scholarly journals ENSO and IOD teleconnections for African ecosystems: evidence of destructive interference between climate oscillations

2011 ◽  
Vol 8 (1) ◽  
pp. 27-40 ◽  
Author(s):  
C. A. Williams ◽  
N. P. Hanan
Keyword(s):  
El Niño ◽  
Land Surface ◽  
Vegetation Change ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Interactive Effects ◽  
Surface Model ◽  
Destructive Interference ◽  
Climate Oscillations

Abstract. Rainfall and vegetation across Africa are known to resonate with the coupled ocean-atmosphere phenomena of El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). However, the regional-scale implications of sea surface temperature variability for Africa's photosyntheis have received little focused attention, particularly in the case of IOD. Furthermore, studies exploring the interactive effects of ENSO and IOD when coincident are lacking. This analysis uses remotely sensed vegetation change plus a land surface model driven with observed meteorology to investigate how rainfall, vegetation, and photosynthesis across Africa respond to these climate oscillations. In addition to the relatively well-known ENSO forcing, the IOD induces large departures of photosynthesis across much of Africa associated with anomalies in rainfall and vegetation greenness. More importantly, sizeable independent effects can be suppressed or even reversed by destructive interferences during periods of simultaneous ENSO and IOD activity. For example, effects of positive IOD on southeastern Africa tended to dominate those of El Niño during their coincidence spanning 1997–1998, with sign reversal of El Niño's typically strong suppression of photosynthesis in this region. These findings call into question past analyses examining teleconnections to ENSO or IOD in isolation, and indicate the need to consider their simultaneous states when examining influences on hydroclimatic and ecological conditions across Africa.

scholarly journals ENSO and IOD teleconnections for African ecosystems: evidence of destructive interference between climate oscillations

2010 ◽  
Vol 7 (4) ◽  
pp. 6323-6352
Author(s):  
C. A. Williams ◽  
N. P. Hanan
Keyword(s):  
El Niño ◽  
Land Surface ◽  
Vegetation Change ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Interactive Effects ◽  
Surface Model ◽  
Destructive Interference ◽  
Climate Oscillations

Abstract. Rainfall and vegetation across Africa are known to resonate with the coupled ocean-atmosphere phenomena of El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). However, the regional-scale implications of sea surface temperature variability for Africa's carbon sources and sinks have received little focused attention, particularly in the case of IOD. Furthermore, studies exploring the interactive effects of ENSO and IOD when coincident are lacking. This analysis uses remotely sensed vegetation change plus a land surface model driven with observed meteorology to investigate how rainfall, vegetation, and photosynthesis across Africa respond to these climate oscillations. In addition to the relatively well-known ENSO forcing, the IOD induces large departures of photosynthesis across much of Africa associated with anomalies in rainfall and vegetation greenness. More importantly, sizeable independent effects can be suppressed or even reversed by destructive interferences during periods of simultaneous ENSO and IOD activity. For example, effects of positive IOD on southeastern Africa tended to dominate those of El Niño during their coincidence spanning 1997–1998, with sign reversal of El Niño's typically strong suppression of photosynthesis in this region. These findings call into question past analyses examining teleconnections to ENSO or IOD in isolation, and indicate the need to consider their simultaneous states when examining influences on hydroclimatic and ecological conditions across Africa.

El Niño–Southern Oscillation influences annual survival of a migratory songbird at a regional scale

The Auk ◽  
2012 ◽  
Vol 129 (4) ◽  
pp. 734-743 ◽  
Author(s):  
Joseph A. LaManna ◽  
T. Luke George ◽  
James F. Saracco ◽  
M. Philip Nott ◽  
David F. DeSante
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Scale ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Annual Survival ◽  
Migratory Songbird

scholarly journals Aerosol meteorology of the Maritime Continent for the 2012 7SEAS southwest monsoon intensive study – Part 1: regional-scale phenomena

