scholarly journals Impact of the Madden‐Julian Oscillation on extreme precipitation over the western Maritime Continent and Southeast Asia

2021 ◽  
Author(s):  
Nicolas A. Da Silva ◽  
Adrian J. Matthews
Keyword(s):  
Southeast Asia ◽  
Extreme Precipitation ◽  
Madden Julian Oscillation ◽  
Maritime Continent

Influence of the Madden–Julian Oscillation on Forecasts of Extreme Precipitation in the Contiguous United States

2011 ◽  
Vol 139 (2) ◽  
pp. 332-350 ◽  
Author(s):  
Charles Jones ◽  
Jon Gottschalck ◽  
Leila M. V. Carvalho ◽  
Wayne Higgins
Keyword(s):  
United States ◽  
Extreme Precipitation ◽  
Western Hemisphere ◽  
Boreal Winter ◽  
Lead Times ◽  
Madden Julian Oscillation ◽  
Extreme Precipitation Events ◽  
Skill Scores ◽  
Probabilistic Forecasts ◽  
Precipitation Events

Abstract Extreme precipitation events are among the most devastating weather phenomena since they are frequently accompanied by loss of life and property. This study uses reforecasts of the NCEP Climate Forecast System (CFS.v1) to evaluate the skill of nonprobabilistic and probabilistic forecasts of extreme precipitation in the contiguous United States (CONUS) during boreal winter for lead times up to two weeks. The CFS model realistically simulates the spatial patterns of extreme precipitation events over the CONUS, although the magnitudes of the extremes in the model are much larger than in the observations. Heidke skill scores (HSS) for forecasts of extreme precipitation at the 75th and 90th percentiles showed that the CFS model has good skill at week 1 and modest skill at week 2. Forecast skill is usually higher when the Madden–Julian oscillation (MJO) is active and has enhanced convection occurring over the Western Hemisphere, Africa, and/or the western Indian Ocean than in quiescent periods. HSS greater than 0.1 extends to lead times of up to two weeks in these situations. Approximately 10%–30% of the CONUS has HSS greater than 0.1 at lead times of 1–14 days when the MJO is active. Probabilistic forecasts for extreme precipitation events at the 75th percentile show improvements over climatology of 0%–40% at 1-day lead and 0%–5% at 7-day leads. The CFS has better skill in forecasting severe extremes (i.e., events exceeding the 90th percentile) at longer leads than moderate extremes (75th percentile). Improvements over climatology between 10% and 30% at leads of 3 days are observed over several areas across the CONUS—especially in California and in the Midwest.

Annual Cycle of Southeast Asia—Maritime Continent Rainfall and the Asymmetric Monsoon Transition

2005 ◽  
Vol 18 (2) ◽  
pp. 287-301 ◽  
Author(s):  
C-P. Chang ◽  
Zhuo Wang ◽  
John McBride ◽  
Ching-Hwang Liu
Keyword(s):  
Southeast Asia ◽  
Summer Monsoon ◽  
Annual Cycle ◽  
Asian Summer Monsoon ◽  
Small Region ◽  
Winter Monsoon ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Maritime Continent ◽  
Asian Summer

Abstract In general, the Bay of Bengal, Indochina Peninsula, and Philippines are in the Asian summer monsoon regime while the Maritime Continent experiences a wet monsoon during boreal winter and a dry season during boreal summer. However, the complex distribution of land, sea, and terrain results in significant local variations of the annual cycle. This work uses historical station rainfall data to classify the annual cycles of rainfall over land areas, the TRMM rainfall measurements to identify the monsoon regimes of the four seasons in all of Southeast Asia, and the QuikSCAT winds to study the causes of the variations. The annual cycle is dominated largely by interactions between the complex terrain and a simple annual reversal of the surface monsoonal winds throughout all monsoon regions from the Indian Ocean to the South China Sea and the equatorial western Pacific. The semiannual cycle is comparable in magnitude to the annual cycle over parts of the equatorial landmasses, but only a very small region reflects the twice-yearly crossing of the sun. Most of the semiannual cycle appears to be due to the influence of both the summer and the winter monsoon in the western part of the Maritime Continent where the annual cycle maximum occurs in fall. Analysis of the TRMM data reveals a structure whereby the boreal summer and winter monsoon rainfall regimes intertwine across the equator and both are strongly affected by the wind–terrain interaction. In particular, the boreal winter regime extends far northward along the eastern flanks of the major island groups and landmasses. A hypothesis is presented to explain the asymmetric seasonal march in which the maximum convection follows a gradual southeastward progression path from the Asian summer monsoon to the Asian winter monsoon but experiences a sudden transition in the reverse. The hypothesis is based on the redistribution of mass between land and ocean areas during spring and fall that results from different land–ocean thermal memories. This mass redistribution between the two transition seasons produces sea level patterns leading to asymmetric wind–terrain interactions throughout the region, and a low-level divergence asymmetry in the region that promotes the southward march of maximum convection during boreal fall but opposes the northward march during boreal spring.

