El Nino-Southern Oscillation

Archaeological research in the Australia's northeast Queensland rainforest and margins has revealed a human antiquity of at least 8000 cal year BP within the rainforest and at least 30,000 years on the western edge. Rainforest occupation before 2000 cal year BP was at generally very low levels, after which time settlement of this environment became intensive and probably permanent. Exploitation of toxic varieties of nuts began about 2500 cal year BP, peaking after 1500 cal year BP. This economic development appears crucial to successful human adaptation to rainforests in the area and was pivotal in facilitating the long-term permanent human settlement of the wet tropics. The role of fire, El Niño Southern Oscillation (ENSO) activity and shifting vegetation regimes were important catalysts in providing opportunities for permanent Australian rainforest Aboriginal occupation. The results have implications for global understandings of rainforest occupation by modern people. It demonstrates the wide temporal and spatial variability of human rainforest colonization processes worldwide.

We tested the hypothesis that the El Niño Southern Oscillation influences forest-wide fruit production, which, in turn, limits frugivorous and granivorous mammals on Barro Colorado Island (BCI), Panama. Observations of BCI mammals have been compiled for 49 years. ...

Along with other causes, such as rapid urbanization, the high intensity rainfall has significant contribution in urban area flooding. Understanding this high intensity rainfall over urban area may help us to reduce the damage caused by urban floods. Recent studies reported the relationship between El Niño-Southern Oscillation (ENSO) and Indian extreme rainfall characteristics. In this paper, the extreme precipitation events of the Hyderabad are studied using the Indian Meteorological Department (IMD) hourly rainfall records to understand the effect of ENSO cycle on extreme rainfall events. The forty-three years (1-1-1971 to 31-12-2013) hourly rainfall data is used to construct the intensity-probability distribution curve. The five percent probability extreme rainfall event's frequency is studied for the period of same 43 years. The study results show that the ENSO cycle is inversely proportional to the Hyderabad city extreme rainfall frequency. The results also show that the ext...

The characteristic evolution of El Niño Southern Oscillation (ENSO) on timescales of months to years means that risks to agriculture have structure between seasons and years. The potential for consecutive ENSO-induced yield anomalies is of particular interest in major food producing areas, where modest changes in yield have significant effects on global markets. In this study, we analyse how multi-year El Niño and La Niña life cycles relate to climate sensitive portions of major crop-growing seasons in North and South America. We analyse the dynamics underlying these life cycles to illustrate which aspects of the system are most important for agriculture. In North America, the same-season teleconnections affecting soybean and maize have been well studied, but we demonstrate the importance of lagged soil moisture teleconnections for wheat in the southern Great Plains. In South America, peak ENSO sea surface temperature (SST) teleconnections are concurrent with, and therefore critical for, wheat and maize growing seasons while soil moisture memory in Argentina plays an important role during the soybean growing season. Finally, we show that ENSO teleconnection life cycles are consistent with historical yield anomalies. Both El Niño and La Niña life cycles tend to force consecutive seasons of either above or below expected yields. While the magnitude of the yield anomalies forced by ENSO is often modest, they occur in major crop-producing regions.

Este artículo, ampliado con figuras y referencias bibliográficas, tiene por objetivo mostrar la necesidad de considerar con la importancia debida la ocurrencia de grandes “Niños” en la concepción del desarrollo infraestructural de la costa norperuana y de conocer su periodo de retorno, el que se expresa como una probabilidad. Esta es una necesidad imperiosa, sobre todo si se tiene en cuenta los enormes daños que han causado los últimos Meganiños (1982-83 y 1997-98) y las grandes cantidades de dinero que se invierten  en nuevas obras de desarrollo infraestructural, las que, sin embargo, están expuestas a estos eventos hidrometeorológicos extremos.

This is an advance preview of sections of my principal anthropological study/monograph of personhood, environment and climate change in the Torres Islands. This is the extended version in Spanish, of which a more compact version in English is currently in preparation for submission to an academic publisher.

