scholarly journals On the Assessment of a Cooling Tower Scheme for High-Resolution Numerical Weather Modeling for Urban Areas

2019 ◽  
Vol 58 (6) ◽  
pp. 1399-1415 ◽  
Author(s):  
Miao Yu ◽  
Jorge González ◽  
Shiguang Miao ◽  
Prathap Ramamurthy
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Urban Areas ◽  
Cooling Tower ◽  
Absolute Humidity ◽  
Heat Fluxes ◽  
Anthropogenic Heat ◽  
Near Surface ◽  
Anthropogenic Heat Flux ◽  
Temperature Errors

AbstractA cooling tower scheme that quantifies the sensible and latent anthropogenic heat fluxes released from buildings was coupled to an operational forecasting system [Rapid Refresh Multiscale Analysis and Prediction of the Beijing Urban Meteorological Institute (RMAPS-Urban)] and was evaluated in the context of the megacity of Beijing, China, during summer months. The objective of this scheme is to correct for underestimations of surface latent heat fluxes in regional climate modeling and weather forecasts in urban areas. The performance for surface heat fluxes by the modified RMAPS-Urban is greatly improved when compared with a suite of observations in Beijing. The cooling tower scheme increases the anthropogenic latent heat partition by 90% of the total anthropogenic heat flux release. Averaged surface latent heat flux in urban areas increases to about 64.3 W m−2 with a peak of 150 W m−2 on dry summer days and 40.35 W m−2 with a peak of 150 W m−2 on wet summer days. The model performance of near-surface temperature and humidity is also improved. Average 2-m temperature errors are reduced by 1°C, and maximum and minimum temperature errors are improved by 2°–3°C; absolute humidity is increased by 5%.

scholarly journals A Partition Modeling for Anthropogenic Heat Flux Mapping in China

2019 ◽  
Vol 11 (9) ◽  
pp. 1132 ◽  
Author(s):  
Shasha Wang ◽  
Deyong Hu ◽  
Shanshan Chen ◽  
Chen Yu
Keyword(s):  
Climate Change ◽  
Heat Flux ◽  
Spatial Distribution ◽  
High Resolution ◽  
Urban Areas ◽  
Thermal Environment ◽  
Modeling Method ◽  
Anthropogenic Heat ◽  
Regional Characteristics ◽  
Anthropogenic Heat Flux

Anthropogenic heat (AH) generated by human activities has a major impact on urban and regional climate. Accurately estimating anthropogenic heat is of great significance for studies on urban thermal environment and climate change. In this study, a gridded anthropogenic heat flux (AHF) estimation scheme was constructed based on socio-economic data, energy-consumption data, and multi-source remote sensing data using a partition modeling method, which takes into account the regional characteristics of AH emission caused by the differences in regional development levels. The refined AHF mapping in China was realized with a high resolution of 500 m. The results show that the spatial distribution of AHF has obvious regional characteristics in China. Compared with the AHF in provinces, the AHF in Shanghai is the highest which reaches 12.56 W·m−2, followed by Tianjin, Beijing, and Jiangsu. The AHF values are 5.92 W·m−2, 3.35 W·m−2, and 3.10 W·m−2, respectively. As can be seen from the mapping results of refined AHF, the high-value AHF aggregation areas are mainly distributed in north China, east China, and south China. The high-value AHF in urban areas is concentrated in 50–200 W·m−2, and maximum AHF in Shenzhen urban center reaches 267 W·m−2. Further, compared with other high resolution AHF products, it can be found that the AHF results in this study have higher spatial heterogeneity, which can better characterize the emission characteristics of AHF in the region. The spatial pattern of the AHF estimation results correspond to the distribution of building density, population, and industry zone. The high-value AHF areas are mainly distributed in airports, railway stations, industry areas, and commercial centers. It can thus be seen that the AHF estimation models constructed by the partition modeling method can well realize the estimation of large-scale AHF and the results can effectively express the detailed spatial distribution of AHF in local areas. These results can provide technical ideas and data support for studies on surface energy balance and urban climate change.

