Spatio-temporal evaluation of event detection and measurement coherence among satellite rainfall products for ensembled dataset generation

Theoretical and Applied Climatology - Selection of a best suited satellite-based gridded rainfall product (SGRP) is challenging due to their significant variations at spatial and temporal scale....     

Comparison of TRMM and water district rain rates over New Mexico

This paper compares monthly and seasonal rain rates derived from the Version 5 (V5) and Version 6 (V6) TRMM Precipitation Radar (TPR, TSDIS reference 2A25), TRMM Microwave Imager (TMI, 2A12), TRMM Combined Instrument (TCI, 2B31), TRMM calibrated IR rain estimates (3B42) and TRMM merged gauge and satellite analysis (3B43) algorithms over New Mexico (NM) with rain gauge analyses provided by the New Mexico water districts (WD). The average rain rates over the NM region for 1998–2002 are 0.91mmd?1 for WD and 0.75, 1.38, 1.49, 1.27, and 1.07mmd?1 for V5 3B43, 3B42, TMI, PR and TCA; and 0.74, 1.38, 0.87 and 0.97 mm d?1 for V6 3B43, TMI, TPR and TCA, respectively. Comparison of V5 3B43 with WD rain rates and the daily TRMM mission index (TPR and TMI) suggests that the low bias of V5 3B43 for the wet months (summer to early fall) may be due to the non-inclusion of some rain events in the operational gauge analyses that are used in the production of V5 3B43. Correlation analyses show that the WD rain rates vary in phase, with higher correlation between neighboring WDs. High temporal correlations (>0.8) exist between WD and the combined algorithms (3B42, 3B43 and TCA for both V5 and V6) while satellite instrument algorithms (PR, TMI and TCI) are correlated best among themselves at the monthly scale. Paired t-tests of the monthly time series show that V5 3B42 and TMI are statistically different from the WD rain rates while no significant difference exists between WD and the other products. The agreements between the TRMM satellite and WD gauge estimates are best for the spring and fall and worst for winter and summer. The reduction in V6 TMI (?7.4%) and TPR (?31%) rain rates (compared to V5) results in better agreement between WD estimates and TMI in winter and TPR during summer.     

GPS-derived precipitable water vapour and its comparison with MODIS data for Almora, Central Himalaya, India

The present study is an attempt to analyse the precipitable water vapour (PWV) derived from Global Positioning System (GPS) and observed meteorological data over Almora, Central Himalayan Region. The PWV values derived using GPS study is compared with the corresponding moderate resolution imaging spectro-radiometer (MODIS) data. The statistical analysis reveals a positive correlation between both methods. Moderate resolution imaging spectroradiometer near-infrared (MODIS NIR) clear column water vapour product shows a higher correlation (R ² = 90–93 %) with GPS-derived precipitable water vapour on annual scale as compared to the seasonal scale (R ² = 62–87 %). MODIS is found to be overestimating in NIR clear column where the magnitude of bias and RMSE show systematic changes from season to season. Monsoon is an important phenomenon in the Indian weather context and holds significant importance in Central Himalayan ecosystem. The monthly and seasonal variation in precipitable water vapour is related with monsoon onset in the region. Diurnal variations in precipitable water vapour are studied with other meteorological data over Almora during dry and wet season. The precipitable water vapour had minimum value in the morning, increases in the afternoon to evening and again decreases to the midnight in both the dry and wet seasons. These results suggest that diurnal variation of water vapour is caused by the transport of water vapour by thermally induced local circulation.     

Long-term historic changes in climatic variables of Betwa Basin,India

In this study, trend analyses of historic past climatic variables were investigated for the Betwa basin located in Central India. In the serially independent climatic variables, Mann–Kendall test (MK test) was applied to the original sample data. However, in the serially correlated series, pre-whitening is used before employing the MK test. The long-term trend analysis showed several of the meteorological stations to exhibit a decreasing trend in annual and seasonal precipitation in the study area. Seasonal and yearly numbers of rainy days are decreased. However, onset of effective monsoon (except for Shivpuri and Tikamgarh stations) did not show any trend during the study period. For maximum temperature, five out of 12 stations showed a decreasing trend in monsoon season whereas almost all other stations showed an increasing trend in winter and no trend in summer season. For minimum temperature, only two stations of the basin showed a decreasing trend in monsoon and all other stations exhibited a significant increase in winter and summer season. The increase of winter temperature may adversely affect the growth of Rabi crop (wheat and mustard) in the study area. Potential evopotranspiration (PET) did not show any trend in monsoon, except for Jalaun and Jhansi stations, showing decreasing trends. Raisen and Vidisha stations showed an increasing trend in winter only, and the trend for other stations were random in nature. In summer, five out of 12 stations showed an increasing trend in PET. Results of this study can be employed in preparation of water resources development and management plan in the Betwa Basin.     

