Export 7 results:
Sort by: Author [ Title  (Asc)] Type Year
[A] B C D E F G H I J K L M N O P Q R S T U V W X Y Z   [Show ALL]
Markowicz, KM, Flatau PJ, Ramana MV, Crutzen PJ, Ramanathan V.  2002.  Absorbing mediterranean aerosols lead to a large reduction in the solar radiation at the surface. Geophysical Research Letters. 29   10.1029/2002gl015767   AbstractWebsite

[1] We present direct radiometric observations of aerosol radiative forcing taken during the MINOS experiment (2001) at Finokalia Sampling Station located on North-Eastern shores of Crete, Greece. The mean value of aerosol optical thickness was 0.21 at 500 nm. Aerosols, mostly of anthropogenic origin, lead to a diurnal average reduction of 17.9 W m(-2) in the surface solar radiation, an increase of 11.3 W m(-2) in the atmospheric solar absorption, and an increase of 6.6 W m(-2) in the reflected solar radiation at the top-of-the atmosphere. Thus, the present data gives observational proof for the large role of absorbing aerosols in the Mediterranean. The negative surface forcing and large positive atmospheric forcing values observed for the Mediterranean aerosols is nearly identical to the highly absorbing south Asian haze observed over the Arabian Sea.

Wells, KC, Witek M, Flatau P, Kreidenwei SM, Westphal DL.  2007.  An analysis of seasonal surface dust aerosol concentrations in the western US (2001-2004): Observations and model predictions. Atmospheric Environment. 41:6585-6597.   10.1016/j.atmosenv.2007.04.034   AbstractWebsite

Long-term surface observations indicate that soil dust represents over 30% of the annual fine (particle diameter less than 2.5 mu m) particulate mass in many areas of the western US; in spring and summer, it represents an even larger fraction. There are numerous dust-producing playas in the western US, but surface dust aerosol concentrations in this region are also influenced by dust of Asian origin. This study examines the seasonality of surface soil dust concentrations at 15 western US sites using observations from the Interagency Monitoring of PROtected Visual Environments (IMPROVE) network from 2001 to 2004. Average soil concentrations in particulate matter less than 10 mu m in diameter (PM 10) were lowest in winter and peaked during the summer months at these sites; however, episodic higher-concentration events (> 10 mu g m(-3)) occurred in the spring, the time of maximum Asian dust transport to the western US. Simulated surface dust concentrations from the Navy Aerosol Analysis and Prediction System (NAAPS) suggested that long-range transport from Asia dominates surface dust concentrations in the western US in the spring, and that, although some long-range transport does occur throughout the year (1-2 mu g m(-3)), locally generated dust plays a larger role in the region in summer and fall. However, NAAPS simulated some anomalously high concentrations (> 50 mu g m(-3)) of local dust in the fall and winter months over portions of the western US. Differences between modeled and observed dust concentrations were attributed to overestimation of total observed soil dust concentrations by the assumptions used to convert IMPROVE measurements into PM(10) soil concentrations, lack of inhibition of model dust production in snow-covered regions, and lack of seasonal agricultural sources in the model. (c) 2007 Elsevier Ltd. All rights reserved.

Verlinde, J, Flatau PJ, Cotton WR.  1990.  Analytical Solutions to the Collection Growth Equation - Comparison with Approximate Methods and Application to Cloud Microphysics Parameterization Schemes. Journal of the Atmospheric Sciences. 47:2871-2880.   10.1175/1520-0469(1990)047<2871:asttcg>;2   AbstractWebsite

A closed form solution for the collection growth equation as used in bulk microphysical parameterizations is derived. Although the general form is mathematically complex, it can serve as a benchmark for testing a variety of approximations. Two special cases that can immediately be implemented in existing cloud models are also presented. This solution is used to evaluate two commonly used approximations. The effect of the selection of different basis functions is also investigated.

Goodman, JJ, Draine BT, Flatau PJ.  1991.  Application of Fast-Fourier-Transform Techniques to the Discrete-Dipole Approximation. Optics Letters. 16:1198-1200.   10.1364/ol.16.001198   AbstractWebsite

We show how fast-Fourier-transform methods can be used to accelerate computations of scattering and absorption by particles of arbitrary shape using the discrete-dipole approximation.

Flatau, PJ, Pielke RA, Cotton WR.  1988.  Application of symbolic algebra to the generation of coordinate transformations . Environmental Software. 3:158-160. Abstract

In this paper we present tools for automatic generation of generalized (variable and terrain-following) coordinate transformations and its use in numerical models of atmospheric flows. Such methodology should be competitive with the more cornraonly employed nested grid schemes. We discuss the symbolic (computer) algebra program for analytical calculation of Christoffel symbols, metric tensor and other geometrical objects describing a transformation. An example, related to the numerical modeling of mesoscale flows, is given. This example shows how coupled terrain-following m~d stretching transformation can be easily created. The possible application of such methodology in numerical modeling of air pollution on cirrus clouds is briefly discussed.

Flatau, PJ, Piskozub J, Zaneveld JRV.  1999.  Asymptotic light field in the presence of a bubble-layer. Optics Express. 5:120-124.   10.1364/OE.5.000120   AbstractWebsite

We report that the submerged microbubbles are an efficient source of diffuse radiance and may contribute to a rapid transition to the diffuse asymptotic regime. In this asymptotic regime an average cosine is easily predictable and measurable. (C) 1999 Optical Society of America.

Valero, FPJ, Bucholtz A, Bush BC, Pope SK, Collins WD, Flatau P, Strawa A, Gore WJY.  1997.  Atmospheric Radiation Measurements Enhanced Shortwave Experiment (ARESE): Experimental and data details. Journal of Geophysical Research-Atmospheres. 102:29929-29937.   10.1029/97jd02434   AbstractWebsite

Atmospheric Radiation Measurements Enhanced Shortwave Experiment (ARESE) was conducted to study the magnitude and spectral characteristics of the absorption Of solar radiation by the clear and cloudy atmosphere. Three aircraft platforms, a Grob Egrett, a NASA ER-2, and a Twin Otter, were used during ARESE in conjunction with the Atmospheric Radiation Measurements (ARM) central and extended facilities in north central Oklahoma. The aircraft were coordinated to simultaneously measure solar irradiances in the total spectral broadband (0.224-3.91 mu m), near infrared broadband (0.678-3.3 mu m), and in seven narrow band-pass (similar to 10 nm width) channels centered at 0.500, 0.862, 1.064, 1.249, 1.501, 1.651, and 1.750 mu m. Instrumental calibration issues are discussed in some detail, in particular radiometric power, angular, and spectral responses. The data discussed in this paper are available at the ARM ARESE data archive via anonymous FTP to