Seasonal variation of evapotranspiration and its effect on the surface energy budget closure at a tropical forest over north-east India

This study uses one year of eddy covariance flux observations to investigate seasonal variations in evapotranspiration and surface energy budget closure at a tropical semi-deciduous forest located in north east India. The annual cycle is divided into four seasons, namely: pre-monsoon, monsoon, post-monsoon, and winter. The highest energy balance closure (76%) is observed during pre-monsoon, whereas the lowest level of closure (62%) is observed during winter. Intermediate closure of 68% and 72% is observed during monsoon and post-monsoon seasons, respectively. Maximum latent heat flux during winter (150 W m-2) is half of the maximum latent heat (300 W m-2) flux during monsoon. Evapotranspiration is a controlling factor of surface energy budget closure, with highest rates of closure corresponding to the periods of highest evapotranspiration. The Bowen ratio ranges from 0.93 in winter to 0.27 during monsoon. This is the first time the role of evapotranspiration in the seasonal variation of surface energy budget closure has been reported for any ecosystem in north-east India using eddy covariance measurements

A case study of turbulence in the nocturnal boundary layer during the Indian summer monsoon

Observations from the Cloud-Aerosol Interaction and Precipitation Enhancement Experiment-Integrated Ground Observation Campaign (CAIPEEX-IGOC) provide a rare opportunity to investigate nocturnal atmospheric surface-layer processes and surface-layer turbulent characteristics associated with the low-level jet (LLJ). Here, an observational case study of the nocturnal boundary layer is presented during the peak monsoon season over Peninsular India using data collected over a single night representative of the synoptic conditions of the Indian summer monsoon. Datasets based on Doppler lidar and eddy-covariance are used for this purpose. The LLJ is found to generate nocturnal turbulence by introducing mechanical shear at higher levels within the boundary layer. Sporadic and intermittent turbulent events observed during this period are closely associated with large eddies at the scale of the height of the jet nose. Flux densities in the stable boundary layer are observed to become non-local under the influence of the LLJ. Different turbulence regimes are identified, along with transitions between turbulent periods and intermittency. Wavelet analysis is used to elucidate the presence of large-scale eddies and associated intermittency during nocturnal periods in the surface layer. Although the LLJ is a regional-scale phenomenon it has far reaching consequences with regard to surface-atmosphere exchange processes

Statistical Analysis of the Precipitation Isotope Data with Reference to the Indian Subcontinent

The isotopic analysis of precipitation provides useful information on a variety of hydrological and atmospheric processes. The dynamical characteristics of precipitation isotopes have been well investigated, but a systematic study of their statistical behavior seems to be lacking. We have performed the statistical analysis, basically the distribution characteristics of precipitation isotopes vis-a-vis rainfall data for specific regions. The probability distribution functions of precipitation isotopes have been calculated from local to global scales. It has been observed that the isotopic values, in general, followed a pattern that is similar to the normal distribution, though the rainfall distribution patterns are very different. Under certain circumstances, the isotopic distribution patterns closely resemble the normal distribution, implying a well-constrained moisture source contributing to precipitation. The distribution patterns of oxygen and hydrogen isotopes on continental and global scales show similar behavior. It was observed that the distribution patterns of primary isotopic variables (δ18O and δD) are not very sensitive to the outliers. On the contrary, the secondary parameter, d-excess, is very sensitive to outliers, which offers an effective means to quality control of the precipitation isotopic values

Carbon, water and energy fluxes at the subtropical forest in Kaziranga National Park in India

<p>This dataset contains measured and modeled records of gross primary productivity (GPP), sensible heat flux and latent heat flux from 2016 to 2018 at the Kaziranga National Park, India. The measured fluxes are obtained from eddy covariance technique at the flux tower established by the Indian Institute of Tropical Meteorology (IITM) Pune as part of the MetFlux India network funded by the Ministry of Earth Sciences (MoES), the Government of India, whereas the Integrated Science Assessment Model (ISAM) at the Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, Illinois, USA is used to simulate these fluxes. Additionally, the leaf area index (LAI) and meteorological measurements used as the model input are also included in this dataset. </p&gt

Linkage between precipitation isotopes and biosphere-atmosphere interaction observed in northeast India

© 2022, The Author(s).The intra-seasonal variation in precipitation isotopes shows a characteristic declining trend over northeast India. As of now, no mechanism offers a consistent explanation of this trend. We have performed the isotopic analysis of precipitation (rain) and estimated net ecosystem exchange and latent heat fluxes using an eddy-covariance system in northeast India. Additionally, we have used a diagnostic model to determine the recycled rainfall in this region. We find a strong link between the enhanced ecosystem productivity and isotopic enrichment in rainwater during the premonsoon season. Subsequently, on the advent of monsoon, the Bay of Bengal generated moisture enters this region and depletes the isotopic values. Additionally, the regional-scale convective activities produce periodic lows in the precipitation isotopes. Contrary to the general understanding, our study shows that the internal factors, such as the local land-atmosphere interactions, rather than the external influences, play a significant role in governing the precipitation isotopes in northeast India.11Ysciescopu