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1.
Arthur C. R. Gleason Diego Lirman Dana Williams Nuno R. Gracias Brooke E. Gintert Hossein Madjidi R. Pamela Reid G. Chris Boynton Shahriar Negahdaripour Margaret Miller & Philip Kramer 《Marine Ecology》2007,28(2):254-258
Four hurricanes impacted the reefs of Florida in 2005. In this study, we evaluate the combined impacts of hurricanes Dennis, Katrina, Rita, and Wilma on a population of Acropora palmata using a newly developed video‐mosaic methodology that provides a high‐resolution, spatially accurate landscape view of the reef benthos. Storm damage to A. palmata was surprisingly limited; only 2 out of 19 colonies were removed from the study plot at Molasses Reef. The net tissue losses for those colonies that remained were only 10% and mean diameter of colonies decreased slightly from 88.4 to 79.6 cm. In contrast, the damage to the reef framework was more severe, and a large section (6 m in diameter) was dislodged, overturned, and transported to the bottom of the reef spur. The data presented here show that two‐dimensional video‐mosaic technology is well‐suited to assess the impacts of physical disturbance on coral reefs and can be used to complement existing survey methodologies. 相似文献
2.
Byron C. Shumate Claire L. Schelske Thomas L. Crisman William F. Kenney 《Journal of Paleolimnology》2002,27(1):71-77
A paleolimnological evaluation of cladoceran microfossils was initiated to study limnological changes in Lake Apopka, a large (125 km2), shallow (mean depth = 1.6 m), warm, polymictic lake in central Florida. The lake switched from macrophyte to algal dominance in the late 1940s, creating a Sediment Discontinuity Layer (SDL) that can be visually used to separate sediments derived from macrophytes and phytoplankton. Cladoceran microfossils were enumerated as a means of corroborating extant eutrophication data from the sediment record. Inferences about the timing and trajectory of eutrophication were made using the cladoceran-based paleo-reconstruction. The cladoceran community of Lake Apopka began to change abruptly in both total abundance and relative percent abundance just before the lake shifted from macrophyte to algal dominance. Alona affinis, a mud-vegetation associated cladoceran, disappeared before the SDL was formed. Planktonic and benthic species also began to increase below the SDL, indicating an increase in production of both planktonic and benthic species. Chydorus cf. sphaericus, an indicator of nutrient loading, increased relative to all other cladocerans beginning in the layer below the SDL and continuing upcore. Changes in the transitional sediment layer formed before the lake switched to phytoplankton dominance, including an increase in total phosphorus concentration, suggest a more gradual eutrophication process than previously reported. Data from this study supported conclusions from other paleolimnological studies that suggested anthropogenic phosphorus loading was the key factor in the hypereutrophication of Lake Apopka. 相似文献
3.
Stable Isotope Ratios: Hurricane Olivia 总被引：1，自引：0，他引：1
James R. Lawrence Stanley David Gedzelman John Gamache Michael Black 《Journal of Atmospheric Chemistry》2002,41(1):67-82
The oxygen and hydrogen isotopic compositions of rains from HurricaneOlivia (1994) in the eastern Pacific were measured. The rains werecollected on 24 and 25 September during airplane flights conducted at anelevation of 3 km. Hurricane Olivia peaked in intensity to a category-4storm between the two dates. Isotope ratios of rains from HurricaneOlivia were markedly lower ( 18O = –13.9to –28.8) than that of rain collected from a thunderstormat an elevation of 2.3 km outside the influence of Olivia (18O = –3.8). A distinct decrease in isotoperatios from the first day to the next ( 18O =–18.4 to –21.9) in Hurricane Olivia wasattributed to decreased updraft velocities and outflow aloft. Thisshifted the isotopic water mass balance so that fewer hydrometeors werelifted and more ice descended to flight level. A decrease in the averagedeuterium excess from the first day to the next (d = 15.5 to 7.1)was attributed to an increase in the relative humidity of the watervapor `source' area. We hypothesize that the `source' region for therain was in the boundary layer near the storm center and that becausethe hurricane was at peak intensity prior to the second day the relative humidity was higher. 相似文献
4.
