کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5427693 | 1508645 | 2016 | 6 صفحه PDF | دانلود رایگان |
- The absorption cross section of water vapor was studied from 325 to 420Â nm.
- The upper limit was 5Ã10â26Â cm2Â moleculeâ1 above 340Â nm at 0.5Â nm resolution.
- Our result contradicts a recent report of appreciable absorption by water vapor.
There are few experimental measurements of absorption by water vapor in the near-UV. Here we report the results of spectral measurements of water vapor absorption at ambient temperature and pressure from 325Â nm to 420Â nm, covering most tropospherically relevant short wavelengths. Spectra were recorded using a broadband optical cavity in the chemically controlled environment of an atmospheric simulation chamber. No absorption attributable to the water monomer (or the dimer) was observed at the 0.5Â nm resolution of our system. Our results are consistent with calculated spectra and recent DOAS field observations, but contradict a report of significant water absorption in the near-UV. Based on the detection limit of our instrument, we report upper limits for the water absorption cross section of less than 5Ã10â26Â cm2Â moleculeâ1 at our instrument resolution. For a typical, indicative slant column density of 4Ã1023Â cm2, we calculate a maximum optical depth of 0.02 arising from absorption of water vapor in the atmosphere at wavelengths between 340Â nm and 420Â nm, with slightly higher maximum optical depths below 340Â nm. The results of this work, together with recent atmospheric observations and computational results, suggest that water vapor absorption across most of the near-UV is small compared to visible and infrared wavelengths.
Journal: Journal of Quantitative Spectroscopy and Radiative Transfer - Volume 170, February 2016, Pages 194-199