排序方式： 共有30条查询结果，搜索用时 15 毫秒
1.
Atmospheric forcing of the eastern tropical Pacific: A review 总被引：1，自引：8，他引：1
Jorge A. Amador Eric J. Alfaro Omar G. Lizano Victor O. Magaa 《Progress in Oceanography》2006,69(2-4):101
The increase in marine, land surface, atmospheric and satellite data during recent decades has led to an improved understanding of the air–sea interaction processes in the eastern tropical Pacific. This is also thanks to extensive diagnoses from conceptual and coupled ocean–atmosphere numerical models. In this paper, mean fields of atmospheric variables, such as incoming solar radiation, sea level pressure, winds, wind stress curl, precipitation, evaporation, and surface energy fluxes, are derived from global atmospheric data sets in order to examine the dominant features of the low level atmospheric circulations of the region. The seasonal march of the atmospheric circulations is presented to depict the role of radiative forcing on atmospheric perturbations, especially those dominating the atmosphere at low levels.In the tropics, the trade winds constitute an important north–south energy and moisture exchange mechanism (as part of the low level branch of the Hadley circulation), that determines to a large extent the precipitation distribution in the region, i.e., that associated with the Inter-Tropical Convergence Zone (ITCZ). Monsoonal circulations also play an important role in determining the warm season precipitation distribution over the eastern tropical Pacific through a large variety of air–sea–land interaction mechanisms. Westward traveling waves, tropical cyclones, low latitude cold air intrusions, and other synoptic and mesoscale perturbations associated with the ITCZ are also important elements that modulate the annual rainfall cycle. The low-level jets of the Gulf of California, the Intra-Americas Sea (Gulf of Mexico and Caribbean Sea) and Chocó, Colombia are prominent features of the eastern tropical Pacific low-level circulations related to sub-regional and regional scale precipitation patterns. Observations show that the Intra-Americas Low-Level Jet intensity varies with El Niño/Southern Oscillation (ENSO) phases, however its origin and role in the westward propagation and development of disturbances that may hit the eastern tropical Pacific, such as easterly waves and tropical cyclones, are still unclear. Changes in the intensity of the trade winds in the Caribbean Sea and the Gulf of Mexico (associated with eastern tropical Pacific wind jets) exert an important control on precipitation by means of wind–topography interactions. Gaps in the mountains of southern Mexico and Central America allow strong wind jets to pass over the continent imprinting a unique signal in sea surface temperatures and ocean dynamics of the eastern tropical Pacific.The warm pools of the Americas constitute an important source of moisture for the North American Monsoon System. The northeastern tropical Pacific is a region of intense cyclogenetic activity, just west of the coast of Mesoamerica. Over the oceanic regions, large-scale properties of key variables such as precipitation, moisture, surface energy fluxes and wind stress curl are still uncertain, which inhibits a more comprehensive view of the region and stresses the importance of regional field experiments. Progress has been substantial in the understanding of the ocean and atmospheric dynamics of the eastern tropical Pacific, however, recent observational evidence such as that of a shallow meridional circulation cell in that region, in contrast to the classic concept of the Hadley-type deep meridional circulation, suggests that more in situ observations to validate theories are still necessary.This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific Ocean. 相似文献
2.
Data are presented indicating the complexity and highly variable response of beaches to cold front passages along the northern Gulf of Mexico, in addition to the impacts of tropical cyclones and winter storms. Within the past decade, an increase in the frequency of tropical storms and hurricanes impacting the northern Gulf has dramatically altered the long-term equilibrium of a large portion of this coast. A time series of net sediment flux for subaerial and nearshore environments has been established for a section of this coast in Florida, and to a lesser extent, Mississippi. The data incorporate the morphological signature of six tropical storms/hurricanes and more than 200 frontal passages.
