GAW Report No. 205 - IGAC Project

CHAPTER 3 - ASIAResearch has shown that temperature trend is not only significantly affected by globalclimate change, but also by local factors such as the Urban Heat Island (UHI). Recent work bySoltanzadeh et al. [2009] on the interaction between nocturnal down-slope winds and the urbanboundary layer is still at an early stage, but shows promise in shedding light on the role of thisinteraction in air pollution dispersion, especially at night time.Research projects on air quality of TehranExtensive systematic air pollution study campaigns of significance have not yet beenconducted in Tehran, although an international framework for an ‘Integrated Plan for air pollutionreduction’ is in place. This plan covers topics such as the role that public transport, fuel quality,traffic management, and public awareness play in air quality. Small scale research projects thathave looked at constructing emission inventory databases, characterizing air pollutants and limiteddispersion modelling with mesoscale models have been performed by various researchers fromuniversities and governmental agencies such as the Islamic Republic of Iran MeteorologicalOrganization (IRIMO). But a co-operative multi-agency research programme that simultaneouslymeasures variables such as emission factors, low level meteorology, and boundary layer height isdesperately needed to answer the many key scientific questions that remain.Various Departments at the University of Tehran are active in air quality research. Work iscurrently in progress to understand boundary-layer processes over the urban fabric of Tehran, forexample, in the Department of Geophysics. A long-term SODAR dataset is the main observationaltool here, and extensive postgraduate work is underway to validate mesoscale outputs with thisdata. Previously, theoretical work in this department concentrated on the climatology of mixed-layerevolution. The Department of Geography is mainly concerned with long-term spatial variation ofpollutants, and linkages with synoptic scale flow.Problems remainingIt is obvious that there is plenty of scope for air pollution research in Tehran. There are manyunanswered questions regarding mesoscale meteorology and its role in local and regionaladvection of pollutants. Basins exhibit peculiar vertical stability characteristics that directly controlvertical mixing of pollution, but this aspect has not been examined over Tehran. The twice dailyradiosonde from Mehrabad International Airport ascends too rapidly through the first few hundredmeters above the ground to provide comprehensive information about stability. So there is very littleinformation on the formation and destruction of the nocturnal inversion layer or its seasonalvariation, or on the mixed-layer height evolution throughout the day.Peer-reviewed published work is badly needed examining long-term pollutant trends afterstatistically removing the meteorological signal. Given the influence of the surrounding topographyon Tehran’s meteorology, however, this might not be as vital as it is for cities on less complexterrain. Certainly the AQCC dataset makes a comprehensive overview of trends possible.In view of the significant amount of air and pollution that can be injected into the uppertroposphere via the daytime up-slope flows and transported away by the free atmosphere, it is alsovital to research and understand the role this process plays in Tehran’s air quality.ReferencesADB (2002). RETA Project on “ Study on Air Quality in Jakarta: Future Trends, Health Impacts,Economic Value, and Policy Options”. Asian Development Bank.Asadollah-Fardi G., Air quality management in Tehran. Unpublished Report.Asgari, A., Rahimzadeh, F., Mohammadian, N. and Fattahi, E. (2008). Trend Analysis of ExtremePrecipitation Indices Over Iran. Iran-Water Resources Research. 3, 42-55Asian Development Bank, Philippines: Metro Manila Air Quality Improvement Sector DevelopmentPlan, ADB Completion Report, Project No. 30480, 2008131