Monday, 9 July 2018
Regency A/B/C (Hyatt Regency Vancouver)
Open and closed mesoscale cellular convection (MCC) are an important morphological group of low clouds that occur globally and are seasonally variable. These clouds potentially have a large climatic impact as they are found to have significantly different cloud optical depths and thus radiative impacts. Their dominance in regions of large uncertainty in models (i.e. the Southern Ocean and cold sectors of cyclones) makes them especially important to understand for improving low cloud parameterizations and reducing cloud bias in models. A MCC neural network classification dataset is used in combination with NASA A-Train satellite retrievals and ECMWF ERA-Interim reanalysis to investigate characteristics and controls on open and closed MCC. Thermodynamic forcing associated with temperature gradients from marine cold air outbreaks are found to be important for open and closed MCC development, particularly in the mid-latitudes and sub-tropics. These clouds are well-predicted using metrics that combine the influence of atmospheric static stability and surface forcing. The relative influence of aerosols and precipitation on the development of MCC compared to the thermodynamic forcing are also examined in this study. Results from our study can be used to improve the parameterization of cloudiness and reduce shortwave bias in cyclonic cold fronts (i.e. cold air outbreaks) as well as advance the simulation of marine low clouds.
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