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James H. Mather

Abstract

The Atmospheric Radiation Measurement (ARM) program operates three climate observation stations in the tropical western Pacific region. One of these sites, located on Manus Island in Papua New Guinea, has been operating since 1996. The Manus ARM site includes an extensive array of instruments chosen to observe cloud properties, water vapor and temperature profiles, and the surface radiation budget. This dataset provides an opportunity to examine variability in tropical cloudiness on a wide range of time scales. The focus of this study is on the annual cycle. Analysis of cloud distribution and radiation data from Manus reveals a clear annual cycle in clouds associated with convective activity. The most convectively active period is found to be the Northern Hemisphere summer, while the least active period is the Northern Hemisphere autumn. Outgoing longwave radiation (OLR) data are also examined in order to relate observations at Manus with the surrounding region. Significant differences are found between the annual cycle at Manus and adjacent large islands within the Maritime Continent. Analysis of the combined ARM–OLR data suggests that during the Northern Hemisphere winter, a significant amount of the high clouds observed over Manus are associated with continental convection over the large Maritime Continent islands.

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James H. Mather and Jimmy W. Voyles

The Atmospheric Radiation Measurement (ARM) Climate Research Facility (www.arm.gov) provides atmospheric observations from diverse climatic regimes around the world. Because it is a U.S. Department of Energy (DOE) user facility, ARM data are freely available to anyone through the ARM Data Archive. With 20 years of operations, the facility recently added two mobile facilities and an aerial facility to its network of fixed-location sites. Research using ARM data has led to advances in areas ranging from radiative transfer to cloud microphysics. The American Recovery and Reinvestment Act of 2009 allowed ARM to enhance its observational capabilities with a broad array of new instruments at its fixed and mobile sites and the aerial facility. Instruments include scanning radars; water vapor, cloud/aerosol extinction, and Doppler lidars; aerosol instruments for measuring optical, physical, and chemical properties; and aircraft probes for measuring cloud and aerosol properties. Taking full advantage of these instruments will involve the development of complex data products. This work is underway but will benefit from engagement with the broader scientific community. This article describes the current status of the ARM research capabilities with an emphasis on developments over the past eight years since ARM was designated a DOE scientific user facility, reviews some of scientific advances made using the ARM Facility over the past two decades, and describes the new measurement capabilities and adaptations of the ARM facility to make effective use of these capabilities.

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William H. Brune, Philip S. Stevens, and James H. Mather

Abstract

The hydroxyl radical OH oxidizes many lime gases in the atmosphere. It initiates and then participates in chemical reactions that lead to such phenomena as photochemical smog, acid rain, and stratospheric ozone depletion. Because OH is so reactive, its volume mixing ratio is less than 1 part per trillion volume (pptv) throughout the troposphere. Its close chemical cousin, the hydroperoxyl radical HO2, participates in many reactions as well. The authors have developed an instrument capable of measuring OH and HO2 by laser-induced fluorescence in a detection chamber at low pressure. This prototype instrument is able to detect about 1.4 × 105 molecules cm−3 (0.005 pptv) of OH at the ground in a signal integration time of 30 s with negligible interferences. The absolute uncertainty is a factor of 1.5. This instrument is now being adapted to aircraft use for measurements throughout the troposphere.

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Sally A. McFarlane, James H. Mather, and Eli J. Mlawer
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Thomas P. Ackerman, Ted S. Cress, Wanda R. Ferrell, James H. Mather, and David D. Turner
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James Mather, Susannah Burrows, Duli Chand, Nancy Hess, Alexander Laskin, Allison McComiskey, Noopur Sharma, and John Shilling
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Peter T. May, James H. Mather, Geraint Vaughan, Christian Jakob, Greg M. McFarquhar, Keith N. Bower, and Gerald G. Mace

A comprehensive dataset describing tropical cloud systems and their environmental setting and impacts has been collected during the Tropical Warm Pool International Cloud Experiment (TWPICE) and Aerosol and Chemical Transport in Tropical Convection (ACTIVE) campaign in the area around Darwin, Northern Australia, in January and February 2006. The aim of the experiment was to observe the evolution of tropical cloud systems and their interaction with the environment within an observational framework optimized for a range of modeling activities with the goal of improving the representation of cloud and aerosol process in a range of models. The experiment design utilized permanent observational facilities in Darwin, including a polarimetric weather radar and a suite of cloud remote-sensing instruments. This was augmented by a dense network of soundings, together with radiation, flux, lightning, and remote-sensing measurements, as well as oceanographic observations. A fleet of five research aircraft, including two high-altitude aircraft, were taking measurements of fluxes, cloud microphysics, and chemistry; cloud radar and lidar were carried on a third aircraft. Highlights of the experiment include an intense mesoscale convective system (MCS) developed within the network, observations used to analyze the impacts of aerosol on convective systems, and observations used to relate cirrus properties to the parent storm properties.

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Peter T. May, James H. Mather, Geraint Vaughan, Keith N. Bower, Christian Jakob, Greg M. McFarquhar, and Gerald G. Mace
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Eugene E. Clothiaux, Kenneth P. Moran, Brooks E. Martner, Thomas P. Ackerman, Gerald G. Mace, Taneil Uttal, James H. Mather, Kevin B. Widener, Mark A. Miller, and Daniel J. Rodriguez

Abstract

During the past decade, the U.S. Department of Energy (DOE), through the Atmospheric Radiation Measurement (ARM) Program, has supported the development of several millimeter-wavelength radars for the study of clouds. This effort has culminated in the development and construction of a 35-GHz radar system by the Environmental Technology Laboratory (ETL) of the National Oceanic and Atmospheric Administration (NOAA). Radar systems based on the NOAA ETL design are now operating at the DOE ARM Southern Great Plains central facility in central Oklahoma and the DOE ARM North Slope of Alaska site near Barrow, Alaska. Operational systems are expected to come online within the next year at the DOE ARM tropical western Pacific sites located at Manus, Papua New Guinea, and Nauru. In order for these radars to detect the full range of atmospheric hydrometeors, specific modes of operation must be implemented on them that are tuned to accurately detect the reflectivities of specific types of hydrometeors. The set of four operational modes that are currently in use on these radars are presented and discussed. The characteristics of the data produced by these modes of operation are also presented in order to illustrate the nature of the cloud products that are, and will be, derived from them on a continuous basis.

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CLOUDS AND MORE: ARM Climate Modeling Best Estimate Data

A New Data Product for Climate Studies

Shaocheng Xie, Renata B. McCoy, Stephen A. Klein, Richard T. Cederwall, Warren J. Wiscombe, Michael P. Jensen, Karen L. Johnson, Eugene E. Clothiaux, Krista L. Gaustad, Charles N. Long, James H. Mather, Sally A. McFarlane, Yan Shi, Jean-Christophe Golaz, Yanluan Lin, Stefanie D. Hall, Raymond A. McCord, Giri Palanisamy, and David D. Turner

Abstract

No Abstract available.

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