An annular solar eclipse swept over Taiwan in the early morning on 21 May 2012. This provides an excellent opportunity to study ionospheric response to the solar eclipse mainly due to photochemical effects. Local ground‐based Global Positioning System receivers, an ionosonde, high frequency‐continue wave Doppler sounding systems, and very low frequency receivers are used to observe ionospheric eclipse signatures. These multiinstrument observations show that the extreme total electron content (TEC) depression lags the maximum obscuration by about 5–20 min, while the Doppler frequency shift decreases and increases (i.e., the ionosphere ascends and descends) during first contact‐maximum obscuration and maximum obscuration‐last contact, respectively. The ionosonde data well agree with the TEC and Doppler frequency shift observations. The results show that the extreme TEC depression lag (i.e., delay time) being inversely proportional to the associated maximum obscuration confirms that the photochemical process is essential in Taiwan during the 21 May 2012 annular solar eclipse. A theoretical derivation is proposed for the first time to explain the delay time due to pure photochemical process during solar eclipses.

This study investigates 14-year ultra-fast Kelvin wave (UFKW) activity in the mesosphere and lower thermosphere (MLT) and in the upper stratosphere where the mesopause semiannual oscillation (MSAO) and the stratopause semiannual oscillation (SSAO) dominate the two altitude regions, respectively. The wave properties are derived from SABER temperature data for the period from 2003 to 2016 by two-dimensional fast Fourier transform. The investigations focus on the UFKW with zonal wavenumber 1 and periods of 2.5-4.5 days. The spectra, daily variations, and seasonal variations of UFKW are investigated. The wave activity is also compared with the background zonal wind derived from the horizontal wind model 2014 (HWM14) for the MLT region and from European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis for the upper stratosphere. The results are that periods of UFKW are mainly in the range of 2.5-4.5 days, but the dominated periods change from year to year. The UFKW amplitudes increase with altitude, and the largest amplitudes occur at altitudes above 90 km. Above 95 km, the mean zonal wind is westward at all times and the amplitude of UFKW is large most of the time. In the MLT region and the upper stratosphere, the large-amplitude UFKW tend to occur in the westward phase of the MSAO and the SSAO. The seasonal variation of UFKW in the MLT region and the upper stratosphere both show a semiannual variation in which the maximum and the secondary maximum are in August and February, respectively. The correlation analysis shows that the time lags between the 90-km wave variation and lower altitude wave variations do not match the theoretical expectation of the wave upward velocity. Finally, the MSAO and the SSAO act like two filters, which modify the wave amplitude and result in different daily variations in the MLT region and in the upper stratosphere.

In the past years, global morphology and climatology of gravity waves have been widely studied and the effects of topography and convection systems have been evaluated, but the complete gravity wave distribution could not be explained by these effects. To find the missing controlling factors, a series of synoptic scale analyses is performed in the present study to investigate relationships between synoptic scale factors and potential energy (Ep) associated with gravity waves. Global distribution of Ep during a 12-year period from 2002 to 2013 is derived using temperature profiles retrieved from observations of Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. Synoptic scale factors obtained from ECMWF Interim reanalysis data are employed to investigate the correlation between synoptic systems and Ep. It is found that Ep values are high around extratropical cyclones over mid-latitudes (30–60°) and around the Intertropical Convergence Zone (ITCZ) over low-latitudes (10–30°). Ep values are low around subtropical highs over both mid- and low-latitudes. This is the first time that a synoptic scale analysis of Ep distribution is performed, and the influence of synoptic scale factors on Ep confirmed.

Equatorial atmospheric Kelvin waves are investigated during a positive El Niño Southern Oscillation (ENSO) episode using temperature data retrieved from GPS Radio Occultation (RO) observations of FORMOSAT-3/COSMIC during the period from August 2006 to December 2013. Enhanced Kelvin wave amplitudes are observed during the El Niño episode of 2009-2010 and it is also observed that these amplitudes correlate with the Niño 3.4 index and also with outgoing longwave radiation and trade wind index. This study indicates that the enhanced equatorial atmospheric Kelvin wave amplitudes might be produced by geophysical processes that were involved in the onset and development of the El Niño episode. Further, easterly winds above the tropopause during this period favored the vertically upward propagation of these waves that induced a fast descending westerly regime by the end of 2010, where the zero-wind line is observed to take only 5 months to descend from 10 to 50 hPa. The current study presents observational evidence of enhanced Kelvin wave amplitudes during El Niño that has affected the stratospheric quasi-biennial oscillation (QBO) through wave-mean flow interactions. Earlier El Niño episodes of 1987 and 1998 are also qualitatively investigated, using reanalysis data. It is found that there might have been an enhancement in the equatorial Kelvin wave amplitudes during almost all El Niño episodes, however, an effect of a fast descending westerly is observed in the QBO only when the ambient zonal winds in the lower stratosphere favor the upward propagation of the Kelvin waves and consequently they interact with the mean flow. This study indicates that the El Niño and QBO are not linearly related and wave mean flow interactions play a very important role in connecting these two geophysical phenomena.

