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R. J. List

Collections of radioactive debris were made daily at 120 Weather Bureau stations throughout the United States during the atomic test series in Nevada in the Spring of 1952. The measuring techniques employed and the meteorological factors involved in the transport and deposition of debris are discussed. Several examples of the relation of computed meteorological trajectories to actual observations of debris are given.

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Roland List
and
J. R. Gillespie

Abstract

No abstract available.

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Roland List
and
J. R. Gillespie

Abstract

A numerical model was set up to study the evolution of raindrop spectra by collision-induced breakup as measured in the laboratory. The main conclusion is that drops with diameters larger than 2-3 mm, failing in a population of smaller drops typical of natural rain, break up in comparatively short times (1–5 min in rainfalls of 100 mm h−1). The presence of large drops (4–6 mm) in (cold) rain produced by the Wegener-Bergeron-Findeisen mechanism through melting of ice particles can be attributed to the short time available for large drops to break up in sufficient numbers during the time of fall after melting. Large drops are scarce in (steady-state) warm rain because they break up in collisions and rarely reach diameters larger than 2.5 mm. Hence, the standard notion of a critical diameter of 5–6 mm which raindrops are supposed to reach before breakup due to aerodynamic instability is no longer acceptable.

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R. List
,
P. H. Schuepp
, and
R. G. J. Methot

Abstract

Calculations are presented of the relative contributions of heat exchange by conduction and convection, by evaporation, and by the supercooling of accreted drops to the total heat exchange of growing spherical hailstones. They reveal the regions of dominance of the different ratios for various icing conditions in a model cloud and in laboratory experiments. As an additional result, it can be shown that transfer ratios occurring in hail clouds can only partly be simulated in experiments at constant pressure, but a restricted imitation at constant pressure is possible. These ratios are also considered to represent new parameters for future experiments about the relationship between icing conditions and resulting hailstone shells.

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L. Machta
,
H. L. Hamilton Jr.
,
L. F. Hubert
,
R. J. List
, and
K. M. Nagler

Abstract

The primary purpose of this article is the documentation of radioactivity data collected by airborne equipment during the first of the Nevada atomic tests. While absolute magnitudes of activity are not available, the relative values are useful in checking meteorological trajectories and in making crude estimates of lateral diffusion.

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Greg M. McFarquhar
,
Roland List
,
David R. Hudak
,
Robert P. Nissen
,
J. S. Dobbie
,
N. P. Tung
, and
T. S. Kang

Abstract

During the Joint Tropical Rain Experiment of the Malaysian Meteorological Service and the University of Toronto, pulsating raindrop ensembles, hereafter pulses, were observed in and around Penang Island. Using a Doppler radar on 25 October 1990, a periodic variation of precipitation aloft 30 km from the radar site, with an approximate 8-min period, was established and seemed to be caused by the evolution and motion of horizontal inhomogeneities existing within the same cell. On 30 October 1990, using a new volume scanning strategy with a repetition cycle of 3.5 min, pulsations of the same frequency were observed up to 3 km above the radar and at the ground by a disdrometer. High concentrations of large drops were followed by high concentrations of successively smaller drops at the ground. This provides observational evidence to support the recent argument for using a time-varying release of precipitation-sized particles to model observed pulsating rainfall.

Many cases of nonsteady rain from convective clouds displayed repetition periods of between 8 and 25 min.

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T. J. Ansell
,
P. D. Jones
,
R. J. Allan
,
D. Lister
,
D. E. Parker
,
M. Brunet
,
A. Moberg
,
J. Jacobeit
,
P. Brohan
,
N. A. Rayner
,
E. Aguilar
,
H. Alexandersson
,
M. Barriendos
,
T. Brandsma
,
N. J. Cox
,
P. M. Della-Marta
,
A. Drebs
,
D. Founda
,
F. Gerstengarbe
,
K. Hickey
,
T. Jónsson
,
J. Luterbacher
,
Ø. Nordli
,
H. Oesterle
,
M. Petrakis
,
A. Philipp
,
M. J. Rodwell
,
O. Saladie
,
J. Sigro
,
V. Slonosky
,
L. Srnec
,
V. Swail
,
A. M. García-Suárez
,
H. Tuomenvirta
,
X. Wang
,
H. Wanner
,
P. Werner
,
D. Wheeler
, and
E. Xoplaki

Abstract

The development of a daily historical European–North Atlantic mean sea level pressure dataset (EMSLP) for 1850–2003 on a 5° latitude by longitude grid is described. This product was produced using 86 continental and island stations distributed over the region 25°–70°N, 70°W–50°E blended with marine data from the International Comprehensive Ocean–Atmosphere Data Set (ICOADS). The EMSLP fields for 1850–80 are based purely on the land station data and ship observations. From 1881, the blended land and marine fields are combined with already available daily Northern Hemisphere fields. Complete coverage is obtained by employing reduced space optimal interpolation. Squared correlations (r2) indicate that EMSLP generally captures 80%–90% of daily variability represented in an existing historical mean sea level pressure product and over 90% in modern 40-yr European Centre for Medium-Range Weather Forecasts Re-Analyses (ERA-40) over most of the region. A lack of sufficient observations over Greenland and the Middle East, however, has resulted in poorer reconstructions there. Error estimates, produced as part of the reconstruction technique, flag these as regions of low confidence. It is shown that the EMSLP daily fields and associated error estimates provide a unique opportunity to examine the circulation patterns associated with extreme events across the European–North Atlantic region, such as the 2003 heat wave, in the context of historical events.

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