scholarly journals Changes in surface hydrology, soil moisture and gross primary production in the Amazon during the 2015/2016 El Niño

2018 ◽  
Vol 373 (1760) ◽  
pp. 20180084 ◽  
Author(s):  
Erik van Schaik ◽  
Lars Killaars ◽  
Naomi E. Smith ◽  
Gerbrand Koren ◽  
L. P. H. van Beek ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Primary Production ◽  
El Niño ◽  
Amazon Basin ◽  
El Nino ◽  
Gross Primary Production ◽  
Surface Hydrology ◽  
The North ◽  
North Eastern ◽  
The Impact

The 2015/2016 El Niño event caused severe changes in precipitation across the tropics. This impacted surface hydrology, such as river run-off and soil moisture availability, thereby triggering reductions in gross primary production (GPP). Many biosphere models lack the detailed hydrological component required to accurately quantify anomalies in surface hydrology and GPP during droughts in tropical regions. Here, we take the novel approach of coupling the biosphere model SiBCASA with the advanced hydrological model PCR-GLOBWB to attempt such a quantification across the Amazon basin during the drought in 2015/2016. We calculate 30–40% reduced river discharge in the Amazon starting in October 2015, lagging behind the precipitation anomaly by approximately one month and in good agreement with river gauge observations. Soil moisture shows distinctly asymmetrical spatial anomalies with large reductions across the north-eastern part of the basin, which persisted into the following dry season. This added to drought stress in vegetation, already present owing to vapour pressure deficits at the leaf, resulting in a loss of GPP of 0.95 (0.69 to 1.20) PgC between October 2015 and March 2016 compared with the 2007–2014 average. Only 11% (10–12%) of the reduction in GPP was found in the (wetter) north-western part of the basin, whereas the north-eastern and southern regions were affected more strongly, with 56% (54–56%) and 33% (31–33%) of the total, respectively. Uncertainty on this anomaly mostly reflects the unknown rooting depths of vegetation. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

Towards onset: shades of ENSO skill

2020 ◽  
Author(s):  
Dougal Squire ◽  
James Risbey
Keyword(s):  
El Niño ◽  
Statistical Models ◽  
El Nino ◽  
Southern Oscillation ◽  
Skill Score ◽  
Forecast Skill ◽  
The North ◽  
Forecast Models ◽  
The Impact ◽  
Better Than

<p>Climate forecast skill for the El Nino-Southern Oscillation (ENSO) is better than chance, but has increased little in recent decades. Further, the relative skill of dynamical and statistical models varies in skill assessments, depending on choices made about how to evaluate the forecasts. Using a suite of models from the North American Multi-Model Ensemble (NMME) archive we outline the consequences for skill of how the bias corrections and forecast anomalies are formed. We show that the method for computing forecast anomalies is such a critical part of the provenance of a skill score that any score for forecast anomalies lacking clarity about the method is open to wide interpretation. Many assessments of hindcast skill are likely to be overestimates of attainable forecast skill because the hindcast anomalies are informed by observations over the period assessed that would not be available to a real forecast. The relative skill rankings of forecast models can change between hindcast and forecast systems because the impact of model bias on skill is sensitive to the ways in which forecast anomalies are formed. Dynamical models are found to be more skillful than simple statistical models for forecasting the onset of El Nino events.</p>

scholarly journals Widespread reduction in sun-induced fluorescence from the Amazon during the 2015/2016 El Niño

2018 ◽  
Vol 373 (1760) ◽  
pp. 20170408 ◽  
Author(s):  
Gerbrand Koren ◽  
Erik van Schaik ◽  
Alessandro C. Araújo ◽  
K. Folkert Boersma ◽  
Antje Gärtner ◽  
...  
Keyword(s):  
Primary Productivity ◽  
El Niño ◽  
Carbon Balance ◽  
Amazon Basin ◽  
El Nino ◽  
Atmospheric Conditions ◽  
Signal To Noise ◽  
The Tropics ◽  
The Impact ◽  
Low Precipitation

