پديد آورندگان :
فرهادي پور، سعيد پژوهشكده هواشناسي تهران , آزادي، مجيد پژوهشكده هواشناسي تهران , علي اكبري بيدختي، عباسعلي دانشگاه تهران - موسسه ژئوفيزيك - گروه فيزيك فضا , عليزاده چوبري، اميد دانشگاه تهران - موسسه ژئوفيزيك - گروه فيزيك فضا , سياري، حبيب الله دانشگاه عالي دفاع ملي
كليدواژه :
توفان گرد و خاك , داده هاي ماهواره , پريشيدگي تابش , مدل WRF-Chem
چكيده فارسي :
توفان‌هاي خاك كه امروزه در بسياري از مناطق ايران (به‌خصوص در غرب و جنوب غرب ايران) فراواني وقوع بالايي دارد، علاوه بر تأثير نامطلوب بر سلامتي بشر از طريق آلودگي هوا، تأثير قابل ملاحظه‌اي بر خواص نوري و توازن تابشي منطقه مي‌گذارد. در مطالعه حاضر اثرات تابشي ناشي از توفان خاك در بازه زماني 16 تا 21 ژوئن 2012 در منطقه غرب و جنوب غرب ايران با استفاده از مدل عددي WRF-Chem بررسي شده است. ابتدا عملكرد مدل با استفاده از داده هاي اندازه گيري ايستگاهي (ايستگاه هاي اندازه گيري آلودگي وابسته به سازمان محيط زيست و ايستگاه هاي AERONET) و داده هاي ماهوارهاي MODIS، OMI و CALIPSO مورد ارزيابي قرار گرفت. نتايج ارزيابي مدل نشان از برآورد بيشتر غلظت PM10 در ايستگاه اهواز و در اغلب موارد برآورد كمتر مقادير عمق نوري هواويزها (aerosol optical depth) در ايستگاه هاي AERONET دارد. با اين حال، عملكرد مدل در شبيه سازي روند تغييرات و ميزان گرد و خاك در طي توفان مذكور قابل قبول است، به طوري‌كه توزيع افقي و قائم گرد و خاك شبيه‌سازي‌شده توسط مدل و مشاهده شده توسط ماهواره الگوهاي تقريباً مشابه ي را نشان مي‌دهند. ذرات گرد و خاك در سقف جوّ و سطح زمين داراي اثرهاي سرمايشي، اما در ميانه جوّ داراي اثر گرمايشي هستند. ميانگين پريشيدگي تابش طول موج كوتاه توسط گرد و خاك در منطقه غرب و جنوب غرب ايران در بازه زماني 17 تا 20 ژوئن 2012 در سطح زمين، ميانه جوّ و سقف جوّ به‌ترتيب 7/27-، 1/79 و W m-2 5/47 برآورد شد.
چكيده لاتين :
Dust aerosols make a considerable contribution to the climate system through their radiative effects due to their abundance in the atmosphere. Recent observations suggest that over the past decade, dust events have become more frequent in many parts of Iran, especially in the west and southwest. Through their radiative forcing, dust aerosols have significant effects on the regional radiation budget of the atmosphere, while their adverse effects on human health have also raised serious concerns. The primary aim of the present study is to examine the radiation effects associated with a severe dust storm that occurred in west and southwest Iran on 16 to 21 June 2012. To this end, the Weather Research and Forecasting with Chemistry (WRF-Chem) model was used. Two simulations were conducted: a model setup that did not include dust aerosols, and the one that included dust aerosols and their feedback to the atmosphere. A two-way interactive nested domain (nesting ratio:1:3) simulations were performed using 98 Í 90 and 151 Í 139 horizontal grid points, respectively. In the vertical, 27 σ-levels were used. The grid spacing for the two domains were 45 and 15 km, respectively. Simulations ran from 16 to 22 June 2012, and the first 24 hours was considered as the spin-up time. Meteorological initial conditions were obtained from the Global Forecast System (GFS) data at 0.5˚Í 0.5˚ resolution. The performance of the model was evaluated using the available observed data, including PM10 observations in Ahwaz located in southwest Iran, available AErosol RObotic NETwork (AERONET) data in nearby areas, and aerosol products of the Moderate Resolution Imaging Spectroradiometer (MODIS), the Ozone Monitoring Instrument (OMI) and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) carried on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) spacecraft. Results indicate that PM10 concentration in Ahwaz is overestimated by the model, while simulated aerosol optical depth (AOD) is underestimated compared to the observed AERONET data. Relatively, good agreement is found between the model results and satellite products, and temporal evolution of the dust events is also well-simulated. Thus, generally, the performance of the model is acceptable for accurate simulation of the dust event. Our analysis indicated that radiative effects of dust particles cause cooling at the surface and top of the atmosphere, but warming in the middle of the troposphere. On average, perturbation of shortwave radiation by dust aerosols in the west, and southwest Iran is estimated to be -7.27, 1.79 and -5.47 W m-2 at the surface, in the middle and at the top of the atmosphere, respectively. Average perturbation of the longwave radiation by dust aerosols over the same region was estimated to be 2.2, -1.61 and 0.59 W m-2 at the surface, in the middle and at the top of the atmosphere, respectively. Thus, the net (shortwave + longwave) radiative effect of dust aerosols averaged in west and southwest Iran is found to be -5.07, 0.19 and -4.88 W m-2 at the surface, in the middle and at the top of the atmosphere, respectively.
