Download presentation
Presentation is loading. Please wait.
Published byOwen Brooks Modified over 10 years ago
1
Ewan OConnor, Robin Hogan, Anthony Illingworth Drizzle comparisons
2
Overview –Do operational forecast models simulate drizzle correctly? Models simulate drizzle through precipitation scheme Treat coalescence drizzle as light rain –Observed liquid water content/flux Cloud LWC retrieval Drizzle liquid water flux retrieval –Compare observations and models Daily basis Monthly means –Drizzle drop size Explicit in Met Office model Effect of changing drizzle number concentration
3
Liquid water content Method of Albrecht et al. (1990), Boers et al. (2000) –Use lidar/radar to determine cloud boundaries –Assume linear increase of LWC with height –Scale LWC profile to match LWP from radiometers LWC Height Cloud base (lidar) Cloud top (radar) Model levels
4
Liquid water content –LWC not retrieved in rain
5
Drizzle below cloud Doppler radar and lidar - 4 observables (OConnor et al. 2005) Radar/lidar ratio provides information on particle size
6
Drizzle below cloud Doppler radar and lidar - 4 observables (OConnor et al. 2005) Radar/lidar ratio provides information on particle size Retrieve three components of drizzle DSD (N, D, μ). Can then calculate LWC, LWF and vertical air velocity, w.
7
Liquid water flux –LWF retrieved below cloud base and in the absence of rain
8
ECMWF model –Cloud similar to observations
9
Met Office mesoscale model –Cloud similar to observations
10
Met Office global model –Has rain at correct time!
11
Meteo France ARPEGE model –Thin layers - can be one grid box thick
12
Compare obs/models –Models have similar LWC / LWP –Models overestimate precipitation
13
Compare daily means –Models have similar LWC / LWP –Models overestimate precipitation
14
Monthly comparisons –ECMWF model –Observations
15
Monthly comparisons –Met Office mesoscale model –Observations
16
Monthly comparisons –Met Office global model –Observations
17
Monthly comparisons –Meteo France ARPEGE model –Observations
18
Drizzle drop size –Met Office model uses explicit size distributions –Treats all precipitation as rain Overestimates drop sizes Underestimates evaporation Disdrometer Radar/lidar Model
19
Met Office diagnostic precipitation –Met Office model uses explicit size –Treats all precipitation as rain
20
Met Office diagnostic precipitation –Met Office model uses explicit size –Treats all precipitation as rain
21
Met Office diagnostic precipitation –Met Office model uses explicit size –Treats all precipitation as rain
22
Met Office diagnostic precipitation –Met Office model uses explicit size –Treats all precipitation as rain
23
Met Office diagnostic precipitation –Met Office model uses explicit size –Treats all precipitation as rain
24
Conclusion –Models have reasonable LWC Produce far too much drizzle Precipitation reaches surface Underestimate evaporation –Met Office model Overestimate of drizzle drop size
Similar presentations
© 2024 SlidePlayer.com Inc.
All rights reserved.