scholarly journals Uncertainty in Drought Identification Due to Data Choices, and the Value of Triangulation

2021 ◽  
Author(s):  
Pius Borona ◽  
Friedrich Busch ◽  
Tobias Krüger ◽  
Philippe Rufin
Keyword(s):  
Arid Regions ◽  
Annual Variation ◽  
Ecological Integrity ◽  
Eastern Africa ◽  
Ground Station ◽  
Rainfed Farming ◽  
Dry Conditions ◽  
Decisive Action ◽  
Aid Decision ◽  
Drought Occurrence

Abstract: Droughts are complex and gradually evolving conditions of extreme water deficits which can compromise livelihoods and ecological integrity, especially in fragile arid and semi-arid regions that depend on rainfed farming, such as Kitui West in south-eastern Kenya. Against the background of low ground-station density, 10 gridded rainfall products and four gridded temperature products were used to generate an ensemble of 40 calculations of the Standardized Precipitation Evapotranspiration Index (SPEI) to assess uncertainties in the onset, duration and magnitude of past droughts. These uncertainties were driven more by variations between the rainfall products than variations between the temperature products. Remaining ambiguities in drought occurrence could be resolved by complementing the quantitative analysis with ground-based information from key informants engaged in disaster relief, effectively formulating an ensemble approach to SPEI-based drought identification to aid decision making. The reported trend towards drier conditions in Eastern Africa was confirmed for Kitui West by the majority of data products, whereas the rainfall effect on the increasingly dry conditions was more subtle than annual and seasonal declines and greater annual variation, which warrants further investigation. Nevertheless, the effects of increasing droughts are already felt on the ground and warrant decisive action.

scholarly journals Uncertainty in Drought Identification Due to Data Choices, and The Value of Triangulation

Water ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 3611
Author(s):  
Pius Borona ◽  
Friedrich Busch ◽  
Tobias Krueger ◽  
Philippe Rufin
Keyword(s):  
Arid Regions ◽  
Annual Variation ◽  
Ecological Integrity ◽  
Eastern Africa ◽  
Ground Station ◽  
Rainfed Farming ◽  
Dry Conditions ◽  
Decisive Action ◽  
Aid Decision ◽  
Drought Occurrence

Droughts are complex and gradually evolving conditions of extreme water deficits which can compromise livelihoods and ecological integrity, especially in fragile arid and semi-arid regions that depend on rainfed farming, such as Kitui West in south-eastern Kenya. Against the background of low ground-station density, 10 gridded rainfall products and four gridded temperature products were used to generate an ensemble of 40 calculations of the Standardized Precipitation Evapotranspiration Index (SPEI) to assess uncertainties in the onset, duration, and magnitude of past droughts. These uncertainties were driven more by variations between the rainfall products than variations between the temperature products. Remaining ambiguities in drought occurrence could be resolved by complementing the quantitative analysis with ground-based information from key informants engaged in disaster relief, effectively formulating an ensemble approach to SPEI-based drought identification to aid decision making. The reported trend towards drier conditions in Eastern Africa was confirmed for Kitui West by the majority of data products, whereby the rainfall effect on those increasingly dry conditions was subtler than just annual and seasonal declines and greater annual variation of rainfall, which requires further investigation. Nevertheless, the effects of increasing droughts are already felt on the ground and warrant decisive action.

scholarly journals Water restriction in cowpea plants [Vigna unguiculata (L.) Walp.]: Metabolic changes and tolerance induction

2022 ◽  
Vol 26 (3) ◽  
pp. 190-197
Author(s):  
Alberto S. de Melo ◽  
Yuri L. Melo ◽  
Claudivan F. de Lacerda ◽  
Pedro R. A. Viégas ◽  
Rener L. de S. Ferraz ◽  
...  
Keyword(s):  
Arid Regions ◽  
Global Climate ◽  
Tolerance Induction ◽  
Potassium Nitrate ◽  
Stress Factors ◽  
Water Restriction ◽  
Clear Vision ◽  
Rainfed Farming ◽  
Semi Arid Region ◽  
Semi Arid

