Usefulness of vertical velocity measurements in clouds with a 1290 MHz profiler Henk Klein Baltink Atmospheric Research Section

21 October 2002Cloudnet Workshop KNMI2 Quiet-air fall velocity spectral line Spectral broadening by turbulence 2w2w wi-wwi-w wi+wwi+w wiwi Resulting spectrum Mean vertical speed w Problem: Velocity power spectrum <> DSD

21 October 2002Cloudnet Workshop KNMI3 DSD retrieval from single cloudradar spectrum Gossard (et al) (1994,1997) Babb et al (1999), Klugmann (2001): - use specific spectral shape in the small droplet range to estimate  w - cloud peak is at mean vertical speed Babb et al (2000): - double sided constrained inversion technique

21 October 2002Cloudnet Workshop KNMI MHz Windprofiler vertical speed Origin backscatter: Rayleigh vs. Bragg in rain: Rayleigh scatter from higher levels (ice clouds): mainly Rayleigh in drizzle/light rain: often both in water clouds: (only?) Bragg in clear-air: Bragg

21 October 2002Cloudnet Workshop KNMI5 Windprofiler operational acquisition cycle alternating low (100 m) and high mode (400 m) per mode 1 vertical and 4 oblique beams dwelltime per beam  25 sec. spectral resolution  30 cm/s not co-located with cloudradar beam-width: 6°  quantative use of w and  w limited?

21 October 2002Cloudnet Workshop KNMI6 Case: 27-July-2002

21 October 2002Cloudnet Workshop KNMI7 Backscatter profiler and CT75

21 October 2002Cloudnet Workshop KNMI8 Low mode vertical beam, CT75 Base

21 October 2002Cloudnet Workshop KNMI9 35 GHz Cloudradar Backscatter

21 October 2002Cloudnet Workshop KNMI10 Follow-up (?): assessment usefulness “w” on a case-by-case base enhanced backscatter in water clouds: related to cloud geometry/top ? use of co-planar oblique beams for estimation of w optimize acquisition cycle (or use SA-technique ?) discrimination between Rayleigh/Bragg scatter