Understanding Deep Convection in the Midlatitudes
A team of scientists from Pacific Northwest National Laboratory, University of North Dakota, and National Aeronautics and Space Administration found that the lifetime of midlatitude convective systems lasting less than six hours is mainly attributable to the intensity of the initial convection. Systems lasting longer than six hours were associated with up to 50 percent higher mid-tropospheric relative humidity and up to 40 percent stronger middle to upper tropospheric wind shear. This resulted in continuous growth of the stratiform rain area, prolonging the system’s lifetime. The team used statistical
analysis of satellite, ground radar, and reanalysis datasets to study these deep convective systems consisting of intense convective cores, large stratiform rain regions, and extensive non-precipitating anvil clouds. This study focused on the factors that affect system lifetime and anvil cloud production, with important implications for the impact of these cloud systems on Earth’s radiation budget. An automated satellite tracking method was used in conjunction with a recently developed multisensor classification to analyze the evolution of convective system structure in a Lagrangian framework over the central United States. Regression analysis showed that anvil cloud areal coverage is strongly correlated with the size of the convective core, updraft strength, and stratiform rain area. Upper tropospheric wind speed and wind shear also play an important role for convective anvil cloud production. This research provides insight into the variety of factors that affect the life cycle of convective systems.
Feng, Z., X. Dong, B. Xi, S. A. McFarlane, A. Kennedy, B. Lin, and P. Minnis. 2013. “Life Cycle of Midlatitude Deep Convective Systems in a Lagrangian Framework,” Journal of Geophysical Research-Atmospheres 117, D23201. DOI: 10.1029/2012JD018362.