Characteristics of turbulent fluxes of sensible heat and momentum in the surface boundary layer during the Indian summer monsoon

Abstract

Turbulent fluctuations of wind and temperature were measured using a three-component sonic anemometer at 8 m on a 30 m micro-meteorological tower erected at the Indian Institute of Technology (IIT) Kharagpur (22.3" N, 87.2" E), India, as part of the Monsoon Trough Boundary Layer Experiment (MONTBLEX). Diurnal and nocturnal variations of fluxes of sensible heat and momentum were estimated by the eddy correlation technique from 42 observations, each of 10 min duration during 6-8 July in the monsoon season of 1989. The estimated heat flux shows a diurnal trend while the momentum flux shows variability but no particular trend. The nocturnal heat flux changes sign intermittently. Fluctuations of vertical wind velocity u,, and temperature oH when normalised with the respective scaling parameters IL* and 0, are found to scale with Z/L in accordance with the Monin-Obukhov similarity hypothesis: & x (Z/L)"', +e x (ZIL)m"3 during unstable conditions and 4,, x (Z/L), & = (Z/L)-'during stable conditions. Correlation coefficients for heat and momentum flux Y,,+ and Y~,,~ show stability dependence. For unstable conditions, y,, B increases with increasing /Z/L 1 whereas Y!,,~ decreases. During stable conditions, Y,~@ decreases with increasing Z/L while Y,,,~ decreases very slowly from a value -0.36 to -0.37.

Assessment of difference in the atmospheric surface layer turbulence characteristics during thunderstorm and clear weather days over a tropical station

“…1e-f )) and almost fall in line within the stability range from − 0.1 to 0.1 as noticed by Krishnan and Kunhikrishnan [14]. With instability, the w ∕u * increases and follow 1/3 power law as observed by previous studies [23,29]. The difference of present relationships from the relationships given in the literature is explaining the seasonal and site-specific characteristics of such relationships in the neutral region.…”

“…[11,19]. The relationship of the normalised standard deviation of temperature ( T ∕T * ) and ζ has been reported by various researchers time to time over different regions [22,29,36].…”

Energy Mechanism of Atmospheric Boundary Layer Development Over the Tibetan Plateau

“…It is well known that the turbulent development of the CBL is affected by the surface heat flux (Avolio et al., 2017; Båserud et al., 2020; Maronga & Raasch, 2013; Sellers et al., 1995; Yi et al., 2001). The surface heat and momentum fluxes determine the intensity of the CBL turbulent diffusion, and the heat and water vapor flux also affect the formation of boundary layer clouds (Cava et al., 2006; Mahrt, 2000; Sivaramakrishnan et al., 1992; Su et al., 2018). Yi et al.…”

A Case Study of Turbulence in the Nocturnal Boundary Layer During the Indian Summer Monsoon

“…Grossman and Durran (1984) studied the interaction between low-level flow observed during the Indian summer monsoon and the Western Ghats mountain range to examine the possible influence of complex topography on the intensification of offshore convection. Analysis by Sivaramakrishnan et al (1992) showed the importance of downward transport of momentum and sensible heat during the night-time under near-neutral stability. It was also shown that momentum transfer occurs in bursts, under the influence of large-scale circulations during monsoon conditions while the diurnal and seasonal variation of the monsoon LLJ has been studied by, e.g., Ardanuy (1979); Kalapureddy et al (2007); Nair et al (2014).…”