GPS radio occultations by Formosa Satellite mission-3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC) provide bending angle profiles, which are further processed to give profiles of temperature and water vapour in the lower atmosphere and electron density in the upper atmosphere. The level 2 'atmPrf' (atmospheric profile) product of version 2010.2640 gives temperature from surface to 0.2 hPa (similar to 60 km). This is a dry temperature data product that does not include relative humidity in the inversion process and hence is reliable at altitudes < 100 hPa and erroneous at lower altitudes. In the current study we compare the COSMIC 'atmPrf' data from December 2010 to November 2011 with other satellite (SABER/TIMED and MLS/Aura) temperatures from 50 to 0.2 hPa, COSMIC 'wetPrf' data and reanalysis (NCEP, ERA-Interim and UKMO) outputs at 100, 10, 1 and 0.5 hPa pressure levels. The satellite comparisons show that below 1 hPa the observed median differences are most likely produced due to the biases in the retrievals of SABER and MLS. 'atmPrf' and 'wetPrf' temperatures compare extremely well in the common altitudes with differences being absolute zero between 200 and 10 hPa. When compared to reanalysis outputs, COSMIC seasonal means match NCEP and ECMWF seasonal mean temperatures very well, especially at 100 and 10 hPa. We conclude from this study that with the COSMIC dry temperature retrievals obtained from radio occultations of GPS, there is a 20 km extension of reliable data in the middle atmosphere. 'atmPrf' data are of good quality and provide reliable and unprecedentedly large number of profiles at greater temporal and spatial resolutions for further studies and investigations of the middle atmosphere up to 1 hPa, i.e., approximately up to the stratopause at around 50 km.

Temperature data from Global Positioning System based Radio Occultation (GPS RO) soundings of the Formosa Satellite mission 3/Constellation Observing System for Meteorology, Ionosphere and Climate (FORMOSAT-3/COSMIC or F-3/C) micro satellites have been investigated in detail to study the Kelvin wave (KW) properties during September 2008 to February 2009 using the two-dimensional Fourier transform. It is observed that there was strong KW activity during November and December 2008; large wave amplitudes are observed from above the tropopause to 40 km – the data limit of F-3/C. KW of wavenumbers E1 and E2 with time periods 7.5 and 13 days, dominated during this period and the vertical wavelengths of these waves varied from 12 to 18 km. This event is very interesting as the QBO during this period was westerly in the lower stratosphere (up to ~ 26 km) and easterly above, whereas, climatological studies show that KW get attenuated during westerlies and their amplitudes maximise during easterlies and westerly shears. In the present study, however, the eastward propagating KW crossed the westerly lower stratosphere as the vertical extent of the westerly wind regime was less than the vertical wavelengths of the KW. The waves might have deposited eastward momentum in the upper stratosphere at 26–40 km, thereby reducing the magnitude of the easterly wind by as much as 10 m s−1. The outgoing long wave radiation (OLR) is also investigated and it is found that these KW are produced due to deep convections in the lower atmosphere.

During the passage of typhoon Kujira in April 2003 near to the northeast of Taiwan, atmospheric radar at Chung-Li (24°58′N, 121°11′E) was continuously operated. The data collected from profiler radar was used to investigate the impact of typhoon on generating waves and other atmospheric disturbances. Result showed that the typhoon and the associated wind disturbances can generate atmospheric waves with varied periodicity even when the core was far away from the land. The waves were quite prominent when the core was closer to the mountain. Observations show that these waves propagate vertically upward for many kilometers and getting trapped in higher altitudes. The radar reflectivity at the tropopause during the event showed that stable layer structure was very weak. Further, the enhancement in ozone measurement at the ground level was observed when the typhoon was near to radar site.

