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Lloyd J. Anderson

Measurements on rainfall near Hilo, Hawaii are described. Quartile deviations of drop-size distributions are plotted versus rainfall intensity. Comparison is made with similar data of Laws and Parsons, and certain similarities and differences are pointed out.

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Lloyd J. Anderson

Meteorological equipment for taking detailed temperature and humidity soundings to 3000 ft. altitude is discussed. It consists of a captive balloon wired-sonde system using a ceramic temperature element and an electrolytic hygrometer strip. Similar equipment is also adapted for use in airplane soundings. Calibration techniques and results are discussed, together with a method for correcting the humidity strip to ± 1% R.H. Temperature accuracy is ± 0.1°C. The limitations of the balloon and airplane equipment are discussed and the two are found to be complementary.

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G. Vaughan
,
J. Methven
,
D. Anderson
,
B. Antonescu
,
L. Baker
,
T. P. Baker
,
S. P. Ballard
,
K. N. Bower
,
P. R. A. Brown
,
J. Chagnon
,
T. W. Choularton
,
J. Chylik
,
P. J. Connolly
,
P. A. Cook
,
R. J. Cotton
,
J. Crosier
,
C. Dearden
,
J. R. Dorsey
,
T. H. A. Frame
,
M. W. Gallagher
,
M. Goodliff
,
S. L. Gray
,
B. J. Harvey
,
P. Knippertz
,
H. W. Lean
,
D. Li
,
G. Lloyd
,
O. Martínez–Alvarado
,
J. Nicol
,
J. Norris
,
E. Öström
,
J. Owen
,
D. J. Parker
,
R. S. Plant
,
I. A. Renfrew
,
N. M. Roberts
,
P. Rosenberg
,
A. C. Rudd
,
D. M. Schultz
,
J. P. Taylor
,
T. Trzeciak
,
R. Tubbs
,
A. K. Vance
,
P. J. van Leeuwen
,
A. Wellpott
, and
A. Woolley

Abstract

The Diabatic Influences on Mesoscale Structures in Extratropical Storms (DIAMET) project aims to improve forecasts of high-impact weather in extratropical cyclones through field measurements, high-resolution numerical modeling, and improved design of ensemble forecasting and data assimilation systems. This article introduces DIAMET and presents some of the first results. Four field campaigns were conducted by the project, one of which, in late 2011, coincided with an exceptionally stormy period marked by an unusually strong, zonal North Atlantic jet stream and a succession of severe windstorms in northwest Europe. As a result, December 2011 had the highest monthly North Atlantic Oscillation index (2.52) of any December in the last 60 years. Detailed observations of several of these storms were gathered using the U.K.’s BAe 146 research aircraft and extensive ground-based measurements. As an example of the results obtained during the campaign, observations are presented of Extratropical Cyclone Friedhelm on 8 December 2011, when surface winds with gusts exceeding 30 m s–1 crossed central Scotland, leading to widespread disruption to transportation and electricity supply. Friedhelm deepened 44 hPa in 24 h and developed a pronounced bent-back front wrapping around the storm center. The strongest winds at 850 hPa and the surface occurred in the southern quadrant of the storm, and detailed measurements showed these to be most intense in clear air between bands of showers. High-resolution ensemble forecasts from the Met Office showed similar features, with the strongest winds aligned in linear swaths between the bands, suggesting that there is potential for improved skill in forecasts of damaging winds.

Open access