ALBERT

Description: Discharge in mountain streams may be a mixture of snowmelt, water from surface runoff, and deep return flow through valley bottom alluvia. We used δ 18 O and δ 2 H, solute concentrations, and 222 Rn to determine water sources of a headwater stream located at the McDonald Creek watershed, Glacier National Park, USA during summer recession flow period. We analyzed minimal water isotope ranges of -17.6 to -16.5‰ and -133 to -121‰ for δ 18 O and δ 2 H, respectively, potentially due to dominance of snow-derived water in the stream. Likewise, solute concentrations measured in the stream through the watershed showed minimal variation with little indication of sub-surface water input into the stream. However, we observed 222 Rn activities in the stream that ranged from 39 to 2,646 Bq/m 3 with the highest value measured in middle of the watershed associated with channel constriction corresponding to changes in local orientation of underlying rocks. Downstream from this point, 222 Rn activity decreased from 581 to 117 Bq/m 3 in a series of punctuated steps associated with small rapids and waterfalls that we hypothesized to cause radon degassing with a maximum predicted loss of 427 Bq/m 3 along a 400 m distance. Based on mass balance calculations using 222 Rn activity values, streamflow, and channel characteristics, we estimated that groundwater contributed between 0.3 and 29% of total flow. Overall, we estimated a 5.9% of groundwater contribution integrated for stream reach measured at McDonald Creek during recession flow period. Finally, a lower mean hyporheic flux of 14 m 3 /day was estimated compared to the groundwater flux of 70,710 m 3 /day. These assessments highlight the potential for radon as a conservative tracer that can be used to estimate sub-surface water contribution in mountain streams within a complex geologic setting. This article is protected by copyright. All rights reserved.

Description: Thanks to the work of a number of scientists it is known that severe space weather can cause extensive social and economic disruptions in the modern high-tech society. It is therefore important to understand what determines the severity of space weather, and whether it can be predicted. We present results obtained from the analysis of coronal mass ejections (CME), solar energetic particle (SEP) events, interplanetary magnetic field (IMF), CME-magnetosphere coupling and geomagnetic storms associated with the major space weather events since 1998 by combining data from the ACE and GOES satellites with geomagnetic parameters, and the Carrington event of 1859, the Quebec event of 1989, and an event in 1958. The results seem to indicate that (1) it is the impulsive energy mainly due to the impulsive velocity and orientation of IMF Bz at the leading edge of the CMEs (or CME front) that determine the severity of space weather. (2) CMEs having high impulsive velocity (sudden non-fluctuating increase by over 275 km s −1 over the background) caused severe space weather (SvSW) in the heliosphere (failure of the SWI mode of SWEPAM in ACE) probably by suddenly accelerating the high energy particles in the SEPs ahead directly or through the shocks. (3) The impact of such CMEs which also show the IMF Bz southward from the leading edge caused SvSW at the Earth including extreme geomagnetic storms of mean Dst MP  〈 −250 nT during main phases; and the known electric power outages happened during some of these SvSW events. (4) The higher the impulsive velocity, the more severe the space weather, like faster weather fronts and tsunami fronts causing more severe damage through impulsive action. (5) The CMEs having IMF Bz northward at the leading edge do not seem to cause SvSW on Earth though, later when the IMF Bz turns southward, they can lead to super geomagnetic storms of intensity (DstMin) less than even −400 nT.

Description: Abstract Meteorological effects of wintertime air pollution in the Kathmandu valley were investigated using SOnic Detection and Ranging (SODAR) soundings, Automatic Weather Station (AWS) measurements, numerical simulation using Weather Research and Forecasting (WRF) data and Chemical Transport Modeling (CTM) during February, 2013. A surrogate for Black Carbon (BC) was used for transport simulation in order to better understand the effects of local meteorological factors on air pollution. In the simulation, the emission strength of the BC surrogate was assumed temporally‐constant and spatially‐uniform over the Kathmandu valley floor. The WRF simulation results were well correlated with observed meteorological measurements and demonstrated diurnal periodicity such as intrusion of westerly‐northwesterly wind into the Kathmandu valley and modification of the boundary layer activity due to afternoon wind. The transport simulation suggested long‐lasting weak wind, thermally‐stable stratification, and associated small turbulence during the night and morning caused potentially severe air pollution. We propose a method using wind velocity and Turbulent Kinetic Energy (TKE) in the surface layer to characterize pollution level in the Kathmandu valley.