The tropical carbon balance dominates year-to-year variations in the CO 2 exchange with the atmosphere through photosynthesis, respiration and fires. Because of its high correlation with gross primary productivity (GPP), observations of sun-induced fluorescence (SIF) are of great interest. We developed a new remotely sensed SIF product with improved signal-to-noise in the tropics, and use it here to quantify the impact of the 2015/2016 El Niño Amazon drought. We find that SIF was strongly suppressed over areas with anomalously high temperatures and decreased levels of water in the soil. SIF went below its climatological range starting from the end of the 2015 dry season (October) and returned to normal levels by February 2016 when atmospheric conditions returned to normal, but well before the end of anomalously low precipitation that persisted through June 2016. Impacts were not uniform across the Amazon basin, with the eastern part experiencing much larger (10–15%) SIF reductions than the western part of the basin (2–5%). We estimate the integrated loss of GPP relative to eight previous years to be 0.34–0.48 PgC in the three-month period October–November–December 2015. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

scholarly journals Are there statistical links between the direction of European weather systems and ENSO, the solar cycle or stratospheric aerosols?

2016 ◽  
Vol 3 (2) ◽  
pp. 150320 ◽  
Author(s):  
Benjamin A. Laken ◽  
Frode Stordal
Keyword(s):  
Solar Cycle ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Stratospheric Aerosol ◽  
Atmospheric Flow ◽  
Superposed Epoch Analysis ◽  
The North ◽  
The North Atlantic Oscillation ◽  
The Impact

The Hess Brezowsky Großwetterlagen (HBGWL) European weather classification system, accumulated over a long period (more than 130 years), provides a rare opportunity to examine the impact of various factors on regional atmospheric flow. We have used these data to examine changes in the frequency (days/month) of given weather systems direction (WSD) during peak phases in the North Atlantic Oscillation (NAO), El Niño Southern Oscillation (ENSO), solar cycle (SC) and peaks in stratospheric aerosol optical depth (AOD) with superposed epoch analysis and Monte Carlo significance testing. We found highly significant responses to the NAO consistent with expectations: this signal confirmed the utility of the HBGWL data for this type of analysis and provided a benchmark of a clear response. WSD changes associated with ENSO, SC and AOD were generally within the ranges expected from random samples. When seasonal restrictions were added the results were similar, however, we found one clearly significant result: an increase in southerly flow of 2.6±0.8 days/month ( p =1.9×10 −4 ) during boreal summertime in association with El Niño. This result supports the existence of a robust teleconnection between the ENSO and European weather.

scholarly journals The impact of El Niño-Southern Oscillation on the Canadian climate

2006 ◽  
Vol 6 ◽  
pp. 149-153 ◽  
Author(s):  
A. Shabbar
Keyword(s):  
North American ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Cold Season ◽  
Tropical Pacific ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
The North ◽  
The Impact

Abstract. The quasi-periodic El Niño -Southern Oscillation (ENSO) phenomenon in the tropical Pacific Ocean produces the largest interannual variation in the cold season climate of Canada. The diabatic heating in the eastern tropical Pacific, associated with the warm phase of ENSO (El Niño), triggers Rossby waves which in turn gives rise to the Pacific-North American teleconnection (PNA) over the North American sector. The strongest cell of the PNA pattern lies over western Canada. In most of southern Canada, mean winter temperature distribution is shifted towards warmer values, and precipitation is below normal. The presence of El Niño provides the best opportunity to make skillful long-range winter forecast for Canada. A strong El Niño event, while bringing respite from the otherwise cold winter in Canada, can be expected to cost the Canadian economy two to five billion dollars.

scholarly journals The pan-tropical response of soil moisture to El Niño

2019 ◽  
Author(s):  
Kurt C. Solander ◽  
Brent D. Newman ◽  
Alessandro Carioca de Aruajo ◽  
Holly R. Barnard ◽  
Z. Carter Berry ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Southeast Asia ◽  
El Niño ◽  
Amazon Basin ◽  
Multiple Scales ◽  
El Nino ◽  
Climate Anomalies ◽  
Mature Phase ◽  
El Niño Event ◽  
Sst Anomalies

