شبيه‌سازي هبوب منطقه تهران با مدل WRF-chemو مقايسه آن با تصاوير رادار

Simulation of Haboob over Tehran region by WRF-chem and Comparison of Results with Radar Images

هبوب يكي از انواع طوفان‌هاي گرد و خاك است كه جلوي سلول‌هاي همرفتي تشكيل مي‌شود و همچون ديوار بلندي از گرد و خاك به نظر مي‌رسد. ارتفاع اين نوع از طوفان گرد و خاك به چند كيلومتر، پهناي آن چند ده كيلومتر و طول آن به چند صد كيلومتر مي‌رسد. با توجه به اينكه اين رخداد براي اولين دفعه در تاريخ 12 خرداد 1393در تهران ديده شد بررسي و شبيه‌سازي اين رخداد و در صورت امكان پيش‌بيني آن امري لازم به نظر مي‌رسد. در اين پژوهش با مدل WRF-chem اقدام به شبيه‌سازي اين رخداد خواهد شد. براي اين منظور از طرحواره Lin براي خرد فيزيك، طرحواره Grell-Freitas براي همرفت و براي لايه مرزي، طرحواره MYJ انتخاب شد كه با كاربست آنها در مدل، نتايج مناسبي گرفته شد. در اين پژوهش ضمن تعريف و شبيه‌سازي هبوب، با توجه به ساختار آن از تصاوير بازتاب تراكم ذرات (dBZ) كه يكي از خروجي‌هاي رادار است براي راستي¬آزمايي نتايج اجراي مدل استفاده خواهد شد.

“Haboob” is one of the various types of dust and sand storms which forms in front of convective cells as a huge wall of dust and sand. The height of this type of dust storm reaches a few kilometers, its horizontal dimension is over a few tens to few hundreds of kilometers. It was the first occurrence of Haboob On June 2, 2014 in Tehran, so it is necessary to pay attention and do research about its structure and simulation.In this research we proceed to simulate this phenomenon via WRF-chem model as a numerical weather and research for forecast purposes. Therefore, Lin schema to micro physics, Grell-Freitas to convection, and MYJ schema to boundary layer were selected for the numerical simulation. With use of their applications, good conclusions were achieved. At first, by defining Haboob, we will examine the synoptic, dynamic and thermodynamic conditions governing the atmosphere while Haboob occurred. Then by running the model, we will compare the output of these simulations with observational data such as radar, recorded data of pollution and meteorological stations for verification and assessment of our simulation. One of the reasonable verification methods respect to radar structure, is the comparison of output ofparticles density reflection “dBZ” between model output and radar reflection images caused by concentrated suspended particles. The comparison between simulation on second domain of nested grid of the model output and radar images shows satisfaction results. The comparison indicate that the model is able to simulate high density zones of suspended particles in Haboob of Tehran and domain of Haboob occurrence