Luna-Cruz, Yaítza

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    Optical and radiative properties of aerosols over southwestern puerto rico using the multifilter rotating shadow-band radiometer
    (2008) Luna-Cruz, Yaítza; Pabón-Ortiz, Carlos U.; College of Arts and Science - Science; Jiménez González, Héctor; Armstrong-Pacheco, Roy A.; Department of Physics; Rosado-Román, José
    Currently, a poor understanding of aerosols in the atmosphere and their e??ffects on climate limits our ability to understand and quantify climate change. The most important issue about aerosols today is to reduce the uncertainty of known estimates of aerosol radiative forcing and its e??ffects on regional and global climate. Changes in atmospheric aerosol properties can modify the Earth's energy budget, the planetary albedo, the frequency of cloud occurrence, cloud thickness, and rainfall amounts. The quantitative determination of aerosols optical and radiative properties is then essential for the improvement of atmospheric models. In order to measure and ana- lyze the optical and radiative properties of aerosols, in a global or large scale context, the most e??ffective techniques are those of remote sensing. A Multi??lter Rotating Shadow-band Radiometer (MFRSR) was installed in June, 2005 at the Magueyes Island instrumental site (AERADNET) in Southwestern Puerto Rico (latitude = 17◦ 58' 13.5?? N, longitude = 67◦ 2' 43.5?? W, altitude = 12 m) as part of the NOAA Center for Atmospheric Sciences (NCAS) measurements. This ground-based instrument uses independent detectors and the automated shadow-band technique to make spectrally resolved measurements of total, direct and di??use components of solar irradiance at six wavelengths (414, 496, 612, 670, 868 and 937 nm) and at a broadband channel. The main objective was to obtain ground-based solar irradiance measurements in southwestern Puerto Rico, to determine the aerosols optical and radiative properties, such as aerosol optical depth (AOD) and Ångström exponent (α). Our analysis was focused at 496, 612, 670 and 868 nm, with a total of 59 clear days. Seasonal variations of AOD values with maximum values during the Summer (0.62) and minimum values during Winter (0.03) were found. Ångström exponent (α) results (496.2 nm - 868.3 nm) during a total of eight days with severe dust event passing over the site, include values from 0.10 to 0.31. A comparison of AOD and Ångström exponent between the MFRSR and the AERONET stations has been performed. There is remarkable agreement between both instruments observations with correlations coeffi??cients of 0.99, 0.99 and 0.99 for TOD at 500, 675, 870 nm respectively, 0.98, 0.98 and 0.97 for AOD and 0.95 for α. Comparison be- tween MFRSR and SeaWiFS satellite sensor was also performed with correlation coeffi??cients of 0.98. As a ??nal trajectory model analysis a classi??cation of aerosols for selected cases is also presented.