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.
Back in the Office
Our field campaign closed with an astonishing summer snow storm – yes, I said that right: summer snow storm. The storm happened on June 21, 2019, in the Kananaskis Region (picture below). Snow on the ground and total precipitation was 20.7 cm and 56.0 mm, respectively. This storm started as a snowfall event, then turned into mixed precipitation, and ended as rainfall. Although this is a fascinating phenomenon, snow on the ground melted fast and entered the atmosphere, soil, and streams very quickly, even during the storm. Note that one of our MRRs was installed at Fortress Mountain on top of the tower.
After the field campaign it's back to the office, which is time to process and analyze the huge amount of data we gathered in the field. On my end, that means processing the data of our ground based radars, i.e., Micro Rain Radar (MRR). These instruments allow us to profile the atmosphere using radar beams that tell us about the size of the raindrops and snow crystals, which can then be related to the amount of water that enters our terrestrial hydrological system. By doing this, we are able to look at how well satellites, which have similar radar instruments onboard, are estimating precipitation near the surface. The MRRs also allow us to provide new insights on the algorithms that are used to retrieve precipitation from satellites, especially for snowfall. Ultimately, this work intends to improve precipitation inputs into hydrological models that predict snow on the ground and streamflow in our cold mountain river basins. The picture below shows the Fortress Mountain MRR reflectivity retrievals from that June 21, 2019, event.
SPADE work still ongoing
It's been about 2 and a half months since we decommissioned the field sites and ended the field campaign, but we are still hard at work on SPADE!
As the project manager, I am reviewing some article proposals and writing the data paper. I am also busy getting our dataset ready to be submitted to a data repository.
Stay tuned in the coming weeks where we will feature the work that students have been doing for SPADE, as well as some of their favourite photos from the project.
Decommissioning the field sites
Prologue: The SPADE forecasters had been waiting for this storm for at least a week when we noticed unimaginable amounts of precipitation on the long range GEM models. As the day got closer, the models still suggested large amounts of precipitation that at the time had a few of us a bit skeptical.
Our team waited for the 12PM MDT GEM model runs which came out close to 6PM MDT and we made a 24 hour plan expecting precipitation to begin at 0100 MDT. We were a bit surprised when we checked the radar around 8:30 PM and saw the rapid speed of the storm to the North making its way towards Fortress.
Fortress team (which consisted of Juris, Charlie, André and Cécile) readied themselves for the early start and we left shortly after. Excitement and adrenaline was high, much like the first Calgary storm. We even had several laughs as we filmed a tour of our trailer.
An eventful night at Fortress Top
Hilary and Juris arrived at Fortress at 0542 MDT. Skies were clear with most of the action occurring to the east and north of us. ECCC issued a snowfall warning for Jasper National Park.
Shortly after arrival the newest GEM 2.5 runs came out and the amount of precipitation expected decreased substantially. Most of the precipitation was occurring further north of our location, where several snowfall and rainfall warnings were issued For Wednesday and Thursday, with the main event occurring Wednesday early morning from 0300-0600 AM.
I (Juris) took the first shift, updating radar to see what was in the horizon. Observations began at 0750 UTC, when I noticed a cell to the west of the divide moving towards Fortress. At 0800 UTC it looked as though the smallest of particles were slowly falling, but being swirled around and staying suspended in the air for long.
GEM 2.5 timing for precipitation beginning at 0900 UTC was very close and started at Fortress around 0940 UTC. A thunderstorm continued across the continental divide during Hilary’s shift with a few loud thunder claps with its passing. The thunderstorm lasted for approximately half an hour, and, at certain points, the timing of the lightning and thunder was very close together. Winds were fairy strong during the storm. The thunder seemed to be extra loud in the mountains. Definitely an exciting part of the night!
The second round of precipitation that GEM 2.5 predicted was also very close in timing and accurate with the type of precipitation, which was forecasted as mixed. At 1420 UTC Juris observed a couple of ice pellets that were translucent in colour and then shortly after what appeared to be liquid core pellets with a very thin outer shell. Graupel then began around 1425 UTC which both Hilary and Juris noticed to resemble a diamond, though this was short lived and ended at 1430 MDT. Mixed precipitation then began and we were able to get some pictures of graupel. Winds were pretty strong, with strong gusts, with moderate visibility and precipitation was falling as strictly solid precipitation, with some occasional larger aggregates. By 1500 UTC the system had passed us, heading southeast. Both Hilary and Juris left shortly afterwards to head home to BGI.
- Hilary & Juris
Field Participants: Hilary Smith & Juris Almonte