scholarly journals Impacts of Boreal Winter Monsoon Cold Surges and the Interaction with MJO on Southeast Asia Rainfall

2017 ◽  
Vol 30 (11) ◽  
pp. 4267-4281 ◽  
Author(s):  
See Yee Lim ◽  
Charline Marzin ◽  
Prince Xavier ◽  
Chih-Pei Chang ◽  
Bertrand Timbal
Keyword(s):  
Southeast Asia ◽  
Large Scale ◽  
Winter Season ◽  
Equatorial Indian Ocean ◽  
Extreme Rainfall ◽  
Windward Side ◽  
Boreal Winter ◽  
Eastern Equatorial Indian Ocean ◽  
Cold Surges ◽  
Dynamic Structures

Abstract TRMM rainfall data from 1998–2012 are used to study the impacts and interactions of cold surges (CSs) and the Madden–Julian oscillation (MJO) on rainfall over Southeast Asia during the boreal winter season from November to February. CSs are identified using a new large-scale index. The frequencies of occurrences of these two large-scale events are comparable (about 20% of the days each), but the spatial pattern of impacts show differences resulting from the interactions of the general flow with the complex orography of the region. The largest impact of CSs occurs in and around the southern South China Sea as a result of increased low-level convergence on the windward side of the terrain and increased shear vorticity off Borneo that enhances the Borneo vortex. The largest impact of the MJO is in the eastern equatorial Indian Ocean, sheltered from CSs by Sumatra. In general CSs are significantly more likely to trigger extreme rainfall. When both systems are present, the rainfall pattern is mainly controlled by the CSs. However, the MJO makes the environment more favorable for convection by moistening the atmosphere and facilitating conditional instability, resulting in a significant increased rainfall response compared to CSs alone. In addition to the interactions of the two systems in convection, this study confirms a previously identified mechanism in which the MJO may reduce CS frequency through opposing dynamic structures.

Subseasonal forecasts of the northern Queensland floods of February 2019: Causes and forecast evaluation

2021 ◽  
Author(s):  
Wayne Yuan-Huai Tsai ◽  
Mong-Ming Lu ◽  
Chung-Hsiung Sui ◽  
Yin-Min Cho
Keyword(s):  
Large Scale ◽  
Rossby Waves ◽  
Austral Summer ◽  
Extreme Rainfall ◽  
Circulation Pattern ◽  
Precipitation Event ◽  
Boreal Winter ◽  
Daily Precipitation Data ◽  
Strong Winds ◽  
Equatorial Rossby Waves

<p>During the austral summer 2018/19, devastating floods occurred over northeast Australia that killed approximately 625,000 head of cattle and inundated over 3000 homes in Townsville. This disastrous event was attributed to a quasi-stationary monsoon depression over northeast Australia and the convection associated with MJO over the western Pacific (Cowan et al. 2019). We found that the unusual rainfall was a record-breaking subseasonal peak rainfall event (SPRE) based on the CMORPH daily precipitation data since1998 (Xie et al. 2017). The SPRE is defined as the highest 15-day accumulative rainfall in the running 90-day windows (Tsai et al. 2020). Results of observational data analysis over the recent 21 years (1998~2020) of ERA-interim, OLR, and CMORPH datasets suggest that the northeastern Australian SPREs can be influenced by multiple large-scale drivers, in particular the MJO and equatorial Rossby waves. The occurrence time of the SPRE is associated with MJO activity, while the mean rainfall intensity is more closely associated with the equatorial Rossby waves. The circulation pattern of the SPREs can also be influenced by the equatorial Rossby waves. Using the hindcast data in S2S database we found that the models can capture the SPREs up to one week of the lead times. Characteristics of the activities of MJO and equatorial Rossby waves over the Indonesia-Australia region and their implication to the extended-range SPRE predictability will be discussed.</p><p><strong>Key words: </strong>S2S prediction, Australian summer monsoon, subseasonal peak precipitation event, extreme rainfall</p><p><strong>References:</strong></p><p>Cowan, T., Wheeler, M.C., Alves, O., Narsey, S., de Burgh-Day, C., Griffiths, M., Jarvis, C., Cobon, D.H., Hawcroft, M.K., 2019. Forecasting the extreme rainfall, low tempera- tures, and strong winds associated with the northern Queensland floods of February 2019. Weather Clim. Extremes 26 (100), 232. https://doi.org/10.1016/j.wace.2019. 100232.</p><p>Tsai, W. Y.-H., M.-M. Lu, C.-H. Sui, and P.-H. Lin, 2020: MJO and CCEW Modulation on South China Sea and Maritime Continent Boreal Winter Subseasonal Peak Precipitation. Terr. Atmos. Oceanic Sci., DOI: 10.3319/TAO.2019.10.28.01</p><p>Xie, P., R. Joyce, S. Wu, S. Yoo, Y. Yarosh, F. Sun, and R. Lin, 2017: Reprocessed, Bias-Corrected CMORPH Global High-Resolution Precipitation Estimates from 1998. J. Hydrometeor., 18, 1617–1641, https://doi.org/10.1175/JHM-D-16-0168.1</p>

