Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: R. E. Passarelli x
  • Refine by Access: All Content x
Clear All Modify Search
R. C. Srivastava
and
R. E. Passarelli

Abstract

The kinetic equation for the evolution of particle size spectra by condensation and coalescence is considered. The condensation rate, the rate of increase of the particle mass ẋ, is taken as (i) a(t)x and (ii) a(t), where a(t) is an arbitrary non-negative function of the time. In case (i) it is shown that, for a homogeneous kernel, the solution of the kinetic equation for condensation and coalescence can be reduced to that for pure coalescence by simple transformations. In case (ii) the solution is expressed as an infinite series, the terms of which involve convolutions of arbitrary order of the initial distribution and a function of the condensation rate. The central limit theorem of probability theory is used to obtain an expansion for the convolutions, and an approximate analytical expression for the sum of the infinite series is obtained for large x. A few numerical evaluations of the solutions are presented.

Full access
Richard E. Passarelli Jr.
and
Roscoe R. Braham Jr.

Radar and aircraft data are presented, in the form of case studies, for three shoreline-parallel snow bands that occurred over Lake Michigan. In all three cases a winter land breeze from one or both shores is shown to have an important role in organizing the low-level convergence and convective motions. These cases are compared with earlier studies of lake-effect snow bands on Lakes Erie and Ontario.

Full access
Marc A. Seltzer
,
R. E. Passarelli
, and
K. A. Emanuel

Abstract

Fifteen cases of banded and nonbanded precipitation not associated with surface frontal regions are presented. Results from the linear perturbation and parcel theories of symmetric instability are compared to the observed properties of these bands. Symmetric instability can explain many of the features of the bands considered in this study: all of the bands are aligned parallel to the thermal wind; strong shear and near-neutral static stabilities are observed when bands occur; multiple bands have a wavelength that is related to the depth of the unstable region and the slope of moist isentropic surfaces. However, the linear theory of symmetric instability assumes a basic state of unidirectional flow and thermal wind balance, while the observations indicate that in some cases these conditions are not met. This study supports the hypothesis that symmetric instability may be responsible for precipitation bands, but the comparison between theory and observations is hampered by the inability of the present theory to account for ageostrophic shear and curved flow, and our inability to access geostrophy via sparse soundings.

Full access