scholarly journals Investigation of Precipitation Variability and Extremes Using Information Theory

2020 ◽  
Vol 4 (1) ◽  
pp. 14 ◽  
Author(s):  
Ravi Kumar Guntu ◽  
Ankit Agarwal
Keyword(s):  
Information Theory ◽  
Spatial Patterns ◽  
Hydrological Cycle ◽  
Rainfall Variability ◽  
Central India ◽  
Rainfall Amount ◽  
Spatiotemporal Variability ◽  
Spatial And Temporal Variability ◽  
Seasonal Scale ◽  
The Impact

Quantifying the spatiotemporal variability of rainfall is the principal component for the assessment of the impact of climate change on the hydrological cycle. A better understanding of the quantification of variability and its trend is vital for water resources planning and management. Therefore, a multitude of studies has been dedicated to quantifying the rainfall variability over the years. Despite their importance for modelling rainfall variability, the studies mainly focused on the amount of rainfall and its spatial patterns. The studies investigating the spatial and temporal variability of rainfall across Central India, in general, and at multiscale, in particular, are limited. In this study, we used a Standardized Variability Index (SVI), based on information theory to investigate the spatiotemporal variability of rainfall. SVI is independent of the temporal scale, length of the data and can compare the rainfall variability at multiple timescales. Distinct spatial patterns were observed for information entropies at the monthly and seasonal scale. Grid points with statistically significant trends were observed and vary from monthly to seasonal scale. There is an increase in the variability of rainfall amount from South to North, indicating that spread of the rainfall is high in the South when compared to North of Central India. Trend analysis revealed there is changing behavior in the rainfall amount as well as rainy days, showing an increase in variability of rainfall over Central India, hence the high probability of occurrence of extreme events in the near future.

scholarly journals No growth stimulation of Canada’s boreal forest under half-century of combined warming and CO2 fertilization

2016 ◽  
Vol 113 (52) ◽  
pp. E8406-E8414 ◽  
Author(s):  
Martin P. Girardin ◽  
Olivier Bouriaud ◽  
Edward H. Hogg ◽  
Werner Kurz ◽  
Niklaus E. Zimmermann ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Boreal Forest ◽  
Spatial Patterns ◽  
Tree Growth ◽  
Hydrological Cycle ◽  
Forest Growth ◽  
Spatiotemporal Variability ◽  
Late 20Th Century ◽  
Growth Trends ◽  
Growth Variability

Considerable evidence exists that current global temperatures are higher than at any time during the past millennium. However, the long-term impacts of rising temperatures and associated shifts in the hydrological cycle on the productivity of ecosystems remain poorly understood for mid to high northern latitudes. Here, we quantify species-specific spatiotemporal variability in terrestrial aboveground biomass stem growth across Canada’s boreal forests from 1950 to the present. We use 873 newly developed tree-ring chronologies from Canada’s National Forest Inventory, representing an unprecedented degree of sampling standardization for a large-scale dendrochronological study. We find significant regional- and species-related trends in growth, but the positive and negative trends compensate each other to yield no strong overall trend in forest growth when averaged across the Canadian boreal forest. The spatial patterns of growth trends identified in our analysis were to some extent coherent with trends estimated by remote sensing, but there are wide areas where remote-sensing information did not match the forest growth trends. Quantifications of tree growth variability as a function of climate factors and atmospheric CO2 concentration reveal strong negative temperature and positive moisture controls on spatial patterns of tree growth rates, emphasizing the ecological sensitivity to regime shifts in the hydrological cycle. An enhanced dependence of forest growth on soil moisture during the late-20th century coincides with a rapid rise in summer temperatures and occurs despite potential compensating effects from increased atmospheric CO2 concentration.

scholarly journals The role of storm scale, position and movement in controlling urban flood response

2018 ◽  
Vol 22 (1) ◽  
pp. 417-436 ◽  
Author(s):  
Marie-Claire ten Veldhuis ◽  
Zhengzheng Zhou ◽  
Long Yang ◽  
Shuguang Liu ◽  
James Smith
Keyword(s):  
Spatial Scales ◽  
Rainfall Variability ◽  
Flow Path ◽  
Spatial And Temporal Variability ◽  
Hydrological Response ◽  
Radar Rainfall ◽  
Peak Flows ◽  
Basin Scale ◽  
Urban Catchments ◽  
The Impact

