ARM Raman lidar data provide insights into turbulence structure in the tropics.
The lowest portion of the atmosphere that is directly influenced by its contact with the Earth’s surface is called the atmospheric boundary layer. During the daytime, solar heating of the surface drives convective mixing and turbulence in the convective boundary layer. Accurately representing turbulence in numerical models is critical because turbulence mixes mass, momentum, and energy within the convective boundary layer. Since turbulence works on a range of scales it must be parameterized in these models. This study examines detailed profiles of water vapor turbulence using the Raman lidar observations from the Atmospheric Radiation Measurement (ARM) Tropical Western Pacific (TWP) site located at Darwin, Australia in order to calculate statistical moments of the turbulence profiles that are often used in turbulence parameterizations. These were compared to statistics from a similar Raman lidar at a midlatitude site, the ARM Southern Great Plains site in Oklahoma.
This study presented the first vertical profiles of water vapor turbulence from a ground-based lidar at a tropical site. The study found striking differences in these variables among the tropical wet season, tropical dry season, and midlatitude cases. The tropical wet season differed greatly from the dry season, while the tropical dry season and the SGP site were more similar. The main drivers of this marked seasonality difference in the profiles are the moist maritime air masses that come from the ocean as a part of monsoonal atmospheric circulation in northern Australia and also the relatively strong mixing in the entrainment zone during the wet season. This study demonstrates the value of the continuous, long-term, high temporal, and vertical resolution observations of water vapor from the ARM Raman lidars. The unique data set of the profiles of turbulent statistics presented here can be used for validation of similarity relationships (often used in boundary layer parameterizations), which have traditionally been evaluated only by large eddy model simulations.
This study explored water vapor turbulence in the convective boundary layer 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 convective boundary layer is cloud-free, quasi-stationary, and well mixed. The study 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. The variance and coefficient of the structure function show qualitatively the same vertical pattern. Furthermore, deeper convective boundary layer, larger gradient of water vapor mixing ratio at height of maximum variance, and the strong correlation with the water vapor variance are seen during the dry season. These continuous, long-term, high temporal and vertical resolution observations of water vapor are valuable to evaluate the performance of turbulence parameterization schemes in models in the convective boundary layer, which are essential for improved weather forecasts, regional climate projections, and simulating convection initiation and the formation of clouds and precipitation.
Contacts (BER PM)
ARM Program Manager
ASR Program Manager
M. K. Osman
The University of Oklahoma and NOAA/National Severe Storms Laboratory,
This work was supported by the U.S. Department of Energy Atmospheric System Research (ASR) program via grant DE-SC0014375. The data used were collected as part of the Atmospheric Radiation Measurement (ARM) program and are available from the ARM data archive at http://www.arm.gov.
Osman M, D Turner, T Heus, and R Newsom. "Characteristics of Water Vapor Turbulence Profiles in Convective Boundary Layers During the Dry and Wet Seasons over Darwin." Journal of Geophysical Research: Atmospheres, 123(10), 4818-4836 (2018). [DOI:10.1029/2017JD028060]
SC-33.1 Earth and Environmental Sciences Division, BER
BER supports basic research and scientific user facilities to advance DOE missions in energy and environment. More about BER
Jan 11, 2022
No Honor Among Copper Thieves
Findings provide a novel means to manipulate methanotrophs for a variety of environmental and in [more...]
Dec 06, 2021
New Genome Editing Tools Can Edit Within Microbial Communities
Two new technologies allow scientists to edit specific species and genes within complex laborato [more...]
Oct 27, 2021
Fungal Recyclers: Fungi Reuse Fire-Altered Organic Matter
Degrading pyrogenic (fire-affected) organic matter is an important ecosystem function of fungi i [more...]
Oct 19, 2021
Microbes Offer a Glimpse into the Future of Climate Change
Scientists identify key features in microbes that predict how warming affects carbon dioxide emi [more...]
Aug 25, 2021
Assessing the Production Cost and Carbon Footprint of a Promising Aviation Biofuel
Biomass-derived DMCO has the potential to serve as a low-carbon, high-performance jet fuel blend [more...]
List all highlights (possible long download time)