scholarly journals Recent trends in daily rainfall extremes over Montenegro (1951–2010)

2015 ◽  
Vol 15 (9) ◽  
pp. 2069-2077 ◽  
Author(s):  
D. Burić ◽  
J. Luković ◽  
B. Bajat ◽  
M. Kilibarda ◽  
N. Živković
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Large Scale ◽  
Winter Season ◽  
Daily Rainfall ◽  
Extreme Rainfall ◽  
Intense Rainfall ◽  
The North ◽  
Rainfall Extremes ◽  
The North Atlantic Oscillation

Abstract. More intense rainfall may cause a range of negative impacts upon society and the environment. In this study we analysed trends in extreme ETCCDI (Expert Team on Climate Change Detection and Indices) rainfall indices in Montenegro for the period between 1951 and 2010. Montenegro has been poorly studied in terms of rainfall extremes, yet it contains the wettest Mediterranean region known as Krivošije. Several indices of precipitation extremes were assessed including the number of dry days and rainfall totals in order to identify trends and possible changes. A spatial pattern relationship between extreme rainfall indices and the North Atlantic Oscillation has also been examined. The results generally suggest that the number of days with precipitation decreased while rainfall intensity increased, particularly in south-western parts of the country. A slight tendency towards intense rainfall events is suggested. The examined rainfall indices and North Atlantic Oscillation over Montenegro seemed to be directly linked to changes in one of the major large-scale circulation modes such as the NAO pattern that is particularly evident during the winter season.

scholarly journals Impacts of the Madden-Julian Oscillation (MJO) on rainfall in Sri Lanka

MAUSAM ◽  
2021 ◽  
Vol 71 (3) ◽  
pp. 405-422
Author(s):  
JAYAWARDENA I M SHIROMANI PRIYANTHIKA ◽  
WHEELER MATTHEW C ◽  
SUMATHIPALA W L ◽  
BASNAYAKE B R S B
Keyword(s):  
Sri Lanka ◽  
Large Scale ◽  
Daily Rainfall ◽  
Extreme Rainfall ◽  
Southwest Monsoon ◽  
Boreal Winter ◽  
Northeast Monsoon ◽  
Madden Julian Oscillation ◽  
Extreme Rainfall Events ◽  
Rainfall Events

