Matthias Roth
Email Address
geomr@nus.edu.sg
28 results
Publication Search Results
Now showing 1 - 10 of 28
Publication Review of atmospheric turbulence over cities(2000) Roth, M.; GEOGRAPHYPublication Urban-induced modifications to the diurnal cycle of rainfall over a tropical city(John Wiley and Sons Ltd, 2021-01-01) Quang-Van Doan; Dipankar, Anurag; Simón-Moral, A.; Sanchez, Claudio; Prasanna, Venkatraman; Roth, Matthias; Huang, Xiang-Yu; GEOGRAPHYThere is still no consensus on the mechanisms that modify precipitation over and around cities, especially for those located in the tropics where convective processes primarily drive rainfall. Here we contribute to the ongoing discussion about the urban-associated precipitation by investigating the urban effect on the diurnal cycle of rainfall over Singapore. We use the urban version of the numerical weather prediction system of the Meteorological Service Singapore (hereafter called uSINGV) at a 300 m horizontal resolution to simulate the rainfall conditions over Singapore and its surroundings during the inter-monsoon period between 2010 and 2014. Two simulations with different land surface conditions are conducted: one with urban areas (i.e. present conditions) and one without urban areas. uSINGV is shown to perform well for rainfall when compared to observations. Comparison between simulations reveals that the urban area is responsible for the formation of a rainfall “hot spot” over Singapore and Johor Bahru, located at the southern tip of the Malay Peninsula, and the urban effect is accountable for 20–30% of total rainfall during late afternoons and evenings, highlighting a strong urban effect on localized rainfall over a tropical city. Enhancement of convection due to the urban heat island effect, increased frictional convergence due to buildings' drag, the seaward shift of the sea-breeze front, and the increased inflow of boundary-layer moisture by the stronger sea breeze are suggested as most probable reasons for the increased rainfall in the urban area. © 2020 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society.Publication BUBBLE - An urban boundary layer meteorology project(2005) Rotach, M.W.; Richner, H.; Vogt, R.; Christen, A.; Parlow, E.; Bernhofer, C.; Batchvarova, E.; Clappier, A.; Roulet, Y.-A.; Feddersen, B.; Schatzmann, M.; Batchvarova, E.; Gryning, S.-E.; Mayer, H.; Martucci, G.; Mitev, V.; Oke, T.R.; Roth, M.; Ruffieux, D.; Salmond, J.A.; Voogt, J.A.; GEOGRAPHYPublication Review of Singapore's air quality and greenhouse gas emissions: Current situation and opportunities(2012-06) Velasco, E.; Roth, M.; GEOGRAPHYSingapore has many environmental accomplishments to its credit. Accessible data on air quality indicates that all criteria pollutants satisfy both U.S. Environmental Protection Agency (EPA) and World Health Organization (WHO) air quality standards and guidelines, respectively. The exception is PM2.5 (particles with an aerodynamic diameter ≤2.5 μm), which is not currently considered a criteria pollutant in Singapore but may potentially be the major local air pollution problem and cause for health concern. Levels of other airborne pollutants as well as their physical and chemical processes associated with local formation, transformation, dispersion, and deposition are not known. According to available emission inventories, Singapore's contribution to the total atmospheric pollution and carbon budget at the regional and global scales is small. Emissions per unit gross domestic product (GDP) are low compared with other countries, although Singapore's per-capita GDP and per-capita emissions are among the highest in the world. Some information is available on health effects, but the impacts on the ecosystem and the complex interactions of air pollution and climate change at a regional level are also unknown. This article reviews existing available information on atmospheric pollution and greenhouse gas emissions and proposes a multipollutant approach to greenhouse gas mitigation and local air quality. Singapore, by reducing its per-capita emissions, increasing the availability of information (e.g., through regularly publishing hourly and/or daily PM2.5 concentrations) and developing a research agenda in this area, would likely be seen to be a model of a high-density, livable, and sustainable city in Southeast Asia and other tropical regions worldwide. Singapore is widely recognized for its environmental achievements and often cited as a model of a high-density, livable, and sustainable city. This article reviews available information with the aim to provide a reference for future scientific research of strategic relevance for Singapore's air quality and greenhouse gas mitigation management under a multipollutant framework. However, the limited publicly accessible data and little scientific information prevent a comprehensive assessment of the local air quality and greenhouse gas emissions. Singapore's dynamic economy and strong profile in advanced science and technological innovation have the potential to enhance the research agenda in this area, which is not yet well developed in tropical cities. © Copyright 2012 A&WMA.Publication ICUC-7 Urban Climate Special Issue(2011-02) Roth, M.; Emmanuel, R.; Ichinose, T.; Salmond, J.; GEOGRAPHYPublication A historical review and assessment of urban heat island research in Singapore(2012-11) Roth, M.; Chow, W.T.; GEOGRAPHYThis historical review of 20 studies since the 1960s examines the influence of urban development on the thermal environment in Singapore, a fast growing tropical island city-state. Past observations are critically assessed with regard to experimental controls and station metadata. Given the availability of historical climate and developmental data spanning almost 50 years, changes in urban heat island (UHI) intensity and spatial coverage can be traced temporally. Rapid urban expansion in Singapore is clearly reflected in spatially and temporally changing air and surface temperature patterns. The nocturnal canopy-layer UHI intensity - measured as the difference between the commercial urban core and undeveloped areas close to primary or secondary rainforests for example - doubled in magnitude between 1965 and 2004. At the same time, the spatial extent of the nocturnal UHI has also expanded with the development of new housing and