scholarly journals Multi-season eddy covariance observations of energy, water and carbon fluxes over a suburban area in Swindon, UK

2013 ◽  
Vol 13 (9) ◽  
pp. 4645-4666 ◽  
Author(s):  
H. C. Ward ◽  
J. G. Evans ◽  
C. S. B. Grimmond
Keyword(s):  
Heat Flux ◽  
Eddy Covariance ◽  
Latent Heat ◽  
Sensible Heat Flux ◽  
Significant Proportion ◽  
Suburban Area ◽  
Anthropogenic Heat ◽  
Surface Conductance ◽  
Sensible Heat ◽  
Anthropogenic Heat Flux

Abstract. Eddy covariance measurements of the turbulent sensible heat, latent heat and carbon dioxide fluxes for 12 months (2011–2012) are reported for the first time for a suburban area in the UK. The results from Swindon are comparable to suburban studies of similar surface cover elsewhere but reveal large seasonal variability. Energy partitioning favours turbulent sensible heat during summer (midday Bowen ratio 1.4–1.6) and latent heat in winter (0.05–0.7). A significant proportion of energy is stored (and released) by the urban fabric and the estimated anthropogenic heat flux is small but non-negligible (0.5–0.9 MJ m−2 day−1). The sensible heat flux is negative at night and for much of winter daytimes, reflecting the suburban nature of the site (44% vegetation) and relatively low built fraction (16%). Latent heat fluxes appear to be water limited during a dry spring in both 2011 and 2012, when the response of the surface to moisture availability can be seen on a daily timescale. Energy and other factors are more relevant controls at other times; at night the wind speed is important. On average, surface conductance follows a smooth, asymmetrical diurnal course peaking at around 6–9 mm s−1, but values are larger and highly variable in wet conditions. The combination of natural (vegetative) and anthropogenic (emission) processes is most evident in the temporal variation of the carbon flux: significant photosynthetic uptake is seen during summer, whilst traffic and building emissions explain peak release in winter (9.5 g C m−2 day−1). The area is a net source of CO2 annually. Analysis by wind direction highlights the role of urban vegetation in promoting evapotranspiration and offsetting CO2 emissions, especially when contrasted against peak traffic emissions from sectors with more roads. Given the extent of suburban land use, these results have important implications for understanding urban energy, water and carbon dynamics.

scholarly journals Revising the definition of anthropogenic heat flux from buildings: role of human activities and building storage heat flux

2021 ◽  
Author(s):  
Yiqing Liu ◽  
Zhiwen Luo ◽  
Sue Grimmond
Keyword(s):  
Heat Flux ◽  
Energy Consumption ◽  
Energy Balance ◽  
Human Activities ◽  
Building Energy ◽  
Heat Emission ◽  
Heat Fluxes ◽  
Anthropogenic Heat ◽  
Anthropogenic Heat Flux ◽  
The Difference

Abstract. Buildings are a major source of anthropogenic heat emissions, impacting energy use and human health in cities. The difference between building energy consumption and building anthropogenic heat emission magnitudes and time lag and are poorly quantified. Energy consumption (QEC) is a widely used proxy for the anthropogenic heat flux from buildings (QF,B). Here we revisit the latter’s definition. If QF,B is the heat emission to the outdoor environment from human activities within buildings, we can derive it from the changes in energy balance fluxes between occupied and unoccupied buildings. Our derivation shows the difference between QEC and QF,B is attributable to a change in the storage heat flux induced by human activities (∆So-uo) (i.e., QF,B = QEC − ∆So-uo). Using building energy simulations (EnergyPlus) we calculate the energy balance fluxes for a simplified isolated building (obtaining QF,B, QEC, ∆So-uo) with different occupancy states. The non-negligible differences in diurnal patterns between QF,B and QEC caused by thermal storage (e.g. hourly QF,B to QEC ratios vary between −2.72 and 5.13 within a year in Beijing, China). Negative QF,B can occur as human activities can reduce heat emission from building but are associated with a large storage heat flux. Building operations (e.g., open windows, use of HVAC system) modify the QF,B by affecting not only QEC but also the ∆So-uo diurnal profile. Air temperature and solar radiation are critical meteorological factors explaining day-to-day variability of QF,B. Our new approach could be used to provide data for future parameterisations of both anthropogenic heat flux and storage heat fluxes from buildings. It is evident that storage heat fluxes in cities may also be impacted by occupant behaviour.

