scholarly journals Synoptic and Mesoscale Analysis of Extreme Rainfall Event in Cilacap Meteorological Station, Indonesia on December 7, 2018

2021 ◽  
Vol 5 (2) ◽  
pp. 121-131
Author(s):  
Suwignyo Prasetyo ◽  
Keyword(s):  
Convective Available Potential Energy ◽  
Convective Cloud ◽  
Extreme Rainfall ◽  
Meteorological Station ◽  
Extreme Rainfall Event ◽  
Synoptic Scale ◽  
The North ◽  
Mature Phase ◽  
Long Duration ◽  
Meso Scale

The highest rainfall for the last five years (2016-2020) was recorded at 199.5 mm in twenty-four hours at the Cilacap Meteorological Station. This study examines the dynamics of the atmosphere with a focus on the synoptic scale and the meso scale. This is done because high rainfall with a long duration is usually caused by a wider scale atmospheric circulation than just local convection scale. The rush of cold air masses from the Asian highlands that propagates across the equator is the main cause on the synoptic scale. In addition, the air flow from the south meets the air mass flow from the north right on the island of Java. On the meso scale, numerical simulations have not been able to properly estimate rainfall with values that tend to be underestimated. However, the value of convective available potential energy is high enough to support the growth of convective clouds. Based on himawari-8 satellite imagery, it is clearly observed that the clouds formed due to atmospheric dynamics are meso-scale convective cloud systems with a life span of more than six hours. The cloud growth is quite massive, which is indicated by the cloud top temperature value being lower than -80C in the mature phase. Thus, the resulting rainfall is quite heavy, causing flooding in parts of Cilacap

An Orography-Associated Extreme Rainfall Event during TiMREX: Initiation, Storm Evolution, and Maintenance

2012 ◽  
Vol 140 (8) ◽  
pp. 2555-2574 ◽  
Author(s):  
Weixin Xu ◽  
Edward J. Zipser ◽  
Yi-Leng Chen ◽  
Chuntao Liu ◽  
Yu-Chieng Liou ◽  
...  
Keyword(s):  
Mesoscale Convective System ◽  
Extreme Rainfall ◽  
Cold Pool ◽  
Convective System ◽  
Extreme Rainfall Event ◽  
Long Duration ◽  
Mesoscale System ◽  
Mesoscale Convective ◽  
Storm Evolution ◽  
Temperature Depression

Abstract This study investigates a long-duration mesoscale system with extremely heavy rainfall over southwest Taiwan during the Terrain-influenced Monsoon Rainfall Experiment (TiMREX). This mesoscale convective system develops offshore and stays quasi-stationary over the upstream ocean and southwest coast of Taiwan. New convection keeps developing upstream offshore but decays or dies after moving into the island, dropping the heaviest rain over the upstream ocean and coastal regions. Warm, moist, unstable conditions and a low-level jet (LLJ) are found only over the upstream ocean, while the island of Taiwan is under the control of a weak cold pool. The LLJ is lifted upward at the boundary between the cold pool and LLJ. Most convective clusters supporting the long-lived rainy mesoscale system are initiated and develop along that boundary. The initiation and maintenance is thought to be a “back-building–quasi-stationary” process. The cold pool forms from previous persistent precipitation with a temperature depression of 2°–4°C in the lowest 500 m, while the high terrain in Taiwan is thought to trap the cold pool from spreading or moving. As a result, the orography of Taiwan is “extended” to the upstream ocean and plays an indirect effect on the long-duration mesoscale system.

scholarly journals A Meteorological Analysis of the 2013 Alberta Flood: Antecedent Large-Scale Flow Pattern and Synoptic–Dynamic Characteristics

2015 ◽  
Vol 143 (7) ◽  
pp. 2817-2841 ◽  
Author(s):  
Shawn M. Milrad ◽  
John R. Gyakum ◽  
Eyad H. Atallah
Keyword(s):  
Rossby Wave ◽  
North Pacific ◽  
Extreme Rainfall ◽  
Flash Floods ◽  
Rainfall Event ◽  
Extreme Rainfall Event ◽  
Front Range ◽  
The North ◽  
The North Pacific ◽  
Meteorological Analysis

