Climate characteristics of Hangzhou

Climate characteristics of Hangzhou

Hangzhou is located in the transition zone of the central and northern subtropics. It is warm and humid, with four distinct seasons, sufficient sunshine and abundant rainfall. Throughout the year, with the reverse conversion of winter and summer monsoons, the weather system, controlled air mass and weather conditions will undergo obvious seasonal changes, forming climate characteristics of rainy spring, hot and humid summer, cool autumn air, and dry and cold winter. Due to the complex landform types and wide disparity in terrain, Hangzhou City has uneven regional distribution of light, heat, and water, and some areas are rich in microclimate resources. However, due to the instability of the monsoon's advance and retreat time and sustained intensity, anomalies of cold, heat, dryness, and humidity often occur, leading to disastrous weather.

1. Insolation and sunshine

The average annual total solar radiation in Hangzhou is between 100 and 110 kcal/cm2, the sunshine hours are 1800 and 2100 hours, and the sunshine percentage ( The ratio of the actual sunshine hours to the theoretical sunshine hours in a certain period of time is 41 to 48%. In terms of geographical distribution, there are more plains than mountainous areas. To the north of Tonglu and Fuyang, Xiaoshan, Yuhang and the northeastern part of the urban area, the terrain is flat and the sunshine is sufficient. The annual average total solar radiation is more than 108 kcal/cm2, the sunshine hours are more than 2000 hours, and the sunshine percentage is more than 45%. It is a high-value area in the city. The city is located in the river valley plain in the central part of Luyu, the Xin'anjiang Reservoir area and the eastern part of Lin'an County. The annual average total solar radiation is 106-108 kcal/cm2, and the sunshine hours are 1950-2000 hours. The percentage is about 45%. In hilly and mountainous areas, due to terrain obstruction and more clouds, fog, heat and thunderstorms, the lighting is poor. The annual average total solar radiation is generally below 100 kcal/cm2, the sunshine hours are less than 1900 hours, and the sunshine percentage is less than 41%. In mountain ridges In Narrow dock, the sunlight and sunshine are only about 70% of those in the plain.

According to the observations of the Tianmu Mountain Weather Station, the insolation and sunshine in mountainous areas become weaker and shorter as the terrain increases below 500 meters above sea level. At an altitude of 500 to 1,000 meters, the lowest temperature occurs due to more clouds and rain. Value; above 1,000 meters above sea level, it becomes stronger and longer as the terrain rises. The seasonal changes in insolation and sunshine in Hangzhou are obvious. The total solar radiation, sunshine hours and sunshine percentage in the summer half of the year (May to October) are greater than those in the winter half of the year (November to April of the following year). Among them, the two months of midsummer, July and August, have strong sunlight and long sunshine. Except for mountainous areas, the monthly average total solar radiation in most areas of the city is 12.5 to 14.5 kcal/cm2, the sunshine hours are 230 to 260 hours, and the sunshine percentage is 55 to 60% or above. In winter, the solar radiation is weak and the sunshine is short. The average total radiation amount in each month from December to February is below 6 kcal/cm2, the sunshine hours are less than 150 hours, and the sunshine percentage is less than 50%. Spring (March-April) and autumn (September-October) are transitional seasons, with sunshine and sunshine amounts in the middle. In contrast, spring has more cloudy and rainy weather, and each value is smaller than that in autumn. The only exception is the top of Tianmu Mountain. Except for July and August, the average sunshine hours are also more in every winter month. From November to January of the following year, the sunshine percentage exceeds 50%.