We analyzed 3-hourly Tropical Rainfall Measuring Mission multi-satellite analysis (TRMM 3B42) version-7 data for the 17year period 1998−2014 to investigate seasonal and geographic characteristics of the diurnal rainfall cycle (DRC) over Sumatera, Indonesia. Dividing Sumatera into north, central, and south regions approximately perpendicular to the west coast, we point out for the first time early-afternoon initiation of daily rainfall not only in the Barisan Mountains but also in the east-coastal small islands (ECSIs) such as Bangka and Belitung. Westward and eastward migrations of rainfall areas from the Barisan Mountains are varied with seasons and regions, with the most remarkable being westward during September-October-November (SON) in the central region and the least remarkable occurring during June-July-August (JJA) in the southern region. In the central region, the DRC reaches a distance of ~700 km off the west coast during SON and of only 200 km during March-April-May (MAM). The other westward migrations from the ECSIs in the central and southern regions (except for JJA) have been confirmed by 5-year hourly Multi-functional Transport Satellite-1R (MTSAT-1R) cloud-top data. The results shown in this paper suggest that the rainfall distribution with respect to coastal distance, varying geographically and seasonally.

Rainfall is one of main causes of floods. Monitoring of the rainfall is essential for understanding flood mechanism and early warning. Ground-based rain gauge is a conventional device to measure rainfall amount and considered as a point measurement. Satellite-based rainfall estimates provides complement measurement over wide area having few or even no in situ data. This study evaluates rainfall intensity variation and patterns preceding flood events in Indonesia for the period of 2003-2010 using the GSMaP_MVK satellite-based rainfall product with one hour and 0.1o x 0.1o resolutions and rain gauge station data as a benchmark. The analysed data are 3-hourly average and daily accumulation time steps. The chosen research locations were Medan City, Pekanbaru City, Indragiri Hulu Regency, Samarinda City and Manado City. Graphical comparisons of the GSMaP_MVK with the rain gauge data show discrepancies in capturing rainfall events and intensity. The GSMaP_MVK performs underestimation for the most areas, except Samarinda City, which is overestimated. Short-term period rainfall pattern is the most frequent occurred preceding flood events for the entire study areas which indicate that the areas are more susceptible to flash floods and river overflows. Overall, the GSMaP_MVK product provides promising potentiality for the application of monitoring rainfall conditions preceding flood events over the research locations. Statistical verifications reveal that on average, correlation coefficients are (0.22-0.54) and (0.65-0.83) for 3-hourly and daily scale, respectively. While, probability of rain detections (PODs) are (0.57-0.75) and (0.93-0.99), accordingly.

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The comprehensive relationship between meteorological conditions and whether low water cloud touches the surface, particularly at sea, is examined with the goal of improving low-cloud detection by satellite. Gridpoint-value data provided by an operational mesoscale model with integration of Multifunction Transport Satellite-2 data can provide sufficient data for statistical analyses to find general parameters that can discern whether low clouds touch the surface, compensating for uncertainty due to the scarcity of observation sites at sea and the infrequent incidence of fog. The analyses reveal that surface-touching low clouds tend to have lower cloud-top heights than those not touching the surface, although the frequency distribution of cloud-top height differs by season. The bottom of the G . G m layer (where G and G m are the vertical gradient and the moist-adiabatic lapse rate of the potential temperature, respectively) with surface-touching low-cloud layers tends to be very low or almost attached to the surface. In contrast, the tops of low-cloud layers not touching the surface tend to occur near the bottom of the G . G m layer. Mechanisms to correlate these meteorological conditions with whether low clouds touch the surface are inferred from investigations into the vertical structure of equivalent potential temperature. These results indicate that the temperature difference between cloud-top height and the surface can be an appropriate parameter to infer whether low clouds touch the surface. It is also suggested that only a little addition of meteorological ancillary data, such as the forecast sea surface temperature, to satellite data allows successful performance of the discrimination.

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One of the useful ways to measure the effect of the flow control devise is to use the wall-shear stress sensor to measure the wall-shear stress directly. The sensor used in this paper measures the wall-shear stress, which is reduced by the flow control devise. In this paper, the wall-shear stress of the plane shear layer with the plasma synthetic jet actuator (PSJA) is investigated. PSJA is a flow control device composed of electrodes with A.C. signal. The actuator uses electrohydrodynamic (EHD) effect and induces flow around the electrodes. PSJA has great advantage such as miniaturization, maintenance free, and easy to control compared to other actuators. In this paper, the wall-shear stress of plane shear layer in a low-speed turbulent wind tunnel is observed to measure the effect of the PSJA. The results show that the PSJA changes the flow condition of shear layer by accelerating the flow in shear layer. The wall-shear stress reduces and increases according to the displacement of the wall-shear stress sensor and the actuator.