Abstract The 19–21 June 2013 Alberta flood was the costliest (CAD $6 billion) natural disaster in Canadian history. The flood was caused by a combination of above-normal spring snowmelt in the Canadian Rockies, large antecedent precipitation, and an extreme rainfall event on 19–21 June that produced rainfall totals of 76 mm in Calgary and 91 mm in the foothills. As is typical of flash floods along the Front Range of the Rocky Mountains, rapidly rising streamflow proceeded to move downhill (eastward) into Calgary. A meteorological analysis traces an antecedent Rossby wave train across the North Pacific Ocean, starting with intense baroclinic development over East Asia on 11 June. Subsequently, downstream Rossby wave development occurred across the North Pacific; a 1032-hPa subtropical anticyclone located northeast of Hawaii initiated a southerly atmospheric river into Alaska, which contributed to the development of a cutoff anticyclone over Alaska and a Rex block (ridge to the north, cyclone to the south) in the northeastern North Pacific. Upon breakdown of the Rex block, lee cyclogenesis occurred in Montana and strong easterly upslope flow was initiated in southern Alberta. The extreme rainfall event was produced in association with a combination of quasigeostrophically and orographically forced ascent, which acted to release conditional and convective instability. As in past Front Range flash floods, moisture flux convergence and positive θe advection were collocated with the heavy rainfall. Backward trajectories show that air parcels originated in the northern U.S. plains, suggesting that evapotranspiration from the local land surface may have acted as a moisture source.

scholarly journals Predictability of Orographic Rainfall Features Over Sylhet Using Nwp Model

2020 ◽  
Vol 11 (2) ◽  
pp. 61-73
Author(s):  
Md Omar Faruq ◽  
MAK Mallik ◽  
MAM Chowdhury ◽  
MAE Akhter ◽  
M Arif Hossain
Keyword(s):  
Convective Available Potential Energy ◽  
Wrf Model ◽  
Tropical Rainfall Measuring Mission ◽  
Extreme Rainfall ◽  
Horizontal Resolution ◽  
Physical Factors ◽  
Microphysics Scheme ◽  
Flow Vorticity ◽  
The North ◽  
Orographic Rainfall

Topography and orography are two physical factors which produce high impact rainfall over the North-eastern part of Bangladesh. To predict the orographic rainfall of 29 March 2017 over Sylhet, Bangladesh an attempt has been performed using Weather Research and Forecasting (WRF) model. The model has been run in a single domain of 10 km horizontal resolution for 48-h and 72-h using six hourly global final datasets from 0000 UTC of each initial day of the event as initial and lateral boundary conditions with NSSL 2-moment microphysics scheme, Kain–Fritsch cumulous scheme and Yonsei University Planetary Boundary Layer (PBL) scheme. The model outputs such as sea level pressure, wind flow, vorticity, wind shear, humidity, Convective Available Potential Energy (CAPE), Convective Inhibition, Lifted Index, K-index, Total Total Index and rainfall have been analyzed. The model predicted weather parameters were visualized by Grid Analysis and Display System (GrADS) and Geographic Information System (GIS) software and validated with observed data of Bangladesh Meteorological Department (BMD), Tropical Rainfall Measuring Mission (TRMM) and European Centre for Medium-Range Weather Forecasts (ECMRWF) data. The analysis determines that the CAPE of magnitude 800- 1000 JKg-1, positive vorticity of (6-10) ×10-5s-1 and relative humidity of 80-100% up to 500-400 hPa levels are accountable for the happening of the orographic extreme rainfall and other parameters are compatible with the observed or theoretical values. This study indicates that the model with an appropriate model set up is capable to predict the orographic precipitation realistically well and can be used for upcoming events. Journal of Engineering Science 11(2), 2020, 61-73

A Multiscale Analysis of a Nocturnal Extreme Rainfall Event of 14 July 2017 in Northeast China

2021 ◽  
Vol 149 (1) ◽  
pp. 173-187
Author(s):  
Gaili Wang ◽  
Da-Lin Zhang ◽  
Jisong Sun
Keyword(s):  
Northeast China ◽  
Global Analysis ◽  
Convective Available Potential Energy ◽  
Inversion Layer ◽  
Extreme Rainfall ◽  
Rainfall Event ◽  
Convergence Zone ◽  
Extreme Rainfall Event ◽  
Hourly Rainfall ◽  
Convective Cells

