Photosynthesis and Biomass Studies in \u3cem\u3eLasiurus sindicus\u3c/em\u3e of Chandan Grassland in Thar Desert

Grasslands comprise about one third of the world’s area of natural vegetation (Adams et al., 1990). Uncertainties prevail in the arid ecosystem with reference to carbon balance and fluxes which are primarily attributed to the sensitivity of grasslands to variation in annual precipitation, temperature and other regulating mechanisms of eco-physiological processes (Flanagan et al., 2002). It is therefore necessary to study radiation and water use efficiency of Lasiurus sindicus which is a predominant grass species in Chandan grassland of Thar desert to understand and evaluate its growth in relation to variation in climate. Also, it is pertinent to resolve whether grassland ecosystem function as a source or sink to atmospheric CO2. We therefore, measured diurnal variability of net photosynthesis, diurnal trend in light and water use efficiency and root and shoot biomass studies (10 days interval) of L. sindicus (Sewan) grass species in relation to ambient micrometeorological conditions during growth period along three points viz., initial, peak and declining phenophase to have basic understanding of eco-physiological responses to prevailing micrometeorology to evaluate its carbon use efficiency

Net Ecosystem Exchange of CO₂ in Deciduous Pine Forest of Lower Western Himalaya, India

Carbon cycle studies over the climate-sensitive Himalayan regions are relatively understudied and to address this gap, systematic measurements on carbon balance components were performed over a deciduous pine forest with an understory layer. We determined annual net carbon balance, seasonality in components of carbon balance, and their environmental controls. Results indicated a strong seasonality in the behavior of carbon exchange components. Net primary productivity (NPP) of pine forest exceeded soil respiration during the growing phase. Consequently, net ecosystem exchange exhibited a net carbon uptake. In the initial phase of the growing season, daily mean uptake was −3.93 (±0.50) g C m−2 day−1, which maximizes (−8.47 ± 2.3) later during post-monsoon. However, a brief phase of carbon release was observed during peak monsoon (August) owing to an overcast condition. Nevertheless, annually the forest remained as a carbon sink. The understory is extensively distributed and it turned out to be a key component of carbon balance because of sustained NPP during the pine leafless period. Temperature and evaporative fraction exhibited a prime control over the seasonal carbon dynamics. Our observations could lend certain useful insights into the application of coupled climate-carbon cycle models for the Himalaya and ecological functions in the region

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Not AvailableRegions of strong land–atmosphere coupling will be more susceptible to the hydrological impacts in the intensifying hydrological cycle. In this study, micrometeorological experiments were performed to examine the land–atmosphere coupling strength over a heat low region (Thar desert, NW India), known to influence the Indian summer monsoon (ISM). Within the vortex of Thar desert heat low, energy–water exchange and coupling behavior were studied for 4 consecutive years (2011–2014) based on sub-hourly measurements of radiative–convective flux, state parameters and sub-surface thermal profiles using lead-lag analysis between various E–W balance components. Results indicated a strong (0.11–0.35) but variable monsoon season (July–September) land–atmosphere coupling events. Coupling strength declined with time, becomes negative beyond 10-day lag. Evapotranspiration (LE) influences rainfall at the monthly time-scale (20–40 days). Highly correlated monthly rainfall and LE anomalies (r = 0.55, P < 0.001) suggested a large precipitation memory linked to the local land surface state. Sensible heating (SH) during March and April are more strongly (r = 0.6–0.7) correlated to ISM rainfall than heating during May or June (r = 0.16–0.36). Analyses show strong and weak couplings among net radiation (Rn)–vapour pressure deficit (VPD), LE–VPD and Rn–LE switching between energy-limited to water-limited conditions. Consistently, +ve and −ve residual energy [(dE) = (Rn − G) − (SH + LE)] were associated with regional wet and dry spells respectively with a lead of 10–40 days. Dew deposition (18.8–37.9 mm) was found an important component in the annual surface water balance. Strong association of variation of LE and rainfall was found during monsoon at local-scale and with regional-scale LE (MERRA 2D) but with a lag which was more prominent at local-scale than at regional-scale. Higher pre-monsoon LE at local-scale as compared to low and monotonous variation in regional-scale LE led to hypothesize that excess energy and water vapour brought through advection caused by pre-monsoon rainfall might have been recycled through rainfall to compensate for early part of monsoon rainfall at local-scale. However, long-term measurements and isotope analysis would be able to strengthen this hypothesis. This study would fill the key gaps in the global flux studies and improve understanding on local E–W exchange pathways, responses and feedbacks.Not Availabl

Evaluation of Satellite-Derived Rainfall Estimates for an Extreme Rainfall Event over Uttarakhand, Western Himalayas

