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  • Author or Editor: C. G. Mohr x
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C. G. Mohr
and
R. L. Vaughan

Abstract

A fast and efficient procedure has been developed which allows the systematic interpolation of digital reflectivity data from radar space into Cartesian space. The algorithm is designed so that only one ordered pass through the original PPI scan data is necessary to complete the interpolation process. As a result, 100 cross sections may be interpolated and displayed for approximately five times the cost of producing PPI plots for the same volume. Computer-generated displays produced by the system include contoured and gray-scale plots of orthogonal sections and perspective images of two- and three-dimensional reflectivity surfaces.

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T. L. Clark
,
F. I. Harris
, and
C. G. Mohr

Abstract

Simulations from a time-dependent model of moist convection have been used to assess magnitudes of errors in the estimates of derived wind fields from the synthesis of data from a network of Doppler radars. The two types of errors considered are, first, those due to temporal changes in the scales of deep convection resolved by the model, and second, those due to the random contributions of radial velocity estimates by scales smaller than model resolution (noise). Due to the coarse spatial resolution of the model, much of the assumed noise error is due to spatial scales between the model's resolution (∼1 km) and the Doppler radar sampling scale (∼100 m) and should not be considered in reality as “white” noise with respect to the radar sampling problem. The results presented in this paper must be interpreted only in terms of wind estimates derived by using radar sample volumes comparable to the models resolution. Much higher spatial resolution experiments with the model are necessary to clearly delineate the differences between temporal and noise errors for scales larger than the typical radar sampling volumes.

The temporal errors for the resolved scales of the model using a 3 min scan time were found to be less than those due to noise and in general quite tolerable in magnitude for three or more radars. A dual-Doppler analysis in x, y, z Cartesian space (as opposed to x, y, elevation angle coplane analysis) was considered. In this case the derived errors (in the steady state) were found to be significantly large.

The effects of scan time and number of radars were assessed and two methods of reducing temporal errors were investigated.

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J. C. Fankhauser
,
C. J. Biter
,
C. G. Mohr
, and
R. L. Vaughan

Abstract

Objective numerical techniques are applied in analyzing constant altitude aircraft measurements obtained from coordinated research flights in thunderstorm inflow regions. The approach combines meteorological and flight track data from dual or single aircraft missions in a common frame of reference and transforms the observations from original analogue format to horizontal two-dimensional Cartesian coordinates. Operational procedures guiding the data collection, intercomparison techniques for refining instrument calibrations and corrections for aircraft navigation errors are all considered.

Results of the interpolations are judged in the context of the storms' associated radar echo features. Primary applications include calculation of water vapor influx in cloud base updrafts. Evidence indicates that the fullest exploitation of the inflow mapping will come through combining kinematic fields observed concurrently by aircraft and multiple Doppler radars.

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J. T. Pasquier
,
R. O. David
,
G. Freitas
,
R. Gierens
,
Y. Gramlich
,
S. Haslett
,
G. Li
,
B. Schäfer
,
K. Siegel
,
J. Wieder
,
K. Adachi
,
F. Belosi
,
T. Carlsen
,
S. Decesari
,
K. Ebell
,
S. Gilardoni
,
M. Gysel-Beer
,
J. Henneberger
,
J. Inoue
,
Z. A. Kanji
,
M. Koike
,
Y. Kondo
,
R. Krejci
,
U. Lohmann
,
M. Maturilli
,
M. Mazzolla
,
R. Modini
,
C. Mohr
,
G. Motos
,
A. Nenes
,
A. Nicosia
,
S. Ohata
,
M. Paglione
,
S. Park
,
R. E. Pileci
,
F. Ramelli
,
M. Rinaldi
,
C. Ritter
,
K. Sato
,
T. Storelvmo
,
Y. Tobo
,
R. Traversi
,
A. Viola
, and
P. Zieger

