Observed Changes of Drought/Wetness Episodes in the Middle and Lower Reaches of the Yangtze River, China

2012 ◽  
Vol 212-213 ◽  
pp. 765-771
Author(s):  
Yi Wei Zhang ◽  
Wei Guang Wang
Keyword(s):  
Rainy Season ◽  
Yangtze River ◽  
Standardized Precipitation Index ◽  
Aridity Index ◽  
Monthly Precipitation ◽  
Precipitation Data ◽  
The Yangtze River ◽  
Dry Conditions ◽  
The Standardized Precipitation Index ◽  
Monthly Precipitation Data

Monthly precipitation data of 76 meteorology stations over the middle and lower reaches of Yangtze river for 1961–2010 were analyzed by using the standardized precipitation index (SPI) and aridity index (I) for the rainy season (April–September) and winter (December– February). Trends of the number of wet and dry months were tested with Mann-Kendall technique. The results showed that: (1) The middle and lower reaches of the Yangtze River as a whole has become wetter during the rainy season and winter. (2) Major parts of the study area are characterized by increasing frequencies of severe and moderate wet months in the rainy season. (3) The study tries to explore the spatial and temporal changes in the wet and dry conditions across the middle and lower reaches of the Yangtze River by using SPI and I, and get the complete picture of the change of wet and dry.

scholarly journals Assessing the changes in drought conditions during summer in the Republic of Moldova based on RegCM simulations

2013 ◽  
Vol 2 (3) ◽  
pp. 63 ◽  
Author(s):  
Vera Potop ◽  
Constanta Boroneant ◽  
Mihaela Caian
Keyword(s):  
Standardized Precipitation Index ◽  
Horizontal Resolution ◽  
Precipitation Index ◽  
Monthly Precipitation ◽  
Precipitation Data ◽  
Republic Of Moldova ◽  
Drought Conditions ◽  
The Republic ◽  
The Standardized Precipitation Index ◽  
Monthly Precipitation Data

We assess the changes in drought conditions during summer in the Republic of Moldova based on the Standardized Precipitation Index (SPI) calculated from monthly precipitation data simulated by the regional climatic model RegCM3. The RegCM simulations were conducted at a horizontal resolution of 10 km in the framework of EU-FP6 project -CECILIA. The domain was centered over Romania at 46°N, 25°E and included the Republic of Moldova.

scholarly journals Spatial Downscaling of Tropical Rainfall Measuring Mission (TRMM) Annual and Monthly Precipitation Data over the Middle and Lower Reaches of the Yangtze River Basin, China

Water ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 568 ◽  
Author(s):  
Shaodan Chen ◽  
Liping Zhang ◽  
Dunxian She ◽  
Jie Chen
Keyword(s):  
Spatial Resolution ◽  
Yangtze River ◽  
Vegetation Index ◽  
Yangtze River Basin ◽  
Tropical Rainfall Measuring Mission ◽  
Monthly Precipitation ◽  
Precipitation Data ◽  
The Yangtze River ◽  
The Yangtze River Basin ◽  
Monthly Precipitation Data

Precipitation plays an important role in the global water cycle, in addition to material and energy exchange processes. Therefore, obtaining precipitation data with a high spatial resolution is of great significance. We used a geographically weighted regression (GWR)-based downscaling model to downscale Tropical Rainfall Measuring Mission (TRMM) 3B43 precipitation data over the middle and lower reaches of the Yangtze River Basin (MLRYRB) from a resolution of 0.25° to 1 km on an annual scale, and the downscaled results were calibrated using the geographical differential analysis (GDA) method. At present, either the normalized difference vegetation index (NDVI) or a digital elevation model (DEM) is selected as the environmental variable in the downscaling models. However, studies have shown that the relationship between the NDVI and precipitation gradually weakens when precipitation exceeds a certain threshold. In contrast, the enhanced vegetation index (EVI) overcomes the saturation shortcomings of the NDVI. Therefore, this study investigated the performances of EVI-derived and NDVI-derived downscaling models in downscaling TRMM precipitation data. The results showed that the NDVI performed better than the EVI in the annual downscaling model, possibly because this study used the annual average NDVI, which may have neutralized detrimental saturation effects. Moreover, the accuracy of the downscaling model could be effectively improved after correcting for residuals and calibrating the model with the GDA method. Subsequently, the downscaled rainfall was closer to the actual weather station rainfall observations. Furthermore, the downscaled results were decomposed into fractions to obtain monthly precipitation data, showing that the proposed method by utilizing the GDA method could improve not only the spatial resolution of remote sensing precipitation data, but also the accuracy of data.

