RH and UHI Relative Humidity 7.76g 14.8g 27.69g Urban Heat Islands Effects first discovered in 19 th Century (why??) First detailed by Chandler in 1965 Mainly night time effect City is on average 3-4 oC higher Generally temperatures grow towards the inner city Varies over different land uses Parks etc Density of buildings Purple = Richmond Park Changes in UHI Less Pronounced (less pollution, clean air act 1956, catalytic converters in cars, electric trams, less coal used in homes) Building materials (higher albedos) City planning (density of buildings) Less heavy polluting industry CITY SIZE Effects of UHI Vegetation flowering?? Heating and cooling systems More time outside?? pavement cafs UHI Los Angeles 1930 area covered with orchards, ave summer temp 97 oF 1990s av summer temp 105 oF