Tropical forest dynamics across a rainfall gradient and the impact of an El Niño dry season

2004 ◽  
Vol 20 (01) ◽  
pp. 51-72 ◽  
Author(s):  
Richard Condit ◽  
Salomon Aguilar ◽  
Andres Hernandez ◽  
Rolando Perez ◽  
Suzanne Lao ◽  
...  
2009 ◽  
Vol 48 (8) ◽  
pp. 1718-1724 ◽  
Author(s):  
Martha G. Roberts ◽  
David Dawe ◽  
Walter P. Falcon ◽  
Rosamond L. Naylor

Abstract This study uses regression analysis to evaluate the relationships among sea surface temperature anomalies (SSTA) averaged over the Niño-3.4 region (5°N–5°S, 120°–170°W), rainfall, and rice production, area harvested, and yield in Luzon, the large island on which most Philippine rice is grown. Previous research on Philippine rice production and El Niño–Southern Oscillation (ENSO) has found negative associations between El Niño events and rice yields in rainfed systems. This analysis goes further and shows that both irrigated and rainfed ecosystems are impacted. It also compares impacts on area harvested and yield. Variations in average July–September Niño-3.4 SSTAs explain approximately 29% of the interannual variations in the deviations of total January–June (dry season) rice production from a polynomial trend for 1970–2005. In contrast, no impact was found on July–December production in either year t or t + 1. The impact of ENSO on dry-season rice production in Luzon appears to be primarily due to changes in area harvested rather than yield. Production declines for rainfed ecosystems are relatively larger than for irrigated ecosystems: a 1°C increase in average July–September Niño-3.4 SSTA is associated with a 3.7% decrease in irrigated dry-season production but with a 13.7% decline in rainfed dry-season production.


2000 ◽  
Vol 16 (3) ◽  
pp. 355-367 ◽  
Author(s):  
Michiko Nakagawa ◽  
Kenta Tanaka ◽  
Tohru Nakashizuka ◽  
Tatsuhiro Ohkubo ◽  
Tsuyoshi Kato ◽  
...  

The impact of the unusually severe drought associated with the 1997–1998 El Niño on tropical forest dynamics in Sarawak, Malaysia was examined. Mortality during the non-drought period (1993–1997) in a core plot (1.38 ha) was 0.89 % y−1, while that during the drought period (1997–1998) in the same plot and a peripheral plot was 6.37 and 4.35 % y−1, respectively. The basal area lost in the drought interval was 3.4 times that of the annual incremental basal area in 1993–1997. Drought mortality was higher for the smaller trees, though it was less size dependent than the non-drought mortality. Dipterocarpaceae, which is the dominant family in the study plot, had a mortality 12–30 times higher in the drought than the non-drought period. There were no significant differences in mortality among the topographic types. From the results of a log-linear model (multi-factored contingency table), the death of trees was correlated with size class, indicating a change in the size-class structure of the forest. Thus, both the species composition and structure are totally affected by such an episodic drought even in a per-humid tropical forest.


2016 ◽  
Vol 42 ◽  
pp. 23-33 ◽  
Author(s):  
María Carolina Pinilla Herrera ◽  
Carlos Andrés Pinzón Correa

Abstract. The influence of El Niño and La Niña on monthly and seasonal rainfall over mountain landscapes in Colombia and México was assessed based on the Oceanic Niño Index (ONI). A statistical analysis was develop to compare the extreme dry/precipitation events between El Niño, La Niña and Neutral episodes. For both areas, it was observed that El Niño and La Niña episodes are associated with important increases or decreases in rainfall. However, Neutral episodes showed the highest occurrence of extreme precipitation/dry events. For a better understanding of the impact of El Niño and La Niña on seasonal precipitation, we did a compound and a GIS analyses to define the high/low probability of above, below or normal seasonal precipitation under El Niño, La Niña and cold/warm Neutral episodes. In San Vicente, Colombia the below-normal seasonal rainfall was identified during El Niño and Neutral episodes in the dry season JJA. In this same municipality we also found above-normal seasonal rainfall during La Niña and Neutral episodes, especially in the dry season DJF. In Tancítaro México the below-normal seasonal rainfall was identified during La Niña winters (DJF) and El Niño summers (JJA), the above-normal seasonal rainfall was found during La Niña summers (JJA) and El Niño winters (DJF).