scholarly journals Temporal and spatial characteristics of precipitation and droughts in the upper reaches of the Yangtze river basin (China) in recent five decades

2011 ◽  
Vol 14 (1) ◽  
pp. 221-235 ◽  
Author(s):  
Nan Zhang ◽  
Ziqiang Xia ◽  
Shaofeng Zhang ◽  
Hong Jiang
Keyword(s):  
River Basin ◽  
Yangtze River ◽  
Yangtze River Basin ◽  
Standardized Precipitation Index ◽  
Meteorological Drought ◽  
Temporal Variations ◽  
The Yangtze River ◽  
Mk Test ◽  
The Yangtze River Basin ◽  
The Standardized Precipitation Index

Drought is one of the most harmful natural hazards in the Upper Reaches of the Yangtze River basin (URYR) in the mid-west part of China. Alterations in precipitation will affect the severity of drought. The nonparametric Mann–Kendall (MK) test was used in this paper to examine the trend of precipitation and the standardized precipitation index (SPI) was adopted to analyze the spatial–temporal variations of meteorological drought over different time scales in the last 50 years. The MK test value of precipitation indicated that, for most of the URYR showed an increasing trend of precipitation in the months of January, February, March and June, mainly in the Min-Tuojiang, Jialingjiang and Wujiang sub-basins and a decreasing trend was observed in August to December. The most obvious decreasing trend of precipitation occurred in the Jialingjiang, upper mainstream and Wujiang sub-basins in September, with a rate ranging from –7.89mm/10 years to –39.36mm/10 years. The results show that the SPI is applicable in the URYR basin. The number of severe droughts differed among the six sub-basins, i.e., a more obvious 3-month drought takes place in the middle of the upper mainstream, Wujiang sub-basins and the southeast of Jialingjiang sub-basin and other droughts in 6, 9 and 12 month timescales have the same effect in these three sub-basins. The outcomes of the paper could provide references for droughts mitigation, local water resources management and agriculture decision making.

scholarly journals Changes in the frequency and severity of hydrological droughts over Ethiopia from 1960 to 2013

2016 ◽  
Vol 42 (1) ◽  
pp. 145 ◽  
Author(s):  
A. M. El Kenawy ◽  
M. F. McCabe ◽  
S. M. Vicente-Serrano ◽  
J. I. López-Moreno ◽  
S. M. Robaa
Keyword(s):  
Standardized Precipitation Index ◽  
Principal Component ◽  
Research Unit ◽  
Monthly Precipitation ◽  
Precipitation Data ◽  
Policy Makers ◽  
Local Character ◽  
Afar Region ◽  
The Standardized Precipitation Index ◽  
Evidence For Policy

Here we present an analysis of drought occurrence and variability in Ethiopia, based on the monthly precipitation data from the Climate Research Unit (CRU-v3.22) over the period from 1960 to 2013. The drought events were characterized by means of the Standardized Precipitation Index (SPI) applied to precipitation data at a temporal scale of 12 months. At the national scale, the results reveal a statistically significant decrease in the severity of droughts over the 54-year period, a pattern that is mostly attributed to a statistically significant decrease in the frequency of high intensity drought episodes (i.e., extreme and very extreme droughts), compared to moderate droughts. To assess the general patterns of drought evolution, a principal component analysis (PCA) was applied to the SPI series. PCA results indicate a high spatial heterogeneity in the SPI variations over the investigated period, with ten different spatially well-defined regions identified. These PCA components accounted for 72.9% of the total variance of drought in the region. These regions also showed considerable differences in the temporal variability of drought, as most of the regions exhibited an increase in wetness conditions in recent decades. In contrast, the regions that receive less than 400 mm of annual precipitation showed a declining  trend, with the largest changes occurring over Afar region. Generally, the highly elevated regions over the central Ethiopian Highlands showed the weakest changes, compared to the lowlands. This study confirms the local character of drought evolution over Ethiopia, providing evidence for policy makers to adopt appropriate local policies to cope with the risks of drought. Over Ethiopia, the detailed spatial assessment of drought evolution is required for a better understanding of the possible impacts of recurrent drought on agriculture, food production, soil degradation, human settlements and migrations, as well as energy production and water resources management across Ethiopia.

