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Estimating Temperature Lapse Rate with Doppler SODAR Technology

Study aims to determine if Doppler SODAR data can calculate lapse rate under stable conditions. Compare data with tower for empirical coefficients.

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Estimating Temperature Lapse Rate with Doppler SODAR Technology

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  1. TEMPERATURE LAPSE RATE ESTIMATION BY DOPPLER SODAR Jean-Michel FAGE, PRESIDENT, REMTECH INC, 2 Red Oak Road, St James NY 11780, USA Tel: (303) 772 68 25, Fax: (303) 772 6827, sales@remtechinc.com

  2. OBJECTIVE • The goal of the study is to determine if it is possible to use the data from a Doppler SODAR to determine the lapse rate under stable conditions. • Compare data from SODAR with tall tower to develop empirical coefficients for further use and algorithm development.

  3. DATA SOURCE FOR INITIAL ALGORITHM DEVELOPMENT Kernforschungszentrum (Nuclear Research Center), Karlsruhe, Germany) 200 meter measurement tower

  4. The PA2 SODAR, similar to the system at Kernforschungszentrum (Nuclear Research Center) in Karlsruhe (West Germany)

  5. THEORY The following approach corresponds to the so-called “Level 2” of Mellor & Yamda where advection and diffusion terms are neglected in the Fluid Mechanics equations, which leads to (in the PBL approximation):  q3/ 1= – uw (U / z) – vw (V/z) + g w’ q ²/2 = – w’ (/z) where: -  characteristics lengths - u, w horizontal and vertical speed fluctuations - ’ potential temperature fluctuation - q kinetic energy - sigma of the potential temperature fluctuations

  6. THEORY The derivation resolves down to: / z E 3/2 w-1 The empirical formula, which is applied to the SODAR data reads: / z = A + B E 3/2 w-1 A and B are empirical coefficients which have been estimated using previous data.

  7. THEORY A and B coefficients of the lapse rate formula vary They are constantly recalibrated using two techniques: - if the RASS is not present we infer that the atmosphere is adiabatic at least for a few hundred meters above the surface layer during the afternoon - if the RASS is present we use the RASS data themselves by a least square optimization between the RASS data derived lapse rate and the lapse rate obtained from the Sodar only.

  8. 6.0°C/100m -___ TOWER ----- SODAR 3.0°C/100m 0.0°C/100m -3.0°C/100m

  9. STATISTICS Correlation Between SODAR and Tower: 0.78 Standard Deviation of the difference between the SODAR and tower, by level (in °C/100 m): 180 m 0.63 160 m 0.54 140 m 0.60 120 m 0.64 100 m 0.78 80 m 0.98 60 m 1.13

  10. PA0 SODAR Antenna

  11. WIND SPEED DATA FROM PA0 ON ROOF

  12. LAPSE RATE DATA FROM PA0 ON ROOF

  13. Radio Acoustic Sounding System (RASS) RASS Antennas PA5 Antenna Solar Power Array

  14. CONCLUSIONS • Possible to measure lapse rate with SODAR • Can be included with all versions of the SODAR • Empirical nature of system requires it to learn at each site for a period of time • System improves with RASS as part of the system

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