scholarly journals Rainfall in Vietnam

2021 ◽  
Author(s):  
◽  
Quang Dang Nguyen
Keyword(s):  
Tropical Cyclones ◽  
Monsoon Rainfall ◽  
Rainfall Variability ◽  
Regional Scale ◽  
Southeast Asian ◽  
Climate Trends ◽  
The South ◽  
The North ◽  
Monsoon Index ◽  
Coast Of Vietnam

<p>The thesis is a comprehensive analysis of the climate of Vietnam, concentrating on rainfall. Vietnam lies in the tropical northern hemisphere in a region that is influenced by the South Asian, East Asian and Australian monsoons. Rainfall here is associated with several different mechanisms, such as the monsoon, tropical cyclones, topography, and so on. From the initial climatological analysis, monsoon and non-monsoon rainfall is investigated. Non-monsoon rainfall is found to be related to a vortex often found off the coast of Vietnam, a newly-understood extension of the “Borneo vortex”.  The thesis begins with a study of the surface climate and the general atmospheric circulation over the Southeast Asian region, which dominates Vietnam’s climate. Trends of surface temperature and rainfall were investigated for a 40 year period (1971-2010), using a newly-extended dataset of 60 stations. Vietnam’s average temperature has increased at a rate of 0.26 ± 0.10°C per decade since the 1970s, approximately twice the rate of global warming over the same period. The increase in temperature is statistically significant in most sub-regions. Trends in rainfall are however mostly insignificant in that period. Temperature and rainfall variability are shown to be linked to ENSO on both a national and sub-regional scale. The rainfall climate of Vietnam has been studied in depth, particularly the characteristics of monsoon rainfall and the variability of the length of wet and dry seasons. That investigation has led to the development of an objective monsoon index, based on regional mean sea level pressure and low level zonal wind. While originally developed to define onset and withdrawal dates for the monsoon in Vietnam and over Southeast Asia, the index is shown to be applicable in all monsoon regions of the globe, the first objective index to have such global utility. The final part of the thesis deals with tropical vortex activity and its associated rainfall. Vortices exist almost year-round, migrating from the coast of Vietnam – Southeast Asian Sea - Philippines in summer to the Borneo Island region in winter. Clear evidence is found for the presence of a semi-permanent vortex near the south coast of Vietnam or the north of the Southeast Asian Sea – Maritime Continent (SEASMC) region. It is this vortex and the tropical cyclones over the SEASMC region that significantly contribute to the Vietnam rainfall, particularly the post-monsoon rainfall in Central Vietnam.</p>

scholarly journals Rainfall in Vietnam

2021 ◽  
Author(s):  
◽  
Quang Dang Nguyen
Keyword(s):  
Tropical Cyclones ◽  
Monsoon Rainfall ◽  
Rainfall Variability ◽  
Regional Scale ◽  
Southeast Asian ◽  
Climate Trends ◽  
The South ◽  
The North ◽  
Monsoon Index ◽  
Coast Of Vietnam

<p>The thesis is a comprehensive analysis of the climate of Vietnam, concentrating on rainfall. Vietnam lies in the tropical northern hemisphere in a region that is influenced by the South Asian, East Asian and Australian monsoons. Rainfall here is associated with several different mechanisms, such as the monsoon, tropical cyclones, topography, and so on. From the initial climatological analysis, monsoon and non-monsoon rainfall is investigated. Non-monsoon rainfall is found to be related to a vortex often found off the coast of Vietnam, a newly-understood extension of the “Borneo vortex”.  The thesis begins with a study of the surface climate and the general atmospheric circulation over the Southeast Asian region, which dominates Vietnam’s climate. Trends of surface temperature and rainfall were investigated for a 40 year period (1971-2010), using a newly-extended dataset of 60 stations. Vietnam’s average temperature has increased at a rate of 0.26 ± 0.10°C per decade since the 1970s, approximately twice the rate of global warming over the same period. The increase in temperature is statistically significant in most sub-regions. Trends in rainfall are however mostly insignificant in that period. Temperature and rainfall variability are shown to be linked to ENSO on both a national and sub-regional scale. The rainfall climate of Vietnam has been studied in depth, particularly the characteristics of monsoon rainfall and the variability of the length of wet and dry seasons. That investigation has led to the development of an objective monsoon index, based on regional mean sea level pressure and low level zonal wind. While originally developed to define onset and withdrawal dates for the monsoon in Vietnam and over Southeast Asia, the index is shown to be applicable in all monsoon regions of the globe, the first objective index to have such global utility. The final part of the thesis deals with tropical vortex activity and its associated rainfall. Vortices exist almost year-round, migrating from the coast of Vietnam – Southeast Asian Sea - Philippines in summer to the Borneo Island region in winter. Clear evidence is found for the presence of a semi-permanent vortex near the south coast of Vietnam or the north of the Southeast Asian Sea – Maritime Continent (SEASMC) region. It is this vortex and the tropical cyclones over the SEASMC region that significantly contribute to the Vietnam rainfall, particularly the post-monsoon rainfall in Central Vietnam.</p>

