Refaat T.F.,Old Dominion University |
Ismail S.,NASA |
Nehrir A.R.,NASA |
Hair J.W.,NASA |
And 3 more authors.
Optics Express | Year: 2013
Methane is an efficient absorber of infrared radiation and a potent greenhouse gas with a warming potential 72 times greater than carbon dioxide on a per molecule basis. Development of methane active remote sensing capability using the differential absorption lidar (DIAL) technique enables scientific assessments of the gas emission and impacts on the climate. A performance evaluation of a pulsed DIAL system for monitoring atmospheric methane is presented. This system leverages a robust injection-seeded pulsed Nd:YAG pumped Optical Parametric Oscillator (OPO) laser technology operating in the 1.645 μm spectral band. The system also leverages an efficient low noise, commercially available, InGaAs avalanche photo-detector (APD). Lidar signals and error budget are analyzed for system operation on ground in the range-resolved DIAL mode and from airborne platforms in the integrated path DIAL (IPDA) mode. Results indicate system capability of measuring methane concentration profiles with <1.0% total error up to 4.5 km range with 5 minute averaging from ground. For airborne IPDA, the total error in the column dry mixing ratio is less than 0.3% with 0.1 sec average using ground returns. This system has a unique capability of combining signals from the atmospheric scattering from layers above the surface with ground return signals, which provides methane column measurement between the atmospheric scattering layer and the ground directly. In such case 0.5% and 1.2% total errors are achieved with 10 sec average from airborne platforms at 8 km and 15.24 km altitudes, respectively. Due to the pulsed nature of the transmitter, the system is relatively insensitive to aerosol and cloud interferences. Such DIAL system would be ideal for investigating high latitude methane releases over polar ice sheets, permafrost regions, wetlands, and over ocean during day and night. This system would have commercial potential for fossil fuel leaks detection and industrial monitoring applications. © 2013 Optical Society of America.
Bubbleology Research International LLC | Date: 2013-05-02
There is disclosed systems and methods for barring the advance of an oil spill from one area to another, or for corralling such an oil spill. The systems provide area bubble plumes of air that remain coherent to reaching the surface, in contrast to previous bubble curtains under waves. The area bubble plume may be formed by a plurality of parallel sparger elements that provide a wide plume of bubbles, and are suspended below the surface no more than 10 m. The sparger elements may be mounted in a matrix of structural support members. A series of discrete segments of the system can be connected together to form a flexible chain. The connected segments are desirably coiled around the spool on the rear end of a vessel for easy deployment. The sparger elements are desirably tubular and made of the porous, resistive material that requires a greater luminal pressure than the exterior pressure to create fine bubbles.