## 3 Results
### MISTiC Airborne Instrument Observations from the NASA ER2
The cloud-feature-based wind speed and direction obtained from the data in Figure 11 are indicated in red in Figure 12. These wind-speed and wind angle estimates agree to within 2.5 m/s and five degrees azimuth, if the cloud lies just below the pronounced temperature inversion near 2500 m (AGL) apparent in the lower-left panel of Figure 10.0 This height for the cloud is physically sensible, and also consistent with the cloud top radiance range (corrected for cloud reflectance at that wavelength) observed by MISTiC in this spectral window, as shown in Figure 13 and indicated by the red dashed arrows in temperature profile in Figure 10.1  
Figure 13 also shows spectra for areas both in and near this cloud. The image in this figure is a small portion of a single spectral channel image for a spectral channel near 5 \(\upmu\)m, lying near one local minimum in spectral radiance, indicating somewhat stronger water vapor absorption and re-emission at a lower temperature for some areas surrounding the cloud. On physical grounds, a water vapor field surrounding this low-level cloud is expected. There is also evidence of a lower-level water vapor field in the radiosonde data, shown in the lower right quadrant of Figure 10.2 The vertical position of this water vapor field is consistent with being trapped by the same temperature inversion that trapped the clouds observed in Figure 10.3  
Images of the same scene, but for spectral channels near 4.894, 4.952, 5.017, and 5.079 \(\upmu\)m, are shown in Figure 10.4 The infrared brightness for these channels is progressively lower, indicating that these channels are weighted higher in the atmosphere. The images show a broad region of higher water vapor concentration extending over much of the image, in addition to the moisture field around the lower-level clouds. Figure 15 shows infrared radiance spectra in the MISTiC water vapor band for regions both inside and outside of this moisture field, showing lower infrared radiances, especially for the radiance minima at longer wavelengths-features which indicate that this moisture field is higher in the atmosphere. Figure 15 shows the water vapor from the same Edwards 4 December sounding whose data were shown in Figure 12, but with an expanded altitude scale, together with the water vapor retrieval from the nearest cloud-free AIRS sounding less than one hour later. These both show the presence of a higher-level water vapor field, near 560 hPa over the Edwards AFB area, consistent with what was observed in the MISTiC images shown in Figure 10.5  
As noted previously, due to the cost constraints under the IIP, the airborne version of the MISTiC instrument employed a previously produced version of the IRFPA, which does not have the full spectra range planned for the MISTiC spectrometer and its custom-grown HgCdTe composition for the detector array. Specifically, it lacks the full spectral channel set needed to fully retrieve the water vapor features at 500 hPa and at higher altitudes. However, as shown in Figure 4, the full MISTiC spectral channel set, with the planned lower wavenumber limit of 1750 cm\({}^{-1}\) includes the channels needed to retrieve both the temperature and water vapor through the troposphere, with layer accuracies comparable to AIRS, and would be expected to support water vapor retrievals similar to those provided from AIRS in Figure 10.6