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The Contribution of Subtropical Moisture Within an Atmospheric River on Moisture Flux, Cloud Structure, and Precipitation Over the Salmon River Mountains of Idaho Using Moisture Tracers
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Abstract The Missouri River Basin, one of the primary agricultural regions in North America, is prone to large hydroclimatic variability and extreme events. The Great Plains low‐level jet (GPLLJ) is one of the major sources of moisture transport into this region, and concerns over moisture extremes already seen in the interior U.S. have been linked to changes in GPLLJ. However, the relationship between GPLLJ and precipitation in this region remains uncertain, with studies showing conflicting results that may be related to distinct types of jet events. Here, we use daily GPLLJ data to study connections between different types of jet events and precipitation, integrated water vapor transport, and synoptic conditions to better understand GPLLJ‐streamflow linkages. We assess GPLLJ conditions during historical flood events and potential future changes using CMIP6 projections. We find: (a) in May–September, GPLLJ is associated with 29%–46% of monthly precipitation and with increased precipitation intensity; (b) GPLLJ has a consistently positive impact on Missouri River streamflow over the warm season; (c) coupled jets have a larger impact on moisture transport than uncoupled jets, but streamflow impact is reduced, likely due to seasonal timing; (d) unusual jet conditions preceded historical warm‐season flood events; and (e) future projections indicate relatively small changes in GPLLJ meridional wind velocities along with large increases in moisture transport driven by humidity increases. Although future streamflow will be partially dependent on snowmelt from the upper basin, the projected intensification of warm‐season moisture transport to the Missouri River suggests possible increases in future flood risk.more » « less
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The Mantaro River Basin is one of the most important regions in the central Peruvian Andes in terms of hydropower generation and agricultural production. Contributions to better understanding of the climate and hydrological dynamics are vital for this region and constitute key information to support regional water security and socioeconomic resilience. This study presents eight years of monthly isotopic precipitation information (δ18O, Dxs) collected in the Mantaro River Basin. The isotopic signals were evaluated in terms of moisture sources, including local and regional climatic parameters, to interpret their variability at monthly and interannual timescales. It is proposed that the degree of rainout upstream and the transport history of air masses, also related to regional atmospheric features, are the main factors influencing the δ18O variability. Moreover, significant correlations with precipitation amount and relative humidity imply that local processes in this region of the Andes also exert important control over isotopic variability. Two extreme regional climate events (the 2010 drought and the 2017 coastal El Niño) were evaluated to determine how regional atmospheric circulation affects the rainfall isotope variability. Based on these results, recommendations for hydroclimate studies and paleoclimate reconstructions are proposed in the context of the Mantaro River Basin. This study intends to encourage new applications considering geochemical evidence for hydrological studies over the central Andean region.more » « less
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Abstract Observations of column water vapor in the tropics show significant variations in space and time, indicating that it is strongly influenced by the passage of weather systems. It is hypothesized that many of the influencing systems are moisture modes, systems whose thermodynamics are governed by moisture. On the basis of four objective criteria, results suggest that all oceanic convectively-coupled tropical depression-like waves (TD-waves) and equatorial Rossby waves are moisture modes. These modes occur where the horizontal column moisture gradient is steep and not where the column water vapor content is high. Despite geographical basic state differences, the moisture modes are driven by the same mechanisms across all basins. The moist static energy (MSE) anomalies propagate westward by horizontal moisture advection by the trade winds. Their growth is determined by the advection of background moisture by the anomalous meridional winds and anomalous radiative heating. Horizontal maps of column moisture and 850 hPa streamfunction show that convection is partially collocated with the low-level circulation in nearly all the waves. Both this structure and the process of growth indicate that the moisture modes grow from moisture-vortex instability. Lastly, space-time spectral analysis reveals that column moisture and low-level meridional winds are coherent and exhibit a phasing that is consistent with a poleward latent energy transport. Collectively, these results indicate that moisture modes are ubiquitous across the tropics. That they occur in regions of steep horizontal moisture gradients and grow from moisture-vortex instability suggests that these gradients are inherently unstable and are subject to continuous stirring.more » « less
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2022JD037727
