Urban warming in Japanese cities and its relation to climate change monitoring

Abstract

This article briefly reviews urban warming studies in Japan, where many of the stations established by the beginning of the 20th century are located in cities that have undergone rapid industrialization. The recorded rate of temperature increase is a few degrees per century in large cities and tends to be larger at night than during the daytime. In some cities, the increase in annual extreme minimum temperature exceeds 10°C century −1 . On the other hand, recent numerical studies have revealed widespread urban warming around Tokyo and other megacities during afternoons of the warm season as a result of extensive urbanization that enhances daytime surface heating. An analysis using data from the dense Automated Meteorological Data Acquisition System network has shown that an urban bias in recent temperature trends is detectable not only in densely inhabited areas but also at slightly urbanized sites with 100-300 people km −2 , indicating the need for careful assessment of the background climate change. There is also some evidence of microscale effects on observed temperature, as revealed by an analysis of the relationship between trends in temperature and wind speed.

Changes in terrestrial near-surface wind speed and their possible causes: an overview

“…Relatively greater wind speeds (i.e., > 1.5 m s −1 ) in Japan are negatively correlated with temperature, and lower wind speeds (i.e., < 1.0 m s −1 ) are positively correlated with temperature during daytime (Fujibe 2009). Fujibe (2011) found a negative correlation between SWS changes (ΔU) and air temperature changes (ΔT), and this correlation is more significant for lower wind speeds. Similarly, a negative correlation between SWS and air temperature in South Korea prior to 2003 has also been reported by Kim and Paik (2015).…”

Evolution of the Parisian urban climate under a global changing climate

“…On the other hand, it is expected that these global trends will be more marked at the city scale due to the urban processes such as urban heat islands (UHIs). Moreover, several studies already displayed a significant urban signal that tends to reinforce the increase trends detected in the temperature historical time-series (Jones et al 1990;Wilby 2003;Gaffin et al 2008;Fujibe 2011). During future decades, the complex interactions between the effects of global change at regional scale and the evolution of cities themselves (coupling urban growth and increase in population) will probably lead to a deep change of urban climate.…”

Possible Urban Bias in Gridded Climate Temperature Data over the Japan Area

“…Fujibe (2009Fujibe ( , 2010 found the existence of anomalous warming even for stations with P = 100− 300 km −2…”

“…In some regions, however, anomalous warming at urban stations in comparison to nearby rural sites has been found (Hansen et al 2001;Choi et al 2003;Lim et al 2005;Ren et al 2008;Lai and Cheng 2010). Urban warming is quite conspicuous in cities in Japan, where anomalous temperature trends are detectable not only at stations in large cities but in small cities and towns (Fujibe 2009(Fujibe , 2010Nishimori et al 2009). …”