Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
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.
Revisiting the Climatology of Atmospheric Blocking in the Northern Hemisphere

Ho Nam CHEUNG,ZHOU Wen,Hing Yim MOK,Man Chi WU,Yaping SHAO,

大气科学进展 , 2013,
Abstract: In addition to the occurrence of atmospheric blocking, the climatology of the characteristics of blocking events, including duration, intensity, and extension, in four seasons over the Northern Hemisphere was analyzed for the period 1950–2009. The seasonality and spatial variations of these characteristics were studied according to their longitudinal distributions. In general, there were sharp discrepancies in the blocking characteristics between winter and summer, and these differences were more prominent over the Atlantic and Pacific Oceans. The blocking not only occurred more frequently but also underwent stronger amplification in winter; likewise, the blocking occurred less frequently and underwent weaker amplification in summer. There are very strong interrelationships among different blocking characteristics, suggesting that they are supported by similar physical factors. In addition, the relationship between blocking over different regions and East Asian circulation was examined. Ural-Siberia is a major blocking formation region in all seasons that may exert a downstream impact on East Asia. The impact is generally weak in summer, which is due to its lower intensity and smaller duration. However, the extratropical circulation over East Asia in summer can be disturbed persistently by the frequent occurrence of blocking over the Asian continent or the Western Pacific. In particular, the blocking frequency over the Western Pacific significantly increased during the study period. This climatological information provides a background for studying the impact of blocking on East Asian circulation under both present and future climate conditions.
Climatology of extratropical atmospheric wave packets in the northern hemisphere  [PDF]
Federico Grazzini,Valerio Lucarini
Physics , 2010,
Abstract: Planetary and synoptic scale wave-packets represent one important component of the atmospheric large-scale circulation. These dissipative structures are able to rapidly transport eddy kinetic energy, generated locally (e.g. by baroclinic conversion), downstream along the upper tropospheric flow. The transported energy, moving faster than individual weather systems, will affect the development of the next meteorological system on the leading edge of the wave packet, creating a chain of connections between systems that can be far apart in time and space, with important implications on predictability. In this work we present an automated recognition of atmospheric wave packets which allows the extraction of all the relevant properties, such as location, duration and velocity. Behind this tool lies the need to investigate atmospheric variability in its full complexity, bridging the low-frequency steady-state approach with the storm-tracks lagrangian approach. We have applied the algorithm to the daily analysis (every 12h) from 1958-2010, building an extended climatology of waves packets with different spectral properties. We show that wave packets characteristics over Northern Hemisphere exhibit a strong seasonal dependence, both in their spectral component and in their distribution and localization. The maximum activity is reached in the cold months, from autumn to spring, with a slight weakening in mid-winter and a clear minimum of activity in summer. Preferential areas of genesis are shown to be the Western and Central-Pacific and Western-Atlantic while areas of lyses are the eastern borders of Pacific and Atlantic. We envisage possible applications of this algorithm also for predictability studies and operational activities.
Tropospheric ozone climatology at two Southern Hemisphere tropical/subtropical sites, (Reunion Island and Irene, South Africa) from ozonesondes, LIDAR, and in situ aircraft measurements
G. Clain, J. L. Baray, R. Delmas, R. Diab, J. Leclair de Bellevue, P. Keckhut, F. Posny, J. M. Metzger,J. P. Cammas
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2009,
Abstract: This paper presents a climatology and trends of tropospheric ozone in the Southwestern Indian Ocean (Reunion Island) and South Africa (Irene and Johannesburg). This study is based on a multi-instrumental dataset: PTU-O3 ozonesondes, DIAL LIDAR and MOZAIC airborne instrumentation. The seasonal profiles of tropospheric ozone at Reunion Island have been calculated from two different data sets: ozonesondes and LIDAR. The two climatological profiles are similar, except in austral summer when the LIDAR profiles show greater values in the free troposphere, and in the upper troposphere when the LIDAR profiles show lower values during all seasons. These results show that the climatological value of LIDAR profiles must be discussed with care since LIDAR measurements can be performed only under clear sky conditions, and the upper limit of the profile depends on the signal strength. In addition, linear trends have been calculated from ozonesonde data at Reunion and Irene. Considering the whole tropospheric column, the trend is slightly positive for Reunion, and more clearly positive for Irene. Trend calculations have also been made separating the troposphere into three layers, and separating the dataset into seasons. Results show that the positive trend for Irene is governed by the lower layer that is affected by industrial pollution and biomass burning. On the contrary, for Reunion Island, the strongest trends are observed in the upper troposphere, and in winter when stratosphere-troposphere exchange is more frequently expected.
