2.2 Retrieval户}om radar re月ectivity
The total amount of water in the atmosphere, in
particular liquid water content in clouds, is one of the
important factors that determine precipitation process
and needs consideration in artificial rain enhancement.
In addition to aircraft measurements, remote sensing
from the ground appears to be more economic and ef-
ficient for the long-term observations. The radar echo
has been used in many studies (e.g., Li et al., 2003a;
Zhao et al., 2003; Fang, 2004; Xiao et al., 2004; Tian
et al., 2005) for cloud microp师sical structure analysis
and model evaluation. Lii et al. (2003) reviewed the
progress in atmospheric remote sensing and satellite
meteorology in China, in particular within the Insti-
tute of Atmospheric Physics. Liu and Ge (2006) gave
an overview on radar meteorology research at the Chi-
nese Academy of Meteorological Sciences over the past
half century, focusing on the application of the ad-
vanced dual linear polarization radar they developed
in watching, warning, and nowcasting of heavy rain
fall (Liu et al., 2002, 2005c; Cao and Liu, 2006; Cao
et al., 2006). Chen (2002) proposed a concept that
can determine the cloud liquid water path from cloud
microwave attenuation along the satellite-earth path.
Li et al. (2004b,c) developed a method of retrieving
cloud water mixing ratio (q}), rainwater mixing ratio
(qr), and water vapor mixing ratio (q ) from Doppler
weather radar's reflectivity. They showed that the ini-
tial fields of the mesoscale numerical model, including
these retrieved cloud microphysical messages, would
be helpful for numerical nowcasting of the precipita-
tion. Wang and Chu (2002) made an introduction
of the successful application of polarization weather
radar abroad, and discussed the application problem
of polarization weather radar in weather modification.
Liu et al. (2003e) reported their progress in developing
a polarization lidar for measuring profiles of depolar-
ization ratio of cirrus clouds and Asian dust aerosols.
The primary observational results over Hefei, in Anhui
Province of East-central China, show七hat the depo-
larization ratio for cirrus clouds varies from 0.4 to 0.5.
Liu et al. (2006) introduced a method of ground-based
microwave radiometer remote sensing retrieval of inte-
grated water vapor and cloud liquid water in the at-
mosphere. However; bias of the retrieved results is still
large, and more work on comparisons between radar
retrieval and aircraft measurements should be done