Optical Refractive Index of Air: Dependence on Pressure, Temperature and Composition

Owens, James C.

doi:10.1364/ao.6.000051

Cited by 506 publications

(186 citation statements)

References 8 publications

(7 reference statements)

Supporting

Mentioning

173

Contrasting

Unclassified

Order By: Relevance

“…Climatological seasonally varying ozone profiles have been taken, obtained from the nearby Meteorological Observatory Hohenpeißen-berg of the German Weather Service. The Rayleigh backscatter coefficients have been calculated from the very accurate algorithm provided by Owens (1967) and King factors obtained from a least-squares fit to the wavelength-dependent data by Bates (1984).…”

Section: Lidar Systemsmentioning

confidence: 99%

“…The data were converted to 532.26 nm by assuming a λ −1.4 wavelength dependence (Jäger andDeshler, 2002, 2003) and then averaged within the standard 75 m vertical bins of the aerosol lidar. For the conversion of the Rayleigh backscatter coefficient a factor of 5.9605 was used, again derived from the algorithm by Owens (1967) and the data by Bates (1984). Because of narrow-band filtering of the DIAL return just the contribution of Raman Q branch was included, calculated from the King factor.…”

Section: Lidar Systemsmentioning

confidence: 99%

See 1 more Smart Citation

35 yr of stratospheric aerosol measurements at Garmisch-Partenkirchen: from Fuego to Eyjafjallajökull, and beyond

et al. 2013

View full text Add to dashboard Cite

Lidar measurements at Garmisch-Partenkirchen (Germany) have almost continually delivered backscatter coefficients of stratospheric aerosol since 1976. The time series is dominated by signals from the particles injected into or formed in the stratosphere due to major volcanic eruptions, in particular those of El Chichon (Mexico, 1982) and Mt Pinatubo (Philippines, 1991). Here, we focus more on the long-lasting background period since the late 1990s and 2006, in view of processes maintaining a residual lower-stratospheric aerosol layer in absence of major eruptions, as well as the period of moderate volcanic impact afterwards. During the long background period the stratospheric backscatter coefficients reached a level even below that observed in the late 1970s. This suggests that the predicted potential influence of the strongly growing air traffic on the stratospheric aerosol loading is very low. Some correlation may be found with single strong forest-fire events, but the average influence of biomass burning seems to be quite limited. No positive trend in background aerosol can be resolved over a period as long as that observed by lidar at Mauna Loa. We conclude that the increase of our integrated backscatter coefficients starting in 2008 is mostly due to volcanic eruptions with explosivity index 4, penetrating strongly into the stratosphere. Most of them occurred in the mid-latitudes. A key observation for judging the role of eruptions just reaching the tropopause region was that of the plume from the Icelandic volcano Eyjafjallajökull above Garmisch-Partenkirchen (April 2010) due to the proximity of that source. The top altitude of the ash above the volcano was reported just as 9.3 km, but the lidar measurements revealed enhanced stratospheric aerosol up to 14.3 km. Our analysis suggests for two or three of the four measurement days the presence of a stratospheric contribution from Iceland related to quasi-horizontal transport, differing from the strong descent of the layers entering Central Europe at low altitudes. The backscatter coefficients within the first 2 km above the tropopause exceed the stratospheric background by a factor of four to five. In addition, Asian and Saharan dust layers were identified in the free troposphere, Asian dust most likely even in the stratosphere

show abstract

Section: Lidar Systemsmentioning

confidence: 99%

Section: Lidar Systemsmentioning

confidence: 99%

35 yr of stratospheric aerosol measurements at Garmisch-Partenkirchen: from Fuego to Eyjafjallajökull, and beyond

et al. 2013

View full text Add to dashboard Cite

show abstract

“…verification of the dispersion and higher order derivatives with astronomical interferometry [71], 5. review formulas [14,35,55,63], 6. theoretical summation of electronic transitions [16,30,31,46].…”

