Uçak ve Uzay Bilimleri Fakültesi

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http://hdl.handle.net/11527/19780

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  • Öge
    10th International Symposium on Atmospheric Sciences : e-proceedings, 18-21 October 2022
    (İTÜ Yayınevi, 2023) Meteoroloji Mühendisliği ; Kahya, Ceyhan ; Öztopal, Ahmet
  • Öge
    e-Proceedings of the 9th International Symposium on Atmospheric Sciences
    (İstanbul Teknik Üniversitesi, 2019-10) Department of Meteorology ; Şaylan, Levent ; Koçak, Kasım ; Kaymaz, Zerefşan ; Özgür, Evren ; Eyigüler, Ceren
  • Öge
    Effects of climate trends and variability on tree health responses in the Black Sea and Mediterranean forests of Türkiye
    (Springer, 2024) Dogan Ciftci, Nida ; Şahin,, Ahmet Duran ; Yousefpour, Rasoul ; Christen , Andreas ; Meteoroloji Mühendisliği
    To adapt forest ecosystems and forest management to climate change, it is essential to know which forest regions and which tree species are resilient to climate variability and which ones are possibly affected most by past and anticipated future changes. In this contribution, for the main forest regions of Türkiye and six tree species, recent climate variability and trends were quantified and statistically correlated to record tree defoliation and vitality. Climate variables considered are maximum temperature (Tmax), minimum temperature (Tmin), mean temperature (Tmean), and total precipitation (Prcp), which are compared to forest health responses recorded as part of the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) on 277 plots across forests along the Black Sea and Mediterranean regions. In addition, long-term data on satellite measurements of the normalized difference vegetation index (NDVI) were extracted for the same 277 plots for the period 2008–2020. Firstly, 30 years (1991–2020) of reanalysis of climate variables from ECMWF were extracted for all plots; secondly, individual correlations and cross-correlations of climate variables and tree health and vitality were computed for the period 2008–2020 (significance level of 95%) for the four most dominant species from the Black Sea forests (F. orientalis, Q. cerris, P. sylvestris, P. orientalis) and two species from Mediterranean forests (P. brutia and C. libani). Temperature showed a stronger effect on most species than precipitation. Finally, time-lagged correlations were analyzed for seven-time lags (significance level of 95%) to evaluate legacy effect. The analysis revealed that different tree species from the two regions show different responses to climate variables. Species in the Mediterranean region are more resistant to droughts and climatic variations. Legacy effects of defoliation and NDVI have lasted for at least 2 years.
  • Öge
    International symposium on remote sensing in meteorology: METEO IRS 2021, 1-3 December 2021, İstanbul/TÜRKİYE
    (ITU Press, 2022-11-28) International symposium on remote sensing in meteorology (2022: İstanbul) ; Meteoroloji Mühendisliği ; Öztopal, Ahmet ; Akın, Melek ; Durmaz, Abdurrahman
    In today's world, remote sensing is an important tool used in many fields. Atmospheric Sciences is the main field in which remote sensing is used 24/7 operationally. This technology makes important contributions to detect, understand and solve meteorological, climatological, hydrological problems and to detect and track ordinary or extreme weather events. In addition, remote sensing has undeniable contributions to forecasters and decision makers in terms of very short-term weather forecasting and early warning. Considering that our country's studies on Meteorological Remote Sensing are not sufficient in number and level, it is aimed to increase the studies on this subject throughout the country with the International Symposium on Remote Sensing in Meteorology - METEO IRS 2021. The interest shown in the first METEO IRS, with a total of 9 invited speakers from the United States, Finland, Italy and Turkey, is encouraging. I would like to express my gratitude to all the participants for their contributions, and I wish to be together again in METEO IRS 2023. Dr. Ahmet Öztopal Chair of METEO IRS 2021
  • Öge
    Variables controlling growing season carbon dynamics in desert shrub ecosystem
    (Springer, 2024) Şaylan, Levent ; Kimura, Reiji ; Başakın, Eyyup Ensar ; Kurosaki, Yasunori ; 0000-0003-3233-0277 ; 0000-0001-7700-3566 ; 0000-0002-9045-5302 ; 0000-0002-9595-0484 ; Meteoroloji Mühendisliği
    Arid and semi-arid lands (drylands) are under the influence of extreme environmental conditions and cover large areas on Earth’s land surface. Determining temporal and spatial variations of the greenhouse gas and energy exchange in these ecosystems will provide a better understanding of both, the dynamics between the drylands’s surface and the atmosphere and the importance in climate change. In this study, CO2 exchanges over a shrub steppe ecosystem were determined using the Eddy Covariance method during both dry and wet growing seasons in the Gobi Desert, Mongolia. The net ecosystem exchange (NEE) was modeled using the extreme gradient boosting method (XGBOOST). Variables influencing NEE were estimated employing the SHapley Additive exPlanations algorithm (SHAP). The XGBOOST predictions demonstrated impressive results across all growing seasons, with high performance metrics (R2 = 0.821; NSE = 0.817), particularly notable during the wet season (R2 = 0.932; NSE = 0.929). The total NEE changed between 79.7 and -110.4 gC m−2 throughout the growing seasons. Especially the precipitation before the growing period has a positive impact on carbon sequestration in the shrub ecosystem in the following dry season. A high similarity was found in the patterns of daily NEE of all growing seasons and normalized difference vegetation index (NDVI), albedo, soil water content, temperature, sensible heat flux, the difference between air and soil temperature in desert shrub ecosystem. Although NDVI was the dominant factor during the wet season, there was a weaker relationship between these factors and NEE in the dry season than in the wet season.