Wednesdays at 1:00 p.m. – 2:00 p.m.
(UNLESS OTHERWISE NOTED.)
8/23/2017 — Title coming soon – Emil Cherrington (ESSC), [V/C Rob Griffin]
8/30/2017 — Title coming soon – P.J. Benfield (UAH SMAP), [V/C Larry Carey]
9/06/2017 — A Guide to Lightning Spectroscopy. – Daniel Walker (ESSC), [V/C Phillip Bitzer]
Abstract: Lightning spectroscopy has been a subject of interest for the last 150 years. In the 1960s rigorous studies were done which yielded both qualitative and quantitative information about the physical properties within the lightning channel at stroke level speeds. This information has influenced a variety of research fields within the lightning community since and continues to do so today. This is one of the reasons that we must continue and extend our knowledge of the physics within the channel via spectroscopy. Contemporary camera and dispersing technologies have improved to an extent that we can glean new information from the spectrum of the lightning channel. A brief history of lightning spectroscopy, current research and applications, as well as plans for future research will be discussed.
9/13/2017 — A “Scan” of GPM Precipitation Science Topics at NSSTC. – Walter A. Petersen (NASA), [V/C Larry Carey]
Abstract: NASA’s Global Precipitation Measurement (GPM) mission utilizes spaceborne, aircraft and ground-based measurements to characterize the distribution and variability of precipitation within the Earth system so that we can provide a better understanding of Earth’s water cycle and climate and thereby improve its prediction. The GPM core satellite includes both a dual-frequency precipitation radar (DPR) and microwave radiometer that serve as the reference point for a constellation of other microwave radiometers also in low-earth orbit to collectively provide a global map of precipitation every 30 minutes. The GPM activities at the NSSTC are largely focused on the Ground Validation (GV) aspect of the mission to facilitate satellite retrieval algorithm development and to gauge mission performance from a scientific perspective. This GV approach has entailed several concentrated field campaigns to obtain a diverse set of measurements that are being used to construct the vertical column of precipitation as observed by the GPM core satellite. We build this column by starting with point measurements provided by rain gauges and disdrometers to baseline dual-polarimetric radar retrievals of rainfall that can then be scaled to the satellite footprint. Hence our research activities are largely focused on understanding the DSD characteristics and their variability across different physical processes, locations, meteorological regimes and climates. We will present examples from our GV activities, including findings from the most recent GV field campaign on the Olympic Peninsula where the seasonal precipitation was enhanced from 1.7 m (65 in) near the coast to 4.8 m (189 in) only 50 km away in the mountains.
9/20/2017 — The Cyclone Global Navigation Satellite System (CYGNSS) – Analysis and Data Assimilation for Tropical Convection – Xuanli Li (ESSC), [V/C John Mecikalski]
Abstract: The Cyclone Global Navigation Satellite System (CYGNSS) is a constellation of eight micro-satellite observatories launched in November 2016. CYGNSS observatories receive both direct and reflected signals from Global Positioning System (GPS) satellites to estimate near-surface oceanic winds. CYGNSS differs from other scatterometers by providing unique track-based winds and “cross-sections” of convective storms throughout the tropical oceans, from approximately 38 °S to 38 °N. The retrieval of winds from all other scatterometer satellites is limited to mostly clear sky conditions, therefore making CYGNSS unique. While the primary objective of CYGNSS is to accurately measure near-surface wind speeds through clouds and rain, with an emphasis on tropical cyclone environments, CYGNSS has many other potential applications related to general tropical convection (e.g., the Madden-Julian Oscillation), with rapid updates of winds unbiased by the presence of precipitation. This talk presents a study that leveraged the CYGNSS pre-launch End-To-End Simulator (E2ES)
Abstract: Emerging technologies provide an unprecedented look into lightning occurrence that can be used for scientific, operational, and educational purposes. Lightning measurements from around the Washington, DC metro area in the summer of 2017 are used to examine the physics of lightning discharges and produce resources that highlight hazards posed by lightning. The Geostationary Lightning Mapper (GLM) on the GOES-16 satellite provides continuous measurements of total lightning activity across the hemisphere. The top-down GLM view is augmented with high-speed video from ground-based Phantom cameras and whole-sky spherical video from a 360 camera to compare light escaping the top and lateral boundaries of the cloud. Optical measurements are further supplemented by VHF observations taken by the Washington DC Lightning Mapping Array (DCLMA) that see through the cloud to trace the three-dimensional development of the flash. These combined measurements provide a comprehensive picture of lightning activity in DC thunderstorms that shows how optical emissions from lightning interact with the surrounding cloud.