scholarly journals Components of near-surface energy balance derived from satellite soundings – Part 2: Noontime latent heat flux

2014 ◽  
Vol 11 (24) ◽  
pp. 7369-7382 ◽  
Author(s):  
K. Mallick ◽  
A. Jarvis ◽  
G. Wohlfahrt ◽  
G. Kiely ◽  
T. Hirano ◽  
...  
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Land Surface ◽  
Vegetation Index ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Simple Method ◽  
Near Surface ◽  
Available Energy

Abstract. This paper introduces a relatively simple method for recovering global fields of latent heat flux. The method focuses on specifying Bowen ratio estimates through exploiting air temperature and vapour pressure measurements obtained from infrared soundings of the AIRS (Atmospheric Infrared Sounder) sensor onboard NASA's Aqua platform. Through combining these Bowen ratio retrievals with satellite surface net available energy data, we have specified estimates of global noontime surface latent heat flux at the 1°×1° scale. These estimates were provisionally evaluated against data from 30 terrestrial tower flux sites covering a broad spectrum of biomes. Taking monthly average 13:30 data for 2003, this revealed promising agreement between the satellite and tower measurements of latent heat flux, with a pooled root-mean-square deviation of 79 W m−2, and no significant bias. However, this success partly arose as a product of the underspecification of the AIRS Bowen ratio compensating for the underspecification of the AIRS net available energy, suggesting further refinement of the approach is required. The error analysis suggested that the landscape level variability in enhanced vegetation index (EVI) and land surface temperature contributed significantly to the statistical metric of the predicted latent heat fluxes.

scholarly journals Case Study of Moisture and Heat Budgets within Atmospheric Rivers

2015 ◽  
Vol 143 (10) ◽  
pp. 4145-4162 ◽  
Author(s):  
Qianwen Luo ◽  
Wen-wen Tung
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Radiative Forcing ◽  
Deep Convection ◽  
Sensible Heat Flux ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Near Surface ◽  
Atmospheric Rivers ◽  
Heat Budgets

Abstract This work studies moisture and heat budgets within two atmospheric rivers (ARs) that made landfall on the west coast of North America during January 2009. Three-dimensional kinematic and thermodynamic fields were constructed using ECMWF Year of Tropical Convection data and global gridded precipitation datasets. Differences between the two ARs are observed, even though both had embedded precipitating convective organizations of the same spatial scale. AR1 extended from 20° to 50°N in an almost west–east orientation. It had excessive warm and moist near-surface conditions. Its precipitating systems were mainly distributed on the southwest and northeast sides of the AR, and tended to exhibit stratiform-type vertical heat and moisture transports. In contrast, AR2 spanned latitudes between 20° and 60°N in a north–south orientation. It was narrower and shorter than AR1, and was mostly covered by pronounced precipitating systems, dominated by a deep convection type of heating throughout the troposphere. In association with these distinctions, the atmosphere over the northeastern Pacific on average experienced episodic cooling and drying despite the occurrence of AR1, yet underwent heating and drying during AR2, when latent heating was strong. Downward sensible heat flux and weak upward surface latent heat flux were observed particularly in AR1. In addition, cloud radiative forcing (CRF) was very weak in AR1, whereas it was strongly negative in AR2. In short, it is found that the oceanic convection in ARs both impacts the moisture transport of ARs, as well as modifies the heat balance in the midlatitudes through latent heat release, convective heat transport, surface heat fluxes, and CRF.

scholarly journals Modeling the Partitioning of Turbulent Fluxes at Urban Sites with Varying Vegetation Cover

