Raúl D’Elia

New differential absorption lidar for stratospheric ozone monitoring in Patagonia, South Argentina

As part of environmental studies concerned with measurements of the stratospheric ozone layer, CEILAP has developed a new differential absorption lidar (DIAL) instrument. Since the initial construction of the first DIAL instrument, the Lidar Division of CEILAP has made important financial and scientific investments to upgrade this initial prototype. The new version has a bigger reception system formed by four Newtonian telescopes, each of 50 cm diameter, and a larger number of detection channels: four different wavelengths are detected simultaneously and six digital channels record the Rayleigh and Raman backscattered photons emitted by a ClXe excimer laser at 308 nm and the third harmonic of a Nd–YAG laser at 355 nm. A number of different changes have been made to increase the dynamic range of this lidar: a mechanical chopper was installed together with a gated photomultiplier in the high-energy detection channels to avoid the detector being overloaded by strong signals from lower atmospheric layers. This new version was installed inside a shelter, giving the possibility to make field campaigns outside CEILAP laboratories, for example the SOLAR campaign made in the Argentine Patagonian region during 2005 and 2006 spring periods. In this paper a full description of the instrument update is given. Intercomparisons with the ozone sonde and satellite platform instrument are presented. The results show agreement better than 10% in 16–38 km altitude range when the same airmasses are sampled. The comparison with five quasi-coincident sondes launched in Punta Arenas during spring 2005 shows good agreement between both types of measurement, with relative differences inside 1σ deviation of the lidar measurement. The comparison of the integral of height integrated lidar profiles with total ozone column measured with a Brewer photometer shows good agreement, with relative differences less than 10%.

UV ground based measurements in Río Gallegos, Argentina

CEILAP’s Lidar Division has established an atmospheric remote sensing site in Rio Gallegos (51°55′ S, 69°14′ W) in the southern region of Argentina. SOLAR Campaign was held during 2005–2006. The main objectives of this experiment were to measure stratospheric ozone profiles and surface UV radiation in a subpolar region, where the influence of polar vortex and the Antarctic ozone hole are remarkable. This remote sensing site has lidar instruments and passive sensors to measure solar UV irradiance. In this paper we focused on passive remote sensing sensors and the Rio Gallegos erythemal irradiances reported during 2005–2006. Time evolution of UV index was derived from these measurements and the influence of ozone depleted air masses passing over over Rio Gallegos is highlighted in this paper. This Patagonian region is characterized by high cloud cover during the day that strongly changes the distribution of UV radiation that reaches the ground surface. For that reason some overpasses of ozone hole are maske...

Attenuation by clouds of UV radiation for low stratospheric ozone conditions

Stratospheric poor ozone air masses related to the polar ozone hole overpass subpolar regions in the Southern Hemisphere during spring and summer seasons, resulting in increases of surface Ultraviolet Index (UVI). The impact of these abnormal increases in the ultraviolet radiation could be overestimated if clouds are not taking into account. The aim of this work is to determine the percentage of cases in which cloudiness attenuates the high UV radiation that would reach the surface in low total ozone column situations and in clear sky hypothetical condition for Rio Gallegos, Argentina. For this purpose, we analysed UVI data obtained from a multiband filter radiometer GUV-541 (Biospherical Inc.) installed in the Observatorio Atmosferico de la Patagonia Austral (OAPA-UNIDEF (MINDEF – CONICET)) (51 ° 33’ S, 69 ° 19’ W), Rio Gallegos, since 2005. The database used covers the period 2005-2012 for spring seasons. Measured UVI values are compared with UVI calculated using a parametric UV model proposed by Madron...

Study of UV cloud modification factors in Southern Patagonia

Anthropogenic perturbation of the ozone layer has induced change in the amount of UV radiation that reaches the Earth’s surface, mainly through the Antarctic ozone hole, making the ozone and ultraviolet (UV) radiation two important issues in the study of Earth atmosphere in the scientific community. Also the clouds have been identified as the main modulator of UV amount in short time scales and produce the main source of uncertainty in the projection of surface UV level as consequence of projected ozone recovery. While clouds can decrease direct radiation, they can produce an increase in the diffuse component, and as consequence the surface UV radiation may be higher than an equivalent clear sky scenario for several minutes. In particular this situation can be important when low ozone column and partially cloud cover skies happen simultaneously. These situations happen frequently in southern Patagonia, where the CEILAP Lidar Division has established the Atmospheric Observatory of Southern Patagonia, an at...

Using Lidar to Measure the Ozone Layer

South American scientists are using lidar technology to measure stratospheric ozone, water vapor and aerosols in Argentine Patagonia. Their work is helping to monitor global climate change, and has led to the development of a method for alerting local populations to the presence of the ozone hole.