![](\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/images\/2023\/01\/230110_goes18_waterVapor_infrared_HI_anim.gif\")
<\/a>GOES-18 Upper-level Water Vapor (6.2 \u00b5m, upper left), Mid-level Water Vapor (6.9 \u00b5m, upper right), Lower-level Water Vapor (7.3 \u00b5m, lower left) and “Clean” Infrared Window (10.3 \u00b5m, lower right) [click to play animated GIF | MP4<\/strong><\/a>]<\/p><\/div>GOES-18 (GOES-West)<\/em> Upper-level Water Vapor (6.2 \u00b5m<\/strong><\/a>), Mid-level Water Vapor (6.9 \u00b5m<\/strong><\/a>), Lower-level Water Vapor (7.3 \u00b5m<\/strong><\/a>) and “Clean” Infrared Window (10.3 \u00b5m<\/strong><\/a>) images\u00a0(above)<\/strong><\/em> revealed the diurnal cycle of nighttime cooling and daytime warming at the summits of Mauna Kea<\/strong><\/a>\u00a0and\u00a0Mauna Loa<\/strong><\/a> on the Big Island of Hawai\u2019i on 10 January 2023. In addition, a hot thermal signature (darker red to black pixels) was evident in the 10.3 \u00b5m imagery due to ongoing volcanic activity at Kilauea. This case is another example which helps to underscore the fact that Water Vapor spectral bands are essentially Infrared<\/strong> bands, which \u2014 in the absence of clouds \u2014 essentially sense the mean temperature of a layer\u00a0<\/em>(or layers) of moisture within the troposphere.<\/p>\n The presence of very dry air within most of the middle\/upper troposphere over Hawai\u2019i on 10 January had the effect of shifting the water vapor weighting functions<\/strong><\/a>\u00a0to\u00a0lower<\/strong>\u00a0altitudes, as seen on plots for the 3\u00a0ABI<\/strong><\/a> Water Vapor bands calculated using 12 UTC rawinsonde data from Hilo PHTO (below)<\/strong><\/em>. This allowed thermal radiation from the higher terrain to pass upward — with minimal attenuation — through what little high-altitude moisture was present and reach the 7.3 \u00b5m \/ 6.9 \u00b5m \/ 6.2 \u00b5m detectors on GOES-18.<\/p>\n