Spatial pattern of amount effect of daily precipitation isotopes in China: A consideration of seasonality based on observation and simulation

Abstract

The negative correlation between precipitation amount and precipitation δ¹⁸O, also known as the amount effect, is considered one of the main environmental controls of precipitation isotopes. As isotope observations increase, there is a debate about the spatial patterns of amount effect especially on a daily scale. Based on observations at 150 sampling stations and an isotope-enabled climate model, here we examined the amount effect of precipitation isotopes across China from humid to arid climate conditions. The observations and simulations indicated that the spatial distribution of amount effect of daily precipitation isotopes for each season is not limited to the traditional low latitudes. When the seasonality of precipitation isotopes is filtered or reduced, the areas with amount effect on a daily scale are enlarged. On a daily scale, there is a spatially coherent amount effect in summer, while in other seasons some areas without an amount effect can also be observed, especially in the northeastern part of China in winter. Except for summer, the precipitation extremes do not always lead to isotope depletion, which may be related to relatively higher temperatures during precipitation extremes in these areas. After the seasonality is eliminated, as the time scale increases from daily to monthly and annual scale, the spatial patterns of amount effect are generally similar. The seasonality of spatial patterns of amount effect is associated with atmospheric circulation. The findings provide a perspective of seasonality removal to understand the amount effect of precipitation isotopes, and are useful for understanding the changing isotope signatures in an accelerated hydrological cycle.