Global Dynamics of Stored Precipitation Water in the Topsoil Layer From Satellite and Reanalysis Data

Abstract

The amount of soil water in the topsoil layer (from 0 to 10 cm) has been regarded as a key factor in controlling land‐atmosphere interaction by determining the fraction of net radiation. In the present study, we investigate spatial trends of the stored precipitation fraction in the topsoil layer for varying vegetation and aridity indices by utilizing four satellites and two reanalysis data sets on a global scale. Using the Budyko framework, we relate climate regimes to the stored precipitation fraction on a global scale. A positive relation between the stored precipitation fraction with aridity index and a negative relation between the stored precipitation fraction and free parameter, vegetation optical depth, and isohydric slope are discovered. Even though the stored precipitation fraction values were calculated from different soil moisture and precipitation sources, they share an similar spatial trend: the drier and less vegetated the soil is, the more precipitation is retained in the top layer of the soil. Specifically, the topsoil retains 37% ± 11% of precipitated water three days after a rainfall event where the aridity index was greater than 5. Over wet and forest areas, due to large runoff fluxes and plants intercepting water before the precipitated water reached the ground, the topsoil retains 21% ± 2% of precipitated water three days after a rainfall event. Furthermore, by using the modeled data sets in the calculation of the stored precipitation fraction metric, we are able to conduct a sensitivity analysis of FP(f) metrics with respect to different sampling frequency values.

Hydrological Basis of the Budyko Curve: Data‐Guided Exploration of the Mediating Role of Soil Moisture

“…The result shows a power law relationship between the two variables. Similar climatic control on soil moisture has also been reported in previous studies (Gu et al, 2019; Kim & Lakshmi, 2019; Seneviratne et al, 2010). The observed power law relationship indicates that the equilibrium soil moisture is itself an emergent property that presumably reflects the balance between available energy and available water through interactive effects of climate, soil, vegetation, and topography, as indicated by Eagleson (1978), although Eagleson himself did not invoke the aridity index at the time.…”

The Role of Irrigation Expansion on Historical Climate Change: Insights From CMIP6

“…Despite the clear climate and water cycling impacts of historical and future irrigation ( de Vrese & Stacke, 2020;Hurtt et al, 2020;Lawrence et al, 2016), it has generally not been considered in evaluations of drivers of observed climate change (Thiery et al, 2020). The role of irrigation on land-atmospheric coupling and land surface model initialization has been demonstrated in several studies (H. Kim & Lakshmi, 2019;Lawston et al, 2015;Lu et al, 2015Lu et al, , 2017Pryor et al, 2016). Lu et al (2017) found that irrigation led to a significant decline in coupling strength between the irrigated land and the atmosphere in the Midwestern United States.…”

Soil Moisture Memory of Land Surface Models Utilized in Major Reanalyses Differ Significantly From SMAP Observation

“…(2017) has demonstrated a global median estimation of 0.14, that is, a thin 50 mm soil layer (SMAP's nominal detecting depth) can retain approximately 14% of the precipitation falling on land. Subsequent studies have since referred to this amount as a benchmark to evaluate $${F}_{p}$$ in varying soil and climate conditions or how $${F}_{p}$$ will change in the future climate (Kim & Lakshmi, 2019; Liu et al., 2021; Martínez‐Fernández et al., 2020). However, since SM and precipitation both show annual variabilities, and the original SMAP products can contain larger noises compared to recent SMAP versions using an improved algorithm (e.g., Dual Channel Algorithm, Multi‐Temporal Dual Channel Algorithm [MTDCA]; Konings et al., 2016), it is necessary to examine the robustness of $${F}_{p}$$ distribution originally reported in McColl, Alemohammad et al.…”