The suburban energy balance: Methodological considerations and results for a mid‐latitude west coast city under winter and spring conditions

Knowledge of the surface energy balance is fundamental to understanding the boundary layer meteorology and climatology of urban areas. This study reports some of the first direct measurements of energy fluxes over the city of Christchurch, New Zealand, during both summer and winter. Observations of the surface energy balance were made over two mainly residential suburbs: St Albans and Beckenham. Net all-wave radiation Q * was measured with a net radiometer, the eddy covariance approach was used to measure the turbulent heat fluxes (sensible heat Q H , and latent heat Q E ), and the heat storage flux Q S was estimated as the energy balance residual. During the predominant northeasterlies and unstable conditions in summer, the fetch at St Albans includes a commercial warehouse as well as residential areas. In summer, on a daily basis, Q H is the dominant heat sink followed by Q S and Q E . However, during daytime Q S can be considerable and may approach the magnitude of Q H . Evaporation is low because the turbulent flux source areas are mainly centred over the commercial warehouse and yard, which have little greenspace. In winter the flux source areas are mainly residential for both sites, and the small daily surplus of Q * is partitioned mostly into Q S , with some Q E and a small Q H that may be directed either towards or away from the surface depending largely on the synoptic conditions. Under strong inversion conditions, which occur frequently in Christchurch during winter, the turbulent heat fluxes are very small and Q H may be directed towards the surface for many hours overnight and early in the morning. During foehn events the energy partitioning is significantly altered, particularly in winter. Net radiation may be substantially decreased, evaporation is usually markedly increased and in winter Q H may be directed towards the surface for much of the event.The results highlight the importance of seasonal and synoptic controls in energy partitioning at this location, although difficulties with fetch complicate the analysis.

Section: Energy Partitioning In Wintercontrasting

confidence: 80%

Comparison of summer‐ and winter‐time suburban energy fluxes in Christchurch, New Zealand

Spronken‐Smith

2002

“…Estimating Q F from the inventory of energy consumption is a classical approach (Grimmond, 1992;Kłysik, 1995;Ichinose et al, 1999;Sailor and Lu, 2004). This method assume that the final stage of all energy use is heat and that the delay between energy use and its restitution to heat is zero (Sailor and Lu, 2004).…”

Section: Estimates Of Q F From the Inventory Of Energy Consumptionmentioning

confidence: 99%

“…We have assumed that this value is also valid for tertiary sector buildings. According to previous studies (Grimmond, 1992;Sailor and Lu, 2004), we have neglected the input from human metabolism. The rasterization of the inventory has been carried out using a Geographical Information System (GIS).…”

Section: Estimates Of Q F From the Inventory Of Energy Consumptionmentioning

confidence: 99%

“…The first method is based on inventories of energy consumption and has been applied by Grimmond (1992) for a suburban area of Vancouver (Canada), by Kłysik (1995) for the city of Łódź (Poland), by Ichinose et al (1999) for Tokyo (Japan) and by Sailor and Lu (2004) for different cities in the United States. The estimation of Q F with a high spatial and temporal resolution by this method is almost impossible considering the wide range of energy uses and the organization of energy distribution.…”

Section: Introductionmentioning

confidence: 99%

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Anthropogenic heat release in an old European agglomeration (Toulouse, France)

Pigeon

Legain

Durand

et al. 2007

183

102

Abstract:The anthropogenic heat release, Q F , has been estimated for the old European agglomeration of Toulouse (France) from February 2004 to March 2005 in the frame of the CAPITOUL experiment. Surface energy balance (SEB) measurements have been conducted at a downtown site, over a dense urban area. A method is proposed to estimate Q F at the local scale around this site from observations, as the daily residual term of the SEB equation. The values obtained from this method are in agreement with what can be expected: Q F estimates are around 70 W m −2 during winter and 15 W m −2 during summer. On a larger scale (that of the agglomeration), an energy consumption inventory was conducted for the period of the field campaign with a 1-day temporal resolution and a 100-m spatial resolution. The estimates of Q F obtained with this second method were analysed at the local scale around the measurements site, and compared with estimates computed from the energy budget observations. For the winter period, both estimates are in good agreement. For the summer period, the method based on SEB measurements seems to underestimate Q F which is estimated around 30 W m −2 from the inventory. The simultaneous estimate of Q F , with these two independent methods is a strength of this study.At the scale of the agglomeration, the basal state of energy consumption (observed during the summer period) varies between 25 W m −2 for the densest areas to less than 5 W m −2 for the residential suburban areas. In the regions crossed by the major roads, the traffic is the major source during summer. Then during the winter period, Q F can reach 100 W m −2 in the densest areas of Toulouse whereas it ranges between 5 and 25 W m −2 in the suburban areas.

“…In cities, or parts thereof with intensive industrial or commercial activity, or where there is significant winter heating or summer air conditioning, this term may also be a significant component of the energy balance (Oke, 1987;Klysik, 1996;Ichinose et al, 1999). Q F may be estimated from energy consumption estimates and empirical traffic flow data (Oke, 1987;Grimmond, 1992;Sailor and Lu, 2004). Unfortunately, these data do not all usually match the temporal or spatial scale of the other SEB measurements and may only be compared over longer time frames.…”

Section: Introductionmentioning

confidence: 99%

Heat storage and anthropogenic heat flux in relation to the energy balance of a central European city centre

Offerle

Grimmond

Fortuniak

2005

Self Cite

191

151

The role of net heat storage Q S and anthropogenic heat Q F are considered in the surface energy balance for a downtown area in Łódź, Poland, for a 2 year period. Eddy covariance measurements provide estimates of the turbulent heat fluxes and radiometric measurements of the net all-wave radiation. A method to determine Q S based on representative surface temperature sampling is employed and compared with results from two other models. Results show that Q S is an important flux on the scale of hours to days and that it can be more than 10 W m −2 , on average, for periods of a week or more. By incorporating Q S estimates over hourly intervals, Q F was then determined as the residual of the energy balance. Using the approach, Q F averaged 32 W m −2 from October to March (60% of available energy), and −3 W m −2 from June to August. The physically unrealistic negative values for the summer period may suggest underestimation of turbulent fluxes, but no causal factor was identified. Although energy balance closure was close to 100% throughout the year, there was weaker agreement in the winter. This is attributed to errors in estimates of Q S and variation in Q F . Results highlight the need for future investigations of the urban surface energy balance to incorporate more complete measurements and estimates of Q S .