The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
L Lange - One of the best experts on this subject based on the ideXlab platform.
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transport of biomass burning smoke to the upper troposphere by deep convection in the Equatorial Region
Geophysical Research Letters, 2001Co-Authors: M O Andreae, Paulo Artaxo, H Fischer, S R Freitas, J M Gregoire, A Hansel, P Hoor, R Kormann, Radovan Krejci, L LangeAbstract:During LBA-CLAIRE-98, we found atmospheric layers with aged biomass smoke at altitudes >10 km over Suriname. CO, CO2, acetonitrile, methyl chloride, hydrocarbons, NO, O3, and aerosols were strongly enhanced in these layers. We estimate that 80-95% of accumulation mode aerosols had been removed during convective transport. Trajectories show that the plumes originated from large fires near the Brazil/Venezuela border during March 1998. This smoke was entrained into deep convection over the northern Amazon, transported out over the Pacific, and then returned to South America by the circulation around a large upper-level anticyclone. Our observations provide evidence for the importance of deep convection in the Equatorial Region as a mechanism to transport large amounts of pyrogenic pollutants into the upper troposphere. The entrainment of biomass smoke into tropical convective clouds may have significant effects on cloud microphysics and climate dynamics.
Jay R Johnson - One of the best experts on this subject based on the ideXlab platform.
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effects of heavy ions on ulf wave resonances near the Equatorial Region
Journal of Geophysical Research, 2008Co-Authors: Jay R JohnsonAbstract:[1] Pc1-2 ULF waves are strongly associated with the presence of various ions in the magnetosphere. We investigate the role of heavy ion resonances in nonuniform plasmas near the Equatorial Region. By adopting the invariant imbedding method, the coupled plasma wave equations are solved in an exact manner to calculate the resonant absorption at the ion-ion hybrid resonance. Our results show that irreversible mode conversion occurs at the resonance, which absorbs the fast wave energy. It is found that waves near the resonances appear with linear polarization, and their amplitude and frequency are sensitive to the properties of the heavy ion plasma composition. We examine how these resonances occur for various H+-He+ populations in detail by performing an accurate calculation of the mode conversion efficiency. Because the multi-ion hybrid resonance locations in cold plasmas are determined by simple parameters, such as the fraction of the ion number density of each species and the magnetic field, we suggest that it is possible to monitor heavy ion composition by examining the peak frequencies of linearly polarized wave events in either electric field or magnetic field spectral data.
M O Andreae - One of the best experts on this subject based on the ideXlab platform.
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transport of biomass burning smoke to the upper troposphere by deep convection in the Equatorial Region
Geophysical Research Letters, 2001Co-Authors: M O Andreae, Paulo Artaxo, H Fischer, S R Freitas, J M Gregoire, A Hansel, P Hoor, R Kormann, Radovan Krejci, L LangeAbstract:During LBA-CLAIRE-98, we found atmospheric layers with aged biomass smoke at altitudes >10 km over Suriname. CO, CO2, acetonitrile, methyl chloride, hydrocarbons, NO, O3, and aerosols were strongly enhanced in these layers. We estimate that 80-95% of accumulation mode aerosols had been removed during convective transport. Trajectories show that the plumes originated from large fires near the Brazil/Venezuela border during March 1998. This smoke was entrained into deep convection over the northern Amazon, transported out over the Pacific, and then returned to South America by the circulation around a large upper-level anticyclone. Our observations provide evidence for the importance of deep convection in the Equatorial Region as a mechanism to transport large amounts of pyrogenic pollutants into the upper troposphere. The entrainment of biomass smoke into tropical convective clouds may have significant effects on cloud microphysics and climate dynamics.
Tsutomu Nagatsuma - One of the best experts on this subject based on the ideXlab platform.
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comparison of observed tec values with iri 2007 tec and iri 2007 tec with optional fof2 measurements predictions at an Equatorial Region chumphon thailand
Advances in Space Research, 2013Co-Authors: Prasert Kenpankho, Pornchai Supnithi, Tsutomu NagatsumaAbstract:Abstract In this research, as part of working towards improving the IRI over Equatorial Region, the total electron content (TEC) derived from GPS measurements and IRI-2007 TEC predictions at Chumphon station (10.72°N, 99.37°E), Thailand, during 2004–2006 is analyzed. The seasonal variation of the IRI-2007 TEC predictions is compared with the TEC from the IRI-2007 TEC model with the option of the actual F2 plasma frequency (foF2) measurements as well as the TEC from the GPS and International GNSS service (IGS). The Chumphon station is located at the Equatorial Region and the low latitude of 3.22°N. For a declining phase of the solar cycle (2004–2006), the study shows that the IRI-2007 TEC underestimates the IRI-2007 TEC with the foF2 observation at the nighttime by about 5 TECU. The maximum differences are about 15 TECU during daytime and 5 TECU during nighttime. The overestimation is more evident at daytime than at nighttime. When compared in terms of the root-mean square error (RMSE), we find that the highest RMSE between GPS TEC and IRI 2007 TEC is 14.840 TECU at 1230 LT in 2004 and the lowest average between them is 1.318 TECU at 0630 LT in 2006. The noon bite-out phenomena are clearly seen in the IRI-2007 TEC with and without optional foF2 measurements, but not on the GPS TEC and IGS TEC. The IRI TEC with optional foF2 measurements gives the lowest RMSE values between IRI TEC predicted and TEC measurement. However, the TEC measurements (GPS TEC and IGS TEC) are more correct to use at Chumphon station.
K. Parameswaran - One of the best experts on this subject based on the ideXlab platform.
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Mean structure of the tropical tropopause and its variability over the Indian longitude sector
Climate Dynamics, 2013Co-Authors: S. V. Sunilkumar, Asha Babu, K. ParameswaranAbstract:The mean spatiotemporal variations in tropopause parameters over the tropics (±35°, in latitude) in the Indian monsoon Region are examined using the upper air data for an extended period obtained from radiosonde and Radio Occultation measurements. In general, the altitude of cold point tropopause (CPT) is a minimum near the equator and increases with latitude on either side. While CPT over the entire southern tropical latitudes and northern Equatorial Region is cooler (higher) during boreal winter and warmer (lower) during boreal summer, the annual pattern of CPT-temperature reverses in the northern hemispheric off-Equatorial Region. The temperature of lapse rate tropopause (LRT) is always negatively correlated with its altitude. While the annual variation of LRT-temperature in tropics is always positively correlated with CPT-temperature, the annual variation of LRT-altitude differs mainly in the off-Equatorial Regions. While the altitude of the convective tropopause is positively correlated with CPT-altitude over the latitude Region 20°S–5°N, they are negatively correlated at the north of 10°N. In general, the tropical tropopause layer (TTL) is very thin (~3 km) near the equator and its thickness increases with latitude on either side of the equator to reach a peak value (of ~6 km) around ±30°. A pronounced decrease in TTL-thickness observed over the northern off-Equatorial Region during the ASM period can be attributed to the manifestation of very deep convection over the land near the Head Bay-of-Bengal Region. The TTL-lapse-rate (γ_TTL) is large in the Equatorial Region and decreases with increase in latitude. While γ_TTL in the northern hemispheric off-Equatorial Region is low during winter, it increases and becomes comparable to that over Equatorial Region during the ASM period. The annual variations in CPT parameters as well as the TTL- thickness are significantly modulated by quasi-biennial oscillation and the El Niño Southern Oscillation.