ABSTRACT Global climate change tends to intensify water unavailability, especially in semi-arid regions, directly impacting agricultural production. Cowpea is one of the crops with great socio-economic importance in the Brazilian semi-arid region, cultivated mainly under rainfed farming and considered moderately tolerant to water restriction. This species has physiological and biochemical mechanisms of adaptation to these stress factors, but there is still no clear vision of how these responses can not only allow survival, but also ensure yield advances in the field. Besides acclimation mechanisms, the exogenous application of abiotic (salicylic acid, silicon, proline, methionine, and potassium nitrate) and biotic (rhizobacteria) elicitors is promising in mitigating the effects of water restriction. The present literature review discusses the acclimation mechanisms of cowpea and some cultivation techniques, especially the application of elicitors, which can contribute to maintaining crop yield under different water scenarios. The application of elicitors is an alternative way to increase the sustainability of production in rainfed farming in semi-arid regions. However, the use of eliciting substances in cowpea still needs to be carefully explored, given the difficulties caused by genotypic and edaphoclimatic variability under field conditions.

scholarly journals Possible Causes of the Variation in Microparticle Concentration in an Ice Core from Mizuho Station, Antarctica

1982 ◽  
Vol 3 ◽  
pp. 107-112 ◽  
Author(s):  
Yoshiyuki Fujii ◽  
Tetsuo Ohata
Keyword(s):  
Annual Cycle ◽  
Arid Regions ◽  
Annual Variation ◽  
Ice Core ◽  
Ice Cores ◽  
Layer Formation ◽  
Snow Layer ◽  
Discontinuous Surface ◽  
Surface Snow ◽  
Surface Layer Formation

Variation of the microparticle concentration in an ice core from Mizuho station, East Antarctica, does not show the annual cycle that has been demonstrated for ice cores from Antarctica and Greenland by other authors. Possible reasons for the lack of a annual cycle are considered and two causes are suggested. (1) Semi-annual variation of microparticle concentration as observed in drift-snow. The low particle concentration in March and in August to October is not due to minor particle transport, but to the dilution of microparticles transported mainly from arid regions in the southern hemisphere through the troposphere by falling snow. (2) Discontinuous surface-layer formation. A seasonal or an annual sequence of the variation in microparticle concentration in surface snow layers may be interrupted by the absence of surface snow-layer formation.

Insights into the African Humid Period from fossil stromatolites and Etheria elliptica shells from the Chew Bahir Basin, southern Ethiopia

2020 ◽  
Author(s):  
Peter Nickolaus ◽  
Monika Markowska ◽  
Hubert Vonhof ◽  
Hervé Bocherens ◽  
Ashley Martin ◽  
...  
Keyword(s):  
Temporal Resolution ◽  
Linear Trend ◽  
Eastern Africa ◽  
Southern Ethiopia ◽  
Rift System ◽  
High Temporal Resolution ◽  
East African Rift System ◽  
Climate Conditions ◽  
Dry Conditions ◽  
Humid Period

