scholarly journals Volatility in Rainfall and Predictability of Droughts in Northwest Bangladesh

2020 ◽  
Vol 12 (23) ◽  
pp. 9810
Author(s):  
Mohammad Ahsan Uddin ◽  
ASM Maksud Kamal ◽  
Shamsuddin Shahid ◽  
Eun-Sung Chung
Keyword(s):  
Drought Index ◽  
Monsoon Rainfall ◽  
Daily Rainfall ◽  
Rainfall Anomaly ◽  
Trend Test ◽  
Time Varying ◽  
Jump Model ◽  
Rapid Changes ◽  
Anomaly Analysis ◽  
Autoregressive Conditional Heteroscedasticity

This study was conducted to evaluate the variability, trends, volatility, and transition patterns of rainfall in drought-prone northwest Bangladesh. Daily rainfall recorded at five stations for the period 1959–2018 were used for this purpose. Non-parametric tests of variability changes, a modified Mann–Kendall trend test, innovative trend analysis (ITA), a generalized autoregressive conditional heteroscedasticity (GARCH)–jump model, and a Markov chain (MC) were used to assess the variability changes, trends, volatility, and transitions in rainfall to understand the possibility of the persistence of droughts and their predictability. The results showed an overall decrease of variability in annual and seasonal rainfall, but an increase in mean pre-monsoon rainfall and a decrease in mean monsoon rainfall. This caused a decrease in pre-monsoon droughts, but few changes in monsoon droughts. The ITA and rainfall anomaly analysis revealed high temporal variability and, thus, rapid shifts in rainfall regimes, which were also supported by the volatility dynamics and time-varying jumps from the GARCH–jump model and the rapid changes in drought index from the MC analysis. Therefore, the lack of drought in recent years cannot be considered as an indicator of declining droughts in the region.

scholarly journals Dynamical delimitation of the Central American Dry Corridor (CADC) using drought indices and aridity values

2019 ◽  
Vol 43 (5) ◽  
pp. 627-642 ◽  
Author(s):  
Luis Eduardo Quesada-Hernández ◽  
Oscar David Calvo-Solano ◽  
Hugo G Hidalgo ◽  
Paula M Pérez-Briceño ◽  
Eric J Alfaro
Keyword(s):  
Drought Index ◽  
Pacific Coast ◽  
Potential Evapotranspiration ◽  
Standardized Precipitation Index ◽  
Severity Index ◽  
Rainfall Anomaly ◽  
Central American ◽  
Drought Indices ◽  
Drought Severity ◽  
Southern Mexico

The Central American Dry Corridor (CADC) is a sub-region in the isthmus that is relatively drier than the rest of the territory. Traditional delineations of the CADC’s boundaries start at the Pacific coast of southern Mexico, stretching south through Central America’s Pacific coast down to northwestern Costa Rica (Guanacaste province). Using drought indices (Standardized Precipitation Index, Modified Rainfall Anomaly Index, Palmer Drought Severity Index, Palmer Hydrological Drought Index, Palmer Drought Z-Index and the Reconnaissance Drought Index) along with a definition of aridity as the ratio of potential evapotranspiration (representing demand of water from the atmosphere) over precipitation (representing the supply of water), we proposed a CADC delineation that changes for normal, dry and wet years. The identification of areas that change their classification during extremely dry conditions is important because these areas may indicate the location of future expansion of aridity associated with climate change. In the same way, the delineation of the CADC during wet extremes allows the identification of locations that remain part of the CADC even during the wettest years and that may require special attention from the authorities.

scholarly journals Using integrated meteorological and hydrological indices to assess drought characteristics in southern Taiwan

2019 ◽  
Vol 50 (3) ◽  
pp. 901-914 ◽  
Author(s):  
Hsin-Fu Yeh
Keyword(s):  
River Basin ◽  
Drought Index ◽  
Standardized Precipitation Index ◽  
Assessment Method ◽  
Drought Indices ◽  
Trend Test ◽  
Integrated Analysis ◽  
Drought Assessment ◽  
Southern Taiwan ◽  
The Standardized Precipitation Index

