D20119

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