ALBERT

Description: Fourteen sesquiterpenoids with an eudesmane C-atom skeleton, including four new ones, (1 β ,5 α ,7 β ,8 β ,11 β )-5-hydroperoxy-1-hydroxyeudesm-4(15)-eno-12,8-lactone ( 1 ), (1 β ,5 α ,7 β ,8 β )-8-(acetyloxy)-5-hydroperoxy-1-hydroxycostic acid methyl ester ( 12 ), and a mixture of (1 β ,3 β ,4 β ,7 β ,8 β )-1,3-dihydroxyeudesma-5,11(13)-dieno-12,8-lactone ( 7 ) and (1 β ,3 β ,4 β ,7 β ,8 β ,11 β )-1,3-dihydroxyeudesm-5-eno-12,8-lactone ( 8 ), were isolated from the aerial parts of Inula japonica (Asteraceae). Their structures were determined by extensive spectroscopic methods, and those of 7 and 12 confirmed by means of single-crystal X-ray diffraction analysis.

Description: Time–latitude variations of the spectral slope S. The dashed lines denote the start of each year. The blank indicates the lack of available data The present study investigates the global vertical wave number spectra of potential energy density in the stratosphere by utilizing the COSMIC temperature data in the period January 2007 to February 2014. The statistical analysis shows that the spectral amplitude (defined as the maximum spectral energy density) varies from 0.1 × 104 m2 s−2 (cycle/m)−1 to 3.2 × 104 m2 s−2 (cycle/m)−1, generally smaller than the theoretical saturated spectral amplitude, with remarkable temporal and spatial variations. Due to the latitudinal and seasonal variations of the background winds and wave sources, the amplitude exhibits obvious quasi‐biennial, annual and semi‐annual cycles at low latitudes, and the annual cycle at middle and high latitudes. The spectral slope, ranging from −1.6 to −3.0, is systematically less negative than the canonical value of −3, and exhibits a quasi‐biennial cycle at low latitudes, annual cycle at middle and high latitudes, and semi‐annual cycle at boreal high latitudes. Different from the amplitude, the slope shows weaker temporal and latitudinal variations, strongly indicating a more universal feature of the slope, which mainly results from the wave propagation process (such as the wave–wave or wave–background flow interactions) rather than the wave source characteristics. Furthermore, we statistically study the longitudinal variation of the spectral parameters. The spectral amplitude at different latitudes shows an obvious and distinctive longitudinal distribution, which is attributed to the latitude‐dependent jet and front mechanisms and/or orography. However, the slope has no evident longitudinal distribution except over around 120°W, 67°W and 85°E. This may be accounted for by the fact that orography‐excited gravity waves are easily influenced by the background winds due to their low frequencies. Interestingly, the amplitude and slope have negative correlation at most latitudes. Larger spectral amplitudes could mean that the gravity wave spectrum is more strongly saturated, resulting in a spectral slope closer to the theoretical value of −3.

Description: Based on the temperature, and zonal and meridional winds observed with a Na lidar at Andes Lidar Observatory (30.3°S, 70.7°W) on the night of 20-21 July 2015, we report simultaneous upward and downward propagating inertia-gravity waves (IGWs) in the mesosphere and lower stratosphere (MLT). The ground-based periods of the upward and downward IGWs are about 5.4 h and 4.8 h, respectively. The horizontal and vertical wavelengths are about 935 km and 10.9 km for the 5.4-h IGW, and about 1248 km and 22 km for the 4.8-h IGW, respectively. Hodograph analyses indicate that the 5.4-h IGW propagates in the direction of about 23° west of north, while the 4.8-h IGW travels northward with an azimuth of 20°clockwise from north. These wave parameters are in the typical IGW wavelength and period ranges, nevertheless, the downward propagating IGWs in the MLT are rarely reported in previous observations. The ray-tracing analysis suggests that the 5.4-h IGW is likely to originate from the stratospheric jet adjustment over the Antarctic, while the 4.8-h IGW source may be above the MLT because it is unlikely to propagate downward through a reflection in the realistic atmospheric wind field. Although both IGWs do not reach their amplitude thresholds of instability, the Richard number reveals that the dynamical and convective instabilities occur intermittently, which indicates that the instability arising from the multiple-perturbation superposition may have a significant influence on wave saturation and amplitude constraint in the MLT.

