Anyone who engages in flux tower research in urban areas is familiar with the many difficulties faced when looking for a suitable site (hard to find in the first place) and obtaining permission to install a tower (usually very challenging). But after a long and extensive search, which covered most parts of Singapore, access to an appropriate location (flat and uniformly built-up terrain void of anomalous emission sources) was finally secured. Using a MOE (Ministry of Education) research grant to Matthias Roth, a 21m flux tower was installed in January 2006 at the edge of a playing field on the grounds of the East Lodge Hostel in the Telok Kurau (TK) neighbourhood of Singapore.

 

For about 11 years the TK tower has provided semi-continuous measurements of meteorology, and fluxes of radiation, sensible heat, latent heat and carbon dioxide. Because of real-world vagaries there are some longer periods with missing data: after a lightning strike in April 2007 a number of turbulence sensors had to be replaced and power supply was switched from AC to solar, and in May 2008 a truck reversed into one or two guy wires bending one of middle sections of the tower which subsequently needed to be replaced.

 

In its initial phase manpower support came from three NUS postdocs: ANV Satyanarayana (now with IIT Kharagpur, India), Christer Jansson (Swedish Meteorological and Hydrological Institute) and Erik Velasco (SMART). After moving to SMART in 2010, Erik continued to be engaged in the project and was instrumental in the collection and analysis of the data. While the flux tower facility has been primarily funded through NUS research grants, additional financial support from SMART-CENSAM is gratefully acknowledged.

 

Between September 2012 and April 2013 a new and slightly taller (24m) tower was installed, partly in response to an increase in height of several buildings in the surrounding area following a relaxation in building height restrictions allowing 5-storey high buildings. This resulted in the replacement of 2-3 storey terrace houses with 5-storey small condominium developments. The TK tower ceased operation in September of 2017 after the lease of the site ran out and it was returned to the government for alternate use.

 

The TK tower is unique because it provides pioneering (in many cases the first for an equatorial city), long-term (i.e. multiple years) weather and flux information for a tropical urban location. The studies so far have provided results regarding all component of the energy budget including radiation, sensible and latent heat, storage and anthropogenic heat fluxes, as well as concentrations of carbon dioxide and the surface-atmosphere exchange of this important greenhouse gas including a detailed analysis of the role of vegetation in the carbon cycling over the chosen suburban surface. The flux tower data is also used to evaluate and improve a range of urban climate and land surface models (TEB, WRF, TERRA_URB, CLM, SURFEX, SUEWS, ENVI-met).

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Selected publications (in reverse chronological order)

 

Velasco E, Segovia E and Roth M, 2023. High-resolution maps of carbon dioxide and moisture fluxes over an urban neighborhood. Environmental Science: Atmosphere (https://doi.org/10.1039/D2EA00108J).

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Lipson M, Grimmond S, Best M, Chow W, Christen A, Chrysoulakis N, Coutts A, Crawford B, Earl S, Evans J, Fortuniak K, Heusinkveld BG, Hong J-W, Hong J, Järvi L, Jo S, Kim Y-H, Kotthaus S, Lee K, Masson V, McFadden JP, Michels O, Pawlak W, Roth M, Sugawara H, Tapper N, Velasco E and Ward HC, 2022. Harmonized gap-filled datasets from 20 urban flux tower sites. Earth System Science Data, 14, 5157–5178 (https://doi.org/10.5194/essd-14-5157-2022).

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Doan QV, Chen F, Kusaka H, Dipankar A, Khan A, Hamdi R, Roth, M and Niyogi D, 2022. Increased risk of extreme precipitation over an urban agglomeration with future global warming. Earth's Future, 10, e2021EF002563 (https://doi.org/10.1029/2021EF002563).

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Jongen HJ, Steeneveld GJ, Beringer A, Christen A, Chrysoulakis N, Fortuniak K, Hong J, Hong JW, Jacobs CMJ, Järvi L, Meier F, Pawlak W, Roth M, Theeuwes N, Velasco E, Vogt R and Teuling AJ, 2022. Urban Water Storage Capacity Inferred From Observed Evapotranspiration Recession. Geophysical Research Letters, 49, e2021GL096069 (https://doi.org/10.1029/2021GL096069).

