Formation of Arctic mixed-phase stratocumulus in advecting air masses
Open Access
- Author:
- Simpfendoerfer, Lucien Felix
- Area of Honors:
- Meteorology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Johannes Verlinde, Thesis Supervisor
Johannes Verlinde, Thesis Honors Advisor
Eugene Edmund Clothiaux, Faculty Reader - Keywords:
- Arctic
Arctic climate
Arctic stratocumulus
Atmospheric mixed layers
Stratocumulus
Radiative Transfer
RRTM
Single column model
SCM - Abstract:
- Remote sensing observations across the Arctic indicate that Arctic stratocumuli must form through the cooling of advecting air masses during all seasons, not only in summer as was previously proposed. In this study, radiative transfer calculations and single column model simulations are used to investigate Arctic stratocumuli formation processes and their sensitivities. First, a radiative transfer model and clear-sky radiosonde observations from near Barrow, Alaska, are used to learn about the processes that drive and inhibit cooling within advecting air masses in the Arctic. Next, a single column model simulation is used to investigate how Arctic stratocumuli form when ice precipitation is involved in the formation process. Finally, sets of single column simulations are used to investigate formation processes’ sensitivities to the availability of moisture, the background static stability, and the ice precipitation rate. Radiative transfer calculations show that Arctic stratocumuli may form through radiative cooling and/or synoptic-scale lifting, and that subsidence is more effective than solar heating in inhibiting cloud formation. The single column model simulations show that ice inhibits the growth of liquid during the formation process and that the outcome of the formation process is extremely sensitive to the environment in which the process occurs. Arctic stratocumuli that form in moist environments with low concentrations of ice forming nuclei are likely to become optically thick and exert a large radiative forcing on the surface. Conversely, Arctic stratocumuli that form in dry environments or in environments with high concentrations of ice forming nuclei are likely to become optically thin or dissipate and exert a small radiative forcing on the surface. Static stability affects the formation process by modifying entrainment rates and therefore modifying the processes’ sensitivities to the availability of moisture above and below. The results highlight the importance of precipitation-radiative-dynamical interactions in simulating Arctic stratocumuli in larger-scale models.