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.

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 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 Interannual Variation of the Cold-Season Rainfall Center in the South China Sea

2017 ◽  
Vol 30 (2) ◽  
pp. 669-688 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Jenq-Dar Tsay ◽  
Jun Matsumoto
Keyword(s):  
South China Sea ◽  
Shear Flow ◽  
South China ◽  
Interannual Variation ◽  
Cold Season ◽  
The Philippines ◽  
The South China Sea ◽  
Enso Cycle ◽  
Cold Surge ◽  
China Sea

During 15 November–31 December, a cold-season rainfall center appears in the southern part of the South China Sea (SCS) north of northwestern Borneo and juxtaposed along the southwest–northeast direction with rainfall centers for the Malay Peninsula and the Philippines. This SCS rainfall center also coincides geographically with the SCS surface trough. An effort is made to explore the formation mechanism of this rainfall center. It is primarily formed by the second intensification of heavy rainfall/flood cold surge vortex [CSV(HRF)] through its interaction with a cold surge flow over the SCS trough. Both the SCS rainfall center and the SCS surface trough are located at the easterly flow north of the near-equator trough. Modulated by the interannual variation of the cyclonic shear flow along the near-equator trough in concert with the El Niño–Southern Oscillation (ENSO) cycle, the SCS rainfall center undergoes an interannual variation. The impact of this ENSO cycle is accomplished through the regulation of CSV(HRF) trajectories originating from the Philippines vicinity and Borneo and propagating to different destinations. Rain-producing efficiency determined by the interannual variation of the divergent circulation accompanies the cyclonic shear flow around the near-equator trough in response to this ENSO cycle.

Collaborative Effects of Cold Surge and Tropical Depression–Type Disturbance on Heavy Rainfall in Central Vietnam

2008 ◽  
Vol 136 (9) ◽  
pp. 3275-3287 ◽  
Author(s):  
Satoru Yokoi ◽  
Jun Matsumoto
Keyword(s):  
Heavy Rainfall ◽  
Large Scale ◽  
Lower Troposphere ◽  
Heavy Rainfall Event ◽  
Wind Anomaly ◽  
Southerly Wind ◽  
Cold Surge ◽  
Tropical Depression ◽  
Orographic Rainfall ◽  
Central Vietnam

Abstract This paper reveals synoptic-scale atmospheric conditions over the South China Sea (SCS) that cause heavy rainfall in central Vietnam through case study and composite analyses. The heavy rainfall event discussed in this study occurred on 2–3 November 1999. Precipitation in Hue city (central Vietnam) was more than 1800 mm for these 2 days. Two atmospheric disturbances played key roles in this heavy rainfall. First, a cold surge (CS) northerly wind anomaly in the lower troposphere, originating in northern China near 40°N, propagated southward to reach the northern SCS and then lingered there for a couple of days, resulting in stronger-than-usual northeasterly winds continuously blowing into the Indochina Peninsula against the Annam Range. Second, a southerly wind anomaly over the central SCS, associated with a tropical depression–type disturbance (TDD) in southern Vietnam, seemed to prevent the CS from propagating farther southward. Over the northern SCS, the southerly wind anomaly formed a strong low-level convergence in conjunction with the CS northeasterly wind anomaly, and supplied warm and humid tropical air. These conditions induced by the CS and TDD are favorable for the occurrence of the heavy orographic rainfall in central Vietnam. The TDD can be regarded as a result of a Rossby wave response to a large-scale convective anomaly over the Maritime Continent associated with equatorial intraseasonal variability. Using a 24-yr (1979–2002) reanalysis and surface precipitation datasets, the authors confirm that the coexistence of the CS and TDD is important for the occurrence of heavy precipitation in central Vietnam. In addition, it is observed that CSs without a TDD do not lead to much precipitation.

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 Evaluating the Snow Crystal Size Distribution and Density Assumptions within a Single-Moment Microphysics Scheme

2010 ◽  
Vol 138 (11) ◽  
pp. 4254-4267 ◽  
Author(s):  
Andrew L. Molthan ◽  
Walter A. Petersen ◽  
Stephen W. Nesbitt ◽  
David Hudak
Keyword(s):  
Size Distribution ◽  
Wrf Model ◽  
Terminal Velocity ◽  
Cold Season ◽  
Radiative Properties ◽  
Microphysics Scheme ◽  
Single Moment ◽  
Crystal Diameter ◽  
Forecast Models ◽  
Microphysical Processes

Abstract The Canadian CloudSat/Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) Validation Project (C3VP) was a field campaign designed to obtain aircraft, surface, and radar observations of clouds and precipitation in support of improving the simulation of snowfall and cold season precipitation, their microphysical processes represented within forecast models, and radiative properties relevant to remotely sensed retrievals. During the campaign, a midlatitude cyclone tracked along the U.S.–Canadian border on 22 January 2007, producing an extensive area of snowfall. Observations of ice crystals from this event are used to evaluate the assumptions and physical relationships for the snow category within the Goddard six-class, single-moment microphysics scheme, as implemented within the Weather Research and Forecasting (WRF) model. The WRF model forecast generally reproduced the precipitation and cloud structures sampled by radars and aircraft, permitting a comparison between C3VP observations and model snowfall characteristics. Key snowfall assumptions in the Goddard scheme are an exponential size distribution with fixed intercept and effective bulk density, and the relationship between crystal diameter and terminal velocity. Fixed values for the size distribution intercept and density did not represent the vertical variability of naturally occurring populations of aggregates, and the current diameter and fall speed relationship underestimated terminal velocities for all sizes of crystals.

