In this blog entry, we look at imagery from the AHI instrument on Himawari-8 with anticipation for GOES-R over the USA as the ABI instrument is very similar to AHI.
We start with the 0.64 micron (visible) band during the daytime hours of 11 November:
North of Japan, we observe a circulation (as depicted below) associated with a surface low with convection to the east and southeast of it along a frontal boundary.
Also note the islands that appear to be blocking the flow (as depicted above).
Next, we look at the 1.6 micron band, which will be one of the new GOES-R bands:
The 1.6 micron band is useful for cloud top phase discrimination. Ice clouds are relatively absorbing at 1.6 microns, therefore glaciated clouds appear darker. As the deeper convective clouds in the vicinity of the circulation and east of it along the front grow in vertical extent, they become darker, which indicates cloud top glaciation associated with vertical growth. This information is in addition to many of the features we already viewed in the visible imagery at 0.64 microns.
Next we’ll look at 2 of the 3 water vapor bands that will be available on GOES, the 7.3 micron low-level tropospheric water vapor band:
and the 7.0 micron mid-level tropospheric water vapor band:
Looking at multiple water vapor bands with GOES-R will allow a better 3-dimensional perspective of the scene of interest.
The weighting function profile for the 7.3 micron band sees a lower layer (in altitude) relative to the 7.0 micron band. The 7.3 micron band still shows some of the low-level clouds we observed in the visible imagery, along with numerous waves. This channel also clearly delineates the upward and downward vertical motions around the surface low circulation. Subsidence is associated with warmer brightness temperatures while lift is associated with cooler brightness temperatures. We also see colder cloud tops being enhanced where convection develops.
The 7.0 micron band depicts even fewer low-level clouds compared to the 7.3 micron band due to the weighting function seeing a higher layer (in altitude), note the brightness temperatures are overall colder. The circulation can still be seen in the imagery, which provides evidence for how deep the circulation is. As you gain experience in viewing circulations with the 3 water vapor channels on GOES-R, you will get a better idea of the intensity and vertical extent of these circulations which can lead to better anticipation of trends observed in the imagery.