Possible Role of the Diurnal Cycle in Land Convection in the Barrier Effect on the MJO by the Maritime Continent

2019 ◽  
Vol 46 (5) ◽  
pp. 3001-3011 ◽  
Author(s):  
Jian Ling ◽  
Chidong Zhang ◽  
Robert Joyce ◽  
Ping‐ping Xie ◽  
Guiwan Chen
Keyword(s):  
Diurnal Cycle ◽  
Barrier Effect ◽  
Maritime Continent

scholarly journals Role of Diurnal Cycle in the Maritime Continent Barrier Effect on MJO Propagation in an AGCM

2021 ◽  
Vol 78 (5) ◽  
pp. 1545-1565
Author(s):  
R. S. Ajayamohan ◽  
Boualem Khouider ◽  
V. Praveen ◽  
Andrew J. Majda
Keyword(s):  
Diurnal Cycle ◽  
General Circulation ◽  
Dominant Role ◽  
Circulation Model ◽  
Striking Difference ◽  
Barrier Effect ◽  
Maritime Continent ◽  
Stochastic Case ◽  
The Impact

AbstractThe barrier effect of the Maritime Continent (MC) in stalling or modifying the propagation characteristics of the MJO is widely accepted. The strong diurnal cycle of convection over the MC is believed to play a dominant role in this regard. This hypothesis is studied here, with the help of a coarse-resolution atmospheric general circulation model (AGCM). The dry dynamical core of the AGCM is coupled to the multicloud parameterization piggybacked with a dynamical bulk boundary layer model. A set of sensitivity experiments is carried out by systematically varying the strength of the MC diurnal flux to assess the impact of the diurnal convective variability on the MJO propagation. The effects of deterministic and stochastic diurnal forcings on MJO characteristics are compared. It is found that the precipitation and zonal wind variance, on the intraseasonal time scales, over the western Pacific region decreases with the increase in diurnal forcing, indicating the blocking of MC precipitation. An increase in precipitation variance over the MC associated with the weakening of precipitation variance over the west Pacific is evident in all experiments. The striking difference between deterministic and stochastic diurnal forcing experiments is that the strength needed for the deterministic case to achieve the same degree of blocking is almost double that of stochastic case. The stochastic diurnal flux over the MC seems to be more detrimental in blocking the MJO propagation. This hints at the notion that the models with inadequate representation of organized convection tend to suffer from the MC-barrier effect.

Understanding the role of topography on the diurnal cycle of precipitation in the Maritime Continent during MJO propagation

2022 ◽  
Author(s):  
Haochen Tan ◽  
Pallav Ray ◽  
Bradford Barrett ◽  
Jimy Dudhia ◽  
Mitchell Moncrieff ◽  
...  
Keyword(s):  
Diurnal Cycle ◽  
Maritime Continent ◽  
Diurnal Cycle Of Precipitation

scholarly journals Barrier Effect of the Indo-Pacific Maritime Continent on MJO Propagation in Observations and CMIP5 Models

2020 ◽  
Vol 33 (12) ◽  
pp. 5173-5193 ◽  
Author(s):  
Guiwan Chen ◽  
Jian Ling ◽  
Chongyin Li ◽  
Yuanwen Zhang ◽  
Chidong Zhang
Keyword(s):  
Critical Role ◽  
Cmip5 Models ◽  
Barrier Effect ◽  
Gridded Data ◽  
Physical Processes ◽  
Maritime Continent ◽  
Surface Evaporation ◽  
Spectral Signal ◽  
High Resolution Models

AbstractThis study explores possible mechanisms for the barrier effect of the Indo-Pacific Maritime Continent (MC) on MJO propagation. In particular, this study examines whether similar mechanisms can be found in both observations and CMIP5 simulations. All models simulate individual MJO events but underestimate the percentage of MJO events propagating into the MC. The simulations are grouped into the top and bottom 50% based on their capability of reproducing the MJO spectral signal. When compared with the observations, the bottom 50% of the simulations significantly underestimate the MJO strength and exaggerate the barrier effect intensity, whereas these discrepancies are not significant in the top 50% of the simulations. From the top 50% of the simulations, the MJO strength, moisture processes, and surface evaporation in the MC all play important roles in constituting the barrier effect. No such evidence is found in observations. The discrepancies may come from small observed sample size and/or misrepresentations of key physical processes in the models. A consistent result is found in the observations and simulations: Whether MJO events can cross the MC depends on the degree to which dominant precipitation over land shifts to over water in the MC as MJO convection centers approach the MC and cross it. This result emphasizes the critical role of precipitation over water in carrying convective signals of the MJO through the MC. The results suggest that diagnosing the model alone on mechanisms for the barrier effect could be misleading; further investigations using a combination of observations, global gridded data, and high-resolution models are needed.

scholarly journals Barrier Effect on MJO Propagation by the Maritime Continent in the MJO Task Force/GEWEX Atmospheric System Study Models

