Dual Doppler lidar observations during T-REX Martin Weissmann, Andreas Dörnbrack

AMS Mountain Meteorology Conference, Santa Fe, 30 August 2006

Dual Doppler lidar observations during T-REX

Martin Weissmann, Andreas Dörnbrack Institut für Physik der Atmosphäre, DLR Oberpfaffenhofen, Germany

Ron CalhounDepartment of Mechanical and Aerospace Engineering, Arizona State University, USA

Andreas WieserInstitut für Meteorologie und Klimaforschung, Forschungszentrum Karlsruhe, Germany


DLR lidarASU lidar

Independence

Owens Valley

80°distance ~3 km

260°


instrument: coherent 2-µm Doppler wind lidar(rented from Lockheed Martin Coherent Technologies)deployment: 14 March - 24 April 2006 (6 weeks)nearly continuous measurements

emitted pulses: 2 µm, 500Hz, 450 nsmeasured signal: backscatter from atmospheric aerosolsDoppler shift --> radial velocityhemispherical scannerrange up to 11 km

180° vertical slice scan (RHI): 30 - 90 s360° conical scan (PPI): 60 - 120 sup to ~3000 scans per day

ASU lidar: older version of the same system


Sketch from T-REXScientific Overview Document

IOP 13, 16 March2130 UTC

wave - not stationarysmall, rapidly evolving vortices

along-valley flow pushing beneath westerly downslope flow

thermally driven turbulence

--> complex and unsteady 3D flow

West East


Sketch from T-REXScience Overview Document

IOP 13, 16 April2134 UTC

West East


Sketch from T-REXScience Overview Document

IOP 13, 16 April2143 UTC

West East


IOP 13, 16 April 2108 - 2343 UTC

similar unsteady flow during all strong mountain wave events

animation: http://www.pa.op.dlr.de/trex/filme/2006_04_16_utc2030.AVI


IOP 6, 25 March 2006

"Components" of a rotor, but no full circulation:- with in-situ observations this could look like a rotor- rotor/roll clouds


Dual Doppler analysis25 March 1807-1808 UTC

x x

similar observations several times during IOP6, and around 1300 UTC 17 April (shortly after end of IOP 13)

x xx x


IOP 6, 25 March 2006, 1802 - 1825 UTC

animation: http://www.pa.op.dlr.de/trex/filme/2006_03_25_utc1805.AVI


Conical (PPI) lidar scans at 5° elevation25 March 2006

1700 UTC1730 UTC1800 UTC1830 UTC1900 UTC1930 UTC


Conclusions

successful dual Doppler lidar analysis, improvement of algorithms and noise filters planend

classical rotor concept does not seem appropriate to explain lidar observations during T-REX

observations show: waves/hydraulic jumps stationary for 5-20 min rapidly evolving vortices develop out of hydraulic jump/shear instabilities/wave breaking significant along-valley flow interacts with the downslope flow strong turbulence and 3D-variability due to heating and complex terrain

future suggestions: 3D simulations that include an along-valley flow reconsider classic rotor concepts - no clear observational evidence in literature in-situ observations spread over hours cannot be used for a composite during these events

Are rotors described in the literature really (all) rotors, or the consequence of misleading 2D-simulations and sparse observations spread over longer time periods in a highly unsteady/turbulent flow system?


THANKS TO

Mark Vercauteren and Keith BarrLockheed Martin Coherent Technologies

Susanne Drechsel, University Innsbruck Alexander Klee, University Innsbruck and DLR

DLR T-REX Homepage

www.pa.op.dlr.de/trex/


IOP 13, 15 April, 1107 - 1440 UTCanimation of aereosol backscatter intensity

animation: http://www.pa.op.dlr.de/trex/filme/2006_04_15_utc1100_bs.AVI


Dual Doppler analysis on 15 April

1142 UTC1407 UTC

Documents

Dual Doppler lidar observations during T-REX Martin Weissmann, Andreas Dörnbrack