The present study analyzes and quantifies the spatial-temporal variability of outgoing longwave radiation (OLR) over peninsular Malaysia using the continuous wavelet transform (CWT) from 2003 to 2010. The goal is to understand the long-term variability of OLR over Malaysia in terms of time-frequency variations in relation to the monsoon period and other weather phenomena. The study regions selected were the west coast, east coast, and southern part of peninsular Malaysia. The OLR variation characteristics in time and space derived from wavelet transform were found to be distinctly different in these three regions. In these three regions, OLR showed significant periodicities dominated by the annual cycle, followed by a semiannual cycle. The west coast of peninsular Malaysia has a lower annual component compared to the other regions because of the rain-sheltering effect by the mountain range that blocked the heavy rainfall from northeast monsoon winds. Besides that, the results show that the wet and dry spells coincide with local monsoon and intermonsoon periods. Meanwhile, the results also revealed that the semiannual variation is statistically significant during 2004-06. The strong semiannual variation is coincident with several droughts that resulted from the strong El Nino events in 2004-06. In addition, the phase plot of wavelet coefficients shows that the variations at various scales are in phase, which coincided with the sudden variations of OLR, indicating heavy flood occurrences in the southern part of peninsular Malaysia. The results show that CWT is a powerful tool for analysis of phenomena involving multiscale interactions that exhibit localization in both time and frequency.

We present here a detailed investigation of the mesospheric temperature structure over Taiwan, a subtropical location, using 9 years of observations (March 2002 to October 2010) by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite. The mesopause (MP) is always found to be located at a higher level with a mean altitude of 98.2 +/- 1.8 km and mean temperature of 165.0 +/- 5.8 K. The climatological study shows that MP is lower and warmer during summer and higher and cooler during winter, which is different from the midlatitudes and high latitudes as well as from low latitudes. The temperatures of the mesospheric temperature inversions (MTI) and secondary minimum (SM), on the other hand, are lower during summer and higher during winter, and their altitudes do not show any annual variation. It is found that the thermal structure over Taiwan undergoes a phase shift between 89 and 95 km, and above this region it is in phase with the solar flux. Since MP is always above these altitudes, it shows a seasonal variation that is in phase with the solar energy inputs, and the temperatures below (that of MTI and SM) show the opposite seasonal variation caused by mesospheric adiabatic cooling and warming processes.

Temperature data from Global Positioning System based Radio Occultation (GPS RO) soundings of the Formosa Satellite mission 3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC or F-3/C) micro satellites has been investigated in detail to study the Kelvin wave properties. The high temporal and spatial resolution satellite data from August 2006 to August 2009 have enabled the investigation of Kelvin wave activity on each day. The dominant waves of wave numbers 1 and 2 (W1 and W2) have been investigated in detail at three altitudes-19, 25 and 30 km, and it is found that the amplitude of W1 is greater than that of W2 during 60% of the time. A statistical study of the amplitudes of W1 and W2 is also presented and it is found that the dominant amplitudes are 0.5 to 1.0 K for both waves. At lower altitudes (19 km), the amplitudes of W1 are larger and the distribution is also broader. The amplitudes of both waves in the stratosphere are higher during the easterlies of the quasi-biennial oscillation (QBO) and are maximum when the zonal wind changes from easterlies to westerlies. In the lower altitudes near the tropopause they vary in consonance with the outgoing long wave radiation, a proxy of deep convection. Deduction of the Kelvin wave periods and phase velocities has been possible with better accuracy with the use of the F-3/C data. The average periods of W1 for all years are 15 +/- 3, 13 +/- 4, and 10 +/- 3 days at altitudes 19, 25, and 30 km, respectively and the average periods of W2 for all years are 10 +/- 2, 7 +/- 2, and 6 +/- 2 days, respectively. These standard deviations are geophysical and are due to the variation in the periods of the individual Kelvin wave events and identification of the period for a single Kelvin wave event is correct to within +/- one day. We found that the Kelvin waves of both the zonal wave numbers are slow in the lower altitudes and fast in the higher altitudes. Also, the periods decrease gradually with height. This is the most important result of the present study.

