Eddy flux observations of evaporation and vapor advection in the Gulf of Aqaba (Eilat), Red Sea THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Dekel Shlomo Graduate Program in Civil Engineering The Ohio State University 2011 Master's Examination Committee: Dr. Gil Bohrer, Advisor Dr. Ethan Kubatko Dr. Linda Weavers Copyright by Dekel Shlomo 2011 ABSTRACT There is a large uncertainty around the rates of evaporation from desert enclosed seas, and in particular the Red Sea. The Gulf of Aqaba is long and narrow and is partially isolated from the Red Sea and the Indian Ocean by shallow and narrow straits. The long fringing reef of the Red Sea has a large economic importance to the region's tourism. In the northern part of the Red Sea, vertical mixing of the water column, which is driven by evaporation, supplies nutrients to the shallow water and, at high levels, results in favorable conditions for algae over corals, and thus, will lead to the destruction of corals. The local weather and sea surface temperature are also affected by the rates of evaporation. There are two compounding phenomena that complicate the estimation of evaporation rate in this region: (1) Although the wind is mostly oriented along the long axis of the narrow Gulf, advection of water vapor towards the dry desert surrounding the Red Sea may account for large amounts of water. (2) In the summer, the mean sea surface temperature is colder than the warm, dry desert air, leading to a thin stable boundary layer above the sea that may suppress evaporation. Atmospheric and oceanic models of the Red Sea area have run into difficulties in estimating the evaporation rates. There are very few locations where the temperature and humidity are measured routinely. Direct measurements of evaporation or on-shore advection of water vapor were not previously conducted in this region. ii In March 2009 we set up two eddy flux towers at the Inter-University Institute for Marine Science in Eilat, Israel, at the north western shore of the Gulf of Aqaba. We conducted measurements of water vapor wind and other meteorological conditions. We used the eddy-covariance technique to calculate the mass balance of water in the atmosphere above the coral lagoon near the shore. Our measurements show that a combination of advection toward land and stability conditions of the boundary layer due to negative water-air temperature gradient in hot days significantly affects the evaporation rates. iii Dedication This document is dedicated to my family. iv Acknowledgements The work was funded by Research Award #181 from the PADI Foundation to Dr. Gil Bohrer. The project was hosted, coordinated and made possible by Amatzia Genin, HUJI, and IUI, Israel. Hezi Gildor provided critical advice and assistance in the setup of the project and data interpretation. Daniel Carlson and Eliyahu Biton assisted in building the eddy-flux towers. Shahar Yair, Igal Berenshtein and Margarita Zarubin assisted in construction and maintenance of the towers and continuous data collection. I also thank Ran Nathan, Ithak Mahrer and Elad Shilo for providing additional equipment to the station. Yoav Bartan, Moti Ohavia and Timor Catz assisted in construction of and infrastructure for power supply to the towers. Ronit Bohrer-Hillel and Eyal Hillel provided transportation to the field site. I thank Ziv Bohrer and Patrice Allen for their time and effort in coordination of the expedition. Dan Vehr and the Region-1 Computational Laboratory of the OSU College of Engineering for printing presentation media. Partial support for developing the data analysis methods used in my work was provided through the OSU Institute for Energy and the Environment 2009 Seed grant to Dr. Gil Bohrer and Peter Curtis, NSF grant #DEB0918869, NASA Earth and Space Science Graduate Training Fellowship #NNX09AO26H to Anthony S. Bova and Gil Bohrer, and the U.S. Department of Energy Midwestern Regional Center of the National v Institute for Climatic Change Research (NICCR) at Michigan Technological University, under Award No. DE-FC02-06ER64158. A special gratitude to my advisor, Dr. Gil Bohrer, for his patience, guidance and support throughout the course of this research. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation. vi Vita 1998................................................................Yeshivat Hadrom High school 2008…............................................................B.Sc. Biotechnology Engineering, Ben Gurion University of the Negev 2009 to present ...............................................Graduate Research Associate, Department of Civil and Environmental Engineering, The Ohio State University Fields of Study Major Field: Civil Engineering. vii Table of Contents Abstract ............................................................................................................................... ii Dedication .......................................................................................................................... iv Acknowledgments............................................................................................................... v Vita .................................................................................................................................... vii List of Tables ..................................................................................................................... ix List of Figures ..................................................................................................................... x Chapter 1: Introduction ...................................................................................................... 1 Chapter 2: Methods ........................................................................................................... 10 Chapter 3: Results…. ........................................................................................................ 32 Chapter 4: Conclutions and Future work .......................................................................... 77 References ......................................................................................................................... 80 viii List of Tables Table 1. H2O budget for Eshel and Heavens and Ben-Sasson models .............................. 8 Table 2. Sensors on micro-meteorological towers at the IUI site .................................... 14 Table 3. Despiking values and standard deviation........................................................... 18 Table 4. Average H2O budget ......................................................................................... 63 Table 5. Comparing H2O budget ..................................................................................... 67 Table 6. Average CO2 budget ......................................................................................... 76 ix List of Figures Figure 1. Location of the Gulf of Aqaba............................................................................ 2 Figure 2. Formation of sea breezes .................................................................................... 5 Figure 3. Daily mean sea and air temperature in the Gulf of Aqaba from 2006-2009 ..... 6 Figure 4. Schematic map of the measurement setup......................................................... 11 Figure 5. Eddy flux towers located at the IUI ................................................................... 13 Figure 6. Control volume diagram .................................................................................... 16 Figure 7. Mean daily dynamics of temperature measurements during the spring ........... 34 Figure 8. Mean daily dynamics of temperature measurements during the summer ........ 35 Figure 9. Mean daily dynamics of temperature measurements during the storm ............ 36 Figure 10. Mean daily dynamics of temperature measurements ..................................... 37 Figure 11. Potential temperature during the summer ....................................................... 40 Figure 12. Potential temperature during the storm .......................................................... 41 Figure 13. Potential temperature during the spring ......................................................... 42 Figure 14. Wind rose diagram for the spring .................................................................... 44 Figure 15. Wind rose diagram for the summer ................................................................. 45 Figure 16. Wind rose diagram for the storm ..................................................................... 46 x Figure 17. Mean daily dynamics of advective wind measurements ................................ 48 Figure 18. Mean daily dynamics of change of storage .................................................... 51 Figure 19. Mean daily dynamics of water vapor during the storm .................................. 52 Figure 20. Mean daily dynamics of water vapor during the summer .............................. 53 Figure 21. Mean daily dynamics of water vapor during the spring ................................. 54 Figure 22. Mean daily dynamics of advection .................................................................. 55 Figure 23. Mean daily dynamics of horizontal flux divergence ....................................... 58