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Estimation of drag coefficient at low wind speeds over the monsoon trough land region during MONTBLEX‐90
Author(s) -
Rao Kusuma G.,
Narasimha R.,
Prabhu A.
Publication year - 1996
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/96gl02368
Subject(s) - drag coefficient , anemometer , wind speed , trough (economics) , roughness length , correlation coefficient , meteorology , drag , atmospheric sciences , planetary boundary layer , geology , environmental science , wind profile power law , physics , mathematics , mechanics , turbulence , macroeconomics , statistics , economics
Using observational data acquired during the Monsoon Trough Boundary Layer Experiment (MONTBLEX‐90), the drag coefficient C D is estimated over two land stations, Jodhpur (arid region) and Kharagpur (moist region), by eddy correlation of velocity data from sonic anemometers. At low winds C D varies with wind speed according to a power law, which at Jodhpur takes the form C D =0.04 Ū 10 −1.06 ( Ū 10 being the mean wind speed at 10 m). The large values of the drag coefficient at low winds are associated with both near‐neutral and strongly unstable situations. On the other hand, the C D values at Kharagpur are less than at Jodhpur by nearly 50% for wind speeds > 3ms −1 , and cannot be explained by the different roughness lengths at the two sites.