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A. R. Ehsani, J. A. Reagan, and W. H. Erxleben

Abstract

An automated multichannel solar radiometer has been designed and fabricated by the Atmospheric Remote Sensing Laboratory at The University of Arizona. The automated radiometer has 10 separate silicon-photodiode-based channels that allow near-simultaneous solar spectral measurements through narrow bandpass filters (approximately 10 nm) from the visible to near-IR regions. The photodiode detectors are temperature stabilized using a heating temperature controller circuit. The instrument is pointed toward the sun via an autotracking system that actively tracks the sun with a ±0.05° tracking accuracy. The instrument can continuously collect data for about 22 h at once per minute sample rate. This paper presents instrument design features as well as some performance and experimental results for the automated solar radiometer.

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K. J. Thome, B. M. Herman, and J. A. Reagan

Abstract

A method of determining precipitable water to within 10% from solar radiometer data has been developed. The method uses a modified Langley technique to obtain the water vapor optical depth, and a model developed at the University of Arizona is used to convert this to a precipitable water amount. The method is applied to two-and three-channel radiometric data and is compared to results obtained from empirical methods and to radiosonde data.

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J. D. Spinhirne, J. A. Reagan, and B. M. Herman

Abstract

Vertical profiles of aerosol extinction and backscatter in the troposphere are obtained from multizenith angle lidar measurements. A direct slant path solution was found to be not possible due to horizontal inhomogeneity of the atmosphere. Regression analysis with respect to zenith angle for a layer integration of the angle-dependent lidar equation was thus employed to determine the optical thickness and aerosol extinction-to-backscatter ratio for defined atmospheric layers, and subsequently, cross-section profiles could be evaluated. Measurements were made with an elastic backscatter ruby lidar system with calibration by a standard target procedure. The results from 20 measurement cases are presented. For layer-aerosol optical thicknesses >0.04, useful results were obtained, and corroboration by solar radiometer aerosol optical depth data was found. The mean mixed-layer aerosol extinction-to-backscatter ratio for the measurements was 19.5 sr with a standard deviation of 8.3 sr. With the use of an aerosol size distribution inverted from wavelength-dependent solar aerosol optical depth data, the measured extinction-to-backscatter ratio was compared to Mie theory calculations, and the imaginary index giving best agreement was determined. A maximum upper limit of 0.015 was indicated for the aerosol imaginary index. but the mean result was 0.003 for a real index of 1.52.

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L. W. Thomason, B. M. Herman, and J. A. Reagan

Abstract

The effect of vertical inhomogeneities of atmospheric attenuators upon determinations of air mass and upon Langley plot determinations of the extra-atmospheric solar irradiance is examined and found to be significant, especially when accuracies of 0.1% are required, as in our current solar monitoring program. Ozone air mass values are found to differ greatly from those of the homogeneously mixed atmosphere for zenith angles greater than 60°.

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D. E. Flittner, B. M. Herman, K. J. Thome, J. M. Simpson, and J. A. Reagan

Abstract

A second-derivative smoothing technique, commonly used in inversion work, is applied to the problem of inferring total columnar ozone amounts and aerosol optical depths. The application is unique in that the unknowns (i.e., total columnar ozone and aerosol optical depth) may be solved for directly without employing standard inversion methods. It is shown, however, that by employing inversion constraints, better solutions are normally obtained.

The current method requires radiometric measurements of total optical depth through the Chappuis ozone band. It assumes no a priori shape for the aerosol optical depth versus wavelength profile and makes no assumptions about the ozone amount. Thus, the method is quite versatile and able to deal with varying total ozone and various aerosol size distributions. The technique is applied first in simulation, then to 119 days of measurements taken in Tucson, Arizona, that are compared to TOMS values for the same dates. The technique is also applied to two measurements taken at Mauna Loa, Hawaii, for which Dobson ozone values are available in addition to the TOMS values, and the results agree to within 15%.

It is also shown through simulations that additional information can be obtained from measurements outside the Chappuis band. This approach reduces the bias and spread of the estimated total ozone and is unique in that it uses measurements from both the Chappuis and Huggins absorption bands.

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J. A. Reagan, J. D. Spinhirne, D. M. Byrne, D. W. Thomson, R. G. De Pena, and Y. Mamane

Abstract

Particulate size and height distributions, complex refractive index and mass loading have been measured and inferred from direct aircraft and indirect lidar-solar radiometer observations made during a unique joint experiment conducted the week of 18 November 1974 in Tucson, Ariz. The aircraft and lidar-solar radiometer measurements were first analyzed independently and the results were then intercompared. Vertical profiles of particulate extinction obtained from the lidar (monostatic) and aircraft measurements were found to be in excellent agreement on both a relative and absolute basis. Lidar (bistatic and monostatic) inferences of particulate mass loading agreed favorably with the aircraft mass monitor measurements. The aircraft and lidar (bistatic) size distribution determinations were found to be similar in shape and agreed in absolute value within an order of magnitude. The mean particle refractive index inferred from the lidar (bistatic) measurements (n = 1.40 − i0.000) agreed with the index of a significant fraction of the particles identified by electron microscope analysis of impactor samples collected with the aircraft.

