Trends and variability of climate and river flow in the region of Costa das Baleias, Brazil

2013 ◽  
Vol 67 (1) ◽  
pp. 47-54 ◽  
Author(s):  
F. Genz ◽  
C. A. S. Tanajura
Keyword(s):  
River Discharge ◽  
Large Scale ◽  
River Flow ◽  
Local Development ◽  
Global Climate ◽  
Surface Air Temperature ◽  
Kendall Test ◽  
Positive Trend ◽  
Area Of Interest ◽  
Discharge Rates

There is an ongoing effort by the scientific community to regionalize climate studies to support local development plans. The area of interest is the Costa das Baleias on the east coast of northeast Brazil. It is located in a transition region of precipitation trends, and so assessing the local signal and magnitude is necessary. A series of annual anomalies of surface air temperature, precipitation and river discharge were analyzed from 1946 to 2010. The modified Mann–Kendall test was applied to detect trends. Temperature anomalies showed a consistent positive trend since 1950. Precipitation anomalies tended to decrease, though not significantly. River discharge rates showed a consistent positive trend. However, from the 1980s onwards, both the precipitation and the river discharge anomalies had the same decreasing tendency. The precipitation and discharge behavior are likely due to the combined effect of human interventions in the river basins including local, synoptic and global climate effects. The inter-annual variability was characterized by spectral analysis. Cycles were identified for the precipitation and the river discharge with periods of 2–3 years, 3–4 years, 7–8 years and 11–12 years. The decadal frequency is consistent with the South Atlantic and El Niño indices. This work strongly indicates that climate is changing in Costa das Baleias and further work is needed to investigate the mechanisms that link local to large-scale variability.

Summer Nonconvective Severe Wind Frequency over Ontario and Its Correlation with Tropical Pacific Sea Surface Temperature

2014 ◽  
Vol 53 (5) ◽  
pp. 1170-1182 ◽  
Author(s):  
Da-Lin Zhang ◽  
Zuohao Cao ◽  
Jianmin Ma ◽  
Aiming Wu
Keyword(s):  
Air Temperature ◽  
Large Scale ◽  
Regional Climate ◽  
Surface Wind ◽  
Surface Air Temperature ◽  
Kendall Test ◽  
Tropical Pacific ◽  
Sea Surface ◽  
Positive Trend ◽  
Climate Conditions

AbstractThe summer nonconvective severe surface wind (NCSSW) frequency over Ontario, Canada, in relation to regional climate conditions and tropical Pacific Ocean sea surface temperatures (SSTs) during the period of 1979–2006 is examined using surface wind reports and large-scale analysis data. A statistically robust positive trend in Ontario summer NCSSW frequency is identified using three independent statistical approaches, which include the conventional linear regression that has little disturbance to the original time series, the Mann–Kendall test without a lag-1 autoregressive process, and the Monte Carlo simulation. A composite analysis of the large-scale monthly mean data reveals that the high- (low-) NCSSW occurrence years are linked to stronger (weaker) large-scale horizontal pressure gradients and more (less) intensive vector wind anomalies in the upper troposphere. Unlike the low-event years, anomalous anticyclonic circulations are found at 500 and 250 hPa in the high-event years, which are conducive to downward momentum transport and favorable for severe surface wind development. It is also found that the summer NCSSW occurs more frequently under the conditions of warmer surface air temperature over Ontario. Further analyses indicate that an increase in the summer NCSSW frequency is well correlated with an increase in the previous winter SSTs over the eastern equatorial Pacific, namely, in the Niño-1+2 and Niño-3 areas, through a decrease in sea level pressure over northern Ontario and an increase in surface air temperature over central and southern Ontario.

Satellite soil moisture improves rainfall just where needed

2020 ◽  
Author(s):  
Luca Brocca ◽  
Stefania Camici ◽  
Christian Massari ◽  
Luca Ciabatta ◽  
Paolo Filippucci ◽  
...  
Keyword(s):  
Soil Moisture ◽  
River Discharge ◽  
Large Scale ◽  
River Flow ◽  
Global Scale ◽  
Rain Gauge ◽  
Rainfall Runoff ◽  
Global Precipitation Climatology Centre ◽  
Satellite Rainfall ◽  
Global Precipitation