scholarly journals Detecting and Tracking Coastal Precipitation in the Tropics: Methods and Insights into Multiscale Variability of Tropical Precipitation

2020 ◽  
Vol 33 (15) ◽  
pp. 6689-6705
Author(s):  
David Coppin ◽  
Gilles Bellon ◽  
Alexander Pletzer ◽  
Chris Scott
Keyword(s):  
Diurnal Cycle ◽  
Large Scale ◽  
Madden Julian Oscillation ◽  
Maritime Continent ◽  
Total Rainfall ◽  
Tropical Precipitation ◽  
Precipitation Estimates ◽  
Summer Hemisphere ◽  
The Tropics ◽  
Climate Prediction Center

AbstractWe propose an algorithm to detect and track coastal precipitation systems and we apply it to 18 years of the high-resolution (8 km and 30 min) Climate Prediction Center CMORPH precipitation estimates in the tropics. Coastal precipitation in the Maritime Continent and Central America contributes to up to 80% of the total rainfall. It also contributes strongly to the diurnal cycle over land with the largest contribution from systems lasting between 6 and 12 h and contributions from longer-lived systems peaking later in the day. While the diurnal cycle of coastal precipitation is more intense over land in the summer hemisphere, its timing is independent of seasons over both land and ocean because the relative contributions from systems of different lifespans are insensitive to the seasonal cycle. We investigate the hypothesis that coastal precipitation is enhanced prior to the arrival of the Madden–Julian oscillation (MJO) envelope over the Maritime Continent. Our results support this hypothesis and show that, when considering only coastal precipitation, the diurnal cycle appears reinforced even earlier over islands than previously reported. We discuss the respective roles of coastal and large-scale precipitation in the propagation of the MJO over the Maritime Continent. We also document a shift in diurnal cycle with the phases of the MJO, which results from changes in the relative contributions of short-lived versus long-lived coastal systems.

scholarly journals Role of Maritime Continent Convection during the Preconditioning Stage of the Madden-Julian Oscillation Observed in CINDY2011/DYNAMO

2015 ◽  
Vol 93A (0) ◽  
pp. 101-114 ◽  
Author(s):  
Hisayuki KUBOTA ◽  
Kunio YONEYAMA ◽  
Jun-Ichi HAMADA ◽  
Peiming WU ◽  
Agus SUDARYANTO ◽  
...  
Keyword(s):  
Madden Julian Oscillation ◽  
Maritime Continent

scholarly journals Large-Scale Environmental Characteristics of MJOs that Strengthen and Weaken over the Maritime Continent

2018 ◽  
Vol 31 (14) ◽  
pp. 5731-5748 ◽  
Author(s):  
Casey D. Burleyson ◽  
Samson M. Hagos ◽  
Zhe Feng ◽  
Brandon W. J. Kerns ◽  
Daehyun Kim
Keyword(s):  
Seasonal Cycle ◽  
Large Scale ◽  
Longwave Radiation ◽  
Sea Surface ◽  
Madden Julian Oscillation ◽  
Moist Static Energy ◽  
Maritime Continent ◽  
New Finding ◽  
Field Campaigns ◽  
Static Energy

Abstract The characteristics of Madden–Julian oscillation (MJO) events that strengthen and weaken over the Maritime Continent (MC) are examined. The real-time multivariate MJO (RMM) index is used to assess changes in global MJO amplitude over the MC. The MJO weakens at least twice as often as it strengthens over the MC, with weakening MJOs being twice as likely during El Niño compared to La Niña years and the reverse for strengthening events. MJO weakening shows a pronounced seasonal cycle that has not been previously documented. During the Northern Hemisphere (NH) summer and fall the RMM index can strengthen over the MC. MJOs that approach the MC during the NH winter typically weaken according to the RMM index. This seasonal cycle corresponds to whether the MJO crosses the MC primarily north or south of the equator. Because of the seasonal cycle, weakening MJOs are characterized by positive sea surface temperature and moist-static energy anomalies in the Southern Hemisphere (SH) of the MC compared to strengthening events. Analysis of the outgoing longwave radiation (OLR) MJO index (OMI) shows that MJO precipitation weakens when it crosses the MC along the equator. A possible explanation of this based on previous results is that the MJO encounters more landmasses and taller mountains when crossing along the equator or in the SH. The new finding of a seasonal cycle in MJO weakening over the MC highlights the importance of sampling MJOs throughout the year in future field campaigns designed to study MJO–MC interactions.

