Impact of Using a New High-Resolution Solar Reference Spectrum on OMI Ozone Profile Retrievals

We evaluated a new high-resolution solar reference spectrum for characterizing space-borne Ozone Monitoring Instrument (OMI) measurements as well as for retrieving ozone profile retrievals over the ultraviolet (UV) wavelength range from 270 to 330 nm. The SAO2010 solar reference has been a standard for use in atmospheric trace gas retrievals, which is a composite of ground-based and balloon-based solar measurements from the Kitt Peak National Observatory (KPNO) and Air Force Geophysics Laboratory (AFGL), respectively. The new reference spectrum, called the TSIS-1 Hybrid Solar Reference Spectrum (HSRS), spans 202–2730 nm at a 0.01 to ~0.001 nm spectral resolution. The TSIS-1 HSRS in the UV region of interest in this study is a composite of AFGL and ground-based solar measurements from the Quality Assurance of Spectral Ultraviolet Measurements In Europe (QASUME) campaign, with a radiometric calibration that used the lower resolution Spectral Irradiance Monitor (SIM) instrument on the space-based Total and Spectral Solar Irradiance Sensor-1 (TSIS-1) mission. The TSIS-1 HSRS radiometric uncertainties were below 1% whereas those of SAO2010 ranged from 5% in the longer UV part to 15% in the shorter UV part. In deriving slit functions and wavelength shifts from OMI solar irradiances, the resulting fitting residuals showed significant improvements of 0.5–0.7% (relatively, 20–50%) due to switching from the SAO2010 to the TSIS-1 HSRS. Correspondingly, in performing ozone profile retrievals from OMI radiances, the fitting residuals showed relative improvements of up to ~5% in 312–330 nm with relative differences of 5–7% in the tropospheric layer column ozone; the impact on stratospheric ozone retrievals was negligible.

Temperatures of Anvil Clouds and Radiative Tropopause in a Wide Array of Cloud-Resolving Simulations

We present ninety-nine cloud-resolving simulations to study how temperatures of anvil clouds and radiative tropopause change with surface warming. Our simulation results show that the radiative tropopause warms at approximately the same rate as anvil clouds. This relationship persists across a variety of modeling choices, including surface temperature, greenhouse gas concentration, and the representation of radiative transfer. We further show that the shifting ozone profile associated with climate warming may give rise to a fixed tropopause temperature as well as a fixed anvil temperature. This result points to the importance of faithful treatment of ozone in simulating clouds and climate change; the robust anvil-tropopause relationship may also provide alternative ways to understand what controls anvil temperature.

Compilation of ozonesonde observation over Schirmacher oasis east Antarctic from 1999-2007