scholarly journals Influence of the North Atlantic oscillation on the atmospheric levels of benzo[a]pyrene over Europe

2021 ◽  
Author(s):  
Pedro Jiménez-Guerrero ◽  
Nuno Ratola
Keyword(s):  
Spatial Pattern ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Transport Model ◽  
Regional Scale ◽  
The South ◽  
Climatic Fluctuations ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

AbstractThe atmospheric concentration of persistent organic pollutants (and of polycyclic aromatic hydrocarbons, PAHs, in particular) is closely related to climate change and climatic fluctuations, which are likely to influence contaminant’s transport pathways and transfer processes. Predicting how climate variability alters PAHs concentrations in the atmosphere still poses an exceptional challenge. In this sense, the main objective of this contribution is to assess the relationship between the North Atlantic Oscillation (NAO) index and the mean concentration of benzo[a]pyrene (BaP, the most studied PAH congener) in a domain covering Europe, with an emphasis on the effect of regional-scale processes. A numerical simulation for a present climate period of 30 years was performed using a regional chemistry transport model with a 25 km spatial resolution (horizontal), higher than those commonly applied. The results show an important seasonal behaviour, with a remarkable spatial pattern of difference between the north and the south of the domain. In winter, higher BaP ground levels are found during the NAO+ phase for the Mediterranean basin, while the spatial pattern of this feature (higher BaP levels during NAO+ phases) moves northwards in summer. These results show deviations up to and sometimes over 100% in the BaP mean concentrations, but statistically significant signals (p<0.1) of lower changes (20–40% variations in the signal) are found for the north of the domain in winter and for the south in summer.

scholarly journals Climatology of Heavy Orographic Rainfall Induced by Tropical Cyclones over Madagascar: From Synoptic to Mesoscale Perspectives

2016 ◽  
Vol 5 (2) ◽  
pp. 132 ◽  
Author(s):  
Tatiana A. Arivelo ◽  
Yuh-Lang Lin
Keyword(s):  
Tropical Cyclones ◽  
Southern Oscillation Index ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
Eastern Coast ◽  
Quasi Biennial Oscillation ◽  
Trade Winds ◽  
Southwest Indian Ocean ◽  
The North ◽  
Orographic Rainfall

Variability of and generation mechanisms for Madagascar rainfall are studied by conducting climatological, synoptic and mesoscale analyses. It is found the rainfall variability is highly sensitive to seasons with high variability in summer (Nov-Apr). The rainfall in summer is controlled by the Intertropical Convergence Zone (ITCZ) and orographic rainfall associated with tropical cyclones (TCs), while the rainfall in winter (May-Oct) is controlled by trade winds and local orographic rainfall along the eastern coast. Synoptic analysis reveals that major climate variations in summer are associated with ITCZ position, which is closely related to TC genesis locations and quasi-biennial oscillation (QBO). Linkages between El-Niño Southern Oscillation Index (ENSO) and Southern Oscillation Index (SOI) are identified as the cause of inconsistent dry or wet summers. Mesoscale analysis depicts the importance of the orographic effects on prevailing wind, which are controlled by the orography in both seasons. In winter, the prevailing trade winds over the Southwest Indian Ocean are from the east and are split to the north and south when it impinges on Malagasy Mountains. On the other hand, in summer the prevailing easterlies are weaker leading to the production of lee vortices, in addition to the flow splitting upstream of the mountain. Thus, the flow is classified into two regimes: (a) flow-over regime with no lee vortices under high Froude number (Fr=1.2-1.8) flow, and (b) flow-around regime with lee vortices under low Fr (=0.88-1.16) flow. A case study of TC Domoina (1984) indicates that the long-lasting heavy rainfall was induced by the strong orographic blocking of Madagascar. The shorter-term (e.g., 2 days) heavy orographic precipitation is characterized by large VH ∙Ñh which is composed by two common ingredients, namely a strong low-level wind normal to the mountain (VH) and a steep mountain slope (∇h).

