Storm Clouds Over Axios River Delta, Greece

p>Photographer: Sofia Goudetsidou
Summary Authosr: Sofia Goudetsidou; Jim Foster; Stu Witmer

Arcus clouds (roll clouds and shelf clouds) can occur over land or sea. This view of an arcus cloud was taken as it moved overhead in advance of a weather front over the Axios River estuary (also known as the Vardar River) in Thessaloniki, Greece. From this angle, it's hard to tell if the cloud is a shelf cloud (attached to a parent cloud) or a roll cloud (unattached). This river delta is an important habitat for waterbirds such as the Black-winged Stilt and the Mediterranean Gull. Just 7.5 miles (12 km) from the center of the major city of Thessolonika the esturay faces many threats including rubbish dumping, industrial discharge and urban expansion. Photo taken June 22, 2009.

Photo details: Camera Maker: Canon; Camera Model: Canon EOS 5D Mark II; Focal Length: 24.0mm; Aperture: f/13.0; Exposure Time: 0.020 s (1/50); ISO equiv: 160; Exposure Bias: +0.33 EV; Metering Mode: Matrix; Exposure: shutter priority ; (semi-auto); White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal.