From the extensive database of www.tutiempo.net I calculated the number of thunderstorm days for numerous places in Romania. After that I drew a map to see the spatial distribution:
Average annual number of thunderstorm days for Romania, 1991-2010. Iso-lines: pink=38, red=34, yellow=30, green=26 and blue=22.
It's clear that the central part of Transylvania and a belt just south of the southern Carpathian mountains (Transylvanian Alps) receive most thunderstorm-days, with 35 to 40 on average. This is among the highest in Europe. Other area's in Europe with comparable numbers of thunderstorm days are the southern French Alps, the Po River Valley, the Croatian coastal areas and western Bulgaria.
An other conclusion is that the number of thunderstorms decreases in east and northeasterly direction. One cause could be the dryer/more arid conditions in the east/northeast. The town of Sulina for example, with 15 annual thunderstorm days, gets only 400-450 mm of precipitation per year.
Other interesting observation is the local maximum about 20 kilometers inland from the Black Sea coast. Here thunderstorm development on the seabreeze-front is a plausible explanation for this local maximum.
For the decrease in number near the southern border I have no good explanation. On the Bulgarian side of the river Danube, the annual number is comparable to that of extreme southern Romania. However, further to the southwest it increases dramatically to around 40 near Sofia, Bulgaria.
Geen opmerkingen:
Een reactie posten