Search

Soil moisture (SM) plays a crucial role in altering climate extremes through complex land-atmosphere feedback processes. In the present study, we investigated the impact of SM perturbations on temperature extremes (ExT) over India for the historical period (1951–2010) and future climate projection (2051–2100) under 4 K warming scenario. We note that more than 70% area of the Indian landmass has experienced significant changes in characteristics of ExT due to SM perturbations. In particular, we see larger impact of SM perturbations on ExT over the north-central India (NCI), which is a hotspot of strong SM-temperature coupling. Over NCI, a 20% departure in SM significantly revamps frequency, duration and intensity of ExT by 2–5 events/year, 1-2 days/event and 0.5–2.1 °C, respectively, through modulating surface energy partitioning, evapotranspiration and SM memory. Importantly, the impact of SM perturbations on frequency and duration of ExT events becomes less prominent with intensification of global warming. [ABSTRACT FROM AUTHOR]

[Display omitted] • COSMOS-IITM facilitates high-frequency area-averaged SM across core-monsoon-zone. • Inimitable impacts of multiscale rainfall features on COSMOS-IITM SM are remarkable. • ERA5 and GLDAS SM products are coherent with that of COSMOS-IITM. This study presents an analysis of daily field-scale soil-moisture (SM) variations, measured using the COsmic-ray Soil Moisture Observing System (COSMOS), over a tropical monsoon site (IITM, Pune) in India, for the period 2017–2020. Being located in the core zone of the Indian summer monsoon, the daily field-scale SM observations at COSMOS-IITM provide an unique opportunity to understand the SM response to monsoon precipitation variations on sub-seasonal, seasonal and interannual time-scales. In addition to the COSMOS-IITM observations, we also evaluated SM variations over this location using satellite, reanalysis and model products for the same period. An important result from our analysis reveals the presence of biweekly (time-scale ~ 10–20 days) and low-frequency intra-seasonal (time-scale ~ 30–60 days) variations in the field-scale SM, which are linked to the dominant modes of Indian summer monsoon subseasonal variability. In particular, we find a pronounced enhancement of the low-frequency signal of SM variations during the 2019 monsoon which was characterized by abnormally excess precipitation and prolongation of rains well beyond the summer monsoon season, in contrast to 2018 monsoon. Moreover, this study highlights a longer persistence of SM memory time-scale (about 60 days) during 2019 as compared to 2017, 2018 and 2020. The validation of coarser resolution data sets revealed that GLDAS and ERA5 reasonably capture a range of observed field-scale SM variabilities over COSMOS-IITM site. [ABSTRACT FROM AUTHOR]

• Soil moisture-temperature coupling is stronger over the monsoon dominated regions of north-central India (NCI). • Significant increase of temperature extremes over NCI is dominantly influenced by soil moisture drying. • Decrease of evapotranspiration and soil moisture memory is conducive for drying of soil moisture. Soil moisture (SM) and near-surface temperature variations are known to be linked through land–atmosphere interactions. While previous investigators have examined the association between temperature extremes and large-scale atmospheric circulation variability, the role of land–atmosphere coupling on temperature extremes over the monsoon-dominated region of India is not well understood. This study presents an analysis of hydro-meteorological datasets for the 67-year period (1948–2014) to assess the impact of long-term soil moisture changes on temperature extremes over the Indian region. Firstly, our findings show that the hot-spot of land–atmosphere coupling located across north-central India (NCI) is a region where SM variations can significantly influence temperature extremes. We further note that the NCI region experienced a significant declining trend in SM (about 1.1 mm/decade) during 1948–2014, in association with the decreasing trend of monsoon precipitation. Our findings suggest that the long-term decrease of SM over the NCI has favored increased incidence of temperature extremes through strengthening (weakening) of sensible (latent) heat fluxes; while the loss of soil moisture memory has additionally promoted increased variability of temperature extremes. The frequency, duration and variability of extreme temperatures are found to increase significantly by 1–2 occurrences, 5–6 days and 43%, respectively, in association with a decrease of 10 mm SM over NCI. The Generalized Extreme Value (GEV) distributions are fitted to extreme temperature duration (ExTD) using SM as a covariate to quantify the role of SM on temperature extremes over NCI. GEV analysis reveals that drier SM conditions (10th percentile) lead to an increase in the 67-year return value of ExTD by 9–10 days, relative to wet SM conditions (90th percentile) over NCI. Furthermore, it is interesting to note that the rise in temperature extremes over NCI in the recent three decades has been more prominent during the monsoon and post-monsoon seasons as compared to the pre-monsoon months. [ABSTRACT FROM AUTHOR]