scholarly journals Trends and periodicities of rainfall over north Africa

MAUSAM ◽  
2021 ◽  
Vol 51 (2) ◽  
pp. 155-162
Author(s):  
FAWZIA I. MOURSY
Keyword(s):  
Solar Cycle ◽  
North Africa ◽  
Annual Rainfall ◽  
Quasi Biennial Oscillation ◽  
Using Data ◽  
Biennial Oscillation

Trends and periodicities in the annual rainfall of north Africa are studied using data for 45 stations having record lengths of over 60 year. Increasing or decreasing rainfall tendencies are found over large continuous areas in north Africa. These trends, however, are not significant over all the stations in the areas but only at a few places distributed at random. Wherever a trend is significant, It has persistence or a periodicity of more than 40 year. Quasi- Biennial Oscillation (QBO) is exhibited at several stations in the areas of increasing or decreasing trend. Similarly, the 11-year cycle (solar cycle) is also exhibited in both areas. The QBO and the solar cycle are both present at only six stations.

scholarly journals Analysis of Arctic Spring Ozone Anomaly in the Phases of QBO and 11-year Solar Cycle for 1979–2011

2021 ◽  
Author(s):  
Yousuke Yamashita ◽  
Hideharu Akiyoshi ◽  
Masaaki Takahashi
Keyword(s):  
Solar Cycle ◽  
Climate Model ◽  
Polar Vortex ◽  
Reanalysis Data ◽  
Early Spring ◽  
The Arctic ◽  
Negative Anomaly ◽  
Late Winter ◽  
Quasi Biennial Oscillation ◽  
Biennial Oscillation

Arctic ozone amount in winter to spring shows large year-to-year variation. This study investigates Arctic spring ozone in relation to the phase of quasi-biennial oscillation (QBO)/the 11-year solar cycle, using satellite observations, reanalysis data, and outputs of a chemistry climate model (CCM) during the period of 1979–2011. For this duration, we found that the composite mean of the Northern Hemisphere high-latitude total ozone in the QBO-westerly (QBO-W)/solar minimum (Smin) phase is slightly smaller than those averaged for the QBO-W/Smax and QBO-E/Smax years in March. An analysis of a passive ozone tracer in the CCM simulation indicates that this negative anomaly is primarily caused by transport. The negative anomaly is consistent with a weakening of the residual mean downward motion in the polar lower stratosphere. The contribution of chemical processes estimated using the column amount difference between ozone and the passive ozone tracer is between 10–20% of the total anomaly in March. The lower ozone levels in the Arctic spring during the QBO-W/Smin years are associated with a stronger Arctic polar vortex from late winter to early spring, which is linked to the reduced occurrence of sudden stratospheric warming in the winter during the QBO-W/Smin years.

scholarly journals Stratospheric ozone interannual variability (1995–2011) as observed by Lidar and Satellite at Mauna Loa Observatory, HI and Table Mountain Facility, CA

2012 ◽  
Vol 12 (11) ◽  
pp. 30825-30867
Author(s):  
G. Kirgis ◽  
T. Leblanc ◽  
I. S. McDermid ◽  
T. D. Walsh
Keyword(s):  
Time Series ◽  
Solar Cycle ◽  
Interannual Variability ◽  
Southern Oscillation ◽  
Stratospheric Ozone ◽  
Montreal Protocol ◽  
Quasi Biennial Oscillation ◽  
Mauna Loa ◽  
Table Mountain ◽  
Biennial Oscillation

Abstract. The Jet Propulsion Laboratory (JPL) lidars, at the Mauna Loa Observatory, Hawaii (MLO, 19.5° N, 155.6° W) and the JPL Table Mountain Facility (TMF, California, 34.5° N, 117.7° W), have been measuring vertical profiles of stratospheric ozone routinely since the early 1990's and late-1980s respectively. Interannual variability of ozone above these two sites was investigated using a multi-linear regression analysis on the deseasonalized monthly mean lidar and satellite time-series at 1 km intervals between 20 and 45 km from January 1995 to April 2011, a period of low volcanic aerosol loading. Explanatory variables representing the 11-yr solar cycle, the El Niño Southern Oscillation, the Quasi-Biennial Oscillation, the Eliassen–Palm flux, and horizontal and vertical transport were used. A new proxy, the mid-latitude ozone depleting gas index, which shows a decrease with time as an outcome of the Montreal Protocol, was introduced and compared to the more commonly used linear trend method. The analysis also compares the lidar time-series and a merged time-series obtained from the space-borne stratospheric aerosol and gas experiment II, halogen occultation experiment, and Aura-microwave limb sounder instruments. The results from both lidar and satellite measurements are consistent with recent model simulations which propose changes in tropical upwelling. Additionally, at TMF the ozone depleting gas index explains as much variance as the Quasi-Biennial Oscillation in the upper stratosphere. Over the past 17 yr a diminishing downward trend in ozone was observed before 2000 and a net increase, and sign of ozone recovery, is observed after 2005. Our results which include dynamical proxies suggest possible coupling between horizontal transport and the 11-yr solar cycle response, although a dataset spanning a period longer than one solar cycle is needed to confirm this result.

scholarly journals Connection between the Solar Cycle and the QBO: The Missing Link

2000 ◽  
Vol 13 (2) ◽  
pp. 328-338 ◽  
Author(s):  
Murry Salby ◽  
Patrick Callaghan
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Polar Vortex ◽  
Polar Night ◽  
Quasi Biennial Oscillation ◽  
Missing Link ◽  
New Evidence ◽  
Biennial Oscillation