Bryophyte novelties from the Arabian Peninsula and Socotra Island

Nova Hedwigia ◽  
2020 ◽  
Vol 110 (3) ◽  
pp. 281-286
Author(s):  
Harald Kürschner ◽  
Wolfgang Frey
Keyword(s):  
Saudi Arabia ◽  
Arabian Peninsula ◽  
Monsoon Rainfall ◽  
New Records ◽  
Floristic Diversity ◽  
Southwest Asia ◽  
The South ◽  
The North ◽  
Socotra Island ◽  
Socotra Archipelago

Based on unedited bryophyte collections from the Arabian Peninsula and Socotra Island, six new records of mosses are reported for the area. New to the Arabian Peninsula are Pohlia elongata and Ptychostomum cernuum, the remaining four species are new records for Saudi Arabia, resp. Yemen (mainland) and the Socotra Archipelago. Most interesting is Hymenostylium hildebrandtii from the Makkah-Taif area, indicating the influence of the south-western monsoon rainfall far to the north. All taxa show major range extensions in Southwest Asia and contribute to the floristic diversity of the Arabian Peninsula.

scholarly journals Mesoscale Simulation of Tropical Cyclones in the South Pacific: Climatology and Interannual Variability

2011 ◽  
Vol 24 (1) ◽  
pp. 3-25 ◽  
Author(s):  
Nicolas C. Jourdain ◽  
Patrick Marchesiello ◽  
Christophe E. Menkes ◽  
Jérome Lefèvre ◽  
Emmanuel M. Vincent ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Tropical Cyclones ◽  
Large Scale ◽  
Southern Oscillation ◽  
Regional Scale ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Dimensional Structure ◽  
The South ◽  
Wide Range

Abstract The Weather Research and Forecast model at ⅓° resolution is used to simulate the statistics of tropical cyclone (TC) activity in the present climate of the South Pacific. In addition to the large-scale conditions, the model is shown to reproduce a wide range of mesoscale convective systems. Tropical cyclones grow from the most intense of these systems formed along the South Pacific convergence zone (SPCZ) and sometimes develop into hurricanes. The three-dimensional structure of simulated tropical cyclones is in excellent agreement with dropsondes and satellite observations. The mean seasonal and spatial distributions of TC genesis and occurrence are also in good agreement with the Joint Typhoon Warning Center (JTWC) data. It is noted, however, that the spatial pattern of TC activity is shifted to the northeast because of a similar bias in the environmental forcing. Over the whole genesis area, 8.2 ± 3.5 cyclones are produced seasonally in the model, compared with 6.6 ± 3.0 in the JTWC data. Part of the interannual variability is associated with El Niño–Southern Oscillation (ENSO). ENSO-driven displacement of the SPCZ position produces a dipole pattern of correlation and results in a weaker correlation when the opposing correlations of the dipole are amalgamated over the entire South Pacific region. As a result, environmentally forced variability at the regional scale is relatively weak, that is, of comparable order to stochastic variability (±1.7 cyclones yr−1), which is estimated from a 10-yr climatological simulation. Stochastic variability appears essentially related to mesoscale interactions, which also affect TC tracks and the resulting occurrence.

