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| Screenshot from Earth Null School |
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| Screenshot from Earth Null School |
And when you click on 'earth' you get this panel of controls.
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| Screenshot from Earth Null School Need to click earth to get this view |
And the residuals of my Chinese are good enough that I know the link on the lower right is to a Japanese version.
Go have a look. Play with it yourself. Watch the wind currents flow. The water currents don't move quickly enough to see. At least I didn't see them moving. The middle image is "Projection CE" and when I tried to look that up, I kept getting civil engineering. But when I got the URL it says conic equidistant. ArcGis defines this as:
If you want to know more go to the ArcGis link."This conic projection can be based on one or two standard parallels. As its name implies, all circular parallels are spaced evenly along the meridians. This is true whether one or two parallels are used as the standards."
My friend B knows how to distract me by sending links like this.
[UPDATE Feb. 24, 2014 - Retired aviation technology professor Bill Butler commented here and sent me a longer email which is now a follow up guest post here. It goes into more detail on Mercator maps and Lambert's maps.]
I've been using this with other meterological data to follow the weather systems in the Atlantic, particularly its land-fall on GB (the jetstream view is mind-boggling). Anyway, it's supercomputer modeling to allow near-time predictions in established refresh intervals every day. A bit of projection about projections, really. So good I keep a link in my favourites bar.
ReplyDeleteMorning, Steve,
ReplyDeleteI don't know how much you've played with the controls, but what you've posted is the chart for the 1000 hPa gradient, that is a prediction of winds near the earth's surface.
It isn't actually "real-time", but a compilation of forecast winds plotted at many, many locations. Even the "now" window is a picture of the winds which were forecast to occur now. By clicking on the time bar you can look ahead about four days.
It uses the standard measure of atmospheric pressure (for nerds, not us civilians), i.e.hectopascals. Rather than express altitude in feet, meters, etc. They use hectopascals as a rough equivalent. Not exact, because as high and low pressure areas circulate, the altitude of any specific pressure shifts up and down, but it provides a useful number. the 1000hPa charts show conditions near the surface (the standard atmospheric pressure at the surface is 1013.25hPa). The 500hPa chart would show winds somewhere around 18,000 feet. 300hPa shows the winter jet stream best at around 30,000 feet. (...and it's much more colorful!)
I assume you've already figured out that it is dragable, rotates and zooms.
Next message about projections. Ad summum!
Bill Butler
Ashland, Oregon
Here's a useful tool:
http://www.srh.noaa.gov/epz/?n=wxcalc_pressurealtitude
The problem of projecting a spherical earth onto a flat surface for navigational purposes has vexed man for many centuries. The advent of modern computer graphics has made it possible for us to achieve near-versimilitude, as in the "orthographic" presentation on your wind model. Your computer allows you to "rotate" the sphere, looking over the edge and 'round the back of your flat earth, keeping things in proper relation.
ReplyDeleteHitherto, the most common projection was the 16th Century Mercator, which we all knew from the big wall map on the front wall of our elementary school. Mercator's projection had huge distortions at the poles (the north pole, which is infinitely small in reality is the same size as the equator according to Mercator), but since everyone lived around 30 to 50 degrees north, this was manageable, and the errors were not significant over the short distances people generally travelled.
The CE projection (the most common variety is the Lambert conformal conic) is used over short distances, or more accurately over a series of maps covering short distances, by assuming that only the area near one parallel of latitude, or between two parallels has been flattened, ignoring the minor distortions thus created. I have an hour of powerpoint illustrating this process I'd be glad to show you next time you're in Oregon, but I couldn't figure out how to attach it to this message.
Bill Butler
Professor of Aviation Technology (ret.)
Here's another toy for you:
ReplyDeletehttp://www.gcmap.com/mapui?P=panc-lfpo
Bill, love hearing from you, and one day we'll surprise you and show up in Ashland. Maps are a great metaphor for many things and so I'm always interested in seeing the world differently. Thanks for the added info.
ReplyDeleteSteve,
DeleteIs there a way to insert a picture (jpg) in a reply? If not, send me an email: billbashland@charter.net and I'll send a couple illustrations that make sense of the conical projection.
Bill
May i know what is tpw , tcw and other terms?
ReplyDeleteSorry, I don't understand your question. I searched the page for tpw and tcw and the only time they showed up was in your question.
DeleteWhen we click on " EARTH" , We get pannel of controls. In overlay section, there are abbreviations like temp for temperature. Rh for relative humidity. Etc. In the same section these two terms are appearing. TPW and TCW.
ReplyDeleteOK, now. When I put my cursor on the letters a little pop up window gives the full name - TPW = Total Precipitible Water; TCW = Total Cloud Water.
DeleteThanks.
ReplyDelete