Wave and Surge Forecasting Along the Egyptian Coast of the Mediterranean Sea
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ARAB ACADEMY FOR SCIENCE AND TECHNOLOGY AND MARITIME TRANSPORT Alexandria, Egypt WAVE AND SURGE FORECASTING ALONG THE EGYPTIAN COAST OF THE MEDITERRANEAN SEA Submitted By Mamdouh Mohamed Meligy Mohamed Shalaby A thesis submitted to the Arab Academy for Science and Technology and Maritime Transport, in fulfillment of the requirements for the award of: Master Degree in Maritime Transport Technology (Meteorology) Supervised By Prof. Dr. Abdel Aziz Abdel Baeth Hamed Chairman of Meteorology Program 2000 DECLARATION I hereby certify that the source of the material in this thesis that is not my work has been identified, and that no material is included for which a degree has previously been conferred on me. The contents of this thesis reflect my own personal views, and are not necessarily endorsed by the Arab Academy for Science and Technology and Maritime Transport. Signature: Mamdouh Mohamed Meligy Date Supervised by: Prof Dr. Abde~l _.~ Chairman of Meteorology Program. College of Maritime Transport and Technology. Assessed by: Name: Prof Dr. Ahmed El-Gindy. f).!1.~~~ Office :Alexandria University. Name :Commodore\ Samir A.A. Khalifa. ~ .. -J f2. ~~. t~~;-- Office :Egyptian Navy. Name: Prof Dr. Saad Mesbah. S ~ F'i'o eLi. g ........... Office: Arab Academy for Science and Technology and Maritime Transport. Name: Prof Dr. Refat Rashad. t ~ G Office: Arab Academy for Science and Technology and Maritime Transport . .. -11- Acknowledgement "Praise be to Allah, who has guided us to this felicity, never could we have found guidance, had it not been for the guidance of Allah: indeed it was the truth" I wish to express my deep gratitude to Prof. Dr. Abdel Aziz Abdel Baeth Hamed, Professor of Meteorology and Chairman of Meteorology Program, College of Maritime Transport and Technology, Arab Academy for Science and Technology and Maritime Transport for supervising the work and reading the manuscript of the thesis. I am indebted to him for his able guidance and valuable advice. The author extends SlOcere thanks to Rear Admiral. Ahmed Saber Sleem, Commander in chief, Egyptian Navy Forces and Ret. Commodore Wagdy M. Fouad former Director of Hydrographic Department, Egyptian Navy Forces and Commodore Samir A.A. Khalifa Director of Hydrographic Department, Egyptian Navy Forces for their continuous help and support through out preparing this thesis. The author also extends sincere thanks to Prof. Dr. Refat Rashad, Chairman of higher studies Department, College of Maritime Transport and Technology, Arab Academy for science, and Technology and Maritime Transport for his help during my study. Many thanks are also due to the staff members of: Hydrographic Department of the Egyptian Navy Forces, Meteorology Program, College of Maritime Transport and Technology, Arab Academy for science, and Technology and Maritime Transport, and Egyptian Meteorological Authority for their valuable assistance. -111- Abstract Lack of sufficient knowledge of coastal wave climates and storm surges hinders management and treatment of coastal problems. This limits the data applicability for describing the basic stochastic processes, which govern beach changes along the Egyptian coast of the Mediterranean Sea. The growth of the waves is governed by the following factors: • The depth of the water. • The strength of the wind. • The duration of the wind. • The fetch of the wind. In this study the author discussed the available methods for wave forecasting and the most acceptable method of forecasting the waves along the Egyptian coast of the Med. Sea, as well as studying the effect of the depressions during their courses, on the state of the sea along the Egyptian coast ofMed. Sea. The author also studied the wave characteristics from the observed waves at Alexandria, Abu Quir and Ras EI-Bar during the period 1992-1995 by the Hydrographic Department (Egyptian Navy), and estimated wave climatology along the Egyptian coast of the Mediterranean Sea during each month. Surges are a natural Phenomenon resulting from a complex interaction between the atmosphere, ocean and earth's surface (both above and below the sea surface). They occur in tropical and extra - tropical regions. Surges represent an ocean reaction to the large - scale impact of atmospheric pressure and wind. -lV- This study considered recent tidal data (1995 to 1998) to compare the present conditions with previous ones. Harmonic tidal constants calculated using 31 day, hourly records, and the daily mean surge calculated