industrial districts. The influence of the growing city is also reflected in surface temperature. Two satellite images dated 13 years apart demonstrate the encroachment of areas with high surface temperatures into previously cooler areas during daytime corresponding with new public housing estates and low-rise residential areas or facilities being built. The results from our study contribute to the growing body of tropical heat island research. They provide baseline data for future research and urban development in the Singapore context and, more generally, offer important cues for urban planners to make tropical cities more sustainable. © 2012 Department of Geography, National University of Singapore and Blackwell Publishing Asia Pty Ltd.Publication Application of scintillometry in the urban atmosphere(2004) Roth, M.; Satyanarayana, A.N.V.; Salmond, J.A.; GEOGRAPHYPublication Evaluation of an urban canopy model in a tropical city: The role of tree evapotranspiration(2017) Liu, X; Li, X.-X; Harshan, S; Roth, M; Velasco, E; GEOGRAPHYA single layer urban canopy model (SLUCM) with enhanced hydrologic processes, is evaluated in a tropical city, Singapore. The evaluation was performed using an 11 month offline simulation with the coupled Noah land surface model/SLUCM over a compact low-rise residential area. Various hydrological processes are considered, including anthropogenic latent heat release, and evaporation from impervious urban facets. Results show that the prediction of energy fluxes, in particular latent heat flux, is improved when these processes were included. However, the simulated latent heat flux is still underestimated by ?40%. Considering Singapore's high green cover ratio, the tree evapotranspiration process is introduced into the model, which significantly improves the simulated latent heat flux. In particular, the systematic error of the model is greatly reduced, and becomes lower than the unsystematic error in some seasons. The effect of tree evapotranspiration on the urban surface energy balance is further demonstrated during an unusual dry spell. The present study demonstrates that even at sites with relatively low (11%) tree coverage, ignoring evapotranspiration from trees may cause serious underestimation of the latent heat flux and atmospheric humidity. The improved model is also transferable to other tropical or temperate regions to study the impact of tree evapotranspiration on urban climate. © 2017 The Author(s). Published by IOP Publishing Ltd.Publication Urban Water Storage Capacity Inferred From Observed Evapotranspiration Recession(AMER GEOPHYSICAL UNION, 2022-02-16) Jongen, HJ; Steeneveld, GJ; Beringer, J; Christen, A; Chrysoulakis, N; Fortuniak, K; Hong, J; Hong, JW; Jacobs, CMJ; Jarvi, L; Meier, F; Pawlak, W; Roth, M; Theeuwes, NE; Velasco, E; Vogt, R; Teuling, AJ; Prof Matthias Roth; GEOGRAPHYWater storage plays an important role in mitigating heat and flooding in urban areas. Assessment of the water storage capacity of cities remains challenging due to the inherent heterogeneity of the urban surface. Traditionally, effective storage has been estimated from runoff. Here, we present a novel approach to estimate effective water storage capacity from recession rates of observed evaporation during precipitation-free periods. We test this approach for cities at neighborhood scale with eddy-covariance based latent heat flux observations from 14 contrasting sites with different local climate zones, vegetation cover and characteristics, and climates. Based on analysis of 583 drydowns, we find storage capacities to vary between 1.3 and 28.4 mm, corresponding to e-folding timescales of 1.8–20.1 days. This makes the urban storage capacity at least five times smaller than all the observed values for natural ecosystems, reflecting an evaporation regime characterized by extreme water limitation.Publication An urban ecohydrological model to quantify the effect of vegetation on urban climate and hydrology (UT&C v1.0)(Copernicus GmbH, 2020) Meili, N.; Manoli, G.; Burlando, P.; Bou-Zeid, E.; Chow, W.T.L.; Coutts, A.M.; Daly, E.; Nice, K.A.; Roth, M.; Tapper, N.J.; Velasco, E.; Vivoni, E.R.; Fatichi, S.; GEOGRAPHYIncreasing urbanization is likely to intensify the urban heat island effect, decrease outdoor thermal comfort, and enhance runoff generation in cities. Urban green spaces are often proposed as a mitigation strategy to counteract these adverse effects, and many recent developments of urban climate models focus on the inclusion of green and blue infrastructure to inform urban planning. However, many models still lack the ability to account for different plant types and oversimplify the interactions between the built environment, vegetation, and hydrology. In this study, we present an urban ecohydrological model, Urban Tethys-Chloris (UT&C), that combines principles of ecosystem modelling with an urban canopy scheme accounting for the biophysical and ecophysiological characteristics of roof vegetation, ground vegetation, and urban trees. UT&C is a fully coupled energy and water balance model that calculates 2m air temperature, 2m humidity, and surface temperatures based on the infinite urban canyon approach. It further calculates the urban hydrological fluxes in the absence of snow, including transpiration as a function of plant photosynthesis. Hence, UT&C accounts for the effects of different plant types on the urban climate and hydrology, as well as the effects of the urban environment on plant well-being and performance. UT&C performs well when compared against energy flux measurements of eddy-covariance towers located in three cities in different climates (Singapore, Melbourne, and Phoenix). A sensitivity analysis, performed as a proof of concept for the city of Singapore, shows a mean decrease in 2m air temperature of 1.1 °C for fully grass-covered ground, 0.2 °C for high values of leaf area index (LAI), and 0.3 °C for high values of Vc,max (an expression of photosynthetic capacity). These reductions in temperature were combined with a simultaneous increase in relative humidity by 6.5 %, 2.1 %, and 1.6 %, for fully grass-covered ground, high values of LAI, and high values of Vc,max, respectively. Furthermore, the increase of pervious vegetated ground is able to significantly reduce surface runoff. © Author(s) 2020.
- «
- 1 (current)
- 2
- 3
- »