2016 ◽  
Vol 16 (22) ◽  
pp. 14041-14056 ◽  
Author(s):  
Jeffrey S. Reid ◽  
Peng Xian ◽  
Brent N. Holben ◽  
Edward J. Hyer ◽  
Elizabeth A. Reid ◽  
...  
Keyword(s):  
Biomass Burning ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Intraseasonal Oscillation ◽  
Southwest Monsoon ◽  
Boreal Summer ◽  
Maritime Continent ◽  
Fire Activity

Abstract. The largest 7 Southeast Asian Studies (7SEAS) operation period within the Maritime Continent (MC) occurred in the August–September 2012 biomass burning season. Included was an enhanced deployment of Aerosol Robotic Network (AERONET) sun photometers, multiple lidars, and field measurements to observe transported smoke and pollution as it left the MC and entered the southwest monsoon trough. Here we describe the nature of the overall 2012 southwest monsoon (SWM) and biomass burning season to give context to the 2012 deployment. The MC in 2012 was in a slightly warm El Niño/Southern Oscillation (ENSO) phase and with spatially typical burning activity. However, overall fire counts for 2012 were 10 % lower than the Reid et al. (2012) baseline, with regions of significant departures from this norm, ranging from southern Sumatra (+30 %) to southern Kalimantan (−42 %). Fire activity and monsoonal flows for the dominant burning regions were modulated by a series of intraseasonal oscillation events (e.g., Madden–Julian Oscillation, or MJO, and boreal summer intraseasonal oscillation, or BSISO). As is typical, fire activity systematically progressed eastward over time, starting with central Sumatran fire activity in June related to a moderately strong MJO event which brought drier air from the Indian Ocean aloft and enhanced monsoonal flow. Further burning in Sumatra and Kalimantan Borneo occurred in a series of significant events from early August to a peak in the first week of October, ending when the monsoon started to migrate back to its wintertime northeastern flow conditions in mid-October. Significant monsoonal enhancements and flow reversals collinear with tropical cyclone (TC) activity and easterly waves were also observed. Islands of the eastern MC, including Sulawesi, Java, and Timor, showed less sensitivity to monsoonal variation, with slowly increasing fire activity that also peaked in early October but lingered into November. Interestingly, even though fire counts were middling, resultant AERONET 500 nm aerosol optical thickness (AOT) from fire activity was high, with maximums of 3.6 and 5.6 in the Sumatra and Kalimantan source regions at the end of the burning season and an average of ∼ 1. AOTs could also be high at receptor sites, with a mean and maximum of 0.57 and 1.24 in Singapore and 0.61 and 0.8 in Kuching Sarawak. Ultimately, outside of the extreme 2015 El Niño event, average AERONET AOT values were higher than any other time since sites were established. Thus, while satellite fire data, models, and AERONET all qualitatively agree on the nature of smoke production and transport, the MC's complex environment resulted in clear differences in quantitative interpretation of these datasets.

scholarly journals Regional and Local Impacts of the ENSO and IOD Events of 2015 and 2016 on the Indian Summer Monsoon—A Bhutan Case Study

Atmosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 954
Author(s):  
Katherine Power ◽  
Josefine Axelsson ◽  
Norbu Wangdi ◽  
Qiong Zhang
Keyword(s):  
Indian Ocean ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
El Niño ◽  
Late Onset ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Local Scale ◽  
The Indian Ocean

