The geographical environment of Xuhui District

The annual average temperature is 65438 05.5℃. The average temperature of 65438+ 10 is about 3℃ in winter, and 27.5℃ in summer and August. According to records, the extreme minimum temperature in Xujiahui was (1893) 10-19-12. 1℃ in the 19th year of Guangxu, and the extreme maximum temperature was 20 13 at 40.8℃ on August 7th. There are four distinct seasons in Xujiahui area. The average temperature is lower than 10℃ in winter and higher than 2℃ in summer, with spring and autumn in the middle.

The wind direction is often influenced by the northwest monsoon from the Mongolian plateau in winter, which is cold and dry with high wind speed, and mostly comes from the southeast wind of the Pacific Ocean in summer. 3, September and June 10 is the monsoon transition period, with more northeast winds and the least southwest winds throughout the year.

Precipitation There is more precipitation in summer than in winter, and more precipitation in spring than in autumn. There is no special dry season in the whole year, and the annual average precipitation is 1 143. 1mm, and the average precipitation in February is the least. In the fourth year of the Republic of China, there was no rain in the whole month of 65438+February. During the Meiyu period from June to July every year, the rainfall is concentrated and the precipitation is the most. In the first year of Guangxu in Qing Dynasty (1875), the precipitation in June was as high as 49 1.9 mm, and the rainstorm mainly fell in summer and autumn, with short snowfall in winter. The snow is not deep, and the number and frequency of hail are few.

There is plenty of water vapor in fog and frost, and there are many condensation nuclei in the air, with low wind speed and more foggy days. According to the statistics of Xujiahui Meteorological Observatory, the average foggy day is about 43 days per year, with a maximum of 93 days in the Republic of China 19 and a minimum of 3 days in the 27 th year of Guangxu in Qing Dynasty. Fog is easy to appear in windy and cloudless nights and mornings in June 5438+0 ~ May and June 5438+00 ~ February. The territory is flat and vulnerable to the cold wave. When the cold wave comes, the temperature drops sharply, causing frost in early spring and late autumn, endangering crops. The average first frost date is165438+1October 20th, and the average last frost date is April 24th. The annual average frost period is about 125.4 days, and the frost-free period is about 240 days.

Disastrous weather is mainly affected by tropical storms (typhoons), tornadoes, heavy rains and hail. Typhoons hit Shanghai in July and August, followed by June and September, about twice a year on average. On July 28th, 2004, the typhoon blew the anemometer of Xujiahui Observatory with the maximum wind speed of 44 meters per second. 1On the night of July 24th, 949, a typhoon and rainstorm hit Shanghai, causing serious disasters. According to incomplete statistics, 665 houses collapsed in the south of Zhaojiabang, affecting 50/kloc-0 households with 2389 people, 85 people died and more than 40 people were injured. 1956 12 typhoon blew down the steel cross of Xujiahui Catholic Church, reaching as high as 1 m and weighing about 400 kg. Tornadoes often appear between summer and autumn. 1On the morning of September 6th, 962, a tornado went straight to Longhua, skimmed Longhua Building, swept the northwest, pulled up telephone poles and houses, and caused great losses to crops, people and animals. Rainstorms mainly occur in summer and autumn. 1 September 96313rd, there was a rainstorm of 246.7mm in Longhua ..1August 5, 969, and there was a rainstorm of 204.4 mm in Longhua, of which1hour had a maximum rainfall of 7 1.2 mm, with/kloc-0. There is little hail in this area. According to the Records of Songjiang Prefecture in Jiaqing Period of Qing Dynasty, "On April 8th, the first year of Yongzheng (1723), it rained heavily and hail, with the maximum amount reaching 50 Jin. From Longhua to Zhagang, one person died and countless people were injured. "