Abstract. The impact of spatial and temporal variability of rainfall on hydrological response remains poorly understood, in particular in urban catchments due to their strong variability in land use, a high degree of imperviousness and the presence of stormwater infrastructure. In this study, we analyze the effect of storm scale, position and movement in relation to basin scale and flow-path network structure on urban hydrological response. A catalog of 279 peak events was extracted from a high-quality observational dataset covering 15 years of flow observations and radar rainfall data for five (semi)urbanized basins ranging from 7.0 to 111.1 km2 in size. Results showed that the largest peak flows in the event catalog were associated with storm core scales exceeding basin scale, for all except the largest basin. Spatial scale of flood-producing storm events in the smaller basins fell into two groups: storms of large spatial scales exceeding basin size or small, concentrated events, with storm core much smaller than basin size. For the majority of events, spatial rainfall variability was strongly smoothed by the flow-path network, increasingly so for larger basin size. Correlation analysis showed that position of the storm in relation to the flow-path network was significantly correlated with peak flow in the smallest and in the two more urbanized basins. Analysis of storm movement relative to the flow-path network showed that direction of storm movement, upstream or downstream relative to the flow-path network, had little influence on hydrological response. Slow-moving storms tend to be associated with higher peak flows and longer lag times. Unexpectedly, position of the storm relative to impervious cover within the basins had little effect on flow peaks. These findings show the importance of observation-based analysis in validating and improving our understanding of interactions between the spatial distribution of rainfall and catchment variability.

Assessing the impact of climate and land-use change on the hydrological response of the upper Betwa River basin

2021 ◽  
Author(s):  
Amit Kumar ◽  
Kumar Gaurav
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
River Basin ◽  
Assessment Tool ◽  
Hydrological Cycle ◽  
Central India ◽  
Hydrological Response ◽  
Open Land ◽  
The Mean ◽  
The Impact

<p>Climate and land-use change have altered the regional hydrological cycle. As a result, the mean summer monsoon rainfall has decreased by 10 % over central India during 1950-2015. This study evaluates the combined effect of climate and land-use change on the hydrological response of the upper Betwa River basin in Central India. We use Landsat satellite images from 1990 to 2018 to compute the changes in various land-use types; waterbody, built-up, forest, agriculture, and open land. In the past two decades, we found that the water body, built-up, and cropland have increased by 63 %, 65 %, and 3 %, respectively. However, forest and open land have decreased by 16 % and 23 %. Further, we observed a significant increase in annual average temperature and a decrease in the mean rainfall in the study area during 1980-2018.</p><p>We then coupled the land-use change with weather parameters (precipitation, temperature, wind speed, solar radiation, and relative humidity) and setup the SWAT (Soil and water assessment tool) model to simulate the hydrological responses in the catchment. We have run this model for two different time steps, 1980-2000 and 1998-2018, using the land-use of 1990 and 2018. Calibration and validation are performed for (1991-1994, 2000-2004) and (1995-1998, 2005-2008) respectively using SUFI-2 method. Our results show that the surface runoff and percolation decreased by -21 and -9 %, whereas evapotranspiration increased by 3 % in the upper Betwa River basin during 2001-2018. A decrease in rainfall, runoff, and percolation will have considerable implications on regional water security.</p>

scholarly journals Characterization of Turbulent Latent and Sensible Heat Flux Exchange between the Atmosphere and Ocean in MERRA

2012 ◽  
Vol 25 (3) ◽  
pp. 821-838 ◽  
Author(s):  
J. Brent Roberts ◽  
Franklin R. Robertson ◽  
Carol A. Clayson ◽  
Michael G. Bosilovich
Keyword(s):  
Surface Wind ◽  
Turbulent Fluxes ◽  
Surface Fluxes ◽  
Spatiotemporal Variability ◽  
Western Boundary ◽  
Spatial And Temporal Variability ◽  
Sensible Heat ◽  
Near Surface ◽  
Heat And Moisture ◽  
The Impact

Abstract Turbulent fluxes of heat and moisture across the atmosphere–ocean interface are fundamental components of the earth’s energy and water balance. Characterizing both the spatiotemporal variability and the fidelity of these exchanges of heat and moisture is critical to understanding the global water and energy cycle variations, quantifying atmosphere–ocean feedbacks, and improving model predictability. This study examines the veracity of the recently completed NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) product in terms of its turbulent surface fluxes. This assessment employs a large dataset of directly measured turbulent fluxes as well as other turbulent surface flux datasets. The spatial and temporal variability of the surface fluxes are examined in terms of their annual-mean climatologies, their seasonal covariability of near-surface bulk parameters, and their representation of extremes. The impact of data assimilation on the near-surface parameters is assessed through evaluation of the incremental analysis update tendencies. It is found that MERRA turbulent surface fluxes are relatively accurate for typical conditions but have systematically weak vertical gradients in moisture and temperature and a weaker covariability between the near-surface gradients and wind speed than found in observations. This results in an underestimate of the surface latent and sensible heat fluxes over the western boundary current and storm-track regions. The assimilation of observations generally acts to bring MERRA closer to observational products by increasing moisture and temperature near the surface and decreasing the near-surface wind speeds.