<p>Soil moisture is a fundamental variable in the water and energy cycle and its knowledge in many applications is crucial. In the last decade, some authors have proposed the use of satellite soil moisture for estimating and improving rainfall, doing hydrology backward. From this research idea, several studies have been published and currently preoperational satellite rainfall products exploiting satellite soil moisture products have been made available.</p><p>The assessment of such products on a global scale has revealed an important result, i.e., the soil moisture based products perform better than state of the art products exactly over regions in which the data are needed: Africa and South America. However, over these areas the assessment against rain gauge observations is problematic and independent approaches are needed to assess the quality of such products and their potential benefit in hydrological applications. On this basis, the use of the satellite rainfall products as input into rainfall-runoff models, and their indirect assessment through river discharge observations is an alternative and valuable approach for evaluating their quality.</p><p>For this study, a newly developed large scale dataset of river discharge observations over 500+ basins throughout Africa has been exploited. Based on such unique dataset, a large scale assessment of multiple near real time satellite rainfall products has been performed: (1) the Early Run version of the Integrated Multi-Satellite Retrievals for GPM (Global Precipitation Measurement), IMERG Early Run, (2) SM2RAIN-ASCAT (https://doi.org/10.5281/zenodo.3405563), and (3) GPM+SM2RAIN (http://doi.org/10.5281/zenodo.3345323). Additionally, gauge-based and reanalysis rainfall products have been considered, i.e., (4) the Global Precipitation Climatology Centre (GPCC), and (5) the latest European Centre for Medium-Range Weather Forecasts reanalysis, ERA5. As rainfall-runoff model, the semi-distributed MISDc (Modello Idrologico Semi-Distribuito in continuo) model has been employed in the period 2007-2018 at daily temporal scale.</p><p>First results over a part of the dataset reveal the great value of satellite soil moisture products in improving satellite rainfall estimates for river flow prediction in Africa. Such results highlight the need to exploit such products for operational systems in Africa addressed to the mitigation of the flood risk and water resources management.</p>

scholarly journals Malawi’s Shire River Fluctuations and Climate

2014 ◽  
Vol 15 (5) ◽  
pp. 2039-2049 ◽  
Author(s):  
Mark R. Jury
Keyword(s):  
Large Scale ◽  
River Flow ◽  
Potential Evapotranspiration ◽  
Global Climate ◽  
Severity Index ◽  
Early Warning Systems ◽  
Climatic Research Unit ◽  
Climate Index ◽  
Drought Severity ◽  
High Pressure Cell

Abstract Hydrological fluctuations of Malawi’s Shire River and climatic drivers are studied for a range of time and space scales. The annual cycles of basin rainfall and river flow peak in summer and autumn, respectively. Satellite and model products at <50-km resolution resolve the water deficit in this narrow valley. The leading climate index fitting Shire River flow anomalies is the Climatic Research Unit (CRU) Palmer drought severity index, based on interpolated gauge rainfall minus Penman–Monteith potential evapotranspiration. Climate variables anticipate lake level changes by 2 months, while weather variables anticipate river flow surges by 2 days. Global climate patterns related to wet years include a Pacific La Niña cool phase and low pressure over northeastern Africa. Shire River floods coincide with a cyclonic looping wind pattern that amplifies the equatorial trough and draws monsoon flow from Tanzania. Hot spells are common in spring: daytime surface temperatures can reach 60°C causing rapid desiccation. An anticyclonic high pressure cell promotes evaporation losses of ~20 mm day−1 over brief periods. Flood and drought in Malawi are shown to be induced by the large-scale atmospheric circulation and rainfall in the surrounding highlands. Hence, early warning systems should consider satellite and radar coverage of the entire basin.

scholarly journals Evolving climate network perspectives on global surface air temperature effects of ENSO and strong volcanic eruptions

2021 ◽  
Author(s):  
Tim Kittel ◽  
Catrin Ciemer ◽  
Nastaran Lotfi ◽  
Thomas Peron ◽  
Francisco Rodrigues ◽  
...  
Keyword(s):  
Climate Variability ◽  
Large Scale ◽  
Southern Oscillation ◽  
Global Climate ◽  
Surface Air Temperature ◽  
Volcanic Eruptions ◽  
Internal Variability ◽  
Hierarchical Organization ◽  
Spatio Temporal ◽  
Global Surface

AbstractEpisodically occurring internal (climatic) and external (non-climatic) disruptions of normal climate variability are known to both affect spatio-temporal patterns of global surface air temperatures (SAT) at time-scales between multiple weeks and several years. The magnitude and spatial manifestation of the corresponding effects depend strongly on the specific type of perturbation and may range from weak spatially coherent yet regionally confined trends to a global reorganization of co-variability due to the excitation or inhibition of certain large-scale teleconnectivity patterns. Here, we employ functional climate network analysis to distinguish qualitatively the global climate responses to different phases of the El Niño–Southern Oscillation (ENSO) from those to the three largest volcanic eruptions since the mid-20th century as the two most prominent types of recurrent climate disruptions. Our results confirm that strong ENSO episodes can cause a temporary breakdown of the normal hierarchical organization of the global SAT field, which is characterized by the simultaneous emergence of consistent regional temperature trends and strong teleconnections. By contrast, the most recent strong volcanic eruptions exhibited primarily regional effects rather than triggering additional long-range teleconnections that would not have been present otherwise. By relying on several complementary network characteristics, our results contribute to a better understanding of climate network properties by differentiating between climate variability reorganization mechanisms associated with internal variability versus such triggered by non-climatic abrupt and localized perturbations.

