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J. R. Drummond
and
A. Ashton

Abstract

The pressure modulator is extensively used in atmospheric measurements but is not well characterized in terms of its spectroscopic operation. A series of measurements on a carbon monoxide radiometer is described and comparisons are made with theoretical calculations for the same conditions. Agreement is found between theory and experiment for normalized cell transmissions. Diode laser spectroscopic measurements are also found to give satisfactory agreement if there is some temperature cycling in the modulator cell. Some variation is found in the absolute measurements of equivalent width. The possible reasons for this discrepancy are discussed.

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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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Vincent M. Brown
,
Barry D. Keim
,
William D. Kappel
,
Douglas M. Hultstrand
,
Ashton G. Peyrefitte Jr.
,
Alan W. Black
,
Kristi M. Steinhilber
, and
Geoffrey A. Muhlestein

Abstract

This study examines the spatiotemporal characteristics of the historic 1014 August 2016 south-central Louisiana precipitation event. The storm was the result of a moisture-rich, tropical low pressure system, also known as a tropical easterly wave, that slowly tracked westward along the Gulf Coast from Florida to Texas. Once over south-central Louisiana, the storm was able to take advantage of anomalously high precipitable water, broad low-level instability, and continuous moisture inflow from the Gulf of Mexico to produce historic rainfall. Totals exceeded 254 mm (10 in.) for much of southern Louisiana, while locations adjacent to Baton Rouge and Lafayette received upward of 635 mm (25 in.). One station measured a 48-h rainfall total of 797.3 mm (31.39 in.)—the greatest 48-h total on record for Louisiana. Using calibrated radar data, the Storm Precipitation Analysis System (SPAS) revealed that one location likely received >864 mm (34 in.) of precipitation during the duration of the storm, well over the estimated 1000-yr return interval. A synoptic discussion of the event and analysis of the storm’s recurrence interval helps place this storm in a historical context.

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