Hkkjr ekSle foKku foHkkx }kjk Hkkjrh; bysDVªks&dsfedy vkstksulkSans dh enn ls ,aVkdZfVdk ij Hkkjr ds nwljs LVs'ku eS=h ¼70-7 fMxzh n-] 11-7 fMxzh iw-½ ls vkstksu fLFkfr ¼izksQkby½ dk fu;fer eki fd;k tk jgk gSA ok;qeaMy ds mnxz LraHk esa vkstksu ds ?kuRo dh x.kuk iwjs o"kZ esa fy, x, lkIrkfgd vkstksu lkmfUMax ls dh tkrh gSA ok;qeaMyh; vkstksu dh mnxz fLFkfr ¼izksQkby vkSj vkstksu fNnz ¼gksy½ dh fo'ks"krkvksa dk v/;;u djus ds fy, flracj&vDVwcj ekg ds nkSjku cgqr ckj ifjKfIr;k¡ ¼lkmfUMax½ yh xbZ gSaA bl 'kks/k i= esa lrg ls 10 gsDVk ik- ds chp vkstksu vkSj rkieku ds ekfld ,oa okf"kZd vkSlr esa fofo/krk dh x.kuk ,oa fo'ys"k.k o"kZ 1999 ls 2007 dh vof/k esa fy, vkstksulkSans vkjksg.kksa ls fd;k x;k gSA bl v/;;u ls irk pyk gS fd vkstksu fNnz ds laca/k esa xgu vo{k; vDrwcj esa vkSj vYi ijUrq egRoiw.kZ vo{k; flracj ekg esa gqvk gSA vDrwcj esa yxHkx 250 ,oa 20 gs-ik- ds chp lcls lqLi"V vo{k; gqvk gS ftlesa vf/kdre LFkkuh; vkstksu ds Lrj esa 70 gs-ik- vkSj 10 gs- ik- ds Lrjksa ij vkSj flrEcj esa 70 gs- ik- ij fxjkoV ns[kh xbZA fHkUu&fHkUu nkc Lrjksa ds fy, vkstksu dk rkieku ds lkFk lglaca/k ls ubZ tkudkfj;ksa vkSj vkstksu ifjorZu esa foLrkj dk irk pyk gSA iwjs o"kZ esa 300 ls 50 gs- ik- ds chp U;wure okf"kZd vkSlr rkieku -55 fMxzh ls -63 fMxzh lsaVhxzsM rd cnyrk gSA vxLr vkSj flrEcj ds eghuksa esa 70 gs- ik- rFkk 100 gs- ik- Lrjksa ij rkieku dk -80 fMxzh lsaVhxzsM ls de gksuk ,oa vDrwcj ekg esa 70 gs- ik- rFkk 100 gs- ik- Lrjksa ij yxHkx -70 fMxzh lsaVhxzsM ls de gksus dh fLFkfr dks vDrwcj ekg esa vkst+ksu vo{k; ds ladsrd ds :i esa ekuk tk ldrk gSA Regular ozone profile measurement over Antarctica has been made by India Meteorological Department over Indian second station Maitri (70.7° S, 11.7° E) with the help of Indian electro-chemical ozonesonde. Ozone density in the vertical column of the atmosphere is computed with weekly ozone soundings taken throughout the year. During the month of September- October more frequent soundings were taken to study vertical profile of atmospheric ozone and features of ozone hole. The mean monthly and yearly variation of ozone and temperature from surface to 10 hPa has been computed and analyzed from the ozonesonde ascents for the period 1999 to 2007. The study has shown profound depletion in October and lesser but substantial depletion in September, in association with the ozone hole. Depletion is most pronounced between about 250 and 20 hPa in October, with maximum local ozone losses near 70 hPa & 100 hPa levels and in September at 70 hPa. Ozone correlations with temperature for several pressure levels have revealed new insights into the causes and extent of ozone change. Lowest annual mean temperature varies from -55 to -63 °C between 300 to 50 hPa in all the year. The temperature less than -80 °C in months of August & September at 70 hPa & 100 hPa levels and about -70 °C in month of October at 70 hPa & 100 hPa levels can be attributed as an indicator of ozone depletion in months of October

Measurement of Ozone at Maitri, Antarctica

Regular ozone profile measurement over Antarctica has been made by India Meteorological Department since 1987 at Dakshin Gangotri and later at Maitri (70.7°S, 11.7°E) since 1990 with the help of Indian electro-chemical ozone sonde. Surface ozone measurement was also started at Dakshin Gangotri since 1989 and later at Maitri. Ozone sonde data at Dakshin Gangotri and Maitri have been analysed and ozone hole structure has been studied in detail. The drastic decrease in ozone amount is clearly seen between 100 hPa to 30 hPa layer reaching near zero value. Incidently this is the layer where highest ozone concentration occurs during other months except September-October. The ozone hole has been quite severe during 1994-95 with increase in area and depth. During 1996 the Antarctic ozone hole was also similar to previous years. An interesting feature of the 1995 event was the persistence of ozone hole through November & December. Stratospheric temperature changes during 1995 also support that the cold core vortex during 1995 was very cold and persisted up to November.

Record-breaking stratospheric smoke and record-breaking ozone depletion events in the Arctic and in Antarctica in 2020! Any link between smoke occurrence and ozone depletion?

