Some notes concerning the Fourier transformation of auto-correlation functions

Passage of autocorrelation function to frequency spectrum by numerical Fourier transformatio

New Statistical downscaling methods and applications for Turkey

Hava ve iklim süreçlerinin yeryüzündeki yaşam üzerinde hayati etkileri vardır. İklim değişkenliği ve değişiminin anlaşılabilmesi, bölgesel ve yerel iklim tanılarının geliştirilmesi, iklim çalışmalarının temel konularından biridir. İklim etkilerini araştıranlar genelde iklim değişiminin ve değişkenliğinin geçmişi, bugünü ve geleceği hakkında detaylı ve doğru bilgilere gereksinim duyarlar. İklim değişimi ve değişkenliği konusunda önemli ve temel araçlar genel dolaşım modelleridir (GDM). Ne yazık ki kaba sayısal çözünürlük üzerinde çalıştırılan GDM’ler yerel iklim değişimi ve değişkenliği hakkında doğru bilgi veremezler. Bu bağlamda, GDM’lerin kısıtlarından dolayı “ölçek küçültme” stratejilerinin geliştirilmesine gerek vardır. İklim araştırma ve etkilerinin arasındaki farklı ölçekler; “ölçek küçültme” ve “ölçek büyültme” yaklaşımları ile birbirine bağlanabilir. Bu çalışma, yeni ölçek küçültme yöntemlerini geliştirme ve Türkiye üzerine uygulanması konusunda ilk ve tek araştırmadır. Anahtar Kelimeler: Bölgesel, genel dolaşım modeli, iklim etki, ölçek küçültme, Türkiye, yinelemeli yapay sinir ağları.Weather and climate have a profound influence on life on earth. Understanding climate variability and climate change reveals the increasing need for improving regional and local-scale climate diagnosis which is one of the main goals of climate research. The climate impact researches usually require accurate and detailed climate information on yesterday, present, and tomorrow with high resolution space scale. The main and important tools of studying climate are general circulation models (GCMs). Unfortunately, GCMs running on coarse resolution may not be able to detect the local scale climate variability. The spatial-scale mismatch between climate research and climate impact studies has to be bridged by ?downscaling? on the side of the climate research and ?upscaling? on the side of the climate impact research. This study is the first research of developing downscaling strategies over Turkey. Two new downscaling strategies for climate diagnosis are developed in this study. The proposed methods are based on artificial recurrent neural networks (RNN) and multivariate statistical techniques that derive transfer functions from the large-scale free troposphere variables of which are assumed to govern the local climate over Turkey. This study presents two new approaches for downscaling monthly near-surface air temperature and total precipitation for Turkey stations by surface large-scale pressure systems and upper air circulations derived from National Centers for Environmental Prediction- National Center of Atmospheric Research (NCEP-NCAR) Reanalysis data sets. Keywords: Regional, general circulation model, climate impact, downscaling, Turkey, artificial recurrent neural networks

