ارزيابي و مقايسه روش‌هاي تحليل و پيش‌بيني كشند در نرم‌‌افزار مايك‌21

Evaluation and comparison of tidal analysis and predicting methods of Mike 21 software

در اين تحقيق سعي شده است با استفاده از داده­هاي كوتاه‌مدت و ابزارهاي تحليل و پيش­بيني كشند نرم‌افزار مايك‌21، كاربرد درست ابزارهاي تحليل و توليد داده­هاي كشند ارتفاعي براي استفاده در داده­هاي مرزِ باز ( open boundary ) مدل­هاي هيدروديناميكي معرفي شود. مايك‌21 نرم‌افزاري قدرتمند در زمينه شبيه‌سازي پارامترهاي اقيانوسي و دريايي است. از اطلاعات كشندي براي توليد داده­هاي مرزِ باز شبيه‌سازي­هاي دوبعدي و سه‌بعدي مدل­هاي هيدروديناميكي استفاده مي­شود. دقت نتايج شبيه‌سازي جريان­هاي كشندي و كشند ارتفاعي، موج، انتقال رسوب و ساير پارامترهاي دريايي، وابستگي تام به دقت داده­هاي مرزِ باز ورودي كشند در مدل هيدروديناميكي دارد. اين تحقيق، بهترين روش تحليل و توليد داده­هاي كشندي را با استفاده از ابزارهاي تحليل و پيش­بيني كشند در نرم‌افزار مايك معرفي مي­كند. در اين مقاله با استفاده از ابزارهاي تحليل، مهم­ترين اطلاعات ساعتي يك‌ساله كشندي ايستگاه­هاي دائمي بنادر چابهار، شهيد‌رجايي و بوشهر تجزيه و تحليل مي­شوند. اين تحليل­ها در دوره­هاي بلندمدت يك‌ساله، سي‌روزه، پانزده‌روزه و ده‌روزه با استفاده از روش كانادايي گودين‌- فرمن(Godin-Forman) و روش آدميرالتي (Admiralty) انجام مي­شوند. سپس مؤلفه­هاي حاصل از تحليل كشند با مقادير متناظرشان از مدل كشندي TMD مقايسه و ضرورت استفاده از تحليل داده­هاي كوتاه‌مدت براي اصلاح مقادير مدل كشندي در مناطق خاص بررسي مي­شود. در ادامه، با استفاده از ابزار كشند موجود در نرم‌افزار، مثال­هايي از داده­هاي ساعتي يك‌ساله كشندي ايستگاه­هاي دائمي مطرح و درباره روش­هاي توليد دقيق­تر داده­هاي كشندي از مشاهدات بلند‌مدت وكوتاه‌مدت براي استفاده در شرايط مرزِ باز مدل­هاي هيدروديناميكي بحث خواهد شد. در‌نهايت، نتايج ارائه شده از لحاظ آماري، ارزيابي و ابزارهاي مناسب انجام تحليل و پيش‌بيني داده­هاي كشندي در دوره­هاي مختلف معرفي خواهد شد.

The present article addresses a new approach form using tidal analysis of long and short observations of tidal heights by tidal tools of Mike 21 software. Predicted or observed tides must be available as open boundaries in a hydrodynamic model to simulate tidal currents. Mike 21 is a powerful software in simulating of marine and oceanic parameters. Hydrodynamic models use tidal data as a main input in the open boundaries of 2D/3D simulation. The accuracy of the simulation results from tides and tidal currents as well as sediment transportation and other related marine parameters, is quite dependent on accurate input data in the open boundaries of the hydrodynamic model. Large and meso-scale simulations usually use sophisticated global tidal models. These tidal models are prepared by assimilating of satellite altimeter data and tide gage data. The accuracy of such a tidal input seems to be quite sufficient. In shallower part of ocean, like estuaries and coastal areas, these data are not so accurate; therefore direct tide observations are important. On the other hand, long-term tide observations are limited due to technical and economical constraints. In this study, the appropriate solution to tidal analysis and predictions was introduced in the Mike 21 software to produce acceptable and accurate tidal height data. Mike 21 is provided with two different tidal analysis and prediction modules. The IOS and Admiralty methods of tidal analysis and prediction are known for the corresponding high quality functions. Using the software, the tidal analysis of sample data was discussed in order to produce the accurate tidal data. In this article, hourly tidal observations for a year which belonged to three stations in the Oman Sea and Persian Gulf were analyzed. All tidal analyses were performed for one year, 30, 15 and 10 days periods using Canadian IOS and Admiralty method software. The predicted tidal data were compared with respect to observed data for evaluating of computations. Residuals normally will describe such discrepancies, if there are no abnormal fluctuations of tides. These abnormal inconsistencies might be produced by storm surges and other non-tidal effects. The presented results were statistically analyzed. Two different statistical indices, Root Mean Square Error and Reduction in Variance, were used to evaluate predicted tide data. Consequently, the tool for appropriate analysis and predicting of tidal data of the different periods was introduced. It is shown that for long term tide observations, the IOS method is the proper solution for tidal analysis and prediction, while the Admiralty method is fitted for short term analysis and prediction of tides.