On the linkage between the Asian summer monsoon and tropopause fold activity over the eastern Mediterranean and the Middle East

Tyrlis, Evangelos; Škerlak, Bojan; Sprenger, Michael; Wernli, Heini; Zittis, George; Lelieveld, Jos

doi:10.1002/2013jd021113

Cited by 76 publications

(87 citation statements)

References 75 publications

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“…STT events associated with cut-off low-pressure systems are more prevalent during summer, while STT events associated with frontal passage occur throughout the year. The high frequency of STT ozone enhancements is comparable to the > 25 % frequencies seen over Turkey and east of the Caspian sea in an ERA-I analysis performed by Tyrlis et al (2014). The SH summer maximum we see for STT ozone flux can also be seen in Fig.…”

Section: Stt Event Climatologiessupporting

confidence: 78%

“…Another commonly used tropopause definition is determined with the use of PV (dynamical tropopause). In the extratropics the isosurface where PV = 2 PVU (1 PVU= 10 −6 m 2 s −1 K kg −1 ) is often used to define the tropopause, allowing the 3-D representation of tropopause folds and other tropopause features in a sufficiently resolved model Tyrlis et al, 2014). The PV is not calculable using the ozonesonde measurements alone, so in this work the ozone tropopause is used when determining STT events or measured tropopause altitude.…”

Section: Ozonesonde Record In the Southern Oceanmentioning

confidence: 99%

“…The stratospheric polar vortex may create tropopause folds without other sources of upper-tropospheric turbulence such as low-pressure fronts or cyclones (e.g. Baray et al, 2000;Sprenger et al, 2003;Tyrlis et al, 2014). Cut-off low-pressure systems can be seen clearly in synoptic-scale weather maps as regions with lowered pressure and cyclonic winds.…”

Section: Classifying Synoptic Conditions During Stt Eventsmentioning

confidence: 99%

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Stratospheric ozone intrusion events and their impacts on tropospheric ozone in the Southern Hemisphere

et al. 2017

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Abstract. Stratosphere-to-troposphere transport (STT) provides an important natural source of ozone to the upper troposphere, but the characteristics of STT events in the Southern Hemisphere extratropics and their contribution to the regional tropospheric ozone budget remain poorly constrained. Here, we develop a quantitative method to identify STT events from ozonesonde profiles. Using this method we estimate the seasonality of STT events and quantify the ozone transported across the tropopause over Davis (69 • S, 2006Davis (69 • S, -2013, Macquarie Island (54 • S, 2004-2013), and Melbourne (38 • S, 2004-2013). STT seasonality is determined by two distinct methods: a Fourier bandpass filter of the vertical ozone profile and an analysis of the Brunt-Väisälä frequency. Using a bandpass filter on 7-9 years of ozone profiles from each site provides clear detection of STT events, with maximum occurrences during summer and minimum during winter for all three sites. The majority of tropospheric ozone enhancements owing to STT events occur within 2.5 and 3 km of the tropopause at Davis and Macquarie Island respectively. Events are more spread out at Melbourne, occurring frequently up to 6 km from the tropopause. The mean fraction of total tropospheric ozone attributed to STT during STT events is ∼ 1.0-3.5 % at each site; however, during individual events, over 10 % of tropospheric ozone may be directly transported from the stratosphere. The cause of STTs is determined to be largely due to synoptic low-pressure frontal systems, determined using coincident ERA-Interim reanalysis meteorological data. Ozone enhancements can also be caused by biomass burning plumes transported from Africa and South America, which are apparent during austral winter and spring and are determined using satellite measurements of CO. To provide regional context for the ozonesonde observations, we use the GEOS-Chem chemical transport model, which is too coarsely resolved to distinguish STT events but is able to accurately simulate the seasonal cycle of tropospheric ozone columns over the three southern hemispheric sites. Combining the ozonesonde-derived STT event characteristics with the simulated tropospheric ozone columns from GEOS-Chem, we estimate STT ozone flux near the three sites and see austral summer dominated yearly amounts of between 5.7 and 8.7 × 10 17 molecules cm −2 a −1 .

