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Displaying 90 of about 768 resultsFreezing rain is rain where the temperature of the water droplets is below 0°C. Drops of supercooled rain may freeze on impact with the ground, in-flight aircraft or other objects (WMO, 2017).
A freeze is an air temperature equal to or less than the freezing point of water (D °C) (adapted from WMO, 1992).
A snow storm is a meteorological disturbance giving rise to a heavy fall of snow, often accompanied by strong winds (WMO, 1992).
An extra-tropical cyclone is a low-pressure system which develops in latitudes outside the tropics (WMO, 1992).
A depression or cyclone is a region of the atmosphere in which the pressures are lower than those of the surrounding region at the same level (WMO, 1992).
A storm surge reflects the difference between the actual water level under the influence of a meteorological disturbance (storm tide) and the level which would have occurred in the absence of the meteorological disturbance (i.e., astronomical tide) (WMO, 2008, 2011, 2017).
Seiches are sea-level oscillations at the resonant frequency of enclosed bodies of water (WMO, 2011).
Polluted air is air containing dust, smoke, micro-organisms or gases different from those from which it would normally be composed (WMO, 1992).Alternative definition: Polluted air is air which contains gases and particles emitted to the atmosphere by a variety of human activities and natural sources, or formed in the atmosphere, that at critical levels…
A ‘glacial lake outburst flood’ is a phrase used to describe a sudden release of a significant amount of water retained in a glacial lake, irrespective of the cause (Emmer, 2017).
A snowmelt flood is a significant flood rise in a river caused by the melting of snowpack accumulated during the winter (WMO, 2012).
Coastal flooding is most frequently the result of storm surges and high winds coinciding with high tides. The surge itself is the result of the raising of sea levels due to low atmospheric pressure. In particular configurations, such as major estuaries or confined sea areas, the piling up of water is amplified by a combination of the shallowing of the s…
A thunderstorm is defined as one or more sudden electrical discharges, manifested by a flash of light (lightning) and a sharp or rumbling sound (thunder) (WMO, no date).
A submarine landslide is a downslope movement of sediment or rock under the effect of gravity, which occurs when the stresses acting downslope exceed the available strength of the sediment on the slope (Lee et al., 2007).
Subsidence is a lowering or collapse of the ground, caused by various factors, including groundwater lowering, sub-surface mining or tunnelling, consolidation, sinkholes, or changes in moisture content in expansive soils. Shrink-swell is the term applied to the behaviour of expansive soils, which are a group of soils that exhibit volumetric change in re…
Induced seismic ground shaking comprises non-tectonic (i.e., nonnatural) earthquakes which result from human activities that alter the stresses and strains on the Earth’s crust. Most induced seismicity is of a low magnitude and higher frequency than larger magnitude events with longer wavelengths and lower frequencies (USGS, 2016).