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Search Results: 1 - 10 of 403481 matches for " J.-H. May "
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The Río Parapetí – Holocene megafan formation in the southernmost Amazon basin
J.-H. May
Geographica Helvetica (GH) , 2012,
Abstract: No abstract available.
Review of past and recent fluvial dynamics in the Beni lowlands, NE Bolivia
A. Plotzki, J.-H. May,H. Veit
Geographica Helvetica (GH) , 2012,
Abstract: No abstract available.
Existence of Solutions of Nonlinear Stochastic Volterra Fredholm Integral Equations of Mixed Type
K. Balachandran,J.-H. Kim
International Journal of Mathematics and Mathematical Sciences , 2010, DOI: 10.1155/2010/603819
Abstract: We establish sufficient conditions for the existence anduniqueness of random solutions of nonlinear Volterra-Fredholm stochastic integralequations of mixed type by using admissibility theory and fixed point theorems. Theresults obtained in this paper generalize the results of several papers.
On solutions of general nonlinear stochastic integral equations
K. Balachandran,J.-H. Kim
International Journal of Stochastic Analysis , 2006, DOI: 10.1155/jamsa/2006/45979
Abstract: We study the existence, uniqueness, and stability of random solutions of a general class of nonlinear stochastic integral equations by using the Banach fixed point theorem. The results obtained in this paper generalize the results of Szynal and Wędrychowicz (1993).
Space-borne observations link the tropical atlantic ozone maximum and paradox to lightning
G. S. Jenkins ,J.-H. Ryu
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2004,
Abstract: The potential enhancement of tropospheric column ozone values over the Tropical Atlantic Ocean on a seasonal basis by lightning is investigated using satellite derived ozone data, TRMM lightning data, ozonesonde data and NCEP reanalysis during 1998-2001. Our results show that the number of lightning flashes in Africa and South America reach a maximum during September, October and November (SON). The spatial patterns of winds in combination with lightning from West Africa, Central Africa and South America is likely responsible for enriching middle/upper troposphere ozone over the Tropical South Atlantic during SON. Moreover, lightning flashes are high in the hemisphere opposite to biomass burning during December, January, and February (DJF) and June, July and August (JJA). This pattern leads to an enrichment of ozone in the middle/upper troposphere in the Southern Hemisphere Tropics during DJF and the Northern Hemisphere Tropics during JJA. During JJA the largest numbers of lightning flashes are observed in West Africa, enriching tropospheric column ozone to the north of 5S in the absence of biomass burning. During DJF, lightning is concentrated in South America and Central Africa enriching tropospheric column ozone south of the Equator in the absence of biomass burning.
Linking horizontal and vertical transports of biomass fire emissionsto the tropical Atlantic ozone paradox during the Northern Hemisphere winter season: climatology
G. S. Jenkins ,J.-H. Ryu
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2004,
Abstract: During the Northern hemisphere winter season, biomass burning is widespread in West Africa, yet the total tropospheric column ozone values (<30DU) over much of the Tropical Atlantic Ocean (15°N-5°S) are relatively low. At the same time, the tropospheric column ozone values in the Southern Tropical Atlantic are higher than those in the Northern Hemisphere (ozone paradox). We examine the causes for low tropospheric column ozone values by considering the horizontal and vertical transport of biomass fire emissions in West Africa during November through March, using observed data which characterizes fires, aerosols, horizontal winds, precipitation, lightning and outgoing longwave radiation. We have found that easterly winds prevail in the lower troposphere but transition to westerly winds at pressure levels lower than 500hPa. A persistent anticyclone over West Africa at 700hPa is responsible for strong easterly winds, which causes a net outflow of ozone/ozone precursors from biomass burning in West Africa across the Atlantic Ocean towards South America. The lowest outgoing longwave radiation (OLR) and highest precipitation rates are generally found over the central Atlantic, some distance downstream of fires in West Africa making the vertical transport of ozone and ozone precursors less likely and ozone destruction more likely. However, lightning over land areas in Central Africa and South America can lead to enhanced ozone levels in the upper troposphere especially over the Southern tropical Atlantic during the Northern Hemisphere winter season.