10/04/2017 — Thunderstorms and Atmospheric Composition: A Meeting of Cloud Physics, Dynamics, Lightning, and Chemistry – Mary Barth (NCAR), [V/C Nair]
Abstract: Upward motions in thunderstorms transport trace gases and aerosols from the boundary layer to the upper troposphere and lower stratosphere creating plumes of photochemically-active chemistry that produce new particles and ozone in the upper troposphere where ozone acts as a greenhouse gas. In the thunderstorms, many complicated processes occur removing some trace gases and producing others (e.g., lightning production of nitrogen oxides (NOx)). Entrainment of air into the storms and thunderstorm-generated stratosphere-troposphere exchange are also important factors in determining how thunderstorms affect the composition in the troposphere. Thus, both in situ chemical production and cloud-scale mixing processes must be considered to understand ozone sources in the upper troposphere.
Analysis and modeling of storms sampled during the 2012 Deep Convective Clouds and Chemistry (DC3) experiment show the importance of cloud physics to the removal of soluble trace gases, illustrate the ability of cloud-scale models to predict lightning flash rates for determining lightning production of NOx, and give an estimated amount of ozone produced in convective outflow plumes. The 22 June 2012 DC3 case in northeastern Colorado is a unique case because one of the storms sampled ingested an elevated (7 km altitude) wildfire smoke plume with measurements in the anvil outflow showing enhanced concentrations as a result of the smoke plume. These measurements can be compared to a second, neighboring storm that was not affected by the smoke plume. I will use the 22 June case to highlight some of the DC3 results on ozone production and to discuss the role of the smoke plume on aerosol-cloud interactions.
Abstract: It has come to light in the past few decades that there is more to lightning than meets the eye. In addition to the well-known optical signature, lightning radiates a powerful electromagnetic pulse (EMP) that can be detected thousands of miles away in the Very-Low-Frequency band (VLF, 3—30 kHz). During the development stages of a lightning discharge, it has also been recently observed that certain types of lightning emit X-rays and gamma-rays, which have been detected on the ground and on satellites.
In just the past 25 years, the effects of lightning in space have been predicted, observed, and explained with theory and modeling. The EMP and the quasi-electrostatic (QES) field created above the thunderstorm cause heating, ionization, and breakdown in the upper atmosphere at 75-90 km, leading to transient luminous events (TLEs) known as elves and sprites. Furthermore, the EMP propagates through the ionosphere and into the magnetosphere, where it can interact with radiation belt particles and cause them to precipitate in the upper atmosphere.
Through VLF and LF signatures on the ground, elves in the lower ionosphere, and lightning-induced electron precipitation (LEP), lightning connects the troposphere to the ionosphere and magnetosphere, and back to the mesosphere. It is this process of lightning-induced electron precipitation (LEP) that is the focus of this talk. After providing an introduction to the physical processes and a discussion of the history of LEP research, I present our most recent work aimed at assessing the local and global effects of LEP in the upper atmosphere and on the radiation belts. I describe our numerical modeling framework for quantifying the effects of LEP. This modeling combines a variety of techniques that operate on scales from a few meters to thousands of kilometers, and time scales from nanoseconds to seconds. Our modeling is able to predict the ionization produced in the upper atmosphere, which is validated with observations using subionospheric VLF transmitter signals. In addition, we predict optical and X-ray emissions that have not yet been observed. A future experiment to image these LEP events either in optical or X-ray emissions would provide valuable insight into the local and global impact of these events on the radiation belts and upper atmosphere.
10/18/2017 — Using Unmanned Aircraft Systems for Severe Local Storms Research and Forecasting – Adam Houston (UNI), [V/C Larry Carey]
Abstract: Technological and regulatory advances over the last decade have made it possible to use unmanned aircraft systems (UAS) to fill data gaps that have so far limited our ability to observe and therefore understand and predict severe local storms. UAS have been, and will continue to be, integrated into field campaigns aimed to advance basic understanding of severe local storms; the data they collect have been assimilated into convection-allowing numerical weather prediction (NWP) models and the impacts have been assessed; and their value filling the most acute information gaps within the stream of real-time data available to operational forecasters has been evaluated. In this talk, previous, active, and future applications of UAS in field campaigns designed to advance understanding of severe local storms will be presented. Results from analysis of UAS data collected on the 10 June 2010 Last Chance supercell during VORTEX2 will be presented as an example. This talk will also address active and future field- and model-based investigations of the potential value of UAS for directly improving storm-scale predictions through assimilation in convection-allowing NWP models. Since UAS data are likely to have value when integrated into the real-time data stream available to operational forecasters, results will also be presented from an evaluation of data needs of National Weather Service forecasters for short-term forecasting and how these needs might be met by UAS. Ultimately, UAS have the potential to transform the surveillance meteorological observation network, but if and how their integration occurs must be informed through quantitative evaluation of their impacts when assimilated into NWP models and integrated into the real-time data stream.
10/25/2017 —Atmospheric Monitoring with a New In Situ Observing System – John Manobianco (Mano Nano Technologies), [V/C Ryan Wade]
Abstract: Technological advancements in electronics integration and miniaturization along with material science have inspired a transformational environmental observing system known as GlobalSense. The system features an ensemble of disposable airborne probes known as environmental Motes or eMotes, that will be carried by wind currents much like naturally occurring dandelion or maple seeds. Two other elements that comprise the system include deployment mechanisms and communication platforms to retrieve sensor data.
