Comparison of aerosol extinction between lidar and SAGE II over Gadanki, a tropical station in India

Kulkarni, Padmavati; Ramachandran, S.

doi:10.5194/angeo-33-351-2015

Cited by 5 publications

(3 citation statements)

References 36 publications

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“…Nighttime extinction (Vanhellemont et al, 2010;Sofieva et al, 2013;Robert et al, 2016;Vanhellemont et al, 2016); sensitivity depends on altitude (numbers derived from Fig. 2 in Vanhellemont et al, 2016); the target of the aerosol retrieval is 4 km vertical resolution (Bertaux et al, 2010;Kyrölä et al, 2010); lowest tangent altitude 8-18 km high latitudes and tropics, respectively (Tamminen et al, 2010)…”

Section: Gomos Nmmentioning

confidence: 99%

Aerosol and cloud top height information of Envisat MIPAS measurements

et al. 2020

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Abstract. Infrared limb emission instruments have a long history in measuring clouds and aerosol. In particular, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument aboard ESA's Envisat provides 10 years of altitude-resolved global measurements. Previous studies found systematic overestimations and underestimations of cloud top heights for cirrus and polar stratospheric clouds. To assess the cloud top height information and to characterise its uncertainty for the MIPAS instrument we performed simulations for ice clouds, volcanic ash, and sulfate aerosol. From the simulation results we found that in addition to the known effects of the field-of-view that can lead to a cloud top height overestimation, and broken cloud conditions that can lead to underestimation, the cloud extinction also plays an important role. While for optically thick clouds the possible cloud top height overestimation for MIPAS reaches up to 1.6 km due to the field-of-view, for optically thin clouds and aerosol the systematic underestimation reaches 5.1 km. For the detection sensitivity and the degree of underestimation of the MIPAS measurements, the cloud layer thickness also plays a role; 1 km thick clouds are detectable down to extinctions of 5×10-4 km−1 and 6 km thick clouds are detectable down to extinctions of 1×10-4 km−1, where the largest underestimations of the cloud top height occur for the optically thinnest clouds with a vertical extent of 6 km. The relation between extinction coefficient, cloud top height estimate, and layer thickness is confirmed by a comparison of MIPAS cloud top heights of the volcanic sulfate aerosol from the Nabro eruption in 2011 with space- and ground-based lidar measurements and twilight measurements between June 2011 and February 2012. For plumes up to 2 months old, where the extinction was between 1×10-4 and 7×10-4 km−1 and the layer thickness mostly below 4 km, we found for MIPAS an average underestimation of 1.1 km. In the aged plume with extinctions down to 5×10-5 km−1 and layer thicknesses of up to 9.5 km, the underestimation was higher, reaching up to 7.2 km. The dependency of the cloud top height overestimations or underestimations on the extinction coefficient can explain seemingly contradictory results of previous studies. In spite of the relatively large uncertainty range of the cloud top height, the comparison of the detection sensitivity towards sulfate aerosol between MIPAS and a suite of widely used UV/VIS limb and IR nadir satellite aerosol measurements shows that MIPAS provides complementary information in terms of detection sensitivity.

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Section: Gomos Nmmentioning

confidence: 99%

Aerosol and cloud top height information of Envisat MIPAS measurements

et al. 2020

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“…Aerosols over the Tibetan Plateau (TP) and the Asian summer monsoon region are especially important. The TP is surrounded by countries with large anthropogenic emissions (Li et al, 2005;Lau et al, 2006). Aerosols from India, Southeast Asia, and southern China can be transported to the TP by prevailing winds in the pre-monsoon and monsoon seasons (Lawrence and Lelieveld, 2010;Xia et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Summertime nitrate aerosol in the upper troposphere and lower stratosphere over the Tibetan Plateau and the South Asian summer monsoon region

Liao

Bian

2016

Atmos. Chem. Phys.