scholarly journals Impacts of the Tropical Pacific–Indian Ocean Associated Mode on Madden–Julian Oscillation over the Maritime Continent in Boreal Winter

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1049
Author(s):  
Xin Li ◽  
Ming Yin ◽  
Xiong Chen ◽  
Minghao Yang ◽  
Fei Xia ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Kinetic Energy ◽  
Tropical Pacific ◽  
Western Pacific ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Madden Julian Oscillation ◽  
Maritime Continent ◽  
The Western Pacific ◽  
The Tropical Pacific

Based on the observation and reanalysis data, the relationship between the Madden–Julian Oscillation (MJO) over the Maritime Continent (MC) and the tropical Pacific–Indian Ocean associated mode was analyzed. The results showed that the MJO over the MC region (95°–150° E, 10° S–10° N) (referred to as the MC–MJO) possesses prominent interannual and interdecadal variations and seasonally “phase-locked” features. MC–MJO is strongest in the boreal winter and weakest in the boreal summer. Winter MC–MJO kinetic energy variation has significant relationships with the El Niño–Southern Oscillation (ENSO) in winter and the Indian Ocean Dipole (IOD) in autumn, but it correlates better with the tropical Pacific–Indian Ocean associated mode (PIOAM). The correlation coefficient between the winter MC–MJO kinetic energy index and the autumn PIOAM index is as high as −0.5. This means that when the positive (negative) autumn PIOAM anomaly strengthens, the MJO kinetic energy over the winter MC region weakens (strengthens). However, the correlation between the MC–MJO convection and PIOAM in winter is significantly weaker. The propagation of MJO over the Maritime Continent differs significantly in the contrast phases of PIOAM. During the positive phase of the PIOAM, the eastward propagation of the winter MJO kinetic energy always fails to move across the MC region and cannot enter the western Pacific. However, during the negative phase of the PIOAM, the anomalies of MJO kinetic energy over the MC is not significantly weakened, and MJO can propagate farther eastward and enter the western Pacific. It should be noted that MJO convection is more likely to extend to the western Pacific in the positive phases of PIOAM than in the negative phases. This is significant different with the propagation of the MJO kinetic energy.

scholarly journals Haze in Singapore – Source Attribution of Biomass Burning from Southeast Asia

2018 ◽  
Author(s):  
Ayoe Buus Hansen ◽  
Wei Ming Chong ◽  
Emma Kendall ◽  
Boon Ning Chew ◽  
Christopher Gan ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Southeast Asia ◽  
Biomass Burning ◽  
Dispersion Model ◽  
Source Region ◽  
Weather Conditions ◽  
Peninsular Malaysia ◽  
Source Attribution ◽  
Maritime Continent ◽  
Source Regions

Abstract. This paper presents a study of haze in Singapore caused by biomass burning in Southeast Asia over the six year period from 2010 to 2015, using the Lagrangian dispersion model, NAME. The major contributing source regions are shown to be Riau, Peninsular Malaysia, South Sumatra, and Central and West Kalimantan. However, we see differences in haze concentrations and variation in the relative contributions from the various source regions between monitoring stations across Singapore, as well as on an inter-annual timescale. These results challenge the current popular assumption that haze in Singapore is dominated by emissions/burning from only Indonesia. It is shown that Peninsular Malaysia is a large source for the Maritime Continent off-season biomass burning impact on Singapore. As should be expected, the relatively stronger southeast monsoonal winds that coincide with increased biomass burning activities in the Maritime Continent create the main haze season from August to October (ASO), which brings particulate matter from several and varying source regions to Singapore. In contrast, atypical haze episodes in Singapore are characterised by atypical weather conditions, ideal for biomass burning, and emissions dominated by a single source region (for each event). The two most recent atypical haze events in mid 2013 and early 2014 have different source regions, whereas a different set of five regions dominate as major contributing source regions for most of the recent ASO haze seasons. Haze in Singapore varies across year, season, and location it is influenced by local and regional weather, climate, and regional burning. The study shows that even across small scales, such as in Singapore, variation in local meteorology can impact concentrations of particulate matter significantly, and emphasises the importance of the scale of modelling both spatially and temporally.

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