Network objectives

Canada’s territory and the Arctic regions offer distinct challenges to Numerical Weather Prediction (NWP) and climate projection, due to complex processes and feedbacks between various components of the climate system. A better understanding of these regional climate processes and interactions is crucial to improving the quality of both climate projection and NWP for this region, and to better interpret and apply model results for use in weather and climate-change impact and adaptation studies.

The aim of the Network is to augment, evaluate and exploit the added value provided by regional models in climate and weather simulations. This added value is afforded as a result of the expected higher resolution, improved representation of physical processes, feedbacks and interactions through a Regional Earth System Model approach.

Selected results

Research highlight

Investigation of the 2013 Alberta flood from weather and climate perspectives

The destructive 2013 Alberta flood was the focus of a recent integrative project at CNRCWP. Twelve members of our team contributed their expertise to this project, including co-investigators from our three research themes. The main findings are summarized as follows.

During 19–21 June 2013 a heavy precipitation event affected southern Alberta and adjoining regions, leading to severe flood damage in numerous communities and resulting in the costliest natural disaster in Canadian history. This flood was caused by a combination of meteorological and hydrological factors, which are investigated from weather and climate perspectives with the fifth generation Canadian Regional Climate Model. Results show that the contribution of orographic ascent to precipitation was important, exceeding 30 % over the foothills of the Rocky Mountains. Another contributing factor was evapotranspiration from the land surface, which is found to have acted as an important moisture source and was likely enhanced by antecedent rainfall that increased soil moisture over the northern Great Plains. Event attribution analysis suggests that human induced greenhouse gas increases may also have contributed by causing evapotranspiration rates to be higher than they would have been under pre-industrial conditions. Frozen and snow-covered soils at high elevations are likely to have played an important role in generating record streamflows. Results point to a doubling of surface runoff due to the frozen conditions, while 25 % of the modelled runoff originated from snowmelt. The estimated return time of the 3-day precipitation event exceeds 50 years over a large region, and an increase in the occurrence of similar extreme precipitation events is projected by the end of the 21st century. Event attribution analysis suggests that greenhouse gas increases may have increased 1-day and 3-day return levels of May–June precipitation with respect to pre-industrial climate conditions. However, no anthropogenic influence can be detected for 1-day and 3-day surface runoff, as increases in extreme precipitation in the present-day climate are offset by decreased snow cover and lower frozen water content in soils during the May–June transition months, compared to pre-industrial climate.

Recent blog posts

On the representation of heavy lake-effect snow events for the Laurentian Great Lakes region in a Regional Climate Model

In my previous post (http://cnrcwp.uqam.ca/content/impact-lakes-projected-changes-surface-climate-and-hydrology), I had discussed the impact of lakes on projected changes to the near surface atmospheric fields and streamflows. There, all the lakes were parameterized using a 1D lake model. The results confirmed that lakes are important components of the climate system and affect regional climate by modulating surface albedo, surface energy and moisture budgets.

Snow-atmosphere coupling and its impact on temperature variability and extremes over North America

In my previous blog posts1, 2, I’ve shared with you how land, particularly soil moisture, interacts with the atmosphere and modulates climate extremes in current climate1 (Diro et al., 2014) and amplify the projected future warming 2 (Diro and Sushama 2017) over selected regions of North America during summer months. Land, through its snow cover and depth, also plays an important role in modulating climate during cold seasons.

The role of soil moisture-atmosphere interactions on future hot-spells over North America as simulated by the Canadian Regional Climate Model (CRCM5)

This blog is about our recent modeling study within CNRCWP aimed at exploring the role of future soil moisture-atmosphere interactions on projected hot-spell characteristics using the fifth generation Canadian Regional Climate Model (CRCM5). With this objective, two sets of CRCM5 simulations, driven by two coupled general circulation models (MPIESM and CanESM2), are performed with and without soil moisture-atmosphere interactions for current (1981-2010) and future (2071-2100) climates over North America, for Representative Concentration Pathways (RCPs) 4.5 and 8.5.

Investigation of the intra-annual variability of soil moisture-temperature coupling over North America

The land surface state plays an important role in our climate system. Soil moisture anomalies, in particular, can enhance temperature extremes. Given its potential impacts on our climate, soil moisture-temperature coupling has been well documented in recent years [Koster et al., 2004; Diro et al., 2014]. Most studies on coupling usually only focus on the summer season. However, a study by Tawfik and Steiner [2011] demonstrated that coupling could also be strong during the colder seasons.

