Discovery of a New Ozone Hole over the Tropics

This paper reveals a new ozone hole that exists in the lower stratosphere over the tropics (30°N-30°S) across the seasons since the 1980s, where an ozone hole is defined as an area of ozone loss larger than 25% compared with the undisturbed atmosphere. The depth of this all-season tropical ozone hole is comparable to that of the well-known springtime ozone hole over Antarctica, while its area is about seven times that of the latter. At the center of the deepest tropical or Antarctic ozone hole, approximately 80% of the normal ozone value is depleted, whereas annual mean ozone depletion in the lower stratosphere over the tropics due to the coldest temperature is about 1.6 times that over Antarctica and is about 7.7 times that over the Arctic. The whole-year ozone hole over the tropics could cause a serious global concern as it can lead to increases in ground-level ultraviolet radiation and affect 50% of Earth's surface area, which is home to approximately 50% of the world's population. Moreover, since ozone loss is well-known to lead to stratospheric cooling, the presence of the all-season tropical ozone hole and the seasonal polar ozone holes is equivalent to the formation of three ‘temperature holes’ in the global lower stratosphere. These findings will play a far-reaching role in understanding fundamental atmospheric processes and global climate change.

Non-uniform dissipation of the Antarctic ozone hole

The evolution o f the Antarct ic ozone hole is illustrated fo r 1985·1989 and 1990 springs.A detailed study for 1986.19 89 and 1990 events indicates that the evolution. which occurs in ea rly October . isfairly unifo rm over the South Pole. Hence the fluctuations observed at Syowa, McMurdo and Palmer duringthis period arc mostly due to the vortex \''3.11 passing in and out over these periferial loca t ions. However, later inNovember when the hole is dissipating, the vortex may shift from the South Pole in any direction and may alsocome back or intensify on Sou th Pole before finally disappearing. At South Pole. the recovery started by Octoberend in 19S5. 19R6 and 1988 but later in 19R7 (November end), 1989 {November beginning) and 1990 (Novemberend •.

Twisting turning and pulsating of the Antarctic ozone hole, as revealed by TOMS data

Using data from TOMS!Nimbus7 and Meteor 3, the evolution of Antarctic ozone holes during the southern springs of 1992, 1993, 1994 was studied. At the South Pole, the evolution was mostly smooth, a steady decrease up to about September end and a steady recovery up to about December end. At latitudes near 65° S, the ozone levels (~220 DU) at different latitudes and longitudes showed fluctuations compatible with passing of a noncircular (oval) ! vortex boundary (two ends of a major axis of an ellipse), with a rotation period of -15 days (full rotation period ~30 days) in 1992 and ~17 days (full rotation period ~34 days) in 1994, different from the 2-3 weeks reported by earlier workers. However, the rotation was not with uniform speeds. During a full rotation, the speeds varied sometimes from almost zero (stalling) for a few days to ~20° per day during other intervals. Outside the oval boundary, often there were, depletions with spacings of a few (5-8) days, extending to lower latitudes up to ~30° S, indicating corrugations in the oval boundary, probably due to the effects of synoptic disturbances on total ozone through tropopause pressure changes and/or I ozone mini- holes caused by anticyclonic tropospheric forcing under the southern polar vortex. The shape of the ozone hole changed from elliptic to almost circular and vice versa within a few days and the area also changed by ~15-20%. Thus, the ozone hole was twisting, turning and pulsating, probably due to a varying strength of the wave number 2 component of the wind system prevailing there.

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.

The art of modelling climate change in time slice integrations: The ICON-ART experience

<p>Climate change is happening in a transient manner – with continuously increasing greenhouse gases in the atmosphere, humans have started a radiative imbalance that leads to rising near-surface temperatures. However, there are good reasons why it makes sense to look at quasi-equilibrium climate change simulations. In such simulations, we approximate climate change by “fixing” the amount of long-lived greenhouse gases and use recurring boundary conditions that are representative of a particular year - past, present or future. With such a setup any climate model should simulate a stable climate (after a spin-up phase) that reveals internal variability and does not show any trends. It is a necessary condition for the validity of the model - if no transience is provided in the boundary conditions – that the model does not drift. With such a model configuration, it is possible to estimate probability density functions, because each year of a multi-annual integration is an equally valid realisation for the meteorology of the pre-selected year.</p> <p>Using such a time-slice approach, sensitivities to well-specified individual changes can be assessed. Here, we provide a range of examples using the ICON-ART modelling system to investigate (idealised) climate change scenarios with respect to different threshold temperatures, jet variability and the climatic impact of the ozone hole. We illustrate how such integrations allow the unambiguous attribution of certain climate change effects, e.g. the change of jet stream variability under global warming or the contribution of the ozone hole to regional surface warming. However, we caution against a strict causality chain of processes in explaining the response, because given the nature of the quasi-equilibrium modelled, consistency might not always imply causality.</p>

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>

Study of SO2 and NO2 behaviour during the ozone-hole event at Antarctica by Brewer Spectrophotometer

Vertical column density of sulphur dioxide has been measured at Maitri (70.7°S, 11.7°E), the Indian station in the Antarctica from September, 1999 to December, 2006 by a Brewer Spectrophotometer. Simultaneously, nitrogen dioxide, ozone and the maximum value of UV-B have also been measured, we found an increase in SO2 during spring. An increase in NO2 column was also found during this period but not identical with that of SO2. These variations in SO2 and NO2 are not in phase with the increase in UV-B flux at the ground due to the decrease of ozone column in the stratosphere. The variation of SO2 column is explained by the downward shift of penetration depth of UV-B radiation during the ozone-hole event.

Ozone hole over poles : Current status

The ozone in the stratosphere is of great importance for very survival of life on the mother planet the Earth. Ozone acts as an umbrella and protects us from the harmful ultraviolet radiations coming from the Sun. The catalytic destruction of ozone by ClOx & NOx in general and ozone hole phenomenon over Antarctica during spring time in particular has generated unprecedented interest in monitoring of ozone and other trace constituents in the atmosphere. The satellites have proved to be an important tool to monitor the global ozone column on regular basis. The ozone data using various satellite platforms has been analyzed for the ozone hole studies over north and south poles. Also Ozone measurements were carried out at Maitri, Antarctica. The satellite data indicates that some recovery of ozone hole as a result of international efforts in reduction of use of CFCs which are the main culprit for ozone hole. However, it will be too early to conclude about ozone hole recovery. In the present communication current status of ozone hole will be discussed in detail.