The extreme rainfall event during June 2013 in the Western Himalayas caused widespread flash floods, which triggered landslides, a lake-outburst, and debris flow. For the hydrological study of such an unexpected extreme event, it is essential to have reliable and accurate rainfall predictions based on satellite observations. The mountainous state of Uttarakhand is covered by complex topography, and this state has few, unevenly distributed, rain gauge networks. This unique study was conducted to evaluate three satellite based rainfall products (i.e., TMPA-3B42, Global Satellite Mapping of Precipitation (GSMaP), and NOAA CPC Morphing Technique (CMORPH)) against the observed rain gauge-based India Meteorological Department (IMD) gridded dataset for this rainfall episode. The results from this comprehensive study confirmed that the magnitude of precipitation and peak rainfall intensity were underestimated in TMPA-3B42 and CMORPH against gauge-based IMD data, while GSMaP showed dual trends with under- and over-predictions. From the results of the statistical approach on the determination of error statistic metrics (MAE (mean absolute error), NRMSE (normalized root mean square error), PBIAS (percent bias), and NSE (Nash-Sutcliffe efficiency)) of respective satellite products, it was revealed that TMPA-3B42 predictions were more relevant and accurate compared to predictions from the other two satellite products for this major event. The TMPA-3B42-based rainfall was negatively biased by 18%. Despite these caveats, this study concludes that TMPA-3B42 rainfall was useful for monitoring extreme rainfall event in the region, where rain-gauges are sparse

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International Symposium on “New Dimensions in Agrometeorology for Sustainable Agriculture” held at G.B. Pant University of Agriculture & Technology, Pantnagar, INDIA from 16 to 18 October 2014, Abst.vol.pp.102-Best paper presentation award.Not AvailableNot Availabl

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Not AvailableRegions of strong land–atmosphere coupling will be more susceptible to the hydrological impacts in the intensifying hydrological cycle. In this study, micrometeorological experiments were performed to examine the land– atmosphere coupling strength over a heat low region (Thar desert, NW India), known to influence the Indian summer monsoon (ISM). Within the vortex of Thar desert heat low, energy–water exchange and coupling behaviour were studied for 4 consecutive years (2011–2014) based on sub-hourly measurements of radiative–convective flux, state parameters and sub-surface thermal profiles using lead-lag analysis between various E–W balance components. Results indicated a strong (0.11–0.35) but variable monsoon season (July–September) land–atmosphere coupling events. Coupling strength declined with time, becomes negative beyond 10-day lag. Evapotranspiration (LE) influences rainfall at the monthly time-scale (20–40 days). Highly correlated monthly rainfall and LE anomalies (r = 0.55, P< 0.001) suggested a large precipitation memory linked to the local land surface state. Sensible heating (SH) during March and April are more strongly (r = 0.6–0.7) correlated to ISM rainfall than heating during May or June (r = 0.16–0.36). Analyses show strong and weak coupling among net radiation (Rn)–vapour pressure deficit (VPD), LE–VPD and Rn–LE switching between energy-limited To water-limited conditions. Consistently,+ve and-ve residual energy [(dE) = (Rn - G) - (SH + LE)] were associated with regional wet and dry spells respectively with a lead of 10–40 days. Dew deposition (18.8–37.9 mm) was found an important component in the annual surface water balance. Strong association of variation of LE and rainfall was found during monsoon at local-scale and with regional-scale LE (MERRA 2D) but with a lag which was more prominent at local-scale than at regional-scale. Higher pre-monsoon LE at local-scale as compared to low and monotonous variation in regional-scale LE led to hypothesize that excess energy and water vapour brought through advection caused by pre-monsoon rainfall might have been recycled through rainfall to compensate for early part of monsoon rainfall at local-scale. However, long-term measurements and isotope analysis would be able to strengthen this hypothesis. This study would fill the Key gaps in the global flux studies and improve understanding on local E–W exchange pathways, responses and feedbacks.Not Availabl

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Not AvailableA complete annual cycle of micrometeorological measurements were carried out to characterize the dynamics of radiation and energy balance over a grassland ecosystem at Central Arid Zone Research Institute experimental area at Chandan, Jaisalmer, India from INSAT-linked ISRO-AMS (Agro-Met Station). The daytime average dekadal latent flux for actual evapotranspiration (AET) showed substantially lower magnitude (15-115 Wm-2) (AET: 0.3 mmd-1 to 2.5 mmd-1) with prominent peak coincident to south-west monsoon and peak growth stage. Sensible heat fluxes showed a large variation from 54 to 340 Wm-2 with peak during summer and minimum during winter and monsoon seasons. More than 70% energy balance closure (EBC) was observed. The non-closure of energy balance periods were characterized by strong local advections in summer. The daytime average net radiation showed bimodal behavior (195 to 420 Wm-2) with primary peak in spring-summer and secondary peak coincident to the start of the withdrawal of south-west monsoon. Significant complementary exponential relation (Y=0.045 e12.13X, R2 = 0.65) was found between dekadal albedo and Bowen ratio which was generally high (1.5 to 5.3) with intermittent dips (0.3 to 1.3) coincident to wet spells. Similarly, the dekadal albedo showed a higher magnitude (0.15 to 0.39), recording the highest (0.39) in the month of April and the lowest (0.15) in the month of September post-monsoon period when green grass growth was maximum.Not Availabl

