ALBERT

Description: The Indo–Gangetic foreland basin has some of the highest rates of groundwater extraction in the world, focused in the states of Punjab and Haryana in northwest India. Any assessment of the effects of extraction on groundwater variation requires understanding of the geometry and sedimentary architecture of the alluvial aquifers, which in turn are set by their geomorphic and depositional setting. To assess the overall architecture of the aquifer system, we used satellite imagery and digital elevation models to map the geomorphology of the Sutlej and Yamuna fan systems, while aquifer geometry was assessed using 243 wells that extend to ∼200 m depth. Aquifers formed by sandy-channel bodies in the subsurface of the Sutlej and Yamuna fans have a median thickness of 7 and 6 m, respectively, and follow heavy-tailed thickness distributions. These distributions along with evidence of persistence in aquifer fractions as determined from compensation analysis, indicate persistent reoccupation of channel positions, and suggest that the major aquifers consist of stacked, multi-storied channel bodies. The percentage of aquifer material in individual boreholes decreases down-fan, although the exponent on the aquifer-body thickness distribution remains similar, indicating that the total number of aquifer bodies decrease down-fan but that individual bodies do not thin appreciably, particularly on the Yamuna fan. The interfan area and the fan-marginal zone have thinner aquifers and a lower proportion of aquifer material, even in proximal locations. We conclude that geomorphic setting provides a first-order control on the thickness, geometry, and stacking pattern of aquifer bodies across this critical region.

Description: Increased availability and quality of near real-time observations provide the opportunity to improve understanding of predictive skills of hydrologic models. Recent studies have shown the limited capability of river discharge data alone to adequately constrain different components of distributed model parameterizations. In this study, the GRACE satellite-based total water storage (TWS) anomaly is used to complement the discharge data with the aim to improve the fidelity of mesoscale hydrologic model (mHM) through multivariate parameter estimation. The study is conducted on 83 European basins covering a wide range of hydro-climatic regimes. The model parameterization complemented with the TWS anomalies leads to statistically significant improvements in (1) discharge simulations during low-flow period, and (2) evapotranspiration estimates which are evaluated against independent data (FLUXNET). Overall, there is no significant deterioration in model performance for the discharge simulations when complemented by information from the TWS anomalies. However, considerable changes in the partitioning of precipitation into runoff components are noticed by in-/exclusion of TWS during the parameter estimation. Introducing monthly averaged TWS data only improves the dynamics of streamflow on monthly or longer time scales, which mostly addresses the dynamical behavior of the baseflow reservoir. A cross-evaluation test carried out to assess the transferability of the calibrated parameters to other locations further confirms the benefit of complementary TWS data. In particular, the evapotranspiration estimates show more robust performance when TWS data are incorporated during the parameter estimation, in comparison with the benchmark model constrained against discharge only. This study highlights the value for incorporating multiple data sources during parameter estimation to improve the overall realism of hydrologic models and their applications over large domains. This article is protected by copyright. All rights reserved.

Description: The Indo-Gangetic Plain (IGP) region is one of the most densely populated regions in the World, but ground-based observations of air pollutants are highly limited in this region. Here, surface ozone observations made during March 2009–June 2011 at a semi-urban site (Pantnagar; 29.0°N, 79.5°E, 231 m amsl) in the IGP region are presented. Ozone mixing ratios show a daytime photochemical buildup with ozone levels sometimes as high as 100 ppbv. Seasonal variation in 24-h average ozone shows a distinct spring maximum (39.3 ± 18.9 ppbv in May) while daytime (1130–1630 h) average ozone shows an additional peak during autumn (48.7 ± 13.8 ppbv in November). The daytime, but not daily average, observed ozone seasonality is in agreement with the space-borne observations of OMI tropospheric column NO2, TES CO (681 hPa), surface ozone observations at a nearby high altitude site (Nainital) in the central Himalayas and to an extent with results from a global chemistry transport model (MATCH-MPIC). It is suggested that spring and autumn ozone maximum are mainly due to photochemistry, involving local pollutants and small-scale dynamical processes. Biomass burning activity over the northern Indian region could act as an additional source of ozone precursors during spring. The seasonal ozone photochemical buildup is estimated to be 32–41 ppbv during spring and autumn and 9–14 ppbv during August–September. A correlation analysis between ozone levels at Pantnagar and Nainital along with the mixing depth data suggests that emissions and photochemical processes in the IGP region influence the air quality of pristine Himalayan region, particularly during midday hours of spring. The evening rate of change (8.5 ppbv hr−1) is higher than the morning rate of change, which is dissimilar to those at other urban or rural sites. Ozone seasonality over the IGP region is different than that over southern India. Results from the MATCH-MPIC model capture observed ozone seasonality but overestimate ozone levels. Model simulated daytime ratios of H2O2/HNO3 are higher and suggesting that this region is in a NOx-limited regime. A chemical box model (NACR Master Mechanism) is used to further corroborate this using a set of sensitivity simulations, and to estimate the integrated net ozone production in a day (72.9 ppbv) at this site.

