Quasi-biennial Variations Research Articles

Interdecadal variability of El Niño onset and its impact on monsoon systems over areas encircling the Pacific Ocean

Based on previous study by Xu and Chan (J Clim 14:418–433, 2001), two types of El Nino distinguished by the onset time, a Spring (SP) type and a Summer (SU) type, have been investigated from 1871 through 2011. As can be classified by the spatial patterns of sea surface temperature anomaly into the Warm Pool (WP) and Cold Tongue (CT) El Nino, the temporal features of the CT are dominated by the SP events whereas the SU events mostly display the spatial pattern of WP or Mixed events. The approximate 140-year data analysis shows that the frequency of SP events tends to increase in the most recent 30 years (1980–2009) while the SU events show very strong activity in the beginning of the twentieth century (1900–1929), which are closely associated with the decadal changes in oceanic and atmospheric background conditions. The air-sea processes indicate that the pattern of sea surface temperature (SST) gradient between tropical and extratropical Pacific Ocean on decadal time scales is related to the sea level pressure distribution, which tends to produce wind anomalies. The wind anomalies in turn affect the SST anomalies on inter-annual time scales over the equatorial areas and finally result in the early onset of El Nino in SP time or late onset of El Nino in SU time. A spring onset El Nino favors a Kelvin wave that propagates across the basin and a summer onset favors a Kelvin wave that does not traverse the basin or the related effects are not strong enough. The early or late onset of El Nino significantly impacts the precipitation distribution correlated with the monsoon systems including the Asian–Australian monsoon and North–South American monsoon. The El Nino–monsoon relationship is modulated by decadal changes in atmospheric and oceanic background conditions. The precipitation in the monsoonal area circling the Pacific Ocean exhibits characteristic quasi-biennial variations that are closely associated with the onset time of El Nino events, especially with the early onset of El Nino. For the Spring (SP) type, drought is observed over the central China, Australia, southwestern North America and northern South America in boreal summer, but the opposite pattern appears in the subsequent summer of the following year.

Sediment-Mass Accumulation Rate and Variability in the East China Sea Detected by GRACE

The East China Sea (ECS) is a region with shallow continental shelves and a mixed oceanic circulation system allowing sediments to deposit on its inner shelf, particularly near the estuary of the Yangtze River. The seasonal northward-flowing Taiwan Warm Current and southward-flowing China Coastal Current trap sediments from the Yangtze River, which are accumulated over time at rates of up to a few mm/year in equivalent water height. Here, we use the Gravity Recovery and Climate Experiment (GRACE) gravity products from three data centres to determine sediment mass accumulation rates (MARs) and variability on the ECS inner shelf. We restore the atmospheric and oceanic effects to avoid model contaminations on gravity signals associated with sediment masses. We apply destriping and spatial filters to improve the gravity signals from GRACE and use the Global Land Data Assimilation System to reduce land leakage. The GRACE-derived MARs over April 2002–March 2015 on the ECS inner shelf are about 6 mm/year and have magnitudes and spatial patterns consistent with those from sediment-core measurements. The GRACE-derived monthly sediment depositions show variations at time scales ranging from six months to more than two years. Typically, a positive mass balance of sediment deposition occurs in late fall to early winter when the southward coastal currents prevail. A negative mass balance happens in summer when the coastal currents are northward. We identify quasi-biennial sediment variations, which are likely to be caused by quasi-biennial variations in rain and erosion in the Yangtze River basin. We briefly explain the mechanisms of such frequency-dependent variations in the GRACE-derived ECS sediment deposition. There is no clear perturbation on sediment deposition over the ECS inner shelf induced by the Three Gorges Dam. The limitations of GRACE in resolving sediment deposition are its low spatial resolution (about 250 km) and possible contaminations by land hydrological and oceanic signals. Potential GRACE-derived sediment depositions in six major estuaries are presented.