2018 ◽  
Vol 373 (1760) ◽  
pp. 20170406 ◽  
Author(s):  
C. Burton ◽  
S. Rifai ◽  
Y. Malhi

To understand the impacts of extreme climate events, it is first necessary to understand the spatio-temporal characteristics of the event. Gridded climate products are frequently used to describe climate patterns but have been shown to perform poorly over data-sparse regions such as tropical forests. Often, they are uncritically employed in a wide range of studies linking tropical forest processes to large-scale climate variability. Here, we conduct an inter-comparison and assessment of near-surface air temperature fields supplied by four state-of-the-art reanalysis products, along with precipitation estimates supplied by four merged satellite-gauge rainfall products. Firstly, spatio-temporal patterns of temperature and precipitation anomalies during the 2015–2016 El Niño are shown for each product to characterize the impact of the El Niño on the tropical forest biomes of Equatorial Africa, Southeast Asia and South America. Using meteorological station data, a two-stage assessment is then conducted to determine which products most reliably model tropical climates during the 2015–2016 El Niño, and which perform best over the longer-term satellite observation period (1980–2016). Results suggest that eastern Amazonia, parts of the Congo Basin and mainland Southeast Asia all experienced significant monthly mean temperature anomalies during the El Niño, while northeastern Amazonia, eastern Borneo and southern New Guinea experienced significant precipitation deficits. Our results suggest ERA-Interim and MERRA2 are the most reliable air temperature datasets, while TRMM 3B42 V7 and CHIRPS v2.0 are the best-performing rainfall datasets. 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’.


Agromet ◽  
2018 ◽  
Vol 28 (1) ◽  
pp. 1
Author(s):  
Rahmat Hidayat ◽  
Kentaro Ando

Rainfall variability over Indonesia and its relation to El Niño – Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) events were investigated using the Japanese 25-year reanalysis/Japan Meteorological Agency (JMA) Climate Data Assimilation System (JRA-25/ JCDAS). The JRA-25 data consistently depicts seasonal variation of Indonesian rainfall with a wet season that peaks at December-January and a dry season that peaks in July-August when the convection belt moved northward. Composite analysis of rainfall, sea surface temperature and low-level wind anomalies have shown that the impact of ENSO/IOD on rainfall variations in Indonesia is clearly dominant during dry season. Drought conditions typically occur during El Niño years when SST anomalies surrounding Indonesia are cool and walker circulation is weakened, resulting in anomalous surface easterlies across Indonesia. In contrast, in the wet season, the weakening of the relationship between ENSO and Indonesian rainfall is linked to the transition between surface southeasterlies to northwesterlies. At this time persistent surface easterly anomalies across Indonesia superimposed on the climatological mean winds during a warm phase of ENSO event acts to reduce the wind speed resulting reduced the negative DJF rainfall anomalies.


2018 ◽  
Vol 373 (1760) ◽  
pp. 20170311 ◽  
Author(s):  
Patrick Meir ◽  
Maurizio Mencuccini ◽  
Oliver Binks ◽  
Antonio Lola da Costa ◽  
Leandro Ferreira ◽  
...  

Are short-term responses by tropical rainforest to drought (e.g. during El Niño) sufficient to predict changes over the long-term, or from repeated drought? Using the world's only long-term (16-year) drought experiment in tropical forest we examine predictability from short-term measurements (1–2 years). Transpiration was maximized in droughted forest: it consumed all available throughfall throughout the 16 years of study. Leaf photosynthetic capacity was maintained, but only when averaged across tree size groups. Annual transpiration in droughted forest was less than in control, with initial reductions (at high biomass) imposed by foliar stomatal control. Tree mortality increased after year three, leading to an overall biomass loss of 40%; over the long-term, the main constraint on transpiration was thus imposed by the associated reduction in sapwood area. Altered tree mortality risk may prove predictable from soil and plant hydraulics, but additional monitoring is needed to test whether future biomass will stabilize or collapse. Allocation of assimilate differed over time: stem growth and reproductive output declined in the short-term, but following mortality-related changes in resource availability, both showed long-term resilience, with partial or full recovery. Understanding and simulation of these phenomena and related trade-offs in allocation will advance more effectively through greater use of optimization and probabilistic modelling approaches. 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’.


