Development of low-cost laser remote sensor for high vertical resolution and continuous measurements of atmospheric water vapor
Remote Sensing Facility
Earth Observing Laboratory
The distribution of water vapor influences dynamical and physical processes that drive weather phenomena, general circulation patterns, radiative transfer, and the global water cycle. Terrestrial boundary layers can be especially complex given the large amplitude of diurnal cycles and surface exchange complexities. A better understanding of the spatial and temporal distribution of water vapor is required to support research, and to improve high impact weather forecasts of quantitative precipitation and damaging winds.
While surface observations abound, vertical profiles of water vapor are largely limited to radiosonde data, which are far too sparse, temporally and spatially, to adequately serve planetary boundary layer research. Laser remote sensing instruments are capable of high vertical resolution and continuous measurements; however, they are traditionally expensive devices to develop and operate. The instrument plus its operational cost is especially relevant since multiple devices – a network of profilers – are required to obtain adequate horizontal spatial resolution. Research applications generally require short term deployments of a regional scale network, whereas National Weather Service and related national forecasts require national networks. For example, in the continental USA, high-resolution vertical profiles of humidity at roughly 400 locations are required. Therefore, a new generation of ‘lower cost’ laser remote sensors – capable of safely, accurately, continuously, and autonomously measuring water vapor in the lower troposphere with high vertical resolution – are needed to lower the barrier to investment.
This seminar discusses the development and testing of a next generation laser remote profiler for water vapor which has the potential to enable a regional and national scale network. The electrically-pumped semiconductor-based laser transmitter is inherently low-maintenance, low-cost, and designed to be eye-safe at the exit port. It has the characteristics necessary for the differential absorption lidar technique; rapid frequency agility with good spectral purity, and when combined with ultra-narrowband multistage optical filters in the receiver, the system provides continuous profiles of water vapor with complete coverage – including periods of bright clouds – from 300 m above ground level to 4 km (or cloud base, whichever comes first) with 150 m nominal vertical resolution and 1 minute temporal resolution. Results from the initial field test in 2014, which includes inter-comparisons with radiosondes and an infrared radiometer, will be discussed. This ‘lower cost’ lidar design may be a significant step towards improving our understanding of the distribution of atmospheric water vapor.
Tuesday, 3 March 2015, 3:30PM
3450 Mitchell Lane
Bldg. 2 Large Auditorium (Rm 1022)
Webcast Link: http://www.fin.ucar.edu/it/mms/fl-live.htm