Combine evidence at the right scale

At the subsatellite point, the published nominal sampling is 0.5 kilometers for AHI Band 3 and 2 kilometers for many infrared bands. The location qualifier matters: the geometry changes across the Earth disc. Enlarging a web image does not restore detail that the instrument did not sample.

As an original geometry exercise, compare ideal square footprints with sides of 0.5 and 2 kilometers. The larger side is four times as long and the area is sixteen times as large. This is a scale comparison, not a guarantee that every real footprint is square or that every 0.5-kilometer feature can be cleanly resolved.

The Himawari 3 image shows Cyclone Ivy on February 27, 1989. It uses VISSR observations processed by Chiba University and colorized by Nino Marakot. Its broad cloud structure is visible, along with texture in the processed image. Those display features should not be assigned a precise physical meaning without the underlying product information.

A single frame has no measured movement between timestamps. It also does not directly supply a surface wind speed or rain total. Its value here is an identified historical observation with its processing credit retained. Comparing it to a later image requires attention to different instruments and products, not just how attractive or sharp each looks.

Imagine assessing whether a cloud system is strengthening near a coast. A time sequence can show changes in cloud organization; additional spectral information can help characterize the cloud; surface observations can describe conditions at their locations. A forecast model then addresses future evolution using a broader set of information. These contributions have different spatial and temporal scales.

A defensible explanation states the observation time, instrument, product, scale and inference. For example: this identified cloud pattern changed between these frames, while this nearby gauge recorded rain over this interval. That is more useful than claiming one dramatic image proves every aspect of the weather. The next course can follow how other Earth-observation programs combine different sensors and coverage patterns.