Subtropical Anticyclone

The change in air quality in cities can be the product of regulation and emissions. Regulations require enforcement of emission reduction, but it is often shifting economic and societal structures that influence pollutant emissions. This study examines the long-term record of air pollutants in Kaohsiung, where postwar industrialisation increased pollution substantially, although improvements are observed in recent decades as the city moved to a more mixed economy. The study tracks both gases and particles across a period of significant change in pollution sources in the city. Concentrations of SO 2 and aerosol SO 4 2− were especially high ~1970, but these gradually declined, although SO 4 2− to a lesser extent than its precursor, SO 2. While twenty-first century emissions of SO 2 and NO x have declined, this has been less so for NH 3 , because it arises from predominantly agricultural sources. The atmosphere in Kaohsiung continues to have high concentrations of O 3 , and these have risen in the city, likely a product of less titration by NO. The changes have meant that ozone has become an increasing threat to health and agriculture. Despite a potential for producing (NH 4) 2 SO 4 and NH 4 NO 3 aerosols, a product of a relatively constant supply of NH 3 , visibility has improved in recent years. Emissions of SO 2 and NO x should continue to be reduced, as these strongly affect the amount of fine secondary aerosol. However, the key problem may be ozone, which is difficult to control as it requires careful consideration of the balance of NO x and hydrocarbons so important to its production. Keywords Aerosols • Economic change • Health effects • Agricultural effects • Visibility Highlights • Kaohsiung PM, NO x , and SO 2 emissions and primary pollutants decline; O 3 increases. • Air quality change reflects regulation and Kaohsiung's move to a mixed economy. • The increasing O 3 enhances risks to health and agriculture. • Visibility improved despite active agricultural NH 3 emissions.

Tropospheric ozone (O3) has increased globally since the end of 20th century. Its formation undergoes complicated photochemical reactions and processes in the lower boundary layer. As a result, changes in O3 levels are not about one specific factor but a combined process of other effects such as anthropogenic emissions, topographic characteristics, and meteorological influences. Consequently, published studies often
show conflicting findings on O3 levels. NOx is one of the significant O3 precursors generated during anthropogenic combustion processes. Therefore, despite efforts in emission controls, reducing NOx will not guarantee a downward ozone trend. Furthermore, specific weather phenomena (e.g., anticyclones and sea–land breezes) can enhance
specific meteorological parameters that govern the transport and diffusion of O3 and precursors. The review summarizes current knowledge of O3 levels and NOx emissions in recent years. It helps to understand how meteorological parameters and specific regional
features influence ozone and its precursors, which is beneficial for efficient surface ozone evaluation and control

The bioclimatic prediction system BIOCLIM is employed to provide an estimate of Early to Middle Miocene climate from the overlapping present-day climatic parameter ranges of selected taxa recorded in the Latrobe Valley coal seams. Despite taxon identification to only a coarse taxonomic level, fairly tight climatic envelopes are derived, particularly for temperature parameters. The data suggest that mean annual temperatures may have been about 5°C higher than those of today, with a similar seasonal temperature variation. Minimum annual precipitation is estimated to have been at least 1500 mm and probably much higher, compared to the present average of 800 mm, with most of the additional rainfall falling in the wet season. By comparison with previous, more qualitative, estimates, the degree of seasonal variation is surprising, but may be accounted for by the high latitudinal position of southern Australia during the period of coal formation. A number of factors including the degree to which the distribution of rainforest taxa in the present day may reflect their climatic potential, the possibility of ecological change within recognisable taxa, and the influence of a swamp environment on taxon distributions, all of which may limit the accuracy or validity of these estimates, are examined. It is concluded that the estimates are realistic in broad terms, but can only apply to the limited periods of high sea level, which allowed accumulation of the swamp precursors of the brown coals.

The bioclimatic prediction system BIOCLIM is employed to provide an estimate of Early to Middle Miocene climate from the overlapping present-day climatic parameter ranges of selected taxa recorded in the Latrobe Valley coal seams. Despite taxon identification to only a coarse taxonomic level, fairly tight climatic envelopes are derived, particularly for temperature parameters. The data suggest that mean annual temperatures may have been about 5˚C higher than those of today, with a similar seasonal temperature variation. Minimum annual precipitation is estimated to have been at least 1500 mm and probably much higher, compared to the present average of 800 mm, with most of the additional rainfall falling in the wet season. By comparison with previous, more qualitative, estimates, the degree of seasonal variation is surprising, but may be accounted for by the high latitudinal position of southern Australia during the period of coal formation. A number of factors including the degree to...

A reconstruction of terrestrial temperature and precipitation for the New Zealand landmass over the past ∼30 million years is produced using pollen data from >2000 samples lodged in the New Zealand Fossil Record Electronic Database and modern climate data of nearest living relatives. The reconstruction reveals a warming trend through the late Oligocene to early Miocene, peak warmth in the middle Miocene, and stepwise cooling through the late Neogene. Whereas the regional signal in our reconstruction includes a ∼5–10 • northward tectonic drift, as well as an increase in high altitude biomes due to late Neogene and Pliocene uplift of the Southern Alps, the pattern mimics inferred changes in global ice extent, which suggests that global drivers played a major role in shaping local vegetation. Importantly, seasonal temperature estimates indicate low seasonality during the middle Miocene, and that subsequent Neogene cooling was largely due to cooler winters. We suggest that this may reflect increased Subantarctic influence on New Zealand vegetation as the climate cooled.

The Australian continent is large and therefore exhibits a range of very different climatic zones. Broadly, the continent is characterised by arid climatic regimes: four-fifths of the landmass receiving an annual rainfall of less than 600mm and one-half of the continent receiving less than 300 mm. These arid and semi-arid regions form the greatest proportion of inland Australia, and are fringed by narrow, wet and temperate climatic zones along the southwestern, southern and eastern coastal zones. Tropical monsoonal rainfall characterises the northern coastal zones. Compared to other continents on Earth, Australia has by far the lowest average rainfall. This low precipitation rate is coupled with a high evaporation rate meaning that surfacewater availability is also anomalously low compared to global averages. Average annual temperature also shows significant variation and in most areas there is also a high diurnal variation in temperature.

Today, southeastern Australia experiences a winter-dominated rainfall regime, governed by the seasonal migration of the highly zonal Southern Hemisphere subtropical anticyclone. The late Cenozoic history of this rainfall regime is poorly understood, but it has been widely accepted that its onset was a product of the intensification and northward migration of the subtropical anticyclone, driven by steepening of hemispheric temperature gradients associated with the initiation of extensive Northern Hemisphere glaciation, w2.6 million years ago (Ma). Here, we use fossil beetle remains from Stony Creek Basin, a small palaeolake record in upland southeastern Australia deposited over w280,000 years between w1.84 and 1.56 Ma, to quantitatively reconstruct regional climate during the Early Pleistocene. Climate reconstructions based on coexistence of extant beetle taxa indicate that temperatures were consistently 1-3 C warmer than present, and rainfall as high as or substantially higher than today, throughout the record. In particular, beetle data indicate that rainfall was similar to today during winter, but 2-2.4 times higher than today during summer. This is consistent with the presence of diverse rainforest pollen also present in the record, and indicates that the modern, winter-dominated rainfall regime was not yet in place by w1.5 Ma, at least one million years later than previously thought. We suggest that the Southern Hemisphere anticyclonic circulation must have been much less intense during the Early Pleistocene than today, rather than shifted meridionally as previously argued.