Tong ZHU Da-Lin ZHANG 《大气科学进展》2006,23(1):14-22
The effects of storm-induced sea surface temperature （SST） cooling on hurricane intensity are investigated using a 5-day cloud-resolving simulation of Hurricane Bonnie （1998）. Two sensitivity simulations are performed in which the storm-induced cooling is either ignored or shifted close to the modeled storm track. Results show marked sensitivity of the model-simulated storm intensity to the magnitude and relative position with respect to the hurricane track. It is shown that incorporation of the storm-induced cooling, with an average value of 1.3℃, causes a 25-hPa weakening of the hurricane, which is about 20 hPa per 1℃ change in SST. Shifting the SST cooling close to the storm track generates the weakest storm, accounting for about 47% reduction in the storm intensity. It is found that the storm intensity changes are well correlated with the air-sea temperature difference. The results have important implications for the use of coupled hurricane-ocean models for numerical prediction of tropical cyclones. 相似文献
5.
T. N. Krishnamurti L. Stefanova L. Watson S. Pattnaik 《Pure and Applied Geophysics》2007,164(8-9):1429-1441
This paper addresses two avenues for gaining insight into the hurricane intensity issue—the angular momentum approach and
the scale interaction approach. In the angular momentum framework, the torques acting on a parcel's angular momentum are considered
along an inflowing trajectory in order to construct the angular momentum budget. These torques are separable into three components:
The pressure torque, the surface friction torque, and the cloud torque. All torques are found to diminish the angular momentum
of an inflowing parcel, with the cloud torques having the most important role. In the scale interaction approach, energy exchanges
among different scales within a hurricane are considered as a means of understanding hurricane intensity. It is found that
the majority of kinetic energy contribution to the hurricane scales originates from potential-to-kinetic in-scale energy conversions.
The contribution of mean-wave interactions in the kinetic energy varies with distance from the center and with the life stage
of a storm. In the early stages, as the disorganized convection becomes organized on the hurricane scales, upscale energy
transfers (i.e., from small to large scale) are found to take place in the outer radii of the storm. In a mature storm, the kinetic energy
transfers are downscale, except for the inner radii. 相似文献
6.
In September 2008, Hurricanes Gustav and Ike generated major storm surges which impacted the Lake Pontchartrain estuary in Louisiana. This paper presents analyses of in situ measurements acquired during these storm events. The main data used in the analyses were from three bottom mounted moorings equipped with conductivity, temperature, and depth sensors, acoustic Doppler current profilers (ADCPs), and a semi-permanent laterally mounted horizontal acoustic Doppler profiler (ADP). These moorings were deployed in the three major tidal channels that connect Lake Pontchartrain with the coastal ocean. A process similar to tidal straining was observed: the vertical shear of the horizontal velocity was negligible during the inundation stage, but a shear of 0.8 m/s over a less than 5 m water column was recorded during the receding stage, 2–3 times the normal tidal oscillations. The surge reached its peak in the Industrial Canal 1.4–2.1 h before those in the other two channels. The inward flux of water lasted for a shorter time period than that of the outward flux. The inward flux was also observed to have much smaller magnitude than the outward flux (∼960–1200 vs. 2100–3100 million m3). The imbalance was believed to have been caused by the additional water into Lake Pontchartrain through some small rivers and inundation over the land plus rainfall from the hurricanes. The flux through the Industrial Canal was 8–12%, while the flux through the other two tidal passes ranged between 17% and 70% of the total, but mostly split roughly half-half of the remaining (∼88–92% of the total). 相似文献
7.
