scholarly journals The Winter Rainfall of Malaysia

2013 ◽  
Vol 26 (3) ◽  
pp. 936-958 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Jenq-Dar Tsay ◽  
Ming-Cheng Yen ◽  
Jun Matsumoto
Keyword(s):  
South China Sea ◽  
Heavy Rainfall ◽  
Peninsular Malaysia ◽  
Rainfall Amount ◽  
Severe Weather ◽  
Winter Rainfall ◽  
Maximum Rainfall ◽  
Cold Surge ◽  
Dynamic Analyses ◽  
Rainfall Flood

Abstract Malaysia is geographically separated into Peninsular Malaysia and west Borneo. The rainfall maximum in the former region occurs during November–December, whereas that in the latter region occurs during December–February. This difference of maximum rainfall period indicates that the formation mechanism is different for the rainfall centers in these two parts of Malaysia. Since rainfall is primarily produced by severe weather systems, the formation of a climatological rainfall center is explored through synoptic activity and the rainfall amount of this center is estimated through contributions by rain-producing disturbances. The major cause of the rainfall maximum of Peninsular Malaysia is cold surge vortices (CSVs) and heavy rainfall/flood (HRF) events propagating from the Philippine area and Borneo. In contrast, the major cause of the rainfall maximum of Borneo is these rain-producing disturbances trapped in Borneo. Disturbances of the former group are formed by the cold surge flows of the Philippine Sea type, whereas disturbances of the latter group are formed by cold surge flows of the South China Sea (SCS) type. The population of HRF events is about one-fourth of the rain-producing disturbances in both Peninsular Malaysia and Borneo, but they produce less than ~60% rainfall for these two regions. It is revealed from the synoptic and dynamic analyses that the major Borneo rain-producing disturbances propagate westward before December by strong tropical easterlies, but they are trapped after December by strong northeasterlies of the SCS-type cold surge flow.

scholarly journals Value addition in district level dynamical forecast during monsoon depressions and storms

MAUSAM ◽  
2021 ◽  
Vol 58 (1) ◽  
pp. 1-8
Author(s):  
O. P. SINGH ◽  
B. LAL ◽  
ONKARI PRASAD
Keyword(s):  
Sea Level ◽  
Heavy Rainfall ◽  
Rainfall Amount ◽  
District Level ◽  
Value Addition ◽  
Maximum Rainfall ◽  
Mean Sea Level ◽  
Weather Forecasts ◽  
Medium Range ◽  
Monsoon Depressions

ABSTRACT. The trials of district level forecasts yielded encouraging results during 2005 monsoon. The purpose of this paper is to document the methodology followed in the value addition during the periods of monsoon depressions and storms. The focus is on the use of Mean Sea Level (MSL) positions and the 850 hPa circulation features predicted by different model centres, especially the European Centre for Medium-Range Weather Forecasts (ECMWF). The ECMWF-predicted 72 hr MSL position of the monsoon depression centre was found to be significantly correlated to the actual position of the system and the central location of the realized rainfall zone associated with the system. Even the predicted location of the system at 850 hPa by the ECMWF has been found useful in identifying the districts that received heaviest rainfall associated with the monsoon systems.MM5 and T-80 – predicted locations of the system at 850 hPa yielded lower correlations with the location of the actual rainfall zone associated with the system. As ECMWF – predicted rainfall was not available the rainfall predicted by MM5 and T-80 were used in the computations of the correlations with actual rainfall amounts associated with monsoon depressions and storms. The correlations between MM5 and T-80 – predicted average and maximum rainfall associated with systems and corresponding actual were poor. Though it is not difficult to identify the districts that are likely to be affected by the heavy rainfall associated with monsoon depressions/storms, the prediction of exact rainfall amount for each district (beyond heavy, very heavy or exceptionally heavy categories) is difficult from the model outputs which makes such forecasts a very challenging task. Therefore, the value addition using other inputs such as satellite information, synoptic charts, climatology etc. are very useful in the prediction of rainfall amounts associated with monsoon systems.

