Dynamical processes effecting laminar structure in ozone profiles: A case study of Ankara

Günümüzde Montreal Protokolü ile kontrol altına alınan klor ve brom içeren ve ozona zarar veren kimyasal bileşikler nedeniyle stratosferik ozon son 30 yıldır azalmaktadır. Stratosferik ozon ve iklim arasında oldukça karmaşık etkileşimler bulunmaktadır. Stratosferik sıcaklık ve taşınımda meydana gelen değişimler stratosferik ozonun dağılımına ve konsantrasyonuna etki etmekte; iklim değişimleri stratosferik sirkülasyonu etkilemekte; stratosferik ozonda meydana gelen değişimler atmosferin radyatif bütçesini ve buna bağlı olarak da iklimini etkilemektedir. Kuzey yarıküre orta enlemlerinde ozon, dinamik etkilere duyarlıdır. Kış sonu ilkbahar başında hem aşağı stratosferden düşey taşınım hem de yatay izentropik taşınım orta enlem aşağı stratosfer bölgelerinde ozon değişkenliği üzerine katkı yapmaktadır. Ozonsonde ile ölçülen ozon verileri ozonun maksimum değeri altında düz bir profile sahip değildir. Özellikle kış mevsimi ya da ilkbaharda elde edilen ozon profillerinde ozon konsantrasyonunun bir sonucu olarak artan ya da azalan ince bir tabaka şeklinde gözlenen bu yapıya lamine ya da filament adı verilir. Lamine yapıyı etkileyen olası termik ve dinamik etkenlerin, seçilen bölge üzerinde etkili olan parametreleri ve bu parametrelerin etki şekillerinin ortaya çıkarılması hedeflenmektedir. Bu çalışmada Ankara’da bulunan ozonsonde istasyonundan alınan 1997-2008 dönemine ait ozon profillerinin lamine yapıları ile troposferik ve stratosferik davranışları araştırılmıştır. Elde edilen sonuçlar bu bölgede hakim olan salınımlar, solar döngü gibi dinamik etkiler yardımıyla incelenmiş; 395, 475 ve 600K seviyeleri izentropik analizleri yapılmıştır. Ozon profillerinin 2005-2008 arasındaki değişimleri ENVISAT’a ait SCIAMACHY uydusundan alınan aynı döneme ait ozon profilleriyle de karşılaştırılmıştır. Sonuçlar lamine yapının özellikle kış ve ilkbahar mevsiminde görüldüğünü ortaya koymakta ve lamine yapıdaki artış toplam ozonda da artışa neden olmaktadır. Anahtar Kelimeler: Ozon, lamine, dinamik süreçler.Stratospheric ozone has been depleted over the last 30 years due to chlorine and bromine containing chemicals that are regulated under the Montreal Protocol nowadays. There is a complex interaction between stratospheric ozone and climate. Changes in stratospheric transport and temperature effect the concentration and distribution of stratospheric ozone; changes in climate effect stratospheric circulation; changes in stratospheric ozone influence radiation budget of the atmosphere and climate. Ozone in the mid-latitudes of Northern Hemisphere is sensitive to dynamical effects. During late winter and early spring both vertical transport and horizontal isentropic transport from the lower stratosphere contribute to ozone variability in the lower stratosphere over mid-latitudes. As well as the information ozone soundings have provided on the vertical distribution of ozone, they are the source of knowledge on ozone amounts. Ozonesondes are the instruments providing year-round profiles of ozone through the lowermost stratosphere of Northern Hemisphere. Measurements of the vertical profile of ozone concentration by balloon-borne ECC (Electrochemical Concentration Cell) ozonesondes have been made since 1994 at least once in a month in Ankara. The ozone profiles measured by ozonesondes do not display a smooth shape below the maximum of the ozone layer. Relatively narrow layers of substantially increased or depressed ozone observed in the measured ozone profiles in the late winter and early spring is called laminae or filament. Laminae basically occur between the tropopause and the ozone maximum and is confined to lower stratosphere. The occurence frequency reveals a very strong seasonal variation with early spring maximum and fall minimum. In recent years the existence of the layers with depleted and enchanced ozone mixing ratios has been reported. The first systematic analysis of the laminated ozone structure was reported by Dobson (1973). In his analysis the criteria for the detection of the laminae in a certain height distance was the change of ozone to be greater than 3 mPa. It has been found that the features of laminae vary with season and latitude. Various further studies with different analysis methods have shown that the laminar structure varies with season, latitude, and the effects of dynamical processes. Laminae in ozonesonde profiles have been used in several studies as an indicator of transport. Following Reid and Vaughan (1991) laminae is defined as a sharp phenomenon deviated from the general shape of an ozone profile by at least 20 nanobars, in order not to confuse with gravity waves. In this study it is aimed to examine the thermal and dynamical effects on the laminar structure and the parameters effecting the study area. Upper level temperatures, pressure heights, potential vorticity, oscillation indices, solar cycle, polar vortex are the most effective of all parameters. Ozone profiles of Ankara-Turkey ozone sounding station for the period 1997-2008 were processed. The data was obtained from WOUDC (World Ozone and Ultraviolet Radiation Data Centre) and TSMS (Turkish State Meteorological Service). Since the data of ozonesondes for the period of 2001-2004 were missing due to software difference problem between WOUDC and TSMS, the laminar structure of the profiles of 1997-2001 and 2004-2008 were examined. The results were compared with the dynamical effects of the region and isentropic analysis were made for the 395 K, 475 K and 600 K isentropic levels respectively. The variation of the profiles for the 2005-2008 period were compared with ENVISAT (Environmental Satellite) SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric ChartograhY) data. Ozonesondes were examined for six pressure levels; ground-630 hPa; 630-400 hPa; 400-250 hPa; 250-158 hPa; 158-100 hPa and 100-30 hPa, and the trend of the ozonsonde for the selected time range was identified. The ground-level trends are found to be larger in general than those in the rest five atmospheric layers. Since laminae is minor compared to the total column ozone, the relation between the indices of the AO (Arctic Oscillation) and NAO (North Atlantic Oscillation) and the total ozone content obtained from TOMS (Total Ozone Mapping Spectrometer)-OMI (Ozone Monitoring Instrument) measurements are examined. The results show that the overall ozone content in laminae has a strong seasonal variation with a maximum in late winter/early spring and a minimum in fall. Laminae seem to contribute to seasonal variation of trends in total ozone. The ozonesonde trend is found to be positive for the selected time range. Keywords: Ozone, laminae, dynamical effects

