doctoralThesis
Desenvolvimento e calibração de fotômetro solar para medições da profundidade óptica por aerossóis e coluna de água precipitável
Fecha
2014-06-10Registro en:
CERQUEIRA JÚNIOR, João Gualberto de. Desenvolvimento e calibração de fotômetro solar para medições da profundidade óptica por aerossóis e coluna de água precipitável. 2014. 110f. Tese (Doutorado em Ciências Climáticas) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2014.
Autor
Cerqueira Júnior, João Gualberto de
Resumen
Instrumentation is a tool of fundamental importance for research in several areas of human
knowledge. Research projects are often unfeasible when data cannot be obtained due to lack
of instruments, especially due to impor
ting difficulties and the high costs there associated.
Thus, in order to collaborate with the enhancement of a
national technology, a
multiband
hand
-
held sun p
hotometer (FSM
-
4) was developed
to operate in the 500 nm, 670 nm, 870 nm
and 940 nm bands. In the
500 nm, 670 nm and 870 nm bands aerosols are monitored for
evaluation of the AOD (Aerosol Optical Depth), and the PWC (Precipitable Water Column) is
evaluated in the 940 nm band. For the development of the mech
anical and electronic parts for
the FSM
-
4, th
e materials and componen
ts should combine low cost and
quality of the data
collected. The calibration process utilized the Langley method (ML) and Modified Langley
Method (MLM). These methods are usually applied at high altitudes in order to provide
atmosp
heric optical stability. This condition however can be found in low height sites as
shown in the research by Liu et al. (2010). Thus, for calibration of the FSM
-
4, we investigated
the atmospher
ic optical stability utilizing
the ML and MLM at a site in the
cit
y of Caicó / RN,
located in the s
emiarid region in northeastern
Brazil. This site lies in a region far aw
ay from
large urban centers and
activities generating anthropogenic atmospheric pollution. Data for
calibration of the prototype were collected usin
g the FSM
-
4 in two separate operations during
the dry season, one in December 2012
and another in September 2013.
The methodologies
showed optical atmospheric instability in the studied region through the dispersion of the
values obtained for the calibrati
on constant. This dispersion is affected by the variability of
AOD and PWC during the appl
ication of the above mentioned
methods
. As an alternative to
the descr
ibed sun photometer calibration
, a short study was performed using the sun
photometer worldwide
network AERONET/NASA (AERsol RObotic NETwork
–
US Space
Agency), installed in Petrolina / PE in Brazil. Data were collected for three days utilizing the
AERONET instruments and the FSM
-
4, operating simultaneously on the same site. By way of
the ML and MLM
techniques, convergent test values were obtained for the calibration
constants, despite the low amount of data collected. This calibration transfer methodology
proved to be a viable alternative to the FSM
-
4 calibration
.