Modulation of Daily Precipitation over Southwest Asia by the Madden–Julian Oscillation

2005 ◽  
Vol 133 (12) ◽  
pp. 3579-3594 ◽  
Author(s):  
Mathew Barlow ◽  
Matthew Wheeler ◽  
Bradfield Lyon ◽  
Heidi Cullen
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Daily Precipitation ◽  
Vertical Motion ◽  
Longwave Radiation ◽  
Reanalysis Data ◽  
Eastern Indian Ocean ◽  
Motion Field ◽  
Madden Julian Oscillation ◽  
Southwest Asia

Abstract Analysis of daily observations shows that wintertime (November–April) precipitation over Southwest Asia is modulated by Madden–Julian oscillation (MJO) activity in the eastern Indian Ocean, with strength comparable to the interannual variability. Daily outgoing longwave radiation (OLR) for 1979–2001 is used to provide a long and consistent, but indirect, estimate of precipitation, and daily records from 13 stations in Afghanistan reporting at least 50% of the time for 1979–85 are used to provide direct, but shorter and irregularly reported, precipitation data. In the station data, for the average of all available stations, there is a 23% increase in daily precipitation relative to the mean when the phase of the MJO is negative (suppressed tropical convection in the eastern Indian Ocean), and a corresponding decrease when the MJO is positive. The distribution of extremes is also affected such that the 10 wettest days all occur during the negative MJO phase. The longer record of OLR data indicates that the effect of the MJO is quite consistent from year to year, with the anomalies averaged over Southwest Asia more negative (indicating more rain) for the negative phase of the MJO for each of the 22 yr in the record. Additionally, in 9 of the 22 yr the average influence of the MJO is larger than the interannual variability (e.g., the relationship results in anomalously wet periods even in dry years and vice versa). Examination of NCEP–NCAR reanalysis data shows that the MJO modifies both the local jet structure and, through changes to the thermodynamic balance, the vertical motion field over Southwest Asia, consistent with the observed modulation of the associated synoptic precipitation. A simple persistence scheme for forecasting the sign of the MJO suggests that the modulation of Southwest Asia precipitation may be predictable for 3-week periods. Finally, analysis of changes in storm evolution in Southwest Asia due to the influence of the MJO shows a large difference in strength as the storms move over Afghanistan, with apparent relevance for the flooding event of 12–13 April 2002.

scholarly journals Structure and Origin of the Quasi-Biweekly Oscillation over the Tropical Indian Ocean in Boreal Spring

2010 ◽  
Vol 67 (6) ◽  
pp. 1965-1982 ◽  
Author(s):  
Min Wen ◽  
Tim Li ◽  
Renhe Zhang ◽  
Yanjun Qi
Keyword(s):  
Boundary Layer ◽  
Indian Ocean ◽  
Vertical Motion ◽  
Longwave Radiation ◽  
Tropical Indian Ocean ◽  
Momentum Equation ◽  
Reanalysis Data ◽  
Triggering Mechanism ◽  
Boreal Spring ◽  
Zonal Momentum

Abstract The structure and evolution features of the quasi-biweekly (10–20 day) oscillation (QBWO) in boreal spring over the tropical Indian Ocean (IO) are investigated using 27-yr daily outgoing longwave radiation (OLR) and the National Centers for Environment Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis data. It is found that a convective disturbance is initiated over the western IO and moves slowly eastward. After passing the central IO, it abruptly jumps into the eastern IO. Meanwhile, the preexisting suppressed convective anomaly in the eastern IO moves poleward in the form of double-cell Rossby gyres. The analysis of vertical circulation shows that a few days prior to the onset of local convection in the eastern equatorial IO an ascending motion appears in the boundary layer. Based on the diagnosis of the zonal momentum equation, a possible boundary layer–triggering mechanism over the eastern equatorial IO is proposed. The cause of the boundary layer convergence and vertical motion is attributed to the free-atmospheric divergence in association with the development of the barotropic wind. It is the downward transport of the background mean easterly momentum by perturbation vertical motion during the suppressed convective phase of the QBWO that leads to the generation of a barotropic easterly—the latter of which further causes the free-atmospheric divergence and, thus, the boundary layer convergence. The result suggests that the local process, rather than the eastward propagation of the disturbance from the western IO, is essential for the phase transition of the QBWO convection over the eastern equatorial IO.

scholarly journals Middle East and Southwest Asia Daily Precipitation Characteristics Associated with the Madden–Julian Oscillation during Boreal Winter

