## 5 Co-Located Atmospheric Disturbances
### Specific Humidity  
Specific humidity (SH) is a ratio of the weight of water vapor in a specified volume to the weight of dry air in the same volume. In the selected area, the rate of the seasonal cycle with a minimum in the winter months is about 10\({}^{-4}\) SH units per one degree in temperature according to MERRA-2. In the context of the link between earthquakes and atmospheric perturbations, one may expect that due to moisture condensation on ion clusters, the number of free water vapor molecules in the air decreases, which is recorded as a decrease in humidity.  
Figure 11a depicts the near-surface SH variations over ten days prior to and after EQ. The curve is composed of the 3-h data averaged over the area 36\({}^{\circ}\)-45\({}^{\circ}\)N, 65\({}^{\circ}\)-95\({}^{\circ}\)E. From this figure, one can see the temporal dynamics of the regional SH with a gradual decrease starting approximately 7 days prior to the EQ, a deep minimum on 21-22 January, when the SH dropped to \(\sim\)0.0008 from \(\sim\)0.0016, and a gradual recovery within 5 days after the EQ. It should be noted that SH is directly linked to the air temperature. The air temperature actually measured in Almaty City ([[https://www.accuweather.com/](https://www.accuweather.com/)]([https://www.accuweather.com/](https://www.accuweather.com/)); accessed on 30 March 2024) is presented in Figure 11b. The temperature was mostly negative. After 15 January, it tended to become cooler, while no pronounced reduction similar to that in SH was observed. Thus, the thermal changes in the near-surface air layer and the behavior of SH were rather consistent with atmospheric thermodynamics. Some studies have reported the occurrence of positive thermal anomalies associated with earthquakes [8; 60]. However, for this event, no clear indication of the increased air temperature at the time period around EQ is found. This could be due to the investigated period, as previous studies reported thermal anomalies with more weeks in advance [61].  
To identify the geographical location of the minimum, in Figure 12, we show a diagram of the spatiotemporal variability of the SH, which allows one to visualize the evolution of the parameter from its static images. The diagram is plotted along the time-latitude axes (the x-axis is days of January, and the y-axis is latitude between 29.5\({}^{\circ}\)N and 44.5\({}^{\circ}\)N). Each  
Figure 11: Time series of (**a**) daily values of specific humidity from 10 January to 1 February; each point represents the SH value averaged over the area of 35\({}^{\circ}\)–45\({}^{\circ}\)N, 65\({}^{\circ}\)–95\({}^{\circ}\)E, and (**b**) temperature in Almaty City; the mean of the highest and lowest daily values. The EQ time is indicated by red line.  
column of pixels represents the SH averaged over the longitudes 65\({}^{\circ}\)-95\({}^{\circ}\)E. The spatial distribution of anomalies shown in Figure 12 suggests that the SH drops just above the epicenter and a day before the main shock. The diagram also reveals a quasi-systematic latitudinal variation in SH, which persists throughout the entire time period. Positive ridges are identified near 42\({}^{\circ}\) and 30\({}^{\circ}\)N, while a decrease is observed at \(\sim\)35\({}^{\circ}\)N. This resembles the signature of the planetary wave, which is often observed in the atmospheric parameters (e.g., [62]). However, the drop in humidity that occurred on 22 January at 40\({}^{\circ}\)-42\({}^{\circ}\)N does not seem to be related to a wave train. Rather, this is a \"stay-alone\" signature of enhanced condensation of water vapor and latent heat release, which can be associated with EQ since the strengthening of the fault is accompanied by additional ionization of air due to radon emanation.