A sixteen year long dataset of mesospheric OI 557.7 nm green line nightglow emission rate, measured over Kiso (35.79°N, 137.63°E), Japan using ground-based photometers is spectrally investigated using the Hilbert-Huang Transform (HHT). The spectrograms reveal the presence of semi-annual, annual and quasi-biennial oscillations in consonance with the results obtained from wavelet analysis in an earlier study. In addition, due to the use of the HHT, we have been able to investigate the very low frequency solar cycle variation in the emission rate. It is found that there is a significant solar cycle effect on the oxygen green line emission rate. The mean amplitude of variation is approximately 20% and it is also found that it is maximum at midnight. A correlation study between the means of the emission rate and the solar radio flux at 10.7 cm also shows that the effect of solar activity on the oxygen green line emission rate is maximum at midnight.

This paper describes some of the microphysical and kinematic properties of precipitating systems associated with a typhoon using Chug-Li VHF radar. In order to gain a better understanding of these mechanisms and the vertical structure of the precipitation associated with a typhoon at different stages of development, an analysis has been carried out of the radar back-scattered signal in order to obtain the power, velocity and velocity width of the Doppler spectrum of clear air and hydrometeors. The vertical profiles of raindrop size distribution (DSD) parameters are estimated through model-based regression analysis. The study reveals that during a typhoon, different convective and stratiform types of precipitation occur at different times with varying intensities. This study also reports on some of the characteristic features of the convective systems observed during the typhoon.

L-band wind profiler data are utilized to diagnose the vertical structure of the typhoon precipitating cloud systems in Taiwan. For several typhoons, a pronounced bright band (BB) around 5 km is commonly observed from the observation. Since strong convection within typhoon circulation may disturb and/or disrupt the melting layer, the BB shall not appear persistently. Hence, an understanding of the vertical structure of the BB region is important because it holds extensive hydrometeors information on the type of precipitation and its variability. Wind profiler observational results suggest that the mixture of convective and stratiform (embedded type) clouds are mostly associated with typhoons. In the case of one typhoon, BB is appeared around 5.5 km with embedded precipitation and also BB height of 1 km higher than ordinary showery precipitation. This is evident from the long-term observations of wind profiler and Tropical Rainfall Measuring Mission. The Doppler velocity profiles show hydrometers (ice/snow) at 6 km but liquid below 5 km for typhoons and 4 km for showery precipitation. In the BB region the melting particles accelerations of 5.8 ms−1 km−1 and 3.2 ms−1 km−1 are observed for typhoon and showery precipitation, respectively.

The interaction of the storm circulation with the Central Mountain Range (CMR) of Taiwan is studied with a wind profiler located at the leeside during the invasions of two (Kaemi (200605) and Bopha (200609)) typhoons. The moderate typhoon Kaemi upgraded from a tropical depression on 21 July 2006. It then was made landfall at 15:45 UTC on 24 July 2006 near Cheng-Kung. The weak typhoon Bopha formed at about 12:00 UTC on 5 August 2006 and also landed near Cheng-Kung at around 19:20 UTC on 8 August. A new finding from both typhoons is the vortex splitting into upper and lower parts with the two typhoons that have passed the observation site nearly. For the typhoon Kaemi, demarcation height of the upper-level vortex and lower level is at 2.8 km and passed the site about 3 h earlier than the low-level one. For the typhoon Bopha, the center of the lower-level vortex at 3.5 km locates to the north of the upper-level one at 5.2 km. The re-organization of the split vortexes is found in typhoon Kaemi but not for typhoon Bopha.

Two typhoons Kaemi (200605) and Bopha (200609) crossing over Taiwan were continuously monitored by a wind profiler radar located on the lee side of the Central Mountain Range (CMR) of the island. Wind fields rotating systematically associated with the storm passage is pronounced for both typhoons. Nevertheless, significant wind shear takes place above and below the altitude of about 3.5 km owing to the mountain blocking before typhoon landing is reported in this paper for the first time. Winds deflected due to the orography behave diversely with respect to different typhoon tracks and strengths that may cause a secondary circulation to modify the original one. In this study, a moderate typhoon, Kaemi re‐organizes the winds from the CMR blocking after landfall. On the other hand, weak typhoon Bopha shows a very complicated wind pattern structure from this typhoon‐orography interaction. As the winds are disturbed dramatically, it dissipates over the sea soon after the typhoon center leaves Taiwan.

