Temporal change in seismic wave attenuation using highly stable vibration sources

We developed a method to detect attenuation changes during seismic wave propagation excited by precisely controlled artificial seismic sources, namely Accurately Controlled Routinely Operated Signal System (ACROSS), and applied it to monitor the temporal changes for in situ data collected by previous studies. Our method, together with the use of the ACROSS sources, is less susceptible to noise level changes, from which conventional methods such as envelope calculation suffer. The method utilizes the noise level that is independently estimated in the frequency domain and eliminates the influence of the noise from the observed signal. For performance testing, we applied this method to a dataset that was obtained in an experiment at Awaji Island, Japan, from 2000 to 2001. We detected a change in amplitude caused by rainfall, variation in atmospheric temperature, and coseismic ground motions. Among them, coseismic changes are of particular interest because there are limited studies on coseismic attenuation change, in contrast to many studies on coseismic velocity decrease. At the 2000 Western Tottori earthquake (MW = 6.6, epicenter distance of 165 km), a sudden decrease in amplitude of up to 5% was observed. The coseismic amplitude reduction and its anisotropic characteristics, which showed a larger reduction in the direction of the major axis of velocity decrease, were consistent with the opening of fluid-filled cracks, as proposed by previous studies. The $$\Delta {Q}^{-1}$$ Δ Q - 1 corresponding to the amplitude change gives similar values to those reported in previous studies using natural earthquakes. Graphical Abstract

Biological aspects of Hypostomus affinis (Siluriformes: Loricariidae) in Brazilian coastal rivers

Aim Determine the length-weight relationship (LWR), the period of reproduction, and evaluate the variation of the condition factor (K) of Hypostomus affinis from two coastal drainages in southeastern Brazil, assessing the influence of the rainfall on these biological aspects. Methods fish were sampled quarterly between April 2008 and April 2010 in tributaries of the Doce River basin (DRB) and the Paraíba do Sul River basin (PSRB). Specimens were caught using gillnets. LWR parameters were assessed by location and sex through a t-test. We used the frequency of mature specimens (FM) to evaluate the breeding period. Both FM and K values were assessed by a sinusoidal equation. Results A total of 492 specimens was captured, of which 128 were from the Doce River basin (DRB) and 364 from the Paraíba do Sul River basin (PSRB). In both areas, specimens showed a negative allometric growth type. We collected mature specimens along the studied period in both drainages, with the highest frequency observed at the beginning of the rainy season. We found a positive correlation between the rate of matures and the local rainfall variation. The condition factor (K) was lower for specimens from DRB and did not show a cyclic trend. On the other hand, we observed a cyclic chance of the K values for the individual from the PSRB, peaking in the transitional dry-rainy period. However, it was not possible to correlate it to the rainfall variation. Conclusions LWR parameters of H. affinis were consistent with data already available in the literature. The rainfall may influence the FM but not the K values. In this case, biological characteristics such as reproduction and (or) feeding may be jointly driving a discrete variation of K values. The reduction in K values in the rainy periods suggests a remarkable energetic cost for the reproductive process. In short, our results help us to understand the life cycle of a fish species within a highly modified environment, especially by dams.

A Critical Analysis of Effect of Projected Temperature and Rainfall for Differential Sowing of Maize Cultivars Under RCP4.5 and RCP6.0 Scenarios for Punjab

A simulation study was conducted for two cultivars of maize (PMH1 and PMH2) in four agroclimatic zones of Punjab state of India where climate change depicts a consistent rise in temperature and increased variability in amount and distribution of rainfall. The yield assessment was performed for four agroclimatic zones of Punjab comprising of seven locations because variability in temperature rise and rainfall existed from location to location. Corrected ensemble model weather data (temperature and rainfall) for RCP4.5 and RCP6.0 was used as an input in the calibrated and validated CERES-Maize model and yield was simulated for a period of 70 years. The simulated yield for near as well as far-future was statistically assessed to understand the yield trend in Punjab under current dates of sowing and the results indicated a strong negative correlation between the yield and the weather parameters under the two scenarios at the considered four agroclimatic zones of Punjab. An increase in maximum and minimum temperature was observed ranging 0-4°C and 3-8°C, respectively at all the agroclimatic zones except Faridkot (zone V) where the increase in minimum temperature was observed by 0-3°C during the crop growth season while the rainfall variability ranged from 200-800mm under both the scenarios. At agroclimatic zone II and zone III similar results were obtained with higher yields at later dates of sowing and the rainfall at agroclimatic zone III was higher under RCP6.0 (300-600mm) while the yields for agroclimatic zone IV and V (Abohar) with rainfall variation of 270-450mm and 200-400mm, respectively showed no yield increment. Maize at Faridkot performed well with higher yields at early sowing dates. Among the two cultivars PMH1 showed more high yield years than PMH2 for most of the years. The yield under differential sowing dates showed the first fortnight of June and end June to be the best sowing dates for most of the locations as the yield for these dates were higher for most of the years. Thus, the study can be further applied to decide the future sowing window of maize for the agricultural state like Punjab.