scholarly journals Large-scale scour in response to tidal dominance in estuaries

2021 ◽  
Author(s):  
Jasper Leuven ◽  
Daan van Keulen ◽  
Jaap Nienhuis ◽  
Alberto Canestrelli ◽  
Ton Hoitink
Keyword(s):  
Sediment Transport ◽  
River Discharge ◽  
Large Scale ◽  
River Flow ◽  
Tidal Flow ◽  
Tidal Energy ◽  
Local Flow ◽  
Flow Acceleration ◽  
Flow Through ◽  
Tide Interaction

<p>Channel beds in estuaries and deltas often exhibit a local depth maximum at a location close to the coast. There are two known causes of large-scale (i.e. >10 river widths along-channel) channel bed scours: width constriction and draw down during river discharge extremes, both creating a local flow acceleration. Here, we systematically investigate a potential third mechanism. We study the effect of tidal dominance on the equilibrium channel bed in estuaries with a 1D-morphodynamic model. In estuaries, a morphodynamic equibrium is reached when the net (seaward) transport matches the upstream supply along the entire reach. The residual (river) current and river-tide interactions create seaward transport. Herein, river-tide interactions represent the seaward advection of tide-induced suspended sediment by the river flow. Tidal asymmetry typically creates landward transport. The main reason for scour formation is the amplification of tidal flow through funnelling of tidal energy. Only for a scouring profile the drop in river induced current magnitude reduces the river-tide interaction term, so that the net sediment transport matches the upstream sediment transport. When tidal influence is relatively large, and when channel convergence is strong, a equilibrium is only obtained with a scouring profile. We propose a predictor dependent on the width convergence, quantified as S<sub>B</sub>, and on the ratio between the specific peak tidal discharge at the mouth and the specific river discharge at the landward boundary (q<sub>tide</sub>/q<sub>river</sub>). Scours develop if (q<sub>tide</sub>/q<sub>river</sub>)/S<sub>B</sub> exceeds 0.3. These results are independent of scale and allow the prediction of scour in estuaries under future changes.</p>

scholarly journals Application of transform software for downscaling global climate model EdGCM results in north-eastern Bangladesh

2020 ◽  
Vol 26 (1) ◽  
Author(s):  
Fahmida Ishaque ◽  
Israt Jahan Ripa ◽  
Altaf Hossain ◽  
Abdur Rashid Sarker ◽  
Gazi Tamiz Uddin ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Surface Air Temperature ◽  
Trend Test ◽  
P Value ◽  
Positive Trend ◽  
Geostatistical Approach ◽  
Slope Estimator ◽  
Fine Resolution

Downscaling is a state-of-the-art technique to generate fine-resolution climate change prediction and an obvious tool for forecasting future climate scenarios for many data-scarce areas like Bangladesh. The Educational Global Climate Model (EdGCM) predicts numerically and its performance was not evaluated for Bangladesh earlier. Due to this reason, an attempt has been made to apply a new geostatistical approach with the help of transform software to downscale EdGCM for identifying the trend of surface air temperature at the Sylhet district. Both Doubled_CO<sup>2</sup> and Global_Warming_01 are simulated from EdGCM and maps are generated to depict global temperature variations. Downscaling is applied to the outputs from Doubled_CO<sup>2</sup> scenario. Percent of bias (PBIAS), Nash-Sutcliffe efficiency (NSE) and the ratio of root mean square error to the standard deviation of measured data (RSR) values are satisfactory and acceptable. The trend analysis was performed using the Mann-Kendall Trend test and Sen’s slope estimator. Temperature changes are significant for both downscaled and observed results of p-value which is less than alpha = 0.05. Mann-Kendall Z tests for annual downscaled and IPCC during (2006-2020) show a positive trend. Downscaled predicted annual average temperature (simulations by Doubled_CO<sup>2</sup>) for 2020 is 21.67˚C for the Sylhet district.

scholarly journals Changes in water discharges of the Baltic states rivers in the 20th century and its relation to climate change