Impact of dynamic vegetation phenology on the simulated pan-Arctic land surface state

The pan-Arctic land surface is undergoing rapid changes in a warming climate, with near-surface permafrost projected to degrade significantly and vegetation projected to grow and expand during the 21st century. These vegetation changes influence climate via modified surface albedo and land-atmosphere fluxes of energy, water and momentum. For example, vegetation growth and expansion tends to lower the surface albedo, resulting in more energy absorption and further warming. These vegetation-related feedbacks have the potential to accelerate the rate of degradation of permafrost.

Atmospheric blocking and cold extremes in North America

Extreme events can have large impacts on society. It is important to understand how circulation features are associated with extremes and to evaluate how skilfully this relationship is simulated by climate models in the current climate. The relationship between circulation features (such as atmospheric blocking) and cold extremes in high-resolution regional climate models (RCMs) is an interesting question because these circulation features can be located outside or near the edge of the typical RCM domain for North America.

Development of a glacier mass balance model to nest in a RCM

Glaciers play a role in the regional climate system due to their potential ability to reduce the energy balance by reflecting a large part of the downward solar radiation. They are also an important source of freshwater reserves, help to maintain the river flow level and can contribute to the sea-level rise. Changes in surface properties or glacier coverage might also modify surface energy balance.

On the study of a major snowstorm in a global warming context

Winter storms, especially those happening when the near-surface temperature is about 0°C, can lead to power outages, ground and air transport disruption and sometimes serious injuries. In this regard, it is crucial to better understand the processes implied in those events. The impact of global warming is not negligible for many physical processes since the temperature will probably be 2°C to 10°C higher in about 100 years. One could imagine a snow storm that happened around -10°C to -5°C to become a near 0°C storm with occurrences of freezing precipitation.

Evaluation of geographical distribution of vegetation over North America

Our terrestrial ecosystem plays a vital role in regulating climate and weather through land-atmosphere exchange and contributes in mitigating climate change. Until now the projected sink of atmospheric CO2 is uncertain due to disagreements among the Earth system models (ESMs) due to differing responses of their terrestrial ecosystem modules to future changes in atmospheric CO2. This uncertainty arises primarily because of the differences in the strength of the CO2 fertilization effect on the land carbon cycle components but also because of differences in the response of vegetation.

Outreach event with UNBC students to demonstrate importance of in situ data collection

As demonstrated to a group of University of Northern British Columbia (UNBC) undergraduate environmental science students on Saturday 5 November 2016, quality observational data are essential to validating land surface and climate model simulations. To simulate the current and future climate, a sound understanding of the land and atmospheric processes involved is essential.

Improved representation of hydrological processes in CLASS

Here, I provide a short summary of a recent research that we undertook to improve the Canadian Land Surface Scheme (CLASS) in terms of hydrological processes. Regional and global climate model simulated streamflows for high-latitude regions show systematic biases, particularly in the timing and magnitude of spring peak flows. Though these biases could be related to the snow water equivalent and spring temperature biases in models, a good part of these biases is due to the unaccounted effects of non-uniform infiltration capacity of the frozen ground and other related processes.

Mean storm occurrence over North America as simulated by CRCM5

A storm track algorithm based on tracking approach developed by Sinclair et al. (1997) is used to retrieve individual extratropical cyclone over the current period (North America domain) from meteorological fields of the North America Regional Reanalysis (NARR), the Canadian Regional Climate Model version 5 (CRCM5) driven by global reanalysis ERA-interim and the Canadian Earth System Model version 2 (CanESM2). The CRCM5 storm occurrences are compared with the ones from NARR reanalysis and the CanESM2.

Projected changes to high temperature events for Canada based on a regional climate model ensemble

Here, I provide a short summary of a recent research that we undertook to assess climate change impacts on high temperature events over Canada. We evaluated projected changes to hot spells for the future 2040-2069 period with respect to the current 1970-1999 period, for the June to August period, based on a multi-RCM (regional climate model) ensemble available from the North American Regional Climate Change Assessment Program. Two types of hot spell events HS-1 and HS-2 were considered.

