R. Michael Hardesty
My research interests center around development, evaluation, and application of optical remote sensing techniques to investigate atmospheric processes. Lidar techniques can be used to investigate a broad range of phenomena, including boundary layer dynamics, winds and turbulence, air pollution, and greenhouse gas emissions. My colleagues and I deploy lidars to obtain measurements from a variety of stationary and moving platforms, including surface vehicles, ships, aircraft, and satellites. Results of this research improve understanding, modeling, and forecasting of weather and climate processes, identify sources of particulate and gaseous air pollution, and enhance renewable energy production.
My current research is focused on developing and deploying a Doppler lidar in space to measure wind profiles globally. Currently, observations of wind profiles come primarily from radiosondes and aircraft, and are concentrated over land masses and in the northern hemisphere. Scatterometer and atmospheric motion vectors provide additional wind information but are limited in vertical extent. Observing system simulation experiments (OSSEs) indicate that space-based Doppler wind measurements assimilated into numerical forecast models will significantly improve short and medium range weather forecasts as well as reanalysis data sets used in climate studies. Working with Ball Aerospace and a CIRES postdoc, we have been investigating the performance and potential for space deployment of an Optical Autocovariance Wind Lidar (OAWL) based on a Mach-Zender interferometer to measure Doppler shift. The instrument was developed at Ball and tested on a NASA WB-57 aircraft during the summer of 2016 (Figure 1). The OAWL instrument concept is potentially well-suited for a space mission, offering the capability of measuring winds based on scatter of laser light from both molecules and aerosols using one laser transmitter and a single receiver. Primary goal of the WB-57 flights was to assess the accuracy and precision of the instrument and to verify the model used to estimate performance of such a lidar from space. Dropsondes deployed during each flight provided comparison observations to assess accuracy of the lidar measurements.
The aircraft campaign demonstrated the feasibility of the OAWL design to provide space-based, global wind measurements and served as the basis for a proposal to NASA to deploy a Doppler lidar on the International Space Station. A somewhat similar concept for space-based wind measurements has been implemented by the European Space Agency for their Aeolus wind-measuring mission (Figure 2). The Aeolus satellite was launched in August, 2018, and has been providing observations of atmospheric winds from that time. Because this is the first wind lidar in space, an important component of the mission is validation and assessment of instrument performance. The Aeolus project has assembled an international team to calibrate and validate the wind measurements, and to assess the impact of the data for improving weather forecasts. I serve as Principal Investigator for the US team working on Aeolus calibration and validation, coordinating efforts among NASA, NOAA and external partners. The effort includes aircraft and ground-based measurement campaigns, in which Doppler lidar measurements are obtained for direct comparison with Aeolus observations, comparison of Aeolus measurements with winds calculated from tracking cloud and moisture features in satellite images, and assimilation of Aeolus measurements into current numerical forecast models to evaluate forecast impact. Results of these efforts will be used to assess Aeolus performance and to plan future US missions for measuring winds from space-based platforms.