Abstract: Based on the records of thunderstorms and temperatures in 26 weather stations in Guangdong Province from 1960 to 2013, with the climate trend coefficient analysis, MannKendall mutation test, Morlet wavelet analysis, EOF analysis and the contrasting method between suburban and urban weather stations, we analyzed the climatic characteristics of thunderstorms in Guangdong and the influences of urban heat island effect on thunderstorms in the Pearl River Delta region. Our study showed that there were more days of thunderstorms in the west than in the east, with the average days of thunderstorms being 74.3 d per year, mainly occurring between April and September. The days of thunderstorms decreased by 0.43 d·a^-1 after the year 1984, with a faster decrease in the west than in the east of the province and the Pearl River Delta region. The annual average number of days with thunderstorms showed long time period cycles of 9-12 years and 21-22 years, and short cycles of 2-3 years and 4-5 years. There existed three modes of spatial anomalies in the province, i.e., accordant, different between east and west, and different between north and south. The heat island effects in the cities of Guangzhou and Shen-zhen since 1984 had become stronger, showing close relationships with thunderstorm days, and with the climate trend coefficients of 0.4936 and 0.3937 for the two cities, respectively. Thus, the urban heat island effect caused by urbanization may to certain extent have increased the number of thunderstorms in the cities of the Pearl River Delta region.

Key words: N₂O emission, nitrogen application, ammonia volatilization, vegetable field, nitrogen application rate.