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Artykuły w czasopismach na temat "Monsoon lows"
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KUMAR, J. RAJENDRA, i S. K. DASH. "Inter-annual and intra-seasonal variation of some characteristics of monsoon disturbances formed over the Bay". MAUSAM 50, nr 1 (17.12.2021): 55–62. http://dx.doi.org/10.54302/mausam.v50i1.1804.
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The characteristics of monsoon disturbances during drought and flood years for the period 1971-96 are studied to find out their inter-annual variations. Variations of some of the characteristics of monsoon disturbances formed over Bay during 1979-88, with respect to different monsoon conditions such as strong, weak and break monsoons, are also studied. The results show that monsoon disturbance days are higher during flood years than during drought years. Drought years are associated with higher chances of low pressure areas to intensity into depressions, less westward movement, more horizontal extent, intense pressure departure from normal in comparison with flood years. However, more monsoon disturbances tilt significantly during flood years. The rainfall associated with these disturbances is highly variable and does not depend on the density, horizontal and vertical extent of the individual system. More number of lows intensify into depressions during strong monsoon conditions compared to those of weak monsoon conditions. Lows and depressions during strong monsoons have more westward movement and longer life period. Generally, very few lows form during break monsoon and none of them intensify into depression. Hence, the presence of mid-tropospheric heating during strong and weak monsoons is essential for the formation of depression. Synoptic systems which abate break monsoon condition and re-establish normal monsoon are also discussed.
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KUMAR, J. RAJENDRA, V. THAPLIYAL i S. K. DASH. "Decadal and epochal variation of frequency and duration of monsoon disturbances and their secular relationship with rainfall over India". MAUSAM 55, nr 3 (19.01.2022): 397–408. http://dx.doi.org/10.54302/mausam.v55i3.1171.
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Decadal and epochal variation of frequency and duration of monsoon disturbances like low pressure areas (lows), depressions and Cyclonic Storms (CS) over Indian region are studied by using 110 years (1890-1999) data. No linearly decreasing/increasing trend is observed during 110 years period in any of their frequencies. However, epochal linearly decreasing/increasing trends are noticed in decadal frequencies or duration of different monsoon disturbances. Decadal frequencies of depressions, CS and depressions are decreasing from 1970-79, till recently ended decade of 1990-99. During recent decade, less than half of the total number of depressions and CS are formed compared with 1970-79. On the other hand, total number of lows are increasing significantly from 1960-69 to recent decade, when more than double the number of lows of 1960-69 are formed.
Since Indian Summer Monsoon Rainfall (ISMR) also shows interdecadal variation of below normal and above normal phases, variation of frequencies of different monsoon disturbances and their total durations are also examined in similar time scale to understand their relationship with interdecadal variation of ISMR. Stability and secular nature of these relationships are also examined based on their decadal and 10-year moving Correlation Coefficients (CC) for the period 1890-1999. Relationship of decadal anomaly of their frequencies with interdecadal variation of ISMR shows that number of depressions and CS, are higher than the normal during the above normal ISMR decades and less during the below normal decades of ISMR. Reverse is true for the number of lows. The decadal and 10-years moving CC between ISMR and frequencies of different monsoon disturbances and total monsoon disturbance days clearly show epochal variation of their relationship in interdecadal time scale with ISMR. Hence present study shows that secular variation of CC not only exists between ISMR and its various regional and global parameters used in long range forecast of ISMR but also between ISMR and its main synoptic features e.g., monsoon disturbances.
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BHADRAM, C. V. V. "A synoptic study of active and weak southwest monsoon over Andhra Pradesh". MAUSAM 54, nr 2 (1.04.2003): 385–92. http://dx.doi.org/10.54302/mausam.v54i2.1523.
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An attempt has been made in this study to identify the synoptic systems that cause active or vigorous monsoon conditions over the three meteorological sub-divisions of Andhra Pradesh using the data for the years 1986 to 2000. Despite significant decrease in the frequency of formation of monsoon depressions in recent years, monsoon performance is noticed to be very good. Monsoon lows and upper air cyclonic-circulations (cycirs) found to be the chief synoptic systems which activate the monsoon over the state. Typical cases of these synoptic situations are discussed.
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JENAMANI, RAJENDRA KUMAR, i S. K. DASH. "A study on the role of synoptic and semi-permanent features of Indian summer monsoon on it’s rainfall variations during different phases of El-Nino". MAUSAM 56, nr 4 (20.01.2022): 825–40. http://dx.doi.org/10.54302/mausam.v56i4.1038.
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Characteristics of different synoptic and semi-permanent features of Indian Summer Monsoon Rainfall (ISMR), such as monsoon disturbances (lows and depressions), monsoon trough and Tibetan anticyclone and duration of monsoon, are studied individually for different phases of El-Nino during the period 1960-98 to understand why during some El-Nino single events, ISMR was deficient while during other years, ISMR was on the positive side of normal or normal. This study examines cases of El-Nino double events with deficient and near deficient ISMR in one of the two years and in both the years respectively. The cases of deficient ISMR without any El-Nino are also discussed. Emphasis has been given on the effects of the synoptic and semi-permanent features on spatial variations of ISMR.
Results show that characteristics of synoptic and semi-permanent features were important for ISMR and these were responsible for producing normal or above normal ISMR during some years in spite of El-Nino such as 1997. Also in the absence of El-Nino, ISMR was deficient because of less number of days of monsoon trough, lows and depressions, and weak Tibetan anticyclone. The reverse happened during flood years when there was no La-Nina. Statistical analysis indicates very high correlation coefficients (CCs) of these synoptic and semi-permanent features with ISMR than those of SST of Nino-3 region. India received highest monsoon rainfall during 1961 because total number of days of intense monsoon disturbances and monsoon trough and the total duration of monsoon over India during the year was the highest. This study shows that monsoon disturbances and monsoon trough are the most important components of synoptic and semi-permanent features, which affected spatial variation of ISMR in 1965 and 1966 with deficient rainfall and in 1961 and 1994 with excess rainfall over a large part of India.
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RAJAMANI, S. "Energetics of the monsoon circulation over south Asia :Part -I Diabatic heating and the generation of available potential energy". MAUSAM 36, nr 1 (5.04.2022): 7–12. http://dx.doi.org/10.54302/mausam.v36i1.1573.
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Considering the monsoon circulation as the mean zonal flow with standing or stationary eddies (monsoon trough etc) and the transient eddies (monsoon depressions, lows etc) supermposed on it, diabatic heating and generation of available potential energy over south Asia have been computed for the typical monsoon month of July 1963, based on the computations of vertical velocity from omega-equation, and thermodynamic energy equation.
Regions of upward vertical velocity are found to be areas of good rainfall. Rate of monthly mean diabatic heating in the troposphere is of the order of 0.5 deg. C and is. higher at 500 and 300 mb levels than at lower levels. Positive generation of both zonal and standing eddy available potential energy is inferred.
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Haertel, Patrick, i William R. Boos. "Global association of the Madden-Julian Oscillation with monsoon lows and depressions". Geophysical Research Letters 44, nr 15 (14.08.2017): 8065–74. http://dx.doi.org/10.1002/2017gl073625.
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Koteswaram, P. "Upper level 'Lows' in low latitudes in the Indian Area during SW Monsoon season and 'Breaks' in the monsoon". MAUSAM 1, nr 2 (9.02.2022): 162–64. http://dx.doi.org/10.54302/mausam.v1i2.4559.
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MUKHERJEE, AK, i G. NATARAJAN. "Westward moving sea level low pressure systems in the south Bay of Bengal during southwest monsoon". MAUSAM 19, nr 3 (5.05.2022): 285–88. http://dx.doi.org/10.54302/mausam.v19i3.5325.
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The movement of low pressure systems from the east, across south Bay of Bengal and south Indian Peninsula, during July and August, when the southwest monsoon has established itself over India has been studied for a 20-year period from 1946 to 1965, Only well marked systems, which could be delineated on the sea level synoptic chart, are reported In the present paper, The characteristics of these systems and its relation with other systems breaks in southwest monsoon etc are discussed.