Abstract

The Arctic is warming at more than twice the rate of the global average. This warming is influenced by clouds, which modulate the solar and terrestrial radiative fluxes and, thus, determine the surface energy budget. However, the interactions among clouds, aerosols, and radiative fluxes in the Arctic are still poorly understood. To address these uncertainties, the Ny-Ålesund Aerosol Cloud Experiment (NASCENT) study was conducted from September 2019 to August 2020 in Ny-Ålesund, Svalbard. The campaign’s primary goal was to elucidate the life cycle of aerosols in the Arctic and to determine how they modulate cloud properties throughout the year. In situ and remote sensing observations were taken on the ground at sea level, at a mountaintop station, and with a tethered balloon system. An overview of the meteorological and the main aerosol seasonality encountered during the NASCENT year is introduced, followed by a presentation of first scientific highlights. In particular, we present new findings on aerosol physicochemical and molecular properties. Further, the role of cloud droplet activation and ice crystal nucleation in the formation and persistence of mixed-phase clouds, and the occurrence of secondary ice processes, are discussed and compared to the representation of cloud processes within the regional Weather Research and Forecasting Model. The paper concludes with research questions that are to be addressed in upcoming NASCENT publications.

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S. I. Bohnenstengel
,
S. E. Belcher
,
A. Aiken
,
J. D. Allan
,
G. Allen
,
A. Bacak
,
T. J. Bannan
,
J. F. Barlow
,
D. C. S. Beddows
,
W. J. Bloss
,
A. M. Booth
,
C. Chemel
,
O. Coceal
,
C. F. Di Marco
,
M. K. Dubey
,
K. H. Faloon
,
Z. L. Fleming
,
M. Furger
,
J. K. Gietl
,
R. R. Graves
,
D. C. Green
,
C. S. B. Grimmond
,
C. H. Halios
,
J. F. Hamilton
,
R. M. Harrison
,
M. R. Heal
,
D. E. Heard
,
C. Helfter
,
S. C. Herndon
,
R. E. Holmes
,
J. R. Hopkins
,
A. M. Jones
,
F. J. Kelly
,
S. Kotthaus
,
B. Langford
,
J. D. Lee
,
R. J. Leigh
,
A. C. Lewis
,
R. T. Lidster
,
F. D. Lopez-Hilfiker
,
J. B. McQuaid
,
C. Mohr
,
P. S. Monks
,
E. Nemitz
,
N. L. Ng
,
C. J. Percival
,
A. S. H. Prévôt
,
H. M. A. Ricketts
,
R. Sokhi
,
D. Stone
,
J. A. Thornton
,
A. H. Tremper
,
A. C. Valach
,
S. Visser
,
L. K. Whalley
,
L. R. Williams
,
L. Xu
,
D. E. Young
, and
P. Zotter

Abstract

Air quality and heat are strong health drivers, and their accurate assessment and forecast are important in densely populated urban areas. However, the sources and processes leading to high concentrations of main pollutants, such as ozone, nitrogen dioxide, and fine and coarse particulate matter, in complex urban areas are not fully understood, limiting our ability to forecast air quality accurately. This paper introduces the Clean Air for London (ClearfLo; www.clearflo.ac.uk) project’s interdisciplinary approach to investigate the processes leading to poor air quality and elevated temperatures.

Within ClearfLo, a large multi-institutional project funded by the U.K. Natural Environment Research Council (NERC), integrated measurements of meteorology and gaseous, and particulate composition/loading within the atmosphere of London, United Kingdom, were undertaken to understand the processes underlying poor air quality. Long-term measurement infrastructure installed at multiple levels (street and elevated), and at urban background, curbside, and rural locations were complemented with high-resolution numerical atmospheric simulations. Combining these (measurement–modeling) enhances understanding of seasonal variations in meteorology and composition together with the controlling processes. Two intensive observation periods (winter 2012 and the Summer Olympics of 2012) focus upon the vertical structure and evolution of the urban boundary layer; chemical controls on nitrogen dioxide and ozone production—in particular, the role of volatile organic compounds; and processes controlling the evolution, size, distribution, and composition of particulate matter. The paper shows that mixing heights are deeper over London than in the rural surroundings and that the seasonality of the urban boundary layer evolution controls when concentrations peak. The composition also reflects the seasonality of sources such as domestic burning and biogenic emissions.

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