2010 ◽  
Vol 67 (9) ◽  
pp. 2854-2870 ◽  
Author(s):  
Tingting Gong ◽  
Steven B. Feldstein ◽  
Dehai Luo

Abstract This study examines the relationship between intraseasonal southern annular mode (SAM) events and the El Niño–Southern Oscillation (ENSO) using daily 40-yr ECMWF Re-Analysis (ERA-40) data. The data coverage spans the years 1979–2002, for the austral spring and summer seasons. The focus of this study is on the question of why positive SAM events dominate during La Niña and negative SAM events during El Niño. A composite analysis is performed on the zonal-mean zonal wind, Eliassen–Palm fluxes, and two diagnostic variables: the meridional potential vorticity gradient, a zonal-mean quantity that is used to estimate the likelihood of wave breaking, and the wave breaking index (WBI), which is used to evaluate the strength of the wave breaking. The results of this investigation suggest that the background zonal-mean flow associated with La Niña (El Niño) is preconditioned for strong (weak) anticyclonic wave breaking on the equatorward side of the eddy-driven jet, the type of wave breaking that is found to drive positive (negative) SAM events. A probability density function analysis of the WBI, for both La Niña and El Niño, indicates that strong anticyclonic wave breaking takes place much more frequently during La Niña and weak anticyclonic wave breaking during El Niño. It is suggested that these wave breaking characteristics, and their dependency on the background flow, can explain the strong preference for SAM events of one phase during ENSO. The analysis also shows that austral spring SAM events that coincide with ENSO are preceded by strong stratospheric SAM anomalies and then are followed by a prolonged period of wave breaking that lasts for approximately 30 days. These findings suggest that the ENSO background flow also plays a role in the excitation of stratospheric SAM anomalies and that the presence of these stratospheric SAM anomalies in turn excites and then maintains the tropospheric SAM anomalies via a positive eddy feedback.


2021 ◽  
Vol 9 (4) ◽  
pp. 377
Author(s):  
Dong Eun Lee ◽  
Jaehee Kim ◽  
Yujin Heo ◽  
Hyunjin Kang ◽  
Eun Young Lee

The impact of climatic variability in atmospheric conditions on coastal environments accompanies adjustments in both the frequency and intensity of coastal storm surge events. The top winter season daily maximum sea level height events at 20 tidal stations around South Korea were examined to assess such impact of winter extratropical cyclone variability. As the investigation focusses on the most extreme sea level events, the impact of climate change is found to be invisible. It is revealed that the measures of extreme sea level events—frequency and intensity—do not correlate with the local sea surface temperature anomalies. Meanwhile, the frequency of winter extreme events exhibits a clear association with the concurrent climatic indices. It was determined that the annual frequency of the all-time top 5% winter daily maximum sea level events significantly and positively correlates with the NINO3.4 and Pacific Decadal Oscillation (PDO) indices at the majority of the 20 tidal stations. Hence, this indicates an increase in extreme event frequency and intensity, despite localized temperature cooling. This contradicts the expectation of increases in local extreme sea level events due to thermal expansion and global climate change. During El Nino, it is suggested that northward shifts of winter storm tracks associated with El Nino occur, disturbing the sea level around Korea more often. The current dominance of interannual storm track shifts, due to climate variability, over the impact of slow rise on the winter extreme sea level events, implies that coastal extreme sea level events will change through changes in the mechanical drivers rather than thermal expansion. The major storm tracks are predicted to continue shifting northward. The winter extreme sea level events in the midlatitude coastal region might not go through a monotonic change. They are expected to occur more often and more intensively in the near future, but might not continue doing so when northward shifting storm tracks move away from the marginal seas around Korea, as is predicted by the end of the century.


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