![\"GOES-12](\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2006\/08\/060829_00_g12_wv_raobs_2.jpg\")
<\/a>GOES-12 Water Vapor (6.5 \u00b5m) image [click to enlarge]<\/p><\/div>GOES-12 “water vapor channel” (6.5 \u00b5m) imagery on 28 August 2006<\/strong><\/a> showed a rather strong moisture gradient in the southcentral US, oriented along a cold frontal boundary. In the color enhancement applied to an AWIPS water vapor image (above)<\/strong><\/em>, dry air is denoted by orange to yellow shades, while increasing moisture is indicated by blue to white shades; thick clouds are enhanced with white to green colors. In particular, note the sharp water vapor gradient between the dry atmosphere at Amarillo, Texas (KAMA)<\/strong><\/em> and the moist atmosphere at Fort Worth, Texas (KFWD)<\/strong><\/em>:<\/p>\n Water vapor imagery shows us the distribution of moisture features within the middle to upper troposphere — but the actual altitude of those dry or moist layers that are being detected can vary quite a bit, depending on the temperature\/moisture profile of the atmosphere. To assess the altitude and depth of the layer from which the radiation is originating, we can calculate the water vapor weighting function<\/strong> based upon the temperature and moisture profile for that region. The CIMSS GOES Realtime Weighting Functions<\/strong><\/a> site allows you to select a particular rawinsonde location to view the corresponding GOES weighting functions for a few of the imager and sounder spectral bands (including the 6.5 \u00b5m imager<\/strong><\/a> water vapor and the 7.4 \u00b5m\/7.0 \u00b5m\/6.5 \u00b5m sounder<\/strong><\/a> water vapor bands). Note on the plots below that in the dry<\/strong><\/em> air at Amarillo TX the peak altitudes of the various imager and sounder water vapor weighting functions is significantly lower<\/strong><\/em> than those in the moist atmosphere just 310 miles (500 km) to the southeast at Fort Worth TX:<\/p>\n