The effect of migratory lows on rainfall has been studied for Madras State, Kerala and coastal Mysore, While Madras gets good rain with scattered heavy to very heavy falls, the rainfall over the West Coast particularly in the northern parts, is comparatively less marked.
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Yanase, Wataru, Hiroshi Niino, Shun-ichi I. Watanabe, Kevin Hodges, Matthias Zahn, Thomas Spengler i Irina A. Gurvich. "Climatology of Polar Lows over the Sea of Japan Using the JRA-55 Reanalysis". Journal of Climate 29, nr 2 (7.01.2016): 419–37. http://dx.doi.org/10.1175/jcli-d-15-0291.1.
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Abstract Polar lows are intense meso-α-scale cyclones that develop over the oceans poleward of the main baroclinic zone. A number of previous studies have reported polar low formation over the Sea of Japan within the East Asian winter monsoon. To understand the climatology of polar lows over the Sea of Japan, a tracking algorithm for polar lows is applied to the recent JRA-55 reanalysis. The polar low tracking is applied to 36 cold seasons (October–March) from October 1979 to March 2015. The polar lows over the Sea of Japan reach their maximum intensity on the southeastern side of the midline between the Japanese islands and the Asian continent. Consistent with previous case studies, composite analysis demonstrates that the polar low development is associated with the enhanced northerly flow on the western side of a synoptic-scale extratropical cyclone, with the cold trough in the midtroposphere and with increased heat fluxes from the sea surface. Furthermore, the present climatological study has revealed two dominant directions of motion of the polar lows: southward and eastward. Southward-moving polar lows are steered by a strong northerly flow in the lower troposphere, which is enhanced on the western side of synoptic-scale extratropical cyclones, while the eastward-moving polar lows occur within a planetary-scale westerly flow in the midlatitudes. Thus, the direction of polar low motion reflects the difference in planetary- and synoptic-scale conditions.
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MOHAPATRA, M. "Relative contribution of synoptic systems to monsoon rainfall over Orissa". MAUSAM 58, nr 1 (26.11.2021): 17–32. http://dx.doi.org/10.54302/mausam.v58i1.1125.
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ABSTRACT. The low/depression over northwest (NW) Bay of Bengal is the largest contributor to seasonal monsoon rainfall over all stations in Orissa and Orissa as a whole. The Low Pressure Systems (LPS) and cyclonic circulation (cycir) extending upto 500 hPa level over NW Bay of Bengal alone contribute about 22% to the seasonal monsoon rainfall through about 12 days. The monsoon trough without any significant embedded systems over Orissa and adjoining regions contributes about 28% to seasonal rainfall through about 55 days. All types of LPS including low, depression and cyclonic storm yield maximum rainfall in their left forward (southwest) sectors. The maximum rainfall belt lies more southward due to a depression compared to that due to a low. The spatial distribution of rainfall due to cycir is less systematic. The interaction due to Eastern Ghat plays a significant role in spatial distribution of rainfall over western and eastern sides of the Eastern Ghat due to monsoon lows and depressions over Orissa and adjoining Bay and land regions. The orographic interaction due to Eastern Ghat with the cycirs over Orissa and adjoining Bay and land regions is significantly less leading to no significant difference in spatial distribution of rainfall over eastern and western sides of the Eastern Ghat.
Rozprawy doktorskie na temat "Monsoon lows"
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Carrillo, Cruz Carlos Mauricio. "North American Monsoon Variability from Paleoclimate Era to Climate Change Projection: A Multiple Dataset Perspective". Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/338900.
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In the southwestern United States, the North American monsoon (NAM) is the main driver of severe weather and accounts for nearly half the annual precipitation. How the monsoon has behaved in the past and how it will change in the future is a question of major importance for natural resource management and infrastructural planning. In this dissertation, I present the results of three studies that have investigated North American monsoon variability and change from the perspective of paleoclimate records, future climate change projections, and simulation of the low-frequency variability with the longest retrospective atmospheric reanalysis. In the first study, a monsoon-sensitive network of tree-ring chronologies is evaluated within its ability to reproduce NAM variability during the past four centuries. Matrix methods are used to detect the low-frequency spatiotemporal variability. The treering chronologies can reasonable characterizes the dominant modes of NAM climate variability. The monsoon tree-ring network is able to reproduce the interannual variability of cool and warm season precipitation, in a manner similar to the period of the instrumental record. Earlywood and latewood adjusted chronologies reveal low frequency climate variability at decadal and longer timescales that is beyond the ability of the instrumental record to temporally well resolve. This low-frequency climate variability seems to be part of a much larger cycle that coincides with the occurrence of multiyear persistent droughts. In the second study, we consider the modes of natural climate variability identified in the previous study to objectively assess the degree of physical uncertainty in climate change projections for NAM from Regional Climate Models (RCMs) used in the North American Regional Climate Change Assessment Program (NARCCAP). Climate change projection models are evaluated mainly on their ability to represent warm season driven by quasi-stationary Rossby wave trains and El Niño Southern Oscillation – Pacific Decadal Variability (ENSO-PDV). It is concluded that use of the NARCCAP model ensemble mean for NAM climate projections is probably not suitable. NARCCAP RCMs are largely a slave to their driving global models and their error in the specification of large-scale atmospheric circulation. Only one out of eight NARCCAP RCMs has a reasonable representation of the seasonal cycle of monsoon precipitation and ENSOdriven interannual variability in both the 20th and 21st centuries. No decadal variability was observed in any of the NARCCAP RCMs. In the third study, the low-frequency drought signal found with tree-ring chronologies is further explored within the framework of a regional climate modeling. Version 2 of the Twentieth-Century Reanalysis (DD-20CR) is dynamically downscaled over a contiguous U.S.-Mexico domain. Statistic analysis of the DD-20CR suggests that the low-frequency drought signal in the Southwest is driven by atmospheric circulation changes on global to continental scales that affect precipitation in Central American as well. DD-20CR reproduces the spatial patterns of precipitation associated with climate variability at decadal and longer timescales in a manner that compares well with observational records and tree-ring chronologies. Low-frequency climate variability is therefore likely responsible for the multiyear persistent droughts in the last four centuries, as independently evaluated from the tree-ring monsoon-sensitive network.
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Kehrwald, Natalie Marie. "Low-latitude Ice Cores and Freshwater Availability". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1245169721.
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Duong, Hai Thuan. "Observation of monsoon and typhoon-driven hydro-morphodynamics at a tropical low-tide terraced beach : a case study at Nha Trang, Vietnam". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30361.