The influence of the Madden Julian Oscillation (MJO) on rainfall in Sri Lanka (SL) is examined based on 30 years of daily station data from 1981-2010. Composites are constructed for each of the eight phases of the MJO defined with the Real-time Multivariate MJO (RMM) index, using daily rainfall data from 44 stations over SL for four climatic seasons and comparing to similar results from a satellite-based rainfall product. Composites of lower tropospheric wind and convective anomaly are also investigated in order to examine how the local rainfall anomalies are associated with large-scale circulations. The greatest impact of the MJO on rainfall over SL occurs in the Second Inter-Monsoon (SIM) and Southwest Monsoon (SWM) seasons. Enhanced rainfall generally occurs over SL during RMM phases 2 and 3 when the MJO convective envelop is located in the Indian Ocean and conversely suppressed rainfall in phases 6 and 7. This rainfall impact is due to the direct influence of the MJO’s tropical convective anomalies and associated low-level circulations in the vicinity of SL. In contrast, the MJO influence during the Northeast Monsoon (NEM) season is slightly less than during the SWM and SIM seasons as a result of the southward shift of the MJO convective envelop during boreal winter. Occurrence of extreme rainfall events is most frequent during phase 2 in First Inter-Monsoon (FIM) phases 2 and 3 in SWM, phases 1, 2 and 3 in SIM and phases 2 and 3 in NEM seasons. The analysis of this study provides a useful reference of when and where the MJO has significant impacts on rainfall as well as extreme rainfall events during four climatic seasons in SL. This information can be used along with accurately predicted MJO phase by dynamical or statistical models, to improve extended range forecasting in SL.

scholarly journals The Impact of Trends in the Large Scale Atmospheric Circulation on Mediterranean Surface Turbulent Heat Fluxes

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Joy Romanski ◽  
Sultan Hameed
Keyword(s):  
Latent Heat ◽  
Large Scale ◽  
Winter Season ◽  
Teleconnection Pattern ◽  
Heat Fluxes ◽  
Sea Surface ◽  
Boreal Winter ◽  
Turbulent Heat ◽  
Azores High ◽  
The Impact

Interannual variations of latent heat fluxes (LHF) and sensible heat fluxes (SHF) over the Mediterranean for the boreal winter season (DJF) show positive trends during 1958–2011. Using reanalysis and satellite-based products, the variability and trends in the heat fluxes are compared with variations in three atmospheric teleconnection patterns: the North Atlantic Oscillation (NAO), the pressure and position of the Azores High (AH), and the East Atlantic-West Russia teleconnection pattern (EAWR). Comparison of correlations between the heat fluxes and teleconnections, along with analysis of composites of surface temperature, humidity, and wind fields for different teleconnection states, demonstrates that the AH explains the heat flux changes more successfully than NAO and EAWR. Trends in pressure and longitude of the Azores High show a strengthening and an eastward shift. Variations of the Azores High occur along an axis defined by lower pressure and westward location at one extreme and higher pressure and eastward location at the other extreme. The shift of the AH from predominance of the low/west state to the high/east state induces trends in Mediterranean Sea surface winds, temperature, and moisture. These, combined with sea surface warming trends, produce trends in wintertime sensible and latent heat fluxes.

scholarly journals Large-scale extreme rainfall producing synoptic systems of the Indian summer monsoon

2020 ◽  
Author(s):  
Akshaya C Nikumbh ◽  
Arindam Chakraborty ◽  
G S Bhat ◽  
Dargan M. W. Frierson
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Large Scale ◽  
Extreme Rainfall

scholarly journals Development of a Global Fire Weather Database

2015 ◽  
Vol 15 (6) ◽  
pp. 1407-1423 ◽  
Author(s):  
R. D. Field ◽  
A. C. Spessa ◽  
N. A. Aziz ◽  
A. Camia ◽  
A. Cantin ◽  
...  
Keyword(s):  
Southeast Asia ◽  
Large Scale ◽  
Prediction Models ◽  
Dry Season ◽  
Weather Data ◽  
Data Sets ◽  
Fire Weather ◽  
Fire Weather Index ◽  
Mato Grosso ◽  
Global Database

