Abstract. Cold content is a measure of a snowpack's energy deficit and is a linear function of snowpack mass and temperature. Positive energy fluxes into a snowpack must first satisfy the remaining energy deficit before snowmelt runoff begins, making cold content a key component of the snowpack energy budget. Nevertheless, uncertainty surrounds cold content development and its relationship to snowmelt, likely because of a lack of direct observations. This work clarifies the controls exerted by air temperature, precipitation, and negative energy fluxes on cold content development and quantifies the relationship between cold content and snowmelt timing and rate at daily to seasonal timescales. The analysis presented herein leverages a unique long-term snow pit record along with validated output from the SNOWPACK model forced with 23 water years (1991–2013) of quality controlled, infilled hourly meteorological data from an alpine and subalpine site in the Colorado Rocky Mountains. The results indicated that precipitation exerted the primary control on cold content development at our two sites with snowfall responsible for 84.4 and 73.0% of simulated daily gains in the alpine and subalpine, respectively. A negative surface energy balance – primarily driven by sublimation and longwave radiation emission from the snowpack – during days without snowfall provided a secondary pathway for cold content development, and was responsible for the remaining 15.6 and 27.0% of cold content additions. Non-zero cold content values were associated with reduced snowmelt rates and delayed snowmelt onset at daily to sub-seasonal timescales, while peak cold content magnitude had no significant relationship to seasonal snowmelt timing. These results suggest that the information provided by cold content observations and/or simulations is most relevant to snowmelt processes at shorter timescales, and may help water resource managers to better predict melt onset and rate.
Abstract. Our climate is constrained by the balance between solar energy absorbed by the Earth and terrestrial energy radiated tospace. This energy balance has been widely used to infer equilibrium climate sensitivity (ECS) from observations of20th-century warming. Such estimates yield lower values than other methods, and these have been influential in pushing downthe consensus ECS range in recent assessments. Here we test the method using a 100-member ensemble of the Max Planck Institute Earth System Model(MPI-ESM1.1) simulations of the period 1850–2005 with known forcing. We calculate ECS in each ensemble member usingenergy balance, yielding values ranging from 2.1 to 3.9K. The spread in the ensemble is related to the centralassumption in the energy budget framework: that global average surface temperature anomalies are indicative of anomaliesin outgoing energy (either of terrestrial origin or reflected solar energy). We find thatthis assumption is not well supportedover the historical temperature record in the model ensemble or more recent satellite observations. We find that framingenergy balance in terms of 500hPa tropical temperature better describes the planet's energy balance.
more » « less- Award ID(s):
- 1661861
- NSF-PAR ID:
- 10090445
- Date Published:
- Journal Name:
- Atmospheric Chemistry and Physics
- Volume:
- 18
- Issue:
- 7
- ISSN:
- 1680-7324
- Page Range / eLocation ID:
- 5147 to 5155
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/acp-18-5147-2018
