Effect of the Trans‐Volcanic Axis on meridional propagation of summer precipitation in western Mexico

Abstract

The Trans-Volcanic Axis (TVA)-comprising ridges and terrain elevations above 1,900 m-strongly affects meridional propagation of summer precipitation in western Mexico. This barrier modifies atmospheric moisture content and changes the annual precipitation cycle configuration, which distinguishes it from the precipitation cycle on both sides of the TVA. Using upper-air observations and rainfall records, this study demonstrates that the TVA is the region where the North American monsoon (NAM) and the mid-summer drought (MSD) influence intersections regarding precipitation. This region affects both northward extent of double precipitation maxima with the MSD and the southward extent of the NAM single precipitation peak. This study proposes that the forcing mechanism that controls the annual precipitation cycle in the TVA region relies on latent heat loss via ground cooling by reducing air temperature below dewpoint temperature in the 700-500 hPa layer, consistent with local terrain elevations. The orographic effect increases specific humidity in the atmospheric column-sufficiently large to enhance local precipitation accumulation-resulting in a mid-summer drought intensity decline but not enough to yield a single peak in precipitation. Consequently, the TVA becomes an uncategorized region that does not display the NAM nor the characteristic features of the MSD.

Thunderstorm and hailstorm environments in Mexico

“…Remarkably, a bimodal distribution is observed only in the NW subregion (active vs. inactive season), which has been related to the influence of the North American Monsoon (Boos & Pascale, 2021; Ramos‐Pérez et al, 2022). The highest thunderstorm activity in FV has been associated with the role of complex terrain features in generating deep convection (Brito‐Castillo et al, 2022; León‐Cruz et al, 2021). The GM and YP seasonal patterns are associated with the previously mentioned tropical activity (i.e., easterly waves and tropical cyclones) over the Caribbean Sea.…”

“…For this portion of the country, intermediate-low shear and low-CAPE environments are typical for the formation of thunderstorms and hailstorms. Previous investigations have suggested the critical role of orography as a primordial mechanism for lifting and trigged convection (Brito-Castillo et al, 2022;Le on-Cruz et al, 2021). Further investigations are required to create a proper severe weather index for regions with such characteristics.…”

“…For example, mesoscale convective systems (MCS) over northwestern Mexico have been widely analysed during the North American monsoon (NAM) (Farf an et al, 2021;Ramos-Pérez et al, 2022;Valdés-Manzanilla, 2015). Likewise, the spatiotemporal distribution of precipitation and deep convective clouds over FV has been analysed, illustrating that both events are related to the orographic features (Brito-Castillo et al, 2022;Le on-Cruz et al, 2021). In addition, other research has examined the spatiotemporal distribution and characteristics of severe local storms, including hail, and some convective modes, as supercell storms (Concepci on et al, 2007;Edwards, 2006;Weiss & Zeitler, 2008).…”

Interannual Variability in the Coastal Zones of the Gulf of California

“…Hourly observations of air temperature (AT, °C), relative humidity (RH, %), atmospheric pressure (AP, hPa), wind (W, m/s) and zonal (U, east-west m/s) and meridional wind (V, north-south, m/s) components were covered during the period from 1 January In winter, several midlatitude systems predominate, such as cold fronts, air masses, and jet streams [14,19,30], while in summer, rainfall is primarily controlled by the North American monsoon (NAM) system [16,[32][33][34][35][36] and numerous transient disturbances, such as mesoscale convective systems, tropical cyclones, easterly waves, inverted troughs, the Madden Julian oscillations, and midlatitude troughs. Wang and Fiedler [37] noted that ENSO is a coupled phenomenon in the ocean-atmosphere system that causes climate variability in the GoC.…”

ENSO Impact on Summer Precipitation and Moisture Fluxes over the Mexican Altiplano

“…Additionally, Farfán et al [21] identified a persistent deep convection region along and off the coast of Nayarit, while another study [23] showed that summer rainfall behaves in a contrasting way along coastal Nayarit to that observed on the Mexican Altiplano. It is important to note that this region is positioned in the transition zone where the annual precipitation cycle changes from the double precipitation peak with the midsummer drought to the south, to a single rainfall peak characteristic of the monsoon in the north [24]. All these features are important to understand seasonal and interannual precipitation variabilities in Western Mexico.…”