scholarly journals Dry and wet rainy seasons in the Mantaro river basin (Central Peruvian Andes)

2008 ◽  
Vol 14 ◽  
pp. 261-264 ◽  
Author(s):  
Y. Silva ◽  
K. Takahashi ◽  
R. Chávez
Keyword(s):  
River Basin ◽  
Rainy Season ◽  
Southern Oscillation ◽  
Standardized Precipitation Index ◽  
Monthly Precipitation ◽  
Tropical Atlantic ◽  
Peruvian Andes ◽  
Rainfall Season ◽  
Absolute Correlation ◽  
The Standardized Precipitation Index

Abstract. Monthly precipitation data from the period of 1970 to 2004 from 38 meteorological stations in the Mantaro river basin were used to classify the rainy seasons (September–April) of each year into anomalously dry or wet, and to determine the basin-wide extent of the anomalies based on the Standardized Precipitation Index (SPI). The wet periods mostly occurred in the early 1970's and during the first half of the 1980's, except for the event that occurred in the 1993/94 period which was the strongest and most generalized in the analyzed period. The dry periods occurred mostly during the second half of the 1980's and the 1990's. Consistent with this, a negative trend in precipitation of 2% per decade was found for the rainy season, due mainly to a stronger trend (−4%/decade) during the peak phase (January–March). Despite previously reported significant negative correlations between El Niño-Southern Oscillation (ENSO) and rainfall during the peak of the rainfall season, the similar amplitude variability of precipitation during the onset phase of the rainfall season (September–December), which is uncorrelated with ENSO, participate to the reduction of the absolute correlation for the full rainfall season. Correlations between rainfall in the Mantaro basin and sea surface temperature (SST) in the tropical Atlantic are significant only near the end of the rainy season, with more rain associated with a weaker north-south difference in SST in the tropical Atlantic.

Characterizing Germany’s 2018 drought in the context of wet and dry spells since 1901

2021 ◽  
Author(s):  
Mathilde Erfurt ◽  
Rüdiger Glaser ◽  
Kerstin Stahl
Keyword(s):  
Standardized Precipitation Index ◽  
Meteorological Drought ◽  
Precipitation Data ◽  
Economic Sectors ◽  
Study Region ◽  
Precipitation Patterns ◽  
Dry Spells ◽  
Daily Precipitation Data ◽  
Dry Conditions ◽  
The Standardized Precipitation Index

<p>In 2018, large areas of central and northern Europe were affected by an extreme drought. The water deficit propagated through the hydrologic cycle causing precipitation, soil moisture and, towards the end of 2018, streamflow and groundwater deficits. In Germany many socio-economic sectors were severely affected by the drought, e.g. the forestry sector has still not recovered. Main drivers for drought propagation are precipitation deficits. However, the natural variability of dry and wet precipitation patterns over time and space make characterization of droughts and predictions of impacts still challenging.</p><p>This study investigates German meteorological drought characteristics within general wet and dry spells since 1901 using station based daily precipitation data. Daily, monthly and seasonal aggregated indices such as the Standardized Precipitation Index (SPI) were used to characterize duration, severity and spatial extent of the 2018 drought. These characteristics were then compared with events of extreme droughts since 1901. Even though the meteorological drought of 2018 was extreme considering only precipitation data, we found comparable extremes in the past, for instance 1949 or 1964. However, based on what we observe in the SPI-12, clusters of extreme dry years in the 20th century were often followed by clusters of above average wet years, probably leading to a reduction of impacts in the following years. Since 2003, however, dry patterns predominate. Even though annual precipitation amounts are predicted to increase slightly in the study region this analysis shows the importance of analyzing sub annual as well as multi-year characteristics of precipitation patterns.</p><p>Including both wet and dry conditions when characterizing the severity of current drought events may improve our understanding of extreme meteorological drought events causing severe and long lasting impacts.</p>

scholarly journals Seasonal forecasts of droughts in African basins using the Standardized Precipitation Index

