Extreme landfalling atmospheric river events in Arizona: possible future changes

Climate Change;Atmospheric Rivers;Pseudo-Global Warming;Extreme Precipitation

Singh, Itinderjot ; Dominguez ; Francina

关键词: Climate Change;    Atmospheric Rivers;    Pseudo-Global Warming;    Extreme Precipitation;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/95512/SINGH-THESIS-2016.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The semi-arid Salt and Verde River basins in Arizona depend, in part, on Atmospheric River (AR)-related precipitation for meeting the water demands of the Phoenix metropolitan area. On the other hand, the region is also susceptible to AR-related flooding. In a warming climate, water vapor in the atmosphere increases, thus likely increasing the water vapor transport within ARs. To understand the precipitation-related impacts of climate change on extreme ARs affecting Arizona, a pseudo-global warming (PGW) method was used. High-resolution control and future simulations of five intense historical AR events that affected the Salt and Verde River basin in Central Arizona were carried out. Control simulations realistically captured the magnitude and spatial distribution of precipitation during all five events. The PGW approach for future simulations involved changing the initial and lateral boundary conditions of the input data. The climate change signals of several thermodynamic variables were obtained from an ensemble of 9 General Circulation Models for RCP 8.5 scenario. Two sets of perturbations were applied to the input data. The first set consisted of constant values of temperature change at different vertical levels (PGW1) and the second set consisted of spatially varying temperature values (PGW2). Future simulations showed an overall increase in integrated vertical transport of vapor and upward moisture flux at cloud base over the region for all events. The changes in precipitation at both domain and basin level were highly spatially heterogeneous. Precipitation at the basin level increased in all PGW1 simulations but showed a decrease for some PGW2 simulations. The domain-averaged precipitation increased in all future simulations but the increase remained sub-Clausius-Clapeyron for all but one PGW2 event in which shifting and significant strengthening of the low-level jet was observed. Melting levels rose by more than 600m in all future simulations and this led to a decrease in the fraction of frozen precipitation during the events by more than 80%.