WXT as a disdrometer? - PowerPoint PPT Presentation

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WXT as a disdrometer?

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Drop size distribution data from WXT, disdrometer (RD-69) and POSS from J rvenp , Sorto ... Comparisons between disdrometer, WXT (and POSS) DSD data. ... – PowerPoint PPT presentation

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Title: WXT as a disdrometer?


1
WXT as a disdrometer?
  • Heikki Pohjola1) and Leila Konkola2)
  • Vaisala Oyj
  • University of Helsinki

2
The opportunity
  • Disdrometers are expensive and thus rare
  • Global distribution of DSD is badly known
  • Climatological research and radar measurements
    could benefit of reasonably priced disdrometers
  • For example NASAs
  • Global Precipitation Measurement (GPM) Program
  • Satellite will be launched 2013 ?
  • Understanding of clouds and rainfall processes
  • Make frequent rainfall measurements on a global
    basis.
  • FMI involved in ground validation with
    HelsinkiTestbed and radar network

3
Radar applications
  • Set one or more WXTs toblocked sectors of radar
  • combine dBZ valuesfor each image
  • Gapfilling between radars
  • Attenuation correction
  • between the radar and the target, some microwave
    power is lost.
  • (Barnes, S.L., 1964 A technique for maximising
    details in numerical weather map analysis. Jour_.
    AppI_Meteor., _3,396-409)

4
Radars measurement volume, km3
0,5 km
0,5...1 km
5
Radars measurement volume, km3
0,5 km
Raingauge e.g WXT, diameter 10 cm!!
0,5...1 km
6
Radars measurement volume, km3
0,5 km
Raingauge, diameter 10 cm!
0,5...1 km
7
Z from WXT measurement
Raincap sensor of WXT works as a disdrometer, and
measures N and D in time unit. Thus, we can
calculate reflectivity on ground Zg ?NiDi6
and avoid all fuzzy Z/R conversions
8
Data
  • Drop size distribution data from WXT, disdrometer
    (RD-69) and POSS from Järvenpää, Sorto
  • WXT_Z 21.8. -gt
  • RD-69 1.8. -gt
  • POSS All Testbed campaings

DSD data from WXT_Z
Date Time D1.00 D1.25 D1.60 D2.00 D2.50 D3.20 D4.00 D5.00
2006-09-03 231500 10.9 57.6 23.2 9.4 3.1 0 1 1.3
2006-09-03 232000 21 44 27 3.6 2.9 0 0 2.3
2006-09-03 232500 24.9 44.6 27.6 13 1 0.7 0 0
2006-09-03 233000 16.3 41.5 18.1 2.7 1.1 0 0 0
2006-09-03 233500 4.9 15.9 7.7 6.8 1.7 0 0 0
2006-09-03 234000 15.7 49.1 63 20.7 4.6 0.7 0 0
2006-09-03 234500 25.4 57.7 34.7 11.5 1.8 0 0 0
2006-09-03 235000 3.6 6 1 0 0 0 0 0
9
What next?
  • Comparisons between disdrometer, WXT (and POSS)
    DSD data.
  • If promising, first comparisons with radar
    reflectivity data.
  • Challenges
  • WXT data 5 min intervals, accuracy 5
  • RD-69 data 1 min intervals, accuracy 1,4 !!!!
  • Different drop diameter classes

10
back up slides
11
Defaults for WXT510 Disdrometer test units
  • DSD test units transmit automatically in every
    minute one message (so called auto composite
    message) which includes wind, PTU and disdrometer
    parameters in one string.
  • Disdrometer counters are automatically reset
    after any output including disdrometer
    parameters.
  • Example
  • 0R0,Dm270D,Sm0.9M,Ta22.4C,Ua35.8P,Pa1009.7H,1
    .0010.41n,1.2511.01n,1.606.45n,2.003.44n,2.50
    2.98n,3.202.46n,4.000.51n,5.000.00n
  •  
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