Climate

Extreme storm events, landscape denudation, and carbon sequestration: Typhoon Mindulle, Choshui River, Taiwan

Goldsmith, S. T.; Carey, A. E.; Lyons, W. B.; Kao, S. J.; Lee, T. Y.;
Chen, J. Extreme storm events, landscape denudation, and
carbon sequestration: Typhoon Mindulle, Choshui River, Taiwan.
Geology 2008, 36 (6), 483–486.

Abstract: 
We have performed the fi rst known semicontinuous monitoring of particulate organic carbon (POC) fl uxes and dissolved Si concentrations delivered to the ocean during a typhoon. Sampling of the Choshui River in Taiwan during Typhoon Mindulle in 2004 revealed a POC fl ux of 5.00 × 105 t associated with a sediment fl ux of 61 Mt during a 96 h period. The linkage of high amounts of POC with sediment concentrations capable of generating a hyperpycnal plume upon reaching the ocean provides the fi rst known evidence for the rapid delivery and burial of POC from the terrestrial system. These fl uxes, when combined with storm-derived CO2 consumption of 1.65 × 108 mol from silicate weathering, elucidate the important role of these tropical cyclone events on small mountainous rivers as a global sink of CO2.

African Droughts and Dust Transport to the Caribbean: Climate Change Implications

Joseph M. Prospero, and
Peter J. Lamb
African Droughts and Dust Transport to the Caribbean: Climate Change Implications
Science 7 November 2003:
Vol. 302 no. 5647 pp. 1024-1027
DOI: 10.1126/science.1089915

Abstract: 
Great quantities of African dust are carried over large areas of the Atlantic and to the Caribbean during much of the year. Measurements made from 1965 to 1998 in Barbados trade winds show large interannual changes that are highly anticorrelated with rainfall in the Soudano-Sahel, a region that has suffered varying degrees of drought since 1970. Regression estimates based on long-term rainfall data suggest that dust concentrations were sharply lower during much of the 20th century before 1970, when rainfall was more normal. Because of the great sensitivity of dust emissions to climate, future changes in climate could result in large changes in emissions from African and other arid regions that, in turn, could lead to impacts on climate over large areas

New evidence for enhanced ocean primary production triggered by tropical cyclone

Lin, I., W. T. Liu, C.-C. Wu, G. T.
F. Wong, C. Hu, Z. Chen, W.-D. Liang, Y. Yang, and K.-K. Liu,
New evidence for enhanced ocean primary production triggered
by tropical cyclone, Geophys. Res. Lett., 30(13), 1718,
doi:10.1029/2003GL017141, 2003.

Abstract: 
New evidence based on recent satellite data is presented to provide a rare opportunity in quantifying the long-speculated contribution of tropical cyclones to enhance ocean primary production. In July 2000, moderate cyclone Kai-Tak passed over the South China Sea (SCS). During its short 3-day stay, Kai-Tak triggered an average 30-fold increase in surface chlorophyll-a concentration. The estimated carbon fixation resulting from this event alone is 0.8 Mt, or 2–4% of SCS’s annual new production. Given an average of 14 cyclones passing over the SCS annually, we suggest the long-neglected contribution of tropical cyclones to SCS’s annual new production may be as much as 20–30%. INDEX TERMS: 4275 Oceanography: General: Remote sensing and electromagnetic processes (0689); 4805 Oceanography: Biological and Chemical: Biogeochemical cycles (1615); 0315 Atmospheric Composition and Structure: Biosphere/ atmosphere interactions; 4504 Oceanography: Physical: Air/sea interactions (0312); 1615 Global Change: Biogeochemical processes (4805).

Low Atlantic hurricane activity in the 1970s and 1980s compared to the past 270 years

Nyberg, J., B. A. Malmgren, A. Winter, M. R.
Jury, K. H. Kilbourne, and T. M. Quinn
(2007), Low Atlantic hurricane activity in the
1970s and 1980s compared to the past 270
years, Nature, 447, 698–701.