In this study, III-nitride solar cells with multi-quantum well (MQW) absorption layer were grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD). The effect of different quantum well (QW) arrangement on optoelectronic characteristics of III-nitrides photovoltaic cells was investigated. It was found that the upper quantum well (QW) layer will dominate electroluminescence (EL) emission mechanism and the electrical characteristics of solar cell. The advantage of modulating the short-circuit current density (J(SC)) and open-circuit voltage (V-OC) can be obtained by different arrangement of blue and green QW in MQW absorption layer. The optimum electrical characteristics of solar cell with a J(SC) of 0.30 mA/cm(2), a V-OC up to 1.51 V, fill factor (FF) as high as 0.601, and a series resistance (R-S) of 9 Omega can be obtained by using MQW absorption layer. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

ZnO nanowires were grown on a-plane GaN templates by chemical vapor deposition (CVD) without employing a catalyst. The a-plane GaN templates were pre-deposited on an r-plane sapphire substrate by metal-organic CVD. The resulting ZnO nanowires grow in angles off- related to the GaN basal plane. X-ray diffraction (XRD) spectra showed that the ZnO layer was grown with a heteroepitaxial relationship of (110)ZnO||(110)GaN. Photoluminescence spectra measured at 17K exhibited near-band-edge emission at 372nm with a full width at half maximum of 10nm. The growth mechanism on a-GaN was the Volmer-Weber (VW) mode and differed from the Stranski-Krastanow (SK) mode observed for growth on c-GaN. This difference results from the higher interfacial free-energy on the a-plane between ZnO and GaN than that on the c-plane orientation.

ZnO nanostructures were grown on a-plane GaN templates by chemical vapor deposition (CVD) without employing a catalyst. The a-plane GaN templates were pre-deposited on an r-plane sapphire substrate by metal-organic CVD. For the 800{degree sign}C-grown sample, a ZnO layer with a thickness of 0.1 μm was formed by grains with a size of about 40 nm. For the 900oC-grown sample, ZnO nanowires were grown in angles off-related to the GaN basal plane with a ZnO layer between wires and template formed by grains with a size of about 300 nm. X-ray diffraction spectra showed that the ZnO layer was grown with a heteroepitaxial relationship of (110)ZnO||(110)GaN. The growth mechanism on a-plane GaN was the Volmer-Weber mode and differed from the Stranski-Krastanow mode observed for growth on c-plane GaN. This difference results from the higher interfacial free-energy on the a-plane between ZnO and GaN than that on the c-plane orientation.

Single crystal ZnO nanowires diffused with europium (Eu) from a solid source at 900°C for 1h or doped with Eu during growth have been characterized. The ZnO nanowires were grown by chemical vapor deposition on Si substrates employing Au as a catalyst. The diameter of the resulting nanowires was ∼200nm with a length of 1μm. Photoluminescence spectra excited by a He–Cd laser at room temperature showed the green luminescence at 515nm in Eu-diffused nanowires. A small red shift of near-band-edge emission of ZnO nanowires was observed in the diffused wires, but sharp emission from Eu3 ions was not present. Transmission electron microscopy shows crystalline Eu2O3 formation on the diffused nanowire surface, which forms a coaxial heterostructure system. When Eu was incorporated during the nanowire growth, the sharp 5DO–7F2 transition of the Eu3+ ion at around 615nm was observed.

ZnO nanowires were grown on Si (100) substrates with and without Au catalyst by chemical vapor deposition employing the vapor–liquid–solid (VLS) and vapor–solid (VS) mechanisms, respectively. The diameters of the resulting nanowires were in the range 80–150nm with typical length about 10μm. The near-band-edge (NBE) emission of ZnO nanowires grown with and without catalyst was observed at 382nm and 386nm, respectively. The intensity of the NBE emission of ZnO nanowires grown without the catalyst was higher than that of the green luminescence. By sharp contrast, the intensity of the NBE emission of ZnO nanowires grown with catalyst was lower than that of green luminescence. The X-ray diffraction (XRD) spectrum of the ZnO nanowires grown without catalyst exhibited a peak intensity of c-plane 5 times higher than that of m-plane and 10 times higher than that of a-plane. However, the XRD spectrum of the ZnO nanowires grown with catalyst exhibited a peak intensity of the c-plane about 1.5 times higher than that of the m-plane and 4 times higher than that of a-plane intensity. Thus, the ZnO nanowires grown without catalyst have a preferential orientation along the c-axis direction. Our results show that the catalyst strongly effects optical and structural properties of the ZnO nanowires.