Simone Kotthaus

Meteorology, air quality, and health in London: The ClearfLo project

AbstractAir quality and heat are strong health drivers, and their accurate assessment and forecast are important in densely populated urban areas. However, the sources and processes leading to high concentrations of main pollutants, such as ozone, nitrogen dioxide, and fine and coarse particulate matter, in complex urban areas are not fully understood, limiting our ability to forecast air quality accurately. This paper introduces the Clean Air for London (ClearfLo; www.clearflo.ac.uk) project’s interdisciplinary approach to investigate the processes leading to poor air quality and elevated temperatures.Within ClearfLo, a large multi-institutional project funded by the U.K. Natural Environment Research Council (NERC), integrated measurements of meteorology and gaseous, and particulate composition/loading within the atmosphere of London, United Kingdom, were undertaken to understand the processes underlying poor air quality. Long-term measurement infrastructure installed at multiple levels (street and eleva...

Effects of urban density on carbon dioxide exchanges: Observations of dense urban, suburban and woodland areas of southern England

Anthropogenic and biogenic controls on the surface-atmosphere exchange of CO2 are explored for three different environments. Similarities are seen between suburban and woodland sites during summer, when photosynthesis and respiration determine the diurnal pattern of the CO2 flux. In winter, emissions from human activities dominate urban and suburban fluxes; building emissions increase during cold weather, while traffic is a major component of CO2 emissions all year round. Observed CO2 fluxes reflect diurnal traffic patterns (busy throughout the day (urban); rush-hour peaks (suburban)) and vary between working days and non-working days, except at the woodland site. Suburban vegetation offsets some anthropogenic emissions, but 24-h CO2 fluxes are usually positive even during summer. Observations are compared to estimated emissions from simple models and inventories. Annual CO2 exchanges are significantly different between sites, demonstrating the impacts of increasing urban density (and decreasing vegetation fraction) on the CO2 flux to the atmosphere.

On the Potential Causes of the Nonstationary Correlations between West African Precipitation and Atlantic Hurricane Activity

Abstract For years, various indices of seasonal West African precipitation have served as useful predictors of the overall tropical cyclone activity in the Atlantic Ocean. Since the mid-1990s, the correlation unexpectedly deteriorated. In the present study, statistical techniques are developed to describe the nonstationary nature of the correlations between annual measures of Atlantic tropical cyclone activity and three selected West African precipitation indices (namely, western Sahelian precipitation in June–September, central Sahelian precipitation in June–September, and Guinean coastal precipitation in the preceding year’s August–November period). The correlations between these parameters are found to vary over the period from 1921 to 2007 on a range of time scales. Additionally, considerable year-to-year variability in the strength of these correlations is documented by selecting subsamples of years with respect to various meteorological factors. Broadly, in years when the environment in the main dev...

Wind observations above an urban river using a new lidar technique, scintillometry and anemometry

Airflow along rivers might provide a key mechanism for ventilation in cities: important for air quality and thermal comfort. Airflow varies in space and time in the vicinity of rivers. Consequently, there is limited utility in point measurements. Ground-based remote sensing offers the opportunity to study 3D airflow in locations which are difficult to observe with conventional approaches. For three months in the winter and spring of 2011, the airflow above the River Thames in central London was observed using a scanning Doppler lidar, a scintillometer and sonic anemometers. First, an inter-comparison showed that lidar-derived mean wind-speed estimates compare almost as well to sonic anemometers (root-mean-square error (rmse) 0.65-0.68 ms(-1)) as comparisons between sonic anemometers (0.35-0.73 ms(-1)). Second, the lidar duo-beam operating strategy provided horizontal transects of wind vectors (comparison with scintillometer rmse 1.12-1.63 ms(-1)) which revealed mean and turbulent airflow across the river and surrounds; in particular, channelled airflow along the river and changes in turbulence quantities consistent with the roughness changes between built and river environments. The results have important consequences for air quality and dispersion around urban rivers, especially given that many cities have high traffic rates on roads located on riverbanks.

LUCY: Large scale Urban Consumption of Energy

Model and datasets to document changes in global anthropogenic heat flux (QF) for spatial (30′′ × 30′′ to 0.5° × 0.5°) resolution and temporal coverage (historical, current and future). See further details in the Lindberg et al. publications linked from this record.

Atmospheric correction of ground-based thermal infrared camera through dart model

We introduced an approach to simulate and separate atmospheric contribution in ground-based thermal-infrared (TIR) camera measurements. Different from the traditional approach which uses the look-up table built from 1-D radiative transfer model (RTM), this approach directly simulates 3-D ray propagations and interactions in the heterogeneous urban environment by using the Discrete Anisotropic Radiative Transfer (DART) model. The atmospheric turbid cells that occupy every part of the urban scene are created using the vertical constituent distribution and the optical property profiles in the existing databases or from the actual meteorological measurements. The two components of atmospheric effects on the TIR at-sensor radiance are attenuated transmission and path thermal emission. Taking both into account, the at-surface radiance corresponding to the signal emitted only from the urban surface can be derived.

3D modeling of radiative transfer and energy balance in urban canopies combined to remote sensing acquisitions

In this paper we present a study on the use of remote sensing data combined to the 3D modeling of radiative transfer (RT) and energy balance in urban canopies in the aim to improve our knowledge on anthropogenic heat fluxes in several European cities (London, Basel, Heraklion, and Toulouse). The approach is based on the forcing by the use of LandSAT8 data of a coupled radiative transfer model DART (Direct Anisotropic Radiative Transfer) (www.cesbio.upstlse.fr/dart) with an energy balance module. LandSAT8 visible remote sensing data is used to better parametrize the albedo of the urban canopy and thermal remote sensing data is used to enhance the anthropogenic component in the coupled model. This work is conducted in the frame of the H2020 project URBANFLUXES, which aim is to improve the efficiency of remote-sensing data usage for the determination of the anthropogenic heat fluxes in urban canopies [5].

The impacts of green infrastructure on air quality and temperature

The temperatures and the amounts of air pollution experienced in urban environments are typically larger than in surrounding rural environments. Urban air pollution is associated with increased cardiovascular and respiratory diseases, some cancers, and increased temperatures with discomfort and in the vulnerable and elderly increased mortality. Managing urban air quality by reducing pollution exposure and maintaining equitable urban temperatures are priorities towards enhancing the health and well-being of the urban population. This chapter explores how, and to what extent, urban vegetation can influence the amounts of air pollutants and regulate urban air temperature. Urban vegetation generally has a positive influence, and under some circumstances, the capacity to make substantial gains in urban air quality and temperature regulation. Different species and forms of urban vegetation had different influences, as did the location of planting, but under some circumstances vegetation could negatively influence air-pollution and temperature. Approaches to maximise the benefits from planting urban vegetation are presented and it is acknowledged that more research is needed in order to optimise these benefits.