Seviri L1b native Solar zenith angle

[cherif2019-dev]

Please, how to get the solar zenith angle fom the Eumetsat seviri L1b native scene.

[mraspaud]

@ameraner @sjoro ?

[simonrp84]

Hi @cherif2019-dev, for this you need to also use the pyorbital library.
Here's an example script, please note you'll have to adapt the filenames:

from satpy import Scene
from pyorbital import astronomy

# Choose composite
compo = 'natural_color'

# Create scene and load composite
scn = Scene([my_input_nat_file', reader='seviri_l1b_native')
scn.load([compo], upper_right_corner='NE')

# Extract longitudes and latitudes from scene area
lons, lats = scn[compo].attrs['area'].get_lonlats()
sza = astronomy.sun_zenith_angle(scn.start_time, lons, lats)

This will give you the solar zenith angle for each pixel as a numpy array, sza.
You can save the results with:

import numpy as np
import gdal
scn.save_dataset('natural_color', filename=my_rgb_filename, fill_value=0)
rows, cols = sza.shape
ds = gdal.GetDriverByName('GTiff').Create(my_sza_filename, cols, rows, 1, gdal.GDT_Float32)
ds.GetRasterBand(1).WriteArray(sza)
ds = None

[cherif2019-dev]

Thank you so much Simon, Please how can I print the zenith angle for a specific lat long Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 From: Simon Proud<mailto:notifications@github.com> Sent: Tuesday, January 19, 2021 1:05 PM To: pytroll/satpy<mailto:satpy@noreply.github.com> Cc: cherif2019-dev<mailto:charfi008@hotmail.fr>; Mention<mailto:mention@noreply.github.com> Subject: Re: [pytroll/satpy] Seviri L1b native Solar zenith angle (#1510) Hi @cherif2019-dev<https://github.com/cherif2019-dev>, for this you need to also use the pyorbital library. Here's an example script, please note you'll have to adapt the filenames: from satpy import Scene from pyorbital import astronomy # Choose composite compo = 'natural_color' # Create scene and load composite scn = Scene([my_input_nat_file', reader='seviri_l1b_native') scn.load([compo], upper_right_corner='NE') # Extract longitudes and latitudes from scene area lons, lats = scn[compo].attrs['area'].get_lonlats() sza = astronomy.sun_zenith_angle(scn.start_time, lons, lats) This will give you the solar zenith angle for each pixel as a numpy array, sza. You can save the results with: import numpy as np import gdal scn.save_dataset('natural_color', filename=my_rgb_filename, fill_value=0) rows, cols = sza.shape ds = gdal.GetDriverByName('GTiff').Create(my_sza_filename, cols, rows, 1, gdal.GDT_Float32) ds.GetRasterBand(1).WriteArray(sza) ds = None — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#1510 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ANUYAREVMPXRDXLYLLZ6AKDS2VDO7ANCNFSM4WIM6UFA>.

[mraspaud]

You can use the astronomy.sun_zenith_angle function as @simonrp84 showed.

[cherif2019-dev]

Great, thank you very much Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 From: Martin Raspaud<mailto:notifications@github.com> Sent: Tuesday, January 19, 2021 8:42 PM To: pytroll/satpy<mailto:satpy@noreply.github.com> Cc: cherif2019-dev<mailto:charfi008@hotmail.fr>; Mention<mailto:mention@noreply.github.com> Subject: Re: [pytroll/satpy] Seviri L1b native Solar zenith angle (#1510) You can use the astronomy.sun_zenith_angle function as @simonrp84<https://github.com/simonrp84> showed. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#1510 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ANUYARGC2L3ASGOD2D4XFXDS2WZADANCNFSM4WIM6UFA>.

[ameraner]

Thanks @simonrp84 for the nice code snippet! I'll close this issue, @cherif2019-dev feel free to reopen it or add comments if you have further questions.

[cherif2019-dev]

Hi Andrea, Hope you are doing well, I am working on Eumetsat MSG4 data coming from a receiving station, when I tried to use the same data coming from the API(nat file), I found a difference between the two data, Have you an idea from where this difference comes and what is the most reliable source. Thank you. Best Regards, Cherif Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 From: Andrea Meraner<mailto:notifications@github.com> Sent: Friday, January 22, 2021 1:31 PM To: pytroll/satpy<mailto:satpy@noreply.github.com> Cc: cherif2019-dev<mailto:charfi008@hotmail.fr>; Mention<mailto:mention@noreply.github.com> Subject: Re: [pytroll/satpy] Seviri L1b native Solar zenith angle (#1510) Thanks @simonrp84<https://github.com/simonrp84> for the nice code snippet! I'll close this issue, @cherif2019-dev<https://github.com/cherif2019-dev> feel free to reopen it or add comments if you have further questions. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#1510 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ANUYARAMU6TAOLI2CRDUYN3S3FAVTANCNFSM4WIM6UFA>.

[ameraner]

Hi @cherif2019-dev, could you please elaborate on what differences you see? In theory there shouldn't be any.

[cherif2019-dev]

Yes Andrea, please find attached 2 plots: the upper is the T04 plot from the seviri API, the second is the difference between T04 taken by the receiving station(RS) and by api :API-RS Thank you. Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 From: Andrea Meraner<mailto:notifications@github.com> Sent: Monday, February 1, 2021 9:09 PM To: pytroll/satpy<mailto:satpy@noreply.github.com> Cc: cherif2019-dev<mailto:charfi008@hotmail.fr>; Mention<mailto:mention@noreply.github.com> Subject: Re: [pytroll/satpy] Seviri L1b native Solar zenith angle (#1510) Hi @cherif2019-dev<https://github.com/cherif2019-dev>, could you please elaborate on what differences you see? In theory there shouldn't be any. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#1510 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ANUYAREZHR7SFQPT7IUWFTDS43N6FANCNFSM4WIM6UFA>.

[ameraner]

@cherif2019-dev I'm afraid the attachments to the email are not included in the issue reply and are now lost. Could you please post the images as an answer to the issue via the Github webpage?