1. Introduction
Ž .
The appearance of freezing rainrdrizzle supercooled rainrdrizzle is not a rare phenomenon, especially when a rain cloud or melting layer exists above a cold layer
Ž .
near the ground surface e.g., Stewart, 1992; Stewart and Crawford, 1995; Zerr, 1997 . On the other hand, it is worthy of consideration that meteorological conditions exist
where supercooled rainrdrizzle could form under low temperatures in the mid-winter season of the Arctic regions.
Ž .
Ohtake 1963 reported that in cold regions, supercooled rain sometimes fell even when the temperature was below 08C, at and above the ground. As to the problem of
Ž .
Ž .
formation of supercooled rain, Bocchieri 1980 and Huffman and Norman 1988 reported that about 44 and 30, respectively, of the freezing rainrdrizzle examined
by radiosonde observations had no warm layer with air temperature higher than 08C. Ž
. Ž
. Recently, Strapp et al.
1996 and Stuart and Isaac
1999 compiled the detailed
climatology of freezing rainrdrizzle for North America. Moreover, in-situ aircraft observations have revealed the presence of supercooled drizzle drops in stratiform
Ž clouds with temperatures colder than 08C e.g., Cober et al., 1995; Cober et al., 1996;
. Isaac et al., 1996 .
A few researchers have observed supercooled raindropsrdrizzle drops in the mid- Ž
. winter season of the Arctic region Magono and Kikuchi, 1980; Kajikawa et al., 1988 .
However, in those observations, the formation mechanism has not been proved clearly. This paper describes some considerations regarding the meteorological conditions and
Ž
X
the characteristics of supercooled drizzle observed at Inuvik, N.W.T., Canada 68822 N,
X
. 133842 W in the mid-winter season during the experiment ‘‘Studies on Water vapor,
Ž .
Aerosols and Nuclei Transportation, and Snow Crystals in the Arctic WANTS-Arctic ’’ Ž
. Kikuchi and Asuma, 1999 .
2. Observations
Supercooled drizzle drops were photographed by a camera installed on a polarizing microscope. Traces of those particles spread on a glass plate showed nearly circular
shapes, as seen in Fig. 1. The size of drizzle drops was derived from the calibration curve obtained by a spraying method in a cold room. In addition to the glass plate
method, a catching method in a laboratory dish poured silicon oil and replica method Ž
. Kajikawa et al., 1988 were used for the evaluation of precipitation intensity and size
distribution.
3. Results and consideration
Kategori