Data indicate that (1) barrier islands can conserve mass during catastrophic hurricanes (e.g., Hurricane Opal, a strong category 4 hurricane near landfall); (2) less severe hurricanes and tropical storms can promote rapid dune aggradation and can contribute sediment to the entire barrier system; (3) cold fronts play a critical role in the poststorm adjustment of the barrier by deflating the subaerial portion of the overwash terrace and eroding its marginal lobe along the bayside beach through locally generated, high frequency, steep waves; and (4) barrier systems along the northern Gulf do not necessarily enter an immediate poststorm recovery phase, although nested in sediment-rich nearshore environments. While high wave energy conditions associated with cold fronts play an integral role in the evolution and maintenance of barriers along the northern Gulf, these events are more effective in reworking sediment after the occurrence of extreme events such as hurricanes. This relationship is even more apparent during the clustering of tropical cyclones.
It is anticipated that these findings will have important implications for the longer term evolution of barrier systems in midlatitude, microtidal settings where the clustering of storms is apparent, and winter storms are significant in intensity and frequency along the coast. 相似文献
3.
A common assumption in the geological analysis of modern reefs is that coral community zonation seen on the surface should also be found in cores from the reef interior. Such assumptions not only underestimate the impact of tropical storms on reef facies development, but have been difficult to test because of restrictions imposed by narrow‐diameter cores and poor recovery. That assumption is tested here using large‐diameter cores recovered from a range of common zones across three Campeche Bank reefs. It is found that cores from the reef‐front, crest, flat and rubble‐cay zones are similar in texture and coral composition, making it impossible to recognize coral assemblages that reflect the surface zonation. Taphonomic signatures imparted by variations in encrustation, bioerosion and cementation, however, produce distinct facies and delineate a clear depth zonation. Cores from the reef‐front zone (2–10 m depth) are characterized by sections of Acropora palmata cobble gravel interspersed with sections of in‐place (but truncated) A. palmata stumps. Upper surfaces of truncated colonies are intensely bioeroded by traces of Entobia isp. and Gastrochaenolites isp. and encrusted by mm‐thick crustose corallines before colony regeneration and, therefore, indicate punctuated growth resulting from a hurricane‐induced cycle of destruction and regeneration. Cores from the reef crest/flat (0–2 m depth) are also characterized by sections of hurricane‐derived A. palmata cobble‐gravels as well as in‐place A. palmata colonies. In contrast to the reef front, however, these cobble gravels are encrusted by cm‐thick crusts of intergrown coralline algae, low‐relief Homotrema and vermetids, bored by traces of Entobia isp. and Trypanites isp. and coated by a dense, peloidal, micrite cement. Cores from the inter‐ to supratidal rubble‐cay zone (+0–5 m) are only composed of A. palmata cobble gravels and, although clasts show evidence of subtidal encrustation and bioerosion, these always represent processes that occurred before deposition on the cay. Instead, these gravels are distinguished on the basis of their limited bioerosion and marine cements, which exhibit fabrics formed in the intertidal zone. These results confirm that hurricanes have a major influence on facies development in Campeche Bank reefs. Instead of reflecting the surface coral zonation, each facies records a distinctive, depth‐related set of taphonomic processes, which reflect colonization, alteration and stabilization following the production of new substrates by hurricanes. 相似文献
4.
Scleractinian coral population size structures and growth rates indicate coral resilience on the fringing reefs of North Jamaica 总被引：1，自引：1，他引：0
Coral reefs throughout the world are under severe challenges from many environmental factors. This paper quantifies the size structure of populations and the growth rates of corals from 2000 to 2008 to test whether the Discovery Bay coral colonies showed resilience in the face of multiple acute stressors of hurricanes and bleaching. There was a reduction in numbers of colonies in the smallest size class for all the species at all the sites in 2006, after the mass bleaching of 2005, with subsequent increases for all species at all sites in 2007 and 2008. Radial growth rates (mm yr−1) of non-branching corals and linear extension rates (mm yr−1) of branching corals calculated on an annual basis from 2000–2008 showed few significant differences either spatially or temporally. At Dairy Bull reef, live coral cover increased from 13 ± 5% in 2006 to 20 ± 9% in 2007 and 31 ± 7% in 2008, while live Acropora species increased from 2 ± 2% in 2006 to 10 ± 4% in 2007 and 22 ± 7% in 2008. These studies indicate good levels of coral resilience on the fringing reefs around Discovery Bay in Jamaica. 相似文献
5.