A Comparison of Southern Hemisphere Cyclone Track Climatology and Interannual Variability in Coarse-Gridded Reanalysis Datasets  [PDF]
Timothy Paul Eichler,Jon Gottschalck
Advances in Meteorology , 2013, DOI: 10.1155/2013/891260
Abstract: Southern Hemisphere (SH) extratropical cyclones have received less study than their Northern Hemisphere (NH) counterparts. Generating SH cyclone tracks from global reanalysis datasets is problematic due to data reliability, especially prior to 1979. It is therefore prudent to compare the climatology and variability of SH cyclone tracks from different reanalysis datasets. We generate cyclone track frequency and intensity climatologies from three reanalysis datasets: The National Center for Environmental Prediction’s Reanalysis I and Reanalysis II datasets and the European Centre for Medium Range Weather Forecasts ERA-40 dataset. Our results show that ERA-40 produces more intense cyclones in the SH active cyclone region compared to NCEP reanalyses. More intense storms are also found in the SH active cyclone region in NCEP reanalyses data post-1979 reflecting the positive trend in the AAO in the past few decades. When evaluating interannual variability, our results show Rossby wave trains including the Pacific South American (PSA) and the East Indian Ocean pattern in response to anomalous heating linked to El Ni?o and the Indian Ocean Dipole (IOD), respectively. Response to the AAO shows a robust annular structure for cyclone track frequency, but not intensity suggesting a weak relationship between cyclone frequency and cyclone intensity. 1. Introduction Extratropical cyclones are an important manifestation of the Southern Hemisphere (SH) general circulation and are associated with serious socioeconomic impacts. For example, the economic costs associated with coastal cyclones in South Africa are quite large as demonstrated by infrastructure costs associated with a 2007 cyclone that resulted in R100 million along the Durban coast [1]. While cyclone tracks for the SH have been less studied than the NH, several studies have been conducted. These include those that detect cyclones in the upper levels (e.g., 300?hPa, 500?hPa) using band-passed or high-pass filtered data (e.g., Trenberth [2], J. S. Frederiksen and C. S. Frederiksen [3], Kidson and Sinclair [4], C. S. Frederiksen and J. S. Frederiksen [5], Berbery and Vera [6], Rao et al. [7], Inatsu and Hoskins [8], Nakamura and Shimpo [9], Solman and Menéndez [10], Ashok et al. [11], and Carmo and de Souza [12]). Other studies use a Lagrangian method to determine cyclones from the low levels (e.g., sea level pressure (SLP)) such as Lim and Simmonds [13], Pezza et al. [14], Pezza et al. [15], Mendes et al. [16], and Yuan et al. [17]. Hoskins and Hodges [18] utilized both Eularian and Lagrangian methods in their
New dynamic NNORSY ozone profile climatology
A. K. Kaifel,M. Felder,C. DeClercq,J.-C. Lambert
Atmospheric Measurement Techniques Discussions , 2012, DOI: 10.5194/amtd-5-775-2012
Abstract: Climatological ozone profile data are widely used as a-priori information for total ozone using DOAS type retrievals as well as for ozone profile retrieval using optimal estimation, for data assimilation or evaluation of 3-D chemistry-transport models and a lot of other applications in atmospheric sciences and remote sensing. For most applications it is important that the climatology represents not only long term mean values but also the links between ozone and dynamic input parameters. These dynamic input parameters should be easily accessible from auxiliary datasets or easily measureable, and obviously should have a high correlation with ozone. For ozone profile these parameters are mainly total ozone column and temperature profile data. This was the outcome of a user consultation carried out in the framework of developing a new, dynamic ozone profile climatology. The new ozone profile climatology is based on the Neural Network Ozone Retrieval System (NNORSY) widely used for ozone profile retrieval from UV and IR satellite sounder data. NNORSY allows implicit modelling of any non-linear correspondence between input parameters (predictors) and ozone profile target vector. This paper presents the approach, setup and validation of a new family of ozone profile climatologies with static as well as dynamic input parameters (total ozone and temperature profile). The neural network training relies on ozone profile measurement data of well known quality provided by ground based (ozonesondes) and satellite based (SAGE II, HALOE, and POAM-III) measurements over the years 1995–2007. In total, four different combinations (modes) for input parameters (date, geolocation, total ozone column and temperature profile) are available. The geophysical validation spans from pole to pole using independent ozonesonde, lidar and satellite data (ACE-FTS, AURA-MLS) for individual and time series comparisons as well as for analysing the vertical and meridian structure of different modes of the NNORSY ozone profile climatology. The NNORSY ozone profile climatology is available to the community as a comprehensive software library.
