High aerospora levels and associated atmospheric circulation patterns: Pretoria, South Africa.

At high exposure levels, airborne pollen grains and fungal spores (termed aerospora hereafter), can trigger severe allergic respiratory diseases. For South Africa's administrative capital Pretoria, which boasts dense vegetation within a large urban forest, it is valuable from a health perspective to understand daily atmospheric circulation patterns associated with high aerospora levels. Therefore, we utilised a daily aerospora grain count dataset collected in Pretoria from 08/2019-02/2023 to investigate atmospheric circulation patterns (derived from ERA5 reanalysis sea level pressure [SLP] and 500 hPa geopotential height [zg500] fields) associated with high-risk aerospora levels (aerospora grain count > 90th percentile). Concentrated during October-May, there were 128 high-risk days, with 69.6% of days occurring in November, February and April. Although generally above-average mid-tropospheric subsidence levels prevailed over Pretoria during high-risk days, no single distinct atmospheric circulation pattern was associated with these high-risk days. Therefore, using Principal Component Analysis, we classified 14 Circulation Weather Types (CWTs) for October-May months between 08/2019-02/2023 to assess which CWTs most frequently occurred during high-risk days. Three CWTs had a statistically significant proportion of high-risk days - collectively they occurred during 37.1% of days studied, yet accounted for 45.3% of high-risk days. Among these CWTs, two CWTs were similarly associated with surface and mid-tropospheric high-pressure conditions, while the third was associated with a surface and mid-tropospheric trough. By comparing our CWT classification to daily synoptic charts (from the South African Weather Service), our classification can be used to identify days with potentially high allergenicity risk over Pretoria.

Gathering the evidence and identifying opportunities for future research in climate, heat and health in South Africa: The role of the South African Medical Research Council.

BACKGROUND: A changing climate is likely to have widespread and varying impacts on ecosystems and human health. South Africa (SA) is particularly vulnerable to the impacts of climate change, given the projected increases in temperature, and changes in the amount and patterns of rainfall. Moreover, SA's vulnerability is exacerbated by extreme inequality and poverty. To prepare for the impacts of climate change and to ensure timeous adaptation, a perspective is given on essential heat and health research in the country. Objectives. To gather studies conducted by the South African Medical Research Council (SAMRC)'s Environment and Health Research Unit (EHRU) to illustrate the range of possible research key areas in the climate, heat and health domain and to present future research priorities. Methods. Studies conducted by the SAMRC's EHRU were gathered and used to illustrate the range of possible research key areas in the climate, heat and health domain. Using national and international published and grey literature, and tapping into institutional research experiences, an overview of research findings to date and future research priorities were developed. Results. Heat and health-related research has focussed on key settings, for example, schools, homes and outdoor work places, and vulnerable groups such as infants and children, the elderly and people with pre-existing diseases. The need to address basic needs and services provision was emphasised as an important priority. Conclusions. High and low temperatures in SA are already associated with mortality annually; these impacts are likely to increase with a changing climate. Critical cross-sectoral research will aid in understanding and preparing for temperature extremes in SA.

An overview of regional and local characteristics of aerosols in South Africa using satellite, ground, and modeling data.

We present a comprehensive overview of particulate air quality across the five major metropolitan areas of South Africa (Cape Town, Bloemfontein, Johannesburg and Tshwane (Gauteng Province), the Industrial Highveld Air Quality Priority Area (HVAPA), and Durban), based on a decadal (1 January 2000 to 31 December 2009) aerosol climatology from multiple satellite platforms and detailed analysis of ground-based data from 19 sites throughout Gauteng Province. Satellite analysis was based on aerosol optical depth (AOD) from MODIS Aqua and Terra (550 nm) and MISR (555 nm) platforms, Ångström Exponent (α) from MODIS Aqua (550/865 nm) and Terra (470/660 nm), ultraviolet aerosol index (UVAI) from TOMS, and results from the Goddard Ozone Chemistry Aerosol Radiation and Transport (GOCART) model. At continentally influenced sites, AOD, α, and UVAI reach maxima (0.12-0.20, 1.0-1.8, and 1.0-1.2, respectively) during austral spring (September-October), coinciding with a period of enhanced dust generation and the maximum integrated intensity of close-proximity and subtropical fires identified by MODIS Fire Information for Resource Management System (FIRMS). Minima in AOD, α, and UVAI occur during winter. Results from ground monitoring indicate that low-income township sites experience by far the worst particulate air quality in South Africa, with seasonally averaged PM10 concentrations as much as 136 % higher in townships that in industrial areas. We report poor agreement between satellite and ground aerosol measurements, with maximum surface aerosol concentrations coinciding with minima in AOD, α, and UVAI. This result suggests that remotely sensed data are not an appropriate surrogate for ground air quality in metropolitan South Africa.

Human health impacts in a changing South African climate.

Climate change is projected to lead to warmer temperatures, especially in southern Africa, where the warming is predicted to be 2°C higher than the global increase. Given the high burden of disease already associated with environmental factors in this region, this temperature increase may lead to grave challenges for human health and quality of life. HIV/AIDS, poverty, food and water insecurity together with inequality and unemployment will further complicate the manner in which we will need to address the challenges of a changing climate. The health impacts are direct, such as increased temperatures leading to heat exhaustion, and indirect, such as likely increases in infectious diseases from contaminated water and changes in the distribution and/or magnitude of vector-borne diseases. The most effective measures for adapting to climate change to ensure healthy populations are to implement basic public health systems and services. These range from a continuous supply of clean water to adequate primary healthcare services. Support for required interventions is required not only from government, but also from healthcare professionals and communities. The need for disease surveillance, data capturing and more focused research is paramount.

Rainforest aerosols as biogenic nuclei of clouds and precipitation in the Amazon.

The Amazon is one of the few continental regions where atmospheric aerosol particles and their effects on climate are not dominated by anthropogenic sources. During the wet season, the ambient conditions approach those of the pristine pre-industrial era. We show that the fine submicrometer particles accounting for most cloud condensation nuclei are predominantly composed of secondary organic material formed by oxidation of gaseous biogenic precursors. Supermicrometer particles, which are relevant as ice nuclei, consist mostly of primary biological material directly released from rainforest biota. The Amazon Basin appears to be a biogeochemical reactor, in which the biosphere and atmospheric photochemistry produce nuclei for clouds and precipitation sustaining the hydrological cycle. The prevailing regime of aerosol-cloud interactions in this natural environment is distinctly different from polluted regions.