In this study, the analysis of the extreme sea level was carried out by using 10 years (2007–2016) of hourly tide gauge data of Karachi port station along the Pakistan coast. Observations revealed that the magnitudes of the tides usually exceeded the storm surges at this station. The main observation for this duration and the subsequent analysis showed that in June 2007 a tropical Cyclone “Yemyin” hit the Pakistan coast. The joint probability method (JPM) and the annual maximum method (AMM) were used for statistical analysis to find out the return periods of different extreme sea levels. According to the achieved results, the AMM and JPM methods erre compatible with each other for the Karachi coast and remained well within the range of 95% confidence. For the JPM method, the highest astronomical tide (HAT) of the Karachi coast was considered as the threshold and the sea levels above it were considered extreme sea levels. The 10 annual observed sea level maxima, in the recent past, showed an increasing trend for extreme sea levels. In the study period, the increment rates of 3.6 mm/year and 2.1 mm/year were observed for mean sea level and extreme sea level, respectively, along the Karachi coast. Tidal analysis, for the Karachi tide gauge data, showed less dependency of the extreme sea levels on the non-tidal residuals. By applying the Merrifield criteria of mean annual maximum water level ratio, it was found that the Karachi coast was tidally dominated and the non-tidal residual contribution was just 10%. The examination of the highest water level event (13 June 2014) during the study period, further favored the tidal dominance as compared to the non-tidal component along the Karachi coast.

中文翻译：

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复杂的极端海平面预测分析：卡拉奇海岸案例研究

本研究利用巴基斯坦沿海卡拉奇港站10年（2007-2016）逐时验潮数据进行极端海平面分析。观测显示，该站潮汐的强度通常超过风暴潮。这段时间的主要观测和随后的分析表明，2007年6月，热带气旋“叶敏”袭击了巴基斯坦海岸。采用联合概率法（JPM）和年最大法（AMM）进行统计分析，找出不同极端海平面的重现期。根据所取得的结果，AMM 和 JPM 方法对于卡拉奇海岸来说相互兼容，并且保持在 95% 置信度的范围内。对于JPM方法，卡拉奇海岸的最高天文潮汐（HAT）被视为阈值，其之上的海平面被视为极端海平面。最近10年观测到的海平面最大值显示极端海平面呈上升趋势。研究期间，卡拉奇海岸平均海平面和极端海平面的增长率分别为3.6毫米/年和2.1毫米/年。卡拉奇验潮仪数据的潮汐分析表明，极端海平面对非潮汐残差的依赖性较小。应用Merrifield年平均最高水位比准则发现，卡拉奇海岸以潮汐为主，非潮汐剩余贡献仅为10%。对研究期间最高水位事件（2014 年 6 月 13 日）的检查进一步表明，与卡拉奇海岸的非潮汐成分相比，潮汐占主导地位。