In this study, it is demonstrated that a combination of VHF and millimeter-wave Doppler radars is a key tool for observing particle fall velocity in cirriform clouds. VHF (47-MHz) and millimeter-wave (95-GHz) Doppler radars observed cirriform clouds at West Sumatra, Indonesia (0.2°S, 100.32°E) from 2000 LT 14 to 0800 LT 15 November 2005. Radar reflectivity factor (Ze) observed by the 95-GHz radar showed that echoes from cloud particles had tops around 12-14 km and bottoms around 8-10 km. Doppler velocity observed by the vertically pointed beam of the 95-GHz radar (V&lt
inf&gt
air+Z&lt
/inf&gt
) was compared with vertical air velocity (V&lt
inf&gt
air&lt
/inf&gt
) observed by the 47-MHz radar to confirm that V&lt
inf&gt
air+Z&lt
/inf&gt
, a sum of V&lt
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air&lt
/inf&gt
and reflectivity-weighted particle fall velocity (V&lt
inf&gt
Z&lt
/inf&gt
), showed consistent changes with V&lt
inf&gt
air&lt
/inf&gt
and hence V&lt
inf&gt
Z&lt
/inf&gt
is able to be retrieved by subtracting V&lt
inf&gt
air&lt
/inf&gt
from V&lt
inf&gt
air+Z&lt
/inf&gt
. The correlation coefficient between V&lt
inf&gt
Z&lt
/inf&gt
and Z&lt
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e&lt
/inf&gt
in the middle part of clouds (10.5-12.2 km) was -0.81, which was higher than that (-0.47) in the bottom part (7.2-10.5 km). The change of V&lt
inf&gt
Z&lt
/inf&gt
for Z&lt
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e&lt
/inf&gt
in the middle part was larger (Z&lt
inf&gt
e&lt
/inf&gt
= -31.9 V&lt
inf&gt
Z&lt
/inf&gt
- 32.2) than that in the bottom part (Z&lt
inf&gt
e&lt
/inf&gt
, = -90.2 V&lt
inf&gt
Z&lt
/inf&gt
- 71.8). These results suggest that particle size was a dominant factor that determined Z&lt
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e&lt
/inf&gt
in the middle part. Using V&lt
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Z&lt
/inf&gt
, median volume diameter (D&lt
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0&lt
/inf&gt
) was estimated to suggest that D&lt
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0&lt
/inf&gt
was larger than ∼70 μm in the bottom part and ranged from ∼40 μm to larger than ∼106 μm in the middle part. Copyright 2008 by the American Geophysical Union.