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Student Seminar Series

Department of Atmospheric & Oceanic Sciences

presents

a talk by

Kai Melamed-Turkish
MSc Student

A Dynamic Approach to the development of a precipitation climatology as applied to Montr茅al, Qu茅bec

Most precipitation climatologies partition the precipitation time series by identifying 24-, 48- or 72-h precipitation events. However, these partitioning methods inherently lack physical intuition. Here, I will present a precipitation climatology for Montr茅al, Qu茅bec that utilizes our understanding of atmospheric dynamics.

The quasigeostrophic (QG) omega equation provides meteorologists with a means to qualitatively diagnose vertical motion, which is necessary to produce precipitation, in the atmosphere. Knowing the positions of the low-level cyclones and anticyclones relative to the upper-level troughs and ridges, we can infer the contributions of the low-level temperature advections and upper-level vorticity advections towards omega. With this knowledge, we can use the troughs and ridges in the 500-hPa geopotential heights to qualitatively diagnose the vertical motion in the atmosphere and partition the precipitation time series. The end result is a 40-year climatology where we investigate whether precipitation in Montr茅al conforms to our expectations from the QG-omega equation.

Across all seasons, our results show that Montreal receives significantly more intense precipitation during the times when we expect unambiguous ascent, and significantly less intense precipitation during periods when we expect unambiguous descent. During the periods when we expect unambiguous ascent, the values of omega are the lowest (strongest ascent) and the 850-hPa equivalent potential temperature (q_e) anomalies are the highest and vice-versa for the periods of unambiguous descent. Overall, the results suggest that, climatologically, precipitation in Montr茅al conforms to expectations from the QG-omega equation.

Wednesday Nov 06/ 2.30 PM/ Room 934 Burnside Hall

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