Early Warning of Drought: Climate Watch Advisories for the WMO RA VI Region

The German Meteorological Service (Deutscher Wetterdienst, DWD) leads the climate monitoring activities within the Regional Climate Centre Network of the WMO Regional Association (RA) VI Region (Europe). One of its mandatory functions is the issuance of Climate Watch Advisories (CWAs). These are early warning advisories on weather and climate events in the extended-range-forecast (2-4 weeks), such as heat and cold waves, heavy precipitation periods and drought, all within Europe / RA VI. The advisories are based on expert assessments of climate monitoring and extended forecast results. Users of these advisories are National Meteorological and Hydrological services (NMHSs) in the RA VI Region. It is up to the NMHSs to turn CWAs into tailored national advisories or warnings to their end users.

Drought belongs to the types of events, which are very challenging for early warning. This is due to the various categories of drought (meteorological, hydrological and agricultural drought), its slow onset, its variability in duration in the atmosphere and at various soil depths, its dependency on various parameters (precipitation, temperature, evaporation, soil moisture, heterogenous geographical climate conditions, seasonal cycle), and its variety in impacts in various economical sectors (health, agriculture, energy, forest fires etc.) and different levels of vulnerability from country to country. 

Given the complexity of the drought phenomenon, an early warning approach for Climate Watch Advisories has been chosen, which has some restrictions. The advisories refer to meteorological drought, while hydrological and agricultural aspects are considered in national advisories. For meteorological drought, precipitation totals, anomalies and percentiles seem to be the most useful variables, rather than drought indices. Since the time scale of Climate Watch Advisories is subseasonal, precipitation variability of the past 30 days is taken from monitoring products and for the next 2-4 weeks from extended forecast products.

For the future, the subjective assessment (expert decision after having looked at all available products) will be replaced by an objective approach (fixed criteria are used as input for an automatic process).

In this presentation, some examples of drought advisories will be analysed and the concept of the objective approach will be described.