Monitoring dryland energy and water dynamics in India: an analysis of COSMOS-India and flux tower observations

Small changes in precipitation and temperature can dramatically influence surface energy and water budgets in semi-arid regions. Quantifying land-atmosphere interactions and feedbacks in these areas is crucial to understanding global water and carbon cycles, for the development and testing of land surface, weather prediction and climate models, as well as for monitoring local water resources and agricultural output. We report the results of co-located observations of land surface water and energy fluxes and large-area soil moisture dynamics obtained at three study sites located across India. These sites were instrumented as part of the INCOMPASS (INteraction of Convective Organisation with Monsoon Precipitation, Atmosphere, Surface and Sea) and COSMOS-India projects. Two sites are located on contrasting red (Alfisols) and black (Vertisols) soils on the Deccan Plateau. A third site is installed on alluvial soils (Fluvisols) on the Indo-Gangetic Plain. Each site consists of an eddy covariance flux tower providing measurements of sensible (H) and latent heat (LE) fluxes, micrometeorology and soil physics, in combination with a COSMOS (COsmic-ray Soil Moisture Observing System) sensor that provides spatially-integrated measurements of soil water content at field scale. In this presentation, we report on feedbacks between the land surface and the atmosphere, with a specific focus on the evaporative fraction (EF=LE/LE+H), precipitation and time varying soil moisture dynamics. CEH: Ross Morrison, Jonathan Evans, Chris Taylor, Lucy Ball, Alan Jenkins, Hollie Cooper, Jenna Thornton. IISc (Indian Institute of Science): Sekhar Muddu. University of Agricultural Sciences, Dharwad: S.S. Angadi. Indian Institute of Technology, Kanpur: Sachi Tripathi, Mithun Krishnan, Geet George. University of Reading: Andrew G. Turner

The Indian COSMOS Network (ICON): validating L-band remote sensing and modelled soil moisture data products

Availability of global satellite based Soil Moisture (SM) data has promoted the emergence of many applications in climate studies, agricultural water resource management and hydrology. In this context, validation of the global data set is of substance. Remote sensing measurements which are representative of an area covering 100 m2 to tens of km2 rarely match with in situ SM measurements at point scale due to scale difference. In this paper we present the new Indian Cosmic Ray Network (ICON) and compare it’s data with remotely sensed SM at different depths. ICON is the first network in India of the kind. It is operational since 2016 and consist of seven sites equipped with the COSMOS instrument. This instrument is based on the Cosmic Ray Neutron Probe (CRNP) technique which uses non-invasive neutron counts as a measure of soil moisture. It provides in situ measurements over an area with a radius of 150–250 m. This intermediate scale soil moisture is of interest for the validation of satellite SM. We compare the COSMOS derived soil moisture to surface soil moisture (SSM) and root zone soil moisture (RZSM) derived from SMOS, SMAP and GLDAS_Noah. The comparison with surface soil moisture products yield that the SMAP_L4_SSM showed best performance over all the sites with correlation (R) values ranging from 0.76 to 0.90. RZSM on the other hand from all products showed lesser performances. RZSM for GLDAS and SMAP_L4 products show that the results are better for the top layer R = 0.75 to 0.89 and 0.75 to 0.90 respectively than the deeper layers R = 0.26 to 0.92 and 0.6 to 0.8 respectively in all sites in India. The ICON network will be a useful tool for the calibration and validation activities for future SM missions like the NASA-ISRO Synthetic Aperture Radar (NISAR)

Cosmic-ray soil water monitoring: the development, status & potential of the COSMOS-India network

Soil moisture (SM) plays a central role in the hydrological cycle and surface energy balance and represents an important control on a range of land surface processes. Knowledge of the spatial and temporal dynamics of SM is important for applications ranging from numerical weather and climate predictions, the calibration and validation of remotely sensed data products, as well as water resources, flood and drought forecasting, agronomy and predictions of greenhouse gas fluxes. Since 2015, the Centre for Ecology and Ecology has been working in partnership with several Indian Research Institutes to develop COSMOS-India, a new network of SM monitoring stations that employ cosmic-ray soil moisture sensors (CRS) to deliver high temporal frequency, near-real time observations of SM at field scale. CRS provide continuous observations of near-surface (top 0.1 to 0.2 m) soil volumetric water content (VWC; m3 m-3) that are representative of a large footprint area (approximately 200 m in radius). To date, seven COSMOS-India sites have been installed and are operational at a range of locations that are characterised by differences in climate, soil type and land management. In this presentation, the development, current status and future potential of the COSMOS-India network will be discussed. Key results from the COSMOS-India network will be presented and analysed

Spatial and temporal variability in energy and water vapour fluxes observed at seven sites on the Indian subcontinent during 2017

Under the INCOMPASS project, state of the art eddy‐covariance based surface flux measurement systems were installed at eight locations across India. These sites cover different climatic conditions, land use and land cover, and water management practices. Here we present the initial analysis of the measurements taken at seven sites mainly focusing on the year 2017, quantifying for the first time the remarkable contrasts in evaporative fraction across the seasons, climate zones and land management practices of the Indian subcontinent. With the exception of Jaisalmer which is the driest of the places studied, all the sites maintain values of evaporative fraction above 0.5 after the monsoon through to November. By contrast, for those sites with natural vegetation or rain‐fed agriculture, evaporative fraction remains below 0.3 for the dry January–May period. In the middle Gangetic Plain area, irrigation and pre‐monsoon showers together maintain evaporative fraction above 0.5 between January and June. It is also observed that different variables exhibit different intraseasonal variation characteristics even at one site. Except for Samastipur which is situated in the middle Indo‐Gangetic Plains, wind speed shows spectral peak at a smaller time‐scale compared to sensible and latent heat fluxes