Accuracy analysis of the 2014–2015 Global Shuttle Radar Topography Mission (SRTM) 1 arc-sec C-Band height model using International Global Navigation Satellite System Service (IGS) Network

Global Shuttle Radar Topography Mission (SRTM) data products have been widely used in Earth Sciences without an estimation of their accuracy and reliability even though large outliers exist in them. The global 1 arc-sec, 30 m resolution, SRTM C-Band (C-30) data collected in February 2000 has been recently released (2014–2015) outside North America. We present the first global assessment of the vertical accuracy of C-30 data using Ground Control Points (GCPs) from the International GNSS Service (IGS) Network of high-precision static fiducial stations that define the International Terrestrial Reference Frame (ITRF). Large outliers (height error ranging from –1285 to 2306 m) were present in the C-30 dataset and 14% of the data were removed to reduce the root mean square error (RMSE) of the dataset from ～187 to 10.3 m which is close to the SRTM goal of an absolute vertical accuracy of RMSE ～10 m. Globally, for outlier-filtered data from 287 GCPs, the error or difference between IGS and SRTM heights exhibited a non-normal distribution with a mean and standard error of 6.5 ± 0.5 m. Continent-wise, only Australia, North and South America complied with the SRTM goal. At stations where all the X- and C-Band SRTM data were present, the RMSE of the outlier-filtered C-30 data was 11.7 m. However, the RMSE of outlier-included dataset where C- and X-Band data were present was ～233 m. The results suggest that the SRTM data must only be used after regional accuracy analysis and removal of outliers. If used raw, they may produce results that are statistically insignificant with RMSE in 100s of meters.     

Evaluating Lost Person Behavior Models

US wilderness search and rescue consumes thousands of person‐hours and millions of dollars annually. Timeliness is critical: the probability of success decreases substantially after 24 hours. Although over 90% of searches are quickly resolved by standard “reflex” tasks, the remainder require and reward intensive planning. Planning begins with a probability map showing where the lost person is likely to be found. The MapScore project described here provides a way to evaluate probability maps using actual historical searches. In this work we generated probability maps the Euclidean distance tables in (Koester 2008 ), and using Doke's ( 2012 ) watershed model. Watershed boundaries follow high terrain and may better reflect actual barriers to travel. We also created a third model using the joint distribution using Euclidean and watershed features. On a metric where random maps score 0 and perfect maps score 1, the Euclidean distance model scored 0.78 (95%CI: 0.74–0.82, on 376 cases). The simple watershed model by itself was clearly inferior at 0.61, but the Combined model was slightly better at 0.81 (95%CI: 0.77–0.84).     

The behavior of natural and anthropogenic osmium in the Hudson River-Long Island Sound estuarine system

The extent to which riverine Os is trapped in a temperate estuary was the aim of this study. The behavior of Os through the Hudson River, East River and the Long Island Sound (LIS) system is addressed using both natural Os and anthropogenically mobilized Os. The Os concentration ([Os]) and isotopic composition (¹⁸⁷Os/¹⁸⁸Os) of the Mid-Atlantic Bight as inferred from the analysis of a water sample of 31‰ salinity (S) at Vineyard Sound, MA are 46 fM and 1.070, respectively. In comparison, the Hudson River at Newburgh, NY has [Os] = 68 fM and ¹⁸⁷Os/¹⁸⁸Os = 1.265. The Os concentration of the East River at the Whitestone Bridge is 51 fM and remains essentially constant proceeding eastward in the LIS despite the increase of salinity from 20‰ towards the higher value of the Mid-Atlantic Bight. The ¹⁸⁷Os/¹⁸⁸Os ratio of water at Whitestone Bridge is 0.945 and increases eastward through the Sound to 0.979 at 7 km and then to 1.019 at 39.6 km. The behavior of Os through LIS appears to be conservative at S > 20‰. On the basis of Os concentration and isotopic composition we infer that anthropogenic Os is being added to the East River through sewers with the likely isotopic ratio of ∼0.13 and that about 24% of riverine Os must be removed at S ? 20‰. There is a net transport of about 0.4-1 mole of anthropogenic Os per year from the East River into the LIS. The residence time of Os in the ocean at present must be about 39,000 years, unless an independent source of supply of Os can be identified.     

