R. W. Sanders's research while affiliated with University of Colorado Boulder and other places
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Publications (36)
Cloudy sky average photon path lengths were measured using the gamma band of oxygen near 628 nm on many days over Boulder, Colorado, using a zenith-looking spectrograph with a resolution of 0.8 nm. The approach allows accurate measurement of the average photon path length. Days characterized by relatively extensive cloud cover are examined here, wh...
For several years NO2 and OClO, two species important to understanding ozone destruction in the Antarctic stratosphere, have been measured at Arrival Heights, Antarctica by two groups: New Zealand's National Institute of Water and Atmospheric Research (NIWA) and the NOAA Aeronomy Laboratory in Boulder, Colorado. Using data independently collected b...
We present ground-based spectral measurements of downward direct and diffuse solar intensities between 624 and 686 nm. Using the rising Sun as a light source, it is shown that the water dimer does not absorb significantly in this wavelength region. Over Boulder, Colorado, on July 10, 1998, the upper limit to the dimer vertical optical depth at thes...
Direct measurements of the absorption of downwelling visible radiation by nitrogen dioxide are presented. The data show that this gas can contribute significantly to local radiative forcing under certain conditions. The observed enhancements in nitrogen dioxide absorption are likely to be due both to pollution and to production by lightning in conv...
Absorption of solar radiation by collision pairs of oxygen is a small but significant part of the total budget of incoming shortwave radiation. It is shown that the 1.26-gm band of 04 and O2oN2 is likely to contribute 0.64-1.55 W m -2 to the total atmospheric absorption for overhead Sun, clear sky conditions, bringing the total estimated absorption...
The sunrise column abundance of NO3 has been measured at Fritz Peak, Colorado (40°N, 105°W), using visible absorption spectroscopy with scattered sky light as the light source. Measurements were made in the ``off-axis'' configuration, viewing the sky near the horizon. This is a convenient alternative to direct Moon measurements, and the tropospheri...
Visible absorption spectroscopy was employed for stratospheric measurements at McMurdo Station, Antarctica, during the summer and fall seasons in 1990, 1991, 1992, and 1993. Observed column amounts of NO2 were as much as 50% smaller in 1992 and 1993 than in 1990 and 1991. The measured decreases in NO2 are believed to be due to the hydrolysis of N2O...
The column abundance of BrO has been measured at 40°N throughout the period from January 22 to May 24, 1993, providing the first remote sensing observations of this key molecule at midlatitudes. The near-ultraviolet BrO absorption bands at 349 and 355 nm have been clearly identified in the measured scattered sky spectra, with additional confirmatio...
Observations of the stratospheric NO2 column amount over the Colorado mountains during January, February, and March, 1992 are compared to concurrent lidar measurements. During this period, large aerosol amounts due to the volcanic material injected into the stratosphere by Mt. Pinatubo were observed over Colorado. The observed NO2 column displays a...
Ground-based measurements of NO3 absorption in the band near 662 nm were carried out on four occasions using the moon as a light source during sunrise at both middle and polar latitudes. As the sun rose, the observed slant column abundance of atmospheric NO3 decreased systematically. The observed time dependent decrease is due to the progression of...
Observations of Antarctic chlorine dioxide abundances in the austral
autumn and winter of 1991 (when aerosols concentrations were at
background levels) and 1992 (greatly enhanced aerosol concentrations)
are presented. It is found that in 1992, unlike 1991, chlorine dioxide
levels increased dramatically in the autumn when polar stratospheric
clouds...
The first spectroscopic measurements of chlorine dioxide throughout Antarctic fall, winter, and spring were carried out at McMurdo Station during April to October 1991. Two different observing modes were employed to extend the measurements over the broadest possible seasonal range: direct Moon measurements were used as well as observations of the s...
Lunar absorption spectra have been used to determine the vertical column abundances of NO[sub 2] and NO[sub 3] above McMurdo Station, Antarctica (77.8[degrees]S), during the fall, winter, and spring seasons in 1991. The observed nighttime NO[sub 2] and NO[sub 3] amounts during the fall and spring were broadly consistent with model predictions and w...
Observations of the ratio between the change in slant column abundance of OClO and that of ozone as a function of solar zenith are used to deduce the diurnal cycle of the daytime OClO column abundance above Antarctica during September 1987. This approach effectively normalizes other factors such as air mass factor changes and allows study of the ph...
Observations of the evening twilight BrO abundance over McMurdo Station, Antarctica during austral spring, 1987, are described. The observed variation of the slant column abundance with increasing solar zenith angles suggests that most of the BrO is located near 15 km. The total vertical column abundance observed during one week of measurements yie...
Stratospheric NOâ is expected to depend strongly upon two major factors: solar illumination and temperature. This paper presents observations in the polar regions that confirm the influence of both of these on the NOâ column abundance. Measurements of the absorption of incoming lunar radiation near 662 nm as the sun rises exhibit large changes that...
Observations of the diurnal variations of OClO and BrO during austral
spring, 1987, using long-path visible and near-ultraviolet absorption
spectroscopy are presented and compared to simplified model
calculations. It is shown that care must be taken to compare model
calculations and measurements along the line of sight of the instrument.
