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Critical emissions from the largest on-road transport network in South Asia
Get PDFOne of the major requirements of air quality management for a particular region or country is to understand the sources of emissions, particularly those from the dominant sectors. The on-road transport sector is one of the most important sources of pollutant emissions, as it is directly linked to economic growth, and the current study focuses on India, a nation that is currently experiencing very rapid development. In view of this, the present work develops an inventory of on-road vehicular emissions at 0.5° × 0.5° resolution (approx. 55 km) for a region in India, where a technologically-based dynamic emissions factor method has been used to for the last 20 years. This new inventory can not only provide improved estimates of emissions in recent years but also highlight the relative contribution of various vehicles, based on age, to the total emissions produced by the transport sector. In addition, inventories of the major air pollutants for on-road vehicles in India are developed for the base year of 2009 for the first time in this work. The total emissions from the transport sector are estimated to be 5.4 Tg/yr for NOx, 10.2 Tg for CO, 693.3 Gg/yr for PM and 5.54 Tg/yr for VOC, 240,000 kilometers of national, state and major highways in India are used to achieve a better spatial allocation of gridded on-road emissions, along with a vehicular density map in a GIS environment. The emissions data presented in this work will not only help in improving the simulated distribution of air pollutants in chemical transport models, but can also be used for air quality management in planning related mitigation strategie
Physical properties of the arctic summer aerosol particles in relation to sources at Ny-Alesund, Svalbard
Get PDFMeasurements of the number concentration and size distribution of aerosol particles in the size range of 0.5-20 μm diameter were made with an aerodynamic particle sizer at an Arctic site at Ny-Alesund, Svalbard in August-September 2007 during the International Polar Year 2007-2008. Data are analyzed to study the aerosol number concentration-wind speed relationships. The sea-salt particles of marine origin generated within the Arctic circle are identified as the main source of the Arctic summer aerosols. Total number concentration of aerosol particles increases with increase in wind speed, the increase being more when winds from open leads over the oceanic sector are reaching the station as compared to when winds from pack ice in other directions are reaching the station. The larger increase with winds from the oceanic sector is attributed to the enhanced bubble-breaking activity and increased entrainment of dimethyl sulphide particles at the sea surface. Although, the increase in total aerosol number concentration associated with the winds from the oceanic sector is spread over the whole range of particle sizes, the increase in coarse mode particles is more prominent than that in the accumulation mode particles. The age of airmass over pack ice is also an important factor to determine the aerosol concentration over the Arctic region. The process of rainout/washout of the aerosol particles due to drizzle/snowfall is an effective sink mechanism in the Arctic environment. The aerosol particle concentration starts decreasing within a few minutes from the start of these events but requires a few hours to restore to the normal background aerosol level after the end of event
Prediction and monitoring of monsoon intraseasonal oscillations over Indian monsoon region in an ensemble prediction system using CFSv2
No full textAn ensemble prediction system (EPS) is devised for the extended range prediction (ERP) of monsoon intraseasonal oscillations (MISO) of Indian summer monsoon (ISM) using National Centers for Environmental Prediction Climate Forecast System model version 2 at T126 horizontal resolution. The EPS is formulated by generating 11 member ensembles through the perturbation of atmospheric initial conditions. The hindcast experiments were conducted at every 5-day interval for 45 days lead time starting from 16th May to 28th September during 2001-2012. The general simulation of ISM characteristics and the ERP skill of the proposed EPS at pentad mean scale are evaluated in the present study. Though the EPS underestimates both the mean and variability of ISM rainfall, it simulates the northward propagation of MISO reasonably well. It is found that the signal-to-noise ratio of the forecasted rainfall becomes unity by about 18 days. The potential predictability error of the forecasted rainfall saturates by about 25 days. Though useful deterministic forecasts could be generated up to 2nd pentad lead, significant correlations are found even up to 4th pentad lead. The skill in predicting large-scale MISO, which is assessed by comparing the predicted and observed MISO indices, is found to be ~17 days. It is noted that the prediction skill of actual rainfall is closely related to the prediction of large-scale MISO amplitude as well as the initial conditions related to the different phases of MISO. An analysis of categorical prediction skills reveals that break is more skillfully predicted, followed by active and then normal. The categorical probability skill scores suggest that useful probabilistic forecasts could be generated even up to 4th pentad lead
Study of surface morphology, elemental composition and origin of atmospheric aerosols (PM2.5 and PM10) over Agra, India