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La majeure partie des côtes du Vietnam s'érode actuellement, un déséquilibre dans le bilan sédimentaire qui peut être causé par la surexploitation des sédiments fluviaux pour la construction, l'affaissement associé à la surexploitation des eaux souterraines, la surexploitation de la zone côtière, et peut-être aussi par une augmentation observée des typhons et de la mousson d'hiver. L'évaluation du bilan sédimentaire est nécessaire et nécessite une évaluation précise du transport des sédiments dans l'environnement côtier. Dans mon étude de doctorat, j'utilise deux systèmes de caméras à courte portée pour la surveillance des eaux littorales : une caméra terrestre pour l'observation de l'hydro-morphodynamique côtière à court, moyen et long terme et un drone pour la surveillance des événements à court terme. J'ai utilisé un système de caméra installé sur la plage de Nha Trang, au Viet Nam, du 05/2013 au 08/2016. Certains résultats sur les changements saisonniers et à court terme du littoral ont été analysés et publiés. Les profils transversaux, les positions du rivage et les caractéristiques des vagues (hauteur et période) extraits des données vidéo ont été étalonnés à l'aide de mesures in situ provenant de deux expériences sur le terrain et de mesures bathymétriques effectuées pendant le typhon de Haiyan. L'étude montre une évolution saisonnière marquée du littoral de Nha Trang. L'impact des typhons de catégorie 5 Nari et Haiyan sur le littoral est également dramatique avec des changements de 4 à 8 m dans chaque cas. Cependant, la reprise aux événements individuels est rapide. Nous avons également comparé l'effet des moussons d'hiver avec celui des tempêtes. Nos observations vidéo continues montrent pour la première fois que les épisodes de mousson de longue durée ont un impact plus persistant (phase de récupération de la plage plus longue) que les typhons. À l'aide d'un modèle d'équilibre riverain, nous estimons que c'est l'enveloppe des événements intrasaisonniers plutôt que la moyenne mensuelle des vagues qui détermine le comportement saisonnier du rivage. Enfin, l'étude suggère que l'interaction entre l'intensité et la durée des événements intrasaisonniers peut être d'une importance capitale. [...]Most of the coast of Vietnam is currently eroding, an imbalance in the sediment budget that may be caused by overuse of river sediments for construction, subsidence associated with overuse of groundwater, over-exploitation of the littoral zone (coastal squeeze), and possibly by an increase in typhoon frequency and winter monsoon events. Assessment of sediment budget is needed and requires accurate evaluation of sediment transport in the coastal environment. In my PhD study, I use two close-range camera systems for nearshore monitoring: a land-based nearshore camera system for observing short-, medium- and long-term coastal hydro-morphodynamics and a drone for monitoring short-term events. Specifically, I used a camera system installed in Nha Trang beach, Viet Nam, from 05/2013 to 08/2016. The cross-shore profiles, shoreline positions and wave characteristics (height and period) extracted from the video data are calibrated with in-situ measurement from two field experiments during the Haiyan typhoon event. Then, the results on short-term and seasonal shoreline changes are analyzed -- and published. The study shows a marked seasonal evolution of Nha Trang shoreline and dramatic impact of cat-5 typhoons Nari and Haiyan with changes of 4 to 8 m in each case. However, the recovery to individual events is fast, as opposed to the effect of winter monsoon events. Our continuous video observations show for the first time that long-lasting monsoon events have more persistent impact (longer beach recovery phase) than typhoons. Using a shoreline equilibrium model, we estimate that the envelope of intra-seasonal events rather than monthly-averaged waves drives the seasonal shoreline behavior. Finally, the shoreline study suggests that the interplay between intensity and duration of intra-seasonal events may be of key significance. In the second part of this PhD study, a video-based bathymetry inversion technique is applied to long-term data with varying wave environment from swell to wind wave conditions.[...]
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Guebsi, Ridha. "Impact de la vapeur d’eau et des aérosols désertiques sur le bilan radiatif et leurs contributions à l’intensification de la dépression thermique en Afrique de l’Ouest". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLV019/document.
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Ce travail vise à améliorer notre compréhension de l'impact radiatif des aérosols et de la vapeur d'eau sur la dynamique de la dépression thermique saharienne (Saharan heat low, SHL) en utilisant une combinaison d'observations spatiales (MODIS, OMI et CALIOP) ainsi que le modèle de transfert radiatif STREAMER. La variabilité saisonnière moyenne de l’épaisseur optique des aérosols (AOD) et du contenu intégré en vapeur d'eau (IWVC) sur le Sahara, moyenné sur les 11 dernières années, est bien corrélée avec l'évolution saisonnière du SHL. Après l'apparition de la SHL, l'IWVC augmente progressivement au dessus du Sahara tandis que l'AOD présente un maximum localisé en août, associé à la présence de systèmes convectifs profonds formant au-dessus des monts Hoggar.Pour estimer l'impact radiatif saisonnier de la vapeur d'eau et des aérosols désertiques, le modèle de transfert STREAMER a été utilisé pour calculer le budget radiatif mensuel net de mai à septembre. Des profils verticaux mensuels moyens de température et d'humidité obtenus à partir des analyses du Centre européen pour les prévisions météorologiques à moyen terme (ECMWF) et des profils de coefficients d'extinction dérivés de CALIOP sont utilisés comme paramètres d'entrée pour le calcul du modèle. Nos travaux montrent que le forçage des aérosols dans le Sud-Ouest du massif de Hoggar domine le budget net radiatif de surface, tandis que la vapeur d'eau est le joueur le plus fort en termes de forçage en ondes longues LW. Le forçage en ondes courtes SW et longues LW associé aux aérosols et à la vapeur d'eau, respectivement, contribue au réchauffement de la basse troposphère sur le Sahara pendant l'été (lorsque le SHL est au-dessus du Sahara). A son tour, ce chauffage intensifie la circulation cyclonique du SHL conduisant ainsi à renforcer l’advection de la vapeur d'eau vers le Sahara.Par conséquent, l'analyse des tendances décennales de la vapeur d'eau dans les tropiques et sous-tropiques est importante pour accroître la connaissance de la dynamique de la SHL, une caractéristique essentielle de la mousson ouest-africaine.Par ailleurs et pour la première fois, nous montrons l'impact de la variabilité saisonnière de la mousson africaine associée à la modulation de la latitude du front intertropicale (FIT), du jet de basse couche (LLJ), du vent meridional et zonal, de l’intensité et la position de la dépression thermique saharienne et du jet d’est Africain (EAJ) sur le soulèvement de la poussière sur les deux périodes juin 2006 et juin 2011, correspondant respectivement aux campagnes AMMA et FENNEC.This work aims at enhancing our understanding of the radiative impact of aerosols and water vapor on the dynamics of the Saharan Heat Low (SHL) using a combination of space-borne observations (MODIS, OMI, CALIOP) and a radiative transfer model (STREAMER). The mean seasonal variability of aerosol optical depth (AOD) and integrated water vapor content (IWVC) over the Sahara, averaged over the last 11 years, is found to be well correlated with the seasonal evolution of the SHL. After the onset of the SHL, the IWVC is observed to increase steadily over the Sahara while the AOD exhibits a localized maximum during August associated with the presence of deep convective systems forming over the Hoggar Mountains.To estimate the seasonal radiative impact of water vapor and desert aerosols, STREAMER was used to calculate the net monthly radiative budget from May to September. Average monthly temperature and humidity profiles obtained from the European center for medium range weather forecast (ECMWF) analyses and extinction coefficient profiles derived from CALIOP are used as input parameters for the model calculation.Our work shows that the aerosols forcing in the shortwave (SW) dominates the net surface radiative budget, while water vapor is the strongest player in terms of longwave (LW) forcing. The SW and LW forcing associated with aerosols and water vapor, respectively, contribute to heating the lower troposphere over the Sahara during the summer (when the SHL is over the Sahara). In turn, this heating intensifies the cyclonic circulation of the SHL thereby leading to enhanced advection of water vapor towards the Sahara.Hence, analyzing the decadal trends of water vapor in the Tropics and sub-Tropics is important to increase knowledge of the dynamics of the SHL, a pivotal feature of the West African Monsoon system.For the first time we show the impact of the variability of the African monsoon associated with the modulation of the latitude of intertropical discontinuity (ITD), the Saharan Heat Low (SHL), the low level jet (LLJ) and African Easterly Jet (AEJ) on the uprising of dust during the periods of June 2006 and June 2011, corresponding to the AMMA and FENNEC field campaigns, respectively.
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Akuetevi, Cataria Quam Cyrille. "Dynamics of turbulent western boundary currents at low latitudes, a numerical study". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENU002/document.
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Les courants turbulents de bord ouest sont l'un des phénomènes les plus dominants des océans, il en existe aux faibles latitudes aussi. Ils sont caractérisés par une dynamique très turbulente avec une forte production d'énergie cinétique, et une forte variabilité interne. Plusieurs régions existent où les courants de bord ouest se rétrofléchissent (décollage de la côte) pour former des structures cohérentes: des anticyclones, des bursts (arrachements) et des dipoles. Circulant le long de la côte, les courants de bord ouest interagissent très fortement avec le bord ouest et la bathymétrie et sont donc un problème de couche limite. Cependant aucune étude du point de vue de la théorie de couche limite n'a été jamais été faite. Cette thèse aborde le problème d'un point de vue de couche limite par l'utilisation d'un modèle idéalisé "shallow water" à très haute résolution (2.5km) afin d'isoler et de comprendre les processus. Les résultats sont ensuite appliqués à des sorties de modèle réaliste Drakkar (~10km) basé sur le code NEMO. Le courant de Somali est ensuite pris pour cette applicationStrong western boundary currents are one of dominant features of the world oceans, also at low latitudes. They exhibit a turbulent dynamics and their region is a source of strong kinetic energy production and internal variability of the worlds oceans. Several places exists where the western boundary currents retrofect (i.e separation from the coast) and generate coherent structures as anticyclonic eddies, bursts and dipoles. The dynamics of turbulent western boundary currents has so far not been extensively studied in the viewpoint of turbulent boundary-layer theory. The approach followed in this thesis is to use a fine resolution (2.5km) reduced-gravity shallow water model to understand the turbulent boundary-layer processes and then apply these findings to the Ocean General Circulation Model NEMO in the Drakkar configuration (~10km). The case of the Somali Currentis considered for this application
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Roehrig, Romain. "Variabilité intrasaisonnière de la mousson africaine : caractérisation et modélisation". Phd thesis, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00560954.
