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J. R. Drummond
,
D. Turner
, and
A. Ashton

Abstract

The determination of the horizontal attitude of a balloon-borne, infrared, limb-scanning radiometer is discussed. In particular, the relationship between scan-angle, as measured by the instrument, and the tangent height of the ray path through the atmosphere is considered. The instrument is unusual in that it scans in two opposite directions. This property is used to derive the scan angle from the same radiance profiles, which are used to determine the constituent profiles, subject only to the assumptions that the attitude is steady, the stratosphere is locally horizontally homogeneous, and the instrumental optical alignment is correct.

The results of this determination for the first flight of the Toronto Balloon Radiometer are compared to previous methods of determining the instrumental scan angle and are found to agree to the accuracy with which the comparisons are made. Techniques by which the accuracy and resolution of the two-sided attitude determination could be improved are discussed.

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J. T. Pisano
,
J. W. Drummond
, and
D. R. Hastie

Abstract

A new lightweight NO2 instrument that can be flown from a tethered balloon to give vertical NO2 profiles is described. The detection principle is the chemiluminescent reaction between NO2 and a solution of luminol. The instrument is integrated with a radiosonde to also give temperature, humidity, and pressure data. Tests show the instrument is linear from 2.8 to 75 ppbv but nonlinear below 2.8 ppbv. A calibration curve is determined. The sensitivity varies directly with pressure and it has a −3.5% per degree temperature dependence. Data from trial flights as part of the PACIFIC'93 field study show NO2 data from the surface to 900 m.

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Glen Lesins
,
Thomas J. Duck
, and
James R. Drummond

Abstract

Using 22 Canadian radiosonde stations from 1971 to 2010, the annually averaged surface air temperature trend amplification ranged from 1.4 to 5.2 relative to the global average warming of 0.17°C decade−1. The amplification factors exhibit a strong latitudinal dependence varying from 2.6 to 5.2 as the latitude increases from 50° to 80°N. The warming trend has a strong seasonal dependence with the greatest warming taking place from September to April. The monthly variations in the warming trend are shown to be related to the surface-based temperature inversion strength and the mean monthly surface air temperatures.

The surface energy balance (SEB) equation is used to relate the response of the surface temperature to changes in the surface energy fluxes. Based on the SEB analysis, there are four contributing factors to Arctic amplification: 1) a larger change in net downward radiation at the Arctic surface compared to the global average; 2) a larger snow and soil conductive heat flux change than the global average; 3) weaker sensible and latent heat flux responses that result in a larger surface temperature response in the Arctic; and 4) a colder skin temperature compared to the global average, which forces a larger surface warming to achieve the same increase in upward longwave radiation. The observed relationships between the Canadian station warming trends and both the surface-based inversion strength and the surface air temperature are shown to be consistent with the SEB analysis. Measurements of conductive flux were not available at these stations.

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Dieter Kley
,
E.J. Stone
,
W.R. Henderson
,
J.W. Drummond
,
W.J. Harrop
,
A.L. Schmeltekopf
,
T.L. Thompson
, and
R.H. Winkler

Abstract

The results of four balloon flights of the NOAA ultraviolet fluorescence stratospheric water vapor instrument are presented. A series of improvements in the instrument has brought results which are credibly free from contamination by outgassing. The results are in essential agreement with the extensive soundings by H.J. Mastenbrook. The minimum water vapor mixing ratio occurs 2–3 km above the tropopause in both tropical and temperature latitudes. Our measured minimum values were 2.6 ppmv over Brazil (5°S) and 3.6 ppmv over Wyoming (41°N), with an estimated total error of 20%. This degree of dryness permits the conclusion that the global circulation originally proposed by Brewer is correct; i.e., that air enters the stratosphere from the troposphere in substantial quantities only through the tropical tropopause. This general circulation must apply to all other trace gases of tropospheric origin as well. The carbon monoxide measurements of Seiler support the conclusion.

