All 2022 webinars

June 24: AMP Workshop on Data QA/QC Self-Review Training

In this video, we summarized the new Data QA/QC self-review process and explained the designs and outputs of Data QA/QC modules.

Download the slide deck here. A recording can be found here

April 27 2022, 12-1:30 PM Pacific Time: Year of Water webinar – Water Limitations on ET

1) Dr. Kiona Ogle (Northern Arizona University): Identifying the timescales over which indices of moisture availability influence ecosystem carbon and water fluxes

Description: Both antecedent (past) and concurrent environmental conditions (such as moisture availability) simultaneously govern ecosystem processes such as net and gross ecosystem exchange of CO₂ (e.g., NEE) and evapotranspiration (ET). The relative importance of antecedent conditions can vary over time and across different ecosystem types, and quantifying the timescales over which those conditions are influential is key to predicting ecosystem responses. This webinar will focus on approaches to exploring the varied timescales over which water limitation affects carbon and water fluxes, and the unique opportunities afforded by flux tower data to rigorously quantify associated lagged responses and antecedent effects of moisture-related drivers.

2) Dr. Steven Kannenberg( University of Utah):  Quantifying the drivers of dryland carbon-water cycling across the soil-plant-atmosphere continuum

Description: Dryland ecosystem processes are highly temporally variable due to transient hydrological dynamics and tightly coupled carbon-water cycles. As such, drylands are poorly represented in many vegetation and land surface models. However, an enhanced understanding of dryland ecosystem function is unfortunately limited by the lack of long-term, co-located, continuous measurements of vegetation physiology, hydrology, and ecosystem fluxes. At a piñon-juniper woodland in southeastern Utah, we amassed a continuous dataset of meteorological conditions, soil water potential from surface to bedrock, tree water potential, and ecosystem carbon and water fluxes. In this talk, I will discuss our efforts to: 1) quantify the drivers of plant water potential and ecosystem fluxes, 2) understand the impact of precipitation pulses on ecosystem function, and 3) uncover the data necessary to properly predict ecosystem processes in this region.

3) Dr. Matt Dannenberg (University of Iowa): Exceptional heat and atmospheric dryness amplified losses of primary production during the 2020 U.S. Southwest hot drought

Description: During summer and autumn 2020, the U.S. Southwest experienced one of the most intense “hot droughts” on record, with record-low precipitation and record-high air temperature and vapor pressure deficit (VPD) across the region. We use this natural experiment to evaluate the effects of hot drought on GPP and decompose those negative GPP anomalies into their constituent meteorological and hydrological drivers. We found a 140 Tg C (>25%) reduction in GPP below the 2015-2019 mean, by far the lowest regional GPP over the Soil Moisture Active Passive satellite record. More than half of the estimated GPP loss was attributable to low soil moisture (likely a combination of record-low precipitation and warming-enhanced evaporative depletion), but record-breaking VPD amplified the reduction of GPP, contributing roughly 40% of the GPP anomaly. VPD is very likely to continue increasing over the next century, likely substantially amplifying drought-induced GPP reductions.

4) Dr. Tonantzin Terrazas ( Instituto de Ecología, UNAM, Mexico): Partitioning evapotranspiration in a multi-species shrubland using stable isotopes (d¹⁸O)

A recording can be found here.

Highlight: MexFlux Webinar Series “Conozcamos los observatorios de MexFlux”

March 4-April 8, every Friday at 2 PM Mexico City time

The webinar series is organized by the MexFlux network, and supported by AMP.

This webinar series will be presented in Spanish!

April 1, 12-1:30 PM Pacific Time: Year of Water webinar – Land-Atmosphere Interactions

Land-atmosphere interactions play an important role in regional and global climate systems. Observations at AmeriFlux sites have helped us to better understand land-atmosphere feedbacks. Combined with observations of the atmospheric boundary layer, which connects the land surface to the free atmosphere, these feedbacks can be further scrutinized. This webinar highlights how both observations and modeling of land-atmosphere interactions can advance our understanding of the water and carbon cycle at AmeriFlux sites.

Confirmed speakers:

1) Juliet Pilewskie and Susanne Wiesner (University of Madison – Wisconsin): Can we quantify eddy covariance footprint variability and source area characteristics using radiosondes?

In the summer of 2019 a group of students launched several radiosondes over the course of a week during the CHEESEHEAD19 experiment to understand boundary layer height variations over time, as well as to quantify differences in the contribution of vegetation types to carbon, energy and water fluxes measured at several eddy covariance towers. Here we give a brief overview of what we learned, which includes documenting temperature and humidity variabilities and magnitudes over different vegetation types, which can be quantified using radiosonde information below the boundary layer height, to better account for variable flux footprint characteristics.