Description: Optically measured daylight mean mesopause temperatures over a dip equatorial station, Trivandrum (8.5°N; 77°E; dip lat. 0.5°N), have been analyzed in conjunction with simultaneously measured equatorial electrojet (EEJ)–produced magnetic field at the surface. The signature of planetary wave-tidal interactions in the mesosphere–lower thermosphere (MLT) region has been observed for the first time in the day-to-day variability in the EEJ, i.e., the time of its peaking and the duration, as inferred from the EEJ-produced magnetic field on the ground. The present study shows that the planetary wave of quasi 16 day periodicity plays an important role in causing these variabilities, especially during the winter months. The quasi 16 day wave is found to be modulating the mesopause temperature (MT), duration, and time of the maximum EEJ intensity (DEEJ and TEEJ). During positive excursions of the planetary wave, TEEJ showed a shift toward evening, while the MT showed an increase and DEEJ showed a broadening. Similarly, all these parameters exhibited an opposite trend during negative excursions. The planetary wave-tidal interactions and subsequent modification of the tidal components have been shown to be responsible for the observed variations. This study presents a new perspective addressing the day-to-day variability of the EEJ.

Description: [1]  Simultaneous in-situ measurements of ozone, CO, and NO y have been made for the first time at an high altitude site Nainital (29.37 o N, 79.45 o E, 1958 m amsl) in the central Himalayas during 2009-2011. CO and NO y levels discern slight enhancements during the daytime, unlike in ozone. The diurnal patterns are attributed mainly to the dynamical processes including vertical winds and the boundary layer evolution. Springtime higher levels of ozone (57.5 ± 12.6 ppbv), CO (215.2 ± 147 ppbv), and NO y (1918 ± 1769.3 pptv) have been attributed mainly to the regional pollution supplemented with northern Indian biomass burning. However, lower levels of ozone (34.4 ± 18.9 ppbv), CO (146.6 ± 71 ppbv), and NO y (1128.6 ± 1035 pptv) during summer-monsoon are shown to be associated with the arrival of air-mass originated from marine regions. Downward transport from higher altitudes is estimated to enhance surface ozone levels over Nainital by 6.1 - 18.8 ppbv. The classification based on air-mass residence time, the altitude variations along trajectory and the boundary layer shows higher levels of ozone (57 ± 14 ppbv), CO (206 ± 125 ppbv), and NO y (1856 ± 1596 pptv), in the continental air-masses when compared with their respective values (28 ± 13 ppbv, 142 ± 47 ppbv, and 226 ± 165 pptv) in the regional background air-masses. In general, positive inter-species correlations are observed which suggest the transport of air-mass from common source regions (except during winter). Ozone–CO and ozone-NO y slope values are found to be lower in comparison to those at other global sites, which clearly indicates the incomplete in-situ photochemistry and greater role of transport processes in this region. The higher CO/NO y value also confirms minimal influence of the fresh emissions at the site. Enhancements in ozone, CO, and NO y during high fire activity period are estimated to be 4-18%, 15-76%, and 35-51% respectively. Despite higher CO and NO y concentrations at Nainital, ozone levels are nearly similar to those at other global high altitude sites.

Description: Studies on the solar eclipse–induced changes in near-surface ozone and its precursors NOx and CO were carried out at two nearby tropical coastal locations, Thumba (very close to the sea) and the Centre for Earth Science Studies (CESS), which is 4.5 km off the Thumba coast and with varying topography, during the annular eclipse of 15 January 2010. The surface ozone decreased by 12 and 13 ppb (35% and 52%) over Thumba and CESS, with the time lag of 40 min and 25 min from the maximum phase of eclipse, respectively, and at CESS, post-eclipse recovery was faster compared to Thumba. No pronounced change was observed in NOx, but CO showed an enhancement toward the ending phase of the eclipse. The diurnal patterns of ozone and their differences at the two sites were strongly dependent on local meteorology, in particular, the mesoscale dynamics and topography. While the temperature decreased by 1.2°C at Thumba, the decrease was almost double (∼2.1°C) at CESS. The early fall in temperature caused the early setting in of land-breeze (post-eclipse effect), which in turn triggered an early evening decrease in near-surface ozone compared to the control conditions. The present study points to the role of mesoscale meteorology/dynamics in controlling the evolution of solar eclipse–induced changes in ozone in a relatively clean environment. The chemical box model simulations reproduced these broad features: a percentage decrease and the time lag in surface ozone. The observation of total column ozone showed a decrease and fluctuations, after the eclipse maximum.

Description: Estuaries are known to be strong source for atmospheric CO2, however, little information is available from Indian estuaries. In order to quantify CO2 emissions from the Indian estuaries, samples were collected at 27 estuaries all along the Indian coast during discharge (wet) period. The emissions of CO2 to the atmosphere from Indian estuaries were 4–5 times higher during wet than dry period. The pCO2 ranged between ∼300 and 18492 μatm which are within the range of world estuaries. The mean pCO2 and particulate organic carbon (POC) showed positive relation with rate of discharge suggesting availability of high quantities of organic matter that led to enhanced microbial decomposition. The annual CO2 fluxes from the Indian estuaries, together with dry period data available in the literature, amounts to 1.92 TgC which is 〉10 times less than that from the European estuaries. The low CO2 fluxes from the Indian estuaries are attributed to low flushing rates and less human settlements along the banks of the Indian estuaries.