Projected changes in 6-hourly probable maximum precipitation using the CanRCM4 model over North America

Probable Maximum Precipitation (PMP) is the key parameter used to estimate probable Maximum Flood (PMF). Both PMP and PMF are important for dam safety and civil engineering purposes. PMP can be considered as an asymptote which precipitation events might converge to but should never reach. A commonly used engineering approach to derive PMP estimates is moisture maximization. Using this approach the PMP for a given duration and a given period is calculated as the product of maximum precipitation efficiency and maximum precipitable water.

New TKE scheme improved CanAM4 simulated 2-m air temperature

A new semi-empirical diagnostic turbulent kinetic energy (TKE) scheme has been developed to represent downgradient turbulent transfer processes for both clear and cloudy conditions within CNRCWP. Four members from University of Victoria and CCCma including co-investigators contributed their expertise to this project. The scheme is compared with the default parameterization in the CanAM4 using three single-column modeling cases (Cabauw, ARM2X, and DYCOMS). In general, the new one performs comparably well on both stable, convective, and cloud-topped boundary layer cases.

Pathways to synoptic scale buildups in available potential energy

Zonal available potential energy (ZAPE) is an estimate of the amount of potential energy in the atmosphere available for conversion to kinetic energy, providing a good proxy for the overall strength of the jet stream and its associated cyclones and anticyclones. Large short term depletions of ZAPE have been attributed to synoptic scale processes including intense mid-latitude cyclones which are often associated with cyclonic (LC2) wave break events on the dynamic tropopause; such events have included the 1993 March Superstorm amongst others.

Historical lake-effect snowfall trends for the Ontario snowbelt

Lakes modulate the regional climate through influencing the local energy and hydrological budget, which can produce lake effect snowfall (LES). The leeward shores of the Laurentian Great Lakes are susceptible to LES during the cold season when cold and dry continental air masses advect over long axes of relatively warm water bodies. This advection drives the exchange of moisture and energy fluxes from the lake surface to the lower planetary boundary layer (PBL), inducing instability and the development of LES.

Impact of lakes on projected changes to the surface climate and hydrology

In this post I describe some results from our recent paper that looked at the impact of lakes on projected changes to the surface climate and hydrology for north-east Canada. It is well known that lakes influence the regional climate and hydrology, and therefore we had introduced a lake model in CRCM5 (Canadian Regional Climate Model) to improve the realism of simulations (Martynov et al 2012). Interactions between lakes and rivers are also now represented in CRCM5.

Investigation of the 2013 Alberta flood from weather and climate perspectives

The destructive 2013 Alberta flood was the focus of a recent integrative project at CNRCWP. Twelve members of our team contributed their expertise to this project, including co-investigators from our three research themes. The main findings are summarized as follows.

During 19–21 June 2013 a heavy precipitation event affected southern Alberta and adjoining regions, leading to severe flood damage in numerous communities and resulting in the costliest natural disaster in Canadian history. This flood was caused by a combination of meteorological and hydrological factors, which are investigated from weather and climate perspectives with the fifth generation Canadian Regional Climate Model. Results show that the contribution of orographic ascent to precipitation was important, exceeding 30 % over the foothills of the Rocky Mountains. Another contributing factor was evapotranspiration from the land surface, which is found to have acted as an important moisture source and was likely enhanced by antecedent rainfall that increased soil moisture over the northern Great Plains. Event attribution analysis suggests that human induced greenhouse gas increases may also have contributed by causing evapotranspiration rates to be higher than they would have been under pre-industrial conditions. Frozen and snow-covered soils at high elevations are likely to have played an important role in generating record streamflows. Results point to a doubling of surface runoff due to the frozen conditions, while 25 % of the modelled runoff originated from snowmelt. The estimated return time of the 3-day precipitation event exceeds 50 years over a large region, and an increase in the occurrence of similar extreme precipitation events is projected by the end of the 21st century. Event attribution analysis suggests that greenhouse gas increases may have increased 1-day and 3-day return levels of May–June precipitation with respect to pre-industrial climate conditions. However, no anthropogenic influence can be detected for 1-day and 3-day surface runoff, as increases in extreme precipitation in the present-day climate are offset by decreased snow cover and lower frozen water content in soils during the May–June transition months, compared to pre-industrial climate.