South Asia

Summary

South Asia is the southern subregion of Asia, which is defined in both geographical and ethnic-cultural terms. As commonly conceptualised, South Asia consists of the countries predominantly Afghanistan Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan, and Sri Lanka, Topographically, it is dominated by the Indian subcontinent and defined largely by the Indian Ocean in the south, and the Himalayas, Karakoram, and Pamir mountains in the north. The Amu Darya, which rises north of the Hindu Kush, forms a part of the northwestern border. On land (clockwise), South Asia is bounded by Central Asia to the north, East Asia and Southeast Asia to east, and West Asia to the west. The South Asian Association for Regional Cooperation (SAARC) is an economic cooperation organization in the region which was established in 1985 and includes all eight nations comprising South Asia. The core countries of South Asia have a total area of , which is 10% of the Asian continent. The popul

Official source

https://en.wikipedia.org/wiki/South_Asia

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As part of the Hemispheric Transport of Air Pollution (HTAP; < a href='http://www.htap.org' target='_blank'> http:// www.htap.org ) project, we analyze results from 15 global and 1 hemispheric chemical transport models and compare these to Clean Air Status and Trends Network (CASTNet) observations in the United States (US) for 2001. Using the policy-relevant maximum daily 8-h average ozone (MDA8 O-3) statistic, the multi-model ensemble represents the observations well (mean r(2)=0.57, ensemble bias = +4.1 ppbv for all US regions and all seasons) despite a wide range in the individual model results. Correlations are strongest in the northeastern US during spring and fall (r(2)=0.68); and weakest in the midwestern US in summer (r(2)=0.46). However, large positive mean biases exist during summer for all eastern US regions, ranging from 10-20 ppbv, and a smaller negative bias is present in the western US during spring (similar to 3 ppbv). In nearly all other regions and seasons, the biases of the model ensemble simulations are < 5 ppbv. Sensitivity simulations in which anthropogenic O-3-precursor emissions (NOx + NMVOC + CO + aerosols) were decreased by 20% in four source regions: East Asia (EA), South Asia (SA), Europe (EU) and North America (NA) show that the greatest response of MDA8 O-3 to the summed foreign emissions reductions occurs during spring in the West (0.9 ppbv reduction due to 20% emissions reductions from EA + SA + EU). East Asia is the largest contributor to MDA8 O-3 at all ranges of the O-3 distribution for most regions (typically similar to 0.45 ppbv) followed closely by Europe. The exception is in the northeastern US where emissions reductions in EU had a slightly greater influence than EA emissions, particularly in the middle of the MDA8 O-3 distribution (response of similar to 0.35 ppbv between 35-55 ppbv). EA and EU influences are both far greater (about 4x) than that from SA in all regions and seasons. In all regions and seasons O-3-precursor emissions reductions of 20% in the NA source region decrease MDA8 O-3 the most - by a factor of 2 to nearly 10 relative to foreign emissions reductions. The O-3 response to anthropogenic NA emissions is greatest in the eastern US during summer at the high end of the O-3 distribution (5-6 ppbv for 20% reductions). While the impact of foreign emissions on surface O-3 in the US is not negligible - and is of increasing concern given the recent growth in Asian emissions - domestic emissions reductions remain a far more effective means of decreasing MDA8 O-3 values, particularly those above 75 ppb (the current US standard).

2009

Future trends in wind resources and their consistency in the Indian sub-continent

Michael Lehning, Adrien Michel, Yasmine Zakari

We use the latest Coordinated Regional Dynamical Experiment regional climate models over South Asia at 0.22 degrees grid spacing (WAS-22) under two Representative Concentration Pathways scenarios (RCP 2.6 and RCP 8.5) to evaluate their performance against their predecessor at 0.44 degrees grid spacing (WAS-44) and investigate the impact of climate change on future wind resources in the Indian sub-continent. The comparison of WAS-22 with the previous WAS-44 regional climate models looks at their ability to reproduce annual and seasonal wind speed climatology and trends with respect reanalysis datasets and finds that WAS-22 models achieve the best results. Hence, we use WAS-22 models as a source of climate information, correlate them to local station measurements and wind farm operation data at three sites in the study domain. We then estimate future annual and seasonal wind trends in the Indian sub-continent. Our findings on future trends suggest increasing annual wind speeds in the north-west (+ 0.04 m/s per decade (+/- 8%)), the center (+ 0.03 m/s per decade (+/- 11%)) and the east (+ 0.02 m/s per decade (+/- 19%)) of the Indian sub-continent under the RCP 8.5 scenario at the end of the century, with changes occurring more substantially during the last 30 years of the century. The results project future perturbations during the pre-monsoon season occurring throughout India and trends with the highest magnitude concentrated during the monsoon season. An additional contribution of this investigation is a decision-making tool enabling the quantification of the spatio-temporal consistency of wind trends using a structure-function.

ELSEVIER2022

A multi-model assessment of pollution transport to the Arctic

Isabelle Bey

We examine the response of Arctic gas and aerosol concentrations to perturbations in pollutant emissions from Europe. East and South Asia, and North America using results from a coordinated model intercomparison. These sensitivities to regional emissions (mixing ratio change per unit emission) vary widely across models and species. Intermodel differences are systematic, however, so that the relative importance of different regions is robust. North America contributes the most to Arctic ozone pollution. For aerosols and CO, European emissions dominate at the Arctic surface but East Asian emissions become progressively more important with altitude, and arc dominant in the upper troposphere. Sensitivities show strong seasonality: surface sensitivities typically maximize during boreal winter for European and during spring for East Asian and North American emissions. Mid-tropospheric sensitivities, however, nearly always maximize during spring or summer for all regions. Deposition of black carbon (BC) onto Greenland is most sensitive to North American emissions. North America and Europe each contribute similar to 40% of total BC deposition to Greenland, with similar to 20% from East Asia. Elsewhere in the Arctic, both sensitivity and total BC deposition are dominated by European emissions. Model diversity for aerosols is especially large, resulting primarily from differences in aerosol physical and chemical processing, (including removal). Comparison of modeled aerosol concentrations with observations indicates problems in the models, and perhaps, interpretation of the measurements. For gas phase pollutants such as CO and O-3, which are relatively well-simulated, the processes contributing most to uncertainties depend on the source region and altitude examined. Uncertainties in the Arctic surface CO response to emissions perturbations are dominated by emissions for East Asian sources, while uncertainties in transport, emissions. and oxidation are comparable for European and North American sources. At higher levels. model-to-model variations in transport and oxidation are most important. Differences in photochemistry appear to play the largest role in the intermodel variations in Arctic ozone sensitivity, though transport also contributes substantially in the mid-troposphere.

2008

A multi-model assessment of pollution transport to the Arctic

Isabelle Bey

2008

2009