scholarly journals Development and Formation Mechanism of the Southeast Asian Winter Heavy Rainfall Events around the South China Sea. Part I: Formation and Propagation of Cold Surge Vortex*

2015 ◽  
Vol 28 (4) ◽  
pp. 1417-1443 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Jenq-Dar Tsay ◽  
Jun Matsumoto ◽  
Jordan Alpert
Keyword(s):  
South China Sea ◽  
South China ◽  
Heavy Rainfall ◽  
The Philippines ◽  
The South China Sea ◽  
The South ◽  
Cold Surge ◽  
China Sea ◽  
Flow Type ◽  
Development Processes

Abstract Examination of the development of cold season heavy rainfall/flood (HRF) events around the South China Sea (SCS) from their parent cold surge vortices (CSVs) shows three new development processes. First, the formation mechanism of the parent CSV of an HRF event [CSV(HRF)] has a preference as to geographic location, flow type of the cold surge inside the SCS, and time of day. The surface trough east of the Philippines, Taiwan, and southern Japan island chain in late fall and the near-equator trough across Borneo in winter facilitate the CSV(HRF) formation in two regions—the vicinity of the Philippines and Borneo. The formation of the Philippine (Borneo) CSV(HRF) occurs at 0600 UTC (0000 UTC) with involvement from the Philippine Sea (PHS)-type (SCS type) of cold surge flow. Second, the flow type of the cold surge determines the CSV(HRF) propagation across the South China Sea. The PHS-type (SCS type) facilitates (hinders) the CSV(HRF) westward propagation. This occurs because the easterly (northerly) flow is greater than (less than) the northerly (easterly) flow at the maximum isotach location of the cold surge flow associated with CSV(HRF) and is centered east of the demarcation line for propagation. This flow-type contrast is substantiated by the vorticity budget analysis for CSV(HRF). The positive 925-hPa vorticity tendency is located west of (coincident with) the 925-hPa vorticity center for the PHS-type (SCS type) of cold surge. Third, the CSV(HRF) development into a HRF event is achieved through multiple interactions of former vortices with sequential cold surges across the South China Sea. The first two CSV(HRF) development processes are reported herein; the last process is presented in Part II.

scholarly journals Development and Formation Mechanism of the Southeast Asian Winter Heavy Rainfall Events around the South China Sea. Part II: Multiple Interactions*

2015 ◽  
Vol 28 (4) ◽  
pp. 1444-1464 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Jenq-Dar Tsay ◽  
Jun Matsumoto
Keyword(s):  
South China Sea ◽  
South China ◽  
Heavy Rainfall ◽  
Cold Season ◽  
The South China Sea ◽  
Northwestern Pacific ◽  
The South ◽  
Cold Surge ◽  
China Sea ◽  
Multiple Interactions

Abstract About 44% of the cold-season heavy rainfall/flood (HRF) events around the South China Sea require six days or longer to develop from the formation time of their parent cold surge vortices (CSVs). Formations for both the parent CSV and HRF event are involved with interactions of the concerned vortices with two different cold surge flows. The occurrence frequency of the East Asian cold surge flow varies from 4.5 to 6 days. The longevous CSVs enable their developments to interact with the second cold surge flows between formations of these CSVs and HRF events. Two requirements for the formation of HRF events are 1) synchronized occurrence of the HRF event and the northwestern Pacific explosive cyclone and 2) simultaneous occurrence of the maximum speeds among westerlies of the northwestern Pacific explosive cyclone and easterlies of the tropical trade winds and the HRF event. These requirements cannot be met by the CSV at its second maximum peak intensity, but the CSV at this stage plays an indispensible role for the formation of the HRF event to make its intensity and rainfall amount larger than those HRF events without this relay intensification. The development of an HRF event through multiple interactions of CSVs with sequential cold surge flows may pose difficulties to numerically simulate/predict the occurrence of these HRF events over the cold-season rainfall centers around the South China Sea.

