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SRL/Reference sonde P. Di Girolamo, D. Whiteman, B. Demoz, J. Wang, K. Beierle, T. Weckwerth PowerPoint Presentation
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SRL/Reference sonde P. Di Girolamo, D. Whiteman, B. Demoz, J. Wang, K. Beierle, T. Weckwerth - PowerPoint PPT Presentation


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SRL/Reference sonde P. Di Girolamo, D. Whiteman, B. Demoz, J. Wang, K. Beierle, T. Weckwerth. The Reference sonde (C34) consists of a Snow White (SW) chilled-mirror dew point hygrometer and a carbon hygristor for humidity measurements.

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slide1

SRL/Reference sonde

P. Di Girolamo, D. Whiteman, B. Demoz,

J. Wang, K. Beierle, T. Weckwerth

The Reference sonde (C34) consists of a Snow White (SW) chilled-mirror dew point hygrometer and a carbon hygristor for humidity measurements.

Accuracy: 0.25 % in terms of relative humidity measurements. 

The SW needs no individual calibration and can be used again without recalibration if recovered after flight.

slide2

Comparison between SRL and NCAR Reference radiosondes

NCAR Reference radiosonde

  • Nine reference radiosonde were launched in Homestead during IHOP
  • Eight of these were launched at times when SRL was operational.
  • Only three reference radiosondes were launched during the 11 days for which SRL data have been released (Z20020528_162645, Z20020609_104618 and Z20020620_025610).
slide3

Comparison between SRL, reference sonde (both SW and carbon hygristor) and closest in time Vasiala RS 80.

  • SRL data have been interpolated at sensors’ heights.
  • Unfortunately, some data points result to be missing in the reference sonde profiles.
  • Reference sonde Z20020528_162645
    • no height information between 1400 and 1850 m
  • Reference sonde Z20020609_104618
    • Large gaps of humidity information (2-3.5 km; 4-5.5 km)
    • pressure information result to be missing (only the surface value results to be available).
  • Deviations beween SRL and reference radiosonde are as large as 20 %.
slide4

Z20020528_162645 side by side with y5281739.hom

  • Z20020609_104618 simultaneously with y6091135.hom
  • Z20020620_025610simultaneously with y6200330.hom

The Reference Sonde (RS) uses a hypsometer to measure pressure. This sensor is not reliable so we did not use the pressure data from the RS, but we used the pressure data from the Vaisala radiosondes, which is good.

slide5

Mixing ratio: direct measurement for the Raman lidar

  • Relative humidity: direct measurement for the radiosonde
  • Relative humidity water vapour mixing ratios
  • saturation vapour pressure,
  • which depends of pressure and temperature.
  • Several empirical relationships, which we compared and revealed deviations between them up to 3 %.
    • WMO formulation
    • Bolton formulation (1980)
    • Expression derived from Smithsonian Meteorological Tables.

IHOP_2002 Water Vapor Intercomparison Workshop, 2-3 October 2003, NCAR, Boulder, CO

slide7

SRL is moister than SW

  • (differences ~ -20 % up to 4.8 km a.s.l.)
  • Much better agreement above
  • Integration time for lidar to be changed in order to meet reference sonde effective launch time, which is not 10:46 UT, but 11:40 UT
  • Wind speed in BL > 15 m/s, so that different air masses are sounded from Lidar and sondes
slide8

SRL is drier than SW below ~ 2.3 km a.s.l., moister between 2.3 and 3 km, and drier above (differences ~ -30 to +20 %)

  • Integration time for lidar to be changed in order to meet reference sonde effective launch time, which is not 02:56 UT, but 03:35 UT
  • Wind speed in BL > 15 m/s