The Indian Summer Monsoon (ISM) plays a vital role in the livelihoods and economy of those living on the Indian subcontinent, including the small, mountainous country of Bhutan. The ISM fluctuates over varying temporal scales and its variability is related to many internal and external factors including the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). In 2015, a Super El Niño occurred in the tropical Pacific alongside a positive IOD in the Indian Ocean and was followed in 2016 by a simultaneous La Niña and negative IOD. These events had worldwide repercussions. However, it is unclear how the ISM was affected during this time, both at a regional scale over the whole ISM area and at a local scale over Bhutan. First, an evaluation of data products comparing ERA5 reanalysis, TRMM and GPM satellite, and GPCC precipitation products against weather station measurements from Bhutan, indicated that ERA5 reanalysis was suitable to investigate ISM change in these two years. The reanalysis datasets showed that there was disruption to the ISM during this period, with a late onset of the monsoon in 2015, a shifted monsoon flow in July 2015 and in August 2016, and a late withdrawal in 2016. However, this resulted in neither a monsoon surplus nor a deficit across both years but instead large spatial-temporal variability. It is possible to attribute some of the regional scale changes to the ENSO and IOD events, but the expected impact of a simultaneous ENSO and IOD events are not recognizable. It is likely that 2015/16 monsoon disruption was driven by a combination of factors alongside ENSO and the IOD, including varying boundary conditions, the Pacific Decadal Oscillation, the Atlantic Multi-decadal Oscillation, and more. At a local scale, the intricate topography and orographic processes ongoing within Bhutan further amplified or dampened the already altered ISM.

scholarly journals Land surface anomaly simulations and predictions with a climate model: an El Niño Southern Oscillation case study

2008 ◽  
Vol 367 (1890) ◽  
pp. 917-923 ◽  
Author(s):  
Debbie Putt ◽  
Keith Haines ◽  
Robert Gurney ◽  
Chunlei Liu
Keyword(s):  
Soil Moisture ◽  
El Niño ◽  
Land Surface ◽  
Climate Models ◽  
Snow Water Equivalent ◽  
Climate Model ◽  
El Nino ◽  
Southern Oscillation ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation

The ability of climate models to reproduce and predict land surface anomalies is an important but little-studied topic. In this study, an atmosphere and ocean assimilation scheme is used to determine whether HadCM3 can reproduce and predict snow water equivalent and soil moisture during the 1997–1998 El Niño Southern Oscillation event. Soil moisture is reproduced more successfully, though both snow and soil moisture show some predictability at 1- and 4-month lead times. This result suggests that land surface anomalies may be reasonably well initialized for climate model predictions and hydrological applications using atmospheric assimilation methods over a period of time.

scholarly journals Annual flood sensitivities to El Niño Southern Oscillation at the global scale

2013 ◽  
Vol 10 (8) ◽  
pp. 10231-10276
Author(s):  
P. J. Ward ◽  
S. Eisner ◽  
M. Flörke ◽  
M. D. Dettinger ◽  
M. Kummu
Keyword(s):  
El Niño ◽  
Land Surface ◽  
El Nino ◽  
Southern Oscillation ◽  
Global Scale ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Economic Damage ◽  
Flood Impacts ◽  
River Floods

Abstract. Floods are amongst the most dangerous natural hazards in terms of economic damage. Whilst a growing number of studies have examined how river floods are influenced by climate change, the role of natural modes of interannual climate variability remains poorly understood. Here, we present the first global assessment of the influence of El Niño Southern Oscillation (ENSO) on river floods. The analysis was carried out by simulating daily gridded discharges using the WaterGAP model, and examining statistical relationships between these discharges and ENSO indices. We found that, over the period 1958–1999, ENSO exerted a significant influence on annual floods in river basins covering over a third of the world's land surface, and that its influence on floods has been much greater than its influence on average flows. We show that there are more areas in which annual floods intensify with La Niña and decline with El Niño than vice versa. However, we also found that in many regions the strength of the relationships between ENSO and annual floods have been non-stationary, with either strengthening or weakening trends during the study period. We discuss the implications of these findings for science and management. Given the strong relationships between ENSO and annual floods, we suggest that more research is needed to assess relationships between ENSO and flood impacts (e.g. loss of lives or economic damage). Moreover, we suggest that in those regions where useful relationships exist, this information could be combined with ongoing advances in ENSO prediction research, in order to provide year-to-year probabilistic flood risk forecasts.

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