No abstract

A recent study by Younas et al. (2020, https://doi.org/10.1029/2020ja027981, referred to hereafter as Y20) has shown incorrect results of the variations in the level‐3 data of [O/N2] ratio obtained from global ultra violet imager on board TIMED satellite. Y20 have shown the variations in [O/N2] ratio during 25–28 August 2018 but they have wrongly mapped the corresponding longitudes of the orbits in east‐west direction. So, the decrements and enhancements in the [O/N2] ratio are misinterpreted by Y20 in combination with their results on TEC (total electron content). Also, they have derived hemispheric asymmetry in [O/N2] ratio, the variations of which are not reproducible in similar shape from the same data set and method. The results of Y20 on wrong mapping of [O/N2] ratio are further repeated by Bolaji et al. (2021, https://doi.org/10.1029/2020ja029068). We provide a correct method, validate it and call for the needful corrections in both the papers.

Abstract. Contrail backscatter and polarization measurements made using a 532-1064 nm LIDAR in Florence (Italy) indicated that, in most of the cases, the contrail depolarisation and color ratio resemble the usual cirrus. In 20% of the cases, a depolarisation below 15% was observed, both in isolated contrails and in cirrus-embedded contrails. In a few cases, a very low depolarisation, down to 3%, was observed at temperatures in the -40 ø to-65 ø C range. In two measurements, a low depolarization was coupled with a high color ratio in the 2-4 range. The low-depolarisation, high color ratio contrail observations are discussed in the light of the results of recent Tmatrix scattering simulations. The two events lasted at least 10-20 minutes in the LIDAR data, suggesting a very slow growth or no growth at all of the initial micron-sized contrail particles in the large ice crystals typical of cirrus.

Abstract.A rare occurrence of stratospheric cirrus at 18.6 km height persisting for about 5 days during 3-7 March 2014 is inferred from the ground-based Mie lidar observations over Gadanki (13.5 • N, 79.2 • E) and spaceborne observations. Due to the vertical transport by large updrafts on 3 March in the troposphere, triggered by a potential vorticity intrusion, the water vapour mixing ratio shows an increase around the height of 18.6 km. Relative humidity with respect to ice is ∼ 150 %, indicating that the cirrus cloud may be formed though homogeneous nucleation of sulfuric acid. The cirrus cloud persists due to the cold anomaly associated with the presence of a 4-day wave.

Solar ultraviolet flux measurements in the biological band at 290-320 nm have indicated a sharp increase in the ground reaching solar ultravio let total flux during the recovery phase of the 24 October 1995 solar eclipse event. The flux values came back to their normal control day value within about two hours after the total recovery phase of the eclipse. The solar flux changes at the visible and near infrared wavelengths did not show any such increase in flux except at 600 nm, which is in the Chappius band for ozone absorption. The observed changes indicate that the increase in the flux could be due to a decrease in the atmospheric columnar ozone. From a numerical calculation it is inf erred that a 4.6 % decrease in ozone could produce the observed UV flux increase.