2013 ◽  
Vol 17 (6) ◽  
pp. 2359-2373 ◽  
Author(s):  
E. Dutra ◽  
F. Di Giuseppe ◽  
F. Wetterhall ◽  
F. Pappenberger
Keyword(s):  
Real Time ◽  
Lead Time ◽  
Standardized Precipitation Index ◽  
Precipitation Index ◽  
Seasonal Forecasting ◽  
Monthly Precipitation ◽  
Seasonal Forecasts ◽  
Blue Nile ◽  
Forecasting System ◽  
The Standardized Precipitation Index

Abstract. Vast parts of Africa rely on the rainy season for livestock and agriculture. Droughts can have a severe impact in these areas, which often have a very low resilience and limited capabilities to mitigate drought impacts. This paper assesses the predictive capabilities of an integrated drought monitoring and seasonal forecasting system (up to 5 months lead time) based on the Standardized Precipitation Index (SPI). The system is constructed by extending near-real-time monthly precipitation fields (ECMWF ERA-Interim reanalysis and the Climate Anomaly Monitoring System–Outgoing Longwave Radiation Precipitation Index, CAMS-OPI) with monthly forecasted fields as provided by the ECMWF seasonal forecasting system. The forecasts were then evaluated over four basins in Africa: the Blue Nile, Limpopo, Upper Niger, and Upper Zambezi. There are significant differences in the quality of the precipitation between the datasets depending on the catchments, and a general statement regarding the best product is difficult to make. The generally low number of rain gauges and their decrease in the recent years limits the verification and monitoring of droughts in the different basins, reinforcing the need for a strong investment on climate monitoring. All the datasets show similar spatial and temporal patterns in southern and north-western Africa, while there is a low correlation in the equatorial area, which makes it difficult to define ground truth and choose an adequate product for monitoring. The seasonal forecasts have a higher reliability and skill in the Blue Nile, Limpopo and Upper Niger in comparison with the Zambezi. This skill and reliability depend strongly on the SPI timescale, and longer timescales have more skill. The ECMWF seasonal forecasts have predictive skill which is higher than using climatology for most regions. In regions where no reliable near-real-time data is available, the seasonal forecast can be used for monitoring (first month of forecast). Furthermore, poor-quality precipitation monitoring products can reduce the potential skill of SPI seasonal forecasts in 2 to 4 months lead time.

scholarly journals Application of TRMM Precipitation Data to Evaluate Drought and Its Effects on Water Resources Instability

2019 ◽  
Vol 9 (24) ◽  
pp. 5377
Author(s):  
Ata Amini ◽  
Abdolnabi Abdeh Kolahchi ◽  
Nadhir Al-Ansari ◽  
Mehdi Karami Moghadam ◽  
Thamer Mohammad
Keyword(s):  
Water Resources ◽  
Standardized Precipitation Index ◽  
Remote Sensing Data ◽  
Tropical Rainfall Measuring Mission ◽  
Monthly Precipitation ◽  
Precipitation Data ◽  
Discharge Data ◽  
Satellite Precipitation ◽  
Discharge Rates ◽  
Trmm Precipitation

The present research was carried out to study drought and its effects upon water resources using remote sensing data. To this end, the tropical rainfall measuring mission (TRMM) satellite precipitation, the synoptic stations, and fountain discharge data were employed. For monitoring of drought in the study area, in Kermanshah province, Iran, the monthly precipitation data of the synoptic stations along with TRMM satellite precipitation datasets were collected and processed in the geographic information system (GIS) environment. Statistical indicators were applied to evaluate the accuracy of TRMM precipitation against the meteorological stations’ data. Standardized precipitation index, SPI, and normalized fountain discharge were used in the monitoring of drought conditions, and fountains discharge, respectively. The fountains were selected so that in addition to enjoying the most discharge rates, they spread along the study area. The evaluation of precipitation data showed that the TRMM precipitation data were of high accuracy. Studies in temporal scale are indicative of the strike of drought in this region to the effect that for most months of the year, frequency and duration in dry periods are much more than in wet periods. As for seasonal scales, apart from winter, the frequency and duration of drought in spring and autumn have been longer than in wet years. Moreover, the duration of these periods was different. A comparison between the results of changes in fountain discharges and drought index in the region has verified that the drought has caused a remarkable decline in the fountain discharges.