Dynamical Effects On The Laminar Structure Of Ozone At European Mid-latitudes

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2010Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2010Stratosferik ozon ve iklim arasında oldukça karmaşık etkileşimler bulunmaktadır. Stratosferik sıcaklık ve taşınımda meydana gelen değişimler stratosferik ozonun dağılımına ve konsantrasyonuna etki etmekte; iklim değişimleri stratosferik sirkülasyonu etkilemekte; stratosferik ozonda meydana gelen değişimler atmosferin radyatif bütçesini ve buna bağlı olarak da iklimini etkilemektedir. Kuzey yarıküre orta enlemleri ve Arktik bölgede ozon dinamik etkilere duyarlıdır. Kış sonu ilkbahar başında hem aşağı stratosferden düşey taşınım hem de yatay izentropik taşınım orta enlem aşağı stratosfer bölgelerinde ozon değişkenliği üzerine katkı yapmaktadır. Ozonsonde ile ölçülen ozon verileri ozon tabakası maksimum değeri altında düz bir profile sahip değildir. Özellikle kış mevsimi ya da ilkbaharda elde edilen ozon profillerinde ozon konsantrasyonunun bir sonucu olarak artan ya da azalan ince bir tabaka şeklinde gözlenen bu yapıya lamine ya da filament adı verilir. Lamine yapıyı etkileyen olası termik ve dinamik etkenlerin, seçilen bölge üzerinde etkili olan parametreleri ve bu parametrelerin etki şekillerinin ortaya çıkarılması hedeflenmektedir. Bu çalışmada Avrupa orta enlemlerinde bulunan sekiz ozonsonde istasyonundan alınan 1997-2008 dönemine ait ozon profillerinin pozitif ve negatif lamine yapıları ile troposferik ve stratosferik davranışları incelenmiştir. Elde edilen sonuçlar bu bölgede hakim olan potansiyel vortisiti, salınımlar, solar döngü gibi dinamik etkiler yardımıyla incelenmiş izentropik analizleri yapılmış ve ozon profillerinin 2005-2008 arasındaki değişimleri ENVISAT’a ait SCIAMACHY uydusundan alınan aynı döneme ait ozon profilleriyle de karşılaştırılmıştır. Elde edilen sonuçlar lamine yapının özellikle kış ve ilkbahar mevsiminde görüldüğünü ortaya koymaktadır.There is a complex interaction between stratospheric ozone and climate. Changes in stratospheric transport and temperature effect the concentration and distribution of stratospheric ozone; changes in climate effect stratospheric circulation; changes in stratospheric ozone influence radiation budget of the atmosphere and climate. Ozone in the mid-latitudes of Northern Hemisphere and Arctic is sensitive to dynamical effects. During late winter and early spring both vertical transport and horizontal isentropic transport from the lower stratosphere contribute to ozone variability in the lower stratosphere over mid-latitudes. The ozone profiles measured by ozonesondes do not display a smooth shape below the maximum of the ozone layer. Relatively narrow layers of substantially increased or depressed ozone observed in the measured ozone profiles in the late winter and early spring is called laminae or filament. In this study it is aimed to examine the thermal and dynamical effects on the laminar structure and the parameters effecting the study area. Ozone profiles of eight ozone sounding stations from the European mid-latitudes for the period 1997-2008 were processed and the laminar structure of the profiles were examined. The results were compared with the dynamical effects of the region and isentropic analysis were made, and the variation of the profiles for the 2005-2008 period were compared with ENVISAT SCIAMACHY data. The results show that the overall ozone content in laminae has a strong seasonal variation with a maximum in late winter/early spring.DoktoraPh

Monitoring drought dynamics using remote sensing-based combined drought index in Ergene Basin, Türkiye

Remote sensing-based approaches have gained widespread usage in drought monitoring studies. However, relying on single-variable drought indices may be inadequate to provide a comprehensive understanding of drought dynamics. In this study, principal component analysis was employed to derive a combined index, namely, the combined drought index (CDI), from multiple indices such as vegetation condition index, temperature condition index, precipitation condition index, and soil moisture condition index. The CDI was subsequently employed to analyze drought occurrences in the Ergene Basin-Türkiye period from 2001 to 2020 (May to October) using MODIS data. Correlations were computed with standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI) at 1-, 3-, and 6-month scales and crop yield. The results revealed that drought incidents transpired in the Ergene Basin for at least 1 month annually. May exhibited the wettest, while September stood as the driest month. The severity of drought and its spatial extent displayed an increasing trend followed by a subsequent decline during the aforementioned period. The CDI demonstrated stronger correlations with the 1-month standardized indices than the 3- and 6-month SPI-SPEI. A robust correlation of 0.79 was also observed between the CDI and the crop yield. In general, the CDI performed well in determining the spatial and temporal patterns of the historic droughts. As a result, the CDI could be leveraged to develop effective drought monitoring and management, which could help mitigate the negative impact of drought in the fragile environment of the Ergene Basin