2) Adam Young (Northern Arizona University): Disentangling the relative contribution of multiple drivers to seasonal variation in evapotranspiration across a continental-scale aridity gradient

Evapotranspiration (ET) is a significant ecosystem flux, governing the partitioning of energy at the land surface. Understanding the seasonal pattern and magnitude of ET is critical for anticipating a range of ecosystem impacts. Our analysis used > 100 site years from 20 co-located AmeriFlux and PhenoCam sites to identify the relative controls of seasonal variability in ET, as well as how these controls vary among ecosystems. In this talk, we present our findings from structural equation modeling that highlight how the key drivers of seasonality in bulk surface conductance and evaporative fraction varied among energy- and water-limited ecosystems.

3) Ryann Wakefield (CIRES/NOAA GSL): Observational utility of mixed-layer mixing diagrams to quantify planetary boundary layer budgets 

Mixing diagrams (Betts 1992; Santanello et al. 2009) are a valuable tool for quantifying the relative contributions of planetary boundary layer (PBL) heat and moisture budget components toward daytime PBL evolution. This talk will demonstrate how mixed-layer-based mixing diagrams can be applied to atmospheric and surface flux observations to estimate entrainment fluxes. Observations are imperfect, however, so this talk will also show how uncertainty from various observational sources can be incorporated into the framework.

4) Yunyan Zhang (Lawrence Livermore National Laboratory): Local convections and their interactions with the land surface

Continental shallow cumulus clouds, their transition to deep convection, and their interactions with land surface are very important processes in the climate system. In this study, comprehensive ground-based ARM observations and high-resolution GOES-R satellite measurements are used to investigate the effect of land cover and land heterogeneity length scales on locally generated convections.

A recording can be found here.

February 23/24: AMP Workshop on Data AQ/QC automation

In this video, we summarized our current Data QA/QC process and explained which tests we run for Format QA/QC and Data QA/QC in order to create the published data sets.

Download the slide deck here. A recording can be found here (1st part) and here (2nd part).

January 28, 12-1:30 PM Pacific Time: Year of Water webinar – Sap Flow: Applications, Challenges, and Opportunities

Sap flow measurements have been used by ecophysiologists and ecohydrologists for the past several decades to characterize plant water transport. In addition to improving our understanding of plant-level water dynamics, sap flow data can enhance our understanding of key hydrologic processes within an eddy covariance footprint and within a modeling framework. However, much like eddy covariance data, researchers need to carefully account for challenges associated with instrumentation, data processing, and data interpretation. This webinar highlights four perspectives on important insights that can be gained from sap flow data.

Confirmed speakers:

1) Victor Flo (Imperial College of London, Department of Life Sciences (Silwood Park), Margarita Salas Postdoctoral fellow, Ministry of Universities, Spain):  “Uncertainty in sap flow methods, best practices and new technologies”

Sap flow measurements provide reliable estimates of whole plant transpiration. Although all methods are subjected to measurement uncertainty, their sources of error are well known and can potentially be addressed with calibrations at site and species level. In addition, a new generation of more accurate and cheaper probes will extend the number of sap flow sensors installed and improve estimates of stand transpiration.

2) Georgianne W. Moore (Professor Ecology and Conservation Biology, Texas A&M University):  “Heat dissipation sensors enter a new age: Navigating frontiers in transpiration and hydrologic function”

Thermal dissipation (TD) sensors have been used extensively for a wide array of sap flow applications, and yet recently several limitations of this approach have been identified, including a tendency to underestimate absolute flows, especially in small stems with very high flows. However, when used properly, the TD method remains the most cost effective and reliable approach for determining relative flows in comparison studies. This presentation synthesizes results from numerous field studies and provides guidance on addressing key methodological challenges. The development of “smart” calibration approaches that correct for fundamental effects of radial variation inherent in thermal dissipation studies is discussed.

3) Yakir Preisler (Post-doctorate research fellow, John A. Paulson School Of Engineering And Applied Sciences and at the Department of Organismic and Evolutionary Biology, Harvard University): “Forest tree survival under dry conditions: what enables it and what are the challenges in measuring it?”

Surviving and developing in dryland ecosystems with low water availability and high atmospheric demand for water is a huge challenge for forest trees and is also a challenging task for forest ecophysiologists to measure. Capturing the ecophysiological process at different spatial and temporal resolutions, under harsh conditions is a complicated and important mission. We will explore how these trees survive, what are the main limiting and driving forces, and what are the challenges involved in understanding and measuring that.

4) Ashley M. Matheny (Assistant Professor, Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin): “Trends in plant-water dynamics shed light on complex ecosystem processes”

Often considered supplementary to meteorological and eddy covariance observations, data surrounding water acquisition, storage, and use in vegetation can reveal key plant characteristics which define ecosystem responses to perturbation. New ground and satellite based measurement technologies can now enable feasible, scalable approaches to understanding vegetation hydrodynamics on short timescales (minutes to days). This talk will focus on the centrality of these data for understanding and predicting water, carbon, and energy fluxes in a changing climate.

A recording can be found here.