Sensitivity of Extreme Rainfall to Atmospheric Moisture Content in the Arid/Semiarid Southwestern United States: Implications for Probable Maximum Precipitation Estimates

Long Yang, James A. Smith

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Sensitivity of extreme rainfall to atmospheric moisture content for the 19 August 2014 storm in Arizona is investigated based on numerical experiments using the Weather Research and Forecasting model. Analyses are designed to develop an improved understanding of the roles of atmospheric moisture content and complex terrain in controlling spatial and temporal variability of extreme rainfall in the arid/semiarid southwestern United States. The control simulation identifies complex interactions of low-level moisture transport and orographic lift as key elements in producing extreme rainfall for the first storm episode. Two sensitivity experiments are performed by increasing the relative humidity by 10% and 20% in both initial and boundary conditions used for the control simulation. Changes in atmospheric moisture content modify the storm structure and evolution, instability of the storm environment, and interactions of synoptic flow with complex terrain. The two storm episodes within this event exhibit contrasting responses to the increase of moisture content, with rainfall accumulation and maximum convective available potential energy increased for the second storm episode as opposed to a more complex relationship for the first storm episode. A moisture maximization simulation was also designed to mimic the framework of moisture maximization in probable maximum precipitation estimates. Our results highlight the nonlinear relationship between extreme rainfall and atmospheric moisture content in complex environments where small-scale convection plays a dominant role. Limitations of probable maximum precipitation estimates based physical models are also discussed.

Original languageEnglish (US)
Pages (from-to)1638-1656
Number of pages19
JournalJournal of Geophysical Research: Atmospheres
Volume123
Issue number3
DOIs
StatePublished - Feb 16 2018

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Keywords

  • PMP
  • arid/semiarid
  • extreme rainfall
  • moisture content
  • sensitivity

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