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La variabilité intrasaisonnière de la mousson d'Afrique de l'Ouest se caractérise par une alternance de phases sèches et humides, dont les impacts pe uvent être dramatiques sur les populations locales. Cette variabilité met en jeu un grand nombre d'échelles spatiales et temporelles, rendant difficile sa compréhension, sa modélisation et sa prévision. Cette thèse propose quelques éclairages sur ces différentes thématiques. La dépression thermique saharienne est un acteur majeur de la mousson africaine. La caractérisation de sa variabilité intrasaisonnière a permis de mettre en évidence, à l'échelle de 15 jours, l'existence d'interactions entre les latitudes moyennes et l'Afrique de l'Ouest. Lors de son passage au-dessus de l'Atlantique et la Méditerranée, un train d'ondes de Rossby module les ventilations de la dépression thermique, et donc sa structure. Les anomalies de circulation, de température et d'humidité, ainsi induites sur le Sahel, pourraient alors expliquer une partie des fluctuations intrasaisonnières de la convection, notamment celles qui naissent sur l'est du Sahel, et qui se propagent ensuite vers l'ouest. L'état moyen et la variabilité intrasaisonnière de la mousson africaine restent un défi pour les modèles de climat, même pour la dernière génération, qui a participé à l'exercice d'intercomparaison CMIP3. La variabilité à haute fréquence de la convection est un élément particulièrement difficile à modéliser. Toutefois, la meilleure prise en compte de facteurs inhibant le développement de la convection pourrait être une étape importante pour améliorer la modélisation de la mousson et la prévision de ses fluctuations intrasaisonnières
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Liu, Pei-Teng, i 劉沛滕. "A Study of Low-Level Wind Shear at Taipei Basin during the Northeast Monsoon Period". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/77264474975961222255.
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碩士國立臺灣大學
大氣科學研究所
101
Low-level wind shear is one of the important factors of flight safety factors. Low-level wind shear is defined as 15 kts/km wind vector difference which persists more than 10 seconds between surface and 2,000 feet (600 m) height. At some airports, low-level wind shear could be detected by Low Level Windshear Alert System (LLWAS). However, due to the synoptic environment and topographic effect of Taipei Basin, the low-level wind shear phenomena may occur outside the LLWAS detecting range. Through the influences of northeast monsoon, low-level wind shear might occur at western and north-western regions of Taipei Basin. In order to study low-level wind shear over the western region of Taipei Basin, a field network observation in high temporal resolution with 4 mobile weather stations and one ceilometer lidar lasting for two months were conducted. After data quality control and wind field estimation at 250 m height, the divergence/convergence values in which the strengths are over the low-level wind shear''s threshold were estimated by "triangle recursion calculation method." During the observation period, the observatory network detected several cases of low-level wind shear which corresponds Song-Sang Airport (RCSS) LLWAS warning record well. Moreover, by means of a negative correlation existed in the divergence/convergence field between two regions, the air streams over the observatory network are deflected. To understand the performance of numerical model simulation on low-level wind shear, Weather Research Forecasting (WRF) model and high resolution computational fluid dynamics STREAM model are used to simulate and discuss cases of low-level wind shear at Taipei Basin during the northeast monsoon period. The WRF numerical model can simulate significant vorticity field and divergence/convergence field in which the strengths are over the low-level wind shear''s threshold. The results show that WRF model with 1-km resolution simulation can capture the low-level wind shear successfully by the influence of topography under various synaptic environment conditions. In the strong northeastly wind case on Oct. 25th of 2010, the simulation results show that the hot spots of low-level wind shear locate at western and north-western regions of Taipei Basin including part region of RCSS. The results are consistent with the low-level wind shear alerts of RCSS. The STREAM model uses high resolution topography data and gives stationary boundary wind to simulate the wind structure during the strong northeast monsoon blowing into Taipei Basin. The results show the location of strong wind region at Taipei Basin. With the convergence and deflection of wind, the possible occurring region of low-level wind shear may be further confirmed.
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"The development of climatic design guidelines for low-rise low and middle income group housing in the composite hot-dry/monsoon climates of south India". Chinese University of Hong Kong, 1995. http://library.cuhk.edu.hk/record=b5888563.
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by Shrinath Tandur.Thesis (M.Phil.)--Chinese University of Hong Kong, 1995.
Includes bibliographical references (leaves 122-125).
Chapter 1.0 --- BACKGROUND --- p.13
Chapter 1.1 --- The Site --- p.19
Chapter 1.2 --- Low-rise housing for Low and Middle Income groups (LIG & MIG) --- p.20
Chapter 1.3 --- Use of space with respect to time --- p.28
Chapter 1.4 --- Adapting for comfort --- p.31
Chapter 1.5 --- The roof as a sleeping area --- p.32
Chapter 2.0 --- OBJECTIVE --- p.34
Chapter 3.0 --- METHODOLOGY --- p.35
Chapter 3.1 --- DEROB - an overview --- p.38
Chapter 3.2 --- Modelling the climate --- p.42
Chapter 3.2.1 --- The climate of --- p.42
Chapter 3.2.2 --- Modelling the climate --- p.44
Chapter 3.2.3 --- Special weather files --- p.50
Chapter 3.3 --- Fanger's Comfort Equation --- p.54
Chapter 3.3.1 --- The Predicted Mean Vote --- p.56
Chapter 3.3.2 --- The Predicted Percentage Dissatisfied --- p.58
Chapter 3.3.3 --- Range of values --- p.60
Chapter 3.4 --- Modelling the housing unit on DEROB --- p.64
Chapter 3.4.1 --- Standard building materials --- p.64
Chapter 3.4.2 --- Modelling building materials --- p.65
Chapter 3.4.3 --- Development of a method --- p.66
Chapter 3.4.4 --- The simplified cube --- p.69
Chapter 4.0 --- The -DEROB exercises --- p.72
Chapter 4.1 --- A study of variations air changes rates & times --- p.72
Chapter 4.2 --- The damping effect of the earth's mass --- p.76
Chapter 4.3 --- The effect of orientation --- p.79
Chapter 4.4 --- The effect of external wall mass --- p.82
Chapter 4.5 --- The effect of colour upon external wall mass --- p.84
Chapter 4.6 --- The effect of shadowing upon a building --- p.87
Chapter 4.7 --- The influence of internal wall mass --- p.91
Chapter 4.8 --- The effect of the roof --- p.94
Chapter 4.9 --- An analysis of parapet walls --- p.97
Chapter 4.10 --- The effect of openings and shading --- p.103
Chapter 5.0 --- A SUMMARY OF RESULTS --- p.106
Chapter 5.0.1 --- A summary brief --- p.109
Chapter 5.1 --- Preliminary Design Guidelines --- p.110
Chapter 5.2 --- A validation of results using a model of a complete housing unit --- p.118
Chapter 5.3 --- Afterword --- p.121
Chapter 6.0 --- BIBLIOGRAPHY --- p.122
Chapter 7.0 --- APPENDICES --- p.126
Chapter 7.1 --- Appendix A： Activity Chart --- p.126
Chapter 7.2 --- Appendix B： Clo values --- p.127
Chapter 7.3 --- Appendix C： Sundials for latitudes 12°. 14° & 16° N --- p.129
Chapter 7.4 --- Appendix D; A shortlist of digital simulation models --- p.131
Chapter 7.5 --- Appendix E: Weather Data for Chitradurga District --- p.133
Chapter 7.6 --- Appendix F: HUDCO' s classification of income groups --- p.143
Książki na temat "Monsoon lows"
1
Varkey, M. J. Science of Asian monsoon. Dona Paula: M.J. Varkey, 2007.
