Using ECMWF's Forecasts (UEF2021)

Sand and Dust Storms are recognized as hazardous meteorological events impacting the society in many ways. WMO has established Regional nodes for their forecasting and knowledge share. While their products (e.g. SDS-WAS in Barcelona) provide a general view of the expected dust outbreaks towards Bulgaria, the ECMWF products give a possibility for detailed analysis of the synoptic processes and thus enhance our capabilities for more accurate forecast. We use “direct” ECMWF products (e.g. charts for wind, temperature and geopotential at different pressure levels), as well as “indirect” products for aerosol forecasts available at Copernicus Atmosphere Monitoring Service, implemented by ECMWF.
We discuss here two intense dust events, occurred in March and May 2020 in Bulgaria. In general, the Saharan dust outbreaks towards the Balkans increase in spring as a result of the enhanced atmospheric dynamic. In the first case study (25-31.03.20) the air masses with Saharan dust approach the country from southwest followed by south-east flow. In the middle of the period, however, in northern Bulgaria there is a strong north-easterly outbreak carrying dust from the Aralkum desert. In the second case (13-17.05.2020) the Saharan Dust advection was associated with strong south-westerly flow and anomalies in the temperature (daily max 29 – 37.7°C). The synoptic analysis indicates a favorable strong jet stream over the Mediterranean leading to significant dust spread also over Bulgaria. We show the impact on surface concentrations of particulate matter (PM10). In both cases the daily mean PM10 reached values of about 80-100 ug/m3 at high mountain peaks. The increased background concentrations led also to high PM10 in many urban areas – up to 4 times higher than the daily limit of 50 ug/m3.
At NIMH we notice a tendency for increased number of dust events in the last years. A protocol describing the most frequent synoptic pattern and its main characteristics favorable for intense events are thus useful for the operational forecasts.