Abstract. The Canadian Forest Fire Weather Index (FWI) System is the mostly widely used fire danger rating system in the world. We have developed a global database of daily FWI System calculations, beginning in 1980, called the Global Fire WEather Database (GFWED) gridded to a spatial resolution of 0.5° latitude by 2/3° longitude. Input weather data were obtained from the NASA Modern Era Retrospective-Analysis for Research and Applications (MERRA), and two different estimates of daily precipitation from rain gauges over land. FWI System Drought Code calculations from the gridded data sets were compared to calculations from individual weather station data for a representative set of 48 stations in North, Central and South America, Europe, Russia, Southeast Asia and Australia. Agreement between gridded calculations and the station-based calculations tended to be most different at low latitudes for strictly MERRA-based calculations. Strong biases could be seen in either direction: MERRA DC over the Mato Grosso in Brazil reached unrealistically high values exceeding DC = 1500 during the dry season but was too low over Southeast Asia during the dry season. These biases are consistent with those previously identified in MERRA's precipitation, and they reinforce the need to consider alternative sources of precipitation data. GFWED can be used for analyzing historical relationships between fire weather and fire activity at continental and global scales, in identifying large-scale atmosphere–ocean controls on fire weather, and calibration of FWI-based fire prediction models.

scholarly journals Large-scale transport of PM2.5 in the lower troposphere during winter cold surges in China

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Jianjun Wang ◽  
Meigen Zhang ◽  
Xiaolin Bai ◽  
Hongjian Tan ◽  
Sabrina Li ◽  
...  
Keyword(s):  
Large Scale ◽  
Lower Troposphere ◽  
Winter Cold ◽  
Cold Surges

scholarly journals Mercury distribution in the upper troposphere and lower most stratosphere according to measurements by the IAGOS-CARIBIC observatory, 2014–2016

2018 ◽  
Author(s):  
Franz Slemr ◽  
Andreas Weigelt ◽  
Ralf Ebinghaus ◽  
Johannes Bieser ◽  
Carl A. M. Brenninkmeijer ◽  
...  
Keyword(s):  
Large Scale ◽  
Total Mercury ◽  
Trace Gases ◽  
Boreal Winter ◽  
Signal Integration ◽  
Upper Troposphere ◽  
Cloud Scavenging ◽  
Passenger Aircraft ◽  
North And South America ◽  
North And South

Abstract. Mercury was measured onboard the IAGOS-CARIBIC passenger aircraft since May 2005 until February 2016 during nearly monthly sequences of mostly four intercontinental flights from Germany to destinations in North and South America, Africa, and South and East Asia. Most of these mercury data were obtained using an internal default signal integration procedure of the Tekran instrument but since April 2014 more precise and accurate data were obtained using post-flight manual integration of the instrument raw signal. In this paper we use the latter data. Elevated upper tropospheric total mercury (TM) concentrations due to large scale biomass burning were observed in the upper troposphere (UT) at the equator and southern latitudes during the flights to Latin America and South Africa in boreal autumn (SON) and boreal winter (DJF). TM concentrations in the lowermost stratosphere (LMS) decrease with altitude above the thermal tropopause but the gradient is less steep than reported before. Seasonal variation of the vertical TM distribution in the UT and LMS is similar to that of other trace gases with surface sources and stratospheric sinks. Using speciation experiments, we show that nearly identical TM and gaseous elementary mercury (GEM) concentrations exist at and below the tropopause. Above the thermal tropopause GEM concentrations are almost always smaller than those of TM and the TM – GEM (i.e. Hg2+) difference increases up to ~ 40 % of TM at ~ 2 km and more above the thermal tropopause. Correlations with N2O as a reference tracer suggest stratospheric lifetimes of 72 ± 37 and 74 ± 27 yr for TM and GEM, respectively, comparable to the stratospheric lifetime of COS. This coincidence, combined with pieces of evidence from us and other researchers, corroborates the hypothesis that Hg2+ formed by oxidation in the stratosphere attaches to sulfate particles formed mainly by oxidation of COS and is removed with them from the stratosphere by air mass exchange, gravitational sedimentation, and cloud scavenging processes.

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