Simultaneous measurement of stratospheric O 3 , H 2 O, CH 4 , and N 2 O profiles from infrared limb thermal emissions

A quantitative analysis of continuum absorptions in the lower stratosphere is reported based on infrared solar absorption spectra recorded in the occultation mode at 0.01 cm−1 resolution. The spectra were obtained during seven sunrises near 48°S latitude and 12 sunsets near 28°N latitude with the atmospheric trace molecule spectroscopy (ATMOS) Fourier transform spectrometer operating April 29 to May 1, 1985, on board the shuttle/Spacelab 3 platform. Continuous absorption produced primarily by the collision‐induced fundamental vibration‐rotation band of O2 and to a lesser extent by the superposition of H2O far line wings has been observed in the 1400‐ to 1800‐cm−1 interval below tangent heights of about 25 km. Continuum optical depths measured in microwindows nearly free of atmospheric line absorption are 0.78±0.06 times those calculated with the O2 absorption coefficients of Timofeyev and Tonkov (1978). This difference is consistent with previous measurements, but more than a factor of 2 improvement in accuracy has been achieved. Transmittance measurements in microwindows between 2395 and 2535 cm−1 have been used to study continuous absorption from the collision‐induced fundamental vibration‐rotation band of N2 and the far wings of strong CO2 lines (primarily those of the ν3 fundamental). Below about 2430 cm−1 there is fair agreement between the measurements and calculations based on published absorption coefficients for both N2 and CO2; at higher wave numbers, where absorption by N2 is dominant, the calculated absorption exceeds the measured absorption. The measured transmittances have been analyzed to derive best fit absorption coefficients for the N2 pressure‐induced band at lower stratospheric temperatures (∼210 K). An absorption peak has been detected near 1200 cm−1 and is believed to result from extinction by the H2SO4 stratospheric aerosol layer.

Section: Study Of the Background Levels In The Atmos Spectrasupporting

confidence: 92%

Stratospheric infrared continuum absorptions observed by the ATMOS instrument

Rinsland¹,

Zander

Namkung³

et al. 1989

“…et al, 1989]. Since N20 is mixed through showed that when the water lines were weak the corrections to the troposphere[Ablsas et al, 1987], our results, based on the P(7) line were smaller than for the P(8) line and when the column amounts, should agree with the ground level results, and water lines were strong the corrections to the P(7) line were so the disagreement is a measure of the error in our technique. Part large that the line profile might be seriously affected.…”

supporting

confidence: 70%

Spectroscopic observations of atmospheric trace gases over Kitt Peak: 2. Nitrous oxide and carbon monoxide from 1979 to 1985

Wallace¹,

Livingston²

1990

We have analyzed solar spectra obtained with the 1‐m Fourier transform spectrometer on Kitt Peak for absorption by N2O and CO. During the period 1979–1985 we find that N2O shows no detectable seasonal variation or trend and can place an upper limit on the growth rate of 1. ppb per year. This is consistent with results of ground level gas sampling. For CO we see a large seasonal variation, but because of inadequate sampling we cannot detect a trend. Combined with other Spectroscopic studies, our mean CO level suggests a northern hemisphere tropospheric scale height for CO of ∼3.5 km.

“…In some countries, the practice of imposing a lower limit on relative humidity of 20% or 35% artificially increases water vapor values. Simultaneous comparisons of balloon-borne in situ methods and remote sensing techniques in the lower stratosphere have produced differences on the order of 100% of the mean value [World Meteorological Organization (WMO), 1986; Abbas et al, 1987a, b].…”

Section: Introductionmentioning

confidence: 99%

Overview of the Stratospheric Aerosol and Gas Experiment II water vapor observations: Method, validation, and data characteristics

Rind¹,

Chiou²,

Chu³

et al. 1993

Water vapor observations obtained from the Stratospheric Aerosol and Gas Experiment II (SAGE II) solar occultation instrument for the troposphere and stratosphere are presented and compared with correlative in situ measurement techniques and other satellite data. The SAGE II instrument produces water vapor values from cloud top to approximately 1 mbar, except in regions of high aerosol content such as occurs in the low to middle stratosphere after volcanic eruptions. Details of the analysis procedure, instrumental errors, and data characteristics are discussed. Various features of the data set for the first $ years after launch (1985-1989) are identified. These include an increase in middle and upper tropospheric water vapor during northern hemisphere summer and autumn, thus at times of warmest sea surface temperature; minimum water vapor values of 2.5-3 ppmv in the tropical lower stratosphere, with lower values during northern hemisphere winter and spring; slowly increasing water vapor values with altitude in the stratosphere, reaching 5-6 ppmv or greater near the stratopause; extratropical values with minimum profile amounts occurring above the conventionally defined tropopause; and higher extratropical than tropical water vapor values throughout the stratosphere except in locations of possible polar stratospheric clouds. SAGE II data will be useful for studying individual water vapor profiles, tropospheric response to climate perturbations, troposphericstratospheric exchange (due to its inherent high vertical resolution), and stratospheric transports. It should also aid in the preparation, for the first time on a global scale, of climatologies of the stratosphere and the upper level cloud-free troposphere, for use in radiative, dynamical, and chemical studies.1.