| Based on the daily mean,maximum and minimum temperature in 1960-2013,hourly temperature in 1931-1940 and 2005-2014,and hourly precipitation in 1981-2015 of Shanghai Meteorological Observing Network,combined with social and economic data of urban population,electricity and land use in recent 10 years,the paper presents the characteristics and possible reasons of the urban heat island in Shanghai in different years,seasons,perimeter and day scales,and analyses the possible influence of the superposition effect of urban heat island and local circulation on urban precipitation and electricity consumption.The main conclusions are as follows:1.The enlargement of the urban heat island and the enhancement of its intensity have good consistency and synchronization with the urbanization process in Shanghai.The urban heat island decreases from Xujiahui as the center to the surrounding areas;the distribution pattern of"west high and East low"in the daytime is obvious affected by land-sea differences;the distribution pattern of"urban high suburban low"at night is obvious affected by urbanization;the intensity of the inter-decadal heat island increases significantly after 1980;the heating rate of the urban heat island intensity from 1960 to 2013 is 0.13?/10a,and from1981 to 2013,the heating rate is as high as 0.20?/10a.Using the urban-rural comparison method,it is estimated that about 28%of the surface temperature increase in Shanghai comes from the change of underlying surface,especially in winter and spring.2.Holiday effect has a certain impact on urban heat island on a weekly scale.During the Spring Festival and the Golden Week,the intensity of urban heat island decreased,mainly reflected in the change of the highest temperature during the day;during the National Day,the urban heat island decreased by 0.1?,accounting for 12.7%of the background temperature;during the Spring Festival,the urban heat island decreased by 0.13?,accounting for 14.9%of the background temperature.3.The diurnal variation of urban heat island in Shanghai has the reverse characteristics in each season:the heat island reaches the strongest in summer afternoon,and the other three seasons are several hours behind the sun;the temperature increase at Xujiahui Station in the past hundred years mainly occurs at night,the increase range can be twice as large as that in the daytime;the rate of temperature change slows down.4.Under the influence of heat island and local circulation,the"urban rain island"effect in Shanghai is significant.The spatial distribution shows a pattern of"more in the East and less in the west".The precipitation centers are located in Xujiahui and Pudong.The trend shows a pattern of"increasing in the East and decreasing in the west".The precipitation of Xujiahui Station in the central city increases at the rate of 3.45 mm/10a,while that of Songjiang Station decreases at the rate of-2.26 mm/10a.5.The precipitation has two peaks in the morning and afternoon.From the precipitation level,the precipitation of small to moderate rain level in Shanghai mostly occurs from midnight to early morning.With the increase of precipitation level,the peak value of precipitation gradually shifts to afternoon,and the peak value of extraordinary heavy rain occurs around 14:00.From the persistence point of view,the peak value of precipitation of short-duration precipitation events mostly concentrates from afternoon to evening,while the peak value of precipitation of long-duration precipitation events mostly concentrates in the morning.6.The frequency of short-term heavy rainfall and local heavy rainfall in the afternoon of Shanghai showed an increasing trend with the years,and the increment in the central urban area was larger than that in the suburbs.After 2000,the frequency of local short-term heavy rainfall increased by 89.2%and 49.5%compared with 1980's,but under the combined influence of urban heat island and local circulation,the growth rate of local short-term heavy rainfall suburban ratio was much faster than that of short-term heavy rainfall suburban ratio.Compared with 1980's,the local short-term heavy rainfall suburban ratio increased by twice in 2000's,while the short-term heavy rainfall did not change.7.Shanghai's urban electricity consumption and residential electricity consumption show an increasing trend,while industrial electricity consumption shows a decreasing trend.In a single meteorological factor,temperature and sunshine hours are significantly correlated with the change of electricity consumption.Meanwhile,the sultry index reflecting human body's perception of temperature and humidity has a greater variance explanation rate for the fluctuation of electricity consumption than that of temperature.8.Every 1?change in working day,the electricity consumption changes 14.59×10~6KW h in the same direction and 13.14×10~6KW h in weekend,every 1?increase or decrease of population-temperature index in working day,the electricity consumption increases or decreases 15.13×10~6KW h in the same direction 13.60×10~6KW h in weekend.The"population-temperature"index has higher complex correlation coefficient than the original temperature.The average temperature of 30?is the sudden change point of urban electricity consumption.The increase of urban heat island brings more pressure to urban power supply. |
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