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2
Lachniet, Matthew S., i Juan Pablo Bernal-Uruchurtu. AD 550–600 Collapse at Teotihuacan. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780199329199.003.0006.
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We analyze a 2400-year rainfall reconstruction from an ultra-high-resolution absolutely-dated stalagmite (JX-6) from southwestern Mexico (Lachniet et al., 2012). Oxygen isotope variations correlate strongly to rainfall amount in the Mexico City area since 1870 CE, and for the wider southwestern Mexico region since 1948, allowing us to quantitatively reconstruct rainfall variability for the Basin of Mexico and Sierra Madre del Sur for the past 2400 years. Because oxygen isotopes integrate rainfall variations over broad geographic regions, our data suggest substantial variations in Mesoamerican monsoon strength over the past two millennia. As a result of low age uncertainties (≤ 11 yr), our stalagmite paleoclimate reconstruction allows us to place robust ages on past rainfall variations with a resolution an order of magnitude more precise than archeological dates associated with societal change. We relate our new rainfall reconstruction to the sequence of events at Teotihuacan (Millon, 1967; Cowgill, 2015a) and to other pre-Colombian civilizations in Mesoamerica. We observe a centuries long drying trend that culminated in peak drought conditions in ca. 750 CE related to a weakening monsoon, which may have been a stressor on Mesoamerican societies. Teotihuacan is an ideal location to test for links between climate change and society, because it was located in a semi-arid highland valley with limited permanent water sources, which relied upon spring fed irrigation to ensure a reliable maize harvest (Sanders, 1977). The city of Teotihuacan was one of the largest Mesoamerican cities, which apparently reached population sizes of 80,000 to 100,000 inhabitants by AD 300 (Cowgill, 1997; 2015a). Following the “Great Fire”, which dates approximately to AD 550, population decreased to lower levels and many buildings were abandoned (Cowgill, 2015). Because of the apparent reliance on rainwater capture (Linn é, 2003) and spring-fed agriculture in the Teotihuacan valley to ensure food security and drinking water, food production and domestic water supplies should have been sensitive to rainfall variations that recharge the surficial aquifer that sustained spring discharge prior recent groundwater extraction.
3
Yang, Kun. Observed Regional Climate Change in Tibet over the Last Decades. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.587.
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The Tibetan Plateau (TP) is subjected to strong interactions among the atmosphere, hydrosphere, cryosphere, and biosphere. The Plateau exerts huge thermal forcing on the mid-troposphere over the mid-latitude of the Northern Hemisphere during spring and summer. This region also contains the headwaters of major rivers in Asia and provides a large portion of the water resources used for economic activities in adjacent regions. Since the beginning of the 1980s, the TP has undergone evident climate changes, with overall surface air warming and moistening, solar dimming, and decrease in wind speed. Surface warming, which depends on elevation and its horizontal pattern (warming in most of the TP but cooling in the westernmost TP), was consistent with glacial changes. Accompanying the warming was air moistening, with a sudden increase in precipitable water in 1998. Both triggered more deep clouds, which resulted in solar dimming. Surface wind speed declined from the 1970s and started to recover in 2002, as a result of atmospheric circulation adjustment caused by the differential surface warming between Asian high latitudes and low latitudes.The climate changes over the TP have changed energy and water cycles and has thus reshaped the local environment. Thermal forcing over the TP has weakened. The warming and decrease in wind speed lowered the Bowen ratio and has led to less surface sensible heating. Atmospheric radiative cooling has been enhanced, mainly through outgoing longwave emission from the warming planetary system and slightly enhanced solar radiation reflection. The trend in both energy terms has contributed to the weakening of thermal forcing over the Plateau. The water cycle has been significantly altered by the climate changes. The monsoon-impacted region (i.e., the southern and eastern regions of the TP) has received less precipitation, more evaporation, less soil moisture and less runoff, which has resulted in the general shrinkage of lakes and pools in this region, although glacier melt has increased. The region dominated by westerlies (i.e., central, northern and western regions of the TP) received more precipitation, more evaporation, more soil moisture and more runoff, which together with more glacier melt resulted in the general expansion of lakes in this region. The overall wetting in the TP is due to both the warmer and moister conditions at the surface, which increased convective available potential energy and may eventually depend on decadal variability of atmospheric circulations such as Atlantic Multi-decadal Oscillation and an intensified Siberian High. The drying process in the southern region is perhaps related to the expansion of Hadley circulation. All these processes have not been well understood.
4
Fletcher, Roland, Brendan M. Buckley, Christophe Pottier i Shi-Yu Simon Wang. Fourteenth to Sixteenth Centuries AD. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780199329199.003.0010.
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Angkor, the capital of the Khmer Empire in Southeast Asia, was the most extensive low-density agrarian-based urban complex in the world. The demise of this great city between the late 13th and the start of the 17th centuries AD has been a topic of ongoing debate, with explanations that range from the burden of excessive construction work to disease, geo-political change, and the development of new trade routes. In the 1970s Bernard-Phillipe Groslier argued for the adverse effects of land clearance and deteriorating rice yields. What can now be added to this ensemble of explanations is the role of the massive inertia of Angkor’s immense water management system, political dependence on a meticulously organized risk management system for ensuring rice production, and the impact of extreme climate anomalies from the 14th to the 16th centuries that brought intense, high-magnitude monsoons interspersed with decades-long drought. Evidence of this severe climatic instability is found in a seven-and-a-half century tree-ring record from tropical southern Vietnam. The climatic instability at the time of Angkor’s demise coincides with the abrupt transition from wetter, La Niña-like conditions over Indochina during the Medieval Warm Period to the more drought-dominated climate of the Little Ice Age, when El Niño appears to have dominated and the ITCZ migrated nearly five degrees southward. As this transition neared, Angkor was hit by the double impact of high-magnitude rains and crippling droughts, the former causing damage to water management infrastructure and the latter decreasing agricultural productivity. The Khmer state at Angkor was built on a human-engineered, artificial wetland fed by small rivers. The management of water was a massive undertaking, and the state potentially possessed the capacity to ride out drought, as it had done for the first half of the 13th century. Indeed, Angkor demonstrated just how powerful a water management system would be required and, conversely, how formidable a threat drought can be. The irony, then, is that extreme flooding destroyed Angkor’s water management capacity and removed a system that was designed to protect its population from climate anomalies.
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Lézine, Anne-Marie. Vegetation at the Time of the African Humid Period. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.530.
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An orbitally induced increase in summer insolation during the last glacial-interglacial transition enhanced the thermal contrast between land and sea, with land masses heating up compared to the adjacent ocean surface. In North Africa, warmer land surfaces created a low-pressure zone, driving the northward penetration of monsoonal rains originating from the Atlantic Ocean. As a consequence, regions today among the driest of the world were covered by permanent and deep freshwater lakes, some of them being exceptionally large, such as the “Mega” Lake Chad, which covered some 400 000 square kilometers. A dense network of rivers developed.What were the consequences of this climate change on plant distribution and biodiversity? Pollen grains that accumulated over time in lake sediments are useful tools to reconstruct past vegetation assemblages since they are extremely resistant to decay and are produced in great quantities. In addition, their morphological character allows the determination of most plant families and genera.In response to the postglacial humidity increase, tropical taxa that survived as strongly reduced populations during the last glacial period spread widely, shifting latitudes or elevations, expanding population size, or both. In the Saharan desert, pollen of tropical trees (e.g., Celtis) were found in sites located at up to 25°N in southern Libya. In the Equatorial mountains, trees (e.g., Olea and Podocarpus) migrated to higher elevations to form the present-day Afro-montane forests. Patterns of migration were individualistic, with the entire range of some taxa displaced to higher latitudes or shifted from one elevation belt to another. New combinations of climate/environmental conditions allowed the cooccurrences of taxa growing today in separate regions. Such migrational processes and species-overlapping ranges led to a tremendous increase in biodiversity, particularly in the Saharan desert, where more humid-adapted taxa expanded along water courses, lakes, and wetlands, whereas xerophytic populations persisted in drier areas.At the end of the Holocene era, some 2,500 to 4,500 years ago, the majority of sites in tropical Africa recorded a shift to drier conditions, with many lakes and wetlands drying out. The vegetation response to this shift was the overall disruption of the forests and the wide expansion of open landscapes (wooded grasslands, grasslands, and steppes). This environmental crisis created favorable conditions for further plant exploitation and cereal cultivation in the Congo Basin.