GlobalSense has the potential to expand greatly in situ measurements of thermodynamic and kinematic parameters and transform atmospheric sensing well beyond current capability. In the area of severe storm research and operations, there is a need for new systems to measure boundary layer fields at space and time scales that are not currently feasible with current in situ or remote sensing platforms. eMotes would be ideal to provide these observations for studying the initiation and evolution of supercell thunderstorms.
The presentation will highlight efforts to develop and test GlobalSense during the first year of a NOAA-sponsored project. Topics to be covered include enabling technologies and system components, design challenges and constraints, and potential collaboration with stakeholders in the Huntsville weather ecosystem. It will conclude with project milestones for a field experiment in spring 2018 to demonstrate GlobalSense in the atmosphere and future plans to develop a fully operational system.
11/01/2017 — Title coming soon – Stephanie Granger (NASA/JPL Western Water Applications Office), [V/C Chris Hain]
11/08/2017 — Title coming soon – Tim De Smet (Binghamton), [V/C Tom Sever]
11/15/2017 — Student Seminars – ATS Students (UAH ATS), [V/C Phillip Bitzer]
Evaluation of the UAH GOES Insolation Product through Comparison with Pyranometer Measurements
Adviser: Dr. Arastoo Pour-Biazar
A high-resolution measurement of surface insolation is anticipated by various climatological and agricultural researches and applications. The University of Alabama in Huntsville (UAH) has been archiving a high-resolution insolation product based on a simple physical model using Geostationary Operational Environmental Satellite (GOES) observations. This study uses measurements from well-calibrated pyranometers to validate the insolation retrievals rigorously. Preliminary results indicate the product performs well for most cases, while a significant under-estimation is shown for snow-covered locations.
Applications of Satellite Remote Sensing for Monitoring Surface Water Availability for Pastoralists in Remote Areas of the Tahoua Region, Niger
Kelsey E. Herndon
Adviser: Rob Griffin
Ephemeral water bodies are an important source of water for pastoralists and small-scale agriculturalists in the Sahel region of Africa. Over the past 30 years, changing climatic conditions have altered the quantity, quality, and predictability of traditional sources of water normally relied on by these groups. As a scarce but essential resource, increased competition over access to water has contributed to conflict, and sometimes violence, between nomadic pastoralists searching for watering holes for their cattle and the sedentary smallholder farmers that rely on ponds and lakes to irrigate their crops. This project addresses the degree to which satellite remote sensing can be used to monitor the distribution and dynamics of ephemeral water bodies and evaluates how changes in precipitation impact the availability of surface water for pastoralists and smallholder farmers in the Sahel. Thirty years of Landsat imagery were used to characterize inter- and intra-annual trends of surface water extent. Surface water surface area responsiveness to precipitation was also assessed. The results from this analysis will be used to inform best practices for water resource management in the region.
Orographic Impacts on Liquid and Ice-Phase Precipitation Processes during OLYMPEx
Adviser: Walt Petersen
The most recent field campaign of the Global Precipitation Measurement (GPM) mission was the Olympic Mountains Experiment (OLYMPEx). OLYMPEx was a ground and airborne field effort focused on the study of mid-latitude frontal precipitation processes over the mountainous Olympic Peninsula of Washington State, where the terrain gradients and frequent mid-latitude frontal systems pose unique challenges to both satellite and ground-based precipitation measurement. This study takes a ground-based radar approach to examining precipitation processes occurring in clouds and frontal systems interacting with the Olympic Mountains and how these processes may impact GPM space-based measurements.
Using NASA’s S-band polarimetric radar (NPOL) to analyze vertical profiles of hydrometeors as precipitation systems approach the mountains, the polarimetric variables are used to compute ice (IWP), liquid (LWP), and total water paths (TWP) in association with estimated precipitation rate for several cases. These quantities are compared to coincident water contents and related precipitation characteristics measured or estimated by GPM’s Microwave Imager (GMI) and Dual-frequency Precipitation Radar (DPR). However, limitations in measurements over terrain of space-based radiometers and radars impact the degree to which DPR and/or GMI algorithms are able to adequately observe and estimate precipitation over and around orography. Comparing NPOL with GMI and DPR enables the examination of terrain impacts on precipitation processes affecting the relative production and conservation of ice to rainwater mass flux.
Preliminary case study results suggest: 1) the Olympic Mountains force robust enhancements in the liquid and ice microphysical processes on windward slopes; 2) these orographic enhancements alter the rainfall process and relative contributions of integrated liquid and frozen precipitation masses relative to total precipitation mass in the column; 3) DPR and GMI instrument viewing limitations combined with orographic forcing of column liquid and ice processes may impact the relative ability of current retrieval algorithms to estimate near-surface precipitation rates. Ongoing analysis will better isolate synoptic and terrain spatial controls on (2), and better define uncertainties with potential mitigation approaches for (3).
11/22/2017 — Thanksgiving!
11/29/2017 — Student Seminars – ATS Students (UAH ATS), [V/C Phillip Bitzer]