AbstractA multiscale observational analysis of a nocturnal extreme rainfall event that occurred at Changtu in Northeast China on 14 July 2017 is performed using global analysis, automated surface observations, Doppler radar, rawinsonde, and disdrometer data. Results show that the large-scale environment was characterized by high convective available potential energy and precipitable water, moderate convective inhibition, and a southwesterly low-level jet (LLJ) capped by an inversion layer. The first and subsequent convective cells developed along a quasi-stationary surface convergence zone in a convection-void region of a previously dissipated meso-α-scale convective line. Continuous convective initiation through backbuilding at the western end and the subsequent merging of eastward-moving convective cells led to the formation of a near-zonally oriented meso-β-scale rainband, with reflectivity exceeding 45 dBZ (i.e., convective core intensity). This quasi-stationary rainband was maintained along the convergence zone by the LLJ of warm moist air, aided by local topographical lifting and convectively generated outflows. A maximum hourly rainfall amount of 96 mm occurred during 0200–0300 Beijing standard time as individual convective cores with a melting layer of >55 dBZ reflectivity moved across Changtu with little intermittency. The extreme-rain-producing stage was characterized with near-saturated vertical columns, and rapid number concentration increases of all raindrop sizes. It is concluded that the formation of the meso-β-scale rainband with continuous convective backbuilding, and the subsequent echo-training of convective cores with growing intensity and width as well as significant fallouts of frozen particles accounted for the generation of this extreme rainfall event. This extreme event was enhanced by local topography and the formation of a mesovortex of 20–30 km in diameter.

scholarly journals Numerical Simulations of the 2013 Alberta Flood: Dynamics, Thermodynamics, and the Role of Orography

2017 ◽  
Vol 145 (8) ◽  
pp. 3049-3072 ◽  
Author(s):  
Shawn M. Milrad ◽  
Kelly Lombardo ◽  
Eyad H. Atallah ◽  
John R. Gyakum
Keyword(s):  
Extreme Rainfall ◽  
Rainfall Event ◽  
Extreme Rainfall Event ◽  
Canadian History ◽  
Mesoscale Dynamics ◽  
Physical Mechanisms ◽  
Long Duration ◽  
Surface Cyclone ◽  
Flood Dynamics

The 19–21 June 2013 Alberta flood was the second costliest ($6 billion CAD) natural disaster in Canadian history, trailing only the 2016 Fort McMurray, Alberta, Canada, wildfires. One of the primary drivers was an extreme rainfall event that resulted in 75–150 mm of precipitation in the foothills west of Calgary, Canada. Here, the mesoscale dynamics and thermodynamics that contributed to the extreme rainfall event are elucidated through high-resolution numerical model simulations. In addition, terrain reduction model sensitivity experiments using Gaussian smoothing techniques quantify the importance of orography in producing the extreme rainfall event. It is suggested that the extreme rainfall event was initially characterized by the formation of a surface cyclone on the eastern side of the Canadian Rockies due to quasigeostrophic (QG) mechanisms. Orographic processes and diabatic heating feedbacks maintained the surface cyclone throughout the event, extending the duration of both easterly upslope flow and QG forcing for ascent in the flood region. The long-duration ascent and associated condensational heat release in the flood region vertically redistributed potential vorticity, anchoring and further extending the duration of the surface cyclone, upslope flow, and the rainfall. Although the magnitudes of ascent and precipitation were smaller in 10% and 25% reduced terrain simulations, only a terrain reduction of greater than 25% drastically altered the location and magnitude of the heaviest precipitation and the associated physical mechanisms.

scholarly journals A Synoptic Scale Perspective on Greenland Ice Core δ18O Variability and Related Teleconnection Patterns

Atmosphere ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 294
Author(s):  
Norel Rimbu ◽  
Monica Ionita ◽  
Gerrit Lohmann
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Synoptic Scale ◽  
Local Climate ◽  
Rossby Wave Breaking ◽  
Weather Patterns ◽  
Teleconnection Patterns ◽  
Climate Anomalies ◽  
The North ◽  
Oxygen Isotope Ratios

The variability of stable oxygen isotope ratios (δ18O) from Greenland ice cores is commonly linked to changes in local climate and associated teleconnection patterns. In this respect, in this study we investigate ice core δ18O variability from a synoptic scale perspective to assess the potential of such records as proxies for extreme climate variability and associated weather patterns. We show that positive (negative) δ18O anomalies in three southern and central Greenland ice cores are associated with relatively high (low) Rossby Wave Breaking (RWB) activity in the North Atlantic region. Both cyclonic and anticyclonic RWB patterns associated with high δ18O show filaments of strong moisture transport from the Atlantic Ocean towards Greenland. During such events, warm and wet conditions are recorded over southern, western and central part of Greenland. In the same time the cyclonic and anticyclonic RWB patterns show enhanced southward advection of cold polar air masses on their eastern side, leading to extreme cold conditions over Europe. The association between high δ18O winters in Greenland ice cores and extremely cold winters over Europe is partly explained by the modulation of the RWB frequency by the tropical Atlantic sea surface temperature forcing, as shown in recent modeling studies. We argue that δ18O from Greenland ice cores can be used as a proxy for RWB activity in the Atlantic European region and associated extreme weather and climate anomalies.

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