Simulated Interannual Modulation of Intraseasonal Kelvin Waves in the Equatorial Indian Ocean

Outputs from a high-resolution ocean general circulation model (OGCM) for the period of 1990-2003 indicate an interannual modulation of intraseasonal Kelvin waves along the equatorial Indian Ocean. During normal conditions without IOD event, the first mode explains about 30-40% of the total variance in the western (60-65ºE) and central (75-80ºE) basin, while the second mode contributes up to 45% to the total variance in the central basin around the longitude of 82ºE. In contrast, during the 1997/98 IOD event, the fourth mode caused about 40% of the total variance in the central and eastern basin. During the 1994 IOD event, the contribution from the fourth baroclinic mode in the eastern basin caused 45% of the total variance. In the central basin, the second and the fourth baroclinic mode caused almost the same variance (~40%). The variations in the characteristics of the intraseasonal Kelvin waves are related to variations in the vertical stratification. During the IOD event, the pycnocline in the eastern basin was raised by about 50 m and the stratification at the upper level is strengthened, while it is weakened at lower levels. These changes lead to an increase in the contribution of higher-order baroclinic modes

A Comparative Assessment of Vegetation Diversity Under Coffee Plantations Inside and Outside Protected Forest Areas

The existence of tree vegetation planted in coffee plantations as shade trees is believed to have a positive influence on the growth and production of coffee plants. This study aims to analyze the diversity of coffee plant vegetation in three age classes planted inside and outside protected forest areas included in the administrative area of North Dempo and Central Dempo Districts, Pagar Alam City, South Sumatra Province. The results of observations and calculations of Value IVI found that Albizia sumatrana was the dominant species in all coffee plantations at various age levels. The IVI values of Albazia Sumatrana in coffee plants aged 10 years is 75.46 (inside PF) and 95.92 (outside PF). Assessment using the Shanon Index and Simpon Index showed the same results; coffee plantations at all age levels had a moderate diversity index, except for vegetation in coffee plantations aged < 5 years which were outside protected forest areas and had low diversity index values. Through the availability of this information, it is hoped that it will be used as initial information for selecting vegetation types that will be used to support restoration activities in areas around protected forests

On the Influence of Enso And IOD on Rainfall Variability Over The Musi Basin, South Sumatra

The southern Sumatera region experiences one rainy season and one dry season in a year associated with seasonal change in monsoonal winds. The peak of rainy season is occurring in November-December-January during the northwest monsoon season, while the dry season comes in June-July-August during the southeast monsoon season. This study is designed to evaluate possible influence of the coupled ocean-atmospheric modes in the tropical Indo-Pacific region, namely the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on the rainfall variability over the catchment area of the Music Basin, South Sumatera. The ENSO and IOD occurrences were reflected by the variability of sea surface temperature (SST) in the tropical Pacific and Indian Ocean, respectively. During El Niño and/or positive IOD episode, negative SST anomalies cover the eastern tropical Indian Ocean and western tropical Pacific including the Indonesian seas, leading to suppress convective activities that result in reduce precipitation over the maritime continent. The situation is reversed during La Niña and/or negative IOD event. The results revealed that the high topography area (e.g. Bukit Barisan) was shown to be instrumental to the pattern of rainfall variability. During the 2010 negative IOD co-occurring with La Niña event, the rainfall was significantly increase over the region. This excess rainfall was associated with warm SST anomaly over the eastern tropical Indian Ocean and the Indonesian seas. On the other hand, extreme drought event tends to occur during the 2015 positive IOD simultaneously with the occurrence of the El Niño events Investigation on the SST patterns revealed that cold SST anomalies covered the Indonesian seas during the peak phase of the 2015 positive IOD and El Niño event

Equatorial Oceanic Waves and the Evolution of 2007 Positive Indian Ocean Dipole

The role of equatorial oceanic waves on the evolution of the 2007 positive Indian Ocean Dipole (pIOD) event was evaluated using available observations and output from a quasi-analytical linear wave model. It was found that the 2007 pIOD event was a weak and short-lived event: developed in the mid-summer (July), matured in the early-fall (September), and terminated in the mid-fall (October). The evolution of the 2007 pIOD event was linked to the equatorial wave dynamics. The event development was associated with the generation of upwelling equatorial Kelvin waves (westward current anomalies) generated by easterly wind anomalies. The event termination was associated with the occurrence of eastward zonal current anomalies resulting from a complex interplay between the wind-forced down welling Kelvin waves and the eastern-boundary-reflected Rossby waves. Results from a quasi-analytical linear wave model show that during the event development and maturation, the wind-forced Kelvin waves played a dominant role in generating zonal current anomalies along the equatorial Indian Ocean, while the eastern-boundary-reflected Rossby waves tended to weaken the wind-forced Kelvin wave signals. During the event termination our model shows that the initiation of anomalous eastward current resulted from the reflected Rossby waves at the eastern boundary. The wind-forced Kelvin waves associated with the seasonal reversal of the monsoon further strengthened the eastward zonal currents generated by the boundary-generated Rossby waves in late-October/early-November. This highlights the importance of the eastern-boundary-reflected Rossby waves on the IOD event termination

