Gravity and Rossby wave signatures in the tropical troposphere and lower stratosphere based on Southern Hemisphere Additional Ozonesondes (SHADOZ), 1998–2007

Thompson, A. M.; Allen, Angela; Lee, Sukyoung; Miller, Sonya K.; Witte, J. C.

doi:10.1029/2009jd013429

Cited by 36 publications

(50 citation statements)

References 110 publications

(201 reference statements)

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“…3d in Thompson et al (2011). Here, it is seen that upper tropospheric ozone concentrations are lower in months with a high frequency of deep convection.…”

Section: Discussionmentioning

confidence: 72%

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Quantifying the deep convective temperature signal within the tropical tropopause layer (TTL)

Paulik

Birner

2012

Atmos. Chem. Phys.

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Abstract. Dynamics on a vast range of spatial and temporal scales, from individual convective plumes to planetary-scale circulations, play a role in driving the temperature variability in the tropical tropopause layer (TTL). Here, we aim to better quantify the deep convective temperature signal within the TTL using multiple datasets. First, we investigate the link between ozone and temperature in the TTL using the Southern Hemisphere Additional Ozonesondes (SHADOZ) dataset. Low ozone concentrations in the TTL are indicative of deep convective transport from the boundary layer. We confirm the usefulness of ozone as an indicator of deep convection by identifying a typical temperature signal associated with reduced ozone events: an anomalously warm mid to upper troposphere and an anomalously cold upper TTL. We quantify these temperature signals using two diagnostics: (1) the "ozone minimum" diagnostic, which has been used in previous studies and identifies the upper tropospheric minimum ozone concentration as a proxy for the level of main convective outflow; and (2) the "ozone mixing height", which we introduce in order to identify the maximum altitude in a vertical ozone profile up to which reduced ozone concentrations, typical of transport from the boundary layer are observed. Results indicate that the ozone mixing height diagnostic better separates profiles with convective influence than the ozone minimum diagnostic. Next, we collocate deep convective clouds identified by CloudSat 2B-CLDCLASS with temperature profiles based on Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Global Position System (GPS) radio occultations. We find a robust large-scale deep convective TTL temperature signal, that is persistent in time. However, it is only the convective events that penetrate into the upper half of the TTL that have a significant impact on TTL temperature. A distinct seasonal difference in the spatial scale and the persistence of the temperature signal is identified. Deep-convective cloud top heights are on average found to be well described by the level of neutral buoyancy.

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“…3d in Thompson et al (2011). Here, it is seen that upper tropospheric ozone concentrations are lower in months with a high frequency of deep convection.…”

Section: Discussionmentioning

confidence: 72%

“…Also included is the annual cycle of the LNB (red, mixing height (red, dashed), the LRM height (blue, solid), and the ozone minimum hed). (bottom) annual cycle of the ozone concentration (ppbv) at American Samoa, in Thompson et al (2011). Orange and red colors indicate relatively low values, blue latively high values.…”

Section: Discussionmentioning

confidence: 99%

Quantifying the deep convective temperature signal within the tropical tropopause layer (TTL)

Paulik

Birner

2012

Atmos. Chem. Phys.

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“…At the sites equatorward of 15 • S/N, the ENSO signal exhibits varying characteristics, with stations responding with positive ozone and temperature anomalies (for example, Kuala Lumpur and San Cristóbal), negative at others (Natal and Nairobi in Lee et al, 2010) and with distinct time lags (Randel and . Using a different diagnostic, gravity wave frequency (GWF), as inferred from ozone and potential temperature laminae within the ozone and radiosonde profiles, Thompson et al (2011) found that ENSO signatures during the SHADOZ record were most pronounced in the TTL and less so in the MT. Over subtropical Irene and Réunion, GWF is 2-3 times lower than over Kuala Lumpur, Watukosek and San Cristóbal .…”

Section: Dynamical Factors and Trend Analysismentioning

confidence: 99%

“…8). We note that the quasi-biennial oscillation (QBO) also affects tropical ozone (e.g., Witte et al, 2008;Thompson et al, 2011). Adding a term for the QBO in the regression model, Eq.…”

Section: Dynamical Factors and Trend Analysismentioning

confidence: 99%

Tropospheric ozone increases over the southern Africa region: bellwether for rapid growth in Southern Hemisphere pollution?

