Diurnal microclimate profile in tropical coastal built environment (case: Universitas Islam Sultan Agung campus area, Semarang)

Microclimate is caused by the interaction between atmosphere and earth surfaces in local areas. Built environment has pay attention in microclimate since it considerably affects the thermal earth surfaces. This research is located in tropical coastal area, specifically at Universitas Islam Sultan Agung Semarang campus area as a part of built environment where close to the Java sea. The aim of this paper is to investigate the diurnal pattern of microclimate in research location before modelled to the wider area. A numerical modelling method is applied in this research to simulate the diurnal thermal pattern. The research shows that microclimate is influenced by the earth surface objects and following the sun movement respectively.

Extending the DMSP Nighttime Lights Time Series beyond 2013

Data collected by the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP-OLS) sensors have been archived and processed by the Earth Observation Group (EOG) at the National Oceanic and Atmospheric Administration (NOAA) to make global maps of nighttime images since 1994. Over the years, the EOG has developed automatic algorithms to make Stable Lights composites from the OLS visible band data by removing the transient lights from fires and fishing boats. The ephemeral lights are removed based on their high brightness and short duration. However, the six original satellites collecting DMSP data gradually shifted from day/night orbit to dawn/dusk orbit, which is to an earlier overpass time. At the beginning of 2014, the F18 satellite was no longer collecting usable nighttime data, and the focus had shifted to processing global nighttime images from Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) data. Nevertheless, it was soon discovered that the F15 and F16 satellites had started collecting pre-dawn nighttime data from 2012 onwards. Therefore, the established algorithms of the previous years were extended to process OLS data from 2013 onwards. Moreover, the existence of nighttime data from three overpass times for the year 2013–DMSP satellites F18 and F15 from early evening and pre-dawn, respectively, and the VIIRS from after midnight, made it possible to intercalibrate the images of three different overpass times and study the diurnal pattern of nighttime lights.

Temporal and vertical distributions of the occurrence of the cirrus clouds over the coastal station in the Indian monsoon region

Knowledge of the spatiotemporal coverage of the cirrus clouds is vital in quantifying the radiation budget of the earth-atmosphere system. In this paper, we present the diurnal and vertical distributions of the occurrence of the cirrus clouds during different seasons as well as its interannual variation over Kattankulathur (12.82° N, 80.04° E), east coast of the Bay of Bengal. The long-term (2016–2018) continuous observations of micropulse lidar (MPL) demonstrate the laminar and descending cirrus clouds that occur either as single or multiple layers. The single-layer cirrus occurrence shows a diurnal pattern with frequent occurrence in the late evening (~30–40 %) while multiple-layer cirrus clouds occurrence and early morning (~10–20 %), respectively. For the diurnal pattern in single layer cirrus cloud occurrences, convective processes dominate during the pre-monsoon, southwest (SW), and northeast (NE) monsoon seasons, while the freeze-drying process is favourable during the winter season. However, both convective and freeze-drying processes are dominant in the diurnal pattern of the multiple-layer cirrus occurrences. The occurrence is maximum (~40 %) during the SW and NE monsoon seasons and minimum (~25 %) during the winter. The vertical distributions indicate that the maximum occurrence is confined within the tropical tropopause layer (TTL) during all the seasons. The cirrus cloud rarely occurs above the tropopause; however, it frequently occurs below the TTL during all the seasons. The vertical extent of the occurrence has broader altitude coverage (~8–17 km) during December–March and June–September while narrower during April–May (~10–17 km) and October–November (~9–15 km). The cirrus clouds occurrence also exhibits interannual variations with higher occurrence during 2016 compared to 2017 and 2018 in association with El Nino Southern Oscillation (ENSO).

Night-time NO emissions suppress large amounts of chlorine radical formation in Delhi

