Preprints
https://doi.org/10.5194/wcd-2021-45
https://doi.org/10.5194/wcd-2021-45

  30 Jul 2021

30 Jul 2021

Review status: this preprint is currently under review for the journal WCD.

Synoptic processes of winter precipitation in the Upper Indus Basin

Jean-Philippe Baudouin1,2, Michael Herzog2, and Cameron A. Petrie3 Jean-Philippe Baudouin et al.
  • 1Department of Environmental Physics, Heidelberg University, Germany
  • 2Department of Geography, University of Cambridge, United Kingdom
  • 3Department of Archaeology, University of Cambridge, United Kingdom

Abstract. Precipitation in the Upper Indus Basin is triggered by cross-barrier moisture transport. Winter precipitation events are particularly active in this region and are driven by an approaching upper troposphere Western Disturbance. Here statistical tools are used to decompose the winter precipitation timeseries into a wind and a moisture contribution. The relationship between each contribution and the Western Disturbances are investigated. We find that the wind contribution is not only related to the intensity of the upper troposphere disturbances but also to their thermal structure through baroclinic processes. Particularly, a short-lived baroclinic interaction between the Western Disturbance and the lower altitude cross-barrier flow occurs due to the shape of the relief. This interaction explains both the high activity of Western Disturbances in the area, as well as their quick decay as they move further east. We also revealed the existence of a moisture pathway from the Red Sea, to the Persian Gulf and the north of the Arabian Sea. A Western Disturbance strengthens this flow and steers it towards the Upper Indus Plain, particularly if it originates from a more southern latitude. In cases where the disturbance originates from the north-west, its impact on the moisture flow is limited, since the advected continental dry air drastically limits the precipitation output. The study offers a conceptual framework to study the synoptic activity of Western Disturbances as well as key parameters that explain their precipitation output. This can be used to investigate meso-scale processes or intra-seasonal to inter-annual synoptic activity.

Jean-Philippe Baudouin et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wcd-2021-45', A. P. Dimri, 04 Aug 2021
  • RC2: 'Comment on wcd-2021-45', Kieran Hunt, 06 Sep 2021

Jean-Philippe Baudouin et al.

Jean-Philippe Baudouin et al.

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Short summary
Western Disturbances are mid-latitude, high altitude low pressure areas that brings orographic precipitation in the Upper Indus Basin. Using statistical tools, we show that the interaction between Western Disturbances and relief explains the near surface, cross-barrier wind activity. We also reveal the existence of a moisture pathway from the nearby seas. Overall, we offers a conceptual framework for Western Disturbance activity, particularly in terms of precipitation.