Modeling impacts of climate change scenario over Turkey

Bu çalışmada izlenen yöntem, Türkiye ve çevresi üzerinde, günümüz ve gelecek için NASA-Sonlu Hacim Genel Dolaşım Modeli (fvGCM) tarafından üretilen projeksiyonların, ICTP-Bölgesel İklim Modeli (RegCM3) kullanılarak dinamik olarak ölçek küçültülmesidir. Günümüz (1961-1990, RF) ve gelecek (2071-2100, A2) simülasyonları için, Hükümetlerarası İklim Değşikliği Paneli (IPCC) tarafından belirlenmiş sera gazları emisyon senaryoları dikkate alınmıştır. A2 ve RF simülasyonlarının sıcaklık ve yağış için yapılan mevsimsel analizleri Türkiye’nin iklimsel bölgeleri üzerinde alansal ortalama alınarak ayrı ayrı incelenmiştir. A2 simülasyonuna göre, Türkiye üzerinde sıcaklıklardaki en dramatik değişim yaz mevsiminde Ege Bölgesi üzerindeki 5 ila 6 °C’ler arasındaki artıştır. Kış ayları dışındaki mevsimlerde artış, 3-4 °C arasında değişmektedir. Gelecek simülasyonundaki minimum artış, kış mevsiminden 2-3 °C olarak hesaplanmıştır. Yine A2 simülasyonunda, Doğu Karadeniz dağları boyunca uzanan bölgede kış yağışlarıdaki artış, rüzgar paterninin değişmesiyle orografik etkinin güçlenmesine bağlıdır. Türkiye’nin güneyi üzerinde de rüzgar paterninin güneyli değişimine bağlı olarak kış yağışlarında çok ciddi azalmalar (% 34) model sonuçlarında ortaya çıkmıştır. Sonbahar meviminde ise Güneydoğu Anadolu Bölgesinde yağışlarda % 50’lere varan artışlar görülmüştür. Bu artışların ana nedeni değişen rüzgar akımlarının taşıdığı nem olabilir. Gelecek iklim senaryosunda Fırat ve Dicle su havzalarını kapsayan alandaki kış yağışlarında yaşanan azalmalarla, küresel ısınmaya paralel sıcaklık artışının buharlaşmaya etkisiyle birlikte değerlendirildiğinde, model sonuçlarının hidrolojik analizlerinin önemi daha çok ortaya çıkmaktadır. Anahtar Kelimeler: İklim değişimi, bölgesel iklim modellemesi, ölçek küçültme.The Earth's climate has changed many times and fluctuated between the glacial and the interglacial periods since its formed. These changes related to natural forcings like volcanic eruptions, intense tectonic activity, solar activity and variation of Earth's orbital parameters, were sometimes very dramatic. Today, the global change we face to is different than the natural changes occurred in the past. Human-induced climate change has been taken into consideration extensively within the last decade more than ever. Recent advances in both climate observing systems and methodologies to detect the climate change, as well as broader global coverage of observations help scientists to better understand the climate system. Scientific studies which are led by IPCC (Intergovernmental Panel on Climate Change) showed that dominance of anthropogenic effect on global warming is indisputable (IPCC, 2007). Regional climate change modeling has been applied to many different areas such as agriculture, seasonal forecasting, hydrology applications, paleoclimate and climate projections. Because of its ability to resolve sharp gradients and contrasts in the surface conditions, the regional climate modeling approach yields more accurate and spatially detailed information. In this study,  the ICTP-Regional Climate Model version 3 (RegCM3) has been used to downscale present and future scenario simulations generated by the NASA-Finite Volume General Circulation Model (fvGCM) over Turkey and its surroundings. The present-day (1961-1990, RF) and the future climate change simulations (2071-2100, A2) are based on the IPCC Greenhouse Gases emissions, which are CO2, CH4, N2O, and CFC11- CFC12. Emission scenarios for these gases have been implemented into the radiation scheme for the simulations and, relatively high resolution of 30 km is adopted to resolve the complex topography of the domain. The role of the domain characteristics such as complex land-sea distribution determines the sub-regional climatic features and spatial climate variability. This diverse climatic structure of the region brings great challenge for regional climate modeling. Levantine Sea, Aegean Sea and Black Sea are main moisture sources of the Turkey and its surrounding regions. A2 simulation results which correspond future climate indicate that warming over Turkey's climatic zones is in the range of 2-5 °C. Summer temperature changes are more dominant in the A2 scenario. This pattern has also been observed for neighboring countries. Summer heat wave conditions over Aegean region (5 °C increase) are more obvious in the area averages than in the spatial pattern based model results. The difference between the summer and winter change is about 3 °C and it could play an important role in contributing to temporal shifts of the transition seasons. In addition, warming in winter over eastern and southeastern of Turkey which have higher altitudes are nearly 1 °C higher than for Marmara and Aegean regions which have lower altitudes. Autumn temperature changes for all regions are affected by the extension of the summer season extension due to the global warming. Most significant precipitation changes in A2 scenario have been occurred over the Mediterranean region of Turkey in winter and over the Southeastern of Turkey in autumn. Our analyses show a 34% decrease over Mediterranean region and it is related to the change in the atmospheric circulation which in turn causes reduced orographic forcing. The same circulation change also enhanced orographic forcing especially over the east of the Black Sea region and results in significant precipitation increase. Decreases over the Aegean and Southeastern regions are around 20% in winter. Autumn precipitation over Southeastern region increased as high as 48%. Flow pattern changes which also affected Iraq and Syria are consistent with enhanced moisture availability over this region which may account for the major precipitation increase. All precipitation changes in winter and autumn are also statistically significant. The amount of precipitation over Turkey in summer season is very little except eastern Black Sea region. Therefore, percent changes for summer precipitation over all of regions could not be meaningful to discuss. Analyses of A2 simulation show that combined effect of precipitation decrease and evapotranspiration increase related to temperature increase could play major role to reduce water resources over Turkey. Especially, there could be significant problems over Euphrates-Tigris basin because of the decreasing water availability in future scenario. Keywords: Climate change, regional climate modeling, downscaling scenarios

