Estimation and numerical simulation of atmospheric surface layer parameters at Mangalore, west coast of India

Abstract

Atmospheric surface layer meteorological observations obtained from 20 m height meteorological tower at Mangalore University campus, situated along the west coast of India, are used to estimate the surface layer scaling parameters of roughness length (zo) and drag coefficient (CD) and the surface layer fluxes of sensible heat and momentum. These parameters are computed using the simple flux-profile relationships under the framework of Monin-Obukhov (M-O) similarity theory. The estimated values of zo are higher (1.35-1.54 m) than the reported values in the literature (>0.4-0.9 m), probably due to the undulating topography surrounding the location. The magnitude of CD is high for low wind speed (<1.5 m/s) and found to be in the range of 0.005-0.03. The variations of sensible heat fluxes (SHFs) and momentum fluxes (MFs) are also discussed. Relatively high fluxes of heat and momentum are observed during typical days on 26-27 February 2004 and 10-11 April 2004, due to the daytime unstable atmospheric conditions. Stable or near neutral conditions prevail after 1700 h IST with negative SHF. A mesoscale model PSU/NCAR MM5 is run using a high-resolution (1 km) grid over the study region to examine the influence of complex topography on the surface layer parameters and the simulated fluxes are compared with the estimated values. Spatial variations of the friction velocity (u*), CD, surface fluxes, planetary boundary layer(PBL) height and surface winds are observed according to the topographic variations in the simulation. © 2011 Royal Meteorological Society © 2011 Royal Meteorological Society.