Atmosphere, Volume 1, Issue 1 (December 2010) – 6 articles , Pages 1-84

We used the ‘Radiative-Convective Model of the Earth-atmosphere system’ (OGIM) to investigate the cooling effects induced by sulphur injections into the stratosphere. The ensemble of numerical calculations was based on the A1B scenario from the IPCC Special Report on Emissions Scenarios (SRES). Several geoengineered scenarios were analysed, including the abrupt interruption of these injections in different scenarios and at different dates. We focused on the surface air temperature (SAT) anomalies induced by stratospheric sulphate aerosol generated in order to compensate future warming. Results show that continuous deployment of sulphur into the stratosphere could induce a lasting decrease in SAT. Retaining a constant aerosol loading equivalent to 6 TgS would delay the expected global warming by 53 years. Keeping the SAT constant in a context of increasing greenhouse gases (GHGs) means that the aerosol loading needs to be increased by 1.9% annually. This would offset the effect of increasing GHG under the A1B scenario. A major focus of this study was on the heating rates of SAT that would arise in different scenarios in case of an abrupt cessation of sulphur injections into the stratosphere. Our model results show that heating rates after geoengineering interruption would be 15–28 times higher than in a case without geoengineering, with likely important consequences for life on Earth. Larger initial sulphate loadings induced more intense warming rates when the geoengineering was stopped at the same time. This implies that, if sulphate loading was increased to maintain constant SAT in the light of increasing GHG concentrations, the later the geoengineering interruption was to occur, the higher the heating rates would be. Consequently, geoengineering techniques like this should only be regarded as last-resort measures and require intense further research should they ever become necessary. Full article

Global surface temperature trends, based on land and marine data, show warming of about 0.8 °C over the last 100 years. This rate of warming is sometimes questioned because of the existence of Urban Heat Islands (UHIs). In this study we compare the rate of temperature change estimated from measurements of land and marine temperatures for the same grid squares using 5° by 5° latitude/longitude grid-box datasets. For 1951–2009 the ‘land’ average warmed by 0.02 °C decade⁻¹ relative to the ‘sea surface temperature’ (SST) average. There were regional contrasts in the trends of land/sea temperature differences: the land warmed at a greater rate compared to the SST for regions north of 20°S, but the opposite occurred further south. Given strong forcing of the climate system, we would expect the land to change more rapidly than the ocean, so the differences represent an upper limit to the urbanization effect. Full article

A clear understanding of new particle formation processes in remote oceans is critical for properly assessing the role of oceanic dimethyl sulfide (DMS) emission on the Earth’s climate and associated climate feedback processes. Almost free from anthropogenic pollutants and leafed plants, the Antarctic continent and surrounding oceans are unique regions for studying the lifecycle of natural sulfate aerosols. Here we investigate the well-recognized seasonal variations of new particle formation around Antarctic coastal areas with a recently developed global size-resolved aerosol model. Our simulations indicate that enhanced DMS emission and photochemistry during the austral summer season lead to significant new particle formation via ion-mediated nucleation (IMN) and much higher particle number concentrations over Antarctica and surrounding oceans. By comparing predicted condensation nuclei larger than 10 nm (CN10) during a three-year period (2005–2007) with the long-period continuous CN10 measurements at the German Antarctic station Neumayer, we show that the model captures the absolute values of monthly mean CN10 (within a factor 2–3) as well as their seasonal variations. Our simulations confirm that the observed Antarctic CN10 and cloud condensation nuclei (CCN) seasonal variations are due to the formation of secondary particles during the austral summer. From the austral winter to summer, the zonally averaged CN10 and CCN in the lower troposphere over Antarctica increase by a factor of ~4–6 and ~2–4, respectively. This study appears to show that the H₂SO₄-H₂O IMN mechanism is able to account for the new particle formation frequently observed in the Antarctica region during the austral summer. Full article

Cyclone Monica was an intense Southern Hemisphere tropical cyclone of 2006. Although no in situ measurements of Monica’s inner core were made, microwave, infrared, and visible satellite instruments observed Monica before and during peak intensity through landfall on Australia’s northern coast. The author analyzes remote sensing measurements in detail to investigate Monica’s intensity. While Dvorak analysis of its imagery argues that it was of extreme intensity, infrared and microwave soundings indicate a somewhat lower intensity, especially as it neared landfall. The author also describes several numerical model runs that were made to investigate the maximum possible intensity for the observed environmental conditions; these simulations also suggest a lower intensity than estimates from Dvorak analysis alone. Based on the evidence from the various measurements and modeling, the estimated range for the minimum sea level pressure at peak intensity is 900 to 920 hPa. The estimated range for the one-minute averaged maximum wind speed at peak intensity is 72 to 82 m/s. These maxima were likely reached about 24 hours prior to landfall, with some weakening occurring afterward. Full article

This study monitored ultrafine particles (UFP) concurrent with environmental air quality data, investigating whether already existing instrumentation used by environmental authorities can provide reference values for estimating UFP concentrations. Of particular interest was the relation of UFP to PM₁₀ (particulate matter) and nitrogen oxides (NOx, NO₂) in ambient air. Existing PM measurement methods alone did not correspond exactly enough with the actual particle number, but we observed a link between NO_x and NO₂ to UFP concentration. The combined data could act as proxy-indicator for authorities in estimating particle number concentrations, but cannot replace UFP monitoring. Full article

The new online, Open Access journal Atmosphere has been launched to present reviews, regular research papers, communications and short notes on atmospheric topics. These topics include experimental and theoretical work related to the physical atmosphere, such as turbulence, atmospheric flow, dynamic and physical processes and mechanisms, atmospheric chemistry, such as changes in atmospheric composition, including aerosols, ozone, air pollution, chemical weather, meteorology and scale interaction, climate, climate change and environmental science, including water and energy cycles. [...] Full article