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The sea breeze is a common phenomenon in coastal cities, but its cooling effect has not been well investigated. In this research, we firstly propose a metric of sea breeze cooling capacity (SBCC) to quantify the cooling effect of sea breezes in a coastal city, Adelaide, Australia. Based on data from the Adelaide urban heat island monitoring network in 2010–2013, we reveal the temporal and spatial patterns of SBCC in summer days in the Adelaide Central Business District (CBD) and examine their associations with environmental variables. The results show that the inter-event variability of SBCC is explained by specific humidity and wind speed, while the spatial variability of SBCC is explained by distance towards the coast, frontal area index (FAI), terrain ruggedness index (TRI) and temperature prior to the sea breeze onset. Specifically, SBCC is negatively correlated with FAI and positively correlated with TRI. Future development of high-rise buildings in the Adelaide CBD can lead to changes in both FAI and TRI. It is estimated that the projected building development in Adelaide may cause a change of SBCC ranging from −195 to 143 °C h over an average summer. This research has important implications for urban planning, public health and energy consumption in coastal cities. • A concept of sea breeze cooling capacity (SBCC) is proposed to quantify the cooling effect of sea breezes in coastal cities. • FAI, TRI, distance from the coast and pre-onset temperature explain spatial variability of SBCC. • The diversity of building heights increases SBCC likely from vertical mixing, while mean building height reduces SBCC. [ABSTRACT FROM AUTHOR]

Abstract: The input of groundwater-borne nutrients to Adelaide''s (South Australia) coastal zone is not well known but could contribute to the ongoing decline of seagrass in the area. As a component of the Adelaide Coastal Waters Study (ACWS), the potential for using the radium quartet (223Ra, 224Ra, 226Ra and 228Ra) and 222Rn to evaluate submarine groundwater discharge (SGD) was evaluated. Potential isotopic signatures for SGD were assessed by sampling groundwater from three regional aquifers potentially contributing SGD to the ACWS area. In addition, intertidal groundwater was sampled at two sand beach sites. In general, the regional groundwaters were enriched in long-lived Ra isotopes (226Ra and 228Ra) and in 222Rn relative to intertidal groundwater. Radium activity (but not 222Rn activity) was positively correlated to salinity in groundwater from one of the regional aquifers and in intertidal groundwater. Radium isotope ratios (223Ra/226Ra, 224Ra/226Ra and 228Ra/226Ra) were less variable than individual Ra isotope activities within potential SGD sources. Recirculated seawater (estimated from the intertidal groundwater samples with seawater-like salinities) also had distinctly higher Ra isotope ratios than the regional groundwaters. The activities for all radioisotopes were relatively low in seawater. The activity of the short-lived 223Ra and 224Ra were highest at the shoreline and declined exponentially with distance offshore. In contrast, 228Ra and 226Ra activities had a weak linear declining trend with distance offshore. Rn-222 activity was at or near background in all seawater samples. The pattern of enrichment in short-lived Ra isotopes and the lack of 222Rn in seawater suggest that seawater recirculation is the main contributor to SGD in the ACWS area. Preliminary modeling of the offshore flux of 228Ra and 226Ra suggest that the SGD flux to the ACWS area ranges between 0.2 and 3·10−3 m3 (m of shoreline)−1 s−1. [Copyright &y& Elsevier]

Extreme high-temperature events pose a threat to human beings on Earth. In coastal cities, the sea breeze is widely known as a prevailing wind that can cool the near-surface air. However, the cumulative cooling effect and its attenuation process during the sea breeze penetration have not been well investigated. In this study, we analyze sea breeze cooling capacity (SBCC) and propose a new method in estimating the penetration distance of sea breeze cooling in metropolitan Adelaide during summer using data from the Adelaide urban heat island monitoring network. The results show that during a sea breeze day, wind direction rapidly changes from southeast to southwest in the morning, and it gradually returns to southeast in the afternoon. It takes 67 min on average for the sea breeze cooling fronts to penetrate inside metropolitan Adelaide. The SBCC value is 21.3 °C h per event averaged spatially in Adelaide summer. During the penetration process, the SBCC values decrease at a rate of 0.7 and 0.9 °C h per kilometer from coast to inland on an average sea breeze day and a hot sea breeze day, respectively. Correspondingly, the mean cooling penetration distances are 42 and 29 km along the prevailing wind path. A multiple linear regression analysis indicates that the distance from the coast and elevation at the onshore point together explain 88% of the spatial variability of the temporally average SBCC in the study area. The spatial pattern and penetration distance of the cumulative sea breeze cooling effect contribute to a better understanding of this common cooling source for heat mitigation in coastal cities where a large number of people reside. • For the first time, temporal and spatial patterns of sea breeze cooling in a city are characterized from observations. • The average cooling capacity is 21.3 °C h per event over the metropolitan Adelaide. • Sea breeze cooling penetrates 42 km on average and the penetration distance reduces to 29 km in a hot day. • Path distance from and elevation at the coast together explain 88% of the spatial variability of sea breeze cooling capacity. [ABSTRACT FROM AUTHOR]