scholarly journals Forecast Advisory for a Cold-Season Heavy Rainfall/Flood Event That Developed from Multiple Interactions of the Cold-Surge Vortex with Cold-Surge Flows in the South China Sea

2017 ◽  
Vol 32 (3) ◽  
pp. 797-819 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Jenq-Dar Tsay ◽  
Jun Matsumoto ◽  
Jordan Alpert
Keyword(s):  
Heavy Rainfall ◽  
Vortex Formation ◽  
Cold Season ◽  
Life Cycles ◽  
Cold Surge ◽  
Peak Intensity ◽  
Forecast Models ◽  
Population Ratio ◽  
Rainfall Flood ◽  
Second Peak

Abstract The peak intensity occurrence frequency over the life cycles of parent cold-surge vortices (CSVs) for heavy rainfall/flood (HRF) events is classified into two types depending on their life cycles having two or three peak intensities, denoted as HRF2 or HRF3, respectively. The formation of an HRF2 event from its parent CSV(HRF2) formation is ≤5 days, while the formation of an HRF3 event is ≥6 days. The latter group contributes ~57% of the total number of HRF events. As a result of some model constraints, the formation and development of HRF3 events are not well forecasted by the Global Forecast System (GFS) and regional forecast models. The life cycle and second peak intensity for CSV(HRF3) allow for the introduction of a forecast advisory for HRF3 events. Identification of CSVs and two sufficient requirements for the formation and occurrence of HRF events were developed by previous studies. Nevertheless, two new necessary steps are now included in the proposed forecast advisory. The population ratio for CSV(HRF3) and the regular CSV is only about 15%. The occurrence optimum time to for the CSV(HRF3) second peak intensity from this vortex formation is about 3 days 6 h. The GFS forecast over to is utilized to identify CSV(HRF3). Then, the relay of the GFS forecast from the occurrence time of the CSV(HRF3) second peak is used to predict the formation/occurrence of HRF3 events. Six HRF3 events during cold seasons for 2013–16 are used to test the feasibility of this forecast advisory. Results clearly demonstrate this advisory is a success for the forecast of HRF3 events over the entire life cycles of their parent CSV(HRF3)s.

The Bow and Arrow Mesoscale Convective Structure

2013 ◽  
Vol 141 (5) ◽  
pp. 1648-1672 ◽  
Author(s):  
Kelly M. Keene ◽  
Russ S. Schumacher
Keyword(s):  
Heavy Rainfall ◽  
Prediction Models ◽  
Weather Prediction ◽  
Warm Season ◽  
Severe Weather ◽  
Cold Pool ◽  
Horizontal Shear ◽  
Convective Systems ◽  
Wind Speeds ◽  
Bow And Arrow

Abstract The accurate prediction of warm-season convective systems and the heavy rainfall and severe weather associated with them remains a challenge for numerical weather prediction models. This study looks at a circumstance in which quasi-stationary convection forms perpendicular to, and above the cold-pool behind strong bow echoes. The authors refer to this phenomenon as a “bow and arrow” because on radar imagery the two convective lines resemble an archer’s bow and arrow. The “arrow” can produce heavy rainfall and severe weather, extending over hundreds of kilometers. These events are challenging to forecast because they require an accurate forecast of earlier convection and the effects of that convection on the environment. In this study, basic characteristics of 14 events are documented, and observations of 4 events are presented to identify common environmental conditions prior to the development of the back-building convection. Simulations of three cases using the Weather Research and Forecasting Model (WRF) are analyzed in an attempt to understand the mechanisms responsible for initiating and maintaining the convective line. In each case, strong southwesterly flow (inducing warm air advection and gradual isentropic lifting), in addition to directional and speed convergence into the convective arrow appear to contribute to initiation of convection. The linear orientation of the arrow may be associated with a combination of increased wind speeds and horizontal shear in the arrow region. When these ingredients are combined with thermodynamic instability, there appears to be a greater possibility of formation and maintenance of a convective arrow behind a bow echo.

