The geographical environment of Fancheng District

Fancheng District belongs to the northern subtropical monsoon climate zone, with the characteristics of transition from north to south. Cold winters and hot summers, four distinct seasons, sufficient light energy, rich heat, long frost-free period, moderate precipitation, rain and heat in the same season, and a relatively mild climate.

Sunshine

The annual average sunshine hours in Fancheng District are 1800 to 2100 hours, the sunshine percentage is 41% to 48%, and the total annual radiation is more than 101 to 110 kcal/cm2 between. The annual variation of sunshine is bimodal. There is a high peak in August and another high peak in October. The sunshine hours in summer account for 34% of the total annual hours, and the sunshine hours from June to August are more than 200 hours; the sunshine hours in winter are short, accounting for 19% to 20% of the annual sunshine hours; the sunshine hours in spring are relatively The number of sunshine hours in autumn is about 190 more.

Temperature

The average temperature in Fancheng District over the years is 15℃~16℃. The annual variation in temperature is highest in July and lowest in January. The temperature is generally 2℃~3℃ from December to February, 15℃~16℃ from March to May, 27℃~28℃ from June to August, and 16℃~17℃ from September to November. The diurnal variation of temperature is unimodal. The longest daily temperature is generally between 15:00 and 16:00. The time when the daily minimum temperature occurs varies with the season. The earliest in July is at 5 o'clock; the middle period from April to October is at 6 o'clock; the latest in winter is between 7 and 8 o'clock. The annual average daily temperature range is generally around 8 to 10°C, with the maximum in June at 11.6°C and the minimum in September at 9.5°C.

Frost-free period

The first frost day generally occurs in mid-November; the last frost day generally occurs in mid-to-late March. The average number of frost days is 50 in many years, and the frost-free period is between 228 and 249 days.

Precipitation

The annual precipitation in Fancheng District is generally between 800 and 1100. The inter-annual variation is significant, reaching more than 1200 mm in rainy years and only about 500 mm in dry years. Precipitation is unevenly distributed throughout the year, with more precipitation in summer, less in winter, and slightly more precipitation in spring than in autumn. The most precipitation occurs in July and August, accounting for about 32% of the annual precipitation; the intensity is high, with the monthly average reaching 10.8 to 15.4 mm/day. Snowfall usually begins in late November or early December. Snow breaks usually in early or mid-March. The average number of snowfall days over the years is 13, with a maximum of 28 days (from the end of 1956 to the beginning of 1957) and a minimum of 3 days (from the end of 1960 to the beginning of 1961).

Wind

The seasonal changes in wind direction in Fancheng District are obvious. In winter, the high pressure in Mongolia is strong, and Fancheng is located in the southeast of the high pressure, so northerly winds prevail on the ground. In summer, the high pressure moves to the Pacific Ocean east of the mainland, so the wind direction is mostly southerly. From September to February of the following year, northerly winds prevail, and from March to August, southerly winds prevail. Wind direction and wind speed are affected by the terrain and are caused by the narrow tube effect of the north-south Hanshui River. The average wind speed is the highest in spring, generally above 3 meters/second; the average wind speed is the smallest in autumn, generally no more than 2.5 meters/second. The number of days with level 8 gales is more common in spring, followed by summer, and the least in autumn. The average number of windy days throughout the year is 4 to 5 for many years.

Disastrous weather

Disastrous weather that affects industrial and agricultural production includes drought, floods, cold damage, freezing damage, strong winds, hail, etc.

Drought is the most common disaster and may occur throughout the year. Summer drought and autumn drought are the most serious, and consecutive droughts in summer and autumn are even more harmful. Consecutive droughts in summer and autumn usually occur only twice in five years. Generally, droughts occur every year, with an average of 1.5 to 2 times a year; severe droughts occur once every three years, moderate droughts occur once every two years, and severe droughts occur approximately once every 8 to 10 years.

Floods basically occur from April to October, and the concentrated period is from June to July. Fancheng District is prone to flood disasters because it is located in the transition zone between the north subtropical monsoon climate and the temperate climate, with both north and south climate characteristics. Heavy rains in this area are mainly caused by the convergence of southeast and northwest airflows in summer, the eastward movement of the southwest vortex in autumn, the influence of typhoons penetrating into the interior, and local convection that produces heavy rains and floods. According to the source of floods, in addition to local heavy rain floods, transit floods account for a considerable proportion.

Low temperature freeze damage in early spring generally occurs from late February to early April, with an average of 4 to 6 times per year. Continuous rains in spring are concentrated from mid-April to early May, with an average of about two times a year, and long-term continuous rains occur once every two years on average. In autumn, continuous rains mostly occur in mid-September. Autumn cold (daily average temperature is less than 20°C) begins to appear in mid-to-late September. Cold air activities occur on average 5 to 6 times a year from September to October. Cold waves occur most often in November. The frequency of cold air is generally five times every two years; the frequency of cold waves is two times every five years.

Strong winds and hail are disastrous weather conditions in local areas, and cold wave gales and thunderstorms often occur. In spring, cold air moving southward is usually accompanied by rain and strong winds, and sometimes "floating dust" (yellow sand) appears, which is more harmful to the growth of crops such as silkworms, peas, and wheat. Hail mostly occurs in spring and summer. In spring, it is mostly regional hail, and in summer, it is mostly local hail. Summer hail accounts for about 53% of the annual hail.