Formation of Arctic mixed-phase stratocumulus clouds in advecting air masses
Open Access
- Author:
- Simpfendoerfer, Lucien Felix
- Graduate Program:
- Meteorology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 05, 2018
- Committee Members:
- Johannes Verlinde, Thesis Advisor/Co-Advisor
- Keywords:
- Arctic
Arctic Amplification
Stratocumulus
Atmospheric radiative transfer
Single Column Model
Cloud-top humidity inversions
Formation of Arctic stratocumulus
Climate change
Cloud-driven mixed layers
Mixed layers
Arctic clouds
Arctic climate
Altocumulus
Layered cloud - 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.