Abstract. The 2015–16 El Niño event ranks as one of the most severe on record in terms of the magnitude and extent of sea surface temperature (SST) anomalies generated in the tropical Pacific Ocean. Corresponding global impacts on the climate were expected to rival, or even surpass, those of the 1997–98 severe El Niño event, which had SST anomalies that were similar in size. However, the 2015–16 event failed to meet expectations for hydrologic change in many areas, including those expected to receive well above normal precipitation. To better understand how climate anomalies during an El Niño event impact soil moisture, we investigate changes in soil moisture in the humid tropics (between ±25°) during the three most recent super El Niño events of 1982–83, 1997–98, and 2015–16, using data from the Global Land Data Assimilation System (GLDAS). First, we validate the soil moisture estimates from GLDAS through comparison with in-situ observations obtained from 16 sites across five continents, showing an r2 of 0.54. Next, we apply a k-means cluster analysis to the soil moisture estimates during the El Niño mature phase, resulting in four groups of clustered data. The strongest and most consistent decreases in soil moisture occur in the Amazon basin and maritime southeast Asia, while the most consistent increases occur over east Africa. In addition, we compare changes in soil moisture to both precipitation and evapotranspiration, which showed a lack of agreement in the direction of change between these variables and soil moisture most prominently in the southern Amazon basin, Sahel and mainland southeast Asia. Our results can be used to improve estimates of spatiotemporal differences in El Niño impacts on soil moisture in tropical hydrology and ecosystem models at multiple scales.

scholarly journals Tree growth and stem carbon accumulation in human-modified Amazonian forests following drought and fire

2018 ◽  
Vol 373 (1760) ◽  
pp. 20170308 ◽  
Author(s):  
Erika Berenguer ◽  
Yadvinder Malhi ◽  
Paulo Brando ◽  
Amanda Cardoso Nunes Cordeiro ◽  
Joice Ferreira ◽  
...  
Keyword(s):  
Wood Density ◽  
Tree Growth ◽  
El Niño ◽  
Human Disturbance ◽  
Amazon Basin ◽  
El Nino ◽  
Carbon Accumulation ◽  
Extreme Drought ◽  
The Difference ◽  
The Impact

Human-modified forests are an ever-increasing feature across the Amazon Basin, but little is known about how stem growth is influenced by extreme climatic events and the resulting wildfires. Here we assess for the first time the impacts of human-driven disturbance in combination with El Niño–mediated droughts and fires on tree growth and carbon accumulation. We found that after 2.5 years of continuous measurements, there was no difference in stem carbon accumulation between undisturbed and human-modified forests. Furthermore, the extreme drought caused by the El Niño did not affect carbon accumulation rates in surviving trees. In recently burned forests, trees grew significantly more than in unburned ones, regardless of their history of previous human disturbance. Wood density was the only significant factor that helped explain the difference in growth between trees in burned and unburned forests, with low wood–density trees growing significantly more in burned sites. Our results suggest stem carbon accumulation is resistant to human disturbance and one-off extreme drought events, and it is stimulated immediately after wildfires. However, these results should be seen with caution—without accounting for carbon losses, recruitment and longer-term changes in species composition, we cannot fully understand the impacts of drought and fire in the carbon balance of human-modified forests. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Nino on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

Hawaiian Regional Climate Variability during Two Types of El Niño

2020 ◽  
Vol 33 (22) ◽  
pp. 9929-9943
Author(s):  
Bo-Yi Lu ◽  
Pao-Shin Chu ◽  
Sung-Hun Kim ◽  
Christina Karamperidou
Keyword(s):  
El Niño ◽  
North Pacific ◽  
El Nino ◽  
Moisture Flux ◽  
Jet Stream ◽  
Flux Divergence ◽  
The North ◽  
The Impact ◽  
The North Pacific ◽  
Moisture Flux Divergence