<p>In the context of human evolution and dispersal in Africa, it is important to understand past climate conditions and changes as possible drivers of these processes. One of the most recent climatic events was the end of the African Humid Period (AHP) at around 5 ka BP. This was marked by a decrease in precipitation following a long wet-phase in northern and eastern Africa, which caused many lakes to decrease in size or even desiccate. Although the termination of the AHP is well known, the timing and rate of the transition from wet to dry conditions is still heavily debated. To investigate the termination of the AHP at a high temporal resolution (subdecadal and subannual), fossil stromatolites and <em>Etheria elliptica</em> shells from paleo-shorelines in the Chew Bahir Basin, southern Ethiopia, were collected. Today, Lake Chew Bahir is a deltaic swamp, however in past pluvials a large lake was present that likely overflowed and connected to other basins similar to other amplifier lakes in the East African Rift System. Radiocarbon dating, oxygen and carbon stable isotope analyses, trace element analyses and petrographic mapping of stromatolite laminae structure were conducted. A strong correlation between δ<sup>18</sup>O and δ<sup>13</sup>C shows that paleo-lake Chew Bahir likely experienced highly evaporative conditions and indicate an endorheic state of the basin in times of stromatolite growth at 7.1, 5.8, 4.7 and 4.6 ka BP. Furthermore, our findings suggest highly fluctuating environmental conditions during these times and demonstrate that the transition to drier conditions was not a strictly linear trend. In summary, the stromatolites and <em>Etheria elliptica</em> shells are an excellent environmental archive due to their high temporal resolution, precise dating (± 30 yrs) and an indication of the paleo-lake water depth. These types of records provide insights to past changes in freshwater availability, the variability of which would have had large consequences for humans living in the region.</p>

Ceratitis rosa (Natal fruit fly).

2021 ◽  
Author(s):  
Marc De Meyer
Keyword(s):  
Invasive Species ◽  
Host Plants ◽  
Ceratitis Capitata ◽  
Fruit Fly ◽  
Eastern Africa ◽  
African Species ◽  
The World ◽  
Dry Conditions ◽  
Major Pest ◽  
Environmental Requirements

Abstract C. rosa is a polyphagous African species. Its known distribution is mainly southern and eastern Africa. It is considered to be a major pest of a number of commercial fruits, including fruits that are grown in subtropical or more temperate environments (but see remark under host plants). It has similar environmental requirements to Ceratitis capitata except that it can withstand less dry conditions. It should be considered as a potential invasive species in other parts of Africa, outside its current range, and in other parts of the world (Tanga et al., 2018). The most likely pathway of dispersal and introduction is as larvae in infested fruits with commercial shipments or in the luggage of travellers. C. rosa is of quarantine significance for EPPO, JUNAC and OIRSA.

Dust storm frequency in relation to extreme droughts in arid regions of Iran

2021 ◽  
Author(s):  
reza modarres ◽  
Poria Mohit Esfahani
Keyword(s):  
Dust Storm ◽  
Arid Regions ◽  
Standardized Precipitation Index ◽  
Joint Probability ◽  
Climatic Conditions ◽  
Dust Storms ◽  
Drought Event ◽  
Drought Condition ◽  
Copula Functions ◽  
Dry Conditions

<p>Dust storms are frequent phenomenon in arid and semi arid regions of Iran which cover near 60 percent of the entire country in the center of Iran. Due to geographic and climatic conditions of prolonged dry conditions as well as poor land use management, dust storms occur in almost all seasons across the region. Drought is a major fator affecting the likelihood of dust storm occurrence across arid regions of Iran. We develop copula functions to investigate the effect of drought on dust storm frequency.The standardized precipitation Index (SPI) was caluclated and drought condition was defined based on SPI< -0.5. Dought severity and duration for each drought event were ca;culated and the number of dust days in each drought event ws also identified. The Archimedean copula families shoed that the probability of dust occurrence has a significant relationship to extreme drought conditions. The joint probability is then used to derive the joint return period of dust storms in relation to drought condition.</p>

scholarly journals Possible Causes of the Variation in Microparticle Concentration in an Ice Core from Mizuho Station, Antarctica

1982 ◽  
Vol 3 ◽  
pp. 107-112 ◽  
Author(s):  
Yoshiyuki Fujii ◽  
Tetsuo Ohata
Keyword(s):  
Annual Cycle ◽  
Arid Regions ◽  
Annual Variation ◽  
Ice Core ◽  
Ice Cores ◽  
Layer Formation ◽  
Snow Layer ◽  
Discontinuous Surface ◽  
Surface Snow ◽  
Surface Layer Formation