Mathematical analysis of a chaotic model in relevance to monsoon ISO

Mathematical analysis of a predominantly bimodal chaotic attractor, Lu system, was carried out to investigate a possible application of the model as a prototype of monsoon intra-seasonal oscillation (ISO). Bifurcation structures of the system are explored as the system parameter c and the forcing parameter F are varied. Stability criteria of equilibrium points of the forced Lu system are also explored in detail. A sensitivity study is carried out, by changing forcing parameter F, to explore relationships between some of the derived variables of the model and, based on such relationships, an empirical rule is used for extended range prediction. Analogous variables are also derived from the ISO data and prediction results are compared. Application of the prediction rule of regime transition to the observed ISO and chaotic model data is purely based on the bimodal characteristics of ISO and neglects some of the intricate mechanisms therein. We have found that a forced Lu system can be a good prototype in the prediction of peak anomaly of the monsoon ISO when growth rates around a threshold value are taken as predictors.     

Utilization of Basic Oxygen Furnace (BOF) slag in the production of a hydraulic cement binder

Basic Oxygen Furnace (BOF) slag is a major waste product generated during the steelmaking process. In India and in most industrial countries, the use of BOF slag as a road ballast and land filler has had a very long history. This being a low end use, a study was conducted to examine the possibility of converting the slag into a hydraulic binder. This paper describes the effect of cooling rate on mineralogy and cementing characteristics of normal BOF slag as well as iron oxide-devoid BOF slag. Specifically, the mineralogy and compressive strengths of heat-treated slags were compared with a conventional ordinary Portland cement. It was found that the slowly cooled slags did not show any cementing properties. The iron oxide-devoid slag, on slow cooling, disintegrated into fine powder. The water-cured cubic specimens of quenched slag products were tested for their compressive strengths. The cementing properties of the quenched slag products were improved by formation of hydraulic phases and showed considerable strength after 28 days of water curing.     

Performance evaluation of soil mixtures treated with graphite and used as barrier fill material for high-level radioactive waste repository

Buffer/backfill material is an important engineering barrier in a deep geological repository of high-level radioactive waste (HLW). Its thermo-hydro-mechanical (THM) performance is very important for the safe and stable operation of the HLW repository system. Natural graphite powder mixed with sodium bentonite forms a buffer/backfill material that can dissipate heat quickly and provide strong isolation. In this paper, the THM characteristics of bentonite–sand–graphite–polypropylene fiber (BSGF) mixtures, used as a buffer/backfill material, were studied through a series of laboratory tests. The influence of graphite and polypropylene fiber contents on thermal conductivity, swelling pressure, hydraulic conductivity, and strength properties of BSGF mixtures with different sand contents was analyzed. Experimental results indicated that the graphite content, the maximum graphite mesh number, and the initial dry density of bentonite–graphite mixtures influenced the thermal conductivity of bentonite–graphite mixtures. The addition of polypropylene fiber was found to enhance the shear strength and inhibit cracking without significantly affecting the expansivity, permeability, and thermal conductivity of the BSGF mixtures. This study provides a new buffer/backfill material that can improve the stability, functionality, and thermal efficiency of the HLW repository.