<p>The highlight of our multiwavelength polarization Raman lidar measurements during the 1-year MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition in the Arctic Ocean ice from October 2019 to May 2020 was the detection of a persistent, 10 km deep aerosol layer in the upper troposphere and lower stratosphere (UTLS) with clear and unambiguous wild-fire smoke signatures. The smoke is supposed to originate from extraordinarily intense and long-lasting wildfires in central and eastern Siberia in July and August 2019 and may have reached the tropopause layer by the self-lifting process.</p><p>Temporally almost parallelly, record-breaking wildfires accompanied by unprecedentedly strong pyroconvection were raging in the south-eastern part of Australia in late December 2019 and early January 2020. These fires injected huge amounts of biomass-burning smoke into the stratosphere where the smoke particles became distributed over the entire southern hemispheric in the UTLS regime from 10-30 km to even 35 km height. The stratospheric smoke layer was monitored with our Raman lidar in Punta Arenas (53.2°S, 70.9°W, Chile, southern South America) for two years.</p><p>The fact that these two events in both hemispheres coincided with record-breaking ozone hole events in both hemispheres in the respective spring seasons motivated us to discuss a potential impact of the smoke particles on the strong ozone depletion. The discussion is based on the overlapping height ranges of the smoke particles, polar stratospheric clouds, and the ozone hole regions. It is well known that strong ozone reduction is linked to the development of a strong and long-lasting polar vortex, which favours increased PSC formation. In these clouds, active chlorine components are produced via heterogeneous chemical processes on the surface of the PSC particles. Finally, the chlorine species destroy ozone molecules in the spring season. However, there are two pathways to influence ozone depletion by aerosol pollution. The particles can influence the evolution of PSCs and specifically their microphysical properties (number concentration and size distribution), and on the other hand, the particles can be directly involved in heterogeneous chemical processes by increasing the particle surface area available to convert nonreactive chlorine components into reactive forms. A third (indirect) impact of smoke, when well distributed over large parts of the Northern or Southern hemispheres, is via the influence on large-scale atmospheric dynamics.</p><p>We will show our long-term smoke lidar observations in the central Arctic and in Punta Arenas as well as ozone profile measurements during the ozone-depletion seasons. Based on these aerosol and ozone profile data we will discuss the potential interaction between smoke and ozone.</p>

Combined UV and IR ozone profile retrieval from TROPOMI and CrIS measurements

Vertical ozone profiles from combined spectral measurements in the ultraviolet and infrared spectral range were retrieved by using data from TROPOMI/S5P and CrIS/Suomi-NPP, which are flying in loose formation three minutes apart in the same orbit. A previous study of ozone profiles retrieved exclusively from TROPOMI UV spectra showed that the vertical resolution in the troposphere is clearly limited (Mettig et al, 2021). The vertical resolution and the vertical extent of the ozone profiles is improved by combining both wavelength ranges compared to retrievals limited to UV or IR spectral data only. The combined retrieval particularly improves the accuracy of the retrieved tropospheric ozone and to a lesser degree stratospheric ozone up to 30 km. An increase in the degree-of-freedom by one was found in the UV+IR retrieval compared to the UV-only retrieval. Compared to previous publications, which investigated combinations of UV and IR observations from the pairs OMI/TES and GOME-2/IASI, the degree of freedom is lower, which is attributed to the reduced spectral resolution of CrIS compared to TES or IASI. Tropospheric lidar and ozonesondes were used to validate the ozone profiles and tropospheric ozone column (TOC). From the comparison with tropospheric lidars both ozone profiles and TOCs show smaller biases for the retrieved data from the combined UV+IR observation than the UV observations alone. While the TOCs show good agreement, the profiles have a positive bias of more than 20 % between 10 and 15 km. The reason is probably a positive stratospheric bias from the IR retrieval. The comparison of the UV+IR and UV ozone profiles up to 30 km with MLS (Microwave Limb Sounder) demonstrates the improvement of the UV+IR profile in the stratosphere.

ML-TOMCAT: machine-learning-based satellite-corrected global stratospheric ozone profile data set from a chemical transport model

High-quality stratospheric ozone profile data sets are a key requirement for accurate quantification and attribution of long-term ozone changes. Satellite instruments provide stratospheric ozone profile measurements over typical mission durations of 5–15 years. Various methodologies have then been applied to merge and homogenise the different satellite data in order to create long-term observation-based ozone profile data sets with minimal data gaps. However, individual satellite instruments use different measurement methods, sampling patterns and retrieval algorithms which complicate the merging of these different data sets. In contrast, atmospheric chemical models can produce chemically consistent long-term ozone simulations based on specified changes in external forcings, but they are subject to the deficiencies associated with incomplete understanding of complex atmospheric processes and uncertain photochemical parameters. Here, we use chemically self-consistent output from the TOMCAT 3-D chemical transport model (CTM) and a random-forest (RF) ensemble learning method to create a merged 42-year (1979–2020) stratospheric ozone profile data set (ML-TOMCAT V1.0). The underlying CTM simulation was forced by meteorological reanalyses, specified trends in long-lived source gases, solar flux and aerosol variations. The RF is trained using the Stratospheric Water and OzOne Satellite Homogenized (SWOOSH) data set over the time periods of the Microwave Limb Sounder (MLS) from the Upper Atmosphere Research Satellite (UARS) (1991–1998) and Aura (2005–2016) missions. We find that ML-TOMCAT shows excellent agreement with available independent satellite-based data sets which use pressure as a vertical coordinate (e.g. GOZCARDS, SWOOSH for non-MLS periods) but weaker agreement with the data sets which are altitude-based (e.g. SAGE-CCI-OMPS, SCIAMACHY-OMPS). We find that at almost all stratospheric levels ML-TOMCAT ozone concentrations are well within uncertainties of the observational data sets. The ML-TOMCAT (V1.0) data set is ideally suited for the evaluation of chemical model ozone profiles from the tropopause to 0.1 hPa and is freely available via https://doi.org/10.5281/zenodo.5651194 (Dhomse et al., 2021).