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Sanchez B, Roth M, Simón-Moral A, Martilli A and Velasco E, 2021. Assessment of a meteorological mesoscale model's capability to simulate intra-urban thermal variability in a tropical city. Urban Climate, 40, 101006 (https://doi.org/10.1016/j.uclim.2021.101006).

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Simón-Moral A, Dipankar A, Doan QV, Sanchez C, Roth M, Becker E and Huang XY, 2021. Urban intensification of convective rainfall over the Singapore – Johor Bahru region. Quarterly Journal of Royal Meteorological Society, 147, 3665-3680 (https://doi.org/10.1002/qj.4147).

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Meili N, Manoli G, Burlando P, Bou-Zeid E, Chow W, Coutts A, Daly E, Nice K, Roth M, Tapper N, Velasco E, Vivoni E and Fatichi S, 2019. An urban ecohydrological model to quantify the effect of vegetation on urban climate and hydrology (UT&C v1.0). Geoscientific Model Development 13, 335-362 (https://www.geosci-model-dev.net/13/335/2020/gmd-13-335-2020-metrics.html). 

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Simón-Moral A, Dipankar A, Roth M, Sánchez C, Velasco E, and Huang H, 2019. Application of MORUSES single layer urban canopy model in a tropical city: results from Singapore. Q J R Meteorol Soc, 146, 576–597 (https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.3694). 

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Liu X, Li X-X, Harshan S, Roth M and Velasco E, 2017. Evaluation of an urban canopy model in a tropical city: The role of tree evapotranspiration. Environmental Research Letters 12, 094008 (http://iopscience.iop.org/article/10.1088/1748-9326/aa7ee7/meta).

 

Harshan S, Roth M, Velasco E and Demuzere M, 2017. Evaluation of an urban land surface scheme over a tropical suburban neighbourhood. Theoretical and Applied Climatology (https://link.springer.com/article/10.1007/s00704-017-2221-7).

 

Demuzere M, Harshan S, Järvi L, Roth M, Grimmond CSB, Masson V, Oleson KW, Velasco E, Wouters H, 2017. Impact of urban canopy models and external parameters on the modelled urban energy balance in a tropical city. Q J Roy Meteor Soc, 143, 1581-1596 (http://onlinelibrary.wiley.com/doi/10.1002/qj.3028/full).

 

Roth M, Jansson C, Velasco E, 2017. Multi-year energy balance and carbon dioxide fluxes over a residential neighbourhood in a tropical city. International Journal of Climatology, 37, 2679-2698 (http://onlinelibrary.wiley.com/doi/10.1002/joc.4873/full).

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Roth M, Lim V, 2017. Evaluation of canopy-layer air and mean radiant temperature simulations by a microclimate model over a tropical residential neighbourhood. Building and Environment, 112, 177-189 (http://dx.doi.org/10.1016/j.buildenv.2016.11.026).

 

Velasco E, Roth M, Norford L, Molina LT, 2016. Does urban vegetation enhance carbon sequestration? Landscape and Urban Planning, 148, 99–107 (https://doi.org/10.1016/j.landurbplan.2015.12.003).

 

Velasco EVS, Roth M, Tan SH, Quak M, Nabarro SDH and Norford L, 2013. Velasco EVS, Roth M, Tan SH, Quak M, Nabarro SDH and Norford L, 2013: The role of vegetation in the CO2 flux from a tropical urban neighbourhood. Atmos Chem Phys 13, 10185–1020 (https://doi.org/10.5194/acp-13-10185-2013).

 

Li X, Koh T-Y, Entekhabi D, Roth M, Panda J and Norford L, 2013. A multi-resolution ensemble study of a tropical urban environment and its interaction with the background regional atmosphere. J Geoph Res 118, 9804-9818 (https://doi.org/10.1002/jgrd.50795).

 

Quah, KLA and Roth M, 2012. Diurnal and weekly variation of anthropogenic heat emissions in a tropical city, Singapore. Atmos Environ 46, 92-103 (https://doi.org/10.1016/j.atmosenv.2011.10.015).

 

Velasco EVS and Roth M, 2010. Cites as net sources of CO2: Review of atmospheric CO2 exchange in urban environments measured by eddy covariance technique. Geography Compass 4/9, 1238–1259 (https://doi.org/10.1111/j.1749-8198.2010.00384.x).