The city of Doha in Qatar has suffered severe disruption to transport networks and other services, after receiving almost a year's rainfall in a day on Saturday 20 October 2018. A total of 61.1 mm had fallen by early evening, against a yearly average of 77 mm, leading to many roads being flooded and impassable, and local authorities issuing warnings against people entering the city's many road underpasses due to the risks of becoming trapped. A number of public buildings have been forced to close their doors due to the flooding, including the National Library and the US Embassy.
Flooding in Doha, Qatar, on 20 October 2018. I Love Qatar.
Qatar has been widely reported as having received almost than an average
years rainfall within 24 hours, about 61 mm compared to 75 mm, though
this is slightly misleading as Qatar does not receive any rain some
years, lowering the average rainfall, and what does fall often arrives
in the form of sudden extreme downpours. Flash floods are a common
problem in Qatar (and other
areas with a dry climate) as protracted periods of dry weather can cause
topsoil to dry out completely, making it vulnerable to being blown away
by the wind. When rain does arrive it then falls on exposed bedrock,
which is much less absorbent, triggering flash flooding as the water
escapes over the surface of the ground rather than sinking into it.
These floods wash away more topsoil, making the problem progressively
worse over time.
This extreme weather is thought to be connected with a developing El
Niño weather system, which warms the waters of the Arabian Sea by around. This warming leads to higher rates of seawater
evaporation, i.e. more water entering the atmosphere over the ocean,
which in turn leads to more rainfall on land.
The
El Niño is the warm phase of a long-term climatic oscillation affecting
the southern Pacific, which can influence the climate around the world.
The onset of El Niño conditions is marked by a sharp rise in
temperature and pressure over the southern Indian Ocean, which then
moves eastward over the southern Pacific. This pulls rainfall with it,
leading to higher rainfall over the Pacific and lower rainfall over
South Asia. This reduced rainfall during the already hot and dry summer
leads to soaring temperatures in southern Asia, followed by a rise in
rainfall that often causes flooding in the Americas and sometimes
Africa. Worryingly climatic predictions for the next century suggest
that global warming could lead to more frequent and severe El Niño
conditions, extreme weather conditions a common occurrence.
Movements of air masses and changes in precipitation in an El Niño weather system. Fiona Martin/NOAA.
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