Evening tw...
Laboratory measurements of the near-ultraviolet spectra of O3, NO2, and OClO as a function of temperature are presented. Comparisons are made with observed features in sky spectra. The ratios between measured slant column abundances reveal that the O3 and OClO column abundances are centered in the lower stratosphere, near 20 km, while that of NO2 i...
The nitrate radical abundance is often measured by making use of its strong absorption of visible radiation in a band near 662 nm. It is shown that this NO3 absorption feature has strong negative correlation with water vapor, which requires that water vapor absorption be explicitly considered in attempts to measure NO3 from the ground. Concurrent o...
Scattered sunlight and direct light from the moon was used in two wavelength ranges to measure the total column abundances of stratospheric ozone(O(3)) and nitrogen dioxide (NO(2)) at Thule, Greenland (76.5 degrees N), during the period from 29 January to 16 February 1988. The observed O(3) column varied between about 325 and 400 Dobson units, and...
Observations at Thule, Greenland, that made use of direct light from the moon on 2,3, 4,5, and 7 February 1988 revealed nighttime
chlorine dioxide (OClO) abundances that were less than those obtained in Antarctica by about a factor of 5, but that exceeded
model predictions based on homogeneous (gas-phase) photochemistry by about a factor of 10. The...
The total column abundance of NO3 was measured in Antarctica during the nights of Sept. 17-19, 1986, by visible absorption, using the moon as the light source. The variation of the observed abundance with lunar zenith angle suggests that the bulk of the layer is located in the stratosphere. In agreement with theoretical model calculations, the tota...
The column abundance of OClO at McMurdo Station, Antarctica, was measured by visible absorption spectroscopy during austral spring in 1986. Observations were obtained during the day using scattered sunlight and at night using direct light from the moon. The observed total column amounts in Antarctica were about 20-50 times larger than would be expe...
Observations of the visible spectra of the sun and moon were obtained at McMurdo Station, Antarctica, during austral spring in 1986. The data coverage and observing conditions are described. Daily variations of ozone suggest that the bulk of the springtime ozone depletion (or the Antarctic ozone 'hole') occurs rapidly during early September. Total...
An observing program aimed at obtaining visible light spectra at McMurdo Station, Antarctica, during austral spring in 1986 is described. Total ozone abundances in late August within the polar vortex were of the order of 275 DU, suggesting that the bulk of the ozone column depletion had not yet occurred. That depletion occurred mainly during Septem...
The Infrared Radiometer experiment on the Solar Mesosphere Explorer
satellite has been continuously measuring the 6.8-micron thermal
emission from the stratospheric aerosol from the El Chichon volcano
since the time of eruption in early April, 1982. Inversion results for
the zonally-averaged infrared extinction coefficient in height,
latitude, and...
Thermal emission at 6.8 µm and particle-scattered radiation at 1.9 µm from the El Chichon aerosol cloud were measured by instruments on board the Solar Mesosphere Explorer satellite. The cloud moved westward circling the globe in twenty-one days. During its initial formation the cloud was centered at an altitude of 27 km and was confined to the lat...
The ozone content of the earth's atmosphere between 1 mb and 0.08 mb has
been measured as a function of latitude and season by an ultraviolet
spectrometer on the Solar Mesosphere Explorer spacecraft. The ozone
mixing ratio is found to be highly variable in time and space during the
winter of 1982 with maxima occurring in the winter hemisphere durin...
The temperature of the earth's atmosphere between 40 and 50 km is inferred from measurements of Rayleigh scattered sunlight by a visible-light spectrometer on the Solar Mesosphere Explorer spacecraft. The RMS deviation of the satellite measurements from conventional rocket measurements is 5°K above 45 km and 2-3°K below 45 km. The satellite data ar...
NO2 densities determined from the limb scanning visible light spectrometer on board the Solar Mesosphere Explorer spacecraft are reported for winter 1981/82 in the altitude region 28-40 km. The observational technique utilizes the photoabsorption by NO2 of Rayleigh scattered sunlight in the 440nm spectral region. The NO2 density varies from pole to...
The ozone densities between 50 and 90 km are deduced from 1.27 µm airglow measured on the Solar Mesosphere Explorer satellite. The derived densities agree well with those made simultaneously from SME by the ultraviolet spectrometer. The data set extends from pole to pole at about 3 pm, for most sunlit latitudes. At low altitudes, in the mesosphere,...
The near infrared spectrometer and the ultraviolet spectrometer on the Solar Mesosphere Explorer (SME) observed the ozone density as a function of latitude and altitude during the solar proton event of July 13, 1982. Airglow at 1.27 µm was observed at the earth's limb. The altitude profiles of the emission were inverted providing ozone densities. T...
Instruments on the Solar Mesosphere Explorer simultaneously measure
ozone density, temperature, and solar ultraviolet flux. Results from six
months of observations show that ozone density in the mesosphere changes
from day-to-day and with the seasons and that the principal cause of
these changes is the variation in atmospheric temperature. The
depe...