Abstract Numerous drought index assessment methods have been developed to investigate droughts. This study proposes a more comprehensive assessment method integrating two drought indices. The Standardized Precipitation Index (SPI) and the Streamflow Drought Index (SDI) are employed to establish an integrated drought assessment method to study the trends and characteristics of droughts in southern Taiwan. The overall SPI and SDI values and the spatial and temporal distributions of droughts within a given year (November to October) revealed consistent general trends. Major droughts occurred in the periods of 1979–1980, 1992–1993, 1994–1995, and 2001–2003. According to the results of the Mann–Kendall trend test and the Theil–Sen estimator analysis, the streamflow data from the Sandimen gauging station in the Ailiao River Basin showed a 30% decrease, suggesting increasing aridity between 1964 and 2003. Hence, in terms of water resources management, special attention should be given to the Ailiao River Basin. The integrated analysis showed different types of droughts occurring in different seasons, and the results are in good agreement with the climatic characteristics of southern Taiwan. This study suggests that droughts cannot be explained fully by the application of a single drought index. Integrated analysis using multiple indices is required.

scholarly journals Exploring the Evolution of Drought Characteristics in Balochistan, Pakistan

2020 ◽  
Vol 10 (3) ◽  
pp. 913 ◽  
Author(s):  
Shoaib Jamro ◽  
Falak Naz Channa ◽  
Ghulam Hussain Dars ◽  
Kamran Ansari ◽  
Nir Y. Krakauer
Keyword(s):  
Climate Change ◽  
Drought Index ◽  
Risk Index ◽  
Trend Test ◽  
Standardized Precipitation Evapotranspiration Index ◽  
Long Duration ◽  
Tree Edge ◽  
Edge Removal ◽  
The 1960S

In the wake of a rapidly changing climate, droughts have intensified, in both duration and severity, across the globe. The Germanwatch long-term Climate Risk Index ranks Pakistan among the top 10 countries most affected by the adverse effects of climate change. Within Pakistan, the province of Balochistan is among the most vulnerable regions due to recurring prolonged droughts, erratic precipitation patterns, and dependence on agriculture and livestock for survival. This study aims to explore how the characteristics of droughts have evolved in the region from 1902–2015 using 3-month and 12-month timescales of a popular drought index, the Standardized Precipitation Evapotranspiration Index (SPEI). The region was divided into six zones using Spatial “K”luster Analysis using Tree Edge Removal (SKATER) method, and run theory was applied to characterize droughts in terms of duration, severity, intensity, and peak. The results of the non-parametric Mann–Kendall trend test applied to SPEI indicate prevailing significant negative trends (dryer conditions) in all the zones. Balochistan experienced its most severe droughts in the 1960s and around 2000. The effects of climate change are also evident in the fact that all the long duration droughts occurred after 1960. Moreover, the number of droughts identified by 3-month SPEI showed a significant increase after 1960 for all six zones. The same trend was found in the 12-month SPEI but for only three zones.

scholarly journals Analysis of Length of Growing Season in Some Agro-ecological Zones Using Non-parametric Trend Test

2019 ◽  
Vol 11 (2) ◽  
pp. 241-248
Author(s):  
Olumuyiwa Idowu OJO ◽  
Charity C. TEMENU ◽  
Masengo Francois ILUNGA
Keyword(s):  
Rainy Season ◽  
Daily Rainfall ◽  
Growing Season ◽  
Trend Test ◽  
Rainfall Characteristics ◽  
Land Preparation ◽  
Ecological Zones ◽  
Agricultural Enterprise ◽  
Savannah Zone ◽  
Agro Ecological Zones

The ever increasing population and consequently increase in demand for food and the increasing exploitation of the land justifies the need for adequate studies on rainfall as an important factor affecting agricultural production. The date of the onset of rains is an important factor in planning agricultural operations such as land preparation and sowing. The study conducted agro-statistical analysis of rainfall characteristics over three different zones of Nigeria. Daily rainfall data were collected for the period between 1971 and 2005 for 6 stations and were subjected to standard analysis to determine trends and variations in the onset dates, cessation dates, length of rainy season, number of wet days, drought episodes. The results showed that the inter-annual variability of the onset dates is higher than that of cessation dates with a progressive shift in both onset and cessation dates. The length of rainy season varied from 77-291 days in Guinea zone, 77-243 days for Savannah and 73-155 days for the Sahel. Changes in the length of growing season ranged between -9 and -10 for Guinea zone, -21 and 11 days for Savannah zone and -28 and 20 days for the Sahel. Similarly, the numbers of wet days have declined over Nigeria. The information presented in this study are to serve as input for proper land and water resources management for productive agricultural enterprise across the three major agro-ecological zones of Nigeria.