2019 ◽  
Vol 32 (17) ◽  
pp. 5529-5547 ◽  
Author(s):  
Jian Ling ◽  
Yuqing Zhao ◽  
Guiwan Chen
Keyword(s):  
General Circulation ◽  
Task Force ◽  
General Circulation Models ◽  
Boreal Winter ◽  
Barrier Effect ◽  
System Study ◽  
Maritime Continent ◽  
Walker Cell ◽  
Blocking Effects

ABSTRACTThe simulated Madden–Julian oscillation (MJO) events in 27 general circulation models (GCMs) are identified using an MJO tracking method. The results suggest that the occurrence frequencies of simulated MJO events can represent a model’s ability to simulate several characteristics of the MJO to a certain extent during boreal winter, such as propagation range, strength, and termination longitude. All tracked MJO events are classified into those that propagate through the Maritime Continent (MC) (MJO-C) and those that do not (MJO-B), and the weakening and blocking effects on MJO propagation by the MC in GCMs were quantified. In general, if a GCM shows a stronger weakening effect on MJO strength over the MC, it tends to produce a stronger blocking effect on MJO propagation over the MC during boreal winter. The barrier effect of the MC on MJO propagation is exaggerated in most GCMs, while it can be underestimated in some GCMs, especially the coupled GCMs. Strong lower-tropospheric premoistening is identified ahead of the MJO convection center when it is over the central MC for MJO-C but not for MJO-B in most GCMs. Such strong premoistening is mainly attributed to the zonal gradient of lower-tropospheric easterly anomalies within the front Walker cell, which could be a precursor leading to the eastward propagation of MJO convection. In contrast to the observation, the role of the background sea surface temperature and land–sea precipitation contrast in the barrier effect on MJO propagation by the MC is not well captured by most GCMs.

scholarly journals On the Sensitivity of the Simulated Diurnal Cycle of Precipitation to 3-Hourly Radiosonde Assimilation: A Case Study over the Western Maritime Continent

2021 ◽  
Vol 149 (10) ◽  
pp. 3449-3468
Author(s):  
Joshua Chun Kwang Lee ◽  
Anurag Dipankar ◽  
Xiang-Yu Huang
Keyword(s):  
Diurnal Cycle ◽  
High Frequency ◽  
Initial Conditions ◽  
Rainfall Variability ◽  
Weather Prediction ◽  
Radiosonde Data ◽  
Western Coast ◽  
Maritime Continent ◽  
Model Biases ◽  
Diurnal Cycle Of Precipitation

AbstractThe diurnal cycle is the most prominent mode of rainfall variability in the tropics, governed mainly by the strong solar heating and land–sea interactions that trigger convection. Over the western Maritime Continent, complex orographic and coastal effects can also play an important role. Weather and climate models often struggle to represent these physical processes, resulting in substantial model biases in simulations over the region. For numerical weather prediction, these biases manifest themselves in the initial conditions, leading to phase and amplitude errors in the diurnal cycle of precipitation. Using a tropical convective-scale data assimilation system, we assimilate 3-hourly radiosonde data from the pilot field campaign of the Years of Maritime Continent, in addition to existing available observations, to diagnose the model biases and assess the relative impacts of the additional wind, temperature, and moisture information on the simulated diurnal cycle of precipitation over the western coast of Sumatra. We show how assimilating such high-frequency in situ observations can improve the simulated diurnal cycle, verified against satellite-derived precipitation, radar-derived precipitation, and rain gauge data. The improvements are due to a better representation of the sea breeze and increased available moisture in the lowest 4 km prior to peak convection. Assimilating wind information alone was sufficient to improve the simulations. We also highlight how during the assimilation, certain multivariate background error constraints and moisture addition in an ad hoc manner can negatively impact the simulations. Other approaches should be explored to better exploit information from such high-frequency observations over this region.

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.

Diurnal cycle of Isospora spp. oocyst shedding in Eurasian blackbirds (Turdus merula)

2004 ◽  
Vol 82 (5) ◽  
pp. 764-768 ◽  
Author(s):  
Katharina Misof
Keyword(s):  
Population Dynamics ◽  
Diurnal Cycle ◽  
Bird Species ◽  
Free Living ◽  
Turdus Merula ◽  
Coccidian Oocyst ◽  
Diurnal Fluctuations ◽  
Evolutionary Aspects ◽  
Practical Implications

Diurnal fluctuations in the appearance of parasites have been recognized for more than 60 years but have been largely ignored in studies examining the role of parasites in connection with evolutionary aspects of behaviour, ecology, and population dynamics. The disregard of diurnal fluctuations, however, can influence the reliability and interpretation of data. I examined shedding of Isospora spp. oocysts in faeces of naturally infected, free-living Eurasian blackbirds (Turdus merula L., 1758). Adult birds and nestlings shed coccidian oocysts (Isospora spp.) predominantly in the afternoon. The results are in agreement with earlier studies on coccidian oocyst shedding in other bird species. They are discussed with regard to these studies and to practical implications for future investigators in this field.

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
Sign in / Sign up

Export Citation Format

Share Document