scholarly journals The role of storm dynamics and scale in controlling urban flood response

2017 ◽  
Author(s):  
Marie-Claire ten Veldhuis ◽  
Zhengzheng Zhou ◽  
Long Yang ◽  
Shuguang Liu ◽  
James Smith
Keyword(s):  
Spatial Distribution ◽  
Spatial Scales ◽  
Rainfall Variability ◽  
Spatial And Temporal Variability ◽  
Hydrological Response ◽  
Radar Rainfall ◽  
Peak Flows ◽  
Basin Scale ◽  
Urban Catchments ◽  
The Impact

Abstract. The impact of spatial and temporal variability of rainfall on hydrological response remains poorly understood, in particular in urban catchments due to their high variability in land-use, high degree of imperviousness and the presence of stormwater infrastructure. In this study, we analyse the effect of rainfall spatial distribution with respect to basin scale and flowpath network structure on urban hydrological response based on a large, high quality observational dataset. A catalog of 279 peak events was extracted from 15 years of high resolution flow observations and radar rainfall data for five (semi)urbanised basins ranging from 7.0 to 111.1 km2 in size. Results showed that largest peak flows in the event catalog were associated with storm core scales exceeding basin scale, for all except the largest basin. Spatial scale of flood-producing storm events in the smaller basins fell into two groups: storms of large spatial scales exceeding basin size or small, concentrated events, with storm core much smaller than basin size. For the majority of events, spatial rainfall variability was strongly smoothed by the flowpath network, increasingly so for larger basin size. Correlation analysis showed that position of the storm in relation to the flowpath network was significantly correlated with peak flow in the smallest and in the two more urbanised basins. Analysis of storm movement relative to the flow path network showed that direction of storm movement, upstream or downstream relative to the flowpath network, had little influence on hydrological response variability. Slow-moving storms tend to be associated with higher peak flows and longer lag times. Unexpectedly, spatial distribution of imperviousness along the flowpath network did not significantly alter hydrological response in relation to spatial storm characteristics. These findings show the importance of observation-based analysis in validating and improving our understanding of interactions between rainfall and catchment variability.

scholarly journals Rainfall Variability and Adaptation of Tomatoes Farmers in Santa: Northwest Region of Cameroon

2021 ◽  
pp. 699-711
Author(s):  
Majoumo Christelle Malyse
Keyword(s):  
Rainfall Variability ◽  
Spatiotemporal Variability ◽  
Annual Rainfall ◽  
Crop Failure ◽  
Rainfall Events ◽  
North West ◽  
Market Gardening ◽  
The Government ◽  
Northwest Region ◽  
The Impact

AbstractThe Santa agrarian basin being one of the main market gardening basins in Cameroon and one of the producers of tomatoes in the country is vulnerable to the impact of rainfall variability. The spatiotemporal variability of rainfall through the annual, monthly, and daily fluctuations has greatly affected the market gardening sector in general and tomatoes production in particular. Thus, given rise to the research topic “Rainfall variability and adaptation of tomatoes farmers in Santa North west region of Cameroon,” its principal objective is to contribute to better understanding of the recent changes occurring in tomatoes production and productivity in Santa. To attain this objective, a principal hypothesis was formulated that rainfall variability instead of unnatural conditions or human constraints justifies changes observed in tomatoes production in Santa and resulting adaptation strategies developed by peasants and stakeholders.Our study came out with several findings, among which includes rainfall events in Santa fluctuate in time and in space with reduction in the number of rainy day and increase in the intensity of rainfall events causing soil erosion, infertility, and frequent crop diseases, insects, and pests. Extreme events such as drought and flooding have equally become frequent in the area especially during the different cycles of tomatoes production disrupting the agricultural calendar and causing crop failure and decrease in yields with Pearson’s correlation of 0.017. This positive value shows that there is a relationship between annual rainfall and tomatoes output in Santa. Tomatoes farmers in Santa are struggling to adapt locally to this situations, but their efforts are still limited especially due to their low level of education and poverty. Finally, it was seen that the output of tomatoes over the years in Santa has a strong correlation with rainfall. Based on the findings of this study, the government is called upon to assist farmers in their adaptation options.

scholarly journals India’s Commitments to Increase Tree and Forest Cover: Consequences for Water Supply and Agriculture Production within the Central Indian Highlands

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 959
Author(s):  
Benjamin Clark ◽  
Ruth DeFries ◽  
Jagdish Krishnaswamy
Keyword(s):  
Groundwater Recharge ◽  
Forest Cover ◽  
Hydrological Modeling ◽  
Monsoon Season ◽  
Forest Policy ◽  
Central India ◽  
Field Measurements ◽  
Tree Cover ◽  
Policy Goals ◽  
The Impact