The lesser Himalayan Duplex in Sikkim: Implications for variations in Himalayan shortening

Thrust duplexes account for large fractions of the total shortening in most fold-thrust belts (FTBs). They also provide an efficient mechanism for transferring slip upward from the basal decollement and for transporting roof thrust sheets over long distances. The Lesser Himalayan duplex (LHD) plays a prominent role in the overall evolution of the Himalayan FTB and has been described from Garhwal-Kumaon to Bhutan. In Sikkim the LHD shows unique structural geometry and has been responsible for transporting crystalline thrust sheets (MCT 1 and MCT 2) farther southward than other parts of the Himalaya. Such lateral variations in LHD geometry imply variations in the kinematic history of the Lesser Himalaya and variations in shortening and shortening history along the length of the Himalayan arc, and these are reflected in observable large scale structural patterns.     

Contemporary deformation in the Kashmir–Himachal,Garhwal and Kumaon Himalaya: significant insights from 1995–2008 GPS time series

We present new insights on the time-averaged surface velocities, convergence and extension rates along arc-normal transects in Kumaon, Garhwal and Kashmir–Himachal regions in the Indian Himalaya from 13 years of high-precision Global Positioning System (GPS) time series (1995–2008) derived from GPS data at 14 GPS permanent and 42 campaign stations between $29.5{-}35^{\circ }\hbox {N}$ and $76{-}81^{\circ }\hbox {E}$ . The GPS surface horizontal velocities vary significantly from the Higher to Lesser Himalaya and are of the order of 30 to 48 mm/year NE in ITRF 2005 reference frame, and 17 to 2 mm/year SW in an India fixed reference frame indicating that this region is accommodating less than 2 cm/year of the India–Eurasia plate motion ( ${\sim }4~\hbox {cm/year}$ ). The total arc-normal shortening varies between ${\sim }10{-}14~\hbox {mm/year}$ along the different transects of the northwest Himalayan wedge, between the Indo-Tsangpo suture to the north and the Indo-Gangetic foreland to the south indicating high strain accumulation in the Himalayan wedge. This convergence is being accommodated differentially along the arc-normal transects; ${\sim } 5{-}10~\hbox {mm/year}$ in Lesser Himalaya and 3–4 mm/year in Higher Himalaya south of South Tibetan Detachment. Most of the convergence in the Lesser Himalaya of Garhwal and Kumaon is being accommodated just south of the Main Central Thrust fault trace, indicating high strain accumulation in this region which is also consistent with the high seismic activity in this region. In addition, for the first time an arc-normal extension of ${\sim }6~\hbox {mm/year}$ has also been observed in the Tethyan Himalaya of Kumaon. Inverse modeling of GPS-derived surface deformation rates in Garhwal and Kumaon Himalaya using a single dislocation indicate that the Main Himalayan Thrust is locked from the surface to a depth of ${\sim }15{-}20~\hbox {km}$ over a width of 110 km with associated slip rate of ${\sim }16{-}18~\hbox {mm/year}$ . These results indicate that the arc-normal rates in the Northwest Himalaya have a complex deformation pattern involving both convergence and extension, and rigorous seismo-tectonic models in the Himalaya are necessary to account for this pattern. In addition, the results also gave an estimate of co-seismic and post-seismic motion associated with the 1999 Chamoli earthquake, which is modeled to derive the slip and geometry of the rupture plane.     

Imaging observations of radio bursts at meter-decameter wavelengths

Solar Physics - In this article, we review some of the recent results obtained with imaging observations of the Sun at meter-decameter wavelengths, using the Clark Lake multifrequency...     

Higher order corrections to dust-acoustic ZK-solitons in a magnetized quantum dusty plasma

Nonlinear propagation of two dimensional dust-acoustic solitary waves in a magnetized quantum dusty plasma whose constituents are electrons, ions, and negatively charged heavy dust particles are investigated using quantum hydrodynamic model. The Zakharov-Kuznetsov (ZK) equation is derived by using reductive perturbation technique (RPT). The higher order inhomogeneous ZK-type differential equation is obtained for the correction to ZK- soliton. The dynamical equation for dressed soliton is solved by using renormalization method. The effects of obliqueness (l _x ) of the wave vector, magnetic field strength (B ₀), quantum parameter for ions (H _i ), soliton velocity (θ) and Fermi temperature ratio (σ) on amplitudes and widths of the ZK-soliton and as well as of the dressed soliton are investigated. The conditions for the validity of the higher order correction are described. Suitable parameter ranges for the existence of compressive and rarefactive dressed solitons are also discussed.