A diagnostic study of contrasting rainfall epochs over Mumbai

An attempt has made to diagnose the synoptic features and some dynamic and thermodynamic parameters associated with contrasting rainfall situations (on consecutive days) during the monsoon season, over Mumbai. Study has been made for two contrasting monsoon years, viz. 1987 (Bad monsoon year) and 1988 (Good monsoon year). For this study RS data of Mumbai have been used. In many cases heavy rainfall on an isolated day over Mumbai is associated with the following synoptic systems (a) a trough on sea level chart running along west coast through Maharashtra Coast and (b) a cyclonic circulation (CYCIR) over Gujarat in the lower/middle tropospheric level. At least one of the above two systems ceased to exist on the days of light rainfall. Weighted average value of moist static energy is more on the day of heavy rainfall. In most of the cases convective available potential energy (CAPE) is also more on the day of heavy rainfall. LFC, on most of the cases, is seen to have lowered down on the days of heavy rainfall. Variation in upper air flow pattern and scorer parameter also gave very interesting clues to variation of rainfall on contrasting days.

EI-Nino southern oscillation and rainfall varIation over Bangladesh

In the present study, an attempt has been made to examine the variations of rainfall over Bangladesh and to find possible correlation with EI-Nino/Southern Oscillation (ENSO). Four stations have been chosen from four different climatic regions of Bangladesh for this purpose, namely Jessore, Dhaka. Barisal and Srimangal. The regions have been classified according to annual rainfall amounts. The rainfall data for forty three years, (1950-1992) have been analysed. The yearly mean rainfall shows a distinct negative decreasing tendency with the occurrence of ENSO.The seasonal rainfall analysis shows a somewhat better correlation.

Climate Change and Variability in the Northeastern Himalayan Region of India

Mountainous regions are considered highly vulnerable to the affects of climate change. The extent of change and variability of climatic parameters is still unexamined in many remote mountainous areas. This paper aims in understanding the change in pattern of rainfall and temperature for a period of 30 years in Mizoram. The analysis of time series changing trend in climatic variables is carried out by using Coefficient of Variation (CV), Mann-Kendall (M-K) and Sen’s Slope estimator. The analysis reveals that high variation is observed for both the variables in all the decadal, three decadal and seasonal change. The CV analysis shows that the highest seasonal rainfall variation occurs during winter and the highest seasonal temperature variation occurs during spring. Mann-Kendall test shows a significant change in rainfall with November showing the highest negative trend of rainfall. The temperature trend analysis in the study also reveals drastic change of temperature. An understanding of climatic change, trend and variability helps in predicting for better natural resources from the susceptibility of climate change.

Detection of Spatial Rainfall Variation over the Andean Region Demonstrated by Satellite-Based Observations

Topography has an important role in shaping regional and global climate systems, as it acts as a mechanical barrier to the low-level moisture flow. Thus, a complex spatial pattern of rainfall can exist over the mountainous region. Moreover, it is critical to advance our understanding of the relationship between rainfall and topography in terms of rainfall timing, frequency, and magnitude. In this study, characteristics of austral summer (December–February) precipitation are analyzed using 17-year (1998–2014) high-spatial-resolution (0.05° × 0.05°) data obtained from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) over the Andean region focusing on topographic impact. We observe an interaction between precipitation patterns and topography, with clear precipitation–elevation relationships in the Andes regions. The rainfall maxima zone was observed over the higher terrain of the central and southern Andes, and the zone is attributed to frequency and intensity of rainfall, respectively. In the foothills of the central Andes, we find there was a persistent rain system when a moist, low-level flow was lifted due to topography. In contrast, steep mountain slopes and a relatively dry atmosphere modulate deep convection in the foothills of southern Andes.