Andrew B. Kennedy Uriah Gravois Brian Zachry Rick Luettich Tony Whipple Robert Weaver Janelle Reynolds-Fleming Qin J. Chen Roni Avissar 《Continental Shelf Research》2010
Hurricanes can produce extreme nearshore waves and surge, but permanent gauging stations are often much sparser than is desired. This paper describes the rationale behind and outline for rapidly installed temporary coastal gauges, and presents results during Hurricane Gustav (2008). Within 48 h prior to landfall, twenty self-recording pressure gauges were deployed in depths of 1.4–23 m over more than 700 km of coastline, using helicopters to cover the large distances. Results showed a complex picture that was strongly dependent on location. East of the Mississippi Delta, open coast waves were large, and surge reached 3.8 m NAVD88 in marshes. West of the delta but near landfall, waves and surge were generally smaller as the river levees blocked flow from East to West. West of landfall, both waves and surge were very small and the most prominent feature was a water level drawdown that reached 1.5 m. Wave spectra varied strongly depending both on location and time from landfall. 相似文献
6.
Allen Gellis 《地球表面变化过程与地形》1993,18(6):505-517
Runoff generated from large storm events, such as hurricanes, is expected to transport large quantities of suspended sediment. Observations of suspended-sediment loads transported during Hurricane Hugo in the Lago Loìza (Lake Loiza) basin, Puerto Rico, indicate that loads were lower than expected. In the two main tributaries that enter Lago Loìza, Rio Grande de Loìza and Rio Gurabo, 99 600 tonnes of suspended sediment was transported by 58·2 × 106 m3 of runoff in a 48 h period. The storm-average suspended-sediment concentration in the Río Grande de Loìza for Hurricane Hugo was 2290 mgl−1, the second lowest for the 12 storms that have been monitored at this site. In Río Gurabo the storm-average suspended-sediment concentration was 1420 mgl−1, the sixth lowest recorded out of 15 monitored storms. In Quebrada Salvatierra, a small tributary to Río Grande de Loìza, suspended-sediment concentrations were as low as 33 mgl−1 during the peak runoff of 20 m3 s−1. Normally the suspended-sediment concentrations at this discharge are 3000 mgl−1. Hurricane force winds seem to be the most important factor contributing to the lower than expected suspended-sediment loads in the Lago Loìza basin. The high winds caused vegetation and debris to be dislodged and displaced. Debris accumulated on hillslopes and in small channels, blocked bridges and formed debris dams. These dams caused local backwater effects that reduced stream velocities and decreased suspended-sediment loads. 相似文献
7.
R. M. Wooten K. A. Gillon A. C. Witt R. S. Latham T. J. Douglas J. B. Bauer S. J. Fuemmeler L. G. Lee 《Landslides》2008,5(1):31-44
In September 2004, rain from the remnants of Hurricanes Frances and Ivan triggered at least 155 landslides in the Blue Ridge
Mountains of North Carolina. At least 33 debris flows occurred in Macon County, causing 5 deaths, destroying 16 homes, and
damaging infrastructure. We mapped debris flows and debris deposits using a light-detecting and ranging digital elevation
model, remote imagery and field studies integrated in a geographic information system. Evidence of past debris flows was found
at all recent debris flow sites. Orographic rainfall enhancement along topographic escarpments influenced debris flow frequency
at higher elevations. A possible trigger for the Wayah and fatal Peeks Creek debris flows was a spiral rain band within Ivan
that moved across the area with short duration rainfall rates of 150–230 mm/h. Intersecting bedrock structures in polydeformed
metamorphic rock influence the formation of catchments within structural–geomorphic domains where debris flows originate. 相似文献
8.
