scholarly journals Variation of Radar-Observed Precipitation Characteristics in Relation to the Simultaneous Passages of a Madden-Julian Oscillation Event and Convectively Coupled Equatorial Waves during the Years of the Maritime Continent Pilot Study

2021 ◽  
Author(s):  
Biao Geng ◽  
Masaki Katsumata
Keyword(s):  
Pilot Study ◽  
Low Frequency ◽  
Radar Data ◽  
Frequency Variation ◽  
Equatorial Waves ◽  
Madden Julian Oscillation ◽  
Maritime Continent ◽  
Convectively Coupled Equatorial Waves ◽  
Precipitation Characteristics ◽  
Before And After

AbstractIn this study, we examined the variations of precipitation morphology and rainfall in relation to the simultaneous passages of a Madden-Julian Oscillation (MJO) event and convectively coupled equatorial waves (CCEWs) observed during the Years of the Maritime Continent pilot study. We utilized globally merged infrared brightness temperature data and the radiosonde and radar data observed aboard the research vessel Mirai at 4°4′S, 101°54′E. As well as the observed MJO event, equatorial Rossby waves (ERWs), Kelvin waves (KWs), and mixed Rossby-gravity waves (MRGWs) were identified. The radar data exhibited high-frequency variation, mainly caused by KWs and MRGWs, and low-frequency variation, mainly caused by the MJO and ERWs. The MRGWs predominantly modulated convective echo areas and both convective and stratiform volumetric rainfall. In contrast, the MJO event had little influence on the variance of convective echoes. Moreover, stratiform echo areas and volumetric rainfall were more strongly modulated by the combined effects of the MJO, ERWs, KWs, and MRGWs than their convective counterparts. The intense development of stratiform echo areas and volumetric rainfall was coherent with the superimposition of the active phases of the MJO event and all the analyzed CCEWs. The strongest development and a significant reduction of convective echo-top heights before and after the peak MJO date, respectively, were coherent with the passages of ERWs and MRGWs, which were the dominant wave types in modulating echo-top heights. Thus, it appears that the superimposition of the CCEWs on the MJO event exerted complex modulations on the convective activities within the MJO event.

Tropical Precipitation Variability and Convectively Coupled Equatorial Waves on Submonthly Time Scales in Reanalyses and TRMM

2013 ◽  
Vol 26 (10) ◽  
pp. 3013-3030 ◽  
Author(s):  
Ji-Eun Kim ◽  
M. Joan Alexander
Keyword(s):  
Diurnal Cycle ◽  
Low Frequency ◽  
Tropical Rainfall Measuring Mission ◽  
Precipitation Variability ◽  
Department Of Energy ◽  
Equatorial Waves ◽  
Tropical Precipitation ◽  
Convectively Coupled Equatorial Waves ◽  
Precipitation Characteristics ◽  
Equatorial Wave

Abstract Tropical precipitation characteristics are investigated using the Tropical Rainfall Measuring Mission (TRMM) 3-hourly estimates, and the result is compared with five reanalyses including the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim), Modern Era Retrospective Analysis for Research and Applications (MERRA), National Centers for Environmental Prediction (NCEP)–National Center for Atmospheric Research (NCAR) reanalysis (NCEP1), NCEP–U.S. Department of Energy (DOE) reanalysis (NCEP2), and NCEP–Climate Forecast System Reanalysis (CFSR). Precipitation characteristics are evaluated in terms of the mean, convectively coupled equatorial wave activity, frequency characteristics, diurnal cycle, and seasonality of regional precipitation variability associated with submonthly scale waves. Generally the latest reanalyses such as ERA-Interim, MERRA, and CFSR show better performances than NCEP1 and NCEP2. However, all the reanalyses are still different from observations. Besides the positive mean bias in the reanalyses, a spectral analysis revealed that the reanalyses have overreddened spectra with persistent rainfall. MERRA has the most persistent rainfall, and CFSR appears to have the most realistic variability. The diurnal cycle in NCEP1 is extremely exaggerated relative to TRMM. The low-frequency waves with the period longer than 3 days are relatively well represented in ERA-Interim, MERRA, and CFSR, but all the reanalyses have significant deficiencies in representing convectively coupled equatorial waves and variability in the high-frequency range.

scholarly journals Forecast Skill of the Madden–Julian Oscillation in Two Canadian Atmospheric Models

2008 ◽  
Vol 136 (11) ◽  
pp. 4130-4149 ◽  
Author(s):  
Hai Lin ◽  
Gilbert Brunet ◽  
Jacques Derome
Keyword(s):  
General Circulation ◽  
Initial Conditions ◽  
Circulation Model ◽  
Skill Score ◽  
Forecast Skill ◽  
Second Phase ◽  
Equatorial Waves ◽  
Madden Julian Oscillation ◽  
Atmospheric Models ◽  
Convectively Coupled Equatorial Waves