scholarly journals Improved Seasonal Precipitation Forecasts for the Asian Monsoon Using 16 Atmosphere–Ocean Coupled Models. Part II: Anomaly

2012 ◽  
Vol 25 (1) ◽  
pp. 65-88 ◽  
Author(s):  
T. N. Krishnamurti ◽  
Vinay Kumar
Keyword(s):  
Asian Monsoon ◽  
Monsoon Rainfall ◽  
Systematic Errors ◽  
Rainfall Anomaly ◽  
Seasonal Rainfall ◽  
Seasonal Precipitation ◽  
Training Phase ◽  
Post Processing ◽  
Coupled Models ◽  
Rms Errors

Abstract This is the second part of a paper on the improved seasonal precipitation forecasts for the Asian monsoon using 16 atmosphere–ocean coupled models. This study utilizes a large suite of coupled atmosphere–ocean models; this second part largely addresses the skill of rainfall anomaly forecasts. These include both deterministic and probabilistic skill measures such as the RMS errors, anomaly correlations, equitable threat scores, and the Brier skill score. It was possible to improve the skills of rainfall climatology from the use of a downscaled multimodel superensemble to very high levels, and it is of interest to ask how far this methodology would go toward improving the skills of seasonal rainfall anomaly forecasts. It is possible to go through a sequence of multimodel post processing to improve upon these skills by using a dense rain gauge network over Asia, downscaling forecasts for each member model, and constructing a multimodel superensemble that benefits from the persistence of errors of the member models. This paper addresses the spinup issues of the downscaling and the superensemble results where the number of years of model data needed for training phase, for the downscaling, and for the construction of the superensemble, is addressed. In the context of cross validation, the training phase includes 14 seasons of monsoon data. The forecast phase is only one season; it is this season that was not included in the training phase each time. The relationship between data length and the number of models needed for enhanced skills is another issue that is addressed. Seasonal climate forecasts over the larger monsoon Asia domain and over the regional belts are evaluated. The superensemble forecasts invariably have the highest skill compared to the member models globally and regionally. This is largely due to the presence of large systematic errors in models that carry low seasonal prediction skills. Such models carry persistent signatures of systematic errors, and their errors are recognized by the multimodel superensemble. The probabilistic skills show that the superensemble-based forecasts carry a much higher reliability score compared to the member models. This implies that the superensemble-based forecasts are the most reliable among all the member models. It is possible to examine the performance of models and of the superensemble during periods of heavy monsoon rainfall versus those for deficient monsoon rainfall seasons. One of the conclusions of this study is that given the uncertainties in current modeling for seasonal rainfall forecasts, post processing of multimodel forecasts, using the superensemble methodology, seems to provide the most promising results for the rainfall anomaly forecasts. These results are confirmed by an additional skill metric where the RMS errors and the correlations of forecast skills are evaluated using a normalized precipitation anomaly for the forecasts and the observed estimates.

THE EFFECTS OF U.S. UNCONVENTIONAL MONETARY POLICY ON ASIAN STOCK MARKETS

2017 ◽  
Vol 65 (04) ◽  
pp. 917-945
Author(s):  
CHIEN-CHIANG LEE ◽  
MEI-PING CHEN ◽  
CHUN-CHIE HUANG
Keyword(s):  
Correlation Coefficients ◽  
Spillover Effects ◽  
Market Liquidity ◽  
Time Varying ◽  
Progressive Decline ◽  
Dynamic Correlation ◽  
Volatility Spillovers ◽  
Specific Factors ◽  
Autoregressive Conditional Heteroscedasticity ◽  
The U.S

To assess the spillover effects of quantitative easing (QE) on return and volatility from the U.S. market to the selected Asian markets, this study applies dynamic correlation coefficient-generalized autoregressive conditional heteroscedasticity model to capture the time-varying nature of return and volatility spillovers during non-QE and QE periods of the sample countries. Furthermore, we incorporate the estimated time-varying correlation coefficients and country-specific factors to probe the determinants of the spillover. We find that the U.S. QE policies have significantly affected the correlations between the U.S. and some Asian countries, to which it performs significantly progressive decline in the correlations during the latest QE. Greater stock market liquidity remarkably increases their financial spillovers.