et al. 2014

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Abstract. Increases in free-tropospheric (FT) ozone based on ozonesonde records from the early 1990s through 2008 over two subtropical stations, Irene (near Pretoria, South Africa) and Réunion (21 • S, 55 • E; ∼ 2800 km NE of Irene in the Indian Ocean), have been reported. Over Irene a large increase in the urban-influenced boundary layer (BL, 1.5-4 km) was also observed during the 18-year period, equivalent to 30 % decade −1 . Here we show that the Irene BL trend is at least partly due to a gradual change in the sonde launch times from early morning to the midday period. The FT ozone profiles over Irene in 1990Irene in -2007 are re-examined, filling in a 1995-1999 gap with ozone profiles taken during the Measurements of Ozone by Airbus In-service Aircraft (MOZAIC) project over nearby Johannesburg. A multivariate regression model that accounts for the annual ozone cycle, El Niño-Southern Oscillation (ENSO) and possible tropopause changes was applied to monthly averaged Irene data from 4 to 11 km and to 1992-2011 Réunion sonde data from 4 to 15 km. Statistically significant trends appear predominantly in the middle and upper troposphere (UT; 4-11 km over Irene, 4-15 km over Réunion) in winter (June-August), with increases ∼ 1 ppbv yr −1 over Irene and ∼ 2 ppbv yr −1 over Réunion. These changes are equivalent to ∼ 25 and 35-45 % decade −1 , respectively. Both stations also display smaller positive trends in summer, with a 45 % decade −1 ozone increase near the tropopause over Réu-nion in December. To explain the ozone increases, we investigated a time series of dynamical markers, e.g., potential vorticity (PV) at 330-350 K. PV affects UT ozone over Irene in November-December but displays little relationship with ozone over Réunion. A more likely reason for wintertime FT ozone increases over Irene and Réunion appears to be long-range transport of growing pollution in the Southern Hemisphere. The ozone increases are consistent with trajectory origins of air parcels sampled by the sondes and with recent NO x emissions trends estimated for Africa, South America and Madagascar. For Réunion trajectories also point to sources from the eastern Indian Ocean and Asia.

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“…The second source involves large-scale equatorial waves, e.g. Kelvin waves (Webster, 1972;Gill, 1980;Wheeler et al, 2000;Ryu and Lee, 2010;Thompson et al, 2011), which are usually triggered by convection and organized convective systems. Equatorial Kelvin waves with time periods in the order of a few days lead to temperature anomalies of up to 8 K with typical values around 2-3 K (Immler et al, 2008) Middle panel: time evolution of ice crystal number concentration.…”

Section: Large-scale Dynamicsmentioning

confidence: 99%

Tropical tropopause ice clouds: a dynamic approach to the mystery of low crystal numbers

Spichtinger

Krämer²

2013

Atmos. Chem. Phys.

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Abstract. The occurrence of high, persistent ice supersaturation inside and outside cold cirrus in the tropical tropopause layer (TTL) remains an enigma that is intensely debated as the "ice supersaturation puzzle". However, it was recently confirmed that observed supersaturations are consistent with very low ice crystal concentrations, which is incompatible with the idea that homogeneous freezing is the major method of ice formation in the TTL. Thus, the tropical tropopause "ice supersaturation puzzle" has become an "ice nucleation puzzle". To explain the low ice crystal concentrations, a number of mainly heterogeneous freezing methods have been proposed. Here, we reproduce in situ measurements of frequencies of occurrence of ice crystal concentrations by extensive model simulations, driven by the special dynamic conditions in the TTL, namely the superposition of slow large-scale updraughts with high-frequency short waves. From the simulations, it follows that the full range of observed ice crystal concentrations can be explained when the model results are composed from scenarios with consecutive heterogeneous and homogeneous ice formation and scenarios with pure homogeneous ice formation occurring in very slow (< 1 cm s −1 ) and faster (> 1 cm s −1 ) largescale updraughts, respectively. This statistical analysis shows that about 80 % of TTL cirrus can be explained by "classical" homogeneous ice nucleation, while the remaining 20 % stem from heterogeneous and homogeneous freezing occurring within the same environment. The mechanism limiting ice crystal production via homogeneous freezing in an environment full of gravity waves is the shortness of the gravity waves, which stalls freezing events before a higher ice crystal concentration can be formed.

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Gravity and Rossby wave signatures in the tropical troposphere and lower stratosphere based on Southern Hemisphere Additional Ozonesondes (SHADOZ), 1998–2007

Cited by 36 publications

References 110 publications

Quantifying the deep convective temperature signal within the tropical tropopause layer (TTL)

Quantifying the deep convective temperature signal within the tropical tropopause layer (TTL)

Tropospheric ozone increases over the southern Africa region: bellwether for rapid growth in Southern Hemisphere pollution?

Tropical tropopause ice clouds: a dynamic approach to the mystery of low crystal numbers

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