Los juegos como la mancha o saltar la cuerda, como la mayoría de los deportes, promueven el desarrollo físico pero también les enseñan habilidades como tomar turnos y coordinación. Enseñarle a tu niño estos juegos le dará la oportunidad de aprender reglas, desarrollar un buen criterio y aprender estrategias para el éxito. Además, los deportes y los juegos activos ayudan a que los niños se desarrollen físicamente al usar sus músculos y al mejorar su capacidad aeróbica.

L’ENSO (El Niño Southern Oscillation) è il fenomeno climatico ciclico derivante dell’interazione tra oceano e atmosfera. Si verifica, infatti, una variazione dei comportamenti e delle forze delle componenti coinvolti: la temperatura superficiale, la struttura oceanica e i venti che agiscono sul Pacifico tropicale.
Esso si caratterizza per l'oscillazione di due fenomeni: il Niño e la Niña, che rappresentano  rispettivamente un riscaldamento e un raffreddamento delle acque superficiali del Pacifico equatoriale, in corrispondenza delle coste del Sud America (Perù, Equador, Cile) e di quelle dell’Indonesia (fig. 33).
Si tratta di un ciclo continuo ma irregolare (si presenta con frequenza variabile da tre a otto anni)  di cambiamenti delle condizioni oceaniche e atmosferiche che hanno importanti conseguenze sulle condizioni meteorologiche dell’intero pianeta.
L’illustrazione del fenomeno sarà suddivisa in tre parti, in modo da portare più chiarezza possibile attorno all’evento:
- descrizione  delle condizioni climatiche normali della zona interessata (l’Oceano Pacifico Tropicale);
- breve focus sugli elementi atmosferici che caratterizzano il fenomeno;
- descrizione del Niño e della Niña e loro conseguenze sul sistema climatico globale.

La hambruna que estalló en 1912 refleja años de desequilibrio social, económico y material, y no únicamente las consecuencias de una extensa ausencia de precipitación en la zona. El desastre de 1912 es la materialización dramática de un largo proceso de desadaptación a las condiciones naturales de la península y de empobrecimiento
estructural de sus habitantes. Sin duda, ese proceso no ha cesado en el presente y continúa dando muestras de su indefectible vigor. Aquella catástrofe tuvo la famélica expresión de una agonía lenta, y alcanzó a llevarse casi dos mil vidas tan sólo en ese año. En la actualidad, cuando las sequías se hacen presentes, todo parece indicar
que nunca antes hubiesen ocurrido. Sin preparación para enfrentarlas y sin estrategias preventivas, las sequías continúan generando efectos catastróficos, tal como si se tratase de un fenómeno desconocido y sorprendente.

Menurut (Kailaku 2009) ENSO (El Nino-Southern Oscillation) merupakan salah satu bentuk penyimpangan iklim di Samudera Pasifik yang ditandai dengan kenaikan suhu permukaan laut (SPL) di daerah katulistiwa bagian Tengah dan Timur. Fenomena tersebut memainkan peranan penting terhadap variasi iklim tahunan. Pengaruh ENSO sangat terasa di beberapa wilayah Indonesia yang ditandai dengan jumlah curah hujan lebih kecil dalam tahun ENSO dibandingkan dengan pra dan pasca ENSO, sehingga dapat menyebabkan musim kemarau lebih panjang. Selain dapat mempengaruhi tingginya curah hujan, kejadian El-Nino juga berpengaruh terhadap masuknya musim kemarau.

Daytime fog at Maddens Plain along the Illawarra escarpment south of Sydney between 1975-1990 can be related either to expansive cooling of air directed onshore against the escarpment, or to cloud under conditions of convective instability.  Because of ground drainage, radiation fogs rarely persist into daytime.  Principal component analysis of a suite of regional and local meteorological variables and fog parameters indicates that fog is related to the presence of macro-scale circulation, namely east coast lows, the passage of cold fronts or monsoonal intrusions of low pressure over the interior of New South Wales.  The development and persistence of these lows are linked inseparably to the positioning and movement of anticyclonic cells across the continent.  Surprisingly there appears to be little consistent relationship of either fog characteristics or the synoptic patterns favouring fog formation to phases of the Southern Oscillation.

