Regional trends and local variability in monsoon precipitation in the northern Chihuahuan Desert, USA

In the southwestern United States, monsoon precipitation can affect changes to the land surface, vegetation communities and ecosystem services. To better understand monsoon precipitation, we quantified change in precipitation properties from 1910 to 2010 at 22 sites across the northern Chihuahuan Desert using United States Historical Climatology Network daily data. We also assessed precipitation variability at the Sevilleta National Wildlife Refuge (SNWR) - located at the desert's ecological boundary - using daily data from a recent 10-year period. Evaluating precipitation at these locations allows for comparison of precipitation variability between ecologically-stable ecoregions and the less-stable boundaries where ecological change may be more likely to occur. Regional data from 1910 to 2010 show an increase in the number of precipitation events, a decrease in their magnitude, and also an increase in the length of extreme periods with and without precipitation. At the SNWR, total precipitation is influenced by a small number of large events, while the majority of events (65%) have an insignificant effect. These analyses suggest that local variability in precipitation may be greater than is often attributed to the summer monsoon, and the difference between wet and dry monsoons depends on the occurrence of a small number of large events.