Meteorological conditions at genesis that differentiate intensifying and non-intensifying atmospheric rivers
Jozette Conti1 and Xubin Zeng1
1Department of Hydrology and Atmospheric Sciences
The University of Arizona, Tucson, AZ
The understanding of atmospheric river (AR) genesis remains limited, particularly with respect to the meteorological environments leading to their formation. To our knowledge, no previous study has explicitly differentiated the meteorological conditions that distinguish weak ARs that intensify from those that do not. Improved understanding of the physical drivers governing AR genesis may help reduce uncertainty in AR classification, detection, and tracking. This study examines meteorological patterns associated with AR genesis, with a particular emphasis on distinguishing between weak ARs that later intensify and those that remain weak. Twenty case studies from the Northeast Pacific are analyzed: ten events that intensify to a maximum integrated vapor transport (IVT) exceeding 250 kg m-1 s-1 following genesis (referred to as ARs in this study), and ten events whose maximum IVT remains below 250 kg m-1 s-1, hereafter referred to as atmospheric streams (ASs). A visual classification was performed at -24, -18, -12, -6, and 0 hours relative to genesis to identify key meteorological variables associated with each case type. Preliminary results indicate that intensifying AR cases are associated with stronger 250 hPa winds and integrated water vapor (IWV), while non-intensifying AS cases exhibit stronger 500 hPa relative vorticity, vertical motion, and potential vorticity. These findings are currently being translated into an automated classification algorithm to expand the analysis to a larger sample of case events. The results demonstrate distinct meteorological conditions between intensifying and non-intensifying ARs during genesis.