Principal components-based regionalization of precipitation regimes across the southwest United States and Northern Mexico, with an application to monsoon precipitation variability

Abstract

We determine precipitation regions for the United States-Mexico border region based on seasonality and variability of monthly precipitation at 309 stations for the period 1961 to 1990. Using a correlation matrix of input data to avoid the effect of elevation on precipitation, we apply principal components analysis with oblique rotation to regionalize this large, climatologically complex study area. We examine the applicability of the method, 2 techniques for defining region boundaries, the various defined regions themselves, and the effects of transforming input data and changing obliquity of component rotation. We obtain 9 consistent and largely contiguous regions from each of the analyses, including regions for the North American monsoon, the low deserts, the California Mediterranean regime, and for summer precipitation regimes adjoining the Gulf of Mexico. The derived regions and associated boundaries make physical sense in terms of the driving atmospheric processes, and they are robust to transformed input data and changes in rotation procedures. The central border regions are remarkably consistent across analyses, with small changes to peripheral regions. We also identify 4 monsoon sub-regions, and we illustrate the applicability of the regionalization via an analysis of relationships between monsoon precipitation variability and 500 mb pressure heights. Significantly different 500 mb circulation patterns are associated with wet and dry monsoon seasons in each of the subregions, and it appears that shifts in 500 mb circulation relative to the geographic position of each sub-region influence seasonal precipitation variability, directly or indirectly. There are important differences between some sub-regions, but in general wet monsoons are associated with northward meridional bulging of the subtropical anticyclone over the continental monsoon areas, while dry monsoons are associated with zonal stretching of the subtropical anticyclone over adjacent oceans with slightly higher pressure-heights. Overall, the study provides a clear regionalization of the precipitation climatology for the southwest United States and northern Mexico, and shows its utility for studies of climate variability.

Characterizing regional‐scale variations in monthly and seasonal surface air temperature over Mexico

“…The spatial form of SAT regions was delimited using a loading value of 0.45, and monthly and seasonal time series were constructed as simple averages of SAT anomalies for all grids located within a region's boundaries. The approach nearly mirrors our earlier work (Englehart and Douglas, 2002a,b), and it is consistent with other studies that advocate oblique rotation as an effective strategy for climate regionalization exercises (Comrie and Glenn, 1998).…”

Correlations between sea‐surface temperatures and warm season streamflow in northwest Mexico

“…E-mail: gochis@rap.ucar.edu † The National Center for Atmospheric Research is sponsored by the National Science Foundation climate (cf Tang and Reiter, 1984;Adams and Comrie, 1997;Barlow et al, 1998;Higgins et al, 2003) and readers should refer to these for a more general discussion.] The region encompassing the Sierra Madre Occidental throughout western México has emerged as a locus of convective activity for the NAM (cf Mosino and Garcia, 1974;Douglas et al, 1993;Reyes et al, 1994;Comrie and Glenn, 1998;Hu andFeng 2002, Gutzler, 2004;. Here, frequent convective precipitation, though exhibiting marked interannual variability, is a dominant driver of the annual hydrologic cycle (Gochis et al, 2006a).…”

Filling a Geographical Gap: New Paleoecological Reconstructions From the Desert Southwest, USA

“…Winter precipitation has broad spatialscale patterns with persistent light precipitation delivered by midlatitude frontal systems (Mock, 1996;Comrie and Glenn, 1998;Shinker, 2010). In contrast, summer precipitation is highly variable spatially and typically short in duration associated with convective thunderstorms delivered via the North American Monsoon System (NAMS; Mock, 1996;Adams and Comrie, 1997;Sheppard et al, 2002;Diem and Brown, 2006;Shinker, 2010).…”