On the sensitivity of predictions of maritime cyclogenesis to convective precipitation and sea temperature

Abstract

To cite this article: Maurice Danard (1986) On the sensitivity of predictions of maritime cyclogenesis to convective precipitation and sea temperature, Atmosphere-Ocean, 24:1, 52-72, DOI: 10.1080DOI: 10. /07055900.1986 Convective Precipitation, SST and Predictions of Maritime Cyclogenesis / 53 1 IntroductionExtratropical cyclones over the oceans tend to develop faster, attain greater intensities, and be less accurately predicted than those over land. While it is unlikely that many forecasters responsible for maritime or coastal areas would dispute this statement, some references to support it may be found in Danard (1983Danard ( , 1985. Contributing factors are a smooth underlying surface, an abundant supply of heat and moisture, and sparsity of data. This paper is concerned with the effects of surface fluxes and convective precipitation. The importance of convective precipitation in the development of extratropical cyclones was noted by Tracton (1973). More recently, Smith et al. (1984) examined a winter cyclone over the United States and concluded that the bulk of the precipitation was convective rather than large-scale. In Section 2, a convective parametrization adapted from Kuo (1974) is included in an 8-level primitive equations model. Three methods are investigated of specifying the fraction of the moisture supply producing convective precipitation. These are tested for two 36-h periods of cyclogenesis over the northeastern Pacific Ocean as described in Sections 3 and 4.It is generally accepted that the CISK mechanism (conditional instability of the second kind) is important in the formation of tropical cyclones (Charney and Eliassen, 1964). In CISK, moisture convergence in the PBL and evaporation from the surface lead to condensation and liberation of latent heat, which drives the storm. If a depression moves over warmer water, the moisture supply will increase and the cyclone will intensify. The role of CISK in extratropical systems is not so clear, and this is examined in Section 5.

Synoptic aspects and physical processes in the rapidly intensifying cyclone of 6–8 March 1986

“…Reed (1979) and Mullen (1979) demonstrated that the development of polar lows is affected largely by a weakly-stratified lower troposphere. Danard and Ellenton (1980), Danard (1985) and Reed and Albright (1986) showed that surface fluxes can produce initial temperature and moisture stratifications that favour cyclogenesis along the coastal regions.…”

The importance of diabatic processes for the dynamics of synoptic-scale extratropical weather systems—a review

“…The simulations by Dell' Osso and Radinovic (1984) for an Alpine lee cyclone revealed an even slightly more intense cyclone in the dry compared to the full-physics simulation. Danard (1986) to strongly increased surface precipitation and an almost doubled cyclone deepening, indicating a high sensitivity of cyclone deepening to sea surface temperature and in turn surface fluxes. In contrast, the short-term surface fluxes were not relevant for the explosively deepening North Pacific cyclone simulated by Kuo and Reed (1988).…”

A numerical study of the windstorm Klaus: sensitivity to sea surface temperature

“…Lambert [1996] found a positive correlation between the number of northern hemisphere Pacific "intense" extra-tropical cyclones and SST gradients and a weak correlation in the Atlantic region. A sea surface with high temperature, beneath a cold atmosphere provides an abundant supply of heat and moisture that has a significant effect on the cyclone development [Danard 1983[Danard , 1986. The latent heat release associated with condensation of water vapour definitely plays an important role through convection and/or the moist baroclinic processes [e.g.…”

“…Emanuel 2005], however the effects of SST on extra-tropical cyclones has been the object of only a few case studies [e.g. Danard 1986, Giordani and Caniaux 2001, Ren et al 2004, Booth et al 2012, Ludwig et al 2014]. Indirect assessment of SST impact on extra-tropical cyclone intensity can be found in a few climatological studies, where a moderate positive impact of SST on the number of intense storms is found [Semmler et al 2008a].…”