Observed microphysical structure of nimbostratus in northeast cold vortex over China

- The microphysical structure of the nimbostratus was observed by airborne probes and rain gauges.
- Hallett-Mossop mechanism leads to high ice particle concentrations between -3 °C and -6 °C.
- Significant horizontal variability was evident on the scale of few hundred meters.
- A power law relationship between the intercept and slope parameters for ice spectra.

Airborne measurements were collected during a stepwise ascent within a nimbostratus cloud associated with a northeast cold vortex in Jilin Province over China on 20 June 2005 to study cloud structure and ice particle spectra. The microphysical structure of the nimbostratus was elucidated by King liquid water probe and Particle Measuring Systems (PMS) probes aboard the research aircraft. The PMS 2D images provide detailed information on crystal habits. A thick layer of supercooled cloud is observed and Hallett-Mossop ice multiplication process is used to explain very high ice particle concentrations in the temperature region between − 3 °C and − 6 °C. From near cloud top to melting layer, ice crystals shape in the form of columns, needles, aggregations and plates. In addition, significant horizontal variability was evident on the scale of few hundred meters. Ice particle spectra in this cloud were adequately described by exponential relationships. Relationship between the intercept (N0) and slope (λ) parameters of an exponential size distribution was well characterized by a power law.