2018 ◽  
Vol 31 (21) ◽  
pp. 8843-8860 ◽  
Author(s):  
Andrew Hoell ◽  
Forest Cannon ◽  
Mathew Barlow
Keyword(s):  
Middle East ◽  
Indian Ocean ◽  
Extreme Precipitation ◽  
Cold Season ◽  
Eastern Indian Ocean ◽  
Boreal Winter ◽  
Monthly Precipitation ◽  
Madden Julian Oscillation ◽  
Southwest Asia ◽  
Precipitation Characteristics

The spatial and temporal evolution of Middle East and southwest Asia (MESW) precipitation characteristics and the associated atmospheric circulation during times in which tropical eastern Indian Ocean precipitation is either enhanced or reduced associated with the Madden–Julian oscillation (MJO) is assessed. Using multiple estimates of both the observed precipitation and the MJO during 1981–2016, the evolution of MESW precipitation characteristics throughout November–April is examined in terms of monthly precipitation accumulation on precipitation days, the number of precipitation days, and the number of extreme precipitation days. MJO phases 2–4, during which eastern Indian Ocean precipitation is enhanced, and MJO phases 6–8, during which eastern Indian Ocean precipitation is reduced, are related, with significant decreases and increases in the number of precipitation days across MESW, respectively. The patterns of precipitation-day changes between MJO phases undergo noteworthy spatial and temporal evolutions across the boreal cold season that are influenced by the interaction between Rossby wave forcing by the MJO and seasonal changes in both the upper-level jet and moisture over the region. During December–January, the changes in precipitation days are found primarily over northern MESW, while during February–March, the changes in precipitation days are found primarily over southern MESW. Although the results identify an important sensitivity in the number of precipitation days over the MESW related to the MJO, the same sensitivity is not apparent in terms of the number of extreme precipitation days and, in particular, the amount of precipitation on a precipitation day.

The impact of diurnal precipitation over Sumatra Island, Indonesia, on synoptic disturbances and its relation to the Madden-Julian Oscillation

2021 ◽  
Author(s):  
Ayako Seiki ◽  
Satoru Yokoi ◽  
Masaki Katsumata
Keyword(s):  
Indian Ocean ◽  
Diurnal Cycle ◽  
Lower Troposphere ◽  
Reanalysis Data ◽  
Eastern Indian Ocean ◽  
Sumatra Island ◽  
The Indian Ocean ◽  
Precipitation Area ◽  
High Precipitation ◽  
The Impact

<p>The impact of diurnal precipitation over Sumatra Island, the Indonesian Maritime Continent (MC), on synoptic disturbances over the eastern Indian Ocean is examined using high-resolution rainfall data from the Global Satellite Mapping of Precipitation project and the Japanese 55-year Reanalysis data during the rainy season from September to April for the period 2000–2014. When the diurnal cycle is strong, the high precipitation area observed over Sumatra in the afternoon migrates offshore during nighttime and reaches 500 km off the coast on average. The strong diurnal events are followed by the development of synoptic disturbances over the eastern Indian Ocean for several days, and apparent twin synoptic disturbances straddling the equator develop only when the convective center of the Madden–Julian Oscillation (MJO) lies over the Indian Ocean (MJO-IO). Without the MJO, the synoptic disturbances develop mainly south of the equator. The differences in the locations and behaviors of active synoptic disturbances are related to the strength of mean horizontal winds in the lower troposphere. During the MJO-IO, the intensification of mean northeasterly winds in the northern hemisphere blowing into the organized MJO convection in addition to mean southeasterly winds in the southern hemisphere facilitate the formation of the twin disturbances. These results suggest that seed disturbances arising from the diurnal offshore migration of precipitation from Sumatra develop differently depending on the mean states over the eastern Indian Ocean. Furthermore, it is shown that the MJO events with the strong diurnal cycle tend to have longer duration and continuing eastward propagation of active convection across the MC, whereas the convective activities of the other MJO events weaken considerably over the MC and develop again over the western Pacific. These results suggest that the strong diurnal cycle over Sumatra facilitates the smooth eastward propagation of the intraseasonal convection across the MC.</p>

Structure and Properties of Madden–Julian Oscillations Deduced from DYNAMO Sounding Arrays

2013 ◽  
Vol 70 (10) ◽  
pp. 3157-3179 ◽  
Author(s):  
Richard H. Johnson ◽  
Paul E. Ciesielski
Keyword(s):  
Indian Ocean ◽  
Deep Convection ◽  
Vertical Motion ◽  
Thermodynamic Characteristics ◽  
Reanalysis Data ◽  
Kelvin Waves ◽  
Thermal Anomalies ◽  
Inactive Phase ◽  
The Indian Ocean ◽  
North And South