On the contribution of sunspots to the observed frequency shifts of solar acoustic modes

Activity-related variations in the solar oscillation properties have been known for 30 years. However, the relative importance of the different contributions to the observed variations is not yet fully understood. Our goal is to estimate the relative contribution from sunspots to the observed activity-related variations in the frequencies of the acoustic modes. We use a variational principle to relate the phase differences induced by sunspots on the acoustic waves to the corresponding changes in the frequencies of the global acoustic oscillations. From the sunspot properties (area and latitude as a function of time), we are able to estimate the spot-induced frequency shifts. These are then combined with a smooth frequency shift component, associated with long-term solar-cycle variations, and the results compared with the frequency shifts derived from the Global Oscillation Network Group (GONG) data. The result of this comparison is consistent with a sunspot contribution to the observed frequency shifts of roughly 30 per cent, with the remaining 70 per cent resulting mostly from a global, non-stochastic variation, possibly related to the changes in the overall magnetic field. Moreover, analysis of the residuals obtained after the subtraction of the model frequency shifts from the observations indicates the presence of a 1.5-yr periodicity in the data in phase with the quasi-biennial variations reported in the literature.

On the relationship between quasi-biennial variations of solar activity, the heliospheric magnetic field and cosmic rays

Quasi-biennial oscillations (QBO) of solar activity (T ≈ 1–4 years) are considered to be a variation of basic solar activity, associated with the solar dynamo process. They are transferred into interplanetary space by the open magnetic flux of the Sun, generating QBO in the intensity of cosmic rays (CR). This paper discusses the observational characteristics of QBO in CR and their relationship with QBO on the Sun and in the interplanetary medium. The delay time of QBO in CR relative to the solar and heliospheric magnetic field suggests that the formation of QBO in the open magnetic flux of the Sun occurs within 3–5 months. The paper considers the question of the prominent periodicity of CR (T = 1.6 years) that has prevailed in CR and in the heliospheric magnetic field for more than 10 years but was not stable over 60 years of observations. Distinctions in the characteristics of QBO and long-term variations of CR suggest features of the mechanism of their formation.

SUN-LIKE MAGNETIC CYCLES IN THE RAPIDLY ROTATING YOUNG SOLAR ANALOG HD 30495

A growing body of evidence suggests that multiple dynamo mechanisms can drive magnetic variability on different timescales, not only in the Sun but also in other stars. Many solar activity proxies exhibit a quasi-biennial ($\sim$2 year) variation, which is superimposed upon the dominant 11 year cycle. A well-characterized stellar sample suggests at least two different relationships between rotation period and cycle period, with some stars exhibiting long and short cycles simultaneously. Within this sample, the solar cycle periods are typical of a more rapidly rotating star, implying that the Sun might be in a transitional state or that it has an unusual evolutionary history. In this work, we present new and archival observations of dual magnetic cycles in the young solar analog HD 30495, an $\sim$1 Gyr-old G1.5V star with a rotation period near 11 days. This star falls squarely on the relationships established by the broader stellar sample, with short-period variations at $\sim$1.7 years and a long cycle of $\sim$12 years. We measure three individual long-period cycles and find durations ranging from 9.6-15.5 years. We find the short-term variability to be intermittent, but present throughout the majority of the time series, though its occurrence and amplitude are uncorrelated with the longer cycle. These essentially solar-like variations occur in a Sun-like star with more rapid rotation, though surface differential rotation measurements leave open the possibility of a solar equivalence.

The features of quasi biennial oscillation influence on total ozone amount distribution

Terms, under which quasi-biennial oscillation variations can significantly influence on distribution changes of total ozone amount in Earth atmosphere, have been revealed. It is determined that plausible correlation areas of studied processes range over subequatorial zone and subtropical jet streams. Such areas location differs for Northern and Southern hemispheres and significantly depends on season of the year

