The Extreme Rainfall Detection System (ERDS), developed and implemented by ITHACA, is a service for the monitoring and forecasting of exceptional rainfall events, with a nearly global geographic coverage.

The Extreme Rainfall Detection System (ERDS), developed and implemented by ITHACA, is a service for the monitoring and forecasting of exceptional rainfall events, with a nearly global geographic coverage.

This system is conceived to be a strategic tool, providing complete, immediate and intuitive information about potential flood events, to be used during the preparedness and response phases of the emergency cycle. Information are accessible through a WebGIS application, developed in a complete Open Source environment, that processes and disseminates warnings in an understandable way also for non-specialized users. Available capabilities include the analysis of near real-time rainfall amount and of forecasted rainfall for different lead times, with the aim to deliver extreme rainfall alerts. The combination of such information with reference data allows the system to generate value-added and event-specific information, such as the list of the affected countries and an estimation of the affected population. Currently the system is one of the tools used by UN World Food Programme (WFP) Emergency Preparedness Unit.

The data used for the near-real time detection of extreme events are mainly based on the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) data, updated on a 3-hour basis. Spatial resolution of TRMM data is 0.25x0.25 lat/lon degrees, between 50° latitude N and 50° latitude S.

This system is also able to provide a longer lead-time alerts (up to 6 days) for heavy rain and floods, using forecast rainfall data, coming from NOAA-GFS (Global Forecast System) deterministic weather prediction models, with 1.0x1.0 lat/lon degrees resolution and worldwide coverage, updated on a 6-hour basis.

Three different alert levels can be visualized (low, moderate and severe), based on specific rainfall intensity threshold, defined as the amount of precipitation for a given duration over a specific climatological area. Concerning real-time rainfall data, two kind of events are considered: short term events, up to 24 hours cumulated rainfall, and medium terms events, up to 1 week cumulated rainfall. In case of forecasted rainfall data, three kind of events are considered: short term events (24 hours), and medium term events both on 72 hours basis and 6 days basis.

In order to facilitate the users in interpreting the alerts, specific information about the impact of heavy rainfall, such as the visualization of the affected countries and the calculation of the potentially affected population, are displayed in a table. Countries currently under alert are listed, ordered from the potentially most affected to the less affected in terms of population; the header of the table allows the sorting of the content. Clicking on a row triggers the maps to zoom over the envelope extent of the active pixels in the chosen country.