Changes of Instrument-measured Evaporation and Its Response to Climate Change in Heilongjiang Province

In this study, instrument-measured evaporation and conventional meteorological observations from 80 stations in Heilongjiang Province from 1961 to 2020 were collected. Using these data, methods such as linear trend estimation, cumulative anomaly, multiple linear regression, and Morlet wavelet analysis were employed to analyze the changes of instrument-measured evaporation annually and seasonally in Heilongjiang Province. Additionally, we analyzed its response to climate change. The results showed that from 1961 to 2020, annual pan evaporation in Heilongjiang Province showed a significant downward trend, decreasing at 10.5 mm per decade. Evaporation decreased significantly in spring, while the magnitude of this decrease in summer and autumn was relatively small, and evaporation increased significantly in winter. In the periodic change, annual and seasonal evaporation have significant periods on short time scales. Among them, PEy and PESu mainly have a short period of 3-4 years, PESp has short periods of about 3 years and 6 years, PEA mainly has short periods of 2 years and 3 years, and PEW mainly has short periods of about 4 years.The geographical correlation of evaporation was significant, with evaporation decreasing as latitude, longitude, and altitude increased. Additionally, we found that changes in annual and seasonal pan evaporation were positively correlated to changes in average temperature, hours of sunshine, and wind speed, and negatively correlated to changes relative humidity. Our analysis indicates that a significant decrease in wind speed and hours of sunshine is the dominant factor leading to the decrease in evaporation throughout the year as well as in spring, summer, and autumn, while higher temperatures and lower relative humidity may lead to a significant increase in evaporation in winter.