Plotting: McIDAS and sort of natural colour images

I use a range of RGB products – most of these are pretty standard  in the meteorology with satellite community.  The information in red / green and blue is chosen to maximise the geophysical information avaliable.

But sometimes what we want is a nice image that looks similar to what a human eye might see from space. On most meteorological satellites we don’t have red, green and blue. The most common combination I use is red = 1.6 micron, green = 0.8 micron and blue = 0.6 micron. Which gives brownish desserts, dark seas, green vegetation, white low clouds and cyan ice clouds.

Simon Proud @simon_rp84  suggests  using: red =0.6 micron x 2.2 + 0.8 micron x 2.5 + 1.6 micron x 1.3,  green =0.8 micron and , blue = 0.6 micron.  This gives whiter shades for clouds. Like this:

test

In McIdas other RGBs can be made. Here is how I implemented Simon’s recipe.  Here is my Jython code (Tools -> Formulas – Jython library – add to local library). Here is the jython:

# Simon's more natural colour RGB
#r=0.6u*2.2+0.8u*2.5+1.6u*1.3, 
#g=0.8u, 
#b=0.6u 
# Natural colours, linear enhancement btw minrefl-maxrefllower-upper limit
# units: % Refl
# minrefl	lower limit of reflectivity range
# maxrefl	upper limit of reflectivity range
def SP_NCOL_RGB(ch06,ch08,ch16):
 min=0
 max1=95*2.2+100*2.5+100*1.3
 max2=95
 max3=95
 red = rescale((ch06*2.2)+(ch08*2.5)+(ch16*1.3),min,max1,0,255)
 grn = rescale(ch08,min,max2,0,255)
 blu = rescale(ch06,min,max3,0,255)
 return combineRGB(red,grn,blu)

Note that spaces matter to python

Clipboard01

and corresponding formula (add as a formula)

SP_NCOL_RGB(D1[label=VIS0.6,pattern=0\.6],D2[label=VIS0.8,pattern=0\.8],D3[label=NIR1.6,pattern=1\.6])

I have the formula set to only display an RGB composite.

Clipboard01

Thanks Simon for the recipe.

 

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Plotting: McIDAS V and AVHRR

 

Get the data

I have two ways to get AVHRR data (that I use). For archive I use NOAA CLASS archive http://www.class.ncdc.noaa.gov/ and order the FRAC 1 km data. CLASS has Metop and NOAA AVHRR imagery. FRAC = Full resolution area coverage. Within CLASS you can search for a geographical area and a specific range of time.

In house we have access to an ADDE server with the FRAC data and Lat/Long navigation for the last 5 days – which is a very nice thing to have.

I have not been able to plot the EUMETCast delivered data directly. It is in channel EPS-10.

The class data is in the NOAA AVHRR level 1.5 format. To make this available to McIDAS-V you will need to set up a local ADDE server.  Tools -> manage ADDE datasets ->  Local Data tab. Set the format to NOAA AVHRR Level 1.5.

Plot the data

For RGB images I use the formula -> create 3 colour image (auto scale)  with  1.6 micron on red, 0.8 micron on green and 0.6 micron in blue. (This is the natural colour RGB recommendation) ice clouds show up in cyan.  The example below is from 2014-07- 09 0930Z (Metop-A).

Europe example - 2014-07-09 0930Z

For single channel IR I use this colour table. (import the xml from the colour table screen) with a range of 190 K to 330 K.