2016 ◽  
Vol 17 (10) ◽  
pp. 2537-2553 ◽  
Author(s):  
M. J. Best ◽  
C. S. B. Grimmond
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Water Use ◽  
Vegetation Cover ◽  
Bowen Ratio ◽  
Anthropogenic Heat ◽  
Vegetation Fraction ◽  
Anthropogenic Heat Flux ◽  
External Water ◽  
The Impact

Abstract Inclusion of vegetation is critical for urban land surface models (ULSM) to represent reasonably the turbulent sensible and latent heat flux densities in an urban environment. Here the Joint UK Land Environment Simulator (JULES), a ULSM, is used to simulate the Bowen ratio at a number of urban and rural sites with vegetation cover varying between 1% and 98%. The results show that JULES is able to represent the observed Bowen ratios, but only when the additional anthropogenic water supplied into the urban ecosystem is considered. The impact of the external water use (e.g., through irrigation or street cleaning) on the surface energy flux partitioning can be as substantial as that of the anthropogenic heat flux on the sensible and latent heat fluxes. The Bowen ratio varies from 1 to 2 when the plan area vegetation fraction is between 30% and 70%. However, when the vegetation fraction is less than 20%, the Bowen ratios increase substantially (2–10) and have greater sensitivity to assumptions about external water use. As there are few long-term observational sites with vegetation cover less than 30%, there is a clear need for more measurement studies in such environments.

scholarly journals Multi-season eddy covariance observations of energy, water and carbon fluxes over a suburban area in Swindon, UK

2012 ◽  
Vol 12 (11) ◽  
pp. 29147-29201 ◽  
Author(s):  
H. C. Ward ◽  
J. G. Evans ◽  
C. S. B. Grimmond
Keyword(s):  
Heat Flux ◽  
Eddy Covariance ◽  
Latent Heat ◽  
Significant Proportion ◽  
Carbon Dioxide Flux ◽  
Suburban Area ◽  
Anthropogenic Heat ◽  
Surface Conductance ◽  
Sensible Heat ◽  
Anthropogenic Heat Flux

Abstract. Eddy covariance measurements of the turbulent sensible heat, latent heat and carbon dioxide flux for twelve months (2011–2012) are reported for the first time for a suburban area in the UK. The results from Swindon are compatible with suburban studies of similar surface cover elsewhere but reveal large seasonal variability. Energy partitioning favours turbulent sensible heat during summer (midday Bowen ratio 1.4–1.6) and latent heat in winter (0.05–0.7), a significant proportion of energy is stored (and released) by the urban fabric and the estimated anthropogenic heat flux is small but non-negligible (0.5–0.9 MJ m−2 day−1). The sensible heat flux is negative at night and for much of winter daytimes, reflecting the vegetated nature of the site (44%). Latent heat fluxes appear to be water limited during a dry spring in both 2011 and 2012, when the response of the surface to moisture availability can be seen on a daily timescale. Energy and other factors are more relevant controls at other times; at night the wind speed is important. Surface conductance follows a smooth, asymmetrical diurnal course peaking at around 7–10 mm s−1 but values are larger and highly variable for wet conditions. The combination of natural (vegetative) and anthropogenic (emission) processes is most evident in the temporal variation of the carbon flux: significant photosynthetic uptake is seen during summer, whilst traffic and building emissions explain peak release in winter (9.87 g C m−2 day−1). The area is a net source of CO2 annually. Analysis by wind direction highlights the role of urban vegetation in promoting evapotranspiration and offsetting CO2 emissions, especially when contrasted against peak traffic emissions from sectors with more roads. Given the extent of suburban land use, these results have important implications for understanding urban energy, water and carbon dynamics.

scholarly journals Simulation of the Impacts of Urbanization on Winter Meteorological Fields over the Pearl River Delta Region

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Naixing Luo ◽  
Liping Zeng ◽  
Wenshi Lin ◽  
Fangzhou Li ◽  
Baolin Jiang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Latent Heat ◽  
Urban Areas ◽  
Pearl River Delta ◽  
Sensible Heat Flux ◽  
Heat Fluxes ◽  
Pearl River ◽  
Sensible Heat ◽  
Pearl River Delta Region ◽  
Delta Region

