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İstanbul Teknik Üniversitesi (2015)

Determination Of Energy Fluxes Of Crops by Using Micrometeorological Methods

ÖZKOCA Yunus

Titre : Determination Of Energy Fluxes Of Crops by Using Micrometeorological Methods

Mikrometeorolojik Yöntemlerle bitkilerin Enerji Akılarının Belirlenmesi

Auteur : ÖZKOCA Yunus

Université de soutenance : İstanbul Teknik Üniversitesi

Grade : Master of Science (MS) 2015

Résumé partiel
The growth in world population increases the demand of water for biological and ecological life, agricultural and industrial production activities. The only source of water is precipitation and global climate change affects the distribution of precipitation in the world. Distribution of precipitation may result in natural disasters like droughts and floods depending on the region. Thus every water drop is getting more and more important for human being. The fundamentals of atmospheric sciences rely on energy and water balance and every atmospheric system is controlled by the overall balance of energy and water. Energy balance is a natural and irreversible system and mostly cannot be affected by outside sources. On the other hand, water balance is composed of changeable components and exposed to intervention that makes it more crucial. At this point, determination and control of water loss are being much more significant. Main component of water loss is evapotranspiration in terrestrial ecosystem. Evapotranspiration, the most important and common component of energy and water balance, is defined as the sum of evaporation and plant transpiration from the Earth’s land and ocean surfaces to the atmosphere and composed of land – atmosphere interaction. In order to determine evapotranspiration rate, there are several measurement and calculation techniques in use around the world. Accurate measurements of the vertical transfer of mass and energy on the land surface are necessary to understand the various components of hydrological cycle. The two most commonly used methods to measure evapotranspiration rates are the Bowen Ratio Energy Balance and Eddy Covariance methods. Both methods are suitable when a number of requirements, mostly with respect to terrain topography and homogeneous fetch extension, are fulfilled. Furthermore, meteorological variables can be used to calculate evapotranspiration rates. Penman – Monteith combination equation is the most frequently used method for this purpose. As a matter of fact that lysimeters are used to measure evapotranspiration directly on the ground, but this technique is very expensive and difficult to use in forest and cultivated area. The Bowen Ratio Energy Balance (BREB) is a micrometeorological method often used to estimate energy fluxes (latent heat, sensible heat fluxes) cause of simplicity, robustness, and affordability. It is an indirect measurement method based on the measurements of net radiation, soil heat flux, temperature and humidity of air at two different levels. The partitioning of available energy between sensible and latent heat can usually obtained by BREB method. The errors associated with BREB method should be analyzed to determine analytically the reliable values of Bowen ratio, latent heat and sensible heat fluxes. The Eddy Covariance (EC) method is one of the most accurate, direct and defensible approaches available to date for measurements of gas fluxes and monitoring of gas emissions from areas with sizes ranging from a few hundred to millions of square meters. It is a key atmospheric measurement technique to measure and calculate vertical turbulent fluxes within atmospheric boundary layers. This technique consists of direct and very fast measurements of actual gas transport by a three dimensional wind speed in real time in situ.

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