scholarly journals The Last 1200 Years of Rainfall/Runoff Variability along the Central Mexico Pacific Coast Associated with the North American Monsoon

Oceans ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 530-545
Author(s):  
Steve Lund ◽  
Emily Mortazavi ◽  
Ellen Platzman ◽  
Caitlin Tems ◽  
William Berelson ◽  
...  
Keyword(s):  
Magnetic Material ◽  
North American ◽  
Pacific Coast ◽  
Ice Age ◽  
Magnetic Data ◽  
North American Monsoon ◽  
Cycle Duration ◽  
Rainfall Runoff ◽  
Runoff Variability

This study presents new evidence for long-term variability in the late Holocene North American Monsoon (NAM), Pacific coast of Mexico. We have carried out a rock magnetic study on two deep-sea sediment cores from the Pacific coast Pescadero Basin. The magnetic intensities estimate total magnetic material and are a proxy for total clastic sediment. Ratios of magnetic intensities estimate the grain size of magnetic material. The rock magnetic data show a decimeter scale, multi-decadal oscillation with fourteen cycles (A-N) over the last 1200 years. These oscillations reflect alternating intervals of stronger/coarser magnetic/clastic flux to the coastal ocean and intervals of weaker/finer magnetic flux. We think these variations are caused by variations in long-term dominance of the NAM; summer (wet) monsoons produce rainy conditions (with runoff) while winter (dry) monsoons produce significant offshore winds, increased upwelling/biological productivity. We can correlate our variability to two other published studies southeast of Pescadero Basin, coastal lake sediments in Laguna de Juanacatlan and a Juxtlahuaca Cave stalagmite. Both of these studies estimate local rainfall. We see evidence of the same pattern of multi-decadal rainfall-runoff variability in these records as we see in Pescadero Basin, which is synchronous to within ±25 years over the last 1200 years. The multi-dacadal pattern of hydrologic variability in all three records varies in cycle duration from ~90-years wet/dry cycles in the Little Ice Age (1400–1850 AD) to ~60-years cycles in the Medieval Climate Optimum (1100–1400 AD). This variability in cycle duration suggests some chaotic nature to the regional NAM climate pattern or some long-term non-linear forcing (PDO?).

scholarly journals Vegetation Dynamics within the North American Monsoon Region

2011 ◽  
Vol 24 (6) ◽  
pp. 1763-1783 ◽  
Author(s):  
Giovanni Forzieri ◽  
Fabio Castelli ◽  
Enrique R. Vivoni
Keyword(s):  
North American ◽  
Vegetation Dynamics ◽  
Vegetation Index ◽  
North American Monsoon ◽  
Terrain Attributes ◽  
The North ◽  
Short Period ◽  
Long Term Trends ◽  
Northwestern Mexico

Abstract The North American monsoon (NAM) leads to a large increase in summer rainfall and a seasonal change in vegetation in the southwestern United States and northwestern Mexico. Understanding the interactions between NAM rainfall and vegetation dynamics is essential for improved climate and hydrologic prediction. In this work, the authors analyze long-term vegetation dynamics over the North American Monsoon Experiment (NAME) tier I domain (20°–35°N, 105°–115°W) using normalized difference vegetation index (NDVI) semimonthly composites at 8-km resolution from 1982 to 2006. The authors derive ecoregions with similar vegetation dynamics using principal component analysis and cluster identification. Based on ecoregion and pixel-scale analyses, this study quantifies the seasonal and interannual vegetation variations, their dependence on geographic position and terrain attributes, and the presence of long-term trends through a set of phenological vegetation metrics. Results reveal that seasonal biomass productivity, as captured by the time-integrated NDVI (TINDVI), is an excellent means to synthesize vegetation dynamics. High TINDVI occurs for ecosystems with a short period of intense greening tuned to the NAM or with a prolonged period of moderate greenness continuing after the NAM. These cases represent different plant strategies (deciduous versus evergreen) that can be adjusted along spatial gradients to cope with seasonal water availability. Long-term trends in TINDVI may also indicate changing conditions favoring ecosystems that intensively use NAM rainfall for rapid productivity, as opposed to delayed and moderate greening. A persistence of these trends could potentially result in the spatial reorganization of ecosystems in the NAM region.

scholarly journals Flash Flooding in Arid/Semiarid Regions: Dissecting the Hydrometeorology and Hydrology of the 19 August 2014 Storm and Flood Hydroclimatology in Arizona

2017 ◽  
Vol 18 (12) ◽  
pp. 3103-3123 ◽  
Author(s):  
Long Yang ◽  
James Smith ◽  
Mary Lynn Baeck ◽  
Efrat Morin ◽  
David C. Goodrich
Keyword(s):  
North American ◽  
Hydrological Modeling ◽  
Rainfall Variability ◽  
Flash Floods ◽  
Flood Frequency ◽  
North American Monsoon ◽  
The North ◽  
Flood Response ◽  
Central Arizona

