The influence of tropical forcing on extreme winter precipitation in the western Himalaya

Details

• Journal Title:
  Climate Dynamics
• Personal Author:
  Cannon, Forest ; Carvalho, Leila M. V. ; Jones, Charles ; Hoell, Andrew ; Norris, Jesse ; Kiladis, George N. ; Tahir, Adnan A.
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research) ; PSL (Physical Sciences Laboratory) ; ESRL (Earth System Research Laboratory)
• Description:
  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 Niño 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 Niño than La Niña or neutral conditions. A similar spatial pattern of tropical diabatic heating is produced by the MJO at intraseasonal scales. In comparison to El Niño, 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.
• Source:
  Clim Dyn 48, 1213–1232 (2017).
• DOI:
  https://doi.org/10.1007/s00382-016-3137-0
• Document Type:
  Journal Article
• Rights Information:
  Accepted Manuscript
• Rights Statement:
  The NOAA IR provides access to this content under the authority of the government's retained license to distribute publications and data resulting from federal funding. While users may legally access this content, the copyright owners retain rights that govern the reproduction, redistribution, and re-use of this work. The user is solely responsible for complying with applicable copyright law.
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha-512:ac9299236c1d8b5689bbf714ea773485776bbd9b490bf483b48bbf2401f9f8cf8d8854f0f63cd0d548044df167a855573080cb8d1c991ac223f4f80156c2f7ce
• Download URL:
  https://repository.library.noaa.gov/view/noaa/14513/noaa_14513_DS1.pdf
• File Type:
  [PDF - 2.61 MB ]