Please login first
Moisture transport related to the ENSO effects in the Mexican precipitation
* 1 , 1 , 2 , 2 , 3
1  Centro de Ciencias de la Atmósfera. Universidad Nacional Autónoma de México. Mexico.
2  Ephyslab. Universidad de Vigo. Spain.
3  Universidad Pablo de Olavide. Spain.


In the past, several works addressed the impact of El Niño-Southern Oscillation (ENSO) on Mexican precipitation by using relative scarce observations of the National Weather Service of Mexico or reanalysis data. In this work, we reassessed the ENSO signal in Mexican rainfall by using four precipitation databases (CHIRPS, GPCC, GPCP and CMAP) over a 34-yr period (1981-2014) and three different ENSO indices. Results obtained with different datasets are consistent among them and with previous studies, showing strong positive precipitation anomalies along the winter over the northern Mexico for El Niño events. In contrast, during the summer, negative rainfall anomalies can be found over most of central and southern Mexico, being stronger in August. During La Niña years, the anomalies show approximately the opposite pattern to those observed during El Niño.

A Lagrangian approach is used to track the evaporation minus precipitation (E-P) along trajectories followed by the atmospheric particles that will take precipitable water to the areas with a precipitation amount modulated by ENSO phases. Then, composites of the obtained (E-P) fields are examined for the strong phases of El Niño and La Niña. Finally, the synoptic conditions associated with ENSO-related anomalous atmospheric water vapor fluxes are studied for a better understanding of the origin of the ENSO impact on the Mexican precipitation.

Keywords: ENSO, Moisture sources, NAM, precipitation
Comments on this paper
Ana Durán-Quesada
"Monsoon" related variability
This is a good contribution, I wonder why the effect of ENSO on the so called North American Monsoon was not considered for the analysis of precipitation variability in Northwestern Mexico?
Paulina Ordoñez
Thank you very much. We are looking for robustness and consistency throughout our region of study which is Mexico. When we compared four precipitation databases and different ENSO indices, the more robust signals were found over southern and central Mexico during summer, and over the northwestern region (which includes the Mexican part of the so-called North American Monsoon) during winter.

Obviously, it does not imply that the NAM region is not effected by ENSO during other months. For example, in our figure 1, significant anomalies of rainfall can be clearly seen over the NAM core during July for El Niño events.