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Mexican drought: an observational modeling and tree ring study of variability and climate change
, 2008
"... Se examina la variabilidad del hidroclima mexicano –con un enfoque particular en las sequías persistentes– mediante observaciones, modelos de simulación forzados por las temperaturas históricas de la superficie marina (SST por sus siglas en inglés), reconstrucciones paleoclimáticas basadas en anillo ..."
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Se examina la variabilidad del hidroclima mexicano –con un enfoque particular en las sequías persistentes– mediante observaciones, modelos de simulación forzados por las temperaturas históricas de la superficie marina (SST por sus siglas en inglés), reconstrucciones paleoclimáticas basadas en anillos de árboles, modelos de simulación y proyecciones de cambios de clima tanto de origen natural como antrópico. Durante la mitad invernal del año, el hidroclima a lo largo y ancho de México se ve influenciado por la condición del Océano Pacífico tropical, mientras que la influencia del Atlántico es mínima. Cuando las condiciones de El Niño emergen, los inviernos mexicanos tienden a ser mas húmedos. En la mitad veraniega, cuando El Niño prevalece, el norte de México es también más húmedo, mientras que el sur es más seco. Cuando el Atlántico norte tropical se calienta, el norte de México se caracteriza por ser más seco y el sur más húmedo. Estas relaciones son bien reproducidas en los conjuntos de modelos de simulación de la atmósfera, forzados por las SST históricas para el período que se extiende de 1856 a 2002. Se utilizan ensambles extensos de integraciones de 100 días para examinar día con día la evolución de la circulación atmosférica y la precipitación en respuesta a la repentina imposición de la anomalía de la SST de El Niño en la mitad veraniega del año. Las ondas de Kelvin se propagan hacia el este y causan de inmediato una divergencia incrementada de la columna integrada de humedad y precipitación reducida sobre los mares americanos
Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/jqs.1303 Megadroughts in North America: placing IPCC
"... projections of hydroclimatic change in a long-term palaeoclimate context ..."
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Blueprints for Medieval hydroclimate $
"... According to tree ring and other records, a series of severe droughts that lasted for decades afflicted western North America during the Medieval period resulting in a more arid climate than in subsequent centuries. A review of proxy evidence from around the world indicates that North American megad ..."
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According to tree ring and other records, a series of severe droughts that lasted for decades afflicted western North America during the Medieval period resulting in a more arid climate than in subsequent centuries. A review of proxy evidence from around the world indicates that North American megadroughts were part of a global pattern of Medieval hydroclimate that was distinct from that of today. In particular, the Medieval hydroclimate was wet in northern South America, dry in mid-latitude South America, dry in eastern Africa but with strong Nile River floods and a strong Indian monsoon. This pattern is similar to that accompanying persistent North American droughts in the instrumental era. This pattern is compared to that associated with familiar climate phenomena. The best fit comes from a persistently La Nin ˜ a-like tropical Pacific and the warm phase of the so-called Atlantic Multidecadal Oscillation. A positive North Atlantic Oscillation (NAO) also helps to explain the Medieval hydroclimate pattern. Limited sea surface temperature reconstructions support the contention that the tropical Pacific was cold and the subtropical North Atlantic was warm, ideal conditions for North American drought. Tentative modeling results indicate that a multi-century La Nin ˜ a-like state could have arisen as a coupled atmosphere–ocean response to high irradiance and weak volcanism during the Medieval period and that this could in turn have induced a persistently positive NAO state. A La Nin ˜ a-like state could also induce a strengthening of the North Atlantic meridional overturning circulation, and hence warming of the North Atlantic Ocean, by (i) the ocean response to the positive NAO and by shifting the southern mid-latitude westerlies poleward which (ii) will increase the salt flux from the Indian Ocean into the South Atlantic and (iii) drive stronger
v l ste
"... eral transects in Lake 239. Declines of ∼1–3 m occurred during the late that have a surface outflow) to climatic conditions is more conditions suggests that a longer-term history of climatic con-ditions may be archived in the sedimentary record. ELA lies within the Winnipeg River Drainage Basin, whi ..."
