Terrestrial and Oceanic Sources of North American Monsoon Moisture: A Multi-Method Approach

North American Monsoon rainfall originates from a variety of source regions including the Gulf of California, the Pacific Ocean, the Gulf of Mexico and from terrestrial recycling within the Monsoon region. In this work we use three complementary methodologies to quantify the contribution of different source regions to monsoonal precipitation. First, we use the Dynamic Recycling Model (DRM), a simple analytical model to generate a 30-year climatology of source regions. The DRM is a computationally efficient model that allows us to quantify source and sink regions of precipitation for large spatio-temporal domains. We then use newly developed water vapor tracers embedded within the weather research forecast (WRF) model to better understand the terrestrial sources of moisture, and compare our results with the DRM model. While significantly more computationally expensive than the DRM analytical model, water vapor tracers embedded within WRF are three-dimensional and include the detailed physical processes of the water cycle as represented by WRF, such as advection and diffusion, convective processes and cloud microphysics. Finally we use continuous point measurements of water vapor stable isotopes in Tucson Arizona to infer moisture sources during one monsoon season. We use a laser water vapor isotope analyzer to obtain high frequency water vapor isotopologue measurements, and compare to the numerical models. The three methods are complementary as they allow us to understand the large spatio-temporal patterns, probe into the detailed physical processes of water vapor transport and validate our numerical results with observations.