Description: We adopted 14-year (from 1998 to 2011) radiosonde data from 16 stations at latitudes between 14.33 o S to 29.37 o N to investigate the low frequency oscillations of inertial gravity wave energy densities (including kinetic energy density, potential energy density and total energy density) in the lower atmosphere from 2 km to 30 km. Apparent signatures of 11-year solar cycle and quasi-biennial oscillation (QBO) were found in the gravity wave energy densities in the troposphere and lower stratosphere, respectively. Detailed analyses suggested the 11-year oscillation and QBO of gravity wave activity might be due to the 11-year oscillation of convection activity and zonal wind QBO modulation, respectively. Besides, the gravity wave energy also showed a 35.2-month oscillation in the lower stratosphere, which might be generated by the interaction between the QBO (with the period of 26.7 months) and the 11-year solar cycle, while more possible causes is the direct modulation from the background zonal wind. Our results showed that the QBO signature in gravity wave total energy density could extend northward to over 20 o N in the northern hemisphere, while the 11-year solar cycle in gravity wave activity only extend to lower than 7.5 o N. The oscillation with the period of 35.2 months may be a prolonged QBO in both gravity wave activity and background zonal wind.

Description: A typical application scenario of remote wireless sensor networks (WSNs) is identified as an emergency scenario. One of the greatest design challenges for communications in emergency scenarios is energy-efficient transmission, due to scarce electrical energy in large-scale natural and man-made disasters. Integrated high altitude platform (HAP)/satellite networks are expected to optimally meet emergency communication requirements. In this paper, a novel integrated HAP/satellite (IHS) architecture is proposed, and three segments of the architecture are investigated in detail. The concept of link-state advertisement (LSA) is designed in a slow flat Rician fading channel. The LSA is received and processed by the terminal to estimate the link state information, which can significantly reduce the energy consumption at the terminal end. Furthermore, the transmission power requirements of the HAPs and terminals are derived using the gradient descent and differential equation methods. The energy consumption is modeled at both the source and system level. An innovative and adaptive algorithm is given for the energy-efficient path selection. The simulation results validate the effectiveness of the proposed adaptive algorithm. It is shown that the proposed adaptive algorithm can significantly improve energy efficiency when combined with the LSA and the energy consumption estimation.

Description: The interaction between the tropopause inversion layer (TIL) and the inertial gravity wave (IGW) activities is firstly presented by using a high vertical resolution radiosonde data set at a midlatitude station, Boise, Idaho (43.57°N, 116.22°W) for the period 1998-2008. The tropopause-based vertical coordinate is used for the TIL detection, and for meticulously studying the IGW variation around the TIL, the broad spectral method is used for the IGW extraction. Generally, the TIL at the midlatitude station is stronger and thicker in winter and spring, which is consistent with the previous studies. Our study confirmed the intense interaction between the TIL and IGW. It is found that the TIL not only could inhibit the upward propagation of IGWs from below, but also imply the possible excitation links between the TIL and IGW. The results also indicate that the enhanced wind shear layer just 1 km above the tropopause may result in instability and finally leads to the IGW breaking and intensive turbulence. Subsequently, the IGW-induced intensive turbulence leads to strong wave energy dissipation and a downward heat flux. This downward heat transportation could significantly cooling the tropopause, while has only negligible thermal effect on the atmosphere above the tropopause. Then, the IGW induced cooling at the tropopause make the tropopause colder and sharper and finally form the TIL. These suggest besides previously proposed mechanisms, IGWs also contribute greatly to the formation of TIL, which is consistent with a recent related simulation study.

Description: Abstract The variability in turbulence is a crucial topic in the lower atmosphere. This study aims to validate the credibility of Thorpe analysis in the statistical study of atmospheric turbulence by applying this method on high‐resolution radiosonde data that are a composite of seven sites at mid‐latitudes from January 2012 to December 2016. The spatio‐temporal variability of turbulent energy dissipation rate is also addressed from 2.4 km to 30 km, thereby exhibiting remarkable spatial inhomogeneities and well‐defined seasonal variations. If the ratio between Ozmidov and Thorpe lengths (i.e., c2) is a lognormal distribution, then energy dissipation rate can be simulated by the Monte Carlo method. The approximate proportionalities between the energy dissipation rates revealed by a constant c2 and a lognormally distributed c2 that is based on the results from Schneider et al. [2015] exist at middle, low, and high latitudes. At mid‐latitudes, energy dissipation rates by the simulated cases are quantitatively consistent with the radar results. These results suggest that, even for a highly variable c2, the Thorpe analysis can be statistically applied to the stably stratified free atmosphere, and the optimal value of c2 is 0.54 at all heights and latitudes. We also speculate that the statistical application of a Thorpe sort is acceptable when c2 simply follows a lognormal distribution.