Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

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Climate Change 2007: The Physical Science Basis.

[i] An inventory of air pollutant emissions in Asia in the year 2000 is developed to support atmospheric modeling and analysis of observations taken during the TRACE-P experiment funded by the National Aeronautics and Space Administration (NASA) and the ACE-Asia experiment funded by the National Science Foundation (NSF) and the National Oceanic and Atmospheric Administration (NOAA). Emissions are estimated for all major anthropogenic sources, including biomass burning, in 64 regions of Asia. We estimate total Asian emissions as follows: 34.3 Tg SO 2 , 26.8 Tg NO x , 9870 Tg CO 2 , 279 Tg CO, 107 Tg CH 4 , 52.2 Tg NMVOC, 2.54 Tg black carbon (BC), 10.4 Tg organic carbon (OC), and 27.5 Tg NH 3 . In addition, NMVOC are speciated into 19 subcategories according to functional groups and reactivity. Thus we are able to identify the major source regions and types for many of the significant gaseous and particle emissions that influence pollutant concentrations in the vicinity of the TRACE-P and ACE-Asia field measurements. Emissions in China dominate the signature of pollutant concentrations in this region, so special emphasis has been placed on the development of emission estimates for China. China's emissions are determined to be as follows: 20.4 Tg SO 2 , 11.4 Tg NO x , 3820 Tg CO 2 , 116 Tg CO, 38.4 Tg CH 4 , 17.4 Tg NMVOC, 1.05 Tg BC, 3.4 Tg OC, and 13.6 Tg NH 3 . Emissions are gridded at a variety of spatial resolutions from 1° × 1° to 30 s x 30 s, using the exact locations of large point sources and surrogate GIS distributions of urban and rural population, road networks, landcover, ship lanes, etc. The gridded emission estimates have been used as inputs to atmospheric simulation models and have proven to be generally robust in comparison with field observations, though there is reason to think that emissions of CO and possibly BC may be underestimated. Monthly emission estimates for China are developed for each species to aid TRACE-P and ACE-Asia data interpretation. During the observation period of March/ April, emissions are roughly at their average values (one twelfth of annual). Uncertainties in the emission estimates, measured as 95% confidence intervals, range from a low of ±16% for SO 2 to a high of ±450% for OC.

An inventory of gaseous and primary aerosol emissions in Asia in the year 2000 : NASA global tropospheric experiment transport and chemical evolution over the pacific (TRACE-P): Measurements and analysis (TRACEP1)

Ozone pollution in China: A review of concentrations, meteorological influences, chemical precursors, and effects

http://ira.lib.polyu.edu.hk/bitstream/10397/66328/1/Chen_Review_Biomass_Burning.pdf

A review of biomass burning: Emissions and impacts on air quality, health and climate in China

Air quality is concerned with pollutants in both the gas phase and solid or liquid phases. The latter are referred to as aerosols, which are multifaceted agents affecting air quality, weather and climate through many mechanisms. Unlike gas pollutants, aerosols interact strongly with meteorological variables with the strongest interactions taking place in the planetary boundary layer (PBL). The PBL hosting the bulk of aerosols in the lower atmosphere is affected by aerosol radiative effects. Both aerosol scattering and absorption reduce the amount of solar radiation reaching the ground and thus reduce the sensible heat fluxes that drive the diurnal evolution of the PBL. Moreover, aerosols can increase atmospheric stability by inducing a temperature inversion as a result of both scattering and absorption of solar radiation, which suppresses dispersion of pollutants and leads to further increases in aerosol concentration in the lower PBL. Such positive feedback is especially strong during severe pollution events. Knowledge of the PBL is thus crucial for understanding the interactions between air pollution and meteorology. A key question is how the diurnal evolution of the PBL interacts with aerosols, especially in vertical directions, and affects air quality. We review the major advances in aerosol measurements, PBL processes and their interactions with each other through complex feedback mechanisms, and highlight the priorities for future studies.

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Aerosol and boundary-layer interactions and impact on air quality

[1] In this paper, the three-dimensional distribution of air pollutants in the Beijing region using aircraft measurements is reported, and Mountain Chimney Effect (MCE) on the distribution of air pollutants in this region is studied. A remarkable two-pollution-layer structure was observed by aircraft measurement in Beijing on 18 August 2007. Gaseous and particle pollutants were well mixed with high concentrations in the planetary boundary layer. There was an elevated pollution layer (EPL) at the altitude of 2500–3500 m, and the concentrations of pollutants were high and comparable with that in the planetary boundary layer. Analysis of aircraft measurement indicates that pollutants in the two pollution layers originated from the same source. On the basis of analysis of the Weather Research and Forecasting (WRF)-TRACER model and wind profile data, the formation of EPL is discussed. The wind flow of Beijing region was dominated by mountain-valley breeze, which has MCE on the distribution of pollutants in this region. Air pollutants were injected from the planetary boundary layer into the free troposphere due to this effect. These pollutants were subsequently transported back over the city by the elevated northerly wind. Thus the structure of two pollution layers over Beijing is formed. Modeling results show that the persistence of a polluted layer over the boundary layer from the previous day has significant contribution to the surface concentrations of pollutants. When the mixing depth increases, the elevated pollutants are recaptured into planetary boundary layer and mixed downward. The rapid increase of surface concentrations of pollutants may be attributed to the vertical down-mixing of pollutants.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2008JD010610

Aircraft study of Mountain Chimney Effect of Beijing, China

Vertical distributions of aerosols under different weather conditions: Analysis of in-situ aircraft measurements in Beijing, China

A set of 152 vertical profiles of aerosol number concentration and size distribution with diameter ranging from 0.12 to 3.0 μ m observed by the airborne optical spectrometer probe in Beijing, China, between February 2005 and September 2006 is analysed and discussed. The statistic of aerosol number concentration ( N a ) reveals a high aerosol number density in this region with average surface level number concentration ( N 0 ) of about 6600 cm -3 (0.12–3.0 μ m). The average vertical profile of N a approximately satisfies an exponential decline function with a scale height of 1419 m. The N a profiles are influenced by the structures of planetary boundary layer (PBL) significantly and two typical types of N a profile under different conditions of PBL are presented and parametrized in this study. The observations of aerosol size distribution show that, in most cases the aerosol size distributions are not very sensitive to altitude, with effective radii ranging from 0.16 to 0.28 μ m. Comparison between aircraft-derived aerosol optical depth (AOD) and Moderate Resolution Imaging Spectroradiometer-derived AOD shows good agreement. The Mie model calculations suggest that the surface level number concentration, the PBL height and the structure of PBL can influence the AOD significantly. DOI: 10.1111/j.1600-0889.2009.00440.x

Xincheng Ma

Papers

Aircraft study of Mountain Chimney Effect of Beijing, China

Vertical distributions of aerosols under different weather conditions: Analysis of in-situ aircraft measurements in Beijing, China

Aircraft study of aerosol vertical distributions over Beijing and their optical properties

Aircraft measurements of O3, NOx, CO, VOCs, and SO2 in the Yangtze River Delta region

Impact of aerosol particles on cloud formation: Aircraft measurements in China