Inproceedings,
Worldwide linke turbidity information
(2003)
Abstract
This paper describes the algorithms and data used to construct a
worldwide Linke turbidity factor (TL, for an air mass equal to 2)database.
Two main steps had to be performed to obtain the information: 1.
Assembling estimates of TL and 2. fusing different background layers
for the construction of the TL maps. The estimates of TL have two
forms: either they stand for specific geographical locations and
have a high accuracy, or they are available as gridded data averaged
over large areas. Point information was gathered from measured time
series of hourly beam and daily global radiation, which were transformed
to TL. From publications and networks like AERONET other turbidity
quantities were obtained and transformed to TL. The basic gridded
data are the maps of daily global irradiation supplied by the NASA-Langley
Research Center. The included monthly clear sky irradiations were
converted to TL with the same method as for the ground sites. Further
gridded information was taken from NOAA pathfinder aerosol data and
NASA NVAP. An algorithm was devised to fuse these two types of data
and to produce gridded maps in a canonical projection and 5? arc
angle cells. These final maps should reproduce the values observed
at specific locations. The root mean square error of the interpolation
is 0.73 TL units.