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Section: Stt Event Climatologiessupporting

confidence: 78%

Section: Ozonesonde Record In the Southern Oceanmentioning

confidence: 99%

Section: Classifying Synoptic Conditions During Stt Eventsmentioning

confidence: 99%

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Stratospheric ozone intrusion events and their impacts on tropospheric ozone in the Southern Hemisphere

et al. 2017

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“…The eastern Mediterranean and central Asian region is a global hotspot of tropopause-folding activity (Tyrlis et al, 2014), which is related to ASMA dynamics and generates enhanced O 3 levels through stratosphere-troposphere exchange (Akritidis et al, 2016). If the ASMA circulation encompasses that tropopause folding hotspot, it may pick up stratospheric entrainments.…”

Section: Entrainment Of Tropopause Layer Airmentioning

confidence: 99%

Dynamics and composition of the Asian summer monsoon anticyclone

et al. 2018

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Abstract. This study places HALO research aircraft observations in the upper-tropospheric Asian summer monsoon anticyclone (ASMA) into the context of regional, intra-annual variability by hindcasts with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. The observations were obtained during the Earth System Model Validation (ESMVal) campaign in September 2012. Observed and simulated tracer-tracer relations reflect photochemical O 3 production as well as in-mixing from the lower troposphere and the tropopause layer. The simulations demonstrate that tropospheric trace gas profiles in the monsoon season are distinct from those in the rest of the year, and the measurements reflect the main processes acting throughout the monsoon season. Net photochemical O 3 production is significantly enhanced in the ASMA, where uplifted precursors meet increased NO x , mainly produced by lightning. An analysis of multiple monsoon seasons in the simulation shows that stratospherically influenced tropopause layer air is regularly entrained at the eastern ASMA flank and then transported in the southern fringe around the interior region. Radial transport barriers of the circulation are effectively overcome by subseasonal dynamical instabilities of the anticyclone, which occur quite frequently and are of paramount importance for the trace gas composition of the ASMA. Both the isentropic entrainment of O 3 -rich air and the photochemical conversion of uplifted O 3 -poor air tend to increase O 3 in the ASMA outflow.

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“…Summer anticyclones, covering very large areas over North Africa, the Mediterranean basin and the European continent, are associated with the downward transport of upper troposphere ozone, especially at the interface of high-and lowpressure systems as it is also observed in Zanis et al (2014) and Tyrlis et al (2014). In addition, a frequent midsummer peak of troposphere ozone is observed over northern Europe and the Atlantic (Mantis et al, 1981;Thouret et al, 2006).…”

Section: Introductionmentioning

confidence: 95%

The geographical distribution of meteorological parameters associated with high and low summer ozone levels in the lower troposphere and the boundary layer over the eastern Mediterranean (Cairo case)

Kalabokas¹,

Thouret²,

Cammas³

et al. 2015

Tellus B: Chemical and Physical Meteorology

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A B S T R A C TIn continuation of previous research for evaluation of the high ozone levels observed during summer time over the eastern Mediterranean, MOZAIC profiles collected at the airport of Cairo from 1994 to 2008 are analysed. Average profiles corresponding, respectively, to the highest and the lowest ozone mixing ratios for the 0Á1.5 km layer over Cairo in summer (JJA) (94 profiles) are examined along with their corresponding composite maps of geopotential height (and anomalies), vertical velocity (and anomalies), specific humidity anomalies, precipitable water anomalies, air temperature anomalies and wind speed at 850 hPa. In addition, backward trajectories arriving in the boundary layer over Cairo during the days with highest or lowest ozone mixing ratios are examined. During the 7% highest ozone days at the 0Á1500 m layer over Cairo, very high ozone concentrations of about 80 ppb on average are observed from the surface up to 4Á5 km altitude. The difference in ozone concentrations between the 7% highest and the 7% lowest ozone days reaches maximum values around 60 ppb close to the ground. During the highest ozone days for both 1.5Á5 and 0Á1.5 km layer, there are extended regions of strong subsidence in the eastern Mediterranean but also in eastern and northern Europe and over these regions the atmosphere is dryer than average. In addition, characteristic profiles with the highest ozone concentrations in the 0Á1500 m layer are examined in order to assess the influence of atmospheric transport and photochemistry on the ozone concentrations over the area.

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On the linkage between the Asian summer monsoon and tropopause fold activity over the eastern Mediterranean and the Middle East

Cited by 76 publications

References 75 publications

Stratospheric ozone intrusion events and their impacts on tropospheric ozone in the Southern Hemisphere

Stratospheric ozone intrusion events and their impacts on tropospheric ozone in the Southern Hemisphere

Dynamics and composition of the Asian summer monsoon anticyclone

The geographical distribution of meteorological parameters associated with high and low summer ozone levels in the lower troposphere and the boundary layer over the eastern Mediterranean (Cairo case)

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