## 3 Results  
### Hurricane Jerry (2019) Case Study  
The authors collaborated on a total of five NOAA G-IV flights. For brevity, we focus on the 18 September 2019 flight around Hurricane Jerry, because this mission allowed us to evaluate both moist and dry air masses. Figure 1 shows the locations of coincident dropsondes and NUCAPS retrievals from NOAA-20 for the 18 September 2019 flight around Hurricane Jerry. The collocations are numbered in sequence, and the color-coded dots show where IR + MW retrieval succeeded (green), where the MW-only retrieval succeeded (yellow), and where both were rejected (red). The background airmass RGB image [30] was created from the GOES-16 advanced baseline imager (ABI) channels 8 (6.2 \(\upmu\)m), 10 (7.3 \(\upmu\)m), 12 (9.6 \(\upmu\)m), and 13 (10.3 \(\upmu\)m). The airmass RGB shows regions of dry low- to mid-level air (warmer hues) wrapping around Hurricane Jerry to the west and moist tropical [31] air masses (cooler hues) to the south. The dashed contour line is illustrative and drawn from the difference between 6.2 and 7.3 \(\upmu\)m to help distinguish airmasses. This flight sampled a mixture of both regimes in the hurricane environment, with dropsonde numbers 0-4, 9-12, and 18-19 sampling the moist tropical air and dropsonde numbers 5-8, 13-17, and 20 sampling dryer air associated with a Saharan Air Layer outbreak and a mid-latitude dry air intrusion [31]. The remaining sondes (21-24) sampled the hurricane.  
Figure 1: The G-IV flight path on 18 September 2019 between 14:00 and 19:00 UTC showing the dropsonde locations and the quality flag of the nearest match with the NUCAPS retrieval from NOAA-20 satellite. The background shows the GOES-16 Airmass RGB image at 16:00 UTC. The quality flag has three color values, which are green when the IR + MW retrieval passed (clear to partly cloudy scenes), yellow when the MW-only passed (cloudy scenes), and red when both were rejected (precipitating scenes). The dashed contour line is illustrative and drawn from the subtraction of ABI 6.2–7.3 \(\upmu\)m channels.  
This flight sampled different airmass regimes, and Figure 2 shows the resulting profiles from the collocations. The color-coded squares on the \(x\)-axis show the same quality flags from Figure 1; all but the last four IR + MW retrievals were successful. The NUCAPS temperature and water vapor mixing ratio both show good agreement with the dropsonde when the IR + MW retrieval was successful. Temperature smoothly varies with space, so differences in the vertical resolution between the dropsonde and NUCAPS are less noticeable (Figure 2c). For water vapor, more structure is present in the dropsonde (Figure 2d) due to its higher vertical sampling and often narrower footprint than in NUCAPS (Figure 2e), resulting in larger differences between the two. Interestingly, the airmass RGB in Figure 1 shows that dropsonde numbers 13-16 are in a dryer region, but both NUCAPS and dropsondes cross-sections indicate this region is rather moist. While the magnitudes do not have perfect agreement (Figure 2f), NUCAPS captures the horizontal water vapor gradients and the vertical structure well compared to the dropsonde.