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Shaocheng Xie, Timothy Hume, Christian Jakob, Stephen A. Klein, Renata B. McCoy, and Minghua Zhang

Abstract

This study documents the characteristics of the large-scale structures and diabatic heating and drying profiles observed during the Tropical Warm Pool–International Cloud Experiment (TWP-ICE), which was conducted in January–February 2006 in Darwin during the northern Australian monsoon season. The examined profiles exhibit significant variations between four distinct synoptic regimes that were observed during the experiment. The active monsoon period is characterized by strong upward motion and large advective cooling and moistening throughout the entire troposphere, while the suppressed and clear periods are dominated by moderate midlevel subsidence and significant low- to midlevel drying through horizontal advection. The midlevel subsidence and horizontal dry advection are largely responsible for the dry midtroposphere observed during the suppressed period and limit the growth of clouds to low levels. During the break period, upward motion and advective cooling and moistening located primarily at midlevels dominate together with weak advective warming and drying (mainly from horizontal advection) at low levels. The variations of the diabatic heating and drying profiles with the different regimes are closely associated with differences in the large-scale structures, cloud types, and rainfall rates between the regimes. Strong diabatic heating and drying are seen throughout the troposphere during the active monsoon period while they are moderate and only occur above 700 hPa during the break period. The diabatic heating and drying tend to have their maxima at low levels during the suppressed periods. The diurnal variations of these structures between monsoon systems, continental/coastal, and tropical inland-initiated convective systems are also examined.

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Graeme L. Stephens, Robert F. McCoy Jr., Renata B. McCoy, Philip Gabriel, Philip T. Partain, Steven D. Miller, and Steven P. Love

Abstract

This paper describes the design and characteristics of a scanning spectral polarimeter designed to measure spectral radiances and fluxes in the range between 0.4 and 4.0 μm. The instrument characteristics are described, and the procedures to calibrate the unpolarized radiances and fluxes in the spectral range from 0.4 to 1.1 μm are discussed along with detailed error analyses of this calibration. The accuracy of the radiance calibration was determined to be approximately 3%. The calibration of fluxes based on two different procedures is estimated to be accurate to 3%–6%. Detailed calibration of fluxes was performed using a standard lamp that is not an isotropic source. For this type of calibration the angular response of the flux channel deviates from a pure cosine function at wavelengths longer than 0.74 μm, thus forming a frontal lobe. A less detailed calibration using a 40-in. integrated sphere was also performed. In that case the light source is isotropic and the frontal lobe does not appear. Calibration factors are derived by combining data from both calibration procedures. A comparison with spectral flux measurements obtained from different instruments with different angular response properties is presented with agreement that is within the quoted calibration accuracy. Measurements obtained from two different aircraft flights are presented to illustrate the types of application of the data. Data analyses shows that the reflected (unpolarized) fluxes measured above a cirrus cloud can be reasonably matched to modeled fluxes using optical properties retrieved from the measured (unpolarized) radiances.

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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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