TEMPERATURE LAPSE RATE ESTIMATION BY

DOPPLER SODARJean-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

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.

DATA SOURCE FOR INITIAL ALGORITHM DEVELOPMENT

Kernforschungszentrum (Nuclear Research Center), Karlsruhe, Germany)

200 meter measurement tower

The PA2 SODAR, similar to the system at Kernforschungszentrum

(Nuclear Research Center) in Karlsruhe (West Germany)

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

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.

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.

THEORY

6.0°C/100m

3.0°C/100m

0.0°C/100m

-3.0°C/100m

-___ TOWER ----- SODAR

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 0.63160 m 0.54140 m 0.60120 m 0.64100 m 0.78 80 m 0.98 60 m 1.13

PA0 SODAR Antenna

WIND SPEED DATA FROM PA0 ON ROOF

LAPSE RATE DATA FROM PA0 ON ROOF

PA5 Antenna

RASS Antennas

Solar Power Array

Radio Acoustic Sounding System (RASS)

CONCLUSIONS

1. Possible to measure lapse rate with SODAR

2. Can be included with all versions of the SODAR

3. Empirical nature of system requires it to learn at each site for a period of time

4. System improves with RASS as part of the system