# Spatio-Temporal Distribution of Deep Convection Observed along the Trans-Mexican Volcanic Belt
## 2 Study Area  
The region selected for this study is located over the central part of Mexico, from 18.8\({}^{\circ}\)N, 105.4\({}^{\circ}\)W to 21.5\({}^{\circ}\)N, 95.7\({}^{\circ}\)W, with an area coverage of \(\sim\)324,483 km\({}^{2}\). The criteria for this selection were based on the significant number of tornado reports in the area (taken as a trace of severe weather), the prevalent complex terrain (serving as a static parameter in the generation of deep convection) and the large population exposed to these natural phenomena (considered as one of the risk components). Due to the amount of recently documented tornadic activity in this part of the country (Figure 1a), it is also known as the Mexican Tornado Alley (MTA). Given that these tornado climatologies are based on documentary information (i.e., social networks, eyewitnesses, newspapers and official information from authorities), it is evident that the total number of tornadoes in Mexico is underestimated [32].  
The study area extends along the influence zone of the TMVB. The TMVB has a complex orography with elevations between 0-5000 m above sea level; see Figure 1a. It is defined as a transition zone among the Nearctic and the Neotropical regions [33], separating drier climates to the north from the humid ones to the south; see Figure 1b. Likewise, the mountain ranges of the TMVB represent a great natural barrier in the propagation of cold fronts from the north and moisture fluxes from the Pacific Ocean and the Gulf of Mexico [31].  
Due to its geographical position between the Pacific Ocean and the Gulf of Mexico, the study area is influenced by tropical cyclones, cold fronts and easterly waves. These weather systems have a significant impact on the natural characteristics of this zone; see Figure 1d. For example, the center-north region is dominated by drylands, pastures and shrublands (in yellow tones), associated with the drier portion of the domain. In contrast, the center-south shows abundant vegetation with evergreen and deciduous forests (in green tones). In the eastern part, the coastal plain of the Gulf of Mexico, irrigated and dryland croplands dominate, while at the highest elevations, woodlands dominate. The western sub-region is dominated by cropland/woodland. It is important to mention that two of the most populated cities in Mexico, Mexico City and Guadalajara, are located in the study area (in red tones).  
The mean annual precipitation rate over the study area, computed for the years 2008-2017, shows the greatest values (near the 3000 mm/year) in the east sub-region; see Figure 1c. In general, high precipitation amounts are aligned with higher terrain elevations; i.e., the contribution of convective precipitation is high, at least in this part of Mexico. Along the TMVB, values between 600-1200 mm/year are shown. The area at the west of the Eastern Sierra Madre mountain range displays the minimum values(\(\sim\)300 mm/year), coinciding with an area affected by the Fohn effect and the dryer portion of the domain [34]. In summary, the relationship between precipitation-terrain-land-use and vegetation is clear.