[Tagging] intermittent vs seasonal
johnw at mac.com
Fri Oct 2 02:58:20 UTC 2015
Intermittant= is present irregularly. Larger objects tend to exist for longer than smaller objects. Smaller objects usually appear and reappear more frequently, but this frequency, overall is random.
Seasonal = present only during a certain time or times on the yearly cycle of the earth's journey around the sun. Possibly driven by human choice, but those choices are driven by the seasonal cycle.
Intermittent means randomly. It may be more often in one season or another - but at some point the feature randomly exists or doest exist. This is good for lakes and other "sometimes there, sometimes not" features, as long as one state persists long enough to be noticed /used - An intermittent like or river may be present for days or weeks, perhaps months. The water in a wadi or wash may only be present for a few hours and then dry the rest of the year, so it is not an intermittent river - it uses a tag for the more permanent state (wadi). Natural salt flats (that are nor marshes or covering a mushy liquid underneath) might also be similar.
A seasonal item appears and disappears according to some yearly based cycle (the seasons) - usually due to cyclical and repeating climate changes brought about by the earth's journey around the sun, not geologic (ice ages) or long term climate processes (el nino, global warming etc). A lake with water once every 3 years is intermittent at best. But if it is a lake for 3 months and used as a lake, then it is an intermittent lake.
The salt flats in Death Valley every 10 years or so get a few inches of water to smooth out the salt, and is gone very quickly. It isn't a lake, its a salt flat. Only an extraordinary storm causes it to be wet for very long.
A lake that forms during the rainy season in the summer in Japan, a lake that appears from rain in the desert in winter, a stream from snowmelt runoff in summer, etc are all seasonal. The rest of the year they are usually dry or gone, but during a useful/noticeable amount of time during a repeating time(s) every year (there are two rainy seasons in some places), they exist and are there - every season. (Hence seasonal)
Cyclical =/= seasonal. Seasonal is somehow linked to the 1 year earth-sun cycle, like our caleander and our concept of "the 4 seasons" - where we get the word.
El ninos and other things are linked to other cycles (sunspots, etc) or follow longer climate cycles - but those cycles are not part of nor implied in the word "seasonal".
> On Oct 1, 2015, at 9:58 PM, Mateusz Konieczny <matkoniecz at gmail.com> wrote:
> On Thu, 1 Oct 2015 21:52:11 +1000
> Warin <61sundowner at gmail.com> wrote:
>> It again now says that irregular=regular.
>> Thanks ... black=white too.
>> Tell us .. what tag would you use for a stream that flows randomly ..
>> say on average once every 3 years ?
>> Of course it may not flow for 20 years, then flow 5 times that year.
>> Cannot use intermittent due to your definition... not a yearly
>> (seasonal) flow.
> I thought that "The tag intermittent=yes is used to indicate that a
> waterway (river, stream, etc.) does not have a permanent flow" is quite
> clear but apparently it needs to be simplified. Can somebody help in
> finding more understandable definition?
> Maybe current definition should be changed but clearly at least some
> consider seasonal waterways and water bodies to be intermittent
> (including scientists publishing what seems to be reputable sources).
> Changing definition of established tag requires really strong
> justification that it is a good idea.
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