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https://doi.org/10.5194/esd-2018-32
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
30 May 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Earth System Dynamics (ESD).
On the origin of moisture related to synoptic-scale rainfall events for the North American Monsoon System
Paulina Ordoñez1, Raquel Nieto2, Yolande L. Serra3, Luis Gimeno2, Pedro Ribera4, David Gallego4, Carlos A. Ochoa1, and Arturo I. Quintanar1 1Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México, Mexico City, 04510, Mexico
2Environmental Physics Laboratory (EphysLab), Universidade de Vigo, Ourense, 32004, Spain
3Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, 98105, US
4Dpto. de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Seville, 41013, Spain
Abstract. This work examines the origin of atmospheric water vapor arriving to the North American Monsoon (NAM) region over a 34-yr period (1981–2014) by using a Lagrangian diagnosis method. This methodology computes budgets of evaporation minus precipitation by calculating changes in the specific humidity of thousands of air particles advected into the study area by the observed winds.

During the NAM wet season, on average the recycling process is the main water vapor source, followed by the supply of moisture from the Gulf of California. However, the water vapor transport that generates synoptic-scale rainfall comes primarily from the Caribbean Sea, the Gulf of Mexico and terrestrial eastern Mexico. An additional moisture source over the southwestern US is also identified in association with synoptic rainfall events over the NAM region.

A high (low) moisture supply from the Caribbean Sea and the Gulf of Mexico from 4 to 6 days before precipitation events is responsible for high (low) rainfall intensity on synoptic scales during the monsoon peak. Westward propagating mid to upper level inverted troughs (IVs) seem to favor these water vapor fluxes. A 200 % increase in the moisture flux from the Caribbean Sea is related to the occurrence of heavy precipitation in the NAM area, accompanied by a decrease in water vapor advection from the Gulf of California.

Citation: Ordoñez, P., Nieto, R., Serra, Y. L., Gimeno, L., Ribera, P., Gallego, D., Ochoa, C. A., and Quintanar, A. I.: On the origin of moisture related to synoptic-scale rainfall events for the North American Monsoon System, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2018-32, in review, 2018.
Paulina Ordoñez et al.
Paulina Ordoñez et al.
Paulina Ordoñez et al.

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Short summary
The identification of moisture sources for a region is of prominent importance to characterize precipitation. In this work, the moisture sources for the North American Monsoon (NAM) region are identified, being mainly the Gulf of California, the recycling process and the eastern Mexico together with the Caribbean Sea. We find that the rainfall intensity over the NAM region is related to the amount of moisture transported from the Caribbean Sea and eastern Mexico during the preceding days.
The identification of moisture sources for a region is of prominent importance to characterize...
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