Quantitative Precipitation Forecast of Heavy Rainfall over Southern Vietnam

Thang Vu-Van, Thang Nguyen-Van, Huong Huynh-Thi-Lan, Nam Pham-Quang and Trung Nguyen-Quang

Page No. 1-20

The quality of quantitative precipitation forecast (QPF) in recent years has been improved by advances in numerical weather prediction, particularly by applying data assimilation. This study introduces an unprecedented QPF system designed for Southern Vietnam, implementing the Weather Research and Forecasting model and the Grid-point Statistical Interpolation analysis system. Two well-known assimilation techniques including three-dimensional variational (3D-Var) and hybrid 3D ensemble-variational (Hybrid 3D-EnVar) are examined. Conventional observation data and satellite-retrieved Atmospheric Motion Vectors are used in a series of experiments for eight extreme rainfall events during 2012–2016. Preliminary performance evaluation for daily accumulated precipitation showed that the overall accuracy was improved for rainfall thresholds from 20 to 60 mm by assimilating the conventional observations. Detailed assessments at an hourly timescale highlighted the promising performance of the current QPF system to replicating the timing of the rainfall peak.

Despite the marginal error reductions in fitting the background fields to observations, the flow-dependent background error covariances obtained from the ensemble remarkably modified analysis fields. Further analyses for the heavy rainfall event of 22 September 2016 elaborated that the increase of moisture transport and the modulation of atmospheric stability through the assimilation of observations enhanced the forecasted rainfall amount.

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Soil Slope Stability Assessment in part of Nilgiri Hill Ranges, Tamil Nadu, South India

Uvaraj S.

Page No. 21-29

To minimize the instability of soil slope, a critical evaluation of slope section is required. The stability of a slope is measured by its factor of safety using geometric and shear strength parameter based on infinite slopes. In this present study, soil slope stability conditions were assessed through determination of factor of safety of the soil slope estimated by the limit equilibrium method under different static conditions. The soil samples were collected for the direct shear test from the selected soil sections. The stability of slopes depends on the soil shear strength parameters such as Cohesion, Angle of internal friction, Unit weight of soil and Slope geometry. Based on the soil sample analysis, the area of factor of safety has been calculated. The exact latitude and longitude of the sampling locations along with respective soil properties and factor of safety are presented. If the value of the factor of safety is ≥ 1, it represents a stable condition of the slope and ≤1 denotes an unstable condition of soil slope. On the basis of hazard parameters, stability analyses and field observations, the remedial measures were suggested.

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Estimation of Sea Level Rise threat on the existence of the three northeastern and outermost small islands of Indonesia (i.e. Liki, Bepondi and Miossu Islands) using remote sensing method

Wirasatriya Anindya, Helmi Muhammad, Fauzi Rifqi Fajar, Harsono Gentio, Rahmadi Puji, Kusumastuti Wulan, Iryanthony Sigit Bhayu, Ramadhani Yoniar Hufan and Dharmawan I. Wayan Eka

Page No. 30-41

The outermost small islands determine the territorial boundary of Indonesia. Liki, Bepondi and Miossu Islands are the three northeastern and outermost small islands of Indonesia located in the northern part of Papua Island. On the other hand, sea level rise as an impact of global warming has threatened the existence of small islands around the world. In the present study, the threat of sea level rise (SLR) on the existence of those Islands is estimated from remote sensing method which is very useful for quick assessment. We use drone photography with photogrametry method to estimate the elevation of the three Islands. These elevations were corrected by tidal data to estimate the elevation above highest high water level.

The linear regression assumption of 25 years sea level anomaly data obtained from altimetry satellite from 1993-2017 was calculated to analyze the rate of SLR. The elevations above highest high water level for Liki, Bepondi and Miossu Islands are 265.84 m, 103.19 m, and 26.37 m respectively. With the rate of sea level rise of 4.4 mm/year, 4.4 mm/year, and 4.1 mm/year, the threat of SLR on the existence of the three northeastern and outer-most small islands of Indonesia is small.

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Supercycle of great Himalayan earthquake: Clues from observational seismicity

Sadique M.R., Ahad Alam A. and Masroor Alam M.

Page No. 42-49

Predictions of an upcoming earthquake is still a poorly established research area. Uncertainties regarding source initiation, rupture phenomena, occurrence timing, place and the magnitude of the earthquake occurrence often make prediction either very remote or of low confidence level. Despite all sophisticated geological and geophysical monitoring and satellite-based investigation, it is impossible to predict the earthquake until now accurately. Starting 1250 B.C till date, around 225 earthquakes (of magnitude six or higher) have occurred in the Indian subcontinent (mostly in the Himalayan region) according to the available data. Many researchers had warned of a “Great Earthquake” in the Himalayan region.

The present study tries to resolve the issue based on statistical observations and energy calculations due to seismic activities to forecast upcoming earthquakes. It has been found that due to consistent tectonic movements, the resulting earthquakes have a harmonic frequency of recurrence. A proper selection of time set and a careful parameterization of certain indicators may lead to significantly better results in terms of prediction accuracy.

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Development of a technique for delineation of water from optical images

Meti Chandrakanth Reddy and Panchagnula Manjusree

Page No. 50-57

Flood is a natural disaster; it causes loss of life and economic damage. The availability of high temporal and spatial resolution from optical satellites made it possible to get timely and reliable information on spatial extent of the flood which is necessary for monitoring, mapping and risk assessment. Developing an automated technique helps in delineating the flood in lesser time. Many spectral indices like Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Modified Difference Pond Index (MDPI), Modified Normalized Difference Water Index (MNDWI), Automatic Water Extraction Index (AWEI) and other combinations of normalized difference indices are used to detect surface water bodies and detection of flooded paddy fields. In this study, MODIS09A1 data covering floods in Assam was used to test these indices and the results showed that MNDWI has performed better.