Get PDFIn situ measurements of PM (PM2.5 and PM10) particles were carried out using a medium volume air sampler (offline) and particle number concentrations of PM were measured by a Grimm aerosol spectrophotometer (online) during the study period of 2010�2011. The morphology and elemental composition analyses of PM were performed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS), respectively. The average mass concentrations of PM2.5 and PM10 were 97.2 and 242.6 µg/m3 at roadside (RD) and 121.2 and 230.5 µg/m3 at a semirural (SR) site, respectively. These concentrations were substantially higher than the NAAQS, WHO and USEPA standards. The highest mass and number concentrations of PM2.5 and PM10 were observed during winter, followed by those during the post-monsoon period and summer, with the lowest in the monsoon period. SEM and EDS analysis of PM indicated the presence of soot, mineral, tarballs, fly ash, aluminosilicates/silica, fluorine, carbon rich, and Cl-Na rich particles. Of these particles, soot, tarballs, and F-C rich particles dominate in PM2.5, whereas mineral, aluminosilicates, and Cl-Na rich particles dominate in PM10. The morphology and elemental composition of the particles varied over the seasons due to atmospheric processing. The highest carbon concentration (56) was observed in PM2.5 during summer at the RD, while in the monsoon, post-monsoon period and winter the carbon concentration was ~9 lower at the RD as compared to the SR. However, the concentration of carbon in PM10 was ~38 higher at the RD as compared to SR during both summer and winter. Air mass backward trajectory cluster analysis was performed, and the results indicate that the aerosol loadings over Agra are mainly transported from the Middle East and Arabian Sea during the summer and monsoon period, while during the pre-monsoon period and winter the aerosol loadings came from the northern region, and were due to the burning of biomass and coal, as well as other local activities
Indian Ocean and monsoon coupled interactions in a warming environment
No full textSeveral studies have drawn attention to the steady warming of the equatorial and tropical Indian Ocean (IO) sea surface temperature (SST) observed during recent decades. An intriguing aspect of the IO SST warming trend is that it is has been accompanied by a pronounced weakening of the large-scale boreal summer monsoon circulation. Based on a detailed diagnostic analysis of observed datasets, reanalysis products and IPCC AR4 coupled model output, this study examines how the observed changes in the summer monsoon circulation could have contributed to this SST warming trend. The present results reveal that the weakening trend of the summer monsoon cross-equatorial flow has favored a reorientation of surface westerlies towards the equatorial IO during recent decades, relative to summer monsoons of earlier decades, which were dominated by stronger cross-equatorial flow. Our analysis suggests that the weakening of the summer monsoon cross-equatorial flow has in turn significantly accelerated the SST warming in the central equatorial IO. While the trend in the equatorial westerlies has promoted downwelling and thermocline deepening in the eastern equatorial IO, the central equatorial IO warming is attributed to reduced upwelling in response to a weakening trend of the wind-stress curl. The observed trends in Indian monsoon rainfall and the near-equatorial SST warming are shown to be closely related to variations in the meridional gradient of the monsoon zonal winds. An examination of the twentieth century simulations from 22 IPCC AR4 models, suggests that some models capture the recent equatorial IO warming associated with the weakened summer monsoon circulation reasonably well. The individual member models, however, exhibit significant inter-model variations in representing the observed response of the IO and monsoon coupled system
Characterization of carbonaceous aerosols over the urban tropical location and a new approach to evaluate their climatic importance
No full textIncreasing emissions from fossil-fuel, biomass burning, land use changes and industrial growth have led to rapid increase in the atmospheric concentrations of carbonaceous species over many cities in India. The present paper deals with the results obtained from year long (2012-13) observations conducted at a tropical urban location, Pune in southwestern India on Organic and Elemental Carbon as well as Black Carbon; using the Sunset OCEC Analyzer and Aethalometer, respectively. The average mass concentrations of OC and EC were in the order of winter>post-monsoon>summer>monsoon. Mean annual OC/EC ratio was found to be 2.4±1.1 during the study period, suggesting the presence of secondary organic carbon (SOC). Estimated SOC was found to form 47 of OC mass concentration. OC and EC were also significantly well correlated (r=0.95, p<0.0001) to each other, indicating towards common combustion sources. The primary organic carbon (POC) dominated over SOC and EC in post-monsoon and winter seasons indicating impact of anthropogenic burning activity, enhanced by prevailing meteorological conditions as well as that of long range transport. Mean annual POC+EC/TC ratio was 0.69 indicating that more than 2/3 of TC is formed from combustion sources. Thermally derived EC and optically derived BC correlated very well (r=0.98, p<0.0001). A new concept e.g. Effective carbon ratio (ECR) is suggested to better assess the scattering/absorptive nature and probable source identification of carbonaceous aerosols in place of conventional OC/EC ratio
Extended range prediction of active-break spells of Indian summer monsoon rainfall using an ensemble prediction system in NCEP Climate Forecast System
