Long term NO2 measurements in Hong Kong using LED based Long Path Differential Optical Absorption Spectroscopy.

The article presents a study to measure the atmospheric nitrogen dioxide with the use of long path differential optical absorption spectroscopy (LP-DOAS) based on light emitting diode (LED) in Hong Kong, China. The instrument uses a high power blue LED coupled into a telescope using a Y-fibre bundle. It uses the long-term data set in validating the ozone monitoring instrument (OMI) data product. The study finds that LP-DOAS detects a weekly cycle that the OMI cannot observe.