     

Hydro-chemical analysis and ionic flux of meltwater runoff from Khangri Glacier,West Kameng,Arunachal Himalaya,India

The detailed hydro-chemical study of meltwater draining from Khangri glacier Arunachal Pradesh has been carried out to evaluate the major ion chemistry and weathering processes in the drainage basin. The investigative results shows that the meltwater is almost neutral to slightly acidic in nature with Mg–HCO₃-dominated hydro-chemical facies. In glacial meltwater, Ca^+?2 is the most dominated cation followed by Mg⁺², Na⁺, and K⁺, while HCO₃^? is the most dominant anion followed by SO₄^2?, NO₃^?, and Cl^?. The dominant cations such as Ca⁺² and Mg⁺² show a good relation with the minerals abundance of the rocks. Calcite (CaCO₃) and biotite [K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂] are the most abundant minerals in the deformed carbonate-rich metasedimentary rocks near to the snout with some K feldspar (KAlSi₃O₈) and quartz (SiO₂). This suggests Ca⁺² have definitely entered into the water due to the dissolution of calcite and Ca feldspar (CaAl₂Si₂O₈), while one of the source of Mg⁺² is biotite. Na feldspar (NaAlSi₃O₈) has contributed towards the availability of sodium ion, while potassium ion is derived from the chemical weathering of K feldspar and biotite. The chemical weathering is the foremost mechanism controlling the hydro-chemistry of the Khangri glacier because of the least anthropogenic interferences. The mineralogy of surrounding rocks is studied to understand better, the rock–water interaction processes, and their contribution towards ionic concentration of meltwater. The meltwater discharge and individual ion flux of the catchment area have also been calculated, to determine the ionic denudation rate for the ablation season. The high elemental ratio of (Ca?+?Mg)/(Na?+?K) (7.91?±?0.39 mg/l) and low elemental ratio of (Na?+?K)/total cations (0.11?±?0.004) indicate that the chemical composition of meltwater is mainly controlled by carbonate weathering and moderately by silicate weathering. The scatter plot result between (Ca?+?Mg) and total cations confirms that carbonate weathering is a major source of dissolved ions in Khangri glacier meltwater. In addition, the statistical analysis was also used to determine the correlation between physical parameters of glacier meltwater which controlled the solute dynamics.     

Tectonic and magmatic evolution of the eastern Karakoram,India

Abstract

The Shyok suture zone separates the Ladakh terrane to the SW from the Karakoram terrane to the NE. Six tectonic units have been distinguished. From south to north these are; 1. Saltoro formation; 2. Shyok volcanites; 3. Saltoro molasse; 4. Ophiolitic melange; 5. Tirit granitoids; 6. Karakoram terrane including the Karakoram batholith. Albian—Aptian Orbitolina-bearing lime-stones and turbidites of the Saltoro formation tectonically overlie high-Mg-tholeiites similar to the tectonically overlying Shyok volcanites. The high-Mg tholeiitic basalts and calcalkaline andesites of the Shyok volcanites show an active margin signature. The Saltoro molasse is an apron-like, moderately folded association of redgreen shales and sandstones that are interbedded with ~ 50 m porphyritic andesite. Desiccation cracks and rain-drop imprints indicate deposition in a subaerial fluvial environment. Rudist fragments from a polygenic conglomerate of the Saltoro molasse document a post-Middle Cretaceous age. The calcalkaline andesites of the Shyok volcanites are intruded by the Tirit granitoids, which are located immediately south of the Ophiolitic melange and belong to a weakly deformed trondhjemite-tonalite-granodiorite-granite suite. These granitoids are subalkaline, I-type and were emplaced in a volcanic arc setting. The subalkaline to calcalkaline granitoids of the Karakoram batholith are I-and S-type granitoid. The I-type granitoids represent a typical calcalkaline magmatism of a subduction zone environment whereas the S-type granitoids are crustderived, anatectic peraluminous granites. New data suggest that the volcano-plutonic and sedimentary successions of the Shyok suture zone exposed in northern Ladakh are equivalent to the successions exposed along the Northern suture in Kohistan. It is likely that the o istan and Ladakh blocks evolved as one single tectonic domain uring the Cretaceous-Palaeogene. Subsequently, collision, suturing and accretion of the Indian plate along the Indus suture (50–60 Ma) together with tectonic activity along the Nanga Parbataramosh divided Kohistan and Ladakh into two arealy distinct magmatic arc terranes. The activity and a dextral offset along the Karakoram fault (Holocene-Recent) disrupted the original tectonic relationships. © 1999 Éditions scientifiques et médicales Elsevier SAS