Multi-year ozone concentration and its spectra in Shanghai, China

The periodic properties of surface ozone variation were studied at five stations with different environmental conditions in Shanghai based on multi-year observations of ozone concentration and UV radiation using spectral decomposition methods. The spectra of surface ozone have distinct peaks at semi-diurnal, diurnal, intraseasonal, semiannual, annual, and quasi-biennial periods. The spectra for the frequency band larger than the semi-diurnal follow a −5/3 power law at all the stations. The diurnal peak values for all stations in different years are similar to each other, while the semi-diurnal peak values are somewhat different among the stations. The peak value of semi-diurnal cycle at the station Dongtan (ecological environment area) is smaller than that at the other stations. The monthly mean of surface ozone has a significant seasonal variation with a maximum in May, a secondary maximum in fall, a lower value in summer (July and August), and a minimum in December or January. However the seasonal variation of UV radiation monthly mean shows a relatively higher value in summer (July and August), and for other months it is closely related to the ozone monthly mean. These secondary peaks of the ozone monthly mean in fall might be caused by the UV radiation coming back to its relevant value after falling off during the Asia summer monsoon; it was not related to biomass burning. The intraseasonal cycling of ozone might be related to the MJO (Madden–Julian Oscillation). Further studies are needed to understand the relationship between the local ozone intraseasonal variation and the MJO. The quasi-biennial variation of ozone in Shanghai might be a local reflection of climate change and could be associated with ENSO (El-Nino Southern Oscillation). Further studies will be needed to understand the relationship of the quasi-biennial variation of ozone to ENSO.

Can irregularities of solar proxies help understand quasi-biennial solar variations?

Abstract. We define, calculate and analyze irregularity indices λISSN of daily series of the International Sunspot Number ISSN as a function of increasing smoothing from N = 162 to 648 days. The irregularity indices λ are computed within 4-year sliding windows, with embedding dimensions m = 1 and 2. λISSN displays Schwabe cycles with ~5.5-year variations ("half Schwabe variations" HSV). The mean of λISSN undergoes a downward step and the amplitude of its variations strongly decreases around 1930. We observe changes in the ratio R of the mean amplitude of λ peaks at solar cycle minima with respect to peaks at solar maxima as a function of date, embedding dimension and, importantly, smoothing parameter N. We identify two distinct regimes, called Q1 and Q2, defined mainly by the evolution of R as a function of N: Q1, with increasing HSV behavior and R value as N is increased, occurs before 1915–1930; and Q2, with decreasing HSV behavior and R value as N is increased, occurs after ~1975. We attempt to account for these observations with an autoregressive (order 1) model with Poissonian noise and a mean modulated by two sine waves of periods T1 and T2 (T1 = 11 years, and intermediate T2 is tuned to mimic quasi-biennial oscillations QBO). The model can generate both Q1 and Q2 regimes. When m = 1, HSV appears in the absence of T2 variations. When m = 2, Q1 occurs when T2 variations are present, whereas Q2 occurs when T2 variations are suppressed. We propose that the HSV behavior of the irregularity index of ISSN may be linked to the presence of strong QBO before 1915–1930, a transition and their disappearance around 1975, corresponding to a change in regime of solar activity.

Climatology of global gravity wave activity and dissipation revealed by SABER/TIMED temperature observations

Gravity wave activity and dissipation in the height range from the low stratosphere to the low thermosphere (25–115 km) covering latitudes between 50°S and 50°N are statistically studied by using 9-year (January 22, 2002–December 31, 2010) SABER/TIMED temperature data. We propose a method to extract realistic gravity wave fluctuations from the temperature profiles and treat square temperature fluctuations as GW activity. Overall, the gravity wave activity generally increases with height. Near the equator (0°–10°), the gravity wave activity shows a quasi-biennial variation in the stratosphere (below 40 km) while from 20° to 30°, it exhibits an annual variation below 40 km; in low latitudes (0°–30°) between the upper stratosphere and the low thermosphere (40–115 km), the gravity wave activity shows a semi-annual variation. In middle latitudes (40°–50°), the gravity wave activity has a clear annual variation below 85 km. In addition, we observe a four-monthly variation with peaks occurring usually in April, August, December in the northern hemisphere and in February, June, October in the southern hemisphere, respectively, above 85 km in middle latitudes, which has been seldom reported in gravity wave activity. In order to study the dissipation of gravity wave propagation, we calculate the gravity wave dissipation ratio, which is defined as the ratio of the gravity wave growth scale height to the atmosphere density scale height. The height variation of the dissipation ratio indicates that strong gravity wave dissipation mainly concentrates in the three height regions: the stratosphere (30–60 km), the mesopause (around 85 km) and the low thermosphere (above 100 km). Besides, gravity wave energy enhancement can be also observed in the background atmosphere.