Abstract Evidence of the solar cycle in stratospheric polar temperature rests on a connection to the quasi-biennial oscillation (QBO) of equatorial wind. New evidence reported here establishes a mechanism for how the solar signature in polar temperature follows from the QBO, which itself is shown to vary with the solar cycle. Equatorial westerlies below 30 mb vary systematically with solar activity, as do equatorial easterlies above 30 mb. Changes in their duration introduce a systematic drift into the QBO's phase relative to winter months, when the polar vortex is sensitive to equatorial wind. Corresponding changes in the polar-night vortex are consistent with the solar signature observed in wintertime records of polar temperature that have been stratified according to the QBO.

scholarly journals Lidar observations of middle atmosphere temperature variability

1995 ◽  
Vol 13 (6) ◽  
pp. 648-655 ◽  
Author(s):  
G. P. Gobbi ◽  
C. Souprayen ◽  
F. Congeduti ◽  
G. Di Donfrancesco ◽  
A. Adriani ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Middle Atmosphere ◽  
Atmospheric Temperature ◽  
Temperature Variability ◽  
Quasi Biennial Oscillation ◽  
Temperature Trends ◽  
Atmosphere Temperature ◽  
Reference Atmosphere ◽  
Lidar Observations ◽  
Biennial Oscillation

Abstract. We discuss 223 middle atmosphere lidar temperature observations. The record was collected at Frascati (42°N–13°E), during the 41-month period January 1989-May 1992, corresponding to the maximum of solar cycle 22. The choice of this interval was aimed at minimizing the temperature variability induced by the 11-year solar cycle. The average climatology over the 41-month period and comparison with a reference atmosphere (CIRA86) are presented. Monthly temperature variability over the full period, during opposite quasi-biennial oscillation phases and on a short-term scale (0.5–4 h), is analyzed. Results indicate the 50–55-km region as less affected by variability caused by the natural phenomena considered in the analysis. Due to this minimum in natural noise characterizing the atmospheric temperature just above the stratopause, observations of that region are well suited to the detection of possible temperature trends induced by industrial activities.

scholarly journals Nonstationary Synchronization of Equatorial QBO with SAO in Observations and a Model

2009 ◽  
Vol 66 (6) ◽  
pp. 1654-1664 ◽  
Author(s):  
Le Kuai ◽  
Run-Lie Shia ◽  
Xun Jiang ◽  
Ka-Kit Tung ◽  
Yuk L. Yung
Keyword(s):  
Angular Momentum ◽  
Solar Cycle ◽  
Natural Period ◽  
Quasi Biennial Oscillation ◽  
Integer Multiple ◽  
Weather Forecasts ◽  
Wave Forcing ◽  
Medium Range ◽  
Biennial Oscillation ◽  
Semiannual Oscillation

Abstract It has often been suggested that the period of the quasi-biennial oscillation (QBO) has a tendency to synchronize with the semiannual oscillation (SAO). Apparently the synchronization is better the higher up the observation extends. Using 45 yr of the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) data of the equatorial stratosphere up to the stratopause, the authors confirm that this synchronization is not just a tendency but a robust phenomenon in the upper stratosphere. A QBO period starts when a westerly SAO (w-SAO) descends from the stratopause to 7 hPa and initiates the westerly phase of the QBO (w-QBO) below. It ends when another w-SAO, a few SAO periods later, descends again to 7 hPa to initiate the next w-QBO. The fact that it is the westerly but not the easterly SAO (e-SAO) that initiates the QBO is also explained by the general easterly bias of the angular momentum in the equatorial stratosphere so that the e-SAO does not create a zero-wind line, unlike the w-SAO. The currently observed average QBO period of 28 months, which is not an integer multiple of SAO periods, is a result of intermittent jumps of the QBO period from four SAO to five SAO periods. The same behavior is also found in the Two and a Half Dimensional Interactive Isentropic Research (THINAIR) model. It is found that the nonstationary behavior in both the observation and model is caused not by the 11-yr solar-cycle forcing but by the incompatibility of the QBO’s natural period (determined by its wave forcing) and the “quantized” period determined by the SAO. The wave forcing parameter for the QBO period in the current climate probably lies between four SAO and five SAO periods. If the wave forcing for the QBO is tuned so that its natural period is compatible with the SAO period above (e.g., at 24 or 30 months), nonstationary behavior disappears.

Associations between the 11-year solar cycle, the quasi-biennial oscillation and the atmosphere: a summary of recent work

1990 ◽  
Vol 330 (1615) ◽  
pp. 577-589 ◽  
Keyword(s):  
Solar Cycle ◽  
Middle Atmosphere ◽  
Opposite Sign ◽  
Correlation Coefficients ◽  
Full Time ◽  
Quasi Biennial Oscillation ◽  
Monte Carlo Techniques ◽  
Two Phases ◽  
The Given ◽  
Biennial Oscillation

Atmospheric elements at all levels from the surface to the top of the middle atmosphere show a probable association with the 11-year solar cycle that can be observed only if the data are divided according to the phase of the quasi-biennial oscillation. In either phase the range between solar extremes is as large as the interannual variability of the given element; and the correlations are statistically meaningful when tested both by conventional and Monte Carlo techniques. The sign of the correlations changes spatially on the scale of planetary waves or teleconnections. As the correlations tend to be of opposite sign in the two phases of the quasi-biennial oscillation, correlating a full time series of an atmospheric element with the solar cycle nearly always yields negligible correlation coefficients.

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