and discussed also. The monthly mean sea level correlated and compared with the means of the atmospheric pressure and wind speed. The thesis consists of 5 chapters and 2 appendices, the first chapter contains the general climatic conditions and the general characteristics of the Mediterranean Sea weather. The second chapter contains the climatic conditions along the Egyptian Coast of the Mediterranean Sea. The third chapter gives an idea about the methods of waves forecasting, the effect of depressions movement on the wind waves along the Egyptian coast of the Mediterranean Sea and the wave climatology at Alexandria, Abu-Quir, and Ras El-bar. Chapter four discussed the general statistics of surge at Alexandria coast as well as the percentage frequency at of positive and negative surge. Chapter five gives the conclusion of the study. Appendix A: contains basic wave characteristics. Appendix B: glves an idea about the pressure types and the depression tracks over the Egyptian coast of the Med. Sea -v- CONTENTS Page Declaration 11 Acknowledgments 111 Abstract IV Contents VI List of Figures x List of Tables xu" , List of Abbreviations XIV Chapter 1 Introduction 1. 1 Introduction. 1 1.2 Description of the Mediterranean Sea. 2 1.3 General climatic conditions. 5 1.3 .1 Effects of topography on the weather. 5 1.3.2 Barrier effects. 6 1.3 .3 Effects of vertical motion of air. 7 1.4 General characteristics of Mediterranean weather. 7 1.4. 1 Cool season. 9 1.4.2 Warm Season. 10 1.5 Air masses. 11 1.6 Fronts. 12 1.6.1 Cold fronts. 13 1.6.2 Warm fronts. 13 1.6.3 Occlusions fronts. 13 1.7 Previous studies. 13 1.7.1 Wave predication. 13 1.7.2 Surge predication. 16 1.8 Aim of study. 18 Chapter 2: Climatic Conditions along the Egyptian Coast of the . Mediterranean sea 2.1 Introduction 19 -VI- CONTENTS Page 2.2 Regional climatic conditions along the Egyptian coast of the 19 Mediterranean sea. 2.2.1 Introduction 19 2.2.2 Air temperature. 21 2.2.3 Atmospheric pressure. 22 2.2.4 Relative humidity. 22 2.2.5 Mean scalar wind speed 26 2.2.6 Wind directions. 32 2.2.7 Stormy days. 43 2.2.8 Rainfall. 43 2.2.9 Thunderstorms. 46 2.2.10 Sand rising and sandstorms. 46 2.2.11 Sea surface temperature and salinity at Alex. 49 Chapter 3 Waves forecasting along the Egyptian coast of the Mediterranean Sea. 3.l Introduction. 51 3.2 Wave forecasting by manual methods 52 3.2.1 The USA method for predicting sea waves 55 3.2.1.1 Waves estimation. 55 3.2.l.2 Wave dissipation. 57 3.2.l.3 Waves prediction. 58 3.3 Effect of the depression tracks on the wind waves. 63 3.3.1 Winter season. 63 3.3.2 Spring season. 63 3.3.3 Summer season. 64 3.3.4 Autumn season. 64 3.4 Wave r~cording instrumentation. 73 3.4.1 (S4DW) wave gauge. 73 3.4.l.1 (S4DW) information. 73 3.4.2 CAS directional wave recording system. 74 -vu- CONTENTS Page 3.4.3 Wave climatology. 76 3.4.3.1 Wave roses at Alexandria. 76 3.4.3.1.1 Winter season. 76 3.4.3.1.2 Spring season. 76 3.4.3.1.3 Summer season. 77 3.4.3.1.4 Autumn season. 77 3.4.3.2 Wave roses at Abu Quir and Ras EL Bar. 78 3.4.3.2.1 Winter season. 78 3.4.3.2.2 Spring season. 78 3.4.3.2.3 Summer season. 78 3.4.3.2.4 Autumn season. 79 Chapter 4: Surge at Alexandria coast. 4.1 Introduction. 89 4.2 Storm surge - Tide interaction. 92 4.3 Surge heights estimation 92 4.3.1 Elimination of the predicated astronomical tide method. 93 4.3.2 Low- pass filter method. 101 4.3.3 Xo- filter method 104 4.4 General statistics of surge at Alexandria. 105 4.4.1 Percentage frequency of positive and negative surge. 107 Chapter 5 Conclusion 5.1 Introduction. 111 5.2 Results. 111 5.3 Effect of the depression tracks on the wind waves 114 5.4 Wave climatology 115 5.4.1 Wave climatology at Alexandria 115 5.4.2 Wave climatology at Abu Quir and Ras EL Bar 116 5.5 Surge at Alexandria 118 -Vlll- CONTENTS Page References 120 Appendix A: Basic wave characteristics. Appendix B: The pressure types and the depression tracks over the Egyptian coast of the Med. Sea -lX- List of Figures No Fieures Paee 1. 1 The Mediterranean geographical features. 4 1.2 Main regional winds of the Mediterranean sea. 8 2-1 Egyptian weather station. 20 2-2 The monthly average temperature. 23 2-3 Monthly mean atmospheric pressure (Hpa) corrected to M. S.L. 24 2-4 The monthly mean relative humidity. 25 2-5 Surface wind speeds through out the period 61-90 at SaIl urn. 27 2-6 Surface wind speeds through out the period 61-90 at Mersa Matruh. 28 2-7 Surface wind speeds through out the period 61-90 at Alex. 29 2-8 Surface wind speeds through out the period 61-90 at Port Said. 30 2-9 Surface wind speeds through out the period 83 - 97 at El Arish.