Intensive precipitation and urban hydrological forecasts.


Background and content

Most hydrological processes are strongly influenced by heavy precipitation.

Thus accurate precipitation data are a prerequisite for good hydrological modelling, at all scales, which is however difficult to fulfil.

Different types of observations (gagues, radar, gridded products, etc.) as well as forecasts (determinsistic, ensembles, etc.) with different time horizon (hours, days, weeks, seasons, decades, century) have different strengths and weaknesses which contribute to uncertainties and errors.

There is a need for better understanding of how heavy precipitation is represented in observations and forecasts (including climate projections) and improved methods for merging different sources into integrated products. This will be achieved by:

  1. analyses of observations and forecasts, with focus on high resolutions in time and space and hydrological consequences of heavy precipitation,
  2. method development for data integration.


Background and content

Hydrological simulation and forecasting at SMHI is currently based on a daily time step, which limits the possibility to describe sudden and short-lived flow changes. This limitation is most obvious in small, steep catchments with thin soils and not least in cities with a large fraction of impervious surface.

In S-HYPE, the spatial resolution is sufficient for describing these types of catchments but there is a need for development towards shorter time steps, down to 1 h (maybe even shorter in the future?).                      

There is also a need to develop

HYPE’s descriptions of land use and flow dynamics in urban environments. This will be achieved by:

  1. producing high-resolution P, T, Q data bases
  2. evaluate high-resolution S-HYPE simulations with focus on urban catchments
  3. develop the support for urban areas in set-up and process descriptions.