Climatic characteristics of liushi

The annual average temperature is 65438 07.7℃. The hottest is August (or late July), with an average monthly temperature of 27.8℃. The coldest month is 65438+ 10 (or 65438+in late February and early February), and the monthly average temperature is 7.4℃. The historical extreme maximum temperature is 36.05℃; Extreme minimum temperature -5.35℃.

The temperature is high in the south and low in the north. The temperature in the built-up area is high, and the temperature in the northern, northwest and northeast mountainous areas is low. Statistics of the start and end of the four seasons and the number of days: the start and end days in spring are about February 28th, May 27th, 89th, summer is about May 28th, 10, 127, autumn is about 10, February 2nd, 10, 8/kloc. Winter is about 65438+February 22nd, and February 28th is about 68 days. It shows that climatology usually adopts the average temperature, that is, the daily average temperature of five consecutive days 10℃ and 22℃ as the boundary temperature of climate seasonal change. The annual temperature is less than 10℃ in winter and more than 22℃ in summer, which is between spring and autumn. There is plenty of rain in liushi. Water resources are abundant, but they are unevenly distributed in time and space. In terms of time, the rainy season in May and June is the most rainy, followed by the spring rain season in March and April. July-September is a period of frequent typhoons and thunderstorms. Without a typhoon, it is easy to form a drought. If a typhoon strikes, there will often be heavy rain, and the rainfall will be concentrated, causing disasters.

The spatial distribution of precipitation is also uneven. Affected by topography, the annual rainfall in mountainous areas is the most, and the rainfall in plain hills is less.

The average annual rainfall is1567.5mm. The maximum annual rainfall (1973) after the founding of the People's Republic of China is 9 13mm. The minimum annual rainfall (1979) after the founding of the People's Republic of China is 9 13mm.

The precipitation in Liushi is greatly influenced by the area under its jurisdiction and the surrounding terrain, and the rainfall isoline presents topographic effect. The seasonal trend of precipitation is rainy in summer and dry in winter, which is relatively concentrated in spring and summer. The main types of precipitation are frontal rain, typhoon rain and thermal thunderstorm. Characteristics of precipitation in Liushi area Precipitation characteristics in rainy season During the spring rain in March and April, warm and humid air masses in the south met with cold air masses in the north, forming frontal rain. Rainfall is equivalent to the sum of autumn and winter. During the Meiyu period from May to June, the southern moisture mass moved northward again, confronting the north and south cold air masses, bringing a lot of precipitation. This is for the rainy season. Rainfall is the sum of the other three seasons. July-September Typhoon Thunderstorm Period In the midsummer of July and August, except for thunderstorms around the evening, it is mainly sunny and hot weather, which is prone to drought. Typhoon activity is frequent from July to September, which is easy to bring showers and heavy rains. Precipitation is concentrated, sudden, short-lived, abundant and abundant. It is easy to cause wind disasters and floods. 65438+ 10 to February of the following year is obviously controlled by the cold and high pressure polar continental air mass in the north. It's sunny and cold with little rain, frost, sometimes snowfall, and sometimes freezing in the north, northwest and northeast. The main source of surface water resources is precipitation. For mountainous and hilly areas, the surface water resources are equal to the average runoff for many years MINUS the shallow groundwater resources; For the plain area of Liushi, the amount of surface water resources is the average annual runoff for many years.

The groundwater resources in Liushi are mainly pore confined water of loose rock pore water. There are two confined aquifers buried with the depth of 67.6-78.9 meters respectively, and the water quality is weak. The recoverable water quantity of single well in the first layer is 1849.64 tons/day, and that of single well in the second layer is 10 1.96 tons/day. Shallow water is slightly salty, with salinity of 1. 1.79g/L, which can be used as irrigation water. In addition, there is pore fissure water in the red bed. The groundwater in the south is influenced by seawater, and the water quality is salty and can't be drunk. The utilization of groundwater resources is mainly weir, spring well and civil motor well to solve the irrigation and domestic water use of some farmland. It is widely used, but the utilization rate is not large enough.

Evaporation: land evaporation is not easy to measure and is usually calculated according to water balance. The evaporation of water surface decreases with the elevation of topography, that is, the annual evaporation of water surface decreases by about 20-30 mm for every elevation of topography 100 m. The water surface evaporation in Liushi is larger in June-65438+1October, and smaller in June-1-May of the following year. The maximum is in July and August, and the minimum is 65438+ February-February of the following year. The annual average water surface evaporation is 1283.5 mm.

Relative humidity: the average relative humidity in Liushi for many years is 8 1%. Wet from April to August, with an average of more than 83% per month; The largest in June, reaching 88%; 65438+1October-65438+1October of the following year is about 74%.

Fog condition: The fog season in Liushi is from late spring to early summer, 10 to March of the following year 165438+. The average foggy days for many years are 17.8 days. There are more advection fog and less radiation fog.

Wind condition: the dominant wind direction in Liushi is southerly wind and easterly wind, followed by northwest wind and southeast wind; Strong winds are southeast wind and north wind. East wind and southeast wind predominate in summer and west wind and north wind predominate in winter. The annual average wind speed in Liushi is 2.8m/s, and the annual maximum wind speed is 28m/s. ..

Frost period: the first frost date is about165438+1October 25th, and the final frost date is about February 27th of the following year. The frost-free period is 270 days.