English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

A combination of POAM III aerosol extinction and CHAMP RO temperaturemeasurements are used to examine the role of atmospheric gravity wavesin the formation of Antarctic Polar Stratospheric Clouds (PSCs). POAM IIIaerosol extinction observations and quality flag information are used toidentify Polar Stratospheric Clouds using an unsupervised clustering algorithm. A PSC proxy, derived by thresholding Met Office temperature analyses with thePSC Type Ia formation temperature (TNAT), shows general agreement withthe results of the POAM III analysis. However, in June the POAM III observationsof PSC are more abundant than expected from temperature threshold crossings infive out of the eight years examined. In addition, September and October PSCidentified using temperature thresholding is often significantly higher thanthat derived from POAM III; this observation probably being due to dehydrationand denitrification. Comparison of the Met Office temperature analyses withcorresponding CHAMP observations also suggests a small warm bias in the MetOffice data in June. However, this bias cannot fully explain the differences observed. Analysis of CHAMP data indicates that temperature perturbations associatedwith gravity waves may partially explain the enhanced PSC incidence observedin June (relative to the Met Office analyses). For this month, approximately40% of the temperature threshold crossings observed using CHAMP RO data areassociated with small-scale perturbations. Examination of the distribution oftemperatures relative to TNAT shows a large proportion of June datato be close to this threshold, potentially enhancing the importance of gravitywave induced temperature perturbations.Inspection of the longitudinal structure of PSC occurrence in June 2005 alsoshows that regions of enhancement are geographically associated with theAntarctic Peninsula; a known mountain wave "hotspot". The latitudinal variationof POAM III observations means that we only observe this region in June–July,and thus the true pattern of enhanced PSC production may continue operating into later months. The analysis has shown that early in the Antarctic winter stratosphericbackground temperatures are close to the TNAT threshold (and PSCformation), and are thus sensitive to temperature perturbations associated withmountain wave activity near the Antarctic peninsula (40% of PSC formation).Later in the season, and at latitudes away from the peninsula, temperatureperturbations associated with gravity waves contribute to about 15% of theobserved PSC (a value which corresponds well to several previous studies).This lower value is likely to be due to colder background temperatures alreadyachieving the TNAT threshold unaided. Additionally, there is a reductionin the magnitude of gravity waves perturbations observed as POAM III samplespoleward of the peninsula

Can gravity waves significantly impact PSC occurrence in the Antarctic?