The linkage between large scale weather patterns that are recurring and persisting is called ``teleconnection``. The teleconnections have a large impact in the nature, the humans and the society. Most of them can be understood by propagation of planetary waves, such as the Rossby or the Kelvin waves.

The major atmospheric jet streams can act as waveguides for Rossby waves as they can trap the energy from a vorticity source and transfer the information around the globe, alternating the weather patterns and creating teleconnections. We wonder how different aspects of the jet, such as the jet strength, width and location can constrain specific features of the trapped, zonal waves such as their wavenumber and amplitudes. The systematic analysis is done with the use of reanalysis data and a barotropic model.

The major source of atmospheric variability over the Northeast Atlantic, Europe and North America is the teleconnection North Atlantic Oscillation (NAO). We investigate the contribution of tropical and extratropical atmospheric forcing mechanisms to the formation of the NAO pattern, using a barotropic model and focusing on time scales of 10-60 days.

The tropical Indian Ocean (IO) exhibits notable atmospheric variability influencing the climate not only on regional, but also on global scale. The Seychelles Dome (SD) in the Southwest IO is a region characterized by a shallow thermocline that experiences large variability and strong seasonal upwelling. The variance of the SD is suggested to have an impact on the IO weather and on teleconnections. We investigate the local and remote response of the coupled ocean-atmosphere system to a shallow SD event, running ensemble experiments with the coupled EC-Earth model.

Compuesto de tres capítulos, recopila de manera sencilla información sobre el efecto climático en Colombia del ENOS, sus efectos socioeconómicos directos e indirectos y sectoriales y las actividades de gestión de riesgo de desastres ejercidas a través de las entidades del SNGRD, resumiendo las fortalezas y vulnerabilidades de las acciones de gestión del riesgo de desastres actuales en Colombia. Uno de los mayores impactos del diagnóstico es que permita generar información pertinente y entendible para las entidades nacionales tomadoras de decisiones y para el público en general que favorezcan la gestión de riesgo en Colombia de manera más eficiente.

The Patos Lagoon estuary (PLE; BR-LTER Site 8; approx. 1,000 km2), located in the extreme south of the Patos Lagoon (32 ° 00 ‘S, 52 ° 05’ W) has a high biological productivity, ecological complexity, and great economic importance due to harbor and industrial activities in the region. In this chapter we present a synthesis about the hydrological and biological variability in the PLE and its relation with the natural and anthropogenic impacts based on the data obtaind continuosly and sistematically for more than ten years.

Influencia del fenómeno de El niño en la cuenca hidrográfica del río Guayas Resumen (Tiene que ser elaborado al final del artículo, incluye resultados y conclusiones) Palabras clave (Introducción (También hay que citar) El fenómeno El Niño es una de las manifestaciones naturales más severas en los ecosistemas costeros e insulares de nuestro país. Históricamente ha sido estudiado en la región del Pacífico Oriental y se caracteriza por un incremento rápido sobre el nivel medio del mar y la temperatura superficial del mismo, así como el movimiento hacia el sur de aguas ecuatoriales cálidas y menos salinas, desplazando a la corriente fría de Humboldt. Este fenómeno afecta de diversas formas las actividades humanas como la agricultura, ganadería, logística, salud pública, lo que conlleva a impactos socioeconómicos y ambientales en grandes proporciones. Ocasiona un aumento en las precipitaciones que dan lugar a desmedidas crecientes en los caudales que inciden en las cuencas hidrográficas. El régimen hidrológico de las cuencas hidrográficas varía dependiendo de la región geográfica donde se encuentre. Incluso si se analizará un país, dicho régimen cambiaría según la región donde se encuentre. Por ejemplo, en la Amazonía Ecuatoriana no se muestra una influencia significativa de El Niño, sin embargo en las zonas costeras las precipitaciones son más evidente aumentando los caudales de los ríos de forma alarmante. Estudiar la fluctuación de las precipitaciones y los caudales que ocurren durante la presencia de El Niño Oscilación Sur (ENOS) permitirá un mejor manejo y conocimiento del recurso hídrico de la cuenca. En este artículo, se usarán métodos estadísticos (distribuciones Gumbel tipo 1, Pearson, Log normal) para estimar el periodo de retorno, excedencias, ponderaciones y diferentes tipos de análisis (Precipitación de meses convencionales VS precipitación de meses con influencia del ENOS), para determinar el grado de asociación del fenómeno ENOS y la oferta hídrica de una zona determinada. Así mismo, determinar el coeficiente de aumento que se tiene comparando un año normal, con un año donde el fenómeno del niño estuvo presente. La cuenca hidrográfica de estudio se la ha escogido por facilidad según la cantidad de datos proporcionados para los diferentes análisis, dicha cuenca es la del Río Guayas. Revisión de literatura (Incluir una breve revisión de Evaporación en la sección de Régimen Hidrológico, Citar por lo menos 2 citas en cada párrafo, citar en inglés)

