# The Microwave Temperature and Humidity Profiler: Description and Preliminary Results
## 4 TI3 GER Campaign Measurements
### Preliminary Results
The flights provided in Figures 10 and 11 are shown as time series on a pseudo-multi-spectral look in Figures 12-14. Each figure displays the time series of flights #6, #7, and #8 for the two receivers, at three selected angular positions (45\({}^{\circ}\) up-facing, 90\({}^{\circ}\), front-facing, and 135\({}^{\circ}\), which is 45\({}^{\circ}\) facing down, i.e., \(\pm\)45\({}^{\circ}\) and forward). For the hyperspectral channel (60 GHz), high-resolution data are provided around two absorption lines, f = 54.14 and f = 55.80 GHz, with a total  
Figure 10: Detailed antenna temperature estimations (averaged for all frequency bins) for flights #6 (**left**) (Anchorage to Hawaii), #7 (**center**) (Hawaii island), and #8 (**right**) (Hawaii to Equator) evolution over time and as a function of the observation angle (zenith = 0\({}^{\circ}\), nadir = 180\({}^{\circ}\)). The average airplane pitch is \(\sim\)2.5\({}^{\circ}\). Top row corresponds to the 60 GHz channel and bottom row to the 183 GHz channel. \begin{table}
\begin{tabular}{l l} \hline \hline
**Parameter** & **Value** \\ \hline Altitude & 10 km \\ \hline View angles & 0\({}^{\circ}\) to 180\({}^{\circ}\) (5\({}^{\circ}\) bins) \\ \hline Frequencies & 51 to 59 GHz in 31.25 MHz bins (\(B_{N_{at}}=34.6\) MHz) \\ \hline Surface reflectivity & 0.5 \\ \hline \multirow{4}{*}{Atmospheric Profile} & Flight dependant: \\  & \#6: CIRA86 latitude 45\({}^{\circ}\)/April \\  & \#7: CIRA86 Kona Island, latitude 15\({}^{\circ}\)/April \\  & \#8: Radiosonde \\ \hline \hline \end{tabular}
\end{table} 
Table 3: ARTS simulation parameters. of five frequencies around each peak. For the water vapor channel, all four channels are displayed. Figure 11: Detailed spectra measured during three flights compared to the ARTS simulated brightness temperature. Note that the 51.5 GHz to 52 GHz and the 52.5 GHz to 53 GHz regions are discarded due to RFI. Also, the region around 55 GHz is compromised due to the Nyquist filters not being sharp enough, folding outside the band inside the measurement. Figure 12: Measured Antenna Temperature for 10 selected channels (bin size is 31.25 MHz each, with \(B_{N_{eq}}=34.6\) MHz) at the 60 GHz band receiver and for the 4 analog channels (\(B_{N_{eq}}=250\) MHz each) of the 183 GHz band receiver. Flight displayed is #6, from Anchorage, AK, USA to Kona, HI, USA. Flight height is included in the right axis for reference. By analyzing the three figures, we can first see the absorption line antenna temperature when facing the \(+45^{\circ}\) incident angle at f = 54.14 GHz, with an antenna temperature higher than its adjacent frequencies, f = 54.11 and f = 54.17 GHz. It can be also seen that the temperatures at the left- and right-hand sides of the peak are similar and within a few Kelvin (compare f = 54.07 and f = 54.20 GHz). For the higher peak (f = 55.80 GHz), the temperature of the peak is also larger than its adjacent frequencies, but with lower differences. It is worth mentioning that when the airplane is at low altitudes, all frequencies show the same temperature since the absorption line broadens near sea level. At front-view, the air cross-section measured by the antenna is maxima, hence all data measure the same value, namely, that of SAT. For the \(135^{\circ}\) (\(-45^{\circ}\)) view, we can see that the lower frequency (solid line) measures a higher temperature as compared to the dashed line at the two selected absorption lines, which might be related to the fact that we are seeing the surface. It is also important to note that there is no noticeable difference between adjacent channels, as the absorption lines broaden while facing down. Similar features can be identified in the 183 GHz channel. First, in the up-facing view for high altitudes, the measured temperature is near 2.73 K (cosmic radiation). Since there is little water vapor above 14 km, there is practically no signature of it at high altitudes.