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Fiona J. Drummond
,
R. R. Rogers
,
S. A. Cohn
,
W. L. Ecklund
,
D. A. Carter
, and
J. S. Wilson

Abstract

The authors derive a relationship between the vertical Doppler spectrum of the rain just below the radar bright band and that of the snow just above. It neglects vertical air motions and assumes that each snowflake simply melts to form a raindrop of the same mass, disregarding other possible effects such as aggregation to form larger particles or breakup to create smaller ones. The relationship shows that, regardless of the dependence of particle fallspeed on size, the product of the equivalent reflectivity factor and the mean Doppler velocity of the snow is proportional to the same product for the rain, with a constant proportionality factor of 0.23, which equals the ratio of the dielectric factors of ice and water. Observed values of the reflectivity and mean Doppler velocity above and below the melting layer sometimes agree with this theoretical prediction but more often deviate from it in ways that may be interpreted as indicating the predominance of either aggregation or breakup processes. The data suggest that aggregation is occurring much of the time in the melting layer but that breakup effects become dominant in heavy precipitation. The analysis is extended by assuming relations between particle size and fallspeed for rain and snow. This enables the comparison of measured spectra with those derived theoretically. A simple allowance for aggregation or breakup in the spectral transformation from snow to rain is found to give improved spectral agreement in cases where these effects are indicated.

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G. J. Nott
,
T. J. Duck
,
J. G. Doyle
,
M. E. W. Coffin,
,
C. Perro
,
C. P. Thackray
,
J. R. Drummond
,
P. F. Fogal
,
E. McCullough
, and
R. J. Sica

Abstract

A Rayleigh–Mie–Raman lidar has been installed and is operating in the Polar Environment Atmospheric Research Laboratory at Eureka in the High Arctic (79°59′N, 85°56′W) as part of the Canadian Network for the Detection of Atmospheric Change. The lidar operates in both the visible and ultraviolet and measures aerosol backscatter and extinction coefficients, depolarization ratio, tropospheric temperature, and water vapor mixing ratio. Variable field of view, aperture, and filtering allow fine-tuning of the instrument for different atmospheric conditions. Because of the remote location, operations are carried out via a satellite link. The instrument is introduced along with the measurement techniques utilized and interference filter specifications. The temperature dependence of the water vapor signal depends on the filter specifications, and this is discussed in terms of minimizing the uncertainty of the water vapor mixing ratio product. Finally, an example measurement is presented to illustrate the potential of this instrument for studying the Arctic atmosphere.

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M. N. Deeter
,
G. L. Francis
,
D. P. Edwards
,
J. C. Gille
,
E. McKernan
, and
James R. Drummond

Abstract

Optical bandpass filters in the Measurements of Pollution in the Troposphere (MOPITT) satellite remote sensing instrument selectivity limit the throughput radiance to absorptive spectral bands associated with the satellite-observed trace gases CO and CH4. Precise specification of the spectral characteristics of these filters is required to optimize retrieval accuracy. The effects and potential causes of spectral shifts in the optical bandpass filter profiles are described. Specifically, a shift in the assumed bandpass profile produces a relative bias between the calibrated satellite radiances and the corresponding values calculated by an instrument-specific forward radiative transfer model. Conversely, it is shown that the observed bias (as identified and quantified using operational MOPITT satellite radiance data) can be used to determine the relative spectral shift between the nominal (prelaunch) filter profiles and the true operational (in orbit) profiles. Revising both the radiance calibration algorithm and the forward radiative transfer model to account for the revised filter profiles effectively eliminates the radiance biases.

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J. E. Harries
,
J. E. Russell
,
J. A. Hanafin
,
H. Brindley
,
J. Futyan
,
J. Rufus
,
S. Kellock
,
G. Matthews
,
R. Wrigley
,
A. Last
,
J. Mueller
,
R. Mossavati
,
J. Ashmall
,
E. Sawyer
,
D. Parker
,
M. Caldwell
,
P M. Allan
,
A. Smith
,
M. J. Bates
,
B. Coan
,
B. C. Stewart
,
D. R. Lepine
,
L. A. Cornwall
,
D. R. Corney
,
M. J. Ricketts
,
D. Drummond
,
D. Smart
,
R. Cutler
,
S. Dewitte
,
N. Clerbaux
,
L. Gonzalez
,
A. Ipe
,
C. Bertrand
,
A. Joukoff
,
D. Crommelynck
,
N. Nelms
,
D. T. Llewellyn-Jones
,
G. Butcher
,
G. L. Smith
,
Z. P Szewczyk
,
P E. Mlynczak
,
A. Slingo
,
R. P. Allan
, and
M. A. Ringer