Differences in rainfall variability in the South and Southeast Asian summer monsoons

2004 ◽  
Vol 24 (9) ◽  
pp. 1091-1107 ◽  
Author(s):  
Igor I. Zveryaev ◽  
Marina P. Aleksandrova
Keyword(s):  
Rainfall Variability ◽  
Southeast Asian ◽  
The South ◽  
Asian Summer

scholarly journals Recent emergence of CAT5 tropical cyclones in the South Indian Ocean

2018 ◽  
Vol 114 (11/12) ◽  
Author(s):  
Jennifer M. Fitchett
Keyword(s):  
Tropical Cyclone ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
Satellite Imagery ◽  
Storm Damage ◽  
The South ◽  
South Indian Ocean ◽  
The North ◽  
South Indian ◽  
Recent Emergence

The IBTrACS global best track data set endorsed by the World Meteorological Organization provides a valuable global record of tropical cyclone genesis, track and intensity, and spans 1842 to the present. The record is significantly more robust from the late 1970s onwards, as it is supported by satellite imagery. These records indicate that the first tropical cyclone in the South Indian Ocean to intensify to CAT5 status did so in 1994. This date is significantly later than the first CAT5 storms recorded in the IBTrACS database for the Atlantic Ocean (1924) and the North Pacific (1951) recorded from ship records, and half a decade later than those of the North Indian Ocean (1989) and South Pacific (1988), captured from satellite imagery. Following this late emergence, in the period 1990–2000, eight CAT5 tropical cyclones were recorded for the South Indian Ocean. A further four have been recorded for the period 2010–2015. This recent emergence of tropical cyclones attaining category five intensity in the South Indian Ocean is of significance for the forecasting of tropical cyclone landfall and the anticipation of storm damage for the developing economies that characterise the region. Although an increase in tropical cyclone intensity is frequently projected under global climate change scenarios, the dynamics for the South Indian Ocean have remained poorly understood. Notable are early results indicating an increased frequency and poleward migration of these CAT5 storms, concurrent with a poleward migration in the position of the 26.5 °C, 28 °C and 29 °C sea surface temperature isotherms in the South Indian Ocean. Significance: Category 5 tropical cyclones, the strongest category of storms, have only recently emerged in the South Indian Ocean. Since 1989, their frequency of occurrence has increased. This increase poses a heightened risk of storm damage for the South Indian Ocean Island States and the countries of the southern African subcontinent as a result of the strong winds, heavy rainfall and storm surges associated with these storms, and the large radial extent at category 5 strength.

The Effect of Hawai’i’s Big Island on Track and Structure of Tropical Cyclones Passing to the South and West*

2011 ◽  
Vol 139 (11) ◽  
pp. 3609-3627 ◽  
Author(s):  
Christopher R. S. Chambers ◽  
Tim Li
Keyword(s):  
Tropical Cyclones ◽  
Wrf Model ◽  
Vertical Wind Shear ◽  
Weather Research And Forecasting ◽  
The South ◽  
The North ◽  
Core Convection ◽  
Island Wake ◽  
The Right ◽  
Eye Formation

Abstract The effect of the Big Island of Hawai’i on tropical cyclone (TC) track and structure is investigated using the Weather Research and Forecasting (WRF) model. The high (~4000 m) mountains of the Big Island modulate lower-tropospheric flow in such a way that it can influence TCs hundreds of kilometers away from the island. When a TC approaches from the east, the blocking of lower-tropospheric flow leads to a slowing of the TC’s movement. As a TC passes close to the south side of the Big Island, it deviates southward. The TC core convection and winds can become axisymmetric because of the blocking of the stronger northeasterly flow to the north of the storm. The authors hypothesize that this axisymmetrization led to the unexpected eye formation of Hurricane Flossie (2007) just southeast of the Big Island. As a TC moves into the lee (southwest side) of the Big Island, the flow associated with the island wake leads to a track deviated to the right. The Hurricane Dot (1959) simulations suggest that this effect contributed to an observed deviation to the north, which led to eventual Kauai landfall. A greater TC intensity is found in the lee of the Big Island compared to the case without the island, which is primarily attributed to a weakened vertical wind shear associated with the island blocking.

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