A STUDY OF GREENHOUSE EFFECTS USING ZERO, ONE AND TWO-DIMENSIONAL CLIMATE MODELS

In this study a hierarchy of simple climate models is built and used to assess the impact of changes in the trace gas abundance of Earth's atmosphere on the global and zonal surface temperatures. Two of the four models presented use the Equivalent Radiative Atomosphere approximation to treat the greenhouse effect of water vapor, carbon dioxide and ozone. The other two models have vertically resolved atmospheres and use broad band absorptance and emissivity models in the treatment of radiative exchanges. Two of the models have resolution in the meridional direction and the horizontal energy transport is approximated by a linear, constant coefficient diffusion. A series of sensitivity experiments is conducted with these models to assess the relative importance of various parameters and modeling assumptions. All of the models are sensitive to variations in solar irradiance: the range of the response, quantified in terms of the (beta) parameter, ranges from 71 K to 186 K. The response is highly dependent on the strength of the water vapor feedback in the particular model. Another series of calculations is concerned with the impact of changes in the CO(,2) abundance of the atmosphere on the surface temperatures. The range of the response to a doubling of the CO(,2) abundance is from 2.5 K to 10 K for ERA based models and from 1.9 K to 6 K for the others. The response depends on the latitude and most importantly on the water vapor feedback strength. The effect of minor trace gases O(,3), CH(,4) and N(,2)O on the globally averaged temperature is also studied. A 50% decrease in O(,3) column density lowers the surface temperature by 0.28 K. A doubling of the present atmospheric abundance of CH(,4) and N(,2)O heats the surface by 0.25 K and 0.42 K, respectively