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Not AvailableLand surface processes in data scarce arid northwestern India and their influence on the regional climate including monsoon are now gaining enhanced scientific attention. In this work the seasonal variation of land surface parameters and surface-energy flux components over Lasiurus sindicus grassland system in Thar Desert, western India were simulated using the mesoscale WRF model. The data on surface fluxes from a micrometeorological station, and basic surface level weather data from the Central Arid Zone Research Institute’s experimental field station (260 59’ 41”N;71o29’”10E), Jaisalmer, were used for comparison. Simulations were made for typical fair weather days in three seasons [12–14 January (peak winter); 29–31 May (peak summer), 19–21 August (monsoon)] during 2012. Sensitivity experiments conducted using a 5-layer soil thermal diffusion (5TD) scheme and a comprehensive land surface physics scheme (Noah) revealed the 5TD scheme gives large biases in surface fluxes and other land surface parameters. Simulations show large variations in surface fluxes and meteorological parameters in different seasons with high friction velocities, sensible heat fluxes, deep boundary layers in summer and monsoon season as compared to winter. The shortwave radiation is underestimated during the monsoon season, and is overestimated in winter and summer. In general, the model simulated a cold bias in soil temperature in summer and monsoon season and a warm bias in winter; the simulated surface fluxes and air temperature followed these trends. These biases could be due to a negative bias in net radiation resulting from a high bias in downward shortwave radiation in various seasons. The Noah LSM simulated various parameters more realistically in all seasons than the 5TD soil scheme due to inclusion of explicit vegetation processes in the former. The differences in the simulated fluxes with the two LSMs are small in winter and large in summer. The deep mixed layers are distributed in the northeastern parts in summer, northern areas in southwest monsoon and in southwestern parts during winter seasons and associated with the land-cover and vegetation dynamics. Our results present a baseline simulation study in this data scarce arid region.Not Availabl

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Not AvailableRegions of strong land–atmosphere coupling will be more susceptible to the hydrological impacts in the intensifying hydrological cycle. In this study, micrometeorological experiments were performed to examine the land– atmosphere coupling strength over a heat low region (Thar desert, NW India), known to influence the Indian summer monsoon (ISM). Within the vortex of Thar desert heat low, energy–water exchange and coupling behavior were studied for 4 consecutive years (2011–2014) based on sub-hourly measurements of radiative–convective flux, state parameters and sub-surface thermal profiles using lead-lag analysis between various E–W balance components. Results indicated a strong (0.11–0.35) but variable monsoon season (July–September) land–atmosphere coupling events. Coupling strength declined with time, becomes negativebeyond 10-day lag. Evapotranspiration (LE) influences rainfall at the monthly time-scale (20–40 days). Highly correlated monthly rainfall and LE anomalies (r = 0.55, P < 0.001) suggested a large precipitation memory linked to the local land surface state. Sensible heating (SH) during March and April are more strongly (r = 0.6–0.7) correlated to ISM rainfall than heating during May or June (r = 0.16–0.36). Analyses show strong and weak couplings among net radiation (Rn)–vapour pressure deficit (VPD), LE–VPD and Rn–LE switching between energy-limited to water-limited conditions. Consistently, +ve and −ve residual energy [(dE) = (Rn − G) − (SH + LE)] were associated with regional wet and dry spells respectively with a lead of 10–40 days. Dew deposition (18.8–37.9 mm) was found an important component in the annual surface water balance. Strong association of variation of LE and rainfall was found during monsoon at local-scale and with regional-scale LE (MERRA 2D) but with a lag which was more prominent at local-scale than at regional-scale. Higher pre-monsoon LE at local-scale as compared to low and monotonous variation in regional-scale LE led to hypothesize that excess energy and water vapour brought through advection caused by pre-monsoon rainfall might have been recycled through rainfall to compensate for early part of monsoon rainfall at local-scale. However, long-term measurements and isotope analysis would be able to strengthen this hypothesis. This study would fill the key gaps in the global flux studies and improve understanding on local E–W exchange pathways, responses and feedbacks.Not Availabl

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