Evaluating the Performance of Ozone Products Derived from CrIS/NOAA20, AIRS/Aqua and ERA5 Reanalysis in the Polar Regions in 2020 Using Ground-Based Observations

Quantifying spatiotemporal polar ozone changes can promote our understanding of global stratospheric ozone depletion, polar ozone-related chemical processes, and atmospheric dynamics. By means of ground-level measurements, satellite observations, and re-analyzed meteorology, the global spatial and temporal distribution characteristics of the total column ozone (TCO) and ozone profile can be quantitatively described. In this study, we evaluated the ozone datasets from CrIS/NOAA20, AIRS/Aqua, and ERA5/ECWMF for their performance in polar regions in 2020, along with the in situ observations of the Dobson, Brewer, and ozonesonde instruments, which are regarded as benchmarks. The results showed that the ERA5 reanalysis ozone field had good consistency with the ground observations (R > 0.95) and indicated whether the TCO or ozone profile was less affected by the site location. In contrast, both CrIS and AIRS could capture the ozone loss process resulting from the Antarctic/Arctic ozone hole at a monthly scale, but their ability to characterize the Arctic ozone hole was weaker than in the Antarctic. Specifically, the TCO values derived from AIRS were apparently higher in March 2020 than those of ERA5, which made it difficult to assess the area and depth of the ozone hole during this period. Moreover, the pattern of CrIS TCO was abnormal and tended to deviate from the pattern that characterized ERA5 and AIRS at the Alert site during the Arctic ozone loss process in 2020, which demonstrates that CrIS ozone products have limited applicability at this ground site. Furthermore, the validation of the ozone profile shows that AIRS and CrIS do not have good vertical representation in the polar regions and are not able to characterize the location and depth of ozone depletion. Overall, the results reveal the shortcomings of the ozone profiles derived from AIRS and CrIS observations and the reliability of the ERA5 reanalysis ozone field in polar applications. A more suitable prior method and detection sensitivity improvement on CrIS and AIRS ozone products would improve their reliability and applicability in polar regions.

A global ozone profile climatology for satellite retrieval algorithms based on Aura MLS measurements and the MERRA-2 GMI simulation

A new atmospheric ozone profile climatology has been constructed by combining daytime ozone profiles from the Aura Microwave Limb Sounder (MLS) and Modern-Era Retrospective Analysis for Research Applications version 2 (MERRA-2) Global Modeling Initiative (GMI) model simulation (M2GMI). The MLS and M2GMI ozone profiles are merged between 13 and 17 km (∼159 and 88 hPa), with MLS used for stratospheric and GMI for primarily tropospheric levels. The time record for profiles from MLS and GMI is August 2004–December 2016. The derived seasonal climatology consists of monthly zonal-mean ozone profiles in 5∘ latitude bands from 90∘ S to 90∘ N covering altitudes (in Z* log-pressure altitude) from zero to 80 km in 1 km increments. This climatology can be used as a priori information in satellite ozone retrievals, in atmospheric radiative transfer studies, and as a baseline to compare with other measured or model-simulated ozone. The MLS/GMI seasonal climatology shows a number of improvements compared with previous ozone profile climatologies based on MLS and ozonesonde measurements. These improvements are attributed mostly to continuous daily global coverage of GMI tropospheric ozone compared with sparse regional measurements from sondes. In addition to the seasonal climatology, we also derive an additive climatology to account for interannual variability in stratospheric zonal-mean ozone profiles which is based on a rotated empirical orthogonal function (REOF) analysis of Aura MLS ozone profiles. This REOF climatology starts in 1970 and captures most of the interannual variability in global stratospheric ozone including quasi-biennial oscillation (QBO) signatures.