Journal
CLIMATE DYNAMICS
Volume 48, Issue 3-4, Pages 1213-1232Publisher
SPRINGER
DOI: 10.1007/s00382-016-3137-0
Keywords
Extreme precipitation events; Tropical forcing; Karakoram; Madden-Julian oscillation; El Nino southern oscillation
Categories
Funding
- Climate and Large-Scale Dynamics Program, from the National Science Foundation (NSF award) [AGS 1116105]
- NASA Headquarters under the NASA Earth and Space Science Fellowship Program [13-EARTH13F-26]
- Japan National Space Development Agency (NASDA)
- U.S. National Aeronautics and Space Administration (NASA) Office of Earth Science
- Directorate For Geosciences [1116105] Funding Source: National Science Foundation
- Div Atmospheric & Geospace Sciences [1116105] Funding Source: National Science Foundation
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Within the Karakoram and western Himalaya (KH), snowfall from winter westerly disturbances (WD) maintains the region's snowpack and glaciers, which melt seasonally to sustain water resources for downstream populations. WD activity and subsequent precipitation are influenced by global atmospheric variability and tropical-extratropical interactions. On interannual time-scales, El Nio related changes in tropical diabatic heating induce a Rossby wave response over southwest Asia that is linked with enhanced dynamical forcing of WD and available moisture. Consequently, extreme orographic precipitation events are more frequent during El Nio than La Nia or neutral conditions. A similar spatial pattern of tropical diabatic heating is produced by the MJO at intraseasonal scales. In comparison to El Nio, the Rossby wave response to MJO activity is less spatially uniform over southwest Asia and varies on shorter time-scales. This study finds that the MJO's relationship with WD and KH precipitation is more complex than that of ENSO. Phases of the MJO propagation cycle that favor the dynamical enhancement of WD simultaneously suppress available moisture over southwest Asia, and vice versa. As a result, extreme precipitation events in the KH occur with similar frequency in most phases of the MJO, however, there is a transition in the relative importance of dynamical forcing and moisture in WD to orographic precipitation in the KH as the MJO evolves. These findings give insight into the dynamics and predictability of extreme precipitation events in the KH through their relationship with global atmospheric variability, and are an important consideration in evaluating Asia's water resources.
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