No full textThis study analyses skill of an extended range prediction system to forecast Indian Summer Monsoon Rainfall (ISMR) 3-4 pentads in advance. A series of 45-d forecast integrations starting from 1 May to 29 September at 5-d interval for 7 years from 2001 to 2007 are performed with an ensemble prediction system (EPS) in NCEP Climate Forecast System Version 1 (CFSV1) model. The sensitivity experiments with different amount of perturbation suggest that full tendency perturbation experiment on all basic variables including humidity at all vertical level shows higher dispersion among forecast than other experiments. Spread-error relationship shows that the present EPS system is under-dispersive. The lower bound of predictability is about 10-12 d and upper bound of predictability is found to be 20-25 d for zonal wind at 850 and 200 hPa. The signal-to-noise ratio (SNR) of precipitation (500 hPa geopotential height) reveals that the predictability limit is about 15(18) d over Indian monsoon region. The monsoon zone area averaged precipitation forecasts averaged over 5-d period (pentads) up to 4 pentad lead time are also evaluated and compared with observation. The anomaly correlation coefficients (ACC) reaches zero after pentad 3 (pentad 5) lead for precipitation (dynamical variables). A probabilistic approach is developed from the EPS for extended range forecast applications. The relative operating characteristic (ROC) curves for three categories of precipitation shows that the prediction skill for active and break is slightly higher compared to that of normal category and skillful probabilistic forecasts can be generated for precipitation even beyond pentad 4 lead
Summer monsoon circulation and precipitation over the tropical Indian Ocean during ENSO in the NCEP climate forecast system
No full textThis study investigates the El Niño Southern Oscillation (ENSO) teleconnections to tropical Indian Ocean (TIO) and their relationship with the Indian summer monsoon in the coupled general circulation model climate forecast system (CFS). The model shows good skill in simulating the impact of El Niño over the Indian Oceanic rim during its decay phase (the summer following peak phase of El Niño). Summer surface circulation patterns during the developing phase of El Niño are more influenced by local Sea Surface Temperature (SST) anomalies in the model unlike in observations. Eastern TIO cooling similar to that of Indian Ocean Dipole (IOD) is a dominant model feature in summer. This anomalous SST pattern therefore is attributed to the tendency of the model to simulate more frequent IOD events. On the other hand, in the model baroclinic response to the diabatic heating anomalies induced by the El Niño related warm SSTs is weak, resulting in reduced zonal extension of the Rossby wave response. This is mostly due to weak eastern Pacific summer time SST anomalies in the model during the developing phase of El Niño as compared to observations. Both eastern TIO cooling and weak SST warming in El Niño region combined together undermine the ENSO teleconnections to the TIO and south Asia regions
Indian Summer Monsoon Rainfall Characteristics During Contrasting Monsoon Years
No full textThe present paper presents a diagnostic study of two recent monsoon years, of which one is dry monsoon year (2009) and the other is wet monsoon year (2010). The study utilized the IMD gridded rainfall data set in addition to the Reynolds SST, NCEP-NCAR reanalysis wind and temperature products, and NOAA OLR. The study revealed that the months July and August are the most crucial months to decide whether the ISMR is wet or dry. However, during July 2009, most of the Indian subcontinent received more than 60 in the central and western coastal regions. In a wet monsoon year, about 35-45 of rainfall is contributed during June and July in most parts of India. During these years, the influence of features in the Pacific Ocean played vital role on the Indian summer monsoon rainfall. During 2009, Pacific SST was above normal in nino regions, characteristic of the El Nino structure; however, during 2010, the nino regions were clearly below normal temperature, indicating the La Nina pattern. The associated atmospheric general circulation through equatorial Walker and regional Hadley circulation modulates the tropospheric temperature, and hence the organized convective cloud bands. These cloud bands show different characteristics in northward propagation during dry and wet years of ISMR. During a dry year, the propagation speed and magnitudes are considerably higher than during a wet monsoon year
Investigation of the effects of high atmospheric aerosol pollution on the development of the high-depth cumulonimbus cloud
No full textConsidered is a case of the development of the cumulonimbus cloud (Cb) in the southwestern part of Saudi Arabia under the conditions of heavy pollution of atmosphere with natural aerosol. Using the ground-based radar and satellite radiometric instruments, the characteristics of the Cb are obtained for the cloud top height of more than 14 km and maximum reflectivity of 58 dBZ. To measure the precipitation rate using the radar data, the Z-I ratio obtained for the area under study was applied. To compute the precipitation rate, the results of the sounding with the SEVERI radiometer installed on the Meteosat-8 satellite were also used. Carried out are numerical experiments on the simulation of aerosol effects on the evolution of the cloud under study. The development of the cloud at the presence of background aerosol was simulated as well as at high aerosol concentration. Three cases are considered: aerosol is a passive admixture; aerosol has hygroscopic properties; aerosol has ice-forming properties. It is demonstrated that the most considerable effects on the cloud evolution are caused by the intensification of ice formation under the influence of aerosol; not only the time distribution of precipitation rate changes but also the amount of precipitation increase