Analysis of the Equatorial Lower Stratosphere Quasi-Biennial Oscillation (QBO) Using ECMWF-Interim Reanalysis Data Set

The ERA-Interim data set from Europe Center for Medium Range Weather Forecasting (ECMWF) was used to quantitatively analyze the characteristic of equatorial quasi-biennial oscillation (QBO). Analysis of spatial and temporal of the data showed that the zonally symmetric easterly and westerly phase of QBO regimes alternate with period of ~27.7 months. Based on Equivalent QBO Amplitude (EQA) method, the maximum amplitudes in zonal mean zonal wind (u), temperature (T), vertical shear (du/dz) and quadratic vertical shear (d2u/dz2) are ~28.3 m/s, ~3.4 K, ~4.8 m/s/km, and ~1.0 m/s/km2 respectively. The amplitudes decay exponentially with a Gaussian distribution in latitude. The twofold-structure of QBO descends downward at rate of ~1 km/month. The temperature anomaly can be used to analyze the characteristic of QBO which satisfies the thermal wind balance relation in the lower- stratosphere due to very small contribution of the mean meridional and vertical motion. Moreover, the concentration of the total column ozone (TCO) in the tropics is significantly influenced by QBO. During the westerly phase of QBO, the TCO is relatively increased in the lower-stratosphere, but decreased during the opposite phase

Impact of ENSO on seasonal variations of Kelvin Waves and mixed Rossby-Gravity Waves

Characteristics of atmospheric equatorial Kelvin waves and mixed Rossby-Gravity (MRG) waves as well as their relationship with tropical convective activity associated with El Niño-Southern Oscillation (ENSO) were analyzed. Kelvin waves and MRG waves were identified by using a Space-Time Spectral Analysis (STSA) technique, where the differences in the strength of both waves were quantified by taking the wave spectrum differences for each ENSO phase. Our result showed that Kelvin wave activity is stronger during an El Nino years, whereas the MRG wave activity is stronger during the La Nina years. Seasonal variations of Kelvin wave activity occurs predominantly in MAM over the central to the east Pacific in the El Nino years, while the strongest seasonal variation of MRG wave activity occus in MAM and SON over the northern and southern Pacific during La Nina years. The local variation of Kelvin wave and MRG wave activities are found to be controlled by variation in lower level atmospheric convection induced by sea surface temperature in the tropical Pacific Ocean

Characteristics of Kelvin waves and Mixed Rossby-Gravity waves in opposite QBO phases

A 35-year ERA-Interim dataset from the European Center for Medium-Range Weather Forecasts (ECMWF) was used to study the characteristics of Kelvin waves and Mixed Rossby-gravity waves based on a Space-Time Spectral Analysis (STSA). The results show that Kelvin wave activity is stronger during easterly QBO phases, while Mixed Rossby-gravity waves are stronger during westerly QBO phases. Analysis on seasonal variations indicates that the Kelvin waves and Mixed Rossby-Gravity wave activities increase in JJA and SON, respectively. This is associated with a variation of basic mean flow in the lower stratosphere. In addition, the variations of Kelvin and Mixed Rossby-Gravity waves in the troposphere are not significantly affected by the QBO phases. In the troposphere, both Kelvin waves and Mixed Rossby-Gravity waves propagate with a lower phase speed compared to those observed in the stratosphere. This behavior is to be likely due to large

Impact of Madden-Julian Oscillation (MJO) on global distribution of total water vapor and column ozone

The Madden-Julian Oscillation (MJO) is the leading mode of intra-seasonal variability in the tropical troposphere, characterized by an eastward moving 'pulse' of cloud and rainfall near the equator. In this study, total precipitable water (TPW) and total column ozone (TCO) datasets from ECMWF ERA-Interim reanalysis were used to analyse the impact of the MJO on the distribution of water vapor and column ozone in the tropics from 1979 to 2013. The results show that seasonal variations of TPW modulated by the MJO are maximized in the tropics of about 10°S-10°N during boreal winter, while the variation in TCO is maximized in the mid-latitudes of about 30°S - 40°N in the same season. The composite analysis shows that MJO modulates TPW and TCO anomalies eastward across the globe. The underlying mechanism of the MJO's impact on TPW is mainly associated with variation of tropical convection modulated by the MJO, while the underlying mechanism of the MJO's impact on TCO is mainly associated with an intra-seasonal variability of tropopause height modulated by the MJO activity. This knowledge helps to improve the prediction skill of the intra-seasonal variation of water vapor and column ozone in the tropics during boreal winter

Equatorial Atmospheric Kelvin Waves In Indonesia Region Based On Ncep/Ncar Reanalysis Data

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Kuantifikasi Osilasi Kuasi Dua Tahunan Stratosfer (QBO) Menggunakan Data Ecmwfinterim Reanalysis

Hlm.153-16