Części książek na temat "Monsoon lows"
1
Saha, Kshudiram. "Tropical Disturbances (Quasi-stationary Waves, Easterly/Westerly Waves, Lows and Depressions, Cyclonic Storms, and Meso-Scale Disturbances)". W Tropical Circulation Systems and Monsoons, 33–60. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03373-5_2.
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Dawn, S., i M. Mandal. "Surface Meso High and Wake Low Associated with Pre-Monsoon Thunderstorm Over the Kharagpur Region". W Advances in Meteorology, Climatology and Atmospheric Physics, 57–63. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-29172-2_9.
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Khim, Boo-Keun, Ji-Eun Kim, Keiji Horikawa, Minoru Ikehara, Yoshihiro Asahara i Jongmin Lee. "Orbital-Scale Paleoceanographic Response to the Indian Monsoon in the Laxmi Basin of the Eastern Arabian Sea". W Patterns and Mechanisms of Climate, Paleoclimate and Paleoenvironmental Changes from Low-Latitude Regions, 9–11. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-01599-2_2.
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Knudsen, Magne. "Changing Tides: Temporal Dimensions of Low-Cost, High-Skill Fisheries in the Central Visayas, Philippines". W Case Studies in Biocultural Diversity from Southeast Asia, 21–42. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-6719-0_2.
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AbstractAt the southern mouth of the Tañon Strait—the body of water that separates the islands of Cebu and Negros in the Visayas region of the Philippines—small-scale fishing has always been challenging. Strong and complex sea currents make it difficult for fishers to utilise certain fishing gears. With a significant decline in the resource base and new regulations of the fisheries in recent decades, only fishers with advanced skills and fine-grained place-specific and calendric knowledge of the marine environment are able to catch enough fish, and the right kind of fish, to secure a decent return. Drawing on insights from cultural ecology, the chapter examines the skills and knowledges that fishers draw on to catch fish in this challenging environment. It gives particular attention to the temporal dimensions of the biocultural knowledge complex, showing how fishers’ knowledge of the links between sea currents, the lunar cycle and monsoon winds play into their decisions about where, when and how to fish. In addition to its direct livelihood significance, calendric knowledge also serves as a resource in the formation of identity as mananagat (fisherman) and authority and status within the fishing community. To further explain why some fishers are able to use their knowledge to make fishing a viable and legitimate livelihood and others are not, the last part of the chapter uses insights from political ecology to address issues of power and dynamics of exclusion in the fisheries.
5
Stojanov, Robert, i Ilan Kelman. "Local Expert Perceptions of Creeping Environmental Changes and Responses in Maldives". W IMISCOE Research Series, 173–85. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-34194-6_12.
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AbstractFor the last several decades, low-elevation islands have been highlighted as being at the forefront of facing the impact of creeping environmental changes, notably from human-caused climate change. The islands’ low elevation, including in the Indian Ocean, has led to considering migration due to coastal erosion, sea-level rise, acidifying oceans, salinity intrusion, and changes in monsoon patterns and hence rainfall. Maldives is experiencing such creeping environmental changes which are often stated as being key factors affecting Maldivian society, livelihoods, and futures. Evidence from Maldivians, however, is that they perceive future sea-level rise to be a serious challenge at the national level, but rarely accept it as a local difficulty requiring action. Migration from their islands to other countries might be a potential option, especially when combined with other reasons for relocating, but they generally prefer to stay and adjust to all ongoing changes. Within this context, this paper reports field research from August 2013 in the capital Malé and nearby residential islands, using qualitative interviews with fifteen local experts. The results suggest that, besides a set of actually experienced changes, creeping environmental changes are perceived as being one of the important factors affecting Maldivian society and livelihoods. The results and interpretation, including in the context of major changes from the ongoing COVID-19 pandemic, identify some dissonance in understandings of possible impacts and resultant actions, in terms of recognising what might happen to the country yet not fully considering the action-related implications.
6
Chuan, Goh Kim. "The Climate of Southeast Asia". W The Physical Geography of Southeast Asia. Oxford University Press, 2005. http://dx.doi.org/10.1093/oso/9780199248025.003.0015.
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Southeast Asia lies between the continental influence of the rest of Asia to the north and the more oceanic influence of the Indian and Pacific Oceans to the south and the east respectively. While its overall net energy balance is very much determined by its latitudinal position, which is approximately between 20°N and 10°S, the locational factors referred to above largely give the regional climate its distinctive character. Within the broad latitudinal extent defined above, the Southeast Asian region has often been conveniently separated into two sub-areas: continental and insular Southeast Asia. In some ways these sub-regions represent a valid delineation into the more seasonal climatic region influenced by the monsoon system of winds and the uniformly humid equatorial climate. The former comprises Myanmar, Thailand, Lao PDR, Cambodia, and Viet Nam, while the latter includes Malaysia, Singapore, Indonesia, and the Philippines. The continental Southeast Asia experiences greater seasonality, more extremes in both temperature and rainfall, and more pronounced dry spells; whereas the insular parts, termed the ‘maritime continent’ (Ramage 1968), with a much greater expanse of sea than land (the sea area of Indonesia, for example, is four times its land area), have more equable climate. The northern and southern continental interactions in winter and summer and the differential heating due to the asymmetric character of the two sub-regions give rise to the monsoon development (Hastenrath 1991), which, to a large extent, influences the rainfall characteristics of the region as a whole. In a sense, more than temperature variations, this monsoonal influence gives the Southeast Asian climate its distinctive character. Figure 5.2 shows the two monsoon wind systems that affect Southeast Asia. In addition to these annual reversals of the monsoon winds, the seasonal migration of the Intertropical Convergence Zone (ITCZ)—closest to the Equator during the northern hemispheric winter and farthest north during summer—is a significant factor in influencing the monthly weather regime of the region. Being a belt of low-pressure trough coinciding with the band of highest surface temperature, the ITCZ attracts the moist easterlies from both hemispheres towards its trough resulting in uplift of air, intense convection, and precipitation. This whole process provides a mechanism for the transfer of latent heat from the low to the higher latitudes (Houze et al. 1981; Hastenrath 1991).
7
Kumar Sarma, Pallab, Nikhilesh Baruah, Rupam Borah, Rupshree Borah, Arunjyoti Sonowal, Rekhashree Kalita, Prasanta Neog, Prabal Saikia i Nipen Gogoi. "Adaptation Strategies for Climate Variability in the High Rainfall Zone of India, Assam". W Climate Change - Recent Observations [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.107045.