Abstract The output of two global atmospheric models participating in the second phase of the Canadian Historical Forecasting Project (HFP2) is utilized to assess the forecast skill of the Madden–Julian oscillation (MJO). The two models are the third generation of the general circulation model (GCM3) of the Canadian Centre for Climate Modeling and Analysis (CCCma) and the Global Environmental Multiscale (GEM) model of Recherche en Prévision Numérique (RPN). Space–time spectral analysis of the daily precipitation in near-equilibrium integrations reveals that GEM has a better representation of the convectively coupled equatorial waves including the MJO, Kelvin, equatorial Rossby (ER), and mixed Rossby–gravity (MRG) waves. An objective of this study is to examine how the MJO forecast skill is influenced by the model’s ability in representing the convectively coupled equatorial waves. The observed MJO signal is measured by a bivariate index that is obtained by projecting the combined fields of the 15°S–15°N meridionally averaged precipitation rate and the zonal winds at 850 and 200 hPa onto the two leading empirical orthogonal function (EOF) structures as derived using the same meridionally averaged variables following a similar approach used recently by Wheeler and Hendon. The forecast MJO index, on the other hand, is calculated by projecting the forecast variables onto the same two EOFs. With the HFP2 hindcast output spanning 35 yr, for the first time the MJO forecast skill of dynamical models is assessed over such a long time period with a significant and robust result. The result shows that the GEM model produces a significantly better level of forecast skill for the MJO in the first 2 weeks. The difference is larger in Northern Hemisphere winter than in summer, when the correlation skill score drops below 0.50 at a lead time of 10 days for GEM whereas it is at 6 days for GCM3. At lead times longer than about 15 days, GCM3 performs slightly better. There are some features that are common for the two models. The forecast skill is better in winter than in summer. Forecasts initialized with a large amplitude for the MJO are found to be more skillful than those with a weak MJO signal in the initial conditions. The forecast skill is dependent on the phase of the MJO at the initial conditions. Forecasts initialized with an MJO that has an active convection in tropical Africa and the Indian Ocean sector have a better level of forecast skill than those initialized with a different phase of the MJO.

The Diurnal Cycle of Rainfall and the Convectively Coupled Equatorial Waves over the Maritime Continent

2020 ◽  
Vol 33 (8) ◽  
pp. 3307-3331 ◽  
Author(s):  
Naoko Sakaeda ◽  
George Kiladis ◽  
Juliana Dias
Keyword(s):  
Diurnal Cycle ◽  
Large Scale ◽  
Vertical Motion ◽  
Equatorial Waves ◽  
Maritime Continent ◽  
Moisture Profile ◽  
Convectively Coupled Equatorial Waves ◽  
Large Scale Disturbance ◽  
Diurnal Rainfall ◽  
Equatorial Rossby Waves

AbstractPrecipitation variability over the Maritime Continent is predominantly explained by its diurnal cycle and large-scale disturbances such as the Madden–Julian oscillation (MJO) and convectively coupled equatorial waves (CCEWs). To advance our understanding of their interactions and physical processes, this study uses satellite data to examine changes in the diurnal cycle of rainfall associated with the MJO and CCEWs over the Maritime Continent. We find that diurnal cycle modulations associated with the passage of any type of large-scale disturbance are closely tied to changes in rain types and land–sea diurnal propagation of rainfall. When the amplitude of the diurnal cycle increases over the islands, the phase of the diurnal cycle is delayed by a few hours as clouds are more organized and rainfall from stratiform-anvil clouds increases. Enhanced amplitude of the diurnal cycle can alter the speed of land–sea diurnal propagation of rainfall, which then influences the timing of diurnal rainfall over coastal regions. These changes in the diurnal cycle occur asymmetrically across the island terrain associated with the MJO and equatorial Rossby waves, while such asymmetric modulations are not observed for other waves. Geographical and wave dependencies of the diurnal cycle are linked to differences in large-scale lower tropospheric wind, vertical motion, and moisture profile perturbations, which are in turn tied to differences in cloud population evolution. The results of this study highlight the importance of further improving our understanding of the sensitivity of cloud populations to varying large-scale phenomena.

scholarly journals Modulation of Daily Rainfall in Southern Vietnam by the Madden–Julian Oscillation and Convectively Coupled Equatorial Waves

