## 3 Results
### MISTiC Airborne Instrument Observations from the NASA ER2
Figure 10: Flight path for NASA ER2 (carrying MISTiC airborne instrument) on 4 December 2017 included hyperspectral imaging observations of wind, temperature, and water vapor over the Channel Islands and nearby ocean, and over Vandenberg and Edwards Air Force Bases where radiosondes that provided an independent observation of weather conditions were launched. Figure 12: 4 December 2017 21:30Z radiosonde observation over Edwards AFB and related MISTiC airborne observations for cloud motion vector winds. The radiosonde observations and MISTiC observations provide a consistent and physically sensible picture of the local thermodynamic and wind environment. Figure 13: Spectra for a portion of the radiance image (for channel 112, near 5.068 \(\upmu\)m) near a cloud feature used for cloud-motion-vector observation. The radiance contrast in the image (**left**) has been expanded and shifted to show the higher brightness temperature of the water vapor field which surrounds the cloud. The brightest regions in the image are those without cloud and with low water vapor concentration. The spectra shown (**right**) are 10\(\times\)10 pixel averages in the cloud, moist air, and dry air regions (surface emission-dominated) areas in the image. A cloud (circled in red the figure) was one of several common points identified and located in both of the two images (in this case, given the wind direction and speed, most of the clouds in the field are seen in only one of the two images.) As shown in Figure 10, the ER2 ground track is essentially the same for the two images, but the nadir points of the images are offset in the along-track direction. Figure 14: Clouds (and surrounding low-level water vapor field) under a higher-level water vapor field near Edwards Air Force Base were observed in a set of radiance images. Images from the spectral channels shown are a window channel (71, near 4.919 μm) first with broader radiance range-and then narrowed range to highlight clouds) and images for spectral channels near local spectral radiance minima caused by water vapor absorption and emission, which show a sequence of decreasing average radiance with increasing wavelength, as shown at right in Figure 13. (Channels 64\(\rightarrow\)80\(\rightarrow\)98\(\rightarrow\)115, or 4.894, 4.952, 5.017, and 5.079 μm respectively are shown ). An area of moist air aloft, distinct from a dry area (indicated in the lowest panel on the right), becomes increasingly apparent as spectral channels with increasing water vapor absorption strength are viewed. Figure 15: Radiosonde data during MISTIC Edwards over-flight (**left**) and MISTIC airborne MWIR spectra for areas of dry air and moist air aloft in sweep 114 (**right**). Spectral channels showing the greatest differences between dry and moist areas in Figure 14 are in the longer wavelength portions of the band that are most sensitive to higher-level water vapor. This is consistent with the high dew-point temperature layer aloft shown in the radiosonde data. A cloud motion wind vector is determined from the angular position of the cloud in each of the images along with the instrument's GPS-position and IMU attitude data collected by the instrument during each overpass, and a rough height estimate. The upper two panels in Figure 12 show the wind speed and direction from the lower-altitude portion of the radiosonde profile collected during the MISTiC overpass period.