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The NICRA project is being implemented in two villages viz., Chamua (since 2010–2011) and Ganakdalani (since 2012–2013 till 2016–2017), which are situated in the west of Lakhimpur district of North Bank Plains Zone of Assam. Chamua village is situated in Kherajkhat Mauza (Taluka), which is 45 km away from North Lakhimpur, the headquarter of district Lakhimpur. On the other hand, Ganakdoloni is situated at Dhalpur Mauza, situated 60 km away from North Lakhimpur and 15 km away from the local township Narayanpur. During 2017–2018 four villages viz., Jakaipelua, Borbali, Borkhet, and Nogaya were adopted under the project. Analysis of long-term rainfall data confirmed the significant decreasing trend of annual as well as monsoonal rainfall in both the Brahmaputra and Barak basins of Assam, India. Variability of rainfall has been increasing in terms of the increased frequency of high-intensity rains and the reduced number of rainy days, leading to localized flash floods and the occurrence of multiple dry spells. Mean season-wise rainfall 2011–2021 indicates long dry periods during the winter season, leading to prolonged dry spells affecting crop growth. About 69% of total rainfall (average annual rainfall of Assam is 2000 mm) is received during the monsoon season, resulting in flash floods leading to crop damage. Out of 12 years of investigation, 10 years are deficit years, resulting in crop stress both during the monsoon and post-monsoon period. Preparation and implementation of real-time crop contingencies are important in responding to weather aberrations in different strategies like preparedness, real-time response, etc. Identification of various adaptation strategies, including climate-resilient crops and cultivars, rainwater harvesting and recycling, efficient energy management through farm mechanization, dissemination of weather information, and weather-based agro-advisories to farmers in a real-time basis, is important adaptation technologies for building climate-resilient agriculture. The study showed that adaption of climate-resilient crop and cropping system and use of harvested rainwater resulted in a 12 to 30% increase in yield observed by the cultivation of high-yielding rice varieties (HYVs) (Ranjit, Gitesh, Mahsuri, etc.) when sown in time (before 15th June) over late sowing conditions (after 20th June). In the case of early season drought, replacement of long duration traditional varieties with short duration HYV and life-saving irrigation using harvested rainwater increased yield by about 59% (short duration var. Dishang) over non-irrigated fields. In case of mid-season and terminal drought, application of an additional dose of 22 kg ha−1 MOP at maximum tillering to grain growth period an increase in yield of about 33% (Ranjit), 32% (Gitesh), 64% (Shraboni), and 57.5% (Mulagabharu) has been observed over farmers’ practice. In highly flood-affected areas under lowland situations replacement of submergence tolerant varieties (Jalashree and Jalkuwari) with traditional deepwater rice varieties resulted in reduced crop loss due to the genetic trait of the deepwater rice, which can withstand water logging for a long period. With an increase in the level of mechanization through the use of machinery available in the custom hiring center the human and animal hour requirement for paddy cultivation was reduced from 795 to 350 hrha−1 and 353 to 23 hrha−1, respectively. Alternate land use in terms of low-cost poly house, vermicompost production, and mushroom cultivation also resulted in nutritional security and generation of higher income for the farmers
8
Rahman, Hakikur. "Data Mining Techniques to Improve Early Warning Systems across the Bay of Bengal". W Advances in Data Mining and Database Management, 53–86. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-4078-8.ch004.
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This chapter is a conceptual contribution to this book on data mining applications upholding ethical issues related to two extremely important aspects of the Bangladeshi population: the early warning system and the disaster management system. The chapter tries to provide a few conceptual ideas to introduce ethical data mining application in these systems to support the agencies that are involved for an improved, efficient, and transparent support system in the country, especially across the Bay of Bengal. Resembling a triangular shape (deltaic), a major portion of the bay touches the southern portion of Bangladesh. Sediments from rivers have made the bay a shallow sea. Due to its shallowness and shape, monsoon rains and cyclone storms become destructive, causing great loss of life along the southern part of the country. Moreover, the three mighty rivers (Padma, Jamuna, and Meghna) form one of the largest river systems in the world. They have a large number of distributaries and tributaries, which cause a major portion of the country to be inundated by monsoon rain. In addition, being the lowest landing zone of the Himalayan water, Bangladesh becomes victim to floods almost every year. Loss of lives, destruction of properties, suffering of numerous people and hampering of economic development have become part and parcel of Bangladeshi communities. This chapter suggests that the newly emerged data mining techniques can be introduced to collect, synthesize, analyze, archive, disseminate, and even make future forecasts forming a reliable early warning system across the Bay of Bengal.
9
Schmidt-Vogt, Dietrich. "Causes of land-use change and biodiversity loss in Monsoon Asia". W Sustainable Development: Asia-Pacific Perspectives, 367–76. Cambridge University Press, 2022. http://dx.doi.org/10.1017/9780511977961.033.
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Maji, S., Pramiti K. Chakraborty, S. Basu, Sarika Jena, Ratneswar Poddar, R. Nath, P. Bandopadhyay i P. K. Chakraborty. "Crop Weather Interaction in Potato in South Bengal Plains". W Sustainable Potato Production and the Impact of Climate Change, 50–86. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-1715-3.ch003.
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Potato is one of the main staple foods in West Bengal, where it ranks second in production after Uttar Pradesh. There is lots of variation in productivity of the crop. It is due to climatic variability which causes widespread disease infection in potato crop. The shifting of onset and withdrawal of monsoons has also proved to be a barrier in the productivity of the crop. The farmers are habituated to plant the crop within 15th of November; however this is being disrupted because of the shifting of withdrawal of monsoons. Potato is a thermo sensitive crop. The crop growth rate of potato is significantly affected by cumulative maximum and minimum temperatures. Leaf area index significantly decreased with the increase in cumulative maximum and minimum temperatures. Rainfall and relative humidity are two crucial factors that determine the incidence of late blight in potato, the most devastating disease in Bengal. Rainfall increased productivity by lowering soil temperature and reducing hydrolysis of starch respiratory losses from tubers.
Streszczenia konferencji na temat "Monsoon lows"
1
Amir Rashidi, M. Rashad, Edgar Peter Dabbi, Ahmad Ismail Azahree, Zainol Affendi Abu Bakar, Dylon Tan Jen Huang, Claus Pedersen, Pankaj K. Tiwari i in. "CO2 Leakage Marine Dispersion Modelling for an Offshore Depleted Gas Field for CO2 Storage". W Offshore Technology Conference Asia. OTC, 2022. http://dx.doi.org/10.4043/31447-ms.
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Abstract A depleted gas field situated in offshore Sarawak has been identified by PETRONAS as a potential CO2 storage development site. As part of the monitoring program, CO2 seepage risk and impact on the marine environment needs to be investigated and predicted. This study focuses on understanding the environmental risks associated with the potential seepage of CO2 gas at the depleted field within the 140 m water column through methods of numerical modelling. Leakage scenarios involving existing plugged and abandoned (P&A) wells as CO2 leakage pathways were modelled with leakage rates of 6 tonnes/year, representing a realistic rate and 500 tonnes/year which represents a more improbable and conservative scenario. The modelling period covers three representative climatic periods for the prevailing monsoons in the South China Sea (northwest, southwest and inter-monsoon). Simulation results showed that with the lower rate, changes to the seawater acidity within the far field region were negligible or undetectable. Under the high seepage rate, the pH plume footprint was predicted to extend beyond 200 m distance from the source point. However, the probability was estimated to be less than 1% while the vertical extent of the plume was limited up to 2 m above the seabed. For both scenarios, the CO2 gas were predicted to be fully dissolved within 5 m above the seabed. Therefore, it can be concluded that there is relatively low risk of impact at the storage field in terms of potential increase in seawater acidity if CO2 seepage occurs during the storage period.
2
Zheng, Zhenjun, Xiaozhou Ma, Xuezhi Huang, Yujin Dong i Guohai Dong. "Low-Frequency Oscillations Within the Hambantota Port During the Southwest Monsoon, 2019". W ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18518.
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Abstract Long waves with periods greater than tens of seconds propagating into a harbor may be trapped and significantly amplified, thereby resulting in detrimental effects on port operations. The water surface elevation in the Hambantota Port, Sri Lanka, was measured to investigate the low-frequency oscillations and their forcing mechanisms. Results show that the port is protected well from short waves with periods less than 30 s; however, the protection against long waves with periods larger than 30 s is inadequate. The spectral analyses identified four dominant periods within the low-frequency wave range. Modal analysis based on the extended mild-slope equation shows that the measured spectrum density for some dominant periods is low because the measurement point is close to the corresponding modal lines. Correlation analysis shows that low-frequency oscillations inside the Hambantota Port are excited directly by the low-frequency waves contained within the incident waves. The low-frequency waves outside the Hambantota Port are generated from the higher-frequency gravity waves (swell and wind waves) due to nonlinear interactions. Empirical formula is adopted to estimate the low-frequency wave height outside the Hambantota Port.
