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Archive of SID MODELLING OF LAST RECENT TROPICAL STORMS IN THE

Arash Bakhtiari1, Mohammad Reza Allahyar2, Morteza Jedari Attari 3, Syed Abbas Haghshenas4, Mohammad Bagheri5 Shima Droudi6

1) Project engineer, Middle East Water and Environment Co., Tehran, , Email: [email protected] 2) Iranian Ports and Maritime Organization, Tehran, Iran, Email: [email protected] 3) Project engineer, Middle East Water and Environment Co., Tehran, Iran, Email: [email protected] 4) Assistant Professor, Institute of Geophysics, University of Tehran, Iran, Email: [email protected] 5) Iranian Ports and Maritime Organization, Tehran, Iran, Email: [email protected] 6) Project engineer, Middle East Water and Environment Co., Tehran, Iran, Email: [email protected]

1. INTRODUCTION 3. MEASURED DATA The Sea waters and coastline is subjected to An invaluable data set recorded during the first phase tropical (TC) influence on an infrequent basis; of Monitoring and Modeling Study of Iranian Coasts (by however, these cyclones can generate relatively large sea PMO) includes wave characteristics measurements in 30 states. At many locations along this coastline, m depth at a location outside Bay. particularly in the southern and northern central and Measurements at this location cover the period from eastern parts or areas of the coast, tropical September 2006 until early June 2007 immediately after waves are the dominant coastal design wave condition the Cyclone Gonu event. The oscillating ocean currents as the wave heights can exceed those generated from have been captured in this data set. Moreover, wind and other meteorological phenomena, such as the wave measurements were carried out offshore of and the northerly Shamals. Chabahar in 20 m water depth from 1998, and the Thereupon, a better understanding of tropical effects of a cyclones that occurred from this were cyclones (TC) and hurricane hazards in this area will detected. A synoptic wind station in Chabahar area, also help to make a more informed decision on your risk and recorded winds characteristics. what actions to take. In this study, as part of the sixth phase of Monitoring 4. HISTORICAL TROPICAL CYCLONES and Modeling Study of Iranian Coasts, the assessment of For this project, we used the International Best-Track risks along the Iranian coasts of Archive for Climate Stewardship (IBTrACS) global Arabian Sea and have been studied. tropical cyclone database to represent historical TC The study aims to improve the understanding of activity [2]. The IBTrACS database collates information hazards posed by tropical cyclones to ports and harbors on TC tracks and intensity from reporting agencies of the coastline. The resulting risk information around the globe and provides a single authoritative will allow beneficiaries and the government to better database that can be used for climate analysis. Figure 2 integrate risk considerations into infrastructure shows the tracks contained within the IBTrACS dataset development and ex-ante disaster planning. for the period 1974-2014 which are within 500 km of the Eastern End of the Oman Sea Coastline. 2. STUDY AREA In addition to this set of data, TC tracks of India The regions to be studied in this study are coastal Meteorological Department (IMD) and re-analysed wind areas of Sistan & Baluchesan province. This coastline data extracted from ECMWF (ERA-Interim) data centre which is also called Makran Coasts is about 350 km were also considered and analysed. stretching from Bay at the border with Pakistan to Rapch Estuary at the border with Hormozgan Province (Figure 1).

Figure 1. Study area Figure 2. TC Tracks within 500 km of the Eastern End of the Oman Sea Coastline www.SID.ir

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Bouy Chabahr (Wind Speed) [m/s] 5. NUMERICAL MODELING Wind Speed (Holland) [m/s] Archive ofThe SIDMIKE21-SW and Cyclone Wind Generation 16 14

(CWG) package by DHI were used in the present work. 12

Finding the most appropriate model configuration that 10

can properly simulate large scale oceanic processes was 8

6 a matter of trial and error. Applying various domains (m/s) WindSpeed showed that obtaining reasonable results requires 4 adopting a domain far larger than the study area 2 00:00 00:00 00:00 00:00 00:00 00:00 00:00 00:00 boundaries. The mesh size, and models parameters also 2010-05-31 06-01 06-02 06-03 06-04 06-05 06-06 06-07

Chabahar Synoptic (Wind Speed) [m/s] play significant role in the validity of the model results. Wind Speed (Young & Sobey) [m/s] Figure 3 shows the final selected model domain which 12

extends to the southern hemisphere. 10

8

6 Wind Speed (m/s) WindSpeed 4

2

0 00:00 00:00 00:00 00:00 00:00 00:00 00:00 00:00 2007-06-01 06-02 06-03 06-04 06-05 06-06 06-07 06-08 Figure 4. Comparisons between wind speed of Chabahr Buoy data (black points) and Wind Generation model results (blue solid line) during cyclones Phet (above) and Gonu (below). Measured at AW2 [m] IBTrACS [m] IMD [m] 6.0

Figure 3. Computational domain 4.0

4. SAMPLE RESULTS and DISCUSSION 2.0

A detailed investigation of wind and waves 0.0

Significant Wave Height (m) 00:00 00:00 00:00 00:00 00:00 generated by tropical cyclones has been carried out for 2007-06-03 06-04 06-05 06-06 06-07 the Oman Sea coastline of Iran. Model setup for CWG model is selected by using three major tropical storms 20

happened in the Oman Sea and the Indian Ocean since 15 2007 including GoNu, Phet, and Niloufar cyclones. Generated winds were calibrated against measured wind 10

data (Figure 4). Regenerated wind field for all storm 5 (2007) was introduced to MIKE21-SW model and wave Peak Wave Period (s) 0 00:00 00:00 00:00 00:00 00:00 parameters were hindcasted at Chabahar measurements 2007-06-03 06-04 06-05 06-06 06-07 over Iranian Coastline of the Oman Sea. Figure 5 depicted comparison of modelled and measured wave

characteristics of Gonu Cyclone. Regenerated waves are 300 in reasonable agreement with observations in height and direction, but more attention should be paid for 200

improving the accuracy of simulated wave periods. 100 The following conclusions and recommendations Mean Wave Direction (s) 0 were developed based on the analyses and modeling 00:00 00:00 00:00 00:00 00:00 performed in this study: 2007-06-03 06-04 06-05 06-06 06-07 Figure 5. Comparisons between wave characteristics of 1. Based on measured wind data, IBTrACS data AW2 data (black points) and SW model results (solid are the most appropriate data set to regenerating lines) during cyclone Gonu for two wind track sources. of recorded TC in this study area. 2. Regenerated wind field of each cyclone were 5. ACKNOWLEDGEMENTS slightly under estimated rather than measured The present work has been supported by the Port and data. maritime Organization (PMO). 3. Wave height and direction were reasonably compatible with recorded data in the study area. 6. REFERENCES 4. Wave periods need to be investigated more [1] Jahad Water and Energy Research Company (JWERC): carefully in order to achieve an adequate Study reports of “Monitoring and Modelling Studies of Parts accuracy. of Sistan, Balouchestan and Boushehr Provinces”, Ports and Maritime Organization (PMO), 2008. 5. Reanalysis wind field data such as ERA-Interim [1] Knapp, K. R., M. C. Kruk, D. H. Levinson, H. J. Diamond, (obtained from ECMWF) are not appropriate for and C. J. Neumann, 2010: The International Best Track wind field of cyclonic winds. Archive for Climate Stewardship (IBTrACS): Unifying tropical cyclone best track data. Bulletin of the American Meteorological Society, 91, 363-376. www.SID.ir

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