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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2018-56
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
23 Feb 2018
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Hydrology and Earth System Sciences (HESS).
Combined Impacts of ENSO and MJO on the 2015 Growing Season Drought over the Canadian Prairies
Zhenhua Li1,2, Yanping Li1, Barrie Bonsal3, Alan H. Manson2, and Lucia Scaff1 1Global Institute for Water Security, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N3H5
2Institute of Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
3National Hydrology Research Center, Environment and Climate Change Canada, Saskatoon, SK, Canada
Abstract. Warm-season precipitation over the Canadian Prairies plays a crucial role in activities in environment and society and has particular importance to agricultural production over the region. This research investigates how a warm season precipitation deficit over the Canadian Prairies is related to tropical Pacific forcing in the early summer 2015 drought. The significant deficit of precipitation in May and June of 2015 were coincident with a warm phase of El Nino–Southern Oscillation (ENSO) and a negative phase of Madden–Julian Oscillation (MJO)-4 index as they both favor a positive geopotential height anomaly in western Canada. Further investigation during the instrumental record period (1979–2015) shows that the warm-season precipitation in the Canadian Prairies and the corresponding atmospheric circulation anomalies over western Canada teleconnected with the lower boundary conditions in the tropical western Pacific. MJO may play a crucial role in determining the summer precipitation anomaly in the western Canadian Prairie when equatorial central Pacific is warmer than normal (NINO4 > 0) and MJO is more active. The mechanism of this teleconnection may be due to the propagation of stationary Rossby wave that is generated in the MJO-4 index region. When the tropical convection around MJO-4 index regions (western tropical Pacific, centered over 140 E) is more active than normal when NINO4 > 0, a Rossby wave train originates from western Pacific and propagates into the midlatitude North America causing an anomalous ridge in the upper level over western Canada.
Citation: Li, Z., Li, Y., Bonsal, B., Manson, A. H., and Scaff, L.: Combined Impacts of ENSO and MJO on the 2015 Growing Season Drought over the Canadian Prairies, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2018-56, in review, 2018.
Zhenhua Li et al.
Zhenhua Li et al.
Zhenhua Li et al.

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Short summary
The research started from investigating the 2015 growing season drought over the Canadian Prairies and evolved into an investigation on the connection between growing season rain deficit in the Prairies and MJO (20–90 days tropical oscillation in convective storms). With warm central Pacific sea surface temperature, strong MJOs in the western Pacific cause Rossby wave trains that propagate downstream and favour upper-level ridges and rain deficits over the Canada Prairies during growing season.
The research started from investigating the 2015 growing season drought over the Canadian...
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