Intraseasonal and Seasonally Persisting Patterns of Indian Monsoon Rainfall

2007 ◽  
Vol 20 (1) ◽  
pp. 3-20 ◽  
Author(s):  
V. Krishnamurthy ◽  
J. Shukla
Keyword(s):  
Monsoon Rainfall ◽  
Indian Monsoon ◽  
Singular Spectrum Analysis ◽  
Daily Rainfall ◽  
Central India ◽  
North India ◽  
Peninsular India ◽  
Rainfall Analysis ◽  
Intraseasonal Oscillations ◽  
Rainfall Anomalies

Abstract The space–time structure of the active and break periods of the Indian monsoon has been studied using 70-yr-long high-resolution gridded daily rainfall data over India. The analysis of lagged composites of rainfall anomalies based on an objective categorization of active and break phases shows that the active (break) cycle, with an average life of 16 days, starts with positive (negative) rainfall anomalies over the Western Ghats and eastern part of central India and intensifies and expands to a region covering central India and parts of north India during the peak phase, while negative (positive) anomalies cover the sub-Himalayan region and southeast India. During the final stage of the active (break) period, the positive (negative) rainfall anomalies move toward the foothills of the Himalayas while peninsular India is covered with opposite sign anomalies. The number of days on which lows and depressions are present in the region during active and break periods is consistent with the rainfall analysis. The number of depressions during the active phase is about 7 times that during the break phase. Using multichannel singular spectrum analysis of the daily rainfall anomalies, the seasonal monsoon rainfall is found to consist of two dominant intraseasonal oscillations with periods of 45 and 20 days and three seasonally persisting components. The 45- and 20-day oscillations are manifestations of the active and break periods but contribute very little to the seasonal mean rainfall. The seasonally persisting components with anomalies of the same sign, and covering all of India, have a very high interannual correlation with the total seasonal mean rainfall. These results support a conceptual model of the interannual variability of the monsoon rainfall consisting of seasonal mean components and a statistical average of the intraseasonal variations. The success in the prediction of seasonal mean rainfall depends on the relative strengths of the seasonally persisting components and intraseasonal oscillations.

scholarly journals Linking Drought Intensity with Rice Yield in Nagaland

2021 ◽  
Author(s):  
Baiarbor Nongbri ◽  
S.M. Feroze ◽  
Ram Singh ◽  
L.I.P. Ray
Keyword(s):  
Normal Condition ◽  
Drought Index ◽  
Rice Yield ◽  
Linear Trend ◽  
Daily Rainfall ◽  
Annual Rainfall ◽  
Severe Drought ◽  
Drought Intensity ◽  
Rice Yields ◽  
Linear Trends

Background: Rainfall being one of the most important factors of production for rainfed kharif rice, occurrence of drought may have serious implication on rice yield. Hence, this study is an attempt to understand the linkage between drought and yield of rice in Phek and Dimapur district of Nagaland where rice is the primary crop. Methods: Reconnaissance Drought Index was calculated using gridded daily rainfall (0.25o X 0.25o) and temperature (1o X 1o) (o=degree) data for the year of 1975-2013.Result: The annual mean temperature has increased by 0.03oC in Phek and Dimapur district during the study period. The increasing linear trends for annual temperatures are significant whereas, the linear trend for annual rainfall shows decreasing but insignificant trend. About 38.46% and 41.02% of the 39 years under study were ‘Normal condition-dry’ in Phek in Dimapur district, respectively. Moderate and severe drought occurred more frequently in Dimapur than Phek. After 1994, majority of the years were drought years and the frequency of occurrence was higher in Dimapur. The drought occurrences negatively impacted the rice yields and the rice yield may reduce by 13.85% in normal condition dry to 18.45% in extreme drought condition.

Sign in / Sign up

Export Citation Format

Share Document