Intensification of the dryline over the lee of the Canadian Rockies in a warmer climate
Abstract
Even though strong moisture gradients at low levels (drylines) are initiating convection in many mountain regions, little has been done to objectively and automatically identify them, especially to explain their changes in a changing climate. This is typically due to limited computational capabilities that do not allow to simulate mesoscale processes, such as sharp moisture gradients, on climate time scales.
An algorithm to objectively identify drylines is applied between May and August over the lee side of the Canadian Rockies. It is performed over a 13-year long period for a historical and a future climate conditions simulated by a convection permitting model at 4-km resolution. The future simulation is based on the Pseudo Global Warming approach assuming a high concentration scenario RCP8.5 at the end of the century. Here we show that the 13-year average frequency of days with dryline increases from 65% in the historical simulation to 85% in the warmer climate. The average maximum magnitude of the dryline (i.e., horizontal moisture gradient) shows a consistent and statistically significant increase between June and August, with the largest increase in July (from 0.34 to 0.38 g kg-1 km-1), along with an increase in the major axis length of 80 km (17%). The diurnal cycle of the maximum moisture gradient also amplifies during all months, with the strongest variation in July at 19 h LT, of about 0.1 g kg-1 km-1 (25%). These changes will impact the frequency of convective initiation and convection intensity.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A11V2752S
- Keywords:
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- 3319 General circulation;
- ATMOSPHERIC PROCESSES;
- 3329 Mesoscale meteorology;
- ATMOSPHERIC PROCESSES;
- 3337 Global climate models;
- ATMOSPHERIC PROCESSES;
- 3364 Synoptic-scale meteorology;
- ATMOSPHERIC PROCESSES