Characteristics of the atmospheric circulation associated with cold-season heavy rainfall and flooding over a complex terrain region in Greece

2013 ◽  
Vol 115 (1-2) ◽  
pp. 259-279 ◽  
Author(s):  
G. A. Efstathiou ◽  
C. J. Lolis ◽  
N. M. Zoumakis ◽  
P. Kassomenos ◽  
D. Melas
Keyword(s):  
Atmospheric Circulation ◽  
Complex Terrain ◽  
Heavy Rainfall ◽  
Cold Season

Supercell Pre-convective Environments in Spain: a dynamic downscaling of ERA-5 Reanalysis

2021 ◽  
Author(s):  
Carlos Calvo-Sancho ◽  
Yago Martín
Keyword(s):  
Heavy Rainfall ◽  
Dynamical Downscaling ◽  
Weather Conditions ◽  
Cold Season ◽  
Severe Weather ◽  
Strong Wind ◽  
Dynamic Downscaling ◽  
Wind Gusts ◽  
Arw Model ◽  
The Moment

<p>Supercell thunderstorms are often associated with severe weather conditions, such as tornadoes, hail, strong wind gusts, heavy rainfall, and flash-floods, producing damage to populations and assets. The goal of the study is to analyze and improve our understanding of pre-convective environments conducive for supercell development in the different regions of Spain. We use 2014-2020 data from the Spanish Supercell Database (Martin et al., 2020), ERA-5 reanalysis, and a dynamical downscaling with WRF-ARW model to a 9 km spatial resolution to be able to generate sounding-derived parameters at the moment of formation of each supercell. Results indicate that supercells are more common in high values of CAPE and Shear 0-6 Km, but in the south-western of Spain predominates supercells of HSLC (High Shear-Low CAPE) in the cold season.</p>

scholarly journals Synoptic Development of the Hanoi Heavy Rainfall Event of 30–31 October 2008: Multiple-Scale Processes

2012 ◽  
Vol 140 (4) ◽  
pp. 1219-1240 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Ming-Cheng Yen ◽  
Jenq-Dar Tsay ◽  
Nguyen Thi Tan Thanh ◽  
Jordan Alpert
Keyword(s):  
Heavy Rainfall ◽  
Multiple Scale ◽  
The Philippines ◽  
Heavy Rainfall Event ◽  
Small Surface ◽  
Cold Surge ◽  
Zonal Winds ◽  
The Tropics ◽  
North And South ◽  
Surface Vortex

The 30–31 October 2008 Hanoi, Vietnam, heavy rainfall–flood (HRF) event occurred unusually farther north than other Vietnam events. The cause of this event is explored with multiple-scale processes in the context of the midlatitude–tropical interaction. In the midlatitudes, the cold surge linked to the Hanoi event can be traced westward to the leeside cyclogenesis between the Altai Mountains and Tianshan. This cyclone developed into a Bering Sea explosive cyclone later, simultaneously with the occurrence of the Hanoi HRF event. In the tropics, a cold surge vortex formed on 26 October, south of the Philippines, through the interaction of an easterly disturbance, an already existing small surface vortex in the Celebes Sea, and the eastern Asian cold surge flow. This cold surge vortex developed into a cyclone, juxtaposed with the surface high of the cold surge flow, and established a strong moist southeasterly flow from the South China Sea to Hanoi, which helped maintain the HRF event. Spectral analysis of the zonal winds north and south of the Hanoi HRF cyclone and rainfall at Hanoi reveal the existence of three monsoon modes: 30–60, 12–24, and 5 days. The cold surge vortex developed into an HRF cyclone in conjunction with the in-phase constructive interference of the three monsoon modes, while the Hanoi HRF event was hydrologically maintained by the northwestward flux of water vapor into Hanoi by these monsoon modes.

Determination of the Composition of TiNx and TiBxNy Films by AES

1995 ◽  
Vol 50 (7) ◽  
pp. 624-630 ◽  
Author(s):  
M. A. Baker ◽  
J. Haupt ◽  
W. Gissler
Keyword(s):  
Complex Shape ◽  
Peak Height ◽  
Main Peak ◽  
Peak Height Ratio ◽  
Height Ratio ◽  
Peak Intensity Ratio ◽  
Negative Peak ◽  
Peak Intensity ◽  
Second Peak

For the determination of x and y of TiNx and TiBxNy coatings two Auger methods are presented, one circumventing and the other minimising the difficulties arising from the overlap of the KL23L23 and L3M23M23 peaks of N and Ti, respectively. The first method, developed for TiNx coatings, is based on the L3M23M45 valence band peak of Ti which develops a distinct second peak on nitridation, 3.9 eV below the main peak, labelled the L3M23Hybrid peak. After a simple Shirley background correction, a linear dependence of the L3M23Hybrid/L3M23M45 peak height ratio on the N/Ti ratio was found. This allows the determination of the N content of a TiNx compound. For TiBxNy coatings, a more complex shape of the L3M23M45 peak is obtained due to the presence of more than one phase, rendering this peak unusable for quantification. Therefore the N/Ti ratio is obtained from the L3M23M23/L3M23M4, peak intensity ratio for Ti. To minimise influences of the fine structure and improve the accuracy of the method, the negative peak excursions were artificially broadened. The N/Ti ratio so obtained is used in combination with the B concentration determined from the KL23L23 peak of B to yield the Ti-B-N composition.

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