The hydroclimatology, hydrometeorology, and hydrology of flash floods in the arid/semiarid southwestern United States are examined through empirical analyses of long-term, high-resolution rainfall and stream gauging observations, together with hydrological modeling analyses of the 19 August 2014 storm based on the Kinematic Runoff and Erosion Model (KINEROS2). The analyses presented here are centered on identifying the structure and evolution of flood-producing storms, as well as the interactions of space–time rainfall variability and basin characteristics in determining the upper-tail properties of rainfall and flood magnitudes over this region. This study focuses on four watersheds in Maricopa County, Arizona, with contrasting geomorphological properties. Flash floods over central Arizona are concentrated in both time and space, reflecting controls of the North American monsoon and complex terrain. Thunderstorm systems during the North American monsoon, as represented by the 19 August 2014 storm, are the dominant flood agents that determine the upper tail of flood frequency over central Arizona and that also shape the envelope curve of floods for watersheds smaller than 250 km2. Flood response for the 19 August 2014 storm is associated with storm elements of comparable spatial extent to the drainage area and slow movement for the three compact, headwater watersheds. Flood response for the elongated and relatively flat Skunk Creek highlights the importance of the spatial distribution of rainfall for transmission losses in arid/semiarid watersheds.

scholarly journals The More Extreme Nature of North American Monsoon Precipitation in the Southwestern United States as Revealed by a Historical Climatology of Simulated Severe Weather Events

2017 ◽  
Vol 56 (9) ◽  
pp. 2509-2529 ◽  
Author(s):  
Thang M. Luong ◽  
Christopher L. Castro ◽  
Hsin-I Chang ◽  
Timothy Lahmers ◽  
David K. Adams ◽  
...  
Keyword(s):  
United States ◽  
North American ◽  
Extreme Event ◽  
Severe Weather ◽  
Climate Simulation ◽  
North American Monsoon ◽  
Monsoon Precipitation ◽  
Southwestern United States ◽  
Weather Events

AbstractLong-term changes in North American monsoon (NAM) precipitation intensity in the southwestern United States are evaluated through the use of convective-permitting model simulations of objectively identified severe weather events during “historical past” (1950–70) and “present day” (1991–2010) periods. Severe weather events are the days on which the highest atmospheric instability and moisture occur within a long-term regional climate simulation. Simulations of severe weather event days are performed with convective-permitting (2.5 km) grid spacing, and these simulations are compared with available observed precipitation data to evaluate the model performance and to verify any statistically significant model-simulated trends in precipitation. Statistical evaluation of precipitation extremes is performed using a peaks-over-threshold approach with a generalized Pareto distribution. A statistically significant long-term increase in atmospheric moisture and instability is associated with an increase in extreme monsoon precipitation in observations and simulations of severe weather events, corresponding to similar behavior in station-based precipitation observations in the Southwest. Precipitation is becoming more intense within the context of the diurnal cycle of convection. The largest modeled increases in extreme-event precipitation occur in central and southwestern Arizona, where mesoscale convective systems account for a majority of monsoon precipitation and where relatively large modeled increases in precipitable water occur. Therefore, it is concluded that a more favorable thermodynamic environment in the southwestern United States is facilitating stronger organized monsoon convection during at least the last 20 years.

scholarly journals Intensification of the North American Monsoon Rainfall as Observed From a Long‐Term High‐Density Gauge Network

2019 ◽  
Vol 46 (12) ◽  
pp. 6839-6847 ◽  
Author(s):  
Eleonora M. C. Demaria ◽  
Pieter Hazenberg ◽  
Russell L. Scott ◽  
Menberu B. Meles ◽  
Mary Nichols ◽  
...  
Keyword(s):  
North American ◽  
Monsoon Rainfall ◽  
High Density ◽  
North American Monsoon ◽  
The North

Sophistry, Security, and Socio-Political Structures in the American Revolution; or, Why Jamaica did not Rebel

1986 ◽  
Vol 29 (2) ◽  
pp. 319-344 ◽  
Author(s):  
T. R. Clayton
Keyword(s):  
North America ◽  
British Empire ◽  
American Revolution ◽  
North American ◽  
Western Hemisphere ◽  
American Colonies ◽  
Constitutional Principle ◽  
Mother Country ◽  
Political Structures

Britain's most important American colonies did not rebel in 1776. Thirteen provinces did declare their independence; but no fewer than nineteen colonies in the western hemisphere remained loyal to the mother country. Massachusetts and Virginia may have led the American revolution, but they had never been the leading colonies of the British empire. From the imperial standpoint, the significance of any of the thirteen provinces which rebelled was pale in comparison with that of Jamaica or Barbados. In the century before 1763 the recalcitrance of these two colonies had been more notorious than that of any mainland province and had actually inspired many of the imperial policies cited as long-term grievances by North American patriots in 1774. Real Whig ideology, which some historians have seen as the key to understanding the American revolution, was equally understood by Caribbean elites who, like the continental, had often proved extremely sensitive on questions of constitutional principle. Attacks of ‘frenzied rhetoric’ broke out in Jamaica in 1766 and Barbados in 1776. But these had nothing whatsoever to do with the Stamp Act or events in North America.

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