Cloud Processes Associated with Extratropical Cyclones

The clouds in extratropical cyclones (ECs) lie at the intersection of well-developed theory of dry baroclinic waves and nonlinear feedback on their dynamics due to the effects of moisture and radiation. Of all cloud regimes, EC clouds are the most effective at blocking short-wave radiation, while trapping heat within the troposphere via long-wave blocking. The net modulation of moist processes on the transient wave and the resulting climatological effects due to modified energy and water transports remain unclear. A novel cyclone tracking algorithm (NASA's MCMS) is used to identify ECs in the ERA-I reanalysis data and collect properties of each disturbance. A classification scheme based on cyclone radius and pressure depth is developed. Properties of resulting classes are analyzed, and composites of radiation (ISCCP FD) and precipitation (TRMM TMPA) are assembled for each class. Lifetime and temporal evolution of the clouds, radiation, and precipitation will also be considered. The depth—radius classes defined here meaningfully discriminate between over 10⁶ extratropical disturbances and correspond with distinguishable regimes of precipitation and radiation. Seasonal variability of cyclone types and their diabatic heating are described as well as interesting interannual trends.