2016 ◽  
Vol 29 (16) ◽  
pp. 5801-5820 ◽  
Author(s):  
Roderick van der Linden ◽  
Andreas H. Fink ◽  
Joaquim G. Pinto ◽  
Tan Phan-Van ◽  
George N. Kiladis
Keyword(s):  
Vertical Wind Shear ◽  
Daily Rainfall ◽  
Radiosonde Data ◽  
Equatorial Waves ◽  
Madden Julian Oscillation ◽  
Coherent Signals ◽  
Southern Vietnam ◽  
Wave Interference ◽  
Convectively Coupled Equatorial Waves ◽  
Rainfall Anomalies

Abstract Rainfall extremes have a large socioeconomic relevance for southern Vietnam. More than 30 million people live in this low-lying, flood-prone region in Southeast Asia. In this study the influence of the Madden–Julian oscillation (MJO) and convectively coupled equatorial waves on the modulation of daily rainfall during the rainy season (May–October) is evaluated and quantified using an extensive station database and the gridded Asian Precipitation–Highly Resolved Observational Data Integration Toward Evaluation of Water Resources (APHRODITE) product for different phases of the equatorial waves. The MJO, Kelvin, and equatorial Rossby (ER) waves significantly modulate daily rainfall in Vietnam south of 16°N. The MJO shows the most coherent signals across the region, followed by ER waves, whose influence is strongest in central Vietnam; Kelvin waves only affect the southern parts of Vietnam. For all waves, the frequency of occurrence of intense daily rainfall larger than 25 mm is significantly enhanced during wet phases, whereas the magnitude of rainfall anomalies is related to the wave’s amplitude only in the MJO and ER cases. A novel wave interference diagram reveals strong positive interferences of dry and wet anomalies when the MJO occurs concurrently with Kelvin and ER waves. In terms of causes of rainfall anomalies, the waves modulate tropospheric moisture convergence over the region, but a strong influence on the depth of the monsoon flow and the vertical wind shear is discernible from radiosonde data only for the MJO. The results suggest new opportunities for submonthly prediction of dry and wet spells in Indochina.

scholarly journals Comparison of forecasting accuracy for Madden Julian Oscillation (MJO) and Convectively Coupled Equatorial Waves (CCEW) using Tropical Rainfall Measuring Mission (TRMM) and ERA-Interim precipitation forecast data for Indonesia

2021 ◽  
Author(s):  
Ida Pramuwardani ◽  
Hartono ◽  
Sunarto ◽  
Arhasena Sopaheluwakan
Keyword(s):  
Tropical Rainfall Measuring Mission ◽  
Forecast Model ◽  
Precipitation Forecast ◽  
Poor Correlation ◽  
Equatorial Waves ◽  
Madden Julian Oscillation ◽  
Tropical Rainfall ◽  
Convectively Coupled Equatorial Waves ◽  
Zonal Wavenumber ◽  
Forecast Data

Tropical Rainfall Measuring Mission (TRMM) and ERA-Interim forecast data analyzed using second-order autoregressive AR(2) and space-time-spectra analysis methods (respectively) revealed contrasting results for predicting Madden Julian Oscillation (MJO) and Convectively Coupled Equatorial Waves (CCEW) phenomena over Indonesia. This research used the same 13-year series of daily TRMM 3B42 V7 derived datasets and ERA-Interim reanalysis model datasets from the European Center for Medium-Range Weather Forecasts (ECMWF) for precipitation forecasts. Three years (2016 to 2018) of the filtered 3B42 and ERA-Interim forecast data was then used to evaluate forecast accuracy by looking at correlation coefficients for forecast leads from day +1 through day +7. The results revealed that rainfall estimation data from 3B42 provides better results for the shorter forecast leads, particularly for MJO, equatorial Rossby (ER), mixed Rossby-gravity (MRG), and inertia-gravity phenomena in zonal wavenumber 1 (IG1), but gives poor correlation for Kelvin waves for all forecast leads. A consistent correlation for all waves was achieved from the filtered ERA-Interim precipitation forecast model, and although this was quite weak for the first forecast leads it did not reach a negative correlation in the later forecast leads except for IG1. Furthermore, Root Mean Square Error (RMSE) was also calculated to complement forecasting skills for both data sources, with the result that residual RMSE for the filtered ERA-Interim precipitation forecast was quite small during all forecast leads and for all wave types. These findings prove that the ERA-Interim precipitation forecast model remains an adequate precipitation model in the tropics for MJO and CCEW forecasting, specifically for Indonesia.

scholarly journals Identifying the MJO, Equatorial Waves, and Their Impacts Using 32 Years of HIRS Upper-Tropospheric Water Vapor

2013 ◽  
Vol 26 (4) ◽  
pp. 1418-1431 ◽  
Author(s):  
Carl J. Schreck ◽  
Lei Shi ◽  
James P. Kossin ◽  
John J. Bates
Keyword(s):  
Water Vapor ◽  
Rossby Waves ◽  
North Pacific Ocean ◽  
Low Frequency ◽  
Longwave Radiation ◽  
Equatorial Waves ◽  
Climate Data ◽  
Convectively Coupled Equatorial Waves ◽  
Intersatellite Calibration ◽  
The Tropics

