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British efforts to find a new label for distinctive layered clouds that form "gravity waves" may not be necessary in New Zealand, says MetService spokesman Bob McDavitt.
Meteorologists in Britain are making a bid to have a new classification created for the cloud formation, which the Royal Meteorological Society wants to have named "asperatus" after the Latin word for rough.
The scientists want the label officially added to the international scheme used by forecasters to identify clouds.
New Zealand meteorologists normally describe the cloud pattern as altocumulus lentincularis and one formation of mountain wave clouds is commonly known the "northwest arch" in regions such as Canterbury, McDavitt said.
"So maybe no new name is required for such clouds," he said. "There is a whole zoo of cloud forms and changing shapes that occur".
McDavitt said there were already 10 or so varieties of cloud, and another 15 "species".
The cloud formations at the centre of the debate have underbellies like a rough sea. They are typical of clouds that form when there are two layers of different density in the air, one sitting on the other.
"The moister, cooler higher layer has cloud in it and the less moist layer is cloud-free," he said.
"The boundary between these layers occasionally kicks up, dip again because of gravity".
The northwest arch seen in Canterbury was usually a mix of lenticularis cloud at various levels - altocumulus altostratus and cirrostratus.
McDavitt said the asperatus label could be used to describe the undulations on the underbelly of the cloud but the current cloud classification system was sufficient to describe New Zealand clouds.
If the World Meteorological Organisation (WMO) decided to add asperatus as a new species of cloud, "then we will probably use it to describe the times when the underbellies of altocumulus lenticularis clouds can be seen to change shape and "undulate" over a period of a time."
