It has now been more than three months since the SPADE field campaign in the Canadian Rockies came to an end. Since then, I have returned to work on my master’s project at the UQAM research office in Montreal, Qc. My research project is part of SPADE which was the study of precipitation in the Rocky Mountains. The main goal of my master's is to characterize the influence of atmospheric fluid dynamics on the spatial distribution of precipitation at the surface and in complex terrain, and at mountain-ridge and slope scales. A better knowledge of precipitation accumulation patterns, especially mixed and solid precipitation, allows better understanding and prediction of hydrology and water resources, for example during melting periods.
Specifically, we focussed on the influence of disturbed flows by obstacles such as mountains on the spatial variability of hydrometeor preferential deposition. The effect of precipitation types will also be investigated, as the drag coefficient and the fall speed of a hydrometeor depend on its shape and density. To characterize the atmospheric flow, we will conduct simulations of mean-turbulent and stationary flow around a mountain, such as Fortress Mountain, with computational fluid dynamics software OpenFOAM®. This will be combined with numerical models of precipitation trajectories and equations of motion for particles subjected to wind drag force.
Several datasets collected during the SPADE campaign will also be considered in this research. The processing of the data collected by the wind Doppler LiDAR HALO® will allow us to obtain wind speed profiles that we can compare with the numerical flow simulations. Also, the data from the optical disdrometer Parsivel® tells us the main types of precipitation that were observed by the instruments during precipitation events. This can also be used to characterize hydrometer types associated with different wind and other meteorological variables given by other instruments used during the field campaign.
Finally, since returning back home, I’ve been working a lot on the numerical processing of the LiDAR data. I have also worked on a literature review to investigate all the previous work that has been accomplished in that field of atmospheric sciences and to develop a better understanding of wind-induced processes that influence, at small scale, precipitation deposition patterns on the ground.
I am glad to work on a such motivating project that allowed me to discover the Rockies, one of the most beautiful regions of our vast country. I keep wonderful memories of that experience and of the extraordinary people I’ve met.
Mott, Rebecca, Vincent Vionnet, and Thomas Grünewald. "The seasonal snow cover dynamics: review on wind-driven coupling processes." Frontiers in Earth Science 6 (2018): 197.
After the storms have passed
As my colleagues from Fortress were packing up their snow boots, I was packing away my sunscreen. During our last major precipitation event on June 21st, we received over 19.0 mm of precipitation in less than 12 hours at Nipika. However, once the storm subsided at our site, we were basking in summer conditions, watching the hot sun chase away vestiges of cloud. Meanwhile, our colleagues at the other site continued to battle snowstorms. For me, this only highlighted the vital importance of studying weather on both side of the continental divide.
After the storms dissipated, I returned to Prince George to try to organize and compartmentalize the treasure trove of meteorological information that we had accumulated during the two months of the SPADE field season. Having unplugged the stream of meteorological data, we had to improve its universality; increasing our ability to share it with the rest of the world. Part of this process involved filling in missing time-stamps, cleaning off electronic errors, and removing the peculiar measurements that result from electronics being re-programmed. I also created documents that would give others the ability to comprehend the endless strings of numbers that we had created.
Having witnessed the beauty of orographic precipitation for two months, I have set about studying it. My pile of papers has steadily grown, crawling across the desk of my office, swallowing small books, and bits of stationary. I have also been collecting weather station data from various places in British Columbia and Alberta. I am hoarding it in various crevices of my computer, and incubating it for a beautiful metamorphosis in the near future, a confluence of different data streams that will enrich our understanding precipitation gradients over the continental divide.
While working on this bigger project, I have been graphing information that I collected from a precipitation gauge transect on the Cross Resource Road. Currently, I am examining potential relationships between wind direction and precipitation rates. In the first image below, the graph on the upper left depicts average daily wind direction during a precipitation event and the graph on the lower right depicts cumulative precipitation amounts between May 12th and June 23rd, 2019, at four different sites near the continental divide.
I miss the SPADE field season, my kind colleagues, and their lively intellect. Excellent collaboration arose in response to inclement weather and unruly weather instruments. My favourite SPADE picture is emblematic of our comradery, a good conversation in the middle of a long day of weather observations.
Time for some analysis
After two very intense months of the field campaign in the Rockies, it was finally time to cool down and go back to Montreal to start working on all the data collected. As my PhD project is about the mesoscale modelling of precipitation across the continental divide, the first step for me was to spot and analyze the main events that would be interesting for me to study. I selected 4 of them. The goal now is to make the synoptic analysis of these events, and characterize their common and uncommon patterns to see what conclusions we can take of the orographic processes that took place during this whole campaign. To that extent, I have been collecting synoptic maps, radar and satellite images, soundings, and trying to link all this information by going deeper and deeper in the atmosphere until finally studying the surface conditions measured by our weather stations in Fortress and Nipika, such as the temperature, the relative humidity, the accumulated precipitation and the wind speed.
On the pictures below, the low pressure system located in the area on June 21st brought the last and most intense storm for both Fortress and Nipika, with respectively 56 and 19 mm of rain collected. However it is interesting to see how drier and warmer the weather was at Storm Lodge in the very same time, even if located just in the middle of both stations !It is a curious experience, working on the data we have been collecting all together for so long, as it reminds me of such great and intense moments we had while doing it. As an example, the picture below shows all the happiness (probably mixed with exhaustion) we felt once this last and biggest storm was declared over, and we knew at that point that the field campaign was a total success. That kind of moments brings a whole new dimension to our scientific work.