AbstractThe large-scale atmospheric circulation of the North Pacific associated with two types of El Niño—the eastern Pacific (EP) and central Pacific (CP)—is studied in relation to Hawaiian winter (December–February) rainfall and temperature. The eastern and central equatorial Pacific undergo active convective heating during EP El Niño winters. The local Hadley circulation is enhanced and an upper-level westerly jet stream of the North Pacific is elongated eastward. Due to the impact of both phenomena, stronger anomalous descending motion, moisture flux divergence anomalies near Hawaii, and reduction of easterly trade winds, which are characteristic of EP winters, are unfavorable for winter rainfall in Hawaii. As a result of this robust signal, dry conditions prevail in Hawaii and the standard deviation of rainfall during EP winters is smaller than the climatology. For CP winters, the maximum equatorial ocean warming is weaker and shifted westward to near the date line. The subtropical jet stream retreats westward relative to EP winters and the anomalously sinking motion near Hawaii is variable and generally weaker. Although the anomalous moisture flux divergence still exists over the subtropical North Pacific, its magnitude is weaker relative to EP winters. Without strong external forcing, rainfall in the Hawaiian Islands during CP winters is close to the long-term mean. The spread of rainfall from one CP event to another is also larger. The near-surface minimum temperature from three stations in Hawaii reveals cooling during EP winters and slight warming during CP winters.

scholarly journals Response of Tropical Terrestrial Gross Primary Production to the Super El Niño Event in 2015

2018 ◽  
Vol 123 (10) ◽  
pp. 3193-3203 ◽  
Author(s):  
Jiawen Zhu ◽  
Minghua Zhang ◽  
Yao Zhang ◽  
Xiaodong Zeng ◽  
Xiangming Xiao
Keyword(s):  
Primary Production ◽  
El Niño ◽  
El Nino ◽  
Gross Primary Production ◽  
El Niño Event ◽  
Super El Niño

scholarly journals The pantropical response of soil moisture to El Niño

2020 ◽  
Vol 24 (5) ◽  
pp. 2303-2322
Author(s):  
Kurt C. Solander ◽  
Brent D. Newman ◽  
Alessandro Carioca de Araujo ◽  
Holly R. Barnard ◽  
Z. Carter Berry ◽  
...  
Keyword(s):  
Soil Moisture ◽  
El Niño ◽  
Amazon Basin ◽  
Multiple Scales ◽  
El Nino ◽  
Eastern Africa ◽  
Climate Anomalies ◽  
Mature Phase ◽  
El Niño Event ◽  
Sst Anomalies

Abstract. The 2015–2016 El Niño event ranks as one of the most severe on record in terms of the magnitude and extent of sea surface temperature (SST) anomalies generated in the tropical Pacific Ocean. Corresponding global impacts on the climate were expected to rival, or even surpass, those of the 1997–1998 severe El Niño event, which had SST anomalies that were similar in size. However, the 2015–2016 event failed to meet expectations for hydrologic change in many areas, including those expected to receive well above normal precipitation. To better understand how climate anomalies during an El Niño event impact soil moisture, we investigate changes in soil moisture in the humid tropics (between ±25∘) during the three most recent super El Niño events of 1982–1983, 1997–1998 and 2015–2016, using data from the Global Land Data Assimilation System (GLDAS). First, we use in situ soil moisture observations obtained from 16 sites across five continents to validate and bias-correct estimates from GLDAS (r2=0.54). Next, we apply a k-means cluster analysis to the soil moisture estimates during the El Niño mature phase, resulting in four groups of clustered data. The strongest and most consistent decreases in soil moisture occur in the Amazon basin and maritime southeastern Asia, while the most consistent increases occur over eastern Africa. In addition, we compare changes in soil moisture to both precipitation and evapotranspiration, which showed a lack of agreement in the direction of change between these variables and soil moisture most prominently in the southern Amazon basin, the Sahel and mainland southeastern Asia. Our results can be used to improve estimates of spatiotemporal differences in El Niño impacts on soil moisture in tropical hydrology and ecosystem models at multiple scales.

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