Monsoonal moisture sources revealed using temperature, precipitation, and precipitation stable isotope timeseries

Results of analyses using timeseries of mean temperature, precipitation amount, and stable isotopes from precipitation from July–August in Tucson, Arizona, have revealed atmospheric circulation patterns related to the North American Monsoon in the U.S. Southwest. The isotope timeseries and Tucson air temperatures and precipitation amount are significantly correlated. The temperature and isotope timeseries also correlate significantly with regional and extra‐regional specific humidity, and with Eastern Pacific SSTs near the Mexican coast, evidence for a dominantly Pacific/Gulf of California summer moisture source for the period 1983–1999. Separation of extra‐regional wind vector datasets into groups of years matching relative isotopic depletion or enrichment of the Tucson July–August precipitation seasonal means for the stable isotope timeseries (usually the extreme years in the Tucson seasonal temperature means) suggest circulation patterns entraining more tropical moisture in cooler/isotopically depleted years, and entraining less tropical moisture in hotter/isotopically enriched years.