scholarly journals Borneo vortex and meso-scale convective rainfall

2013 ◽  
Vol 13 (8) ◽  
pp. 21079-21124 ◽  
Author(s):  
S. Koseki ◽  
T.-Y. Koh ◽  
C.-K. Teo
Keyword(s):  
South China Sea ◽  
South China ◽  
Convective Rainfall ◽  
Absolute Vorticity ◽  
Wind Pattern ◽  
Cold Surge ◽  
China Sea ◽  
Asian Winter Monsoon ◽  
Budget Analysis ◽  
Vorticity Budget

Abstract. We have investigated how the Borneo vortex develops over the equatorial South China Sea under cold surge conditions in December during the Asian winter monsoon. Composite analysis using reanalysis and satellite datasets has revealed that absolute vorticity and water vapour are transported by strong cold surges from upstream of the South China Sea to around the equator. Rainfall is correspondingly enhanced over the equatorial South China Sea. A semi-idealized experiment reproduced the Borneo vortex over the equatorial South China Sea during a "perpetual" cold surge. The Borneo vortex is manifested as a meso-α cyclone with a comma-shaped rainband in the northeast sector of the cyclone. Vorticity budget analysis showed that the growth of the meso-α cyclone was achieved mainly by vortex stretching. The comma-shaped rainband consists of clusters of meso-β scale rainfall patches. The warm and wet cyclonic southeasterly flow meets with the cold and dry northeasterly surge forming a confluence front in the northeastern sector of the cyclone. Intense upward motion and heavy rainfall result both due to the low-level convergence and the favourable thermodynamic profile at the confluence front. At both meso-α and meso-β scales, the convergence is ultimately caused by the deviatoric strain in the confluence wind pattern but is much enhanced by nonlinear self-enhancement dynamics.

scholarly journals Macrobenthos diversity along the Exclusive Economic Zone of East Coast Peninsular Malaysia

2021 ◽  
Vol 42 (3(SI)) ◽  
pp. 817-823
Author(s):  
B.B. Shafie ◽  
◽  
A. Man ◽  
N.F. Ali ◽  
A.A. Rahim ◽  
...  
Keyword(s):  
South China Sea ◽  
East Coast ◽  
Standing Stock ◽  
Environmental Parameters ◽  
Peninsular Malaysia ◽  
Depth Gradient ◽  
Sunda Shelf ◽  
Faunal Composition ◽  
Western South China Sea ◽  
Abundance And Diversity

Aim: To examine the standing stock of macrobenthos along a depth gradient at regional scales in the Sunda Shelf of Malaysian Economic Exclusive Zone (EEZ). Methodology: Macrobenthos was sampled with a Smith–McIntyre grab at 19 stations on the continental shelf of the South-western South China Sea (east coast of Peninsular Malaysia) within the EEZ and was carried out onboard MV SEAFDEC II in May/June 2016. Results: The faunal composition, abundance, and diversity of species, together with environmental parameters were studied. A total of 10,232 individuals comprising 105 families were identified. The dominant macrobenthic group was Mollusca (55.25%), followed by Annelida (26.80%) and Arthropoda (15.36%), while the Echinodermata and Miscellaneous group recorded 1.13% and 1.43% respectively. Based on Bray-Curtis species similarities, five different sample groups (SGs) were distinguished, which were located in different zones and gradients of EEZ. Interpretation: Variations in the macrobenthic community is significantly associated with depth, temperature, and salinity. Further research should be conducted on other factors that contribute to the diversity of macrobenthos along the east coast of Peninsular Malaysia’s EEZ.

