%0 Journal Article
%@holdercode {isadg {BR SPINPE} ibi 8JMKD3MGPCW/3DT298S}
%@nexthigherunit 8JMKD3MGPCW/3EU29DP 8JMKD3MGPCW/3EUFCFP
%@archivingpolicy denypublisher denyfinaldraft
%@issn 0016-7169
%@dissemination WEBSCI; PORTALCAPES; AGU.
%@resumeid 8JMKD3MGP5W/3C9JH3D
%@resumeid 8JMKD3MGP5W/3C9JHUD
%@usergroup administrator
%@usergroup alexandra
%@usergroup marciana
%3 Echer1.pdf
%X Observations of broadband solar UV-A irradiance (320-400 nm) were made at Santa Maria, Brazil (29° S, 53° W) between September 1993 and December 1996. Two different measurement techniques were used, the direct sun (DS) with the sensor pointed directly to the sun, and the zenith sky (ZS), with the sensor pointed to the zenith. The seasonal variation of UV-A DS and ZS irradiances measured at local noon is analysed. Both UV-A DS and ZS irradiances have a strong seasonal variability, anticorrelated to the solar zenith angle variation. It is shown that UV-A ZS irradiance has a larger seasonal variation than UV-A DS irradiance, with summer/winter ratios of 3.4 for UV-A ZS and 1.4 for UV-A DS. This difference is explained because of the geometrical arrangement of the observations; UV-A DS irradiance is easured tracking the sun and its variability is due to the atmospheric optical path variation during the year. UV-A ZS irradiance is diffuse irradiance measured pointing at a fixed direction, the zenith, and besides the atmospheric optical path variability, the component of direct irradiance incident on the horizontal surface has also a variation with solar zenith angle. Analysing UV-A DS and ZS irradiances versus solar zenith angle, it was observed that UV-A ZS decreases faster with higher solar zenith angles than UV-A DS. Calculations using Beers law at 370 nm were made and show similar behaviour for irradiances at a horizontal surface, compared to UV-A ZS, and at a surface perpendicular to the solar beam, compared to UV-A DS irradiance.
%8 Jan.-Mar.
%N 1
%T Observations of broadband solar UV-A irradiance at Santa Maria, Brazil (29°S, 53° W)
%K Solar radiation, solar UV, atmosphere, atmospheric radiative transfer.
%@secondarytype PRE PN
%@group DGE-INPE-MCT-BR
%@group RSU-INPE-MCT-BR
%@copyholder SID/SCD
%@secondarykey INPE-11203-PRE/6652
%2 sid.inpe.br/jeferson/2004/07.28.12.50.08
%@affiliation Instituto Nacional de Pesquisas Espaciais
%@affiliation Centro Regional Sul de Pesquisas Espaciais, CRSPE/INPE,
%@affiliation Takushoku University - Tokyo
%@affiliation National Institute of Polar Research, Tokyo,
%B Geofísica Internacional
%P 53-59
%4 sid.inpe.br/jeferson/2004/07.28.12.50
%D 2004
%V 43
%A Echer, Ezequiel,
%A Schuch, Nelson Jorge,
%A Makita, K.,
%A Okano, S.,
%@area CEA