A possible link between wildfire aerosol and North American Monsoon precipitation in Arizona–New Mexico

Abstract

Previous research highlights the dominant role of Pacific sea surface temperatures (SSTs) and their associated large-scale teleconnections in modulating the North American monsoon (NAM). At the regional scale, feedbacks associated with land-surface boundary conditions have been shown to provide 'memory' in the system. Here, a previously unexplored second-order linkage between aerosol generated by late-spring wildfires and subsequent summer precipitation delivered by the NAM in the Arizona-New Mexico (AZNM) region is proposed. Correlations between June/July organic carbon and elemental carbon (OC/EC) in Inter-agency Monitoring of Protected Visual Environments (IMPROVE) aerosol data (Gila Wilderness and Bandelier) and NAM precipitation in southern AZNM over the period 1994-2012 are shown to be negative (r = -0.4), suggesting that active antecedent wildfire seasons tend to be immediately followed by a weak late summer monsoon. This result is consistent with a previous study linking precipitation and area burned in wildfires in AZNM. A survey of extant literature suggests a sound basis for potential mechanisms related to convective processes and cloud microphysics, and furthermore suggests that this forcing could be of similar magnitude to well-documented land-based second-order NAM forcings (antecedent snowpack and soil moisture, vegetation, and mineral dust). Based on these results, we believe that the role of aerosols in modulating summer precipitation deserves further investigation both observationally and in modeling studies. If indeed wildfire smoke does contribute to the modulation of NAM intensity, by virtue of its close temporal association with NAM season, it may well represent a factor that could contribute effectively to improved seasonal prediction of summer precipitation in the NAM region.

Monsoon Responses to Climate Changes—Connecting Past, Present and Future

“…There is some spatial variability in trends, with precipitation increases over June through September in northwest Mexico and the southwestern USA from 1948 to 2010, with decreases occurring in central and southern Mexico over the same time period [111]. The reduced precipitation could be linked to antecedent wildfire aerosols [112].…”