Abstract The kinematic and thermodynamic characteristics of the October and November 2011 Madden–Julian oscillations (MJOs) that occurred over the Indian Ocean during Dynamics of the MJO (DYNAMO) are investigated. Analyses are presented 1) for two primary sounding arrays, where results are independent of model parameterizations, and 2) on larger scales, including the Indian Ocean, using operational and reanalysis data. Mean precipitation during DYNAMO was characterized by maxima in two east–west bands north and south of the equator. This pattern alternated between two bands during the inactive phase of the MJOs and a single rainfall maximum on the equator during the active phases. Precipitation over the northern sounding array (NSA), where the MJO signal was strongest, was significantly modulated by the MJOs, while the southern array experienced more frequent, briefer episodes of rainfall mostly related to ITCZ convection. Over the NSA the MJOs were characterized by gradual moistening of the low to midtroposphere over approximately 2-week periods. The October MJO featured multiple westward-moving, 2-day disturbances whereas the November MJO principally comprised two prominent Kelvin waves. Patterns of moistening, divergence, and vertical motion suggest a stepwise progression of convection, from shallow cumulus to congestus to deep convection. Tilted thermal anomalies in the upper troposphere–lower stratosphere reveal gravity or Kelvin waves excited by the MJO convective envelopes, which modulate the tropopause and contribute to preactive-phase upper-tropospheric moistening. While there is a number of similarities in the characteristics of the two MJOs, there are sufficient differences to warrant caution in generalizing results from these two events.

scholarly journals Analysis of Vortex Development over Eastern Indian Ocean using Potential Vorticity

2021 ◽  
Vol 893 (1) ◽  
pp. 012003
Author(s):  
R P Damayanti ◽  
N J Trilaksono ◽  
M R Abdillah
Keyword(s):  
Indian Ocean ◽  
Potential Vorticity ◽  
Vortex Motion ◽  
Weather Forecast ◽  
Reanalysis Data ◽  
Eastern Indian Ocean ◽  
Medium Range Weather Forecast ◽  
Circulation Patterns ◽  
Ocean Region ◽  
Flooding Events

Abstract A vortex phenomenon may have a significant influence, especially on wind circulation patterns and extreme weather in Indonesia. The formation of the vortex, initially located over the eastern part of the Indian Ocean has drawn attention due to the highest frequency of its occurrence and as the source of the vortex over the Indonesian region. Vortices generated in this region is also suspected as one of contributing factor for flooding events at Jakarta in 2002 and 2007, studying both formation and development mechanism of these vortices is essential. The evolution of vortex development is investigated to characterize the vortex motion and development pattern in the Eastern Indian Ocean region. The study was conducted for 17 years starting from 1998 to 2016 on every December-January-February (DJF) period using ECMWF (European Center for Medium-Range Weather Forecast) ERA-Interim Reanalysis data. The analysis of vortex evolution was conducted for each event using a composite evolution of potential vorticity anomalies in the isentropic layer. The result shows 84 vortex systems identified with three characteristic patterns of vortex movement that occurred during 295 days of the observation period. Composite analysis of potential vorticity anomalies shows that the initial formation of vortices in the Eastern Indian Ocean is related to the emergence of negative potential vorticity anomalies from the west, which subsequently forming the vortices.

scholarly journals Cold Season Southwest Asia Precipitation Sensitivity to El Niño–Southern Oscillation Events

2018 ◽  
Vol 31 (11) ◽  
pp. 4463-4482 ◽  
Author(s):  
Andrew Hoell ◽  
Mathew Barlow ◽  
Taiyi Xu ◽  
Tao Zhang
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Eastern Indian Ocean ◽  
El Nino Southern Oscillation ◽  
Southwest Asia ◽  
Cp El Niño ◽  
La Nina