Analisis Dinamika dan Sumber Massa Air Arus Lintas Indonesia

Dalam penelitian ini dilakukan pengkajian dinamika massa air Arus Lintas Indonesia (Arlindo) dalam kaitannya dengan sumber asli air yang dapat teridentifikasi masuk dari Samudra Pasifik ke perairan Indonesia Bagian Timur. Wilayah studi berada pada 12.5° LU – 2.5° LS dan 122,5° BT - 140° BT. Sumber data adalah World Ocean Database 2001 dari National Oceanography Data Center (NODC), http://www.nadc.noaa.gov/PC5/WODo1/pacif_o.html. Analisis dilakukan dengan menggunakan metode core layer dan analisis isopiknal sedangkan untuk mengolah dan menampilkan data digunakan software Ocean Data View mp versi 1.2, http://www.awi-bremerhaven.de/GEO/odv.Dari analisis yang dilakukan teridentifikasi bahwa sumber air Arlindo yang masuk ke Perairan Indonesia bagian timur melalui gerbang Arlindo memiliki karakteristik dari berbagai massa air, antara lain adalah core dari; NPSW dengan densitas potensial sekitar 24 sq salinitas 34.764 ml/l; SPSW dengan densitas potensial ekitar 25 sq salinitas S>35 psu dan konsentrasi oksigen terlarut sekitar 3.3 ml/l; NPIW dengan densitas potensial 26.5 sq salinitas S<34.55 psu dan konsentrasi oksigen terlarut antara 2 -3 ml/l dan AAIW dengan densitas potensial sekitar 27.2 sq. Secara umum semua karakteristik massa air ini mengidentifikasikan bahwasanya sumber air Arlindo berasal dari Samudera Pasifik

Coupled Ocean-Atmosphere Mode in the Tropical Indian Ocean during 2011

Coupled ocean-atmosphere mode in the tropical Indian Ocean, so-called the Indian Ocean Dipole (IOD), occurred during boreal summer to fall 2011. In this study, data from satellite observations and atmospheric reanalysis datasets together with data from ocean current mooring were used to evaluate the evolution of the 2011 IOD event. It is shown that the 2011 IOD was a weak and short-lived event. It developed in July, peaked in September, decayed in October and terminated in November. During the peak phase, maximum negative sea surface temperature anomaly off Sumatera-Java reached -1.2 °C. As oceanic response to easterly wind anomalies along the equator, the observed zonal currents in the central and eastern equatorial Indian Ocean also showed prominent westward currents during the peak phase of the 2011 IOD event

Coupled Ocean-Atmosphere Mode in the Tropical Indian Ocean during 2011

Coupled ocean-atmosphere mode in the tropical Indian Ocean, so-called the Indian Ocean Dipole (IOD), occurred during boreal summer to fall 2011. In this study, data from satellite observations and atmospheric reanalysis datasets together with data from ocean current mooring were used to evaluate the evolution of the 2011 IOD event. It is shown that the 2011 IOD was a weak and short-lived event. It developed in July, peaked in September, decayed in October and terminated in November. During the peak phase, maximum negative sea surface temperature anomaly off Sumatera-Java reached -1.2 &deg;C. As oceanic response to easterly wind anomalies along the equator, the observed zonal currents in the central and eastern equatorial Indian Ocean also showed prominent westward currents during the peak phase of the 2011 IOD event.&nbsp

WindSat and RAMA Buoy: a comparison of ocean-atmosphere data

Ocean-atmosphere data deployed along the equatorial Indian Ocean were used for validating the ocean-atmosphere data recorded by the WindSat satellite. Three RAMA Buoys mounted at 67 °E, 80.5°E and 90 °E along the equator were used to evaluate the sea surface temperature (SST), wind speeds and precipitation obtained by the WindSat satellite, except for precipitation in the eastern equatorial Indian Ocean. The SST from WindSat shows significant correlation with that from RAMA Buoy, with coefficient correlations of 0.95, 0.88 and 0.83, respectively. The root mean square errors (RMSEs) of the WindSat SST relative to RAMA Buoy data were 0.28, 0.29 and 0.32 °C, respectively. In this study, the quality performances of the WindSat wind speed were also satisfactory, with coefficient correlation of 0.64, 0.7 and 0.58 in each RAMA buoy. The corresponding RMSEs of the wind speeds were 1.46, 1.37 and 1.63 ms−1. Meanwhile, the WindSat precipitations reveal weak correlation with RAMA Buoy data, in particular in the eastern equatorial Indian Ocean. Overall, the WindSat satellite data for each measurement parameters can be used to replace in-situ observation data after taking into account the measurement errors

WindSat and RAMA Buoy: a comparison of ocean-atmosphere data

Ocean-atmosphere data deployed along the equatorial Indian Ocean were used for validating the ocean-atmosphere data recorded by the WindSat satellite. Three RAMA Buoys mounted at 67 °E, 80.5°E and 90 °E along the equator were used to evaluate the sea surface temperature (SST), wind speeds and precipitation obtained by the WindSat satellite, except for precipitation in the eastern equatorial Indian Ocean. The SST from WindSat shows significant correlation with that from RAMA Buoy, with coefficient correlations of 0.95, 0.88 and 0.83, respectively. The root mean square errors (RMSEs) of the WindSat SST relative to RAMA Buoy data were 0.28, 0.29 and 0.32 °C, respectively. In this study, the quality performances of the WindSat wind speed were also satisfactory, with coefficient correlation of 0.64, 0.7 and 0.58 in each RAMA buoy. The corresponding RMSEs of the wind speeds were 1.46, 1.37 and 1.63 ms−1. Meanwhile, the WindSat precipitations reveal weak correlation with RAMA Buoy data, in particular in the eastern equatorial Indian Ocean. Overall, the WindSat satellite data for each measurement parameters can be used to replace in-situ observation data after taking into account the measurement errors