Beginning on October 13, 1981 a two channel spectrometer aboard the Solar Mesosphere Explorer has been obtaining daily measurements of full disc solar irradiance. These observations cover the spectral interval 120 to 305nm with approx..75nm spectral resolution. The relative accuracy of the measurements from day to day over the first three solar rot...
Citations
... The retrieval of TOC from Phaethon spectra is based on the calculation of the differential slant column density (dSCD) of ozone, i.e. the slant column that is derived when comparing the radiance of a directsun spectrum to that of a reference spectrum using the Lambert-Beer law (Kerr, 2002;Mount et al., 1987;Platt and Stutz, 2008). When a spectrum corresponding to the solar spectrum outside the Earth's atmosphere is used as reference Huber et al., 1995;Kerr, 2002;Tzortziou et al., 2012) the derived slant column represents the total slant column in the measurement path. ...
... In the lower stratosphere, the ozone decline is seen in all presented datasets for the ozone depletion phase. The ozone minimum in this region has been visible for a few years after 1991 because of the enhancement of chlorine activation after the Pinatubo eruption (Solomon et al., 1993), after which ozone starts to recover. The LSO evolution in MERRA-2 shows a decline similar to SOCOLv4, while in ERA-5, the ozone decline is much stronger than in all other datasets. ...
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... This mass is substantially higher than the initial estimate (Krueger, 1983) but in good agreement with later estimates using Version 6 of the TOMS calibration (Bluth et al., 1997;Schneider et al., 1999;Carn et al., 2003). The current estimate is consistent with estimates of the mass of sulfate aerosol produced by oxidation of the sulfur dioxide (Hoffman and Rosen, 1983;Thomas et al., 1983). ...
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... Thus, photolysis of NO 3 by moonlight is negligible. A series of moonlight NO 3 measurements have been reported (Noxon et al., 1980;Noxon, 1983;Sanders et al., 1987;Solomon et al., 1989Solomon et al., , 1993Aliwell and Jones, 1996a, b;Wagner et al., 2000). These measurements yield total column data of NO 3 , the sum of tropospheric and stratospheric partial columns. ...
... Thus, photolysis of NO 3 by moonlight is negligible. A series of moonlight NO 3 measurements have been reported (Noxon et al., 1980;Noxon, 1983;Sanders et al., 1987;Solomon et al., 1989Solomon et al., , 1993Aliwell and Jones, 1996a, b;Wagner et al., 2000). These measurements yield total column data of NO 3 , the sum of tropospheric and stratospheric partial columns. ...
... Measurements of the NO 3 absorption structure using sunlight take advantage of the fact that NO 3 is very quickly photolyzed by sunlight (around 5 s lifetime during the day) allowing for vertically resolved measurements during twilight (e.g., Aliwell and Jones, 1998;Allan et al., 2002;Coe et al., 2002;von Friedeburg et al., 2002). The fact that the NO 3 concentration is nearly zero due to rapid photolysis in the directly sunlit atmosphere, while it is largely undisturbed in a shadowed area, can be used to determine NO 3 vertical concentration profiles during sunrise using the moon as a light source (Smith and Solomon, 1990;Smith et al., 1993;Weaver et al., 1996). Alternatively, the time series of the NO 3 column density derived from scattered sunlight originating from the zenith (or from a viewing direction away from the sun) during sunrise can be evaluated to yield NO 3 vertical profiles Coe et al., 2002;von Friedeburg et al., 2002). ...
... In fact, in the NIR wavelength region, the gas absorption cross-section has strong temperature-and pressure-dependent properties and varies greatly with wavelength. This finding has been perceived and analyzed by some scientists at the 20 th century to the beginning of this century [44]- [46]. Thus, the drawback of the classical DOAS algorithm under certain conditions began to be noticed. ...
... This chlorine activation is the prerequisite for ozone destruction by catalytic cycles like the ClO-ClO and the ClO-BrO cycle (McElroy et al., 1986;Molina and Molina, 1987) after the return of sunlight in the polar spring. OClO is mostly created by the reaction between ClO and BrO (ClO + BrO → OClO + Br) (Solomon et al., 1987;Toumi, 1994;Renard et al., 1997). OClO has a very short lifetime of a few seconds in the sunlit atmosphere due to its photolysis (OClO + hν → ClO + O), which prevents the buildup of significant amounts until large solar zenith angles (SZAs) are reached. ...
... Several trace gas species were detected the first time by DOAS, e.g. OH by Perner et al. (1976), HONO by Perner and Platt (1979), NO 3 by Platt and Perner (1980), BrO by Sanders et al. (1989) and Hausmann and Platt (1994), IO by Alicke et al. (1999) and CHOCHO by Volkamer et al. (2005a). Also several other trace gases like e.g. ...
... Differential optical absorption spectroscopy (DOAS) (Platt and Stutz, 2008) is a well-established remote sensing method to retrieve trace gas abundances in the atmosphere, either from direct or scattered light observations (e.g. Perner et al., 1976;Platt and Perner, 1980;Mount et al., 1987;Wahner et al., 1990;Burrows et al., 1999;Platt and Stutz, 2008;Wagner et al., 2008). Based on Beer-Lambert law, it assumes a linear relation between the trace gas concentration (i.e. ...