Quasi-biennial oscillation in GPS VTEC measurements

The quasi-biennial oscillation, QBO, a well known periodicity in the equatorial stratospheric zonal winds, is also found in ionospheric parameters and in solar and geomagnetic activity indices. Many authors speculated about the link between the QBO in solar and geomagnetic activity and the QBO in atmospheric parameters. In this work we analyze the presence of the QBO in the ionosphere using the Vertical Total Electron Content (VTEC) values obtained from Global Navigation Satellite System (GNSS) measurements during the period 1999–2012. In particular, we used IONEX files, i.e. the International GNSS Service (IGS) ionospheric products. IONEX provide VTEC values around the world at 2-h intervals. From these data we compute global and zonal averages of VTEC at different local times at mid and equatorial geomagnetic latitudes. VTEC and Extreme Ultra Violet (EUV) solar flux time series are analyzed using a wavelet multi resolution analysis. In all cases the QBO is detected among other expected periodicities.Since the main source of variation of free electrons in the ionospheric F2 region, where the maximum concentration occurs, is solar EUV radiation, we conclude that the most important cause attributable to QBO in the ionosphere is the quasi-biennial variability of EUV solar flux. Both QBOs are observed to vary in phase.The percentage of the total signal of the ionospheric QBO at the local times of the maximum photoionization is around 15% independent of magnetic latitude while the respective percentage of the total energy for the EUV solar flux is about 18%.

Solar cycle and quasi-biennial variations in helioseismic frequencies

AbstractThe prolonged period of solar minimum between cycles 23 and 24 has invoked a great deal of interest to understand the origin of the unusually low solar activity. Even though the origin of solar activity is believed to lie in the shear layer at the base of the convection zone, the analysis of helioseismic data seem to orientate us toward the near surface. In this context, we analyze the signature of the quasi-biennial periodicity seen in the oscillation frequencies which may provide additional constraints on the solar dynamo models.

Temporal variations in the acoustic signal from faculae

The integrated brightness of the Sun shows variability on time-scales from minutes to decades. This variability is mainly caused by pressure mode oscillations, by granulation and by dark spots and bright faculae on the surface of the Sun. By analyzing the frequency spectrum of the integrated brightness we can obtain greater knowledge about these phenomena. It is shown how the frequency spectrum of the integrated brightness of the Sun in the frequency range from 0.1 to 3.2 mHz shows clear signs of both granulation, faculae and p-mode oscillations and that the measured characteristic time-scales and amplitudes of the acoustic signals from granulation and faculae are consistent with high-resolution observations of the solar surface. Using 13 years of observations of the Sun's integrated brightness from the VIRGO instrument on the SOHO satellite it is shown that the significance of the facular component varies with time and that it has a significance above 0.99 around half the time. Furthermore, an analysis of the temporal variability in the measured amplitudes of both the granulation, faculae and p-mode oscillation components in the frequency spectrum reveals that the amplitude of the p-mode oscillation component shows variability that follows the solar cycles, while the amplitudes of the granulation and facular components show signs of quasi-annual and quasi-biennial variability, respectively.

Methane Interannual Distribution over Peninsular Malaysia from Atmospheric Infrared Sounder Data: 2003-2009

Methane (CH4) is a significant greenhouse gas (GHG's) with a relatively short atmospheric lifetime of about 12 years, and is released to the atmosphere by biological processes occurring in anaerobic environments. The CH4 is second in importance only to CO2 with regard to its environmental effects, and its relative global warming ability is 23 times that of CO2 over a time horizon of 100 years. The interannual distribution of atmospheric CH4 has been studied in Peninsular Malaysia during the period 2003–2009 using Atmosphere Infrared Sounder (AIRS) data, onboard NASA's Aqua Satellite. The analysis of CH4 above five dispersed stations in the study area shows that the high CH4 growth rates observed at the end of each year can be attributed to the increased emissions from biomass burning and wetlands, and the reduced hydroxyl (OH) sink. In particular, we observe a quasi-biennial variation in CH4 emissions in Peninsular Malaysia, with varying magnitudes in peak emissions occurring in 2004, 2006, and 2008. The seasonal variation in the CH4 fluctuated significantly between northeast (NEM) and southwest (SWM) monsoon seasons. The CH4 value in the NEM season was higher than in the SWM season, and higher in the north regions, above the latitude 4°, than in the rest of area throughout the year. To study the CH4 distribution over peninsular Malaysia for 2009, monthly CH4 maps were generated using the Kriging interpolation technique. The AIRS data and satellite measurements are able to measure the increase in the atmospheric CH4 concentrations over different regions.