The level of Cliff Lake, a small, subalpine, moraine-dammed lake in California’s south central Sierra Nevada, was approximately 5 m lower than present for 50 years or more approximately 600 years ago, this determined by radiocarbon dating of wood recovered from a submerged tree stump found in the lake. This finding corresponds to commensurate data from throughout much of western North America, suggesting the duration and magnitude of terminal medieval megadrought was similar throughout the region. Ultimately this datum helps give credence to the perspective that though late Holocene climate in California was indeed variable, the effects of terminal Medieval megadrought was similar across both time and broad geographic expanse.

We investigate the viability of using El Niño-Southern Oscillation (ENSO) and sea surface temperature (SST) data to predict seasonal streamflow for one of the major rivers in Sri Lanka, the Kelani, using correlation analysis, contingency tables, and principal component analysis. The agricultural seasons in Sri Lanka are Yala (April-September) and Maha (October-March). The correlation between the Kelani River streamflow during Yala and ENSO indices (r = À0.41) is significant at 99% level. In addition, the Kelani streamflow during Yala has a correlation with the Central Indian Ocean SST (r = À0.40) that is also significant at the 99% level. The first principal component of the Indo-Pacific Ocean SST is reminiscent of the SST associated with the ENSO mode. A prediction scheme based on this mode for the streamflow during Yala has a skill characterized by a correlation of 0.5 in a cross-validated mode.

The Pole-Equator-Pole (PEP) projects of the
PANASH (Paleoclimates of the Northern and Southern
Hemisphere) programme have significantly advanced our understanding
of past climate change on a global basis and
helped to integrate paleo-science across regions and research
disciplines. PANASH science allows us to constrain predictions
for future climate change and to contribute to the management
of consequent environmental changes. We identify
three broad areas where PEP science makes key contributions.
1. The pattern of global changes. Knowing the exact
timing of glacial advances (synchronous or otherwise) during
the last glaciation is critical to understanding interhemispheric
links in climate. Work in PEPI demonstrated
that the tropical Andes in South America were deglaciated
earlier than the Northern Hemisphere (NH) and that an extended
warming began there ca. 21 000 cal years BP. The
general pattern is consistent with Antarctica and has now
been replicated from studies in Southern Hemisphere (SH)
regions of the PEPII transect. That significant deglaciation
of SH alpine systems and Antarctica led deglaciation of NH
ice sheets may reflect either i) faster response times in alpine
systems and Antarctica, ii) regional moisture patterns that influenced
glacier mass balance, or iii) a SH temperature forcing
that led changes in the NH. This highlights the limitations
of current understanding and the need for further fundamental
paleoclimate research.
2. Changes in modes of operation of oscillatory climate
systems. Work across all the PEP transects has led to the
recognition that the El Ni˜no Southern Oscillation (ENSO)
phenomenon has changed markedly through time. It now appears
that ENSO operated during the last glacial termination and during the early Holocene, but that precipitation teleconnections
even within the Pacific Basin were turned down,
or off. In the modern ENSO phenomenon both inter-annual
and seven year periodicities are present, with the inter-annual
signal dominant. Paleo-data demonstrate that the relative importance
of the two periodicities changes through time, with
longer periodicities dominant in the early Holocene.
3. The recognition of climate modulation of oscillatory
systems by climate events. We examine the relationship of
ENSO to a SH climate event, the Antarctic cold reversal
(ACR), in the New Zealand region. We demonstrate that the
onset of the ACR was associated with the apparent switching
on of an ENSO signal in New Zealand. We infer that this related
to enhanced zonal SW winds with the amplification of
the pressure fields allowing an existing but weak ENSO signal
to manifest itself. Teleconnections of this nature would
be difficult to predict for future abrupt change as boundary
conditions cannot readily be specified. Paleo-data are critical
to predicting the teleconnections of future changes.

