The investigators will conduct a five-year research program to develop a lidar sensor for the Arctic using state-of-the-art devices and a novel Internet-based data transport system to enable advancements in arctic atmospheric science. In particular, the lidar development will involve sensitive photon-counting detectors including a new infrared photon detector, a unique dual-polarized laser transmitter, and novel timing schemes to make Rayleigh-Mie-Raman (RMR) measurements from 5 to 90 km in altitude. Analysis of the RMR lidar measurements will provide unique vertical profiles of temperature and aerosol backscatter strength, extinction, shape and size from the arctic troposphere through the mesosphere with a vertical resolution of tens of meters and a temporal resolution of tens of minutes. These observations will be applicable to studies of polar stratospheric clouds, aerosols, and the vertical thermal structure of the winter arctic stratosphere. Remote operations will allow more event-driven operations, such as during stratospheric warming events, and, in general, more observing opportunities. The ultimate objective of the data transport system will be to make the lidar system accessible from remote locations and pave the way for the development of fully autonomous lidar systems. This capability would provide greater opportunity for lidar deployments in remote arctic locations with limited infrastructure. The observations will contribute to a distributed network of temperatures and aerosol measurements to support the Network for Detection of Stratospheric Change. The project will involve a graduate student, who will be trained in lidar technologies and stratospheric dynamics, and the data acquired will be rapidly and broadly disseminated for use by other researchers. Not only will the measurements and scientific results contribute to community-wide issues, but they will also be useful for calibration and validation of current and future spacecraft missions designed to observe middle atmosphere temperatures and aerosols.
, ATM 0454999, was a six-year project with activities performed within the Aerospace Engineering Sciences Department at the University of Colorado at Boulder (UCB), at SRI International via a subcontract, and at the NSF Sondrestrom Upper Atmosphere Research Facility near Kangerlussuaq, Greenland. The project was to advance lidar capabilities at the Sondrestrom facility to explore the properties of the Arctic polar atmosphere from the troposphere to the mesosphere (3 km – 90 km altitude). Lidars, also known as laser radars, are unique in their ability, as an atmospheric remote sensing instrument, to provide height-resolved measurements of temperature, winds, constituent gas concentrations, clouds, and aerosols from the Earth’s surface to the edge of space. The region of the Earth’s atmosphere above the troposphere is called the stratosphere, where critical arctic processes take place – such as polar stratospheric cloud formation leading to ozone destruction and polar stratosphere dynamics that may affect tropospheric weather. It is this region of the atmosphere that is the focus for the lidar measurements under this project. We have developed the only Rayleigh / Mie / Raman (RMR) lidar in Greenland, called the Arctic Lidar Technology Experiment (ARCLiTE). This system complements the few lidar stations with such a capability in Andenes, Norway; Ny-Alesund, Svalbard; Kiruna, Sweden; and Eureka, Canada, and adds much needed scientific infrastructure to the Arctic. The ARCLiTE system has the added capability of analyzing the polarization scattering properties of aerosols and clouds in the Arctic. The ARCLiTE system operates weekly and distributes its data to two international community databases called the Coupling, Energetics and Dynamics of Atmospheric Regions and the Network for the Detection of Atmospheric Composition Change. A second lidar system dedicated to studying polarization properties of aerosols / clouds from the surface through the troposphere in the Arctic was developed partially under this grant. The Cloud, Aerosol Polarization and Backscatter Lidar (CAPABL) was developed by PhD students under this grant with substantial assistance by the National Oceanographic and Atmospheric Administration. This lidar was deployed to Summit Camp, Greenland in the summer of 2010. Two images are provided showing the ARCLiTE facility near Kangerlussuaq, Greenland (67°00' N, 59°06' W) and the CAPABL facility at Summit Camp, Greenland (72°35' N, 38°27' W). The polarization measurements from ARCLiTE and CAPABL have enabled new developments in characterizing aerosol shape. This shape determination is used to identify whether clouds consist of liquid water (spherical) or ice crystals (nonspherical). The lidar results have led to a new formulation for polarization lidar improving the accuracy and precision of the measurement. A new polarization technique has also evolved from this effort to determine not only shape but whether atmospheric ice crystals are preferentially oriented or randomly oriented. Often random orientation is assumed but we have detected oriented ice crystals in the atmosphere using novel polarization measurements. Oriented particles scatter incoming radiation more efficiently back to space and will alter the radiative balance of the Earth. The new polarization techniques we have developed have led to new applications beyond atmospheric aerosols and clouds. Our research has been applied to water depth measurements and has led to a factor of 100 improvement in measuring, from a distance, shallow water depths. Most lidar water systems are limited to measuring depths in excess of 1 meter. Our approach has demonstrated water depth measurements as shallow as 1 cm and with much simpler instrument specifications. This finding has led to the filing of a provisional patent in water depth measurements. Another finding under this project has been the height-resolved profiling of water vapor through the troposphere. Water vapor is a critical measurement to understand the water cycle in the Arctic – particularly under today’s changing Arctic climate. A Raman-scattering measurement technique of molecular nitrogen and molecular water vapor has led to one of the few routine measurements of troposphere water vapor mixing ratio in the Arctic. A new finding from our observations in the upper atmosphere has been the formation of weather-like fronts that are similar in construction to fronts that occur in the troposphere. These front-like dynamical structures are tied to planetary scale size disturbances and may play a role in the climate evolution of dynamical patterns in the stratosphere and troposphere. This project has led to the training and development of numerous students. Five PhD students have worked at various levels on this project and four of these PhD students will use these lidar measurements as substantial elements of their PhD thesis – one completing his thesis this year was exclusively supported under this grant. Another student has earned her Masters degree using this lidar data as a central component of her thesis. Two undergraduate students were supported under this project to gain research experience and contribute to these areas of study.
