Hydrometeorological extremes in a future climate

Are extremes intensified in a warming climate?

Vertical-Rainfall
Cross-section of precipitation from a sequence of convective clouds as observed from a vertical pointing ground based radar.

Isn’t rain fascinating?! Sometimes it falls as a light refreshing mist and other times as an all drenching waterfall. The formation of rainfall is affected by all scales, from the smallest microphysical processes to the large scale atmospheric circulation. Further, it is in itself affecting these processes, which makes it a very intricate phenomenon to study. In this research field, we study two main topics: (i) the use of remote sensing to improve assessment of rainfall at both the global scale for hydrological modeling and at small kilometer scale to study extreme events, and (ii) changes in hydrometeorological extremes at local and global scale.

Remote analysis for better understanding of precipitation

Remote analysis of land and satellite radar precipitation results in far better spatial coverage and often higher resolution than traditional station observations. Long data series with improved quality in different parts of the world means new opportunities to for mapping rainfall quantities, but also to study individual rainfall systems in more detail. Radar and satellite data studies can thereby provide a deeper understanding of precipitation extremes and how they are affected by external conditions such as changed temperature, humidity or circulation patterns.

Hydrometeorological extremes on a global scale

The hydrological model HYPE has recently developed into a global model, WW-HYPE. Linked with tools for handling bias adjustment and ensemble simulations of climate projections WW-HYPE provides a unique opportunity to explore hydrometeorological extremes, as well as to evaluate uncertainties in climate projections. Within this topic we also investigate the impact of natural variability, bias adjustment and process description on the interface between meteorology and hydrology, for future climate projections.

Research and development questions

How to combine multiple observations to improve rainfall products?
Remote sensing provides higher spatial coverage at high time and space resolution. The HIPRAD method will be further developed to handle multiple data sources, such as ground and space based radar measurements as well as gauge and other ground based data. Cloud observations are also explored.

Can we acquire fundamental principles of the intensification of rainfall extremes in present data?
Studies of high resolution rainfall data and tracking of rainfall events gives a more in-depth understanding of cloud systems and how they evolve in space and time.  We study, for example, the interaction between clouds and its relationship to invigorated extreme events.

How will hydrological extremes change in the future?
The water cycle is intensifying in most parts of the world, and we study how this affects drought and flood events. We also address what can be learnt from climate projections, and what are the limits due to uncertainties arising from natural variability and bias adjustment techniques.

Our core publications in this Scientific focus

Berg, P.; Donnelly, C. & Gustafsson, D. Near-real-time adjusted reanalysis forcing data for hydrology, Hydrology and Earth System Sciences, Copernicus GmbH, 2018, 22, 989-1000, doi.org/10.5194/hess-22-989-2018

Berg, P.; Norin, L. & Olsson, J. Creation of a high resolution precipitation data set by merging gridded gauge data and radar observations for Sweden, Journal of Hydrology, 2016, 541, 6-13, doi.org/10.1016/j.jhydrol.2015.11.031

Berg, P.; Haerter, J. O.; THejll, P.; Piani, C.; Hagemann, S. & Christensen, J. H. Seasonal characteristics of the relationship between daily precipitation intensity and surface temperature, Journal of Geophysical Research, 2009, 114, 9 PP. doi.org/10.1029/2009JD012008

Berg, P.; Moseley, C. & Haerter, J. Strong increase in convective precipitation in response to higher temperatures, Nature Geosci., 2013, 6(3), 181-185, doi.org/10.1038/ngeo1731

Moseley, C.; Berg, P. & Haerter, J. O. Probing the convection life-cycle by iterative rain cell tracking, Journal of Geophysical Research, 2013, 118, 13361-13370, doi.org/10.1002/2013JD020868

Moseley, C.; Hohenegger, C.; Berg, P. & Haerter, J. Convective extremes driven by cloud-cloud interaction, Nature Geoscience, 2016, 9, 748-752, doi.org/10.1038/ngeo2789