East Asia and Western Pacific METEOROLOGY AND CLIMATE

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In the meantime, with the increasing concern about the impact of
atmospheric trace gases and aerosols on the environment, climate and
ecology in recent years, we have strengthened the research on the
probing of atmospheric trace gases and aerosols and developed
successfully some inversion methods, such as solar extinction-forward
scattering method of remote sensing of aerosol size distribution and
complex refraction indextl^-loj^ and some other combined inversion
methods. Through these methods, the ordinary photometer technology
can be used in a broader area.
1. The Laser Probing of Visibility
Laser radar is almost the only effective means of probing
visibility due to the fact that it can probe efficiently the spatial
distribution of atmospheric extinction coefficient* In the last 20
years, there were many studies in using laser tchnology to probe
visibility in both China and abroad^6»7,18-20]^ but all these were
still at the theoretical and experimental stages. Our research on the
laser probing of visibility has put significant step. A small version
of YAG lidar for visual range probing has been using preliminarily at
some airports in China.
1. Visibility mainly depends on the extinction coefficient of
the path, the brightness of observed objects and its background, and
the brightness of the sky. Lu Daren*-^ analyzed the relationship
between visual range and other atmospheric and background parameters,
derived some simplified relations for lidar-sensing visual range.
Zhao Yanzeng^J used a lidar to measure the atmospheric extinction
coefficient, and used a photometer to measure brightness of targets,
background and the sky, solving successfully the probing of slant
visibility. Her results coincide well with pilots* visual
observations.
2. Qiu Jinhuan^1°-f,
based on radiative transfer computation
results, presented an empirical formula with which the proportion of
downward average sky brightness to quasi-horizontal sky brightness can
be calculated. Since the target and background can be considered as a