Examination of 3-6 day Disturbances over Equatorial Indonesia Based on Boundary Layer Radar Observations during 1996-1999 at Bukittinggi, Serpong and Biak.

Widiyatmi, Ipuk; Hashiguchi, Hiroyuki; Fukao, S.; Yamanaka, Manabu D.; Ogino, Shin-Ya; Gage, K. S.; Harijono, Sri Woro B.; Diharto, Sri; Djojodihardjo, Harjono

doi:10.2151/jmsj.79.317

Cited by 13 publications

(18 citation statements)

References 15 publications

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“…5). However, such transient or traveling disturbances are modified or weakened on reaching the IMC (Nitta et al 1992;Widiyatmi et al 2001;Sakurai et al 2005;Shibagaki et al 2006;Hidayat and Kizu 2010; and cannot explain the convective clouds and rainfall over the IMC throughout the year.…”

Section: The Global Energy/water Cycle and The Maritime Continentmentioning

confidence: 99%

“…The rainfall (particularly over the sea rather than the land) at various locations over the IMC increases during the active/wet phase of ISVs/MJOs (e.g., Widiyatmi et al 2001;Murata et al 2002;Sakurai et al 2005Sakurai et al , 2009Sakurai et al , 2011Shibagaki et al 2006;Wu et al 2007Wu et al , 2013Hidayat and Kizu 2010;Mori et al 2011; Kamimera et al 2012;Peatman et al 2014). As a result, the onset and total rainfall amount of the rainy season over the IMC (in particular over the southern hemispheric part) are governed by the passage of active phases of ISVs/MJOs (see Fig.…”

Section: Diurnal Cycle Observed Around the Imc Coastlinesmentioning

confidence: 99%

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Maritime continent coastlines controlling Earth’s climate

Yamanaka

Ogino

et al. 2018

Prog Earth Planet Sci

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During the Monsoon Asian Hydro−Atmosphere Scientific Research and Prediction Initiative (MAHASRI; 2006-16), we carried out two projects over the Indonesian maritime continent (IMC), constructing the Hydrometeorological Array for Intraseasonal Variation−Monsoon Automonitoring (HARIMAU; 2005-10) radar network and setting up a prototype institute for climate studies, the Maritime Continent Center of Excellence (MCCOE; 2009-14). Here, we review the climatological features of the world's largest "regional" rainfall over the IMC studied in these projects. The fundamental mode of atmospheric variability over the IMC is the diurnal cycle generated along coastlines by land−sea temperature contrast: afternoon land becomes hotter than sea by clear-sky insolation before noon, with the opposite contrast before sunrise caused by evening rainfall-induced "sprinkler"-like land cooling (different from the extratropical infrared cooling on clear nights). Thus, unlike the extratropics, the diurnal cycle over the IMC is more important in the rainy season. The intraseasonal, seasonal to annual, and interannual climate variabilities appear as amplitude modulations of the diurnal cycle. For example, in Jawa and Bali the rainy season is the southern hemispheric summer, because land heating in the clear morning and water vapor transport by afternoon sea breeze is strongest in the season of maximum insolation. During El Niño, cooler sea water surrounding the IMC makes morning maritime convection and rainfall weaker than normal. Because the diurnal cycle is almost the only mechanism generating convective clouds systematically near the equator with little cyclone activity, the local annual rainfall amount in the tropics is a steeply decreasing function of coastal distance (e-folding scale 100-300 km), and regional annual rainfall is an increasing function of "coastline density" (coastal length/land area) measured at a horizontal resolution of 100 km. The coastline density effect explains why rainfall and latent heating over the IMC are twice the global mean for an area that makes up only 4% of the Earth's surface. The diurnal cycles appearing almost synchronously over the whole IMC generate teleconnections between the IMC convection and the global climate. Thus, high-resolution (<< 100 km; << 1 day) observations and models over the IMC are essential to improve both local disaster prevention and global climate prediction.