Variation of the microparticle concentration in an ice core from Mizuho station, East Antarctica, does not show the annual cycle that has been demonstrated for ice cores from Antarctica and Greenland by other authors. Possible reasons for the lack of a annual cycle are considered and two causes are suggested. (1) Semi-annual variation of microparticle concentration as observed in drift-snow. The low particle concentration in March and in August to October is not due to minor particle transport, but to the dilution of microparticles transported mainly from arid regions in the southern hemisphere through the troposphere by falling snow. (2) Discontinuous surface-layer formation. A seasonal or an annual sequence of the variation in microparticle concentration in surface snow layers may be interrupted by the absence of surface snow-layer formation.

scholarly journals Assessment of Hydromorphological Characteristics in Sakarya Watershed, Turkey

10.29007/gshk ◽  
2018 ◽  
Author(s):  
Cansu Özcan ◽  
Elçin Kentel ◽  
Emre Alp
Keyword(s):  
Ecological Integrity ◽  
Hydrological Regime ◽  
Hydrologic Model ◽  
Decision Makers ◽  
Anthropogenic Pressures ◽  
Aquatic Life ◽  
Gis And Remote Sensing ◽  
The Status ◽  
Aid Decision ◽  
Management Alternatives

Hydromorphology is one of the key components of ecological integrity of a waterbody according to European Union Water Framework Directive (WFD). Therefore, hydromorphological quality assessment plays a significant role in evaluating the status of aquatic life. The aim of this study is to assess hydromorphological characteristics of Sakarya Watershed where hydromorphological alteration and anthropogenic pressures are significant. Morphological conditions of the streams, river continuity and hydrological regime are evaluated. In this study, hydrological foundation of the assessment is established using a hydrologic model, Water Evaluation and Planning Model (WEAP). Moreover, Geographic Information System (GIS) and Remote Sensing (RS) tools in addition to field surveys are used in the spatial and temporal evaluation of the hydromorphological characteristics in the study area. It is believed that the outcomes of this study will aid decision makers to develop sustainable management alternatives to improve ecological integrity in Sakarya Watershed.

scholarly journals Changes in Drought Characteristics over China Using the Standardized Precipitation Evapotranspiration Index

2015 ◽  
Vol 28 (13) ◽  
pp. 5430-5447 ◽  
Author(s):  
Huopo Chen ◽  
Jianqi Sun
Keyword(s):  
Arid Regions ◽  
Southern China ◽  
Northern China ◽  
Standardized Precipitation Evapotranspiration Index ◽  
The Past ◽  
Drought Characteristics ◽  
Temperature And Precipitation ◽  
Decadal Variations ◽  
Dry Conditions ◽  
Precipitation Anomalies

Abstract The standardized precipitation evapotranspiration index (SPEI) is computed and compared in China using reference evapotranspiration calculated using the Thornthwaite (TH) approach and the Penman–Monteith (PM) equation. The analysis reveals that SPEI_PM outperforms the SPEI_TH with regard to drought monitoring during the period 1961–2012 over China, especially in arid regions of China. Furthermore, the SPEI_PM also performs better with regard to observed variations in soil moisture and streamflow in China. Thus, changes in drought characteristics over China are detected on the basis of variations in the SPEI_PM. The results indicate that droughts over China exhibit pronounced decadal variations over the past 50 yr, with more frequent and severe droughts occurring before the 1980s and in the 2000s compared with the 1980s and 1990s. Since the late 1990s, droughts have become more frequent and severe across China, especially in some regions of northern China. Concurrently, consecutive drought events have also increased across China. This suggests that dry conditions in China have been enhanced in recent years. Further analyses illustrate that the temperature and precipitation anomalies exhibit different roles in detecting droughts across China, which is primarily due to the magnitude of their variations and different climate variability. Considering temperature and precipitation perturbations, droughts exhibit relatively larger responses to temperature fluctuations in northern China and relatively larger responses to precipitation anomalies in southern China.

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