This study examined the spatial effects of El Niño and vulnerability on cholera in Peru across the epidemic period of 1991 to 1998. Using Wavelet and GIS analyses, relationships between sea surface temperatures and department-level cholera rates were estimated. In addition, we constructed composite indices to assess spatial vulnerability during the 1997-98 extreme El Niño. The findings demonstrated strong temporal connections in 1997-98, most evident in northern Peru, and less clear connections from 1991-93. Spatially, we found patterns of difference, greater cholera risk in northern coastal Peru in 1997-98, compared to greater risk in central and southern coastal Peru in 1991-92. Overall, the spatial vulnerability analysis suggested preexisting social conditions and disaster impacts increased cholera exposure and infection in 1998. Our study supports the notion that the spatial nature of El Niño's impacts on cholera rates exacerbated cholera vulnerability following the emergence, rather than triggered the epidemic's onset in 1991.

Climate influences a variety of ecological processes. These effects operate through local weather parameters such as temperature, wind, rain, snow, and ocean currents, as well as interactions among these. In the temperate zone, local variations in weather are often coupled over large geographic areas through the transient behavior of atmospheric planetary-scale waves. These variations drive temporally and spatially averaged exchanges of heat, momentum, and water vapor that ultimately determine growth, recruitment, and migration patterns. Recently, there have been several studies of the impact of large-scale climatic forcing on ecological systems. We review how two of the best-known climate phenomena-the North Atlantic Oscillation and the El Niño-Southern Oscillation-affect ecological patterns and processes in both marine and terrestrial systems.

El Nino-Southern Oscillation (ENSO) merupakan salah satu bentuk penyimpangan iklim di Samudera Pasifik yang ditandai dengan kenaikan suhu permukaan laut (SPL) di daerah katulistiwa bagian Tengah dan Timur (Kailaku 2009). Fenomena tersebut memainkan peranan penting terhadap variasi iklim tahunan. Pengaruh ENSO sangat terasa di beberapa wilayah Indonesia yang ditandai dengan jumlah curah hujan lebih kecil dalam tahun ENSO dibandingkan dengan pra dan pasca ENSO, sehingga dapat menyebabkan musim kemarau lebih panjang. Selain dapat mempengaruhi tingginya curah hujan, kejadian El-Nino juga berpengaruh terhadap masuknya musim kemarau. El-Nino biasanya diikuti dengan penurunan curah hujan dan peningkatan suhu udara, sedangkan kejadian La-Nina merangsang kenaikan curah hujan di atas curah hujan normal (Irawan 2006). Pernyataan tersebut diperkuat dengan pendapat menurut Fox (2000) bahwa El Nino dan La Nina merupakan anomali iklim global.

The Southern Oscillation was named in 1924 and its discovery can be traced back to colonial attempts to forecast the Indian monsoon in the late-nineteenth century. The first use of the name ‘El Niño’ to describe a climatic phenomenon appeared in South America in 1893. The term did not, however, originally mean what it does today, being used to describe a seasonal warm water current that is manifest off the coast of northwestern Peru. The history of these two distinct phenomena and their eventual amalgamation into ENSO is closely linked to the activities of the international Guano industry and to efforts to strengthen US soft power in Latin America during the Cold War. Significant advances in El Niño forecasting have occurred since the 1982 event.

