G
Wind blowing at speeds of 63–75 km/h.
The level surface that the ocean would take in the absence of tides, currents, water density variations and atmospheric effects. It is the surface of reference for astronomical observations and geodetic levelling. See also geopotential.
The earth’s gravitational potential is called the geopotential. A geopotential surface is one whose gravitational forces are equal everywhere. See also geoid.
This approximates the height of a pressure level above mean sea level. Meteorologists often use geopotential heights to analyse the state of the atmosphere at different levels above the ground.
A weather satellite, in a west to east orbit at an altitude of 35 786 km, that maintains the same position over the equator.
If hail larger than 5 cm across is expected, we use the words 'giant hail' in our forecast.
A coating of ice, generally clear and smooth, formed on surfaces by the freezing of supercooled rain, drizzle or fog.
Total short-wave (solar) energy received on a horizontal surface on the ground. It comes direct from the sun and indirectly from elsewhere in the sky, where it can be scattered downwards by clouds, dust particles and so on.
Total amount of electromagnetic energy emitted from the sun that falls on a specified unit horizontal surface.
Irradiance emitted from the sun that falls on a specified unit horizontal surface.
Organisations do not have to provide any water information in the grace period. During this time, an organisation can work out what data it will need to give. This includes historical and ongoing information.
The grace period is 3 months long. It starts when we add an organisation to certain categories of the regulations – person categories A–G and L.
The grace period doesn't apply to:
- water information in Category 5 or 7. Organisations required to give this information will always have longer than 3 months between being added to a person category and when they need to start giving data
- a subcategory of information that the organisation was required to give previously due to being named in another category immediately prior. In this way, the grace period applies only once for each type of information.
Organisations start giving data after the grace period expires. The actual start date depends on whether the data is required daily, weekly, monthly or yearly data. For example, if the grace period ends after the start of a week, the requirement to give weekly information doesn’t apply until the end of the next week.
Wind at the gradient level, about 1 km above the Earth's surface. It's the level most representative of air flow in the lower atmosphere, immediately above the layer affected by surface friction. The gradient level is free of local wind and topographic effects, such as sea breezes and downslope winds.
Natural warming process of the Earth. When the sun's energy reaches the Earth, some is reflected back to space and the rest is absorbed. The absorbed energy warms the Earth's surface, which sends heat energy back toward space as longwave radiation. This is partially trapped by greenhouse gases such as carbon dioxide, methane and water vapor. They radiate the energy in all directions, warming the Earth's surface and atmosphere.
Enhanced greenhouse effect
This term refers to the addition of more heat-trapping gases to the atmosphere. The extra gases are mainly due to the burning of fossil fuels (coal, oil and natural gas). Other sources, such as land clearing, make smaller contributions. Increased concentrations of these gases in the atmosphere are contributing to warming of Earth's surface.
Was used to refer to the primary time standard, but now replaced by Coordinated Universal Time (UTC).
Pattern of radar echoes from fixed objects on the ground, such as buildings or hills.
Sudden increase of wind for a short period, usually a few seconds.
The leading edge of cool air rushing down and out from a thunderstorm cloud. Is usually accompanied by a drop in temperature, a wind shift and a pressure jump.