Stephen Vermette 《Natural Hazards》2007,42(1):91-103
The tropical storm database used in this study was obtained from the National Oceanic and Atmospheric Administration’s (NOAA)
Coastal Service Center, using the Historical Hurricane Tracks tool. Queries were used to determine the number of storms of
tropical origin that have impacted the State and each of its counties. A total of 76 storms of tropical origin passed over
New York State between 1851 and 2005. Of these storms, 14 were classified as hurricanes. The remaining hurricanes passed over
New York State as weaker or modified systems—27 tropical storms, 7 tropical depressions, and 28 extratropical storms (ET).
Long Island experiences a disproportionate number of hurricanes and tropical storms. The average frequency of hurricanes and
storms of tropical origin (all types) is one in every 11 years and one in every 2 years, respectively. September is the month
of greatest frequency for storms of tropical origin, although the storms of greatest intensity tend to arrive later in the
hurricane season and follow different poleward tracks. While El Nino Southern Oscillation (ENSO) cycles appear to show some
influence, the frequency and intensity of storms of tropical origin appear to follow a multidecadal cycle. Storm activity
was greatest in both the late 19th and 20th centuries. During periods of increased storm frequency and intensity storms reached
New York State at progressively later dates. While the number and timing of storms of tropical origin is likely to increase,
this increase appears to be attributed to a multidecadal cycle, as opposed to a trend in global warming. 相似文献
9.
Hurricanes produce mixing and flow divergences (and convergences) that alter the upper-ocean heat content (OHC), which in turn affects the storm. Ocean observations under a hurricane are rare, making it difficult to validate forecast models. Past research have mainly focused on OHC-changes by vertical mixing and tacitly assumed that horizontal transports are slowly varying. Moreover, effects of coastal boundaries on ocean responses to hurricanes are generally omitted. This work uses satellite data to detect and verify forecast isopycnal motions under hurricane Wilma (Oct/16–26/2005) in the Caribbean Sea and the Gulf of Mexico. The model is then used to show that Wilma-induced convergences in northwestern Caribbean Sea produce increased Yucatan-Channel transport into the Gulf ahead of the storm, and the Yucatan–Loop Current front diverts most of this heat around the Loop. This response is distinct from that of an ocean without the Loop, for which warming is widespread north of the channel. These intricate ocean responses can impact hurricane predictions. 相似文献
10.
Factors controlling the survival of coastal dunes during multiple hurricane impacts in 2004 and 2005: Santa Rosa barrier island, Florida 总被引：3，自引：1，他引：2
Santa Rosa Island is an 85 km-long, wave-dominated low-lying barrier island situated along the northwestern Florida coast, facing the Gulf of Mexico. The entire island was severely impacted by Ivan, a strong category 3 hurricane that made landfall about 45 km to the west in September of 2004. Ten months later in July of 2005, Dennis, another category 3 hurricane, made landfall about 30 km east of the western tip of the island. Santa Rosa Island is characterized by well-developed but relatively low dunefields, described in this paper as incipient and established dunes, based on the presence of grassy and woody types of vegetation, respectively. The dunes were severely eroded by the two hurricanes. This paper investigates the factors controlling the regional-scale destruction and survival of the dunefields.Dune survival is controlled by: 1) hurricane characteristics, including intensity, duration, and frequency, and 2) morphological parameters including width of the barrier island, height and width of the dunefields, vegetation type, distance of the dunes to the ocean, and continuity of the dunefields. Three processes of dune destruction are described including, from most to least severe, inundation, overwash, and scarping. The interaction of all the above factors determines the different dune responses to the storm impacts. In general, the extensive and densely woody vegetated dunefields near the bay-side shoreline survived the storms, while the discontinuous dunes with grassy vegetation near the Gulf shoreline were almost completely destroyed. 相似文献