© Yuet Sim Li
Tai Mo Shan, Hong Kong, China
Latitude: 22° 24' 32'' N
Longitude: 114° 8' 17'' E
24 January 2016 0957 (Local Time)
Image P/S code: P.11.2.11
Image I.D.: 5177
Ice pellets are transparent ice particles with a diameter of less than 5 mm. The particles are usually spheroidal or irregular in shape, and rarely conical. They originate as raindrops or snowflakes that fall from a layer cloud such as Altostratus or Nimbostratus into a layer of air at a temperature above 0 °C, where the snowflakes melt or partially melt. They then fall into a layer of air at a temperature below 0 °C, where they freeze and reach the ground as frozen precipitation.
The ruler at the top of the photograph provides a scale against which these ice pellets can be measured. The lower scale is in centimetres (numbered) and millimetres. These ice pellets are 1 to 2 mm in diameter.
Links in the image description will highlight features on the image. Mouse over the features for more detail.
The upper air sounding made 2 hours before the photograph was taken shows thick cloud between 830 and 450 hPa. Between 800 and 640 hPa the temperature was above 0 °C and precipitation would have melted when falling through this region. Below 800 hPa, with the exception of a shallow layer around 900 hPa and the surface, the temperature was below 0 °C. The precipitation would have frozen in the sub-zero air below 800 hPa, reaching the ground in solid form.