scholarly journals Analysis of Drought in the Northern Region of Bangladesh Using Standardized Precipitation Index (SPI)

2019 ◽  
Vol 11 (1-2) ◽  
pp. 199-216
Author(s):  
R Afrin ◽  
F Hossain ◽  
SA Mamun
Keyword(s):  
Standardized Precipitation Index ◽  
Extended Period ◽  
Northern Region ◽  
Precipitation Index ◽  
Rainfall Data ◽  
Extreme Drought ◽  
Severe Drought ◽  
Drought Analysis ◽  
Dry Conditions ◽  
The Standardized Precipitation Index

Drought is an extended period when a region notes a deficiency in its water supply. The Standardized Precipitation Index (SPI) method was used in this study to analyze drought. Northern region of Bangladesh was the area of study. Monthly rainfall data of northern region of Bangladesh was obtained from the Meteorological Department of Bangladesh. Obtained rainfall data was from 1991 to 2011 and values from 2012 to 2026 were generated using Markov model. Then SPI values from 1991 to 2026 were calculated by using SPI formula for analyzing drought. Analysis with SPI method showed that droughts in northern region of Bangladesh varied from moderately dry to severely dry conditions and it may vary from moderately dry to severely dry conditions normally in future but in some cases extreme drought may also take place. From the study, it is observed that the northern region of Bangladesh has already experienced severe drought in 1991, 1992, 1994, 1995, 1997, 1998, 2000, 2003, 2005, 2007, 2009 and 2010. The region may experience severe drought in 2012, 2015, 2016, 2018, 2019, 2021, 2022, 2023, 2024, 2025 and 2026 and extreme drought in 2012, 2014, 2016, 2023 and 2024. J. Environ. Sci. & Natural Resources, 11(1-2): 199-216 2018

scholarly journals Using CHIRPS Dataset to Assess Wet and Dry Conditions along the Semiarid Central-Western Argentina

2019 ◽  
Vol 2019 ◽  
pp. 1-18 ◽  
Author(s):  
Juan A. Rivera ◽  
Sofía Hinrichs ◽  
Georgina Marianetti
Keyword(s):  
Standardized Precipitation Index ◽  
Warm Season ◽  
Cold Season ◽  
Temporal Features ◽  
Dry Conditions ◽  
Central Western Argentina ◽  
Zero Values ◽  
The Standardized Precipitation Index ◽  
Precipitation Records

The Climate Hazards group Infrared Precipitation with Stations (CHIRPS) dataset was conceived as a tool for monitoring drought and environmental change over land. Recent validation efforts along South America have assessed its suitability for reproducing the main spatial and temporal features of precipitation. Nevertheless, little has been done regarding the ability of CHIRPS for the assessment of wet and dry conditions, particularly in areas where in situ precipitation records are scarce. In this paper, we investigated the performance of CHIRPS for monitoring wet and dry events along the semiarid Central-Western Argentina. Using the Standardized Precipitation Index (SPI), we compared the CHIRPS database with records from 49 meteorological stations along the study area for the period 1987–2016. Results indicate that the CHIRPS dataset adequately reproduced the temporal variability of SPI on multiple timescales (1 month, 3 months, and 6 months), particularly in the region dominated by warm season precipitation. The large overestimation of the seasonal precipitation in the region dominated by cold season precipitation can introduce errors that are reflected in the performance of CHIRPS over the western portion of the domain. The frequency of wet and dry classes was accurately reproduced by CHIRPS on timescales larger than 1 month (SPI1), given the existence of a wet bias that produces an underestimation of the frequency of zero values. This bias is further translated to the evaluation of the SPI1 during the spatial and temporal assessment of historical dry (1998) and wet (2016) events, especially for the classification of extreme dry/wet months. The results from the evaluation indicate that CHIRPS is a suitable tool for assessing dry and wet conditions for timescales longer than 1 month and can support decision-making process within the hydrometeorological agencies over the region.

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