Estonian total ozone climatology  [PDF]
K. Eerme,U. Veismann,R. Koppel
Annales Geophysicae (ANGEO) , 2003,
Abstract: The climatological characteristics of total ozone over Estonia based on the Total Ozone Mapping Spectrometer (TOMS) data are discussed. The mean annual cycle during 1979–2000 for the site at 58.3° N and 26.5° E is compiled. The available ground-level data interpolated before TOMS, have been used for trend detection. During the last two decades, the quasi-biennial oscillation (QBO) corrected systematic decrease of total ozone from February–April was 3 ± 2.6% per decade. Before 1980, a spring decrease was not detectable. No decreasing trend was found in either the late autumn ozone minimum or in the summer total ozone. The QBO related signal in the spring total ozone has an amplitude of ± 20 DU and phase lag of 20 months. Between 1987–1992, the lagged covariance between the Singapore wind and the studied total ozone was weak. The spring (April–May) and summer (June–August) total ozone have the best correlation (coefficient 0.7) in the yearly cycle. The correlation between the May and August total ozone is higher than the one between the other summer months. Seasonal power spectra of the total ozone variance show preferred periods with an over 95% significance level. Since 1986, during the winter/spring, the contribution period of 32 days prevails instead of the earlier dominating 26 days. The spectral densities of the periods from 4 days to 2 weeks exhibit high interannual variability. Key words. Atmospheric composition and structure (middle atmosphere – composition and chemistry; volcanic effects) – Meteorology and atmospheric dynamics (climatology)
Air temperature was associated with ambulance transports in Osaka area, Japan  [PDF]
Nobuyuki Miyatake, Noriko Sakano, Shoko Murakami, Takeshi Suzue, Takeshi Yoda, Akira Yoshioka, Tomohiro Hirao
Health (Health) , 2011, DOI: 10.4236/health.2011.39092
Abstract: We investigated the link between ambulance transports and meteorological parameters of summer by using daily data in Osaka area, Japan. Daily observations for ambulance transports (from July 1 to September 30, 2009) were obtained from Fire Department Service in Osaka. Data of meteorological parameters in Osaka area, Japan (from July 1 to September 30, 2009) were also obtained from Japan Meteorological Agency. Effect of meteorological parameters on ambulance transports was analyzed. A total of 49,526 ambulance transports were observed from July 1 to September 30, 2009 in Osaka, Japan. Ambulance transports were significantly correlated with mean air temperature (r = 0.298), the highest air temperature (r = 0.347), the lowest air temperature (r = 0.209) and daylight hours (r = 0.301). The higher air temperature was associated with higher ambulance transports of summer in Osaka area, Japan.
Higher Temperatures Were Closely Associated with Higher Ambulance Transports in Takamatsu Area, Japan  [PDF]
Nobuyuki Miyatake, Masaki Nakao, Noriko Sakano, Shigeru Suna, Takeshi Suzue, Tomohiro Hirao
Journal of Environmental Protection (JEP) , 2011, DOI: 10.4236/jep.2011.21007
Abstract: The link between high temperatures and ambulance transports in Takamatsu area, Japan was investigated. Monthly observations for ambulance transports (2004-2008) were obtained from Fire Department Service in Takamatsu. Data of temperatures in Takamatsu area, Japan (2004-2008) were used by Japan Meteorological Agency. Effect of high temperatures on ambulance transports was analyzed. By using data from July to September, there were not clear differences of mean temperatures and ambulance transports among years. Ambulance transports were significantly correlated with parameters of temperatures. Correlation coefficient rate between ambulance transports and the mean temperature of maximum temperatures in a month was highest among parameters (r = 0.738, p = 0.0017). In addition, ambulance transports were also significantly correlated with the number of days over the level of 32?C in a month (r = 0.782, p = 0.0006). Higher temperatures were closely associated with higher ambulance transports in Takamatsu area, Japan.
The relation between ambulance transports due to heat stroke and air temperature using daily data in Okayama prefecture, Japan  [PDF]
Nobuyuki Miyatake, Shoko Murakami, Noriko Sakano
Open Journal of Preventive Medicine (OJPM) , 2012, DOI: 10.4236/ojpm.2012.21016
Abstract: The aim of this study was to investigate the link between ambulance transports due to heat stroke and air temperature by using daily data of ambulance transports in Okayama prefecture, Japan. Daily observations for ambulance transports due to heat stroke from July to September in 2010 in Okayama prefecture, Japan were obtained from Fire and Disaster Management Agency in Japan. Data of meteorological parameters in Okayama prefecture, Japan were also obtained from Japan Meteorological Agency. Effect of meteorological parameters on ambulance transports due to heat stroke was analyzed. A total of 1133 ambulance transports due to heat stroke were observed in from July to September of 2010 in Okayama prefecture, Japan. Ambulance transports due to heat stroke was significantly correlated with air temperature. In addition, number of subjects with ambulance transports due to heat stroke over 34°C in the highest air temperature was 21.2 ± 9.8 per day. Higher air temperature was closely associated with higher ambulance transports due to heat stroke by using daily data in Okayama, prefecture, Japan.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.