A comparison of OH nightglow volume emission rates as measured by SCIAMACHY and SABER

Abstract

Abstract. Hydroxyl (OH) short-wave infrared emissions measured by the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) were used in this study to simulate OH 1.6 μm and 2.0 μm radiances as measured by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument. This paper presents a retrieval model to perform an inversion of OH(v) number densities in order to simulate OH ro-vibrational emission radiances using a non-linear regularized global fit technique. OH 1.6 μm and 2.0 μm radiances as measured by SABER were retrieved from OH limb measurements recorded by SCIAMACHY channel 6 for altitudes in the range of 80–96 km. The main source of uncertainty in the retrieval is related to the Einstein coefficients. Systematic deviations of up to 88 % were found between SABER OH 1.6 μm and 2.0 μm radiance measurements and the corresponding simulations obtained from SCIAMACHY OH data. The radiometric calibration of the instruments could potentially explain the differences between the two measurements.

Simultaneous Retrievals of Nighttime O(3P) and Total OH Densities From Satellite Observations of Meinel Band Emissions

“…This discrepancy between SABER and SCIA data was first reported by Zhu et al. (2020). The authors used SCIA signals at OH(9‐6), OH(8‐5), OH(5‐2), and OH(4‐2) to retrieve OH(v = 4, 5, 8, and 9), then subsequently simulate SABER OH 1.6 and 2.0 μm VERs in range of 80–96 km.…”

“…Zhu et al. (2020) further reports that the signal differences can be mostly reduced by up to 50% by taking into account uncertainties in the Einstein coefficients as well as model parameter uncertainties and radiometric calibration. The bottom panels of Figure 2 already demonstrate the effects of Einstein coefficients on [OH] retrieval obtained using our technique, which utilizes SCIA VERs directly and does not involve Einstein coefficient ratios required for simulating SABER data.…”

“…This same behavior is seen for SABER-VDL (red-circle) and SCIA-VDL (blue-circles) cases suggesting that there are intrinsic discrepancies between SABER and SCIA observations as all other parameters in these retrievals are identical. This discrepancy between SABER and SCIA data was first reported by Zhu et al (2020). The authors used SCIA signals at OH(9-6), OH(8-5), OH(5-2), and OH(4-2) to retrieve OH(v = 4, 5, 8, and 9), then subsequently simulate SABER OH 1.6 and 2.0 μm VERs in range of 80-96 km.…”

“…Zhu et al. (2020) used these SCIAMACHY observations to retrieve OH( v = 4, 5, 8, 9) number densities. The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the TIMED mission measures nighttime emissions of the OH Meinel bands at 2.0 and 1.6 μm originating from ν = 8, 9 and 4, 5, respectively.…”

“…The Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument on the Envisat mission measured several OH emissions from 240 to 2,380 nm, among them 9-6, 8-5, 8-3, 5-2, 4-2, and 3-1 rotational-vibrational bands. Zhu et al (2020) used these SCIAMACHY observations to retrieve OH (v = 4, 5, 8, 9) number densities. The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the TIMED mission measures nighttime emissions of the OH Meinel bands at 2.0 and 1.6 μm originating from ν = 8, 9 and 4, 5, respectively.…”