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Kevin S. Repasky, John A. Reagan, Amin R. Nehrir, David S. Hoffman, Michael J. Thomas, John L. Carlsten, Joseph A. Shaw, and Glenn E. Shaw

Abstract

Coordinated observational data of atmospheric aerosols were collected over a 24-h period between 2300 mountain daylight time (MDT) on 27 August 2009 and 2300 MDT on 28 August 2009 at Bozeman, Montana (45.66°N, 111.04°W, elevation 1530 m) using a collocated two-color lidar, a diode-laser-based water vapor differential absorption lidar (DIAL), a solar radiometer, and a ground-based nephelometer. The optical properties and spatial distribution of the atmospheric aerosols were inferred from the observational data collected using the collocated instruments as part of a closure experiment under dry conditions with a relative humidity below 60%. The aerosol lidar ratio and aerosol optical depth retrieved at 532 and 1064 nm using the two-color lidar and solar radiometer agreed with one another to within their individual uncertainties while the scattering component of the aerosol extinction measured using the nephelometer matched the scattering component of the aerosol extinction retrieved using the 532-nm channel of the two-color lidar and the single-scatter albedo retrieved using the solar radiometer. Using existing aerosol models developed with Aerosol Robotic Network (AERONET) data, a thin aerosol layer observed over Bozeman was most likely identified as smoke from forest fires burning in California; Washington; British Columbia, Canada; and northwestern Montana. The intrusion of the thin aerosol layer caused a change in the atmospheric radiative forcing by a factor of 1.8 ± 0.5 due to the aerosol direct effect.

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M. P. McCormick, D. M. Winker, E. V. Browell, J. A. Coakley, C. S. Gardner, R. M. Hoff, G. S. Kent, S. H. Melfi, R. T. Menzies, C. M. R. Piatt, D. A. Randall, and J. A. Reagan

The Lidar In-Space Technology Experiment (LITE) is being developed by NASA/Langley Research Center for a series of flights on the space shuttle beginning in 1994. Employing a three-wavelength Nd:YAG laser and a 1-m-diameter telescope, the system is a test-bed for the development of technology required for future operational spaceborne lidars. The system has been designed to observe clouds, tropospheric and stratospheric aerosols, characteristics of the planetary boundary layer, and stratospheric density and temperature perturbations with much greater resolution than is available from current orbiting sensors. In addition to providing unique datasets on these phenomena, the data obtained will be useful in improving retrieval algorithms currently in use. Observations of clouds and the planetary boundary layer will aid in the development of global climate model (GCM) parameterizations. This article briefly describes the LITE program and discusses the types of scientific investigations planned for the first flight.

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Gregory C. Johnson, Rick Lumpkin, Simone R. Alin, Dillon J. Amaya, Molly O. Baringer, Tim Boyer, Peter Brandt, Brendan R. Carter, Ivona Cetinić, Don P. Chambers, Lijing Cheng, Andrew U. Collins, Cathy Cosca, Ricardo Domingues, Shenfu Dong, Richard A. Feely, Eleanor Frajka-Williams, Bryan A. Franz, John Gilson, Gustavo Goni, Benjamin D. Hamlington, Josefine Herrford, Zeng-Zhen Hu, Boyin Huang, Masayoshi Ishii, Svetlana Jevrejeva, John J. Kennedy, Marion Kersalé, Rachel E. Killick, Peter Landschützer, Matthias Lankhorst, Eric Leuliette, Ricardo Locarnini, John M. Lyman, John J. Marra, Christopher S. Meinen, Mark A. Merrifield, Gary T. Mitchum, Ben I. Moat, R. Steven Nerem, Renellys C. Perez, Sarah G. Purkey, James Reagan, Alejandra Sanchez-Franks, Hillary A. Scannell, Claudia Schmid, Joel P. Scott, David A. Siegel, David A. Smeed, Paul W. Stackhouse, William Sweet, Philip R. Thompson, Joaquin A. Triñanes, Denis L. Volkov, Rik Wanninkhof, Robert A. Weller, Caihong Wen, Toby K. Westberry, Matthew J. Widlansky, Anne C. Wilber, Lisan Yu, and Huai-Min Zhang
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Molly Baringer, Mariana B. Bif, Tim Boyer, Seth M. Bushinsky, Brendan R. Carter, Ivona Cetinić, Don P. Chambers, Lijing Cheng, Sanai Chiba, Minhan Dai, Catia M. Domingues, Shenfu Dong, Andrea J. Fassbender, Richard A. Feely, Eleanor Frajka-Williams, Bryan A. Franz, John Gilson, Gustavo Goni, Benjamin D. Hamlington, Zeng-Zhen Hu, Boyin Huang, Masayoshi Ishii, Svetlana Jevrejeva, William E. Johns, Gregory C. Johnson, Kenneth S. Johnson, John Kennedy, Marion Kersalé, Rachel E. Killick, Peter Landschützer, Matthias Lankhorst, Tong Lee, Eric Leuliette, Feili Li, Eric Lindstrom, Ricardo Locarnini, Susan Lozier, John M. Lyman, John J. Marra, Christopher S. Meinen, Mark A. Merrifield, Gary T. Mitchum, Ben Moat, Didier Monselesan, R. Steven Nerem, Renellys C. Perez, Sarah G. Purkey, Darren Rayner, James Reagan, Nicholas Rome, Alejandra Sanchez-Franks, Claudia Schmid, Joel P. Scott, Uwe Send, David A. Siegel, David A. Smeed, Sabrina Speich, Paul W. Stackhouse Jr., William Sweet, Yuichiro Takeshita, Philip R. Thompson, Joaquin A. Triñanes, Martin Visbeck, Denis L. Volkov, Rik Wanninkhof, Robert A. Weller, Toby K. Westberry, Matthew J. Widlansky, Susan E. Wijffels, Anne C. Wilber, Lisan Yu, Weidong Yu, and Huai-Min Zhang
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