Abstract The Madden–Julian oscillation (MJO) and convectively coupled equatorial waves are the dominant modes of synoptic-to-subseasonal variability in the tropics. These systems have frequently been examined with proxies for convection such as outgoing longwave radiation (OLR). However, upper-tropospheric water vapor (UTWV) gives a more complete picture of tropical circulations because it is more sensitive to the drying and warming associated with subsidence. Previous studies examined tropical variability using relatively short (3–7 yr) UTWV datasets. Intersatellite calibration of data from the High Resolution Infrared Radiation Sounder (HIRS) has recently produced a homogeneous 32-yr climate data record of UTWV for 200–500 hPa. This study explores the utility of HIRS UTWV for identifying the MJO and equatorial waves. Spectral analysis shows that the MJO and equatorial waves stand out above the low-frequency background in UTWV, similar to previous findings with OLR. The fraction of variance associated with the MJO and equatorial Rossby waves is actually greater in UTWV than in OLR. Kelvin waves, on the other hand, are overshadowed in UTWV by horizontal advection from extratropical Rossby waves. For the MJO, UTWV identifies subsidence drying in the subtropics, poleward of the convection. These dry anomalies are associated with the MJO’s subtropical Rossby gyres. MJO events with dry anomalies over the central North Pacific Ocean also amplify the 200-hPa flow pattern over North America 7 days later. These events cannot be identified using equatorial OLR alone, which demonstrates that UTWV is a useful supplement for identifying the MJO, equatorial waves.

A note on the power distribution between symmetric and anti-symmetric components of the tropical Brightness Temperature spectrum in the wavenumber-frequency plane

2021 ◽  
Author(s):  
Ofer Shamir ◽  
Chaim I. Garfinkel ◽  
Ori Adam ◽  
Nathan Paldor
Keyword(s):  
Brightness Temperature ◽  
Power Distribution ◽  
Spectral Power ◽  
Equatorial Waves ◽  
Madden Julian Oscillation ◽  
Background Spectrum ◽  
Temperature Spectrum ◽  
Spectral Bands ◽  
Convectively Coupled Equatorial Waves ◽  
The Difference

AbstractA recent study observed the existence of a salient bias towards the symmetric part of the tropical wavenumber-frequency spectrum. Examination of the tropical Brightness Temperature (BT) spectrum in this note shows that its parity difference, i.e., the difference between its symmetric and anti-symmetric components, is concentrated in regions of the wavenumber-frequency plane corresponding to the spectral bands suggested by Wheeler and Kiladis (1999). In terms of the difference between the spectral power in the symmetric and anti-symmetric components, the spectral bands corresponding to Kelvin waves, Madden-Julian Oscillation, and Rossby waves explain about 31%, 21%, and 13% of the symmetric bias, respectively, while the combined contribution of all the other bands is negligible. The “background” spectrum after filtering out all the spectral bands explains the remaining 35% of the symmetric bias. As these spectral bands were originally designed for filtering convectively coupled equatorial waves, the findings of this note may help estimate the contributions of different wave features to the symmetric bias in the tropical BT spectrum. In addition, these findings may also help better understand the processes responsible for generating the tropical background spectrum.

scholarly journals Models for Multiscale Interactions. Part II: Madden–Julian Oscillation, Moisture, and Convective Momentum Transport

2016 ◽  
Vol 56 ◽  
pp. 10.1-10.5 ◽  
Author(s):  
Andrew J. Majda ◽  
Samuel N. Stechmann
Keyword(s):  
Tropical Cyclones ◽  
Momentum Transport ◽  
Mesoscale Convective Systems ◽  
Equatorial Waves ◽  
Madden Julian Oscillation ◽  
Synoptic Scale ◽  
Convective Systems ◽  
Convectively Coupled Equatorial Waves ◽  
Mesoscale Convective ◽  
Convective Momentum Transport

Abstract It is well known that the envelope of the Madden–Julian oscillation (MJO) consists of smaller-scale convective systems, including mesoscale convective systems (MCS), tropical cyclones, and synoptic-scale waves called “convectively coupled equatorial waves” (CCW). In fact, recent results suggest that the fundamental mechanisms of the MJO involve interactions between the synoptic-scale CCW and their larger-scale environment (Majda and Stechmann). In light of this, this chapter reviews recent and past work on two-way interactions between convective systems—both MCSs and CCW—and their larger-scale environment, with a particular focus given to recent work on MJO–CCW interactions.

Sign in / Sign up

Export Citation Format

Share Document