# The Microwave Temperature and Humidity Profiler: Description and Preliminary Results
## 4 TI3 GER Campaign Measurements
### Preliminary Results  
To illustrate the preliminary results from the campaign, flights #6, #7, and #8 (see Figure 9) are selected for further analysis. Figure 10 shows the antenna temperature estimations after calibration for both 60 GHz and 183 GHz channels. To ease the visualization, all frequencies within each channel have been averaged together. The temperatures on the right-hand side of each plot correspond to the two internal loads: The warmed load, at a constant temperature of 333 K, and the ambient load, of which the temperature varies depending on the aircraft's altitude. The antenna temperature also exhibits a drop in both channels for low observation angles (zenith-facing), and a sharp transition between the zenith-facing angles (0\({}^{\circ}\) to 85\({}^{\circ}\)) and the nadir-facing angles (95\({}^{\circ}\) to 180\({}^{\circ}\)), going from below 150 K to 220-250 K in both oxygen and water vapor channels. In this case, the water vapor channel (183 GHz) exhibits a lower temperature while facing the zenith when the plane is situated at altitudes higher than 10 km, which is not the case for oxygen (60 GHz). The oxygen spectra at high altitudes have a spectral richness not comparable with the water vapor channel. For this reason, it is crucial to visualize the measured oxygen spectra at these altitudes. To validate the MTHP results, the measured antenna temperature is compared to a simulated profile generated using the Atmospheric Radiative Transfer Simulator (ARTS) [27]. To be as realistic as possible, the simulation uses three different atmospheric profiles depending on the flight. For flight #6, since it goes from Alaska to Hawaii, the 1986 COSPAR International Reference Atmosphere (CIRA86) is used, using 45\({}^{\circ}\) as a latitude setting and April as a reference month. For flight #7, the same atmosphere is used but is referenced at the Kona Island latitude of 15\({}^{\circ}\). Finally, during flight #8, a radiosonde was also launched along with the flight. In this case, the radiosonde data are used as a reference temperature. The other input parameters are summarized in Table 3.  
The comparison between the measured spectrum and the simulated one is shown in Figure 11. Note that to visualize the spectra with respect to the visualization angle, the average of the entire flight whenever the airplane is at an altitude above 10 km is used (\(\sim\)2 h of data). As can be seen, the correlation between the simulated spectra and the retrieved profile is R\({}^{2}\) = 0.92 for flight #6, R\({}^{2}\) = 0.87 for flight #7, and R\({}^{2}\) = 0.91 for flight #8. The correlation coefficient is computed after correcting bias and offset using a least-squares fit with robust regression. The first noticeable features of the measured spectra from MTHP are anomalies at 51.5 to 52 GHz and 52.5 to 53 GHz. We analyzed and concluded an  
Figure 9: The eight flights conducted during T13 GER campaign, where MTHP was fully operational, acquiring data together with other atmospheric sensor and in situ data. The color bar represents the flight altitude. The color scale for the plots is the flight altitude in kilometers. anomalous receiver temperature in this area post-flight, which should not be used for retrieval purposes. Nonetheless, several areas show good agreement with the simulated profile in both the magnitude and spectral shape. The zenith-facing part exhibits very good agreement with the simulation, showing the oxygen absorption band narrowing for higher altitudes at 53.07, 53.60, 54.14, 54.66, 55.30, and 55.80 GHz, higher frequencies exhibit a wider peak even at 10 km altitude. It is also worth noting a slight \"glitch\" or \"jump\" in the brightness temperature around 55 GHz. Note that the spectral area surrounding 55 GHz is where the two bands (upper and lower bands) used to sample the two 4 GHz portions of the spectra to produce an 8 GHz bandwidth meet. Due to the pre-sampling Nyquist filter not having a sharp cut-off and the signal an alias, this area shall not be used for science retrievals.