by Isabelle Y. ’24
The Lakeside Summer Research Institute (LSRI) is a four-week summer research experience in which students engage in mentored research projects.
This summer in LSRI 2021, I used temperature data from the southern side of Mount Baker to graph and analyze lapse rates — changes in temperature with elevation. For climate researchers, lapse rates are a topic of interest because smaller lapse rates correspond with less snowmelt, and one-sixth of the world relies on glacial runoff as a water source (Minder et al., 2010). Moreover, smaller lapse rates yield warmer temperatures at higher altitudes, resulting in more precipitation and less snowfall (Minder et al., 2010). This means less snow amasses in snowpacks (accumulations of slowly melting compressed snow), and snowpack layers melt faster.
For my research, I wrote a Python program that parsed temperature data files and plotted the lapse rates of daily average temperatures (see Figure 1 below). Substantial variation is displayed in the data, including temperature inversions (i.e. negative lapse rates that indicate temperature rising with elevation) and super-adiabatic lapse rates (lapse rates above 9.8°C/km — a theoretical limit for a dry atmosphere). This variation is better represented in Figure 2, a daily lapse rate distribution with a mean, median, and mode of 2.5°C/km, 3.1°C/km, and 5.1°C/km, respectively. As for seasonal averages, summer had the largest lapse rate — 4.4°C/km — due to lack of moisture in a dry atmosphere, whereas the smallest lapse rate of 1.3°C/km occurred in spring. Even summer surface lapse rates, however, were significantly smaller than the typical free atmosphere lapse rate of 6.5°C/km.
My results show that lapse rates on Mount Baker from July 2019 to July 2020 were significantly smaller than the previously accepted 6.5°C/km. These values echo prior research conducted in the Cascades by Minder et al. (2010). In the future, climate scientists can utilize lapse rate graphs to more accurately estimate snowfall/precipitation, snowpack volume, and snowmelt on Mount Baker. By creating better models of mountain snowfall, researchers can also more accurately map the ecosystems that thrive in mountainous terrain. Hopefully, my research will inspire more people to study lapse rates in different mountain ranges. I want to extend my thanks to Dr. Town and my LSRI peers for supporting me in my learning and research experience.
Figure 1. Time series of the lapse rates of daily average temperatures from 7/20/19 to 7/16/20. The implemented sensors' elevations were 3480 ft (1060.7 m), 4040 ft (1231.4 m), and 4410 ft (1344.2 m).
Figure 2. Percentage histogram displaying the frequency of daily mean lapse rates. Although temperature inversions and super-adiabatic lapse rates are present, most lapse rates remain in the 2 to 7°C/km range.
Minder, J. R., Mote, P. W., & Lundquist, J. D. (2010, July). Surface temperature lapse rates over complex terrain: Lessons from the Cascade Mountains. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2009JD013493