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Agarwal, A., J. S. Pillai, K. Aurobindo, J. D. Abhyankar, G. Isola, P. Srivastava i Abhishek Kodilkar. "Monsoon cloud observations using a low power vertical looking Ka Band Cloud radar". W IGARSS 2016 - 2016 IEEE International Geoscience and Remote Sensing Symposium. IEEE, 2016. http://dx.doi.org/10.1109/igarss.2016.7729554.
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Liao, Mengyuan, Toshihiko Hojo, Guijun Xian, Yuqiu Yang i Hiroyuki Hamada. "Environmental Degradation Behavior of Kenaf Fiber Mat Composite". W ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-38248.
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Nowadays “eco-design” is becoming a philosophy to guide next generation of materials and products as global environmental issue produced by fossil fuels and resource overusing. With an industrial increasing interest in sustainable, eco-efficient and green material’s application, natural fiber in polymer composite is guided to develop rapidly. As well know that, natural fibers possess advantages over synthetic or manmade fibers due to its abundance, biodegradability, CO2 neutrality, excellent price/performance ratio and comparable specific strength properties. However, outdoor applications of natural fiber composite are still constrained and raising concerns in terms of their durability, including UV resistance, moisture resistance and extreme temperature withstand and dimensional stability. Continuing with previous research on kenaf non-woven reinforced unsaturated polyester composites three months degradation performance, in order to get a good knowledge of its degradation process/cycle in complicated outdoor environments, longer degradation periods up to 6 months and 12 months in this paper were added for further investigation and comparison. Initially, three sets of kenaf fiber mat composite samples were located in extreme cold temperature (Harbin), mild sea climate Kyoto (Japan), subtropical marine monsoon climate Shanghai (China) and tropical monsoon climate Zaria (Nigeria) respectively from the same starting time until predetermined ageing periods, afterwards weight change and mechanical behavior in terms of tensile, flexural, impact and fracture toughness were measured instrumentally for ageing effect discussion and comparison. As expected, the aged specimens in those different positions all showed the dropped mechanical properties with increasing ageing periods. Furthermore, the trend of degradation in various mechanical parameters was established, which demonstrated weight loss made more serious effect on aged sample’s mechanical properties’ reduction than water absorption behavior. In a word, dropped mechanical properties of the degraded composites accompanied with weight change behavior were clarified, in which degradation phenomenon of embrittled the matrix polymer, deteriorated reinforced fiber and interfacial properties were detected.
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Макарова, Т. Р. "CHANGES OF THE HUMIDIFICATION OF VALLEY PEAT BAGS R.BOLSHAYA USSURKA (PRIMORYE) BY THE DATA OF THE DIATOMIC ANALYSIS". W Геосистемы Северо-Восточной Азии. Crossref, 2021. http://dx.doi.org/10.35735/tig.2021.69.14.022.
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Изучение разреза торфяника в бассейне р. Большая Уссурка (Приморье) позволило выявить изменения увлажненности. Установлен период продолжительных засух, совпадавших с ослаблением летнего муссона. Несмотря на сухие условия проходили паводки, вызванные тайфунами или глубокими циклонами. Влажными были малый оптимум голоцена и малый ледниковый период, характеризовавшиеся усилением циклогенеза. Отмечены кратковременные флуктуации увлажнения, периоды с разной паводковой активностью. Study of the peat bog section in the river basin Bolshaya Ussurka (Primorye) made it possible to distinguish periods with different moisture. Period of prolonged droughts was established, coinciding with the weakening of the summer monsoon. Dry conditions did not exclude floods due to the passage of typhoons or deep cyclones. The low optimum of the Holocene and the Little Ice Age, characterized by increased cyclogenesis, were humid. Short-term fluctuations of moisture, periods with different flood activity were noted.
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Manoj, M. G., Mohankumar, V. Rakesh i Rejoy Rebello. "Features of low level winds over Cochin during the deluge of Monsoon-2018 using 205 MHz wind Profiler Radar". W 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC). IEEE, 2019. http://dx.doi.org/10.23919/ursiap-rasc.2019.8738657.
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Lijuan Wang, Hui Gao i Shan Lu. "Effect of low frequency oscillation of Monsoon on the heavy rainfall from the landing typhoon based on the Wavelet analysis". W 2011 International Conference on Information Science and Technology (ICIST). IEEE, 2011. http://dx.doi.org/10.1109/icist.2011.5765292.
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Karmakar, Nirupam, Arindam Chakraborty i Ravi S. Nanjundiah. "The spatio-temporal structures and role of low- and high-frequency intraseasonal modes in Indian Summer monsoon rainfall observed in TRMM data". W SPIE Asia-Pacific Remote Sensing, redaktorzy Tiruvalam N. Krishnamurti i Madhavan N. Rajeevan. SPIE, 2016. http://dx.doi.org/10.1117/12.2228030.
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Dahal, Swaechchha, Thomas Øyvang, Gunne John Hegglid, Shailendra Kumar Jha i Bhupendra Bimal Chhetri. "Himalayan Run-Off River Power Generation Modelling for Power Security in Evolving Weather Conditions". W 63rd International Conference of Scandinavian Simulation Society, SIMS 2022, Trondheim, Norway, September 20-21, 2022. Linköping University Electronic Press, 2022. http://dx.doi.org/10.3384/ecp192022.
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Extreme black-swan occurrences like earthquakes, glacial lake outbursts, flash floods, landslides, etc. are important concerns in Himalayan countries like Nepal, which are highly susceptible, geologically active, and exquisitely fragile. Nepal generates 97 percent of its electricity from hydropower, where 56.08 percent of it is coming from seasonal run-off-river (RoR) hydro plants. Landslides and mudflows are common in the monsoon, and low discharge is common in the winter season. These RoR plants must be able to withstand high-impact events like earthquakes and lengthy droughts in order for the Nepalese grid to remain secure. This study gives a presentation and overview of previously occured natural hazards in Nepal related to hydropower plants. In particular, the 2014 Sunkoshi landslide and the 2021 Melamchi flood are evaluated as extreme events and their impacts on hydropower plant has been studied. In addition, an in-depth investigation on a ROR plant is carried out. Moreover, the water discharge and extreme rainfall peaks in time series data is evaluated using an ARIMA-based model. This paper shows the feasibility of predicting the energy produced by a run-off river hydropower plant. The purpose is to forecast discharge and hence the ROR power generation with the aim to facilitate the hydropower operators for their availability declaration which will again help in the overall energy planning. The results are discussed together with performance metrics, and indicates that the implemented technique is promising.These predictions can be further used for planning and estimating the power generation on a more complex level.
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Wu, Ching-Hui, Tsu-Jen Lin i Tsu-Mu Kao. "Study of a Station Blackout Event in the PWR Plant". W 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22757.
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On March 18, 2001, a PWR nuclear power plant located in the Southern Taiwan occurred a Station BlackOut (SBO) event. Monsoon seawater mist caused the instability of offsite power grids. High salt-contained mist caused offsite power supply to the nuclear power plant very unstable, and forced the plant to be shutdown. Around 24 hours later, when both units in the plant were shutdown, several inadequate high cycles of bus transfer between 345 kV and 161 kV startup transformers degraded the emergency 4.16 kV switchgears. Then, in the Train-A switchgear room of Unit 1 occurred a fire explosion, when the degraded switchgear was hot shorted at the in-coming 345 kV breaker. Inadequate configuration arrangement of the offsite power supply to the emergency 4.16 kV switchgears led to loss of offsite power (LOOP) events to both units in the plant. Both emergency diesel generators (EDG) of Unit 1 could not be in service in time, but those of Unit 2 were running well. The SBO event of Unit 1 lasted for about two hours till the fifth EDG (DG-5) was lined-up to the Train-B switchgear. This study investigated the scenario of the SBO event and evaluated a risk profile for the SBO period. Guidelines in the SBO event, suggested by probabilistic risk assessment (PRA) procedures were also reviewed. Many related topics such as the re-configuration of offsite power supply, the addition of isolation breakers of the emergency 4.16 kV switchgears, the betterment of DG-5 lineup design, and enhancement of the reliability of offsite power supply to the PWR plant, etc., will be in further studies.