Abstract: 
Hurricane activity in the North Atlantic Ocean has increased significantly since 1995 (refs 1, 2). This trend has been attributed to both anthropogenically induced climate change3 and natural variability1, but the primary cause remains uncertain. Changes in the frequency and intensity of hurricanes in the past can provide insights into the factors that influence hurricane activity, but reliable observations of hurricane activity in the North Atlantic only cover the past few decades2. Here we construct a record of the frequency of major Atlantic hurricanes over the past 270 years using proxy records of vertical wind shear and sea surface temperature (the main controls on the formation of major hurricanes in this region1,3–5) from corals and a marine sediment core. The record indicates that the average frequency of major hurricanes decreased gradually from the 1760s until the early 1990s, reaching anomalously low values during the 1970s and 1980s. Furthermore, the phase of enhanced hurricane activity since 1995 is not unusual compared to other periods of high hurricane activity in the record and thus appears to represent a recovery to normal hurricane activity, rather than a direct response to increasing sea surface temperature. Comparison of the record with a reconstruction of vertical wind shear indicates that variability in this parameter primarily controlled the frequency of major hurricanes in the Atlantic over the past 270 years, suggesting that changes in the magnitude of vertical wind shear will have a significant influence on future hurricane activity.

Atlantic Subtropical Storms. Part II: Climatology

Guishard, Mark P., Jenni L. Evans, Robert E. Hart, 2009: Atlantic Subtropical Storms. Part II: Climatology. J. Climate, 22, 3574–3594.
doi: 10.1175/2008JCLI2346.1

Abstract: 
A 45-yr climatology of subtropical cyclones (ST) for the North Atlantic is presented and analyzed. The STs pose a warm-season forecasting problem for subtropical locations such as Bermuda and the southern United States because of the potentially rapid onset of gale-force winds close to land. Criteria for identification of ST have been developed based on an accompanying case-study analysis. These criteria are applied here to the 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40) to construct a consistent historical database of 197 North Atlantic ST in 45 yr. Because ST may eventually evolve into tropical cyclones, sea surface temperatures (SST) and vertical wind shear conditions for tropical cyclogenesis are contrasted with the conditions for ST genesis identified here. Around 60% of the 197 ST formed over SST in excess of 258C in a region of weak static stability. Further, the mean environmental vertical wind shear at formation for these storms is 10.7 m s21, a magnitude generally considered to be unfavorable for tropical cyclogenesis. The STs have hybrid structure, so the potential for baroclinic and thermodynamic development is explored through the baroclinic zone (characterized by the Eady growth rate s) and SST field. Seasonal evolution in the location and frequency of ST formation in the basin is demonstrated to correspond well to the changing region of overlap between SST . 258C and s . 0.1 day21. This climatology is contrasted with two alternative ST datasets. The STs contribute to 12% of tropical cyclones (TC) in the current National Hurricane Center (NHC) Hurricane Database (HURDAT); this equivalent to about 1 in 8 genesis events from an incipient ST disturbance. However, with the addition of 144 ST that are newly identified in this climatology (and not presently in HURDAT) and the reclassification (as not ST) of 65 existing storms in HURDAT, 197/597 storms (33%) in the newly combined database are ST, which emphasizes the potential importance of these warm-season storms.

Meteorological Impacts of Land Use Change in the Maritime Tropics

Abstract: 
The island Puerto Rico is the smallest of the Greater Antilles. Measuring roughly 180 x 60 km, it is situated in the eastern Caribbean at 18o15’N and 66o30’W (figure 1.1). Apart from the coastal plains on the north and south coast, the island is mountainous, with the highest peaks in the central and north-eastern part of the island rising to elevations of 1000-1300 ma:s:l: (figure 1.2).

An assessment of climate change in the Luquillo Mountains of Puerto Rico.

Scatena, F. N. 1998. An assessment of climate change in the Luquillo Mountains of Puerto Rico. . In: Segarra-García, R. I., editor. Proceeding tropical hydrology and Caribbean water resources, Third international symposium on tropical hydrology and Fifth Caribbean Islands water resources congress; San Juan, Puerto Rico. Herndon, VA: American Water Resources Association; :193-198.