Samenvatting Περίληψη Acknowledgements Curriculum vitae viii Chapter 1.2.2 Rossby waves and their propagation characteristics Atmospheric Rossby waves are disturbances from the zonal symmetry in the atmospheric circulation that move westward under the inuence of the rotation of the Earth. In this thesis we study Rossby waves that are excited by tropical Rossby wave sources and travel into the extratropics, creating so-called teleconnection patterns. Rossby waves are named after Carl-Gustaf Arvid Rossby (Rossby (1939)) who identied them and explained their westward propagation in 1939. Rossby waves are dispersive, the longer the wavelength the faster the westward propagation. Their propagation is oset by the background winds such that in the region of the westerly winds, only the longest waves retrograde, move against the ow westward, while the smaller waves are carried eastward. The largest waves are called planetary waves. The planetary Rossby waves determine β * = β − ∂ 2Ū ∂y 2 (1.6) The jet stream is a fast westerly current owing around the globe in the upper troposphere with a sharp meridional prole, that is a consequence of the Earth's rotation and its dierential heating (section 1.2.1). Due to its sharp prole β * tends to have a larger relative maximum thanŪ (see Eq. 1.6). Therefore K s (Eq. 1.7) takes its maximum values along the jet core and reduces quickly toward the anks of the jet. This curvature and the attribute of the rays to bend towards larger K-values allows the changes the waveguiding properties and hence inuence the formation and propagation characteristics of Rossby waves. The pattern is most vigorous in the boreal winter when the circulation is strongest. The eect of NAO variability on the local weather conditions are distinct over Eastern North America, North Atlantic and Northern Europe and often across Southern Europe and the Middle East. Contrary to the extratropical mean ow, the NAO has a pronounced 1.4.2 The Indian Ocean Dipole Another important source of IO variability is the atmosphere-ocean coupled phenomenon widely known as the Indian Ocean Dipole (IOD) (Saji et al (1999)). On a regional scale the IOD has a signicant impact on the atmospheric circulation and precipitation anomalies and on a larger scale the phenomenon correlates with temperature and precipitation anomalies in remote regions, such as Europe, America, South Africa and Northeast Asia (Saji and Yamagata (2003a)). The IOD is characterized by an eastwest SST gradient along the central tropical IO that strongly impacts the atmospheric convection over the basin. When the Central-West IO is warmer than the Eastern IO the event is called a positive event and vice-Along the equator the strong east to southeasterly trade winds allow the cold deep currents, that ow from Antarctica to the west coast of South America, to upwell and keep the SSTs relatively cool along the equatorial cold tongue. In the Western Pacic the trade winds deepen the thermocline and the surface water is warmer. This area of warm ocean waters, the Pacic warm pool, is a major source for atmospheric convection program, which is nanced by the Netherlands Organization for Scientic Research (NWO). We also thank the two anonymous reviewers that provided valuable suggestions and remarks that improved the outcome of this work.

We monitored mortality and recruitment annually for six years for all trees Ն5 cm diameter at breast height in four 1-ha plots in second-growth, lowland rain forests in northeastern Costa Rica. Stands initially ranged in age from 12 to 25 years since abandonment of cattle pastures. In younger stands, abundance decreased 10-20% in the small size class (5-9.9 cm dbh), but increased 49-100% in the large size class (Ն25 cm dbh). In the two youngest plots, 45.0% and 27.6% of the common tree species showed annual population increases of 3% or more, whereas 10% showed annual decreases of 4% or more. Annual rates of tree mortality for all size classes and recruitment into the 5-cm size class varied significantly among years, and mortality rates of trees 5-9.9 cm dbh were higher in younger than in older stands. Tree mortality was highest during the 1997-1998 El Niño Southern Oscillation (ENSO) year; on average, 5.6%, 3.5%, and 1.4% of trees died in the small, intermediate, and large size classes, respectively. Mortality rates during the ENSO year were 1.9 times higher for trees Ն10 cm dbh compared to non-ENSO years. Annual mortality rates for trees Ն10 cm dbh decreased significantly with increasing dry-season rainfall, but not with total annual rainfall during the census periods. Tree mortality (particularly for trees Ն25 cm dbh) in these secondary forests was highly sensitive to dryseason rainfall, even during non-ENSO years. Increased tree mortality during ENSO years is likely to accelerate forest dynamics and successional change in wet tropical secondgrowth forests.

