Cloud Radiative Effects and Precipitation in Extratropical Cyclones

Abstract

Clouds associated with extratropical cyclones complicate the well-developed theory of dry baroclinic waves through feedback on their dynamics by precipitation and cloud-altered radiative heating. The relationships between cyclone characteristics and the diabatic heating associated with cloud radiative effects (CREs) and latent heat release remain unclear. A cyclone tracking algorithm [NASA’s Modeling, Analysis, and Prediction (MAP) Climatology of Midlatitude Storminess (MCMS)] is used to identify over 106 cyclones in 33 years of the ERA-Interim and collect the properties of each disturbance. Considering storm intensity as related to wind speeds, which depend on the pressure gradient, the distribution of cyclone properties is investigated using groups defined by their depth (local pressure anomaly) and the radius of the region within closed pressure contours to investigate variations with longitude (especially ocean and land), hemisphere, and season. Using global data products of cloud radiative effects on in-atmosphere net radiation [the ISCCP radiative flux profile dataset (ISCCP-FD)] and precipitation (GPCP), composites are assembled for each cyclone group and for “nonstormy” locations. On average, the precipitation rate and the CRE are approximately the same among all cyclone groups and do not strongly differ from nonstormy conditions. The variance of both precipitation and CRE increases with cyclone size and depth. In larger, deeper storms, maximum precipitation and CRE increase, but so do the amounts of nonprecipitating and clear-sky conditions.

A New Perspective for Future Precipitation Change from Intense Extratropical Cyclones

“…And while such a change is consistent with a slight deepening in the composite mean synoptic-filtered MSLP (Figure 2c), to the extent such a signal is real, it is small. Further to this judgement, we also checked the closed contour size as a metric of EC size (Polly & Rossow, 2016) and find no clear changes with warming.…”

Coupling of Precipitation and Cloud Structures in Oceanic Extratropical Cyclones to Large-Scale Moisture Flux Convergence

“…The most rapid recycling during the deepening stage is realized as the largest loop of phase changes in the Q cnvg Q advt space, with the largest precipitation in the WF and CF sectors and the largest surface evaporation in the CF and CS. This is also related to the largest differences in extreme values (maximum minus minimum) of cyclone precipitation (Rudeva and Gulev 2011) and cloud radiative forcings (Polly and Rossow 2016). Since poleward transport of atmospheric moisture is mainly driven by transient eddy processes caused by ETCs, the extreme contrasts of Q advt in ETCs (i.e., moist advection in the PWF minus dry advection in the PCF) measure their efficiency in poleward moisture transport.…”

“…Following Polly and Rossow (2016), the depth of an ETC is measured by the difference between the SLP at the cyclone center and the outermost closed SLP contour. The depth of each ETC is determined for each 6-hourly time step along its track.…”

“…Rudeva and Gulev (2011) demonstrated that deepening cyclones have larger differences in extreme values of surface turbulent fluxes and precipitation than decaying cyclones. Polly and Rossow (2016) illustrated that the extreme values (maximum vs minimum) within the ETCs largely depend on cyclone depths. Both studies suggest changes in cloud and precipitating structures within the ETCs during cyclone evolution.…”

Impacts of Storm Track Variations on Wintertime Extreme Precipitation and Moisture Budgets over the Ohio Valley and Northwestern United States

“…Numerous case studies of hazardous weather for the winter over the United States demonstrate that these are mostly related to the passage of deep cyclones (e.g., Bosart 1981;Zhang et al 2002;Cardone et al 1996). Detailed statistical composites of extratropical cyclones have related the extreme precipitation to cyclone depths (Polly and Rossow 2016) or cyclone intensification (Rudeva and Gulev 2011). Over the U.S. west coast, many such events have been linked to atmospheric rivers (Ralph et al 2006;Guan et al 2010), which are also related to cyclones (Zhu and Newell 1994;Ralph et al 2004).…”