How to create or adapt an RGB scheme

Introduction

RGB images can be composed in many different ways. To avoid ambiguity and incorrect interpretations, WMO and EUMETSAT work to standardize the RGB images used by weather forecasters. Experts develop optimized methods to create RGB images that provide high quality visual information about specific features. The use of these standard RGBs helps meteorologists easily understand each other. The standard RGBs have schemes, or recipes, describing how to create them.

A new imager usually has:

• New channels providing new information content, measuring in spectral regions not measured by the previous imager.
• Similar channels to those of the previous imager. These channels might be different in some degree (shifted central wavelengths, different response functions), but their information contents are similar.

Adaptation of successful RGB schemes to the new imager are feasible. Experts also try to find new RGB schemes (using the new channels) to benefit from the new information content, in order to fill the gaps in our knowledge about clouds, the atmosphere or the surface. The best new and adapted RGB schemes will be standardized later on; it is important not to standardize too many RGB schemes. RGBs with the same information content, but with different appearances, should be avoided.

This document summarizes how to create a new RGB scheme and how to adapt an existing RGB for a new imager.