Geoscience Reference
In-Depth Information
Fig. 8. The relationship between maximum depolarization ratio and maximum
extinction coecient of cloud events with respect to
RH
in Spring from 2002 to 2004.
3.3
. Characteristics of dust clouds
Our observation location was affected frequently by outside aerosols such
as dust storms from Northern China which mostly appear during the spring
seasons.
13
−
15
The term “dust cloud” has been used instead of using “dust
layer” because we have measured higher values of backscattering ratio of
the dust as compared with other literature. We think that this phenomenon
is related with our location as it is of low latitude, where atmosphere is
more humid and the dust particles can easily interact with humidity and
pollution.
12
Figure 9 shows one of the dust-cloud case on 31 March 2002,
which is observed over our lidar site during the period (spring season) of
dust storm which break out in Northern China. The peaks of
BR
of this
dust cloud are at 1.8 and 2.1 km with
around 100% and 80%, and
depolarization ratios are 0.27 and 0.30, respectively. The upper layer, which
is around 2.1 km has lower
RH
DR
(0.30). The result shows that the dust clouds, which are measured by lidar
during spring seasons, accompanied with BGA and water clouds have higher
extinction coecient and
BR
(
∼
12.5) with
RH
(
∼
80%), but higher
DR
.
