TY - JOUR

T1 - Simulated airborne flux measurements in a LES generated convective boundary layer

AU - Schröter, M.

AU - Bange, J.

AU - Raasch, S.

N1 - Funding Information: The authors would like to thank A. Muschinski who had the idea to do this investigation. They also wish to thank D. Lenschow for useful comments. This research was partly supported by the Deutsche Forschungsgemeinschaft (German Science Foundation) through the Sonderforschungsbereich 420 Flugmesstechnik (Special Research Program ‘Flight Measurement Technique’). All model runs were performed on the Fujitsu VPP-300 at the Regionales Rechenzentrum für Niedersachsen (Regional Scientific Computing Centre of Lower Saxony, RRZN) in Hannover, Germany.

PY - 2000/6

Y1 - 2000/6

N2 - One aim of past boundary-layer experiments with aircraft was the determination of areally averaged heat fluxes. In spite of sophisticated instrumentation the measured fluxes extrapolated to the ground differed significantly from fluxes measured directly at ground stations. This study presents simulated sensible heat flux measurements with aircraft flights through a synthetic convective boundary layer created by a 401 x 401 x 42 cubic-grid large eddy simulation (LES) with a grid spacing of 50 m. After some considerations with respect to necessary measurement lengths using results of Lenschow and Stankov (1986 - J. Atmos. Sci. 43, 1198-1209), simulated measurement campaigns were carried out in three model runs. During each model run five sets of measurement runs were carried out successively. During each set of runs 10 aircraft flew at 10 altitudes with a ground speed of 100 m s-1 simultaneously through time and space. In total, 150 legs were carried out, 15 at each flight level. The resulting ‘measured’ heat fluxes were compared with those of the ‘true’ flux profiles obtained directly from the ensemble-averaged LES-generated data. No significant systematic error between ‘measured’ and ‘true’ profiles was observed. Furthermore, the comparison of the resulting relative error with the theory of Lenschow and Stankov showed a good agreement at all measurement levels.

AB - One aim of past boundary-layer experiments with aircraft was the determination of areally averaged heat fluxes. In spite of sophisticated instrumentation the measured fluxes extrapolated to the ground differed significantly from fluxes measured directly at ground stations. This study presents simulated sensible heat flux measurements with aircraft flights through a synthetic convective boundary layer created by a 401 x 401 x 42 cubic-grid large eddy simulation (LES) with a grid spacing of 50 m. After some considerations with respect to necessary measurement lengths using results of Lenschow and Stankov (1986 - J. Atmos. Sci. 43, 1198-1209), simulated measurement campaigns were carried out in three model runs. During each model run five sets of measurement runs were carried out successively. During each set of runs 10 aircraft flew at 10 altitudes with a ground speed of 100 m s-1 simultaneously through time and space. In total, 150 legs were carried out, 15 at each flight level. The resulting ‘measured’ heat fluxes were compared with those of the ‘true’ flux profiles obtained directly from the ensemble-averaged LES-generated data. No significant systematic error between ‘measured’ and ‘true’ profiles was observed. Furthermore, the comparison of the resulting relative error with the theory of Lenschow and Stankov showed a good agreement at all measurement levels.

KW - Airborne flux measurements

KW - Averaging length

KW - Convective boundary layer

KW - Large-eddy simulation

KW - Spectra

UR - http://www.scopus.com/inward/record.url?scp=0343090451&partnerID=8YFLogxK

U2 - 10.1023/A:1002649322001

DO - 10.1023/A:1002649322001

M3 - Article

AN - SCOPUS:0343090451

VL - 95

SP - 437

EP - 456

JO - Boundary-Layer Meteorology

JF - Boundary-Layer Meteorology

SN - 0006-8314

IS - 3

ER -