<p>Concentrations of particulate chloride can reach values over 100 µg m<sup>-3</sup> during the winter in Delhi, which is among the highest levels recorded across the globe. In the presence of nitrogen pentoxide (N<sub>2</sub>O<sub>5</sub>), this chloride can form nitryl chloride (ClNO<sub>2</sub>), which photolyses in sunlight and releases the Cl radical. The Cl radical is an incredibly potent oxidant, reacting with some volatile organic compounds (VOCs) orders of magnitude faster than more common oxidants such as OH. Chlorine would therefore be expected to play a significant role in the oxidation of VOCs in Delhi.</p><p>We carried out intensive measurements of particle- and gas-phase physical and chemical properties during a field campaign in Delhi in early 2019. A suite of instruments was used, including a chemical ionisation mass spectrometer fitted with a filter inlet for aerosols and gases (FIGAERO-CIMS) to measure N<sub>2</sub>O<sub>5</sub> and ClNO<sub>2</sub>. Despite N<sub>2</sub>O<sub>5</sub> typically being considered a night-time compound, we in fact observed the highest concentrations in the mid-afternoon and almost none at all during the night. Further analysis indicated that the ubiquity of night-time NO<sub>x</sub> emissions in the city suppresses night-time production of N<sub>2</sub>O<sub>5</sub>. As a result of this unusual diurnal pattern, high concentrations of ClNO<sub>2</sub> are unable to form overnight. The morning peak in ClNO2 and the subsequent release of chlorine radicals, while large compared with some other urban environments, is therefore much smaller than might have been expected given the high levels of particulate chloride.</p><p>In this presentation, I will discuss our observations and the impact of this unusual diurnal pattern on the atmospheric chemical profile. Impacts include a shift of even typically ‘night-time’ oxidation patterns to the day and a likely overall reduced oxidative capacity in the city’s atmosphere. Our results indicate that a reduction in chlorine emissions must be considered in tandem with NO<sub>x</sub> emission reductions in efforts to reduce Delhi’s pollution.</p>

Variability of the atmospheric electric field in the South Atlantic marine boundary layer from the SAIL campaign

<p>The marine boundary layer offers a unique opportunity to investigate the electrical properties of the atmosphere, as the effect of natural radioactivity in driving near surface ionization is significantly reduced over the ocean, and the concentration of aerosols is also typically lower than over land. This work addresses the temporal variability of the atmospheric electric field in the South Atlantic marine boundary layer based on measurements from the SAIL (Space-Atmosphere-Ocean Interactions in the marine boundary Layer) project. The SAIL monitoring campaign took place on board the Portuguese navy tall ship NRP Sagres during its circumnavigation expedition in 2020.  Two identical field mills (CS110, Campbell Scientific) were installed on the same mast but at different heights (about 5 and 22 meters), recording the atmospheric electric field every 1-second. Hourly averages of the atmospheric electric field are analyzed for the ship’s leg from 3<sup>rd</sup> to 25<sup>th</sup> March, between Buenos Aires (South America) and Cape Town (South Africa). The median daily curve of the electric field has a shape compatible with the Carnegie curve, but significant variability is found in the daily pattern of individual days, with only about 30% of the days exhibiting a diurnal pattern consistent with the Carnegie curve.</p>

Decennial time trends and diurnal patterns of particle number concentrations in a central European city between 2008 and 2018

Multiple atmospheric properties were measured semi-continuously in the Budapest platform for Aerosol Research and Training laboratory, which represents the urban background for the time interval of 2008–2018. Data of 6 full measurement years during a decennial time interval were subjected to statistical time trend analyses by an advanced dynamic linear model and a generalized linear mixed model. The main interest in the analysed data set was on particle number concentrations in the diameter ranges from 6 to 1000 nm (N6−1000), from 6 to 100 nm (N6−100, ultrafine particles), from 25 to 100 nm (N25−100) and from 100 to 1000 nm (N100−1000). These data were supported by concentrations of SO2, CO, NO, NOx, O3, PM10 mass, as well as air temperature, relative humidity, wind speed, atmospheric pressure, global solar radiation, condensation sink, gas-phase H2SO4 proxy, classes of new aerosol particle formation (NPF), and growth events and meteorological macro-circulation patterns. The trend of the particle number concentrations derived as a change in the statistical properties of background state of the data set decreased in all size fractions over the years. Most particle number concentrations showed decreasing decennial statistical trends. The estimated annual mean decline of N6−1000 was (4–5) % during the 10-year measurement interval, which corresponds to a mean absolute change of −590 cm−3 in a year. This was interpreted as a consequence of the decreased anthropogenic emissions at least partly from road traffic alongside household heating and industry. Similar trends were not observed for the air pollutant gases. Diurnal statistical patterns of particle number concentrations showed tendentious variations, which were associated with a typical diurnal activity–time pattern of inhabitants in cities, particularly of vehicular road traffic. The trend patterns for NPF event days contained a huge peak from late morning to late afternoon, which is unambiguously caused by NPF and growth processes. These peaks were rather similar to each other in the position, shape and area on workdays and holidays, which implies that the dynamic and timing properties of NPF events are not substantially influenced by anthropogenic activities in central Budapest. The diurnal pattern for N25−100 exhibited the largest relative changes, which were related to particle emissions from high-temperature sources. The diurnal pattern for N100−1000 – which represents chemically and physically aged particles of larger spatial scale – were different from the diurnal patterns for the other size fractions.