Characteristics of Water Vapor Turbulence Profiles in Convective Boundary Layers During the Dry and Wet Seasons Over Darwin. Issue 10 (17th May 2018)

• Record Type: Journal Article
• Authors: Osman, M. K.; Turner, D. D.; Heus, T.; Newsom, R.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 10(2018)
• Page Start: 4818
• Page End: 4836
• Publication Date: 2018-05-17
• Subjects: Raman lidar -- water vapor turbulence -- wet and dry seasons -- coefficient of the structure function -- Darwin -- Oklahoma; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2017JD028060
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: This study explores water vapor turbulence in the convective boundary layer (CBL) using the Raman lidar observations from the Atmospheric Radiation Measurement site located at Darwin, Australia. An autocovariance technique was used to separate out the random instrument error from the atmospheric variability during time periods when the CBL is cloud‐free, quasi‐stationary, and well mixed. We identified 45 cases, comprising of 8 wet and 37 dry seasons events, over the 5‐year data record period. The dry season in Darwin is known by warm and dry sunny days, while the wet season is characterized by high humidity and monsoonal rains. The inherent variability of the latter resulted in a more limited number of cases during the wet season. Profiles of the integral scale, variance, coefficient of the structure function, and skewness were analyzed and compared with similar observations from the Raman lidar at the Atmospheric Radiation Measurement Southern Great Plains (SGP) site. The wet season shows larger median variance profiles than the dry season, while the median profile of the variance from the dry season and the SGP site are found to be more comparable particularly between 0.4 and 0.75 z i . The variance and coefficient of the structure function show qualitatively the same vertical pattern. Furthermore, deeper CBL, larger gradient of water vapor mixing ratio at z i, and the strong correlation with the water vapor variance at z i are seen during the dry season. The median value in the skewness is mostly positive below 0.6 z i unlike the SGP site. Key Points: Analysis of water vapor turbulence profiles was performed for the wet and dry season cases separately Comparisons of turbulent statistics revealed that the dry season is more comparable to observations in Oklahoma than to the wet season The dry season showed deeper CBL, larger gradient of water vapor mixing at z i, and smaller variance