Abstract The sensitivity of southwest Asia (25°–40°N, 40°–70°E) precipitation during the November–April rainy season to four types of El Niño–Southern Oscillation (ENSO) events, eastern Pacific (EP) and central Pacific (CP) El Niño and La Niña, is assessed using an ensemble of atmospheric model simulations forced by 1979–2015 boundary conditions. Sensitivity is assessed in terms of 1) the spread of precipitation across the ensemble members around the ensemble mean, 2) the probability of precipitation falling into the upper and lower terciles of the historical distribution, and 3) the relationship between the tropical atmosphere and southwest Asia precipitation during ENSO. During CP La Niña, the magnitude of the below-average mean precipitation exceeds the magnitude of the precipitation spread, thereby conditioning the probability of lower-tercile southwest Asia precipitation to greater than 70%. By contrast, EP La Niña does not alter the odds of southwest Asia precipitation terciles, as the magnitude of the near-zero mean precipitation is overwhelmed by the magnitude of the precipitation spread. EP and CP El Niño similarly result in above-average mean precipitation whose magnitude approaches the magnitude of the precipitation spread, thereby conditioning the probability of upper-tercile southwest Asia precipitation to around 50% region-wide. However, the notable effect of the precipitation spread during El Niño allows for a 20%–30% probability that the regional precipitation falls into the lower tercile. ENSO types simultaneously modify the probability of eastern Indian Ocean precipitation and southwest Asia precipitation, supporting the hypothesis that the tropical eastern Indian Ocean atmosphere serves as the medium by which ENSO forcing is communicated to southwest Asia.

scholarly journals Interannual Variability of Equatorial Eastern Indian Ocean Upwelling: Local versus Remote Forcing

2016 ◽  
Vol 46 (3) ◽  
pp. 789-807 ◽  
Author(s):  
Gengxin Chen ◽  
Weiqing Han ◽  
Yuanlong Li ◽  
Dongxiao Wang
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Southern Oscillation ◽  
Equatorial Indian Ocean ◽  
Eastern Indian Ocean ◽  
Boreal Summer ◽  
Thermocline Depth ◽  
Remote Forcing ◽  
Local Forcing ◽  
The Mean

AbstractThe equatorial eastern Indian Ocean (EIO) upwelling occurs in the Indian Ocean warm pool, differing from the equatorial Pacific and Atlantic upwelling that occurs in the cold tongue. By analyzing observations and performing ocean model experiments, this paper quantifies the remote versus local forcing in causing interannual variability of the equatorial EIO upwelling from 2001 to 2011 and elucidates the associated processes. For all seasons, interannual variability of thermocline depth in the EIO, as an indicator of upwelling, is dominated by remote forcing from equatorial Indian Ocean winds, which drive Kelvin waves that propagate along the equator and subsequently along the Sumatra–Java coasts. Upwelling has prominent signatures in sea surface temperature (SST) and chlorophyll-a concentration but only in boreal summer–fall (May–October). Local forcing plays a larger role than remote forcing in producing interannual SST anomaly (SSTA). During boreal summer–fall, when the mean thermocline is relatively shallow, SSTA is primarily driven by the upwelling process, with comparable contributions from remote and local forcing effects. In contrast, during boreal winter–spring (November–April), when the mean thermocline is relatively deep, SSTA is controlled by surface heat flux and decoupled from thermocline variability. Advection affects interannual SSTA in all cases. The remote and local winds that drive the interannual variability of the equatorial EIO upwelling are closely associated with Indian Ocean dipole events and to a lesser degree with El Niño–Southern Oscillation.

scholarly journals Simulating Global and North American Climate Using the Global Environmental Multiscale Model with a Variable-Resolution Modeling Approach

2010 ◽  
Vol 138 (10) ◽  
pp. 3967-3987 ◽  
Author(s):  
Marko Markovic ◽  
Hai Lin ◽  
Katja Winger
Keyword(s):  
North America ◽  
Indian Ocean ◽  
Interannual Variability ◽  
Tropical Pacific ◽  
Eastern Indian Ocean ◽  
Variable Resolution ◽  
Modeling Approach ◽  
Global Environmental ◽  
Global Environmental Multiscale ◽  
The Tropical Pacific

Abstract Results from two simulations using the Global Environmental Multiscale (GEM) model in a variable-resolution modeling approach are evaluated. Simulations with a highly resolved domain positioned over North America and over the tropical Pacific–eastern Indian Ocean are assessed against the GEM uniform grid control run, 40-yr ECMWF Re-Analysis (ERA-40), and available observations in terms of regional and global climate and interannual variability. It is found that the variable-resolution configurations realistically simulate global and regional climate over North America with seasonal means and variability generally closer to ERA-40 or observations than the control run. Systematic errors of the control run are still present within the variable-resolution simulations but alleviated to some extent over their respective highly resolved domains. Additionally, there is some evidence of performance deterioration due to the increased resolution. There is little evidence that an increased resolution over the tropical Pacific–eastern Indian Ocean, with better-resolved local processes (e.g., convection and equatorial waves), has a significant impact on the extratropical time mean fields. However, in terms of simulating the Northern Hemisphere atmospheric flow anomaly associated with the dominant mode of sea surface temperature interannual variability in the equatorial eastern Pacific (i.e., El Niño), both stretched configurations have more realistic teleconnection patterns than the control run.

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