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Section: The Global Energy/water Cycle and The Maritime Continentmentioning

confidence: 99%

Section: Diurnal Cycle Observed Around the Imc Coastlinesmentioning

confidence: 99%

Maritime continent coastlines controlling Earth’s climate

Yamanaka

Ogino

et al. 2018

Prog Earth Planet Sci

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“…These may be mixed Rossby-gravity waves [Yanai and Maruyama, 1966;Wheeler and Kiladis, 1999;Widiyatmi et al, 1999Widiyatmi et al, , 2001.…”

Section: Atmospheric Observationsmentioning

confidence: 99%

Equatorial Atmosphere Radar (EAR): System description and first results

et al. 2003

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[1] A VHF Doppler radar with an active phased-array antenna system, called the Equatorial Atmosphere Radar (EAR), was established recently at the equator near Bukittinggi, West Sumatra, Indonesia (0.20°S, 100.32°E, 865 m above sea level). The EAR is a large monostatic radar which operates at 47.0 MHz with peak output power of 100 kW. The EAR uses a circular antenna array, approximately 110 m in diameter, which consists of 560 three-element Yagi antennas. Each antenna is driven by a solid-state transmitter-receiver module. This system configuration allows the antenna beam to be steered electronically up to 5,000 times per second. The scientific objective of the EAR is to advance knowledge of dynamical and electrodynamical coupling processes in the equatorial atmosphere from the near-surface region to the upper atmosphere. The equatorial atmosphere over Indonesia is considered to play an important role in global change of the Earth's atmosphere. This paper presents the system description of the EAR, including observational results of the equatorial atmosphere made for the first time with altitude resolution of 75-150 m.

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“…From the spectral analysis of horizontal winds observed by BLR, Widiyatmi et al (2001) showed that oscillations of zonal wind with a period of >10 days are prominent over Sumatera, and suggested that these oscillations are related to Kelvin waves and/or ISVs. The relation between diurnal variations of convective activities over Sumatera caused by local circulations and large-scale convective activities by SCCs was discussed by Murata et al (2002).…”

Section: Introductionmentioning

confidence: 99%

Convective activities associated with intraseasonal variation over Sumatera, Indonesia, observed with the equatorial atmosphere radar

et al. 2004

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Abstract. The influence of intraseasonal variation (ISV) on convective activities over Sumatera (or Sumatra) is studied by using data derived from the Equatorial Atmosphere Radar (EAR), the Boundary Layer Radar (BLR), the surface weather station, the Geostationary Meteorological Satellite (GMS), and NCEP/NCAR reanalysis. In June 2002, convective activities over the Indian Ocean, the maritime continent, and the western Pacific were significantly modulated by the ISV. Zonal wind observed by EAR and surface pressure observed at the observation site suggested the existence of a Kelvin-wave-like structure of ISV. From temporal variations of T BB , zonal wind at 850 hPa, and vertical shear of horizontal wind between 700 and 150 hPa, we classified the observation periods into the inactive phase (1-9 June), active phase (10-19 June), and postwesterly wind burst phase of ISV (20-26 June). During the inactive phase of ISV, convective activities caused by local circulation were prominent over Sumatera. Results of radar observations indicated the dominance of convective rainfall events over the mountainous area of Sumatera during the inactive phase of ISV. During the active phase of the ISV, cloud clusters (CCs), which developed in the convective envelope of SCC with a period of 1-2 days, mainly induced the formation of convective activities over Sumatera. Results of radar observations indicated that both convective and stratiform rainfall events occurred over the mountainous area of Sumatera during the active phase of ISV. In the postwesterly wind burst phase of ISV, Correspondence to: M. K. Yamamoto (m-yamamo@rish.kyoto-u.ac.jp) convective activities were suppressed over Sumatera. Features of convective activities found over Sumatera generally agreed well with those found in Tropical Ocean and Global Atmosphere/Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). However, local circulation played an important role in the formation of convective activities over Sumatera in the inactive phase of ISV.

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Examination of 3-6 day Disturbances over Equatorial Indonesia Based on Boundary Layer Radar Observations during 1996-1999 at Bukittinggi, Serpong and Biak.

Cited by 13 publications

References 15 publications

Maritime continent coastlines controlling Earth’s climate

Maritime continent coastlines controlling Earth’s climate

Equatorial Atmosphere Radar (EAR): System description and first results

Convective activities associated with intraseasonal variation over Sumatera, Indonesia, observed with the equatorial atmosphere radar

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