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eral transects in Lake 239. Declines of ∼1–3 m occurred during the late that have a surface outflow) to climatic conditions is more conditions suggests that a longer-term history of climatic con-ditions may be archived in the sedimentary record. ELA lies within the Winnipeg River Drainage Basin, which provides a major component of the hydroelectric power gene-Available online at www.sciencedirect.com Quaternary Research 69 (20Numerous studies indicate that the droughts of the 20th century in western North America and the northern Great Plains were shorter and less extreme than those that occurred during the past several thousand years (e.g., Laird et al., 2003; Woodhouse, 2004; Cook et al., 2007) and represent only a small subset of the range in natural climatic variability, even in comparison to the last few centuries (St. George and Nielsen, 2002; Case and MacDonald, 2003; Sauchyn et al., 2003). In arid
A Dendroclimatic Investigation of Moisture Variability and Drought in the Greater Victoria Water Supply Area, Vancouver Island, British Columbia.
"... or other means, without the permission of the author. ii Supervisory Committee ..."
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or other means, without the permission of the author. ii Supervisory Committee
Quantification of Land-Atmosphere Coupling and Implications for Drought Persistence In Observations and Model Simulations of 20th Century Climate and 21st Century Climate Change
"... Of all recurring natural disasters, long-term drought is one of the most devastating and costly due to large spatial extent and often long duration. The mechanisms responsible for the maintenance of long-term droughts are not well understood, however many drought analyses allege the importance of la ..."
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Of all recurring natural disasters, long-term drought is one of the most devastating and costly due to large spatial extent and often long duration. The mechanisms responsible for the maintenance of long-term droughts are not well understood, however many drought analyses allege the importance of land-atmosphere feedbacks and speculate that these feedbacks will amplify changes in the hydrological cycle in the presence of climate change, increasing drought severity. A statistical lagged correlation method is applied to IPPC model and observed precipitation and evaporation data to quantify JJA land-atmosphere coupling based on a positive feedback between evaporation and later precipitation. Results of this statistical method are broadly consistent with results of other land-atmosphere coupling analyses with some important differences, most notably in the Sahara and Arabian deserts. In addition, drought analysis is conducted using a percentile scheme to quantify JJA drought frequency and drought persistence. The relationship between land-atmosphere coupling and drought persistence is analyzed by plotting drought persistence against land-atmosphere coupling; the result shows a positive linear relationship in three regions examined in which
Blueprints for Medieval hydroclimate$
"... According to tree ring and other records, a series of severe droughts that lasted for decades afflicted western North America during the Medieval period resulting in a more arid climate than in subsequent centuries. A review of proxy evidence from around the world indicates that North American megad ..."
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According to tree ring and other records, a series of severe droughts that lasted for decades afflicted western North America during the Medieval period resulting in a more arid climate than in subsequent centuries. A review of proxy evidence from around the world indicates that North American megadroughts were part of a global pattern of Medieval hydroclimate that was distinct from that of today. In particular, the Medieval hydroclimate was wet in northern South America, dry in mid-latitude South America, dry in eastern Africa but with strong Nile River floods and a strong Indian monsoon. This pattern is similar to that accompanying persistent North American droughts in the instrumental era. This pattern is compared to that associated with familiar climate phenomena. The best fit comes from a persistently La Niña-like tropical Pacific and the warm phase of the so-called Atlantic Multidecadal Oscillation. A positive North Atlantic Oscillation (NAO) also helps to explain the Medieval hydroclimate pattern. Limited sea surface temperature reconstructions support the contention that the tropical Pacific was cold and the subtropical North Atlantic was warm, ideal conditions for North American drought. Tentative modeling results indicate that a multi-century La Niña-like state could have arisen as a coupled atmosphere–ocean response to high irradiance and weak volcanism during the Medieval period and that this could in turn have induced a persistently positive NAO state. A La Niña-like state could also induce a strengthening of the North Atlantic meridional overturning circulation, and hence warming of the North Atlantic Ocean, by (i) the ocean response to the positive NAO and by shifting the southern mid-latitude westerlies poleward which (ii) will increase the salt flux from the Indian Ocean into the South Atlantic and (iii) drive stronger Southern Ocean upwelling. r 2007 Elsevier Ltd. All rights reserved.