This paper reports on a new satellite sensor, the Geostationary Earth Radiation Budget (GERB) experiment. GERB is designed to make the first measurements of the Earth's radiation budget from geostationary orbit. Measurements at high absolute accuracy of the reflected sunlight from the Earth, and the thermal radiation emitted by the Earth are made every 15 min, with a spatial resolution at the subsatellite point of 44.6 km (north–south) by 39.3 km (east–west). With knowledge of the incoming solar constant, this gives the primary forcing and response components of the top-of-atmosphere radiation. The first GERB instrument is an instrument of opportunity on Meteosat-8, a new spin-stabilized spacecraft platform also carrying the Spinning Enhanced Visible and Infrared (SEVIRI) sensor, which is currently positioned over the equator at 3.5°W. This overview of the project includes a description of the instrument design and its preflight and in-flight calibration. An evaluation of the instrument performance after its first year in orbit, including comparisons with data from the Clouds and the Earth's Radiant Energy System (CERES) satellite sensors and with output from numerical models, are also presented. After a brief summary of the data processing system and data products, some of the scientific studies that are being undertaken using these early data are described. This marks the beginning of a decade or more of observations from GERB, as subsequent models will fly on each of the four Meteosat Second Generation satellites.

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Taneil Uttal
,
Sandra Starkweather
,
James R. Drummond
,
Timo Vihma
,
Alexander P. Makshtas
,
Lisa S. Darby
,
John F. Burkhart
,
Christopher J. Cox
,
Lauren N. Schmeisser
,
Thomas Haiden
,
Marion Maturilli
,
Matthew D. Shupe
,
Gijs De Boer
,
Auromeet Saha
,
Andrey A. Grachev
,
Sara M. Crepinsek
,
Lori Bruhwiler
,
Barry Goodison
,
Bruce McArthur
,
Von P. Walden
,
Edward J. Dlugokencky
,
P. Ola G. Persson
,
Glen Lesins
,
Tuomas Laurila
,
John A. Ogren
,
Robert Stone
,
Charles N. Long
,
Sangeeta Sharma
,
Andreas Massling
,
David D. Turner
,
Diane M. Stanitski
,
Eija Asmi
,
Mika Aurela
,
Henrik Skov
,
Konstantinos Eleftheriadis
,
Aki Virkkula
,
Andrew Platt
,
Eirik J. Førland
,
Yoshihiro Iijima
,
Ingeborg E. Nielsen
,
Michael H. Bergin
,
Lauren Candlish
,
Nikita S. Zimov
,
Sergey A. Zimov
,
Norman T. O’Neill
,
Pierre F. Fogal
,
Rigel Kivi
,
Elena A. Konopleva-Akish
,
Johannes Verlinde
,
Vasily Y. Kustov
,
Brian Vasel
,
Viktor M. Ivakhov
,
Yrjö Viisanen
, and
Janet M. Intrieri

Abstract

International Arctic Systems for Observing the Atmosphere (IASOA) activities and partnerships were initiated as a part of the 2007–09 International Polar Year (IPY) and are expected to continue for many decades as a legacy program. The IASOA focus is on coordinating intensive measurements of the Arctic atmosphere collected in the United States, Canada, Russia, Norway, Finland, and Greenland to create synthesis science that leads to an understanding of why and not just how the Arctic atmosphere is evolving. The IASOA premise is that there are limitations with Arctic modeling and satellite observations that can only be addressed with boots-on-the-ground, in situ observations and that the potential of combining individual station and network measurements into an integrated observing system is tremendous. The IASOA vision is that by further integrating with other network observing programs focusing on hydrology, glaciology, oceanography, terrestrial, and biological systems it will be possible to understand the mechanisms of the entire Arctic system, perhaps well enough for humans to mitigate undesirable variations and adapt to inevitable change.

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