A new technique was developed using the spectral combination of blue, green, infrared and short wave infrared bands to delineate water and tested on IRS Advanced Wide Field Sensor (AWiFS) data covering floods in Assam. The results were compared with the water layer derived from the RADARSAT microwave data acquired on the same day. The analysis revealed that both the algorithms have performed well and can be used for detection of water in real time mode. This would help the disaster managers to carry out relief measures quickly.

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A morphometric analysis of Silwani Watershed in Jharkhand, India using Geospatial technology

Mahato Lakhan Lal, Kumar Mukesh, Gourav Piyush, Singh Samuel David and Lal Deepak

Page No. 58-65

The quantitative analysis of morphometric parameters is found to be an important aspect of characterization of watersheds. In the present research work, Silwani Watershed, which is part of Hazaribagh plateau, a sub-division of the Chota Nagpur plateau has been selected for detail morphometric analysis. Satellite data (CARTOSAT- DEM, - 30m resolutions) was used in this study to understand the drainage characteristics. ArcGIS, Hydrotool has been used to find out different stream number, stream ordering, stream length which are useful for further calculation of other parameters. The stream order found in this watershed ranges from first to fifth order. The total area for the entire watershed has thus been found to be 979.30 sq km representing a sparse drainage network. The mean bifurcation ratio in this study is found to be 4.33 which concludes that the area comes under strong structural control on the drainage.

However, elongation ratio of the watershed showed less extended in shape more likely to flood and erosion. About 22 important parameters (Linear, Aerial and Relief aspects) have been calculated in this study to understand the characteristics of watershed. The result from this study can be used by watershed planner to work with this watershed.

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Sudden Commencements during Solar Cycles 11-24 and their Statistical trend

Dan Aparna and Nag Atanu

Page No. 66-74

A series (total 3721) of sudden commencements (SCs) was observed by rigorous magnetic analysis of 152 year records and the obtained results are re-investigated statistically. More than 50% of the cases (year of observation) register 10-19 SCs per year. Events with amplitude 15nT and 4 minute rise times are most probable. Most of the events occur in March-May (26.5%) and least during December (6.5%). Generally, the events are closely associated with each other and occur within one-two months of the previous event.

Related to the solar influence, the yearly numbers of SCs are very well correlated with the yearly values of SSNs (87.5%) than the monthly values of SSNs (55.4%). From the observation it is obvious that the yearly numbers of SCs are somehow correlated with the sunspot numbers.

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Understanding Precipitation Trends for Valsad District, Gujarat

Dave Meet A. and Mujmudar Sanskriti

Page No. 75-82

The precipitation studies are very useful for understanding distribution pattern and variation and also for understanding the characteristics of climate change. The study is principally focused on trend analysis of precipitation time series data of 30 years(1973-2002) using Mann-Kendall test at 85%, 90% and 95% significant level and Sen’s Slope Estimator Method at 95% of significance level for 17 Stations of Valsad district of Gujarat from June to October months .The results shows that total 9 stations among 17 show the presence of significance of monotonic trend of precipitation in which at all stations, rainfall is declining in each month(June to October) except Jhuj which shows rising of rainfall in June month over a study period(1973-2002).

For broad understanding of variability of precipitation at each station, the box plot of rainfall is plotted for each month (June to October).In June, Dugri and Valsad, in July, Mandva, in August, Mandva and Bopi, in September, Kalvada and in October, no stations are associated with large dispersion of rainfall. Also, Pindval shows higher outliers in June and October. Madhuban is associated with higher outlier in June, July, Septembers and October. Nanivahiyal and Varolitalat are havung greater outliers in Septembers.

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Mobile Telecom Networks in Disaster Communication Management: A survey on issues, challenges and solutions

Srinivasa Rao D. and Naidu G.B.S.R.

Page No. 83-91

Disaster is a natural phenomenon that occurs over various parts of the world at any time. In many cases, it may lead to huge economic and social losses. According to the international disaster database, India is one of the top disaster-prone regions in the world exposed to recurring devastations due to cyclones, floods and earthquakes. One of the first and immediate impact of any natural disaster is the collapse of the telecom infrastructure. Communication during this situation is highly required to save the lives of people in need of rescue.

The main reason for the failure of communication services is the lack of disaster preparedness for telecom operators, disaster management authorities and crisis communication plans. Well-equipped telecom infrastructure is always required to provide disaster resilience and establish communication between government, communities and organizations at risk. To understand the impact of natural calamities on communications, we reviewed some recent disasters focusing on cyclones. We then addressed the key issues and challenges faced by telecom network operators during various stages of a disaster. Further, we provided solutions to problems that enhance the resilience and efficiency of telecom networks.

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Probability assessment of seismicity in Kashmir valley based on Extreme Value Theory

Dar Ayaz Mohmood and Bukhari Kaiser

Page No. 92-97

The statistical analysis of 1668 earthquake events of M >3 from 1905–2019 was carried out using Extreme value theory (EVT). The spatial pattern and clustering of earthquakes was seen at the extensions of Kashmir basin whereas less frequent earthquakes have occurred inside the basin. The seismicity rate, recurrence and risk probability were calculated using Guttenberg- Richter18 relationship. The linear downslope trend was observed in seismicity via curve fitting method and implies decrease in earthquakes and increase in magnitudes.

The study shows that the probability of M 6.5 to occur in the region is 20 years whereas the earthquake M >7 is 100 years. The probability of earthquake M 6.5 to occur in 10 years is 40% and that of M 8 to occur in 200 years is 40%. Based on the data analysis, the region is prone to large scale earthquakes and therefore the seismic studies and relevant measures must not be ignored.

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