2007 ◽  
Vol 38 (4-5) ◽  
pp. 401-412 ◽  
Author(s):  
A. Reihan ◽  
T. Koltsova ◽  
J. Kriauciuniene ◽  
L. Lizuma ◽  
D. Meilutyte-Barauskiene
Keyword(s):  
Climate Change ◽  
Air Temperature ◽  
River Discharge ◽  
Water Resource Management ◽  
Global Climate ◽  
Kendall Test ◽  
Low Flow ◽  
Baltic States ◽  
Temperature And Precipitation ◽  
The Baltic

The river discharge changes in three Baltic States and its relation to changes in the main climatic variables such as precipitation and air temperature were analyzed using observed data and methods of empirical statistical analysis. The study is important for the development of efficient water resource management systems and validation of climate change impact models. The application of the Mann-Kendall test reveals that a significant increasing trend in winter air temperature and precipitation was determined for all 3 investigated periods (1923–2003, 1941–2003 and 1961–2003). The same trend was found for the winter and annual discharge time series. No trend was observed for the spring, summer and autumn seasonal streamflow and summer low flow series for most of the Baltic region. In general the relation between the main meteorological and hydrological parameters and the tendency in river discharge trends is common for all of the Baltic States, and might be associated with the regional impacts of global climate change.

Modeling river discharge rates in California watersheds

2010 ◽  
Vol 1 (1) ◽  
pp. 36-54 ◽  
Author(s):  
Christopher Potter ◽  
John Shupe ◽  
Peggy Gross ◽  
Vanessa Genovese ◽  
Steven Klooster
Keyword(s):  
River Discharge ◽  
River Flow ◽  
Routing Algorithm ◽  
Ecosystem Model ◽  
North Coast ◽  
Flow Rates ◽  
Water Diversions ◽  
Discharge Rates ◽  
Model Predictions ◽  
Runoff Model

River discharge rates across all California's watershed have been modeled using the NASA version of the Carnegie-Ames-Stanford Approach (CASA) ecosystem model coupled with a surface hydrologic routing scheme previously called the Hydrological Routing Algorithm (HYDRA). To assess CASA-HYDRA's capability to estimate actual water flows in extreme and non-extreme precipitation years, we have organized hundreds of California river gauge records for comparison to monthly model predictions. Previously, CASA-HYDRA snowmelt algorithms were modified with equations from the USDA Snowmelt Runoff Model, which has been designed to predict daily stream flow in mountain basins where snowmelt is a major runoff factor. Based on model predictions of monthly flow rates across 336 stream gauges statewide, the multi-year model-to-measurement correlation between monthly river flow rates was R2=0.72. The model output was 15% higher across all these stream gauges than the measured monthly flow records for 1982–1990. It is plausible that the model would predict higher flow rates statewide than was measured at many gauge locations, due mainly to extensive water diversions for power generation and crop irrigation in the valley growing regions of the state. Predictions for gauges located on the state's North Coast and Sierra regions showed errors distributed fairly evenly throughout the seasons, whereas results for Central Coast and Southern regions showed higher errors mainly during the summer and fall. Future model applications for land cover and climate change in California are outlined.

scholarly journals Climate Control of Multidecadal Variability in River Discharge and Precipitation in Western Europe

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 257
Author(s):  
Isabel Jalón-Rojas ◽  
Bruno Castelle
Keyword(s):  
Interannual Variability ◽  
River Discharge ◽  
Large Scale ◽  
Western Europe ◽  
River Flow ◽  
Winter Precipitation ◽  
Climate Indices ◽  
Spring Discharge ◽  
Monthly Precipitation ◽  
Climate Control

The influence of large-scale climate variability on winter river discharge and precipitation across western Europe is investigated. We analyze 60 years of monthly precipitation and river flow data from 18 major western-European rivers and its relationship with dominant teleconnection patterns and climate indices in this region. Results show that winter river flow is characterized by large interannual variability, best correlates with (a) the North Atlantic Oscillation (NAO) at the far-northern (R up to 0.56) and southern latitudes (R up to −0.72), and (b) the West Europe Pressure Anomaly (WEPA) at the middle and northern latitudes, from 42° N to 55° N (R up to 0.83). These indices also explain the interannual variability in autumn and spring discharge in rivers characterized by secondary floods. Compared to the other leading modes of atmospheric variability, WEPA increases the correlations with winter precipitation up to 0.8 in many regions of western and central Europe. A positive WEPA corresponds to a southward shift and an intensification of the Icelandic-Low/Azores-High dipole, driving enhanced precipitation and river discharge in these regions. The correlations with precipitation are slightly higher than those with river discharge, particularly in France, with clear latitudinal gradient. This trend suggests that water storage variability and other catchment characteristics may also influence the interannual variability of river discharge. Seasonal forecasting of the WEPA and NAO winter indices can become a powerful tool in anticipating hydrological risks in this region.

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