Linking horizontal and vertical transports of biomass fire emissions to the Tropical Atlantic Ozone Paradox during the Northern Hemisphere winter season: climatology
G. S. Jenkins,J.-H. Ryu
Atmospheric Chemistry and Physics Discussions , 2003,
Abstract: During the Northern hemisphere winter season, biomass burning is widespread in West Africa, yet the total tropospheric column ozone values (<30 DU) over much of the Tropical Atlantic Ocean (15° N–5° S) are relatively low. At the same time, the tropospheric column ozone values in the Southern Tropical Atlantic are higher than those in the Northern Hemisphere (ozone paradox). We examine the causes for low tropospheric column ozone values by considering the horizontal and vertical transport of biomass fire emissions in West Africa during November through March, using observed data which characterizes fires, aerosols, horizontal winds, precipitation, lightning and outgoing longwave radiation. We have found that easterly winds prevail in the lower troposphere but transition to westerly winds at pressure levels lower than 500 hPa. A persistent anticyclone over West Africa at 700 hPa is responsible for strong easterly winds, which causes a net outflow of ozone/ozone precursors from biomass burning in West Africa across the Atlantic Ocean towards South America. The lowest outgoing longwave radiation (OLR) and highest precipitation rates are generally found over the central Atlantic, some distance downstream of fires in West Africa making the vertical transport of ozone and ozone precursors less likely and ozone destruction more likely. However, lightning over land areas in Central Africa and South America can lead to enhanced ozone levels in the upper troposphere especially over the Southern tropical Atlantic during the Northern Hemisphere winter season.
Influence of the Asian monsoon on net ecosystem carbon exchange in two major ecosystems in Korea
H. Kwon, J. Kim, J. Hong,J.-H. Lim
Biogeosciences (BG) & Discussions (BGD) , 2010,
Abstract: Considering the feedback in radiation, temperature, and soil moisture with alterations in rainfall patterns, the influence of the changing monsoon on Net Ecosystem CO2 Exchange (NEE) can be critical to the estimation of carbon balance in Asia. In this paper, we examined CO2 fluxes measured by the eddy covariance method from 2004 to 2008 in two major ecosystems in the KoFlux sites in Korea, i.e., the Gwangneung Deciduous forest (GDK) and the Haenam Farmland (HFK). Our objectives were to identify the repeatability of the mid-season depression of NEE encountered at the two sites based on the single-year observation, and to further scrutinize its cause, effect, and interannual variability by using multi-year observations. In both GDK and HFK sites, the mid-season depression of NEE was reproduced each year but with different timing, magnitude, and mechanism. At the GDK site, a predominant factor causing the mid-season depression was a decreased solar radiation and the consequent reduction in Gross Primary Productivity (GPP) during the summer monsoon period. At the HFK site, however, the monsoonal effect was less pronounced and the apparent mid-season depression was mainly a result of the management practices such as cultivation of spring barley and rice transplantation. Other flux observation sites in East Asia also showed a decline in radiation but with a lesser degree during the monsoon season, resulting in less pronounced depression in NEE. In our study, the observed depressions in NEE caused both GDK and HFK sites to become a weaker carbon sink or even a source in the middle of the growing season. On average, the GDK site (with maximum leaf area index of ~5) was a weak carbon sink with NEE of 84 gC m 2 y 1. Despite about 20% larger GPP (of 1321 gC m 2y 1) in comparison with the GDK site, the HFK site (with maximum leaf area index of 3–4) was a weaker carbon sink with NEE of 58 gC m 2 y 1 because of greater ecosystem respiration (of 1263 gC m 2 y 1). These NEE values were near the low end of the ranges reported in the literature for similar ecosystems in mid-latitudes. With the projected trends of the extended length of monsoon with more intensive rainfalls in East Asia, the observed delicate coupling between carbon and hydrological cycles may turn these key ecosystems into carbon neutral.
Corrigendum to "Thirty thousand years of vegetation development and climate change in Angola (Ocean Drilling Program Site 1078)" published in Clim. Past, 4, 107–124, 2008
L. M. Dupont, H. Behling,J.-H. Kim
Climate of the Past (CP) & Discussions (CPD) , 2011,
Abstract: No abstract available.
Thirty thousand years of vegetation development and climate change in Angola (Ocean Drilling Program Site 1078)
L. M. Dupont, H. Behling,J.-H. Kim
Climate of the Past (CP) & Discussions (CPD) , 2008,
Abstract: ODP Site 1078 situated under the coast of Angola provides the first record of the vegetation history for Angola. The upper 11 m of the core covers the past 30 thousand years, which has been analysed palynologically in decadal to centennial resolution. Alkenone sea surface temperature estimates were analysed in centennial resolution. We studied sea surface temperatures and vegetation development during full glacial, deglacial, and interglacial conditions. During the glacial the vegetation in Angola was very open consisting of grass and heath lands, deserts and semi-deserts, which suggests a cool and dry climate. A change to warmer and more humid conditions is indicated by forest expansion starting in step with the earliest temperature rise in Antarctica, 22 thousand years ago. We infer that around the period of Heinrich Event 1, a northward excursion of the Angola Benguela Front and the Congo Air Boundary resulted in cool sea surface temperatures but rain forest remained present in the northern lowlands of Angola. Rain forest and dry forest area increase 15 thousand years ago. During the Holocene, dry forests and Miombo woodlands expanded. Also in Angola globally recognised climate changes at 8 thousand and 4 thousand years ago had an impact on the vegetation. During the past 2 thousand years, savannah vegetation became dominant.
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