Identification and Synoptic Analysis of the Highest Precipitation Linked to Ars in Iran

2021 ◽  
Vol 3 (2) ◽  
pp. 20-32
Author(s):  
Hassan Lashkari ◽  
Neda Esfandiari ◽  
Abbas Kashani
Keyword(s):  
Water Vapour ◽  
Heavy Rainfall ◽  
Daily Rainfall ◽  
Horn Of Africa ◽  
Maximum Rainfall ◽  
Rainfall Events ◽  
Atmospheric Rivers ◽  
Factors Affecting ◽  
North West ◽  
Integral Data

Atmospheric rivers are long, narrow, concentrated structures of water vapour that are highly associated with rainfall and floods. To identify and introduce the highest rainfall occurring during the presence of atmospheric rivers from November to April (2007-2018) while showing the importance of this phenomenon in creating super heavy rainfall and introducing the areas affected by it, analyzed the synoptic factors affecting them slowly. In order to identify atmospheric rivers, vertical integral data of water vapour flow were used and thresholds were documented on them. The date of occurrence of each atmospheric river with their daily rainfall was examined and ten of the highest rainfall events Station (equivalent to the 95th percentile of maximum rainfall) related to atmospheric rivers was introduced and analyzed. It is found that the South Gram has been directly and indirectly the main source of atmospheric rivers associated with heavy rainfall. The source of most of these atmospheric rivers is at the peak of the Red Sea, the Gulf of Aden and the Horn of Africa. Synonymously, the origins of 7 cases from Atmospheric rivers have been of the Sudanese low pressure and in the remaining three cases have been integrated systems. In Sudanese systems, the predominant structure of the meridional inclination jet and in Integration systems has been oriented. Due to the dominance of a strong upstream current in the vicinity of the highest flux, moisture of heavy convective currents has caused super heavy rainfall and the station with the highest rainfall in the east and North West of the negative omega field or upstream streams.

scholarly journals Individual Rainfall Change Based on Observed Hourly Precipitation Records on the Chinese Loess Plateau from 1983 to 2012

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2268
Author(s):  
Wenbin Ding ◽  
Fei Wang ◽  
Kai Jin ◽  
Jianqiao Han ◽  
Qiang Yu ◽  
...  
Keyword(s):  
Loess Plateau ◽  
Heavy Rainfall ◽  
Rainfall Intensity ◽  
Rainfall Amount ◽  
The Loess Plateau ◽  
Total Rainfall ◽  
Rainfall Events ◽  
Rainfall Duration ◽  
Rainfall Frequency ◽  
Annual Total

The magnitude and spatiotemporal distribution of precipitation are the main drivers of hydrologic and agricultural processes in soil moisture, runoff generation, soil erosion, vegetation growth and agriculture activities on the Loess Plateau (LP). This study detects the spatiotemporal variations of individual rainfall events during a rainy season (RS) from May to September based on the hourly precipitation data measured at 87 stations on the LP from 1983 to 2012. The incidence and contribution rates were calculated for all classes of rainfall duration and intensity to identify the dominant contribution to the rainfall amount and frequency variations. The trend rates of regional mean annual total rainfall amount (ATR) and annual mean rainfall intensity (ARI) were 0.43 mm/year and 0.002 mm/h/year in the RS for 1983–2012, respectively. However, the regional mean annual total rainfall frequency (ARF) and rainfall events (ATE) were −0.27 h/year and −0.11 times/year, respectively. In terms of spatial patterns, an increase in ATR appeared in most areas except for the southwest, while the ARI increased throughout the study region, with particularly higher values in the northwest and southeast. Areas of decreasing ARF occurred mainly in the northwest and central south of the LP, while ATE was found in most areas except for the northeast. Short-duration (≤6 h) and light rainfall events occurred mostly on the LP, accounting for 69.89% and 72.48% of total rainfall events, respectively. Long-duration (≥7 h) and moderate rainfall events contributed to the total rainfall amount by 70.64% and 66.73% of the total rainfall amount, respectively. Rainfall frequency contributed the most to the variations of rainfall amount for light and moderate rainfall events, while rainfall intensity played an important role in heavy rainfall and rainstorms. The variation in rainfall frequency for moderate rainfall, heavy rainfall, and rainstorms is mainly affected by rainfall duration, while rainfall event was identified as a critical factor for light rainfall. The characteristics in rainfall variations on the Loess Plateau revealed in this study can provide useful information for sustainable water resources management and plans.

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