The influences of urbanization on weather in Guangdong Province, China, were studied using the Weather Research and Forecasting model from 31 December 2009 through 3 January 2010. Model outputs were compared with extensive monitoring of meteorological data to examine the simulation ability. Model results between tests (with and without land-use change) show that the urbanization had major effects on meteorological fields across nearly the entire Pearl River Delta region and particularly in urban areas. Studied fields (wind speed, temperature, precipitation, and sensible and latent heat fluxes) were affected by the urbanization of the PRD region. The major influences occurred in urban areas, where wind speeds decreased greatly, while the daytime surface upward sensible heat flux clearly increased. Unlike the sensible heat flux, the latent heat flux had a nonmonotonic increase or decrease. As a consequence of the two heat fluxes, 2-m temperature varied with location and time. Change of precipitation was complex. The main rain band became more concentrated, while precipitation decreased upwind of the urban area and increased downwind.

Effects of Sea Spray on Tropical Cyclones Simulated under Idealized Conditions

2008 ◽  
Vol 136 (5) ◽  
pp. 1686-1705 ◽  
Author(s):  
Jeffrey S. Gall ◽  
William M. Frank ◽  
Young Kwon
Keyword(s):  
Heat Flux ◽  
Surface Layer ◽  
Latent Heat ◽  
Surface Wind ◽  
Heat Fluxes ◽  
Sea Spray ◽  
High Wind ◽  
Near Surface ◽  
Wind Region ◽  
Spray Droplets

Abstract Under high-wind conditions, breaking waves and whitecaps eject large numbers of sea spray droplets into the atmosphere. The spray droplets originate with the same temperature and salinity as the ocean surface and thus increase the effective surface area of the ocean in contact with the atmosphere. As a result, the spray alters the total sensible and latent heat fluxes in the near-surface layer. The spray drops in the near-surface layer also result in horizontal and vertical spray-drag effects. The mass of the spray introduces an additional drag in the vertical momentum equation and tends to stabilize the lower boundary layer (BL). An initially axisymmetric control hurricane was created from the output of a real-data simulation of Hurricane Floyd (1999) using the nonhydrostatic fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5, version 3.4). The subsequent simulations, however, are not axisymmetric because the mass, wind, and spray fields are allowed to develop asymmetries. While such a design does not result in an axisymmetric simulation, the mass, wind, and spray fields develop more realistic structures than in an axisymmetric simulation. Simulations of the hurricane were conducted using a version of the Fairall et al. (1994) sea spray parameterization, which includes horizontal and vertical spray-drag effects. The simulations were run using varying spray-source function intensities and with and without horizontal and vertical spray-drag effects. At present, the relationship of spray production to surface wind speed is poorly known for hurricane-force wind regimes. Results indicate that spray modifies the hurricane structure in important but complex ways. Spray moistens the near-surface layer through increased evaporation. The effect of spray on the near-surface temperature profile depends on the amount of spray and its location in the hurricane. For moderate spray amounts, the near-surface layer warms within the high-wind region of the hurricane and cools at larger radii. For larger spray amounts, the near-surface layer warms relative to the moderate spray case. The moderate spray simulations (both with and without drag effects) have little net effect on the hurricane intensity. However, in the heavier spray runs, the total sensible heat flux is enhanced by 200 W m−2, while the total latent heat flux is enhanced by over 150 W m−2 in the high-wind region of the storm. Horizontal spray drag decreases wind speeds between 1 and 2 m s−1, and vertical spray drag increases the stability of the lower BL. In these heavy spray runs, the effect of the enhanced spray sensible and latent heat fluxes dominates the negative spray-drag effects, and as a result, the modeled storm intensity is upward of 10 mb stronger than the control run by the end of the simulation time. This study shows that spray has the capability of significantly affecting hurricane structure, but to do so, the amount of spray ejected into the BL of the hurricane would need to lie near the upper end of the currently hypothesized spray-source functions.

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