Possible solar forcing of interannual and decadal stratospheric planetary wave variability in the northern hemisphere: An observational study |
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| Authors: | Alfred M Powell |
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| Institution: | 1. NOAA/NESDIS/Center for Satellite Applications and Research (STAR), Camp Springs, MD, USA;2. IMSG at NOAA/NESDIS/STAR, 5200 Auth Road, WWB, Camp Springs, MD 20746, USA;1. State Key laboratory of tropical oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, PR China;2. Institute of Space and Earth Information Science, The Chinese University of Hong Kong, Hong Kong, PR China;3. Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, PR China;4. College of Marine Science, Nanjing University of Information Science and Technology, Nanjing, Jiangsu 210044, PR China;5. South China Sea Branch, State Oceanic Administration, Guangzhou 510301, PR China;1. State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, People''s Republic of China;2. College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266003, People''s Republic of China;1. Key Laboratory of Meteorological Disaster, Ministry of Education (KLME)/Joint International Research Laboratory of Climate and Environmental Change (ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Nanjing University of Information Science and Technology, Nanjing, China;2. International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii, 2525 Correa Rd., Honolulu, HI 96822, USA |
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| Abstract: | The variability of stratospheric planetary waves and their possible connection with the 11-year solar cycle forcing have been investigated using annual-mean temperatures for the period of 1958–2001 derived from two reanalysis data sets. The significant planetary waves (wavenumbers 1–3) can be identified in the northern mid-high latitudes (55–75°N) in the stratosphere using this data. Comparisons with satellite-retrieved products from the Microwave Sounding Unit (MSU) confirm the significant planetary wave variability seen in the reanalyses. A planetary wave amplitude index (PWAI) is defined to indicate the strength of the stratospheric planetary waves. The PWAI is derived from Fourier analysis of the temperature field for wavenumbers 1–3 and averaged over 55–75°N latitude and the 70–20 hPa layers. The results include two meaningful inter-annual oscillations (2- and 8-year) and one decadal trend (16-year) that was derived from wavelet analysis. The stratospheric temperature structure of the wave amplitudes appear associated with the Arctic Oscillation (AO) which explicitly changed with the PWAI. The temperature gradients between the polar and mid-high latitudes show opposite tendencies between the top-10 strong and weak wave regimes.The variation of the planetary wave amplitude appears closely related to the solar forcing during the recent four solar cycles (20–23). The peak of the 2-year oscillation occurs synchronously with solar minimum, and is consistent with the negative correlation between the PWAI and the observed solar UV irradiance. The UV changes between the maxima and minima of the 11-year solar cycle impact the temperature structure in the middle-lower stratosphere in the mid-high latitudes and hence influence the planetary waves. During solar maximum, the dominant influence appears to be exerted through changes in static stability, leading to a reduction in planetary wave amplitude. During solar minimum, the dominant influence appears to be exerted through changes in the meridional temperature gradient and vertical wind shear, leading to an enhancement of planetary wave amplitude. |
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