Section: Scopementioning

confidence: 99%

Refractive index of humid air in the infrared: model fits

Mathar¹

2007

J. Opt. A: Pure Appl. Opt.

110

View full text Add to dashboard Cite

The theory of summation of electromagnetic line transitions is used to tabulate the Taylor expansion of the refractive index of humid air over the basic independent parameters (temperature, pressure, humidity, wavelength) in five separate infrared regions from the H to the Q band at a fixed percentage of Carbon Dioxide. These are least-squares fits to raw, highly resolved spectra for a set of temperatures from 10 to 25 • C, a set of pressures from 500 to 1023 hPa, and a set of relative humidities from 5 to 60%. These choices reflect the prospective application to characterize ambient air at mountain altitudes of astronomical telescopes. The paper provides easy access to predictions of the refractive index of humid air at conditions that are typical in atmospheric physics, in support of ray tracing [5] and astronomical applications [4,16,47,50] until experimental coverage of the infrared wavelengths might render these obsolete. The approach is in continuation of earlier work [46] based on a more recent HITRAN database [60] plus more precise accounting of various electromagnetic effects for the dielectric response of dilute gases, as described below.The literature of optical, chemical and atmospheric physics on the subject of the refractive index of moist air falls into several categories, sorted with respect to decreasing relevance (if relevance is measured by the closeness to experimental data and the degree of independence to the formalism employed here):1. experiments on moist air in the visible [3,9,18,53 [42,61,79] and eventually in the static limit [24], the refractive index plotted as a function of wavelength is more and more structured by individual lines. Since we will not present these functions at high resolution but smooth fits within several bands in the infrared, their spiky appearance sets a natural limit to the far-IR wavelength regions that our approach may cover. II. DIELECTRIC MODEL A. MethodologyThe complex valued dielectric function n(ω) of air n = 1 +χ (1) is constructed from molecular dynamical polarizabilitiesN m are molecular number densities, S ml are the line intensities for the transitions enumerated by l. ω 0ml are the transition angular frequencies, Γ ml the full linewidths at half maximum. c is the velocity of light in vacuum, and i the imaginary unit. The line shape (2) adheres to the complex-conjugate symmetry χ m (ω) = χ * m (−ω), as required for functions which are real-valued in the time domain. The sign convention of Γ ml merely reflects a sign choice in the Fourier Transforms and carries no real significance; a sign in the Kramers-Kronig formulas is bound to it. The integrated imaginary part is [28] whereν = k/(2π) = ω/(2πc) = 1/λ is the wavenumber.

show abstract

“…The refractive index of air depends heavily on the pressure, temperature, and humidity, and the theoretical conversion from pressure to refractive index is calculated from the work of Owens et al, 21 using their formulas for dry CO 2 -free air. The refractive index of dry CO 2 -free air is to a very good approximation linear with pressure in the range of interest n = 1 + 2.5834 ϫ 10 −7 /mbar P. ͑5͒…”

Section: ͑1͒mentioning

confidence: 99%

The influence of refractive index change and initial bending of cantilevers on the optical lever readout method

Dohn

Greve

Svendsen

et al. 2010

Review of Scientific Instruments

View full text Add to dashboard Cite

It has been speculated that the initial bending of cantilevers has a major influence on the detector signal in a cantilever-based sensor using the optical lever readout method. We have investigated theoretically as well as experimentally the changes induced in the detector signal when the optical lever technique is used to monitor a cantilever with initial bending during changes in the refractive index of the surrounding media. We find that for changes in refractive index as small as 10−4 the detector signal is highly dependent on the initial bending of the cantilever. The findings are validated experimentally using an environmental chamber and varying the pressure. We sketch routes to circumvent the problem and formulas suitable for data treatment are given.

show abstract

Optical Refractive Index of Air: Dependence on Pressure, Temperature and Composition

Cited by 506 publications

References 8 publications

35 yr of stratospheric aerosol measurements at Garmisch-Partenkirchen: from Fuego to Eyjafjallajökull, and beyond

35 yr of stratospheric aerosol measurements at Garmisch-Partenkirchen: from Fuego to Eyjafjallajökull, and beyond

Refractive index of humid air in the infrared: model fits

The influence of refractive index change and initial bending of cantilevers on the optical lever readout method

Contact Info

Product

Resources

About