Jackson Hian Wui Chang

Ground-based aerosol optical depth measurement using sunphotometers

Introduction.- Ground-Based Aerosol Optical Depth Measurement.- Near-Sea-Level Langley Calibration Algorithm.- Implementation of Perez-Dumortier Calibration Algorithm.- Conclusion.

Data Acquisition System for In Situ Monitoring of Chemoelectrical Potential in Living Plant Fuel Cells

Photosynthesis process in plants generates numerous sources of bioenergy. However, only a small fraction is readily exploited for electrical energy. The impact of environmental factors is one of the significant physiological influences on the electrical potential of the plants. Hence, we developed a data acquisition (DAQ) system for instantaneous monitoring of electrical potential in plants and Aloe vera was used as a plant sample. The static response characterization, capability index (P/T), and Pearsons coefficient of correlation procedures were applied to assess the reliability of the obtained data. This developed system offers the capability of in situ monitoring and detecting gradual changes in the electrical potential of plants up to a correlational strength of greater than 0.7. Interpretation of the electrical signal mechanisms in the Aloe vera plant and the optimization of the electricity can be achieved through the application of this monitoring system. This system, therefore, can serve as a tool to measure and analyze the electrical signals in plants at different conditions.

Implementation of perez-dumortier calibration algorithm

To avoid the unnecessary needs to travel to high altitude for sunphotometers calibration, Perez-Dumotier calibration algorithm has been used as an objective means to select the right intensity data so that the calibration can be performed at any altitude levels. The governing theory of the algorithm was discussed in the previous chapter. This chapter presents information on how to implement the Perez-Dumotier calibration algorithm using actual field measurement. The implementation of the filtration procedure in step-by-step is discussed to render better framework of the proposed calibration algorithm. The aerosol retrieval inversion uses the extraterrestrial constant obtained from the final Langley plot to calculate retrieved AOD. The implementation example uses irradiance-matched technique by i-SMARTS radiative transfer code to derive corresponding reference AOD for validation purposes. The reliability of the technique was substantiated by radiative closure experiment to verify the promising direct solar irradiance to accurately derive the reference AOD values.

Ground-Based Aerosol Optical Depth Measurements

This chapter presents a detailed overview on the theory of aerosol optical depth retrieval with the emphasis on ground-based sunphotometry technique. To further discuss on the calibration issue as mentioned previously, this overview also includes the principle of the oldest passive ground-based calibration method, Langley calibration to provide an insight on the working mechanism of the method. The final part in this chapter compiles the previous existing Langley calibration method in a chronological sequence to render a better comprehension on its development from the past to present time.

Near-Sea-Level Langley Calibration Algorithm

As compared to other methods, measurement of aerosol optical depth (AOD) using sunphotometers offer several advantages. However, it suffers a drawback as calibration of the instrument required to be performed at high altitude due to temporal drifts in the atmospheric condition during the calibration. To solve this, a new Langley calibration algorithm has been designed for AOD measurement using spectroradiometer instrument. The key advantages of the proposed algorithm are its objectivity, computational efficiency and the ability to detect short intervals of cloud transits. It avoids travelling to high altitude mountain that the conventional calibration procedure always practiced for frequent calibration. Most importantly, neither it requires priori knowledge of the instrument calibration nor a collocated calibrated instrument for nominal calibration transfer to perform the cloud-screening procedure.