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Dynamics of Cloud-Top Generating Cells in Winter Cyclones. Part I: Idealized Simulations in the Context of Field Observations
- Source :
- Journal of the Atmospheric Sciences. 73:1507-1527
- Publication Year :
- 2016
- Publisher :
- American Meteorological Society, 2016.
-
Abstract
- This paper assesses the influence of radiative forcing and latent heating on the development and maintenance of cloud-top generating cells (GCs) in high-resolution idealized Weather Research and Forecasting Model simulations with initial conditions representative of the vertical structure of a cyclone observed during the Profiling of Winter Storms campaign. Simulated GC kinematics, structure, and ice mass are shown to compare well quantitatively with Wyoming Cloud Radar, cloud probe, and other observations. Sensitivity to radiative forcing was assessed in simulations with longwave-only (nighttime), longwave-and-shortwave (daytime), and no-radiation parameterizations. The domain-averaged longwave cooling rate exceeded 0.50 K h−1 near cloud top, with maxima greater than 2.00 K h−1 atop GCs. Shortwave warming was weaker by comparison, with domain-averaged values of 0.10–0.20 K h−1 and maxima of 0.50 K h−1 atop GCs. The stabilizing influence of cloud-top shortwave warming was evident in the daytime simulation’s vertical velocity spectrum, with 1% of the updrafts in the 6.0–8.0-km layer exceeding 1.20 m s−1, compared to 1.80 m s−1 for the nighttime simulation. GCs regenerate in simulations with radiative forcing after the initial instability is released but do not persist when radiation is not parameterized, demonstrating that radiative forcing is critical to GC maintenance under the thermodynamic and vertical wind shear conditions in this cyclone. GCs are characterized by high ice supersaturation (RHice > 150%) and latent heating rates frequently in excess of 2.00 K h−1 collocated with vertical velocity maxima. Ice precipitation mixing ratio maxima of greater than 0.15 g kg−1 were common within GCs in the daytime and nighttime simulations.
- Subjects :
- Cloud forcing
Atmospheric Science
Daytime
010504 meteorology & atmospheric sciences
Cloud top
0208 environmental biotechnology
Longwave
02 engineering and technology
Radiative forcing
Atmospheric sciences
01 natural sciences
020801 environmental engineering
Weather Research and Forecasting Model
Climatology
Environmental science
Cyclone
Shortwave
0105 earth and related environmental sciences
Subjects
Details
- ISSN :
- 15200469 and 00224928
- Volume :
- 73
- Database :
- OpenAIRE
- Journal :
- Journal of the Atmospheric Sciences
- Accession number :
- edsair.doi...........bfdf68158e5b450a3c32544bd507b979