Description: Coseismic travelling ionospheric disturbances (CTIDs) and their propagation characteristics during Mw 7.8 Gorkha earthquake in Nepal on 25 April 2015 have been investigated using a suite of ground based GPS receivers and broad band seismometers along with the space borne Radio Occultation observations over the Indian subcontinent region. Depletion in vertical total electron content (VTEC), a so called ionospheric hole, is observed near the epicenter ~9 – 11 minutes after the onset of earthquake. A positive pulse preceding the depletion, similar to N-shaped perturbation, propagating with an apparent velocity of ~2.4 km/s is observed on the South. Further, the CTIDs in the southward direction are found to split in to fast (~2.4 – 1.7 km/s) and slow (~680 – 520 m/s) propagating modes at epicentral distances greater than ~800 km. However, the velocities of fast mode CTIDs are significantly smaller than the surface Rayleigh wave velocity (~3.7 km/s), indicating that they are not the true imprint of Rayleigh wave, instead, can probably be attributed to the superimposed wave front formed by the mixture of acoustic waves excited by main shock and propagating Rayleigh wave. The southward CTIDs are found to propagate at F2-region altitudes of ~300 – 440 km captured by COSMIC Radio Occultation observations. The CTIDs with periods of ~4 – 6 minutes are observed in all directions with significantly larger amplitudes and faster propagation velocities in South and East directions. The observed azimuthal asymmetry in the amplitudes and velocities of CTIDs are discussed in terms of the alignment with geomagnetic field and nature of surface crustal deformation during the earthquake.

Description: The St. Patrick's Day storm of 17 th March, 2015 has a long lasting main phase with the Dst reaching a minimum of -223 nT. During the main phase, two strong prompt penetration electric field (PPEF) phases took place; first with the southward turning of IMF Bz around ~1200 UT and the second with the onset of a substorm around ~1725 UT leading to strong equatorial zonal electric field enhancements. The consequent spatio-temporal disturbances in the ionospheric Total Electron Content (TEC) and the resultant modifications in the Equatorial Ionization Anomaly (EIA) over the Brazilian longitudinal sector are investigated in detail. The simultaneous measurements from a large network of GPS receivers, Ionosonde and magnetometers over the Brazilian longitudinal sector are used for this study. In the presence of enhanced zonal electric field, the equatorial F2-layer peak (hmF2) experienced a rapid uplift without any significant change in the base height (h′F); while the F2 layer is redistributed into F2 and F3 layers. The enhanced zonal electric filed due to PPEF led to the strong super fountain effect under which, the anomaly crest departed poleward to ~40 o S latitude. In the presence of westward and equatorward wind surge over Brazil with the co-existing disturbance dynamo fields, strong hemispheric asymmetry is seen in the storm time response of EIA during both the PPEF phases.

Description: Understanding potential hydrologic influences to continued climate change in Himalayan watersheds is important for management of transnational water resources. This study estimates the climate change impacts on hydrologic processes of the Kali Gandaki watershed from central Himalayan region using the Soil and Water Assessment Tool. Daily predicted stream discharge of the basin for 1981-95 following calibration was accurate with Nash Sutcliffe Efficiency value〉0.75. Sensitivity analysis of the hydrologic parameters showed the precipitation and temperature lapse rates as the most sensitive parameters to the stream discharge. To assess the influence of continued climate change on hydrologic processes, we modified the weather inputs for the model using average, minimum and maximum temperature, and precipitation changes for the Special Report on Emission Scenarios B1, A1B and A2 derived from 16 General Circulation Models for 2080s. Mean annual stream discharge was approximately 39% higher than current values for the maximum temperature and precipitation changes of the A2 scenario and 22% less for minimum changes of the same scenario. Stream discharge was projected to be changed by +9% during monsoon season and by -6% during pre-monsoon season. Snowfall and snow melt were projected to be 30% and 29%, respectively, less than the current average for the maximum temperature and precipitation changes of the A2 scenario. Future simulations showed potential increase in monsoonal stream discharge associated with projected higher precipitation which when coupled with enhanced summer glacier melt might influence the downstream water availability of the basin. © 2013 John Wiley & Sons, Ltd.

Description: Discharge in mountain streams may be a mixture of snowmelt, water from surface runoff, and deep return flow through valley bottom alluvia. We used δ18O and δ2H, solute concentrations, and 222Rn to determine water sources of a headwater stream located at the McDonald Creek watershed, Glacier National Park, USA, during summer recession flow period. We analysed minimal water isotope ranges of -17.6‰ to -16.5‰ and -133‰ to -121‰ for δ18O and δ2H, respectively, potentially due to dominance of snow-derived water in the stream. Likewise, solute concentrations measured in the stream through the watershed showed minimal variation with little indication of subsurface water input into the stream. However, we observed 222Rn activities in the stream that ranged from 39 to 2646 Bq/m3 with the highest value measured in middle of the watershed associated with channel constriction corresponding to changes in local orientation of underlying rocks. Downstream from this point, 222Rn activity decreased from 581 to 117 Bq/m3 in a series of punctuated steps associated with small rapids and waterfalls that we hypothesized to cause radon degassing with a maximum predicted loss of 427 Bq/m3 along a 400m distance. Based on mass balance calculations using 222Rn activity values, streamflow, and channel characteristics, we estimated that groundwater contributed between 0.3% and 29% of total flow. Overall, we estimated a 5.9% of groundwater contribution integrated for stream reach measured at McDonald Creek during recession flow period. Finally, a lower mean hyporheic flux of 14m3/day was estimated compared to the groundwater flux of 70710 m3/day. These assessments highlight the potential for radon as a conservative tracer that can be used to estimate subsurface water contribution in mountain streams within a complex geologic setting. © 2016 John Wiley & Sons, Ltd.