As part of its nationally determined contributions as well as national forest policy goals, India plans to boost tree cover to 33% of its land area. Land currently under other uses will require tree-plantations or reforestation to achieve this goal. This paper examines the effects of converting cropland to tree or forest cover in the Central India Highlands (CIH). The paper examines the impact of increased forest cover on groundwater infiltration and recharge, which are essential for sustainable Rabi (winter, non-monsoon) season irrigation and agricultural production. Field measurements of saturated hydraulic conductivity (Kfs) linked to hydrological modeling estimate increased forest cover impact on the CIH hydrology. Kfs tests in 118 sites demonstrate a significant land cover effect, with forest cover having a higher Kfs of 20.2 mm hr−1 than croplands (6.7mm hr−1). The spatial processes in hydrology (SPHY) model simulated forest cover from 2% to 75% and showed that each basin reacts differently, depending on the amount of agriculture under paddy. Paddy agriculture can compensate for low infiltration through increased depression storage, allowing for continuous infiltration and groundwater recharge. Expanding forest cover to 33% in the CIH would reduce groundwater recharge by 7.94 mm (−1%) when converting the average cropland and increase it by 15.38 mm (3%) if reforestation is conducted on non-paddy agriculture. Intermediate forest cover shows however shows potential for increase in net benefits.

scholarly journals The Role of Mesoscale Convective Complexes in Southern Africa Summer Rainfall

2013 ◽  
Vol 26 (5) ◽  
pp. 1654-1668 ◽  
Author(s):  
R. C. Blamey ◽  
C. J. C. Reason
Keyword(s):  
South Africa ◽  
Southern Africa ◽  
Rainfall Variability ◽  
Warm Season ◽  
Tropical Rainfall Measuring Mission ◽  
Summer Rainfall ◽  
Spatial And Temporal Variability ◽  
Eastern Region ◽  
Southwest Indian Ocean ◽  
Mesoscale Convective

Abstract A combination of numerous factors, including geographic position, regional orography, and local sea surface temperatures, means that subtropical southern Africa experiences considerable spatial and temporal variability in rainfall and is prone to both frequent flooding and drought events. One system that may contribute to rainfall variability in the region is the mesoscale convective complex (MCC). In this study, Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) data is used to document the precipitation produced by MCCs over southern Africa for the 1998–2006 period. Most of the rainfall associated with MCCs is found to occur over central Mozambique, extending southward to eastern South Africa. High precipitation totals associated with these systems also occur over the neighboring southwest Indian Ocean, particularly off the northeast coast of South Africa. MCCs are found to contribute up to 20% of the total summer rainfall (November–March) in parts of the eastern region of southern Africa. If the month of March is excluded from the analysis, then the contribution increases up to 24%. In general, the MCC summer rainfall contribution for most of the eastern region is approximately between 8% and 16%. Over the western interior and Botswana and Namibia, the MCC contribution is much less (<6%). It is also evident that there is considerable interannual variability associated with the contribution that these systems make to the total warm season rainfall.

scholarly journals Natural and Managed Grasslands Productivity during Multiyear in Ex-Arable Lands (in the Context of Climate Change)

Agriculture ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 215
Author(s):  
Liudmila Tripolskaja ◽  
Asta Kazlauskaite-Jadzevice ◽  
Virgilijus Baliuckas ◽  
Almantas Razukas
Keyword(s):  
Climate Change ◽  
Soil Properties ◽  
Dry Matter ◽  
Arable Land ◽  
Rainfall Amount ◽  
Rainfall Variation ◽  
Global Issue ◽  
Term Change ◽  
The Impact

Ex-arable land-use change is a global issue with significant implications for climate change and impact for phytocenosis productivity and soil quality. In temperate humid grassland, we examined the impact of climate variability and changes of soil properties on 23 years of grass productivity after conversion of ex-arable soil to abandoned land (AL), unfertilized, and fertilized managed grassland (MGunfert and MGfert, respectively). This study aimed to investigate the changes between phytocenosis dry matter (DM) yield and rainfall amount in May–June and changes of organic carbon (Corg) stocks in soil. It was found that from 1995 to 2019, rainfall in May–June tended to decrease. The more resistant to rainfall variation were plants recovered in AL. The average DM yield of MGfert was 3.0 times higher compared to that in the AL. The DM yields of AL and MG were also influenced by the long-term change of soil properties. Our results showed that Corg sequestration in AL was faster (0.455 Mg ha−1 year−1) than that in MGfert (0.321 Mg ha−1 year−1). These studies will be important in Arenosol for selecting the method for transforming low-productivity arable land into MG.

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