Abstract: 
Change in the surface temperature of the coastal plain of 1 to 2C and/or a 11 to 33% change in annual rainfall could dramatically alter the distribution of forest vegetation within the Luquillo Experimental Forest(LEF) of northeastern Puerto Rico.

Physical Aspects of Hurricane Hugo in Puerto Rico

Scatena, F. N., and Larsen, M. C., 1991, Physical aspects of Hurricane Hugo in Puerto Rico: Biotropica, v. 23, no. 4A, p. 317-323.

Abstract: 
On 18 September 1989, the western portion of Hurricane Hugo crossed eastern Puerto Rico and the Luquillo Experimental Forest (LEF). Storm-facing slopes on the northeastern part of the island that were within 15 km of the eye and received greater than 200 mm of rain were most affected by the storm. In the LEF and nearby area, recurrence intervals associated with Hurricane Hugo were 50 yr for wind velocity, 10 to 31 yr for stream discharge, and 5 yr for rainfall intensity. To compare the magnitudes of the six hurricanes to pass over Puerto Rico since 1899, 3 indices were developed using the standardized values of the product of: the maximum sustained wind speed at San Juan squared and storm duration; the square of the product of the maximum sustained wind velocity at San Juan and the ratio of the distance between the hurricane eye and San Juan to the distance between the eye and percentage of average annual rainfall delivered by the storm. Based on these indices, Hurricane Hugo was of moderate intensity. However, because of the path of Hurricane Hugo, only one of these six storms (the 1932 storm) caused more damage to the LEF than Hurricane Hugo. Hurricanes of Hugo's magnitude are estimated to pass over the LEF once every 50-60 years on average.

STRUCTURAL AND FUNCTIONAL RESPONSES OF A SUBTROPICAL FOREST TO 10 YEARS OF HURRICANES AND DROUGHTS

Beard, Karen H., Kristiina A. Vogt, Daniel J. Vogt, Frederick N. Scatena, Alan P. Covich, Ragnhildur Sigurdardottir, Thomas G. Siccama, and Todd A. Crowl. 2005. STRUCTURAL AND FUNCTIONAL RESPONSES OF A SUBTROPICAL FOREST TO 10 YEARS OF HURRICANES AND DROUGHTS. Ecological Monographs 75:345–361. [doi:10.1890/04-1114]

Abstract: 
Little is known about ecosystem-level responses to multiple, climatic disturbance events. In the subtropical forests of Puerto Rico, the major natural disturbances are hurricanes and droughts. We tested the ecosystem-level effects of these disturbances in sites with different land use histories. From 1989 to 1992, data were collected to determine the effects of Hurricane Hugo and two droughts on litterfall inputs, fine-root biomass, and decomposition rates in three topographic locations (stream, riparian, upslope) within two watersheds. From 1994 to 1998, we added a third watershed and an experiment in which coarse-wood levels were manipulated to simulate hurricane inputs. Data were collected on tree and palm growth rates, litterfall inputs, fine-root biomass, and decomposition rates. From 1994 to 1998, four hurricanes and three droughts were recorded. Measured parameters had unique responses and recovery rates to hurricanes and droughts. Litterfall inputs returned to long-term mean rates within one month following droughts and small-to-moderate hurricanes but required five years to recover after an intense hurricane. In contrast, fine-root biomass recovered seven months after an intense hurricane but failed to recover after five years following a severe drought. Despite the dramatic effects of these weather events on some ecosystem parameters, we found that aboveground measures of tree and palm growth were more affected by preexisting site conditions (e.g., nitrogen availability due to past land use activities) than hurricanes or droughts. The addition of coarse woody debris increased tree and palm growth, fine-root biomass, and litter production; however, in the case of tree and palm growth, this effect was least measurable in the sites with the highest productivity. We found that decomposition rates were more controlled by litter quality than weather conditions. In conclusion, we found that certain ecosystem structures (e.g., canopy structure and fine-root biomass) generally recovered more slowly from disturbance events than certain ecosystem processes (e.g., plant growth rates, decomposition rates). We also found that past land use activities and disturbance legacies were important in determining the responses and recovery rates of the ecosystem to disturbance.
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