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We inferred climate drivers of 20th-century years with regionally synchronous forest fires in the U.S. northern Rockies. We derived annual fire extent from an existing fire atlas that includes 5038 fire polygons recorded from 12 070 086 ha, or 71% of the forested land in Idaho and Montana west of the Continental Divide. The 11 regional-fire years, those exceeding the 90th percentile in annual fire extent from 1900 to 2003 (.102 314 ha or ;1% of the fire atlas recording area), were concentrated early and late in the century (six from 1900 to 1934 and five from 1988 to 2003). During both periods, regional-fire years were ones when warm springs were followed by warm, dry summers and also when the Pacific Decadal Oscillation (PDO) was positive. Spring snowpack was likely reduced during warm springs and when PDO was positive, resulting in longer fire seasons. Regional-fire years did not vary with El Nin˜o-Southern Oscillation (ENSO) or with climate in antecedent years. The long mid-20th century period lacking regional-fire years had generally cool springs, generally negative PDO, and a lack of extremely dry summers; also, this was a period of active fire suppression. The climate drivers of regionally synchronous fire that we inferred are congruent with those of previous centuries in this region, suggesting a strong influence of spring and summer climate on fire activity throughout the 20th century despite major land-use change and fire suppression efforts. The relatively cool, moist climate during the mid-century gap in regional-fire years likely contributed to the success of fire suppression during that period. In every regional-fire year, fires burned across a range of vegetation types. Given our results and the projections for warmer springs and continued warm, dry summers, forests of the U.S. northern Rockies are likely to experience synchronous, large fires in the future.

Many modelling studies suggest that the El Niño Southern Oscillation (ENSO), in interaction with the tropical Pacific background climate, will change under rising atmospheric greenhouse gas concentrations. Solar geoengineering (reducing the solar flux from outer space) has been proposed as a means to counteract anthropogenic greenhouse-induced changes in climate. Effectiveness of solar geoengineering is uncertain. Robust results are particularly difficult to obtain for ENSO because existing geoengineering simulations are too short (typically ~50 years) to detect statistically significant changes in the highly variable tropical Pacific background climate. We here present results from a 1000-year sunshade geoengineering simulation, G1, carried out with the coupled atmosphere-ocean general circulation model HadCM3L. In agreement with previous studies, reducing the shortwave solar flux  more than compensates the warming in the tropical Pacific that develops in the 4×CO2 scenario: we observe an overcooling of 0.3oC (5 %) and 0.23-mm day-1 (5 %) reduction in mean rainfall relative to preindustrial conditions in the G1 simulation. This is due to the different latitudinal distributions of the shortwave (solar) and longwave (CO2) forcings.The location of the Intertropical Convergence Zone (ITCZ) located north of equator in the tropical Pacific, which moved 7.5o southwards under 4×CO2, is also restored to its preindustrial location. However, other aspects of the tropical Pacific mean climate are not reset as effectively. Relative to preindustrial conditions, in G1 the zonal wind stress, zonal sea surface temperature (SST) gradient, and meridional SST gradient are reduced by 10 %, 11 %, and 9 %, respectively, and the Pacific Walker Circulation (PWC) is consistently weakened. The overall amplitude of ENSO strengthens by 5-8 %, but there is a 65 % reduction in the asymmetry between cold and warm events: cold events intensify more than warm events. Importantly, the frequency of extreme El Niño and La Niña events increases by 44 % and 32 %, respectively, while the total number of El Niño events increases by 12 %. Paradoxically, while the number of total and extreme events increase, the most extreme El Niño events also become weaker relative to preindustrial state while the La Niña events become stronger. That is, extreme El Niño events in G1 become less extreme than in preindustrial conditions, but extreme El Niño events become more frequent. In contrast, extreme La Niña events become stronger in G1. This is in agreement with the general overcooling of the tropical Pacific in G1 relative to preindustrial conditions, which depict a shift towards generally more La Niña-like conditions.