Quasi-biennial variations in helioseismic frequencies: can the source of the variation be localized?

We investigate the spherical harmonic degree (l) dependence of the ‘seismic’ quasi-biennial oscillation (QBO) observed in low-degree solar p-mode frequencies, using Sun-as-a-star Birmingham Solar Oscillations Network data. The amplitude of the seismic QBO is modulated by the 11-yr solar cycle, with the amplitude of the signal being largest at solar maximum. The amplitude of the signal is noticeably larger for the l= 2 and 3 modes than for the l= 0 and 1 modes. The seismic QBO shows some frequency dependence but this dependence is not as strong as observed in the 11-yr solar cycle. These results are consistent with the seismic QBO having its origins in shallow layers of the interior (one possibility being the bottom of the shear layer extending 5 per cent below the solar surface). Under this scenario the magnetic flux responsible for the seismic QBO is brought to the surface (where its influence on the p modes is stronger) by buoyant flux from the 11-yr cycle, the strong component of which is observed at predominantly low latitudes. As the l= 2 and 3 modes are much more sensitive to equatorial latitudes than the l= 0 and 1 modes the influence of the 11-yr cycle on the seismic QBO is more visible in l= 2 and 3 mode frequencies. Our results imply that close to solar maximum the main influence of the seismic QBO occurs at low latitudes (<45°), which is where the strong component of the 11-yr solar cycle resides. To isolate the latitudinal dependence of the seismic QBO from the 11-yr solar cycle we must consider epochs when the 11-yr solar cycle is weak. However, away from solar maximum, the amplitude of the seismic QBO is weak making the latitudinal dependence hard to constrain.

ГЕОДИНАМІКА

In the paper the dynamic of solar activity and connected to it the geomagnetic field variations and its ecological disturbance on Ukrainis territory is analyzed. It is shown that solar activity concerning to the cycles with 100–200 years periods is in the state of transition to decreasing. Interconnection of the quasibiennial variations of solar and geomagnetic activities is studied. It is shown that ecological disturbance of geomagnetic field on Ukrainis the Ukrainis territory do not exceed of the quota.

The activity of the solar atmosphere and solar-type stars at 11-year and quasi-biennial timescales

Observations of a time series of solar activity indices are compared with new simultaneous observations of the flux variations of the photospheric and chromospheric emissions of 33 stars during the HK project that were conducted over the past 20 years. In addition to the known cyclic chromospheric emissions of stars in the 11-year time scale, which was discovered at the Mount Wilson Observatory and Stanford University, we found a recurrence that is similar to the quasi-biennial variations of solar radiation fluxes. The results of calculations of the of radiation flux variation periods of stars at the quasi-biennial scale are given.

Possible ozone influence on the quasi-biennial oscillation in the equatorial stratosphere

Crossspectral analysis between the time series of zonal wind velocity in the equatorial stratosphere and the flux of solar UV radiation revealed high coherence between the variations of these two parameters on a quasibiennial scale (24-30 months) in the atmo� spheric layer 500-1 hPa (~6-48.5 km). A lag of the quasibiennial variations in wind velocity behind the quasibiennial variations in the solar radiation flux, the maximum (~ 24 months) of which is located at a level of 100 hPa (16.5 km), decreases with height, and in the stratopause region (~1 hPa), the wind velocity variations are approximately in phase with the varia� tions in the solar radiation flux. This points at the pos� sibility of the influence of quasibiennial variations in the shortwave solar radiation on the quasibiennial oscillation of the zonal wind in the neighborhood of the equatorial stratopause. It has been shown that the meridional gradient and the curvature degree of the meridional profile of ozone concentration in this layer undergo quasibiennial variations such that could be a cause of synchronization between the quasibiennial variations in the wind velocity and thermal variations according to the solar wind equation. 1. The quasibiennial oscillation (QBO) manifests itself most clearly in the change of the direction of the

