Connecting Land–Atmosphere Interactions to Surface Heterogeneity in CHEESEHEAD19

The Chequamegon Heterogeneous Ecosystem Energy-Balance Study Enabled by a High-Density Extensive Array of Detectors 2019 (CHEESEHEAD19) is an ongoing National Science Foundation project based on an intensive field campaign that occurred from June to October 2019. The purpose of the study is to examine how the atmospheric boundary layer (ABL) responds to spatial heterogeneity in surface energy fluxes. One of the main objectives is to test whether lack of energy balance closure measured by eddy covariance (EC) towers is related to mesoscale atmospheric processes. Finally, the project evaluates data-driven methods for scaling surface energy fluxes, with the aim to improve model–data comparison and integration. To address these questions, an extensive suite of ground, tower, profiling, and airborne instrumentation was deployed over a 10 km × 10 km domain of a heterogeneous forest ecosystem in the Chequamegon–Nicolet National Forest in northern Wisconsin, United States, centered on an existing 447-m tower that anchors an AmeriFlux/NOAA supersite (US-PFa/WLEF). The project deployed one of the world’s highest-density networks of above-canopy EC measurements of surface energy fluxes. This tower EC network was coupled with spatial measurements of EC fluxes from aircraft; maps of leaf and canopy properties derived from airborne spectroscopy, ground-based measurements of plant productivity, phenology, and physiology; and atmospheric profiles of wind, water vapor, and temperature using radar, sodar, lidar, microwave radiometers, infrared interferometers, and radiosondes. These observations are being used with large-eddy simulation and scaling experiments to better understand submesoscale processes and improve formulations of subgrid-scale processes in numerical weather and climate models

Acceleration intermittency and enhanced collision kernels in turbulent clouds

Scaling arguments suggest that in turbulent clouds, the droplet collision kernel is a fluctuating quantity with peak values at least an order of magnitude greater than the typically used kernel corresponding to droplet sedimentation in still air. These peaks are expected to occur in regions of intense fluid acceleration that are encountered in the fine scales of atmospheric turbulence, characterized by exceedingly large Reynolds numbers and strong energy-dissipation intermittency. The increase in the collision kernel is due to enhanced droplet relative velocities resulting from fluid accelerations and likely is further enhanced by increases in the droplet collision efficiency, which is a function of relative velocity. Velocity data obtained from a turbulent atmospheric flow are presented in order to support the general picture of acceleration intermittency and to estimate its peak values. Several independent estimates all point to the collision kernel as having peak magnitudes several times larger than the traditional kernel that accounts for gravitational acceleration alone. © 2001 Elsevier Science B.V. All rights reserved

Whirlwinds and hairpins in the atmospheric surface layer

Vortices in the atmospheric surface layer are characterized using observations at unprecedented resolution from a fixed array of 31 turbulence sensors. During the day, these vortices likely are dust devils, though no visual observations are available for confirmation. At night, hairpin vortices appear to have been observed. The structure and dynamics of several types of vortices are described and related to other vortex investigations, including tornadoes and hurricanes

Multi-lidar wind resource mapping in complex terrain

Scanning Doppler lidars have great potential for reducing uncertainty of wind resource estimation in complex terrain. Due to their scanning capabilities, they can measure at multiple locations over large areas. We demonstrate this ability using dual-Doppler lidar measurements of flow over two parallel ridges. The data have been collected using two pairs of long-range WindScanner systems operated in a dual-Doppler mode during the Perdigão 2017 measurement campaign. The lidars mapped the flow along the southwest and northeast ridges 80 m above ground level. By nalyzing the collected data, we found that for different flow nditions on average wind speeds are 10% higher over the outhwest ridge compared to the northeast ridge. At the southwest ridge, the data shows, depending on the atmospheric conditions, a change of 20% in wind speed along the ridge. For the measurement period, we have simulated the flow over the site using WRF-LES to compare how well the model can capture wind resources along the ridges. We used two model configurations. In the first configuration, surface drag is based purely on aerodynamic roughness whereas in the second configuration forest canopy drag is also considered

The Niwot Ridge Subalpine Forest US-NR1 AmeriFlux site – Part 1: Data acquisition and site record-keeping

The Niwot Ridge Subalpine Forest AmeriFlux site (US-NR1) has been measuring eddy-covariance ecosystem fluxes of carbon dioxide, heat, and water vapor since 1 November 1998. Throughout this 17-year period there have been changes to the instrumentation and improvements to the data acquisition system. Here, in Part 1 of this three-part series of papers, we describe the hardware and software used for data-collection and metadata documentation. We made changes to the data acquisition system that aimed to reduce the system complexity, increase redundancy, and be as independent as possible from any network outages. Changes to facilitate these improvements were (1) switching to a PC/104-based computer running the National Center for Atmospheric Research (NCAR) In-Situ Data Acquisition Software (NIDAS) that saves the high-frequency data locally and over the network, and (2) time-tagging individual 10 Hz serial data samples using network time protocol (NTP) coupled to a GPS-based clock, providing a network-independent, accurate time base. Since making these improvements almost 2 years ago, the successful capture of high-rate data has been better than 99.98 %. We also provide philosophical concepts that shaped our design of the data system and are applicable to many different types of environmental data collection.Northeastern States Research Cooperative; NSF's Macrosystems Biology program [EF-1065029]; US DOE, Office of Science, through the AmeriFlux Management Project (AMP) at Lawrence Berkeley National Laboratory [7094866]; NSFThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The Impacts of Irrigated and Rainfed Agriculture on Near-Surface Atmosphere: Preliminary Results from GRAINEX

Land use/land cover change (LULCC) has long been viewed as a contributing source of climate change. Modification of natural prairie grasslands to irrigated and rainfed agriculture has proven to have significant impacts on regional weather and climate variables including temperature, precipitation and energy fluxes. These impacts can be visible in various parts of the Great Plains. In this presentation, we have analyzed energy flux and soil moisture data collected during the Great Plains Irrigation Experiment (GRAINEX) in the 2018 growing season. The GRAINEX field campaign includes 12 in-situ integrated surface flux systems; three mobile radar units that also conducted radiosonde balloon launches; 74 temporary weather stations; and two integrated sounding systems that launched radiosonde balloons. Balloon launches were conducted every two hours from sunrise to sunset accumulating to 40 radiosonde balloon launches every day. The data were collected during two intensive observation periods (IOPs) in early June (May 30-June 13, 2018) and late July (July 16-July 30, 2018). Flux and surface meteorological observations were continuous from May through July. Impacts of four different land covers, including, irrigated soybean, irrigated corn, non-irrigated soybean, and non-irrigated corn were quantified by analyses of observed data. The data assessed for this study included sensible and latent heat energy, and equivalent temperature (moist enthalpy). In addition, soil moisture and temperature data were also collected and used to determine how root zone soil moisture affected atmospheric boundary layer variables

BOREAS AFM-3 NCAR Electra 1994 Aircraft Flux and Moving Window Data

The BOREAS AFM-3 team used the NCAR Electra aircraft data to make measurements of the fluxes of momentum, sensible and latent heat, carbon dioxide, and ozone over the entire BOREAS region to tie together measurements made in both the SSA and the NSA in 1994. These data were also used to study the planetary boundary layer using both in situ and remote sensing measurements. This data set contains both the aircraft flux and the moving window data. These data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884) or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC)