Spectral analysis of wind and temperature components during lightning in pre-monsoon season over Ranchi

Meteorological Applications

Kumar

et al. 2020

Self Cite

Turbulence observations over an Indian region are used to examine the observational behaviour of stability‐correction functions for momentum ( φ m) and heat ( φ h) under stable conditions within the framework of Monin–Obukhov similarity theory. The φ m is observed to follow the linear functional form in the case of near‐neutral to moderately stable conditions. However, φ m is found to increase with a relatively slower rate as compared with the linear form in strongly stable conditions. A large scatter in φ h is observed with the near‐neutral condition, and they tend to level off in very stable conditions. The optimized co‐efficients appearing in the functional form of φ m suggested by Grachev et al. in 2007 are derived using turbulence observations. The present study recommends the use of these optimized functional forms of φ m and φ h for the estimation of surface fluxes over an Indian region in atmospheric models.

Section: A Brief Description Of Site and Data Setmentioning

confidence: 99%

On stability correction functions over the Indian region under stable conditions

Meteorological Applications

Kumar

et al. 2020

Self Cite

“…We have further carried out data analysis to support the findings of Srivastava and Sharan (2015). The dataset used in the present study is obtained from a fast response sensor (CSAT3 sonic anemometer) installed at 10 m height in the Birla Institute of Technology Mesra, Ranchi (23.4128N, 85.4408E), India, with an average elevation 609 m above sea level (Dwivedi et al 2015;Sharan and Srivastava 2016;Srivastava and Sharan 2017). Turbulence measurements at 10 Hz frequency for the year 2009 are used to calculate the hourly turbulent fluxes using the eddy covariance technique.…”

Section: Observational Evidence and Recommendation For The Form Of U ...mentioning

confidence: 96%

Uncertainty in the Parameterization of Surface Fluxes under Unstable Conditions

Journal of the Atmospheric Sciences

2021

In this study, an attempt has been made to analyze the possible uncertainties in the parameterization of surface fluxes associated with the form of non-dimensional wind and temperature profile functions used in weather and climate models under convective conditions within the framework of Monin-Obukhov similarity theory (MOST). For this purpose, these functions, which are commonly known as similarity functions, are classified into four categories based on the resemblance in their functional behaviour. The bulk flux algorithm is used for the estimation of transfer coefficients of momentum and heat using four different classes of similarity functions. Uncertainty in the estimated values of fluxes is presented in the form of deviation in the predicted values of momentum and heat transfer coefficients and their variation with the Monin-Obukhov stability parameter. The analysis suggests that a large deviation in the values of estimated fluxes might occur if different forms of similarity functions are utilized for the estimation of surface fluxes. Recommendations are made for the form of similarity function for momentum based on the analysis of one year-long turbulence observations over an Indian region. The study suggests that there is a distinct need to carry out a careful analysis of turbulence data in free convective conditions for determining a consistent functional form of the similarity functions to be utilized in the atmospheric models universally.

“…The first data set used in the present study is obtained from a fast response sensor (CSAT3 Sonic anemometer) installed at 10‐m height in the Birla Institute of Technology Mesra, Ranchi (23.412°N, 85.440°E), India, with an average elevation 609 m above sea level (http://odis.incois.gov.in/index.php/project-datasets/ctcz-programme/data; Dwivedi et al, ). There are few buildings, residential houses, agricultural land, and dense trees near the site.…”

Section: Observational Datamentioning

confidence: 99%

Analysis of Dual Nature of Heat Flux Predicted by Monin‐Obukhov Similarity Theory: An Impact of Empirical Forms of Stability Correction Functions

2019

JGR Atmospheres

The behavior of sensible heat flux H with stability parameter ζ in the stable atmospheric surface layer is analyzed within the framework of Monin‐Obukhov similarity theory (MOST). Using MOST equations, H is expressed as a function of ζ and wind shear ∂U/∂z. A systematic mathematical analysis is carried out to analyze the behavior of H with ζ utilizing the linear as well as various nonlinear empirical functional forms of the similarity functions. In case of linear form, for a given value of H, two different values of ζ along with the “downward heat flux maximum” with a unique critical point are found to occur. However, for the other selected empirical similarity functions, more than two values of ζ having the same magnitude of H may occur suggesting the existence of multiple critical points. Further, the observational variation of H with ζ is analyzed using data from three different sites. Data suggest the existence of two different stability regimes for the same magnitude of heat flux. However, the data do not support the existence of multiple values of ζ for the same magnitude of H, as predicted by MOST with the other selected empirical forms of similarity functions. This suggests that the phenomenon of existence of downward heat flux maximum, as predicted by MOST equations, depends on the functional form of the similarity functions, and it appears to break down for some selected empirical forms of similarity functions under very stable conditions.