Does future springtime drying in the North American Monsoon region mean a late monsoon?

Authors: Sara Rauscher*, Department of Geography, University of Delaware
Topics: Climatology and Meteorology, Latin America
Keywords: monsoon, precipitation, Mexico, southwestern United States
Session Type: Paper
Day: 4/11/2018
Start / End Time: 10:00 AM / 11:40 AM
Room: Napoleon B3, Sheraton 3rd Floor
Presentation File: No File Uploaded

Precipitation seasonality and its variability in monsoon regions – including the North American Monsoon in Mexico and the southwestern United States – is a critically important part of the global water cycle. Global climate model (GCM) projections of future climate indicate robust changes in the annual cycle of precipitation in monsoon regions. In simulations with increasing greenhouse gases (GHGs), the annual cycle of precipitation is amplified, such that dry seasons become drier, and wet seasons are wetter (Rauscher et al. 2008; Seth et al. 2010, 2011, 2013). It is not clear whether these annual season changes indicate a delay in monsoon onset, however. To that end, I examine changes in onset dates in the North American Monsoon using daily precipitation data from observations, the North American regional reanalysis, and model data from CMIP5 and the regional CORDEX project. Most of the models show wet biases when the historical simulations are compared with observations. Additionally, the timing of the monsoon is poorly simulated with early onsets in the southern Mexico and late onsets in Arizona. Future projections show a later monsoon onset at the end of the century, although the change is small compared to the model biases. However, the models more consistently show a late monsoon withdrawal in the future climate projections. Future research will explore the mechanisms behind these annual cycle changes, including the role of SST warming patterns and land-atmosphere coupling.

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