Satellite weather images

[Karthik Subramanian]

Context: I'm interested in understanding the information conveyed by satellite weather images,

and correlating this with local weather conditions.

My interest is twofold - firstly, to choose observing locations, and secondly, to be able to make

a go/no-go decision for a given observing location.

I'm looking at the images from the IMD website: http://satellite.imd.gov.in/insat.htm 

My current understanding of satellite weather imagery is this:

+ Visible-spectrum satellite images are pretty much a daytime snapshot of clouds from above.

   Clouds show up as bright white, and clear regions show up as black.

   

   Example: http://satellite.imd.gov.in/img/3Dasiasec_vis.jpg

   

+ In Water Vapour spectrum (essentially, IR wavelengths that are reflected by water vapour)

   images, regions of the atmosphere with high moisture content show up as bright white,

   and low moisture content shows up as dark. 

   

   Example: http://satellite.imd.gov.in/img/3Dasiasec_wv.jpg

+ In both the images above, there is a colour scale at the bottom of the picture. I'm not sure

   what the numbers mean, however. I assumed that areas in both the visible and IR images

   that show up as black tend to have good observing weather.

+ I do not know how to interpret the other kinds of images you get off the IMD Insat page -

   the SWIR, MIR, IR-1, IR-2 and colour composite images.

+ The RAPID link at the top of the IMD Insat page seems to let you play animations of weather

    images collected over a period of time, with pretty good (geographic) resolution. I do not

    understand the different kinds of images (say, WV-Count, WV-BT, WV-Rad), and neither do

    I know how to interpret them. I'm guessing that this would be the one thing to look at to

    make observing weather decisions, since it lets you zoom in to a smaller geographical area

    than the other images.

If someone could shed light (!) on this topic - and hopefully correct gaps in my understanding

above, that would be great. In addition, pointers to any reading material on this topic would also

be highly appreciated.

Best,

K.

[Srikanth Yadake]

I have been following IMD site(the page which you have mentioned) for long time now, but I could not co relate the images from either Visible/IR to clear skies in my area/city. Even I would want to know about this. 

One more interesting site is this https://earth.nullschool.net/#current/wind/surface/level/orthographic=-280.72,17.75,1024/loc=77.247,14.234

[itspo...@gmail.com]

One more interesting site

 EOSDIS Worldview

Cheers

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[Arun Venkataswamy]

Hi Karthik,

On Wed, Jan 11, 2017 at 10:45 AM, Karthik Subramanian <karthi...@gmail.com> wrote:

If someone could shed light (!) on this topic - and hopefully correct gaps in my understanding

above, that would be great. In addition, pointers to any reading material on this topic would also

be highly appreciated.

Satellite images are released by Mosdac every hour and they are good. But I don't think their resolution is enough to do a localised inference for an observing site. Ofcourse you can find out about widespread cloud coverage over the area.

Global Forecasting System (GFS) data is released for every point on earth with a resolution of half a degree resolution of latitude and longitude. Directly inferring from this numerical data is tough but there are websites which convert them into meteograms. These meteograms show prediction of cloud coverage too.

For Chennai:

http://www.monsoondata.org/wx/chengfs.png

For other cities you can find it here:

http://www.monsoondata.org/wx2/meteogram2.html 

Regards,

Arun 

http://wondroussky.blogspot.in/ 

"கற்றது கைமண் அளவு, கல்லாதது உலகளவு" - ஔவையார்
Known is a drop, Unknown is an ocean

[Suresh Mohan Neelmegh]

I don't know if Dhinakar Rajaram is a member of BAS , he is the best I know

Suresh

Sent from my iPhone

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[Karthik Subramanian]

On Thursday, 12 January 2017 12:14:47 UTC+5:30, drsureshmohan wrote:

I don't know if Dhinakar Rajaram is a member of BAS , he is the best I know

Suresh

Thanks, Doc!

How does one get in touch with him off-list?

K. 

[keerthi kiran]

Hi Doc,

But he always predicts rain ;)

We need some optimistic forecasts :D

Regards,

Keerthi

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[Suresh Mohan Neelmegh]

Then trust my predictions !

Sent from my iPhone

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