The Solar Cycle

The Solar Cycle is reviewed. The 11-year cycle of solar activity is characterized by the rise and fall in the numbers and surface area of sunspots. We examine a number of other solar activity indicators including the 10.7 cm radio flux, the total solar irradiance, the magnetic field, flares and coronal mass ejections, geomagnetic activity, galactic cosmic ray fluxes, and radioisotopes in tree rings and ice cores that vary in association with the sunspots. We examine the characteristics of individual solar cycles including their maxima and minima, cycle periods and amplitudes, cycle shape, and the nature of active latitudes, hemispheres, and longitudes. We examine long-term variability including the Maunder Minimum, the Gleissberg Cycle, and the Gnevyshev-Ohl Rule. Short-term variability includes the 154-day periodicity, quasi-biennial variations, and double peaked maxima. We conclude with an examination of prediction techniques for the solar cycle.

Daily distribution Map of Ozone (O3) from AIRS over Southeast Asia

Problem statement: Daily retrieved Ozone (O3) column data for 12 day for periods varying (11-18 August) 2005 and 2003 and (12-19 February) 2005, obtained from the Atmospheric Infrared Sounder AIRS, are utilized to investigate the ozone distribution over the Southeast Asia. Approach: AIRS included on the Earth Observing System (EOS) Aqua satellite launched on 4 May 2002. Ozone (O3) is the gas that naturally present in our atmosphere and is a critical atmospheric trace species in the stratosphere and troposphere. Most ozone resides in the stratosphere. Ozone can be “good” or “bad” for your health and the environment. Closer to Earth, in the air we breathe, Ozone is a harmful pollutant that causes damage to lung tissue and plants; it is a major constituent of smog. Results: The aim of this study was to investigate Daily Distribution map and Indonesia forest fires influences on O3 over Peninsular Malaysia and Thailand. The land use map of the study area was conducted by using total column O3 obtained from AIRS/Aqua Level 3 Daily (AIRX3STD) 1×1° spatial resolution ascending Standard, are used to study the O3 distribution and the impact of Indonesia forest fire. Considerable variations demonstrate annual changes in rainfall and drought patterns in various seasons (dry and wet season). Note such variations in the Ozone emissions over study area, while highest O3 occurs over Industrial, congested urban zones and existence of Swamps and lakes during dry season and a greater draw down of O3 occurs in the pristine marine environment over Surat Thani during wet seasons. Conclusion/Recommendations: In particular, we observe a quasi-biennial variation in O3 emissions from study area with two contrary cases, the higher concentrations around the equatorial regions at dry season and less at wet season. Examining satellite measurements, we find the enhanced O3 emission correlates with occasions of less rainfall during dry season.

Quasi-biennial variations of the total solar flux: Their manifestation in variations of the stratospheric wind and the Earth’s rotation velocity

A detailed representation of variations of the total solar flux I has been obtained by analyzing the regular measurements of this flux by the Nimbus-7 and other spacecrafts. In particular, quasi-biennial variations (QBVs) of the monthly average value 〈I〉 and standard deviation sI within a month interval have been revealed. It is remarkable that the QBVs of sI almost coincide in shape with the QBVs of many solar activity and ionospheric indices, and the QBVs of 〈I〉 are almost in antiphase with the variations of sI. The manifestation of the QBVs of 〈I〉 in some processes on the Earth has been already revealed. A relation between the QBVs of 〈I〉 for solar radiation (according to the Nimbus-7 and ACRIM-2 data) and the QBVs of the zonal stratospheric wind near the equator, as well as the QBVs of the Earth’s rotation velocity, has been found. Many of the considered QBV-processes on the Earth are seemingly attributed to the variations of the total solar flux.