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Abstract. We use the global three-dimensional Goddard Earth Observing System chemical transport model (GEOS-Chem) to examine the contribution of nitrate aerosol to aerosol concentrations in the upper troposphere and lower stratosphere (UTLS) over the Tibetan Plateau and the South Asian summer monsoon (TP/SASM) region during summertime of year 2005. Simulated surface-layer aerosol concentrations are compared with ground-based observations, and simulated aerosols in the UTLS are evaluated by using the Stratospheric Aerosol and Gas Experiment II satellite data. Simulations show elevated aerosol concentrations of sulfate, nitrate, ammonium, black carbon, organic carbon, and PM2.5 (particles with diameter equal to or less than 2.5 µm, defined as the sum of sulfate, nitrate, ammonium, black carbon, and organic carbon aerosols in this study) in the UTLS over the TP/SASM region throughout the summer. Nitrate aerosol is simulated to be of secondary importance near the surface but the most dominant aerosol species in the UTLS over the studied region. Averaged over summertime and over the TP/SASM region, CNIT (the ratio of nitrate concentration to PM2.5 concentration) values are 5–35 % at the surface, 25–50 % at 200 hPa, and could exceed 60 % at 100 hPa. The mechanisms for the accumulation of nitrate in the UTLS over the TP/SASM region include vertical transport and the gas-to-aerosol conversion of HNO3 to form nitrate. The high relative humidity and low temperature associated with the deep convection over the TP/SASM region are favorable for the gas-to-aerosol conversion of HNO3.

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“…For the comparison of the ground-based lidar measurements with the MIPAS profiles we used a match radius of 500 km, as for CALIOP, but a larger match time of the lidar measurement period ±24 h as in several studies comparing SAGE II and ground based lidar aerosol measurements (e.g. Antuña et al, 2002;Kulkarni and Ramachandran, 2015). In total we found MIPAS aerosol measurements matching to 32 lidar profiles that were measured on 26 different days between 18 July 2011 and 02 February 2012 (e.g.…”

Section: Leipzig Lidar Measurementsmentioning

confidence: 99%

Aerosol and cloud top height information of Envisat MIPAS measurements

Grießbach¹,

Hoffmann²,

Spang³

et al. 2019

Preprint

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Abstract. Infrared limb emission instruments have a long history in measuring clouds and aerosol. In particular the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument aboard ESA's Envisat provides 10 years of altitude resolved global measurements. Previous studies found systematic over- and underestimations of cloud top heights for cirrus and polar stratospheric clouds. To assess the cloud top height information and to characterize its uncertainty for the MIPAS instrument we performed simulations for ice clouds, volcanic ash, and sulfate aerosol. From the simulation results we found that in addition to the known effects of the field-of-view that can lead to a cloud top height overestimation, and broken cloud conditions that can lead to underestimation, also the cloud extinction plays an important role. While for optically thick clouds the possible cloud top height overestimation for MIPAS reaches up to 1.6 km due to the field-of-view, for optically thin clouds and aerosol the systematic underestimation reaches 5.1 km. For the detection sensitivity and the degree of underestimation of the MIPAS measurements also the cloud layer thickness plays a role. 1 km thick clouds are detectable down to extinctions of 5 x 10-4 km-1 and 6 km thick clouds are detectable down to extinctions of 1 x 10-4 km-1, where the largest underestimations of the cloud top height occur for the optically thinnest clouds with a vertical extent of 6 km. The relation between extinction coefficient, cloud top height estimate, and layer thickness is confirmed by a comparison of MIPAS cloud top heights of the volcanic sulfate aerosol from the Nabro eruption in 2011 with space- and ground-based lidar measurements and twilight measurements between June 2011 and February 2012. In the fresh to two months old plume, where the extinction was between 1 x 10-4 and 7 x 10-4 km-1 and the layer thickness mostly below 4 km, we found for MIPAS an average underestimation of 1.1 km. In the aged plume with extinctions down to 5 x 10-5 km-1 and layer thicknesses of up to 9.5 km the underestimation was higher reaching 7.2 km. The dependency of the cloud top height over- or underestimation on the extinction coefficient can explain seemingly contradictory results of previous studies. In spite of the relatively large uncertainty range of the cloud top height, the comparison of the detection sensitivity towards sulfate aerosol between MIPAS and a suite of widely used UV/VIS limb and IR nadir satellite aerosol measurements shows that MIPAS provides complementary information in terms of detection sensitivity.

show abstract

Comparison of aerosol extinction between lidar and SAGE II over Gadanki, a tropical station in India

Cited by 5 publications

References 36 publications

Aerosol and cloud top height information of Envisat MIPAS measurements

Aerosol and cloud top height information of Envisat MIPAS measurements

Summertime nitrate aerosol in the upper troposphere and lower stratosphere over the Tibetan Plateau and the South Asian summer monsoon region

Aerosol and cloud top height information of Envisat MIPAS measurements

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