Prosopis pallida H.B.K. is one of the most economically and ecologically important tree species in the arid and semi-arid lands of the American continent. Sections of P. pallida were used to describe its wood anatomy and to determine whether annual rings were visible or not. Results showed that P. pallida has well-differentiated annual growth rings and is therefore suitable for dendrochronological studies. Tree ring chronologies correlate well with precipitation events related to El Nin˜o Southern Oscillation phases. A master chronology for the northern area of Peru was built with these data, and some physiological derivations from the anatomy of P. pallida wood are discussed. r

This paper estimates regional tornado risk from records of past events using statistical models. First, a spatial model is fit to the tornado counts aggregated in counties with terms that control for changes in observational practices over time. Results provide a long-term view of risk that delineates the main tornado corridors in the United States where the expected annual rate exceeds two tornadoes per 10,000 square km. A few counties in the Texas Panhandle and central Kansas have annual rates that exceed four tornadoes per 10,000 square km. Refitting the model after removing the least damaging tornadoes from the data (EF0) produces a similar map but with the greatest tornado risk shifted south and eastward. Second, a space-time model is fit to the counts aggregated in raster cells with terms that control for changes in climate factors. Results provide a short-term view of risk. The short-term view identifies a shift of tornado activity away from the Ohio Valley under El Niño conditions and away from the Southeast under positive North Atlantic oscillation conditions. The combined predictor effects on the local rates is quantified by fitting the model after leaving out the year to be predicted from the data. The models provide state-of-the-art views of tornado risk that can be used by government agencies, the insurance industry, and the general public.

The Indian subcontinent witnessed a severe monsoon drought in 2002, which largely resulted from a major rainfall deficiency in the month of July. While moderate El Nino conditions prevailed during this period, the atmospheric convective activity was anomalously enhanced over northwest and north-central Pacific in the 10-20°N latitude belt; and heavy rainfall occurred over this region in association with a series of northward moving tropical cyclones. Similar out-of-phase rainfall variations over the Indian region and the northwest (NW) Pacific have been observed during other instances of El Nino/Southern Oscillation (ENSO). The dynamical linkage corresponding to this out-of-phase rainfall variability is explored in this study by conducting a set of numerical experiments using an atmospheric general circulation model. The results from the model simulations lend credence to the role of the tropical Pacific sea surface temperature anomalies in forcing the out-of-phase precipitation variability over the NW Pacific and the Indian monsoon region. It is seen that the ENSO induced circulation response reveals an anomalous pattern comprising of alternating highs and lows which extend meridionally from the equatorial region into the sub-tropic and midlatitude regions of west-central Pacific. This meridional pattern is associated with an anomalous cyclonic circulation over NW Pacific, which is found to favor enhanced tropical cyclonic activity and intensified convection over the region. In turn, the intensified convection over NW Pacific induces subsidence and rainfall deficiency over the Indian landmass through anomalous east-west circulation in the 10-20°N latitude belt. Based on the present findings, it is suggested that the convective activity over NW Pacific is an important component in mediating the ENSO-monsoon teleconnection dynamics.

A recent increase in studies of b diversity has yielded a confusing array of concepts, measures and methods. Here, we provide a roadmap of the most widely used and ecologically relevant approaches for analysis through a series of mission statements. We distinguish two types of b diversity: directional turnover along a gradient vs. nondirectional variation. Different measures emphasize different properties of ecological data. Such properties include the degree of emphasis on presence ⁄ absence vs. relative abundance information and the inclusion vs. exclusion of joint absences. Judicious use of multiple measures in concert can uncover the underlying nature of patterns in b diversity for a given dataset. A case study of Indonesian coral assemblages shows the utility of a multi-faceted approach. We advocate careful consideration of relevant questions, matched by appropriate analyses. The rigorous application of null models will also help to reveal potential processes driving observed patterns in b diversity.