Kendini tanımlayan yer sistem modellerine doğru: Bir iş akışı uygulaması

The application of scientific workflow systems for orchestrating complex tasks is still an open research area. In particular, earth system related modeling applications consists of different tasks that are closely related to each other and scientific workflow systems can be used to simplify these sub processes and their relationships. The motivation for this work is driven by the complexities of running a large modeling system on a high performance computing and network systems and need to reduce those complexities, particularly for the average user.In this study, it is presented and analyzed a new methodology to combine scientific workflow system and modeling framework approach together to create standardized work environment. Then, the proposed methodology is tested using a typical and realistic earth system modeling application. The result of example workflows that are based on the proposed methodology is a part of this study.A Modeling framework is a standardized programming environment for combining model components and couplers of different kinds of earth system models using a common calling interface. Earth System Modeling Framework (ESMF) is one of the most popular examples for this approach. It consists of a superstructure for coupling components of Earth system applications and an infrastructure of robust, high-performance utilities and data structures that ensures consistent component behavior. Extending beyond the modeling framework approach, scientific workflow systems create standardized interfaces to a variety of technologies and automate the execution and monitoring of a heterogeneous workflow. Namely, a scientific workflow system is a problem-solving environment that simplifies tasks by creating meaningful and easy understandable sub-tasks and combining them to form executable data management and analysis pipelines. Kepler was chosen as the workflow environment for this work because it is open source, platform independent, and it supports different models of computation such as Process Network (PN) and Synchronous Data Flow (SDF). Kepler is a scientific workflow system that is based on the Ptolemy II project. The actor-oriented design of Kepler enables users to create hierarchically structured scientific workflows. The overall execution of model is controlled by separate component that is called a director (a special actor). Kepler supports different model of computation types via its directors.In application example, a regional coupled climate modeling system is developed for Mediterranean region and integrated into workflow system to provide better representation of regional climate system. This application has crucial importance in downscaling output of the global circulation models over Turkey and near regions. It also can be used to create better representation of regional climate for the future scenarios. The workflow application also collects provenance information automatically from the coupled earth system modeling system to reproduce, compare and debug results. The coupled atmosphere-ocean modeling system is based on NCAR's Weather Research and Forecasting (WRF) and Regional Ocean Modeling System (ROMS) model. To couple atmosphere and ocean models the ESMF library is used. For the atmospheric component (WRF), the experimental ESMF-IO structure is used to create ESMF fields and states to share data between different model components. The WRF ESMF-IO is also modified to add field level metadata into coupling variables (heat and momentum fluxes) of atmospheric model. In ocean component (ROMS), the coupler code is written to control each model component and also the gridded component code is developed to run each earth system model via ESMF init, run and finalize methods. The gridded component level metadata is added into coupler to create prototype version of self-describing modeling system. The results show that the developed workflow environment is capable of running different earth system models on a different high performance computing resource with a meaningful abstraction. The proposed work environment acts as an abstraction layer and hides the detail of the used infrastructure and earth system model from user and it also collect standardized provenance information about both model and computing resource to represent the work environment as possible as it can. Keywords: Scientific workflow, model coupling, provenance information, Kepler, ESMF.Bilimsel iş akış sistemlerinin karmaşık bileşen ve süreçler içeren çalışmalarda kullanılması, günümüzde oldukça popüler bir araştırma alanıdır. Özellikle yer sistem bilimleri açısından bakıldığında, birbirlerine sıkı bir şekilde bağlı, birçok alt bileşen içeren yer sistem modellerine ait süreçlerin basitleştirilmesi ve modüler bir yapıya kavuşturularak standartlaştırması için, bilimsel iş akış sistemleri kullanılabilir. Bu çalışmanın asıl amaçlarından biri, karmaşık yer sistem modelleme uygulamalarının, yüksek başarımlı hesaplama sistemlerinde çalıştırılmasının gittikçe zorlaşması, kendi kendisini tanımlayan yer sistem modellerine ve varolan karmaşık modelleme sistemlerinin anlamlı bir şekilde soyutlaştırılarak ortalama bir kullanıcı seviyesine indirgenmesine duyulan ihtiyaçtır. Bu amaçla, literatürde sıkça kullanılan bilimsel iş akışı ve çerçeve yaklaşımlarının birleştirilerek standartlaştırılmış bir çalışma ortamının yaratılması için yeni bir metodoloji geliştirilmiştir. Önerilen metodolojinin sınanması amacıyla, gerçekçi bir yer sistem modelleme uygulaması kullanılmış ve sonuçları analiz edilmiştir. Bu amaçla geliştirilen uygulama örneği, çerçeve yaklaşımı kullanılarak birleştirilmiş bir atmosfer-okyanus model sisteminin, bölgesel iklim sistemini daha gerçekçi olarak modellemek amacıyla iş akış sistemine entegre edilmesi ve model bileşenlerinden köken bilgisinin otomatik olarak toplanması süreçlerini içermektedir. Sonuçlar iş akışı ortamına entegre edilen model sistemlerinin daha kolay kullanılabildiğini ve toplanan köken bilgisinin çalışmanın evrimini kayıt altına alması açısından son derece önemli olduğunu göstermektedir. Ayrıca modellerin kuple edilmesi için kullanılan çerçeve uygulaması (ESMF), her bir alt yer sistem modeli için standart bir arayüz tanımlayarak model kuple sürecini ve yönetimini kolaylaştırmaktadır. Anahtar Kelimeler: Bilimsel iş akışı, çerçeve yaklaşımı, köken bilgisi, Kepler, ESMF