Analysis on the Seasonal Characteristics of Water and Heat in Fujian Province from 1957 to 2011

Potential evapotranspiration and precipitation are two important indicators of the hydrological balance of a watershed, and their intra-annual and multi-year seasonal variation characteristics have an important impact on the hydrological balance. In this paper, based on the daily meteorological data of 23 meteorological stations in Fujian Province from 1957 to 2011, the daily potential evapotranspiration was estimated by using the Penman-Momteith formula and fitted with a sine function to obtain the amplitude, peak phase and time to peak of evapotranspiration to measure the regional The seasonal variation of potential evapotranspiration was measured. Three seasonal indicators, namely precipitation seasonality index, peak phase time and rainy season length, were introduced to characterize the seasonal characteristics of precipitation. The study shows that the potential evapotranspiration in Fujian Province is generally decreasing, with a decline of 30 mm/10a-130 mm/10a. The multi-year average precipitation in Fujian Province is 1590.19 mm, with an increase of 50–200 mm per decade, and the annual average amplitude shows a clear latitudinal band distribution, with a significant decrease in amplitude with increasing latitude. The peak time of the year occurs as early as mid-July on the southeast coast, increasing from the southeast coast to the northwest mountains, with some variation in the spatial distribution of the bands in Fujian Province, influenced by the number of sunshine hours. The seasonal index of precipitation has shown a significant downward trend over the past 55 years, characterising a decrease in regional differences in wet and dry conditions and a tendency for intra-annual rainfall distribution to become more even. Peak precipitation in Fujian Province occurs as early as early June in the northwest, extending and expanding to the southeast, and as late as late June in the south and southeast due to the influence of the marine monsoon and typhoons. The length of the rainy season reaches nearly three months in central and northeastern coastal areas of Fujian Province, due to the influence of the subtropical monsoon in early June and the typhoon in August. This paper explores the changes and trends in the seasonal characteristics of water and heat in Fujian Province, which will provide a basis for the impact of seasonal changes on the water and heat cycle in Fujian Province.