Assimilating Best Track Minimum Sea Level Pressure Data Together with Doppler Radar Data Using an Ensemble Kalman Filter for Hurricane Ike (2008) at a Cloud-Resolving Resolution 
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下载免费PDF全文 Extending an earlier study, the best track minimum sea level pressure (MSLP) data are assimilated for landfalling Hurricane Ike (2008) using an ensemble Kalman filter (EnKF), in addition to data from two coastal ground-based Doppler radars, at a 4-km grid spacing. Treated as a sea level pressure observation, the MSLP assimilation by the EnKF enhances the hurricane warm core structure and results in a stronger and deeper analyzed vortex than that in the GFS (Global Forecast System) analysis; it also improves the subsequent 18-h hurricane intensity and track forecasts. With a 2-h total assimilation window length, the assimilation of MSLP data interpolated to 10-min intervals results in more balanced analyses with smaller subsequent forecast error growth and better intensity and track forecasts than when the data are assimilated every 60 minutes. Radar data are always assimilated at 10-min intervals. For both intensity and track forecasts, assimilating MSLP only outperforms assimilating radar reflectivity (Z) only. For intensity forecast, assimilating MSLP at 10-min intervals outperforms radar radial wind (Vr) data (assimilated at 10-min intervals), but assimilating MSLP at 60-min intervals fails to beat Vr data. For track forecast, MSLP assimilation has a slightly (noticeably) larger positive impact than Vr(Z) data. When Vr or Z is combined with MSLP, both intensity and track forecasts are improved more than the assimilation of individual observation type. When the total assimilation window length is reduced to 1h or less, the assimilation of MSLP alone even at 10-min intervals produces poorer 18-h intensity forecasts than assimilating Vr only, indicating that many assimilation cycles are needed to establish balanced analyses when MSLP data alone are assimilated; this is due to the very limited pieces of information that MSLP data provide. 相似文献
8.
Abir Gupta 《Gondwana Research》2000,3(4):529-544
The Permian Gondwana sediments in the Damodar-Koel Valley, Rajmahal and Deoghar basins were deposited on a northwest palaeoslope in broad valleys within uplands (e.g. Aravalli-Vindhyan, Chattisgarh, Chotanagpur and Santhal Parganas upland). The main winds during Permian Period were mostly the westerly winds coming from the northwest low pressure belt in the Tethys, which found no barrier between the Vindhyan and Santhal Parganas uplands and then changing its direction, moving towards east. Frequent storm activity also took place from the northwest Tethyan low pressure belt and followed the same path of wind. Possibly there was a barrier in the form of a dense rain forest or elevated land at the place of East Bokaro coalfield and its adjoining southern part, which acted as a deterrent and minimized the effect of storm towards further east of the Damodar Valley. Intense tropical hurricanes for the generation of storm generated bedforms, cannot be ruled out, which probably, in some cases, causes marine inundation/flooding deep into the landmass and also mass (?) uprooting of trees. 相似文献
9.
This research analyzes the relationship between tropical cyclones and fine particulate matter (PM2.5) for landfalling Atlantic tropical cyclones from 2000 to 2015. Daily mean PM2.5 concentrations were collected from the United States Environmental Protection Agency. Tropical cyclone data were acquired from Tropical Prediction Center Best Track Reanalysis in Unisys weather. GRIdded Binary (GRIB formatted) data were downloaded from the Data Support Section of the Computational and Information Systems Laboratory at the National Center for Atmospheric Research (NCAR). Tracks of tropical cyclones were overlaid with the interpolated daily mean PM2.5 concentration value. Results suggest that, in general, tracks are distant from areas with the largest PM2.5 concentrations. To examine the cause-effect nature of this relationship, simulation using the Weather Research and Forecasting (WRF) model suggests that the intensity of Hurricane Lili was weakened only after passing the most PM2.5-polluted area in Louisiana. This result suggests that aerosol loading may weaken the intensity of tropical cyclones, at least in some cases. 相似文献
10.
基于美国台风预报系统（Hurricane Weather Research and Forecasting,HWRF）,研究了气团订正方法对GOES-13/15静止卫星成像仪资料同化效果的改进作用,选取了2012年6月23日生成于大西洋地区的台风Debby作为研究对象,通过一组对照试验比较了气团订正前后台风路径和初始场相关物理量的差异,结果表明:气团订正能显著减小GOES-13/15静止卫星成像仪资料的系统偏差,明显提高台风路径的预报效果,气团订正使得预报的台风路径与观测路径的平均偏差和标准差降低了30%左右,提前6 h实现了台风路径的正确转向。物理机制分析表明,经过气团订正后的静止卫星资料增强了位于台风东南侧副热带高压的强度,同时增加了台风东部的温度和比湿,在引导气流和大气温、湿场的共同作用下,台风预报路径实现了正确转向。 相似文献