Oscillation In Atmospheric Circulation Research Articles

Trends in the consecutive days of temperature and precipitation extremes in China during 1961–2015

Background and aimsConsecutive climatic extremes have more intense impacts on natural ecosystems and human activities than occasional events. There were many studies about the frequency or intensity of extreme weather events, but few focused on the consecutiveness or continuousness of climatic extremes. We analyzed the temporal and spatial distributions and tendencies in the consecutive temperature and precipitation extremes in China during 1961–2015. MethodsDaily temperature and precipitation data at 1867 meteorological stations over China was used and four consecutive indices of climate extremes, i.e. cold spell duration indicator (CSDI), warm spell duration indicator (WSDI), consecutive dry days (CDD) and consecutive wet days (CWD), were calculated by RClimDex 1.0. Linear trends in the time series of consecutive days of temperature and precipitation extremes were examined and their statistical significance was evaluated using Mann–Kendall test. Results and discussionThere were obvious differences in the spatial distributions of consecutive days of climate extremes in China. During 1961–2015, CSDI and CWD decreased significantly at rates of 0.9 and 0.1 days per decade respectively, while WSDI increased significantly at rate of 0.8 days per decade in China. Spatially, CSDI decreased at rates of 0–3.0 days per decade in almost all parts of China, and WSDI increased at rates of 0–2.0 days per decade in most parts of China. The spatial trends of CDD and CWD were significant only in several regions of China. CSDI and WSDI had higher percent changes than those of CDD and CWD. Changes in the CSDI and WSDI were associated with large-scale oceanic and atmospheric circulation oscillations, such as Atlantic Multidecadal Oscillation (AMO), El Niño/Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). With global warming, there will be fewer cold extremes, more frequent hot extremes and precipitation extremes. ConclusionsGiven the increases in the frequency and intensity of some consecutive climatic extremes and an increasing physical exposure and socio-economic vulnerability to such extremes in China, more strategies and capacities of mitigation and adaptation to consecutive climatic extremes are essential for the local government and climate-sensitive sectors.

The relationship between the wind and waves in the North Atlantic and atmospheric circulation oscillations

Characteristics of wind and waves are computed using the data of instrumental observations on the moored buoys in the northeastern part of the North Atlantic during the cold periods (November–March) of 2009–2013. Their comparison is carried out for different phases of the North Atlantic and East Atlantic oscillations and for the combinations of these phases.

27.3-day and 13.6-day atmospheric tide and lunar forcing on atmospheric circulation

An analysis of time variations of the earth’s length of day (LOD) versus atmospheric geopotential height fields and lunar phase is presented. A strong correlation is found between LOD and geopotential height from which a close relationship is inferred and found between atmospheric circulation and the lunar cycle around the earth. It is found that there is a 27.3-day and 13.6-day east-west oscillation in the atmospheric circulation following the lunar phase change. The lunar revolution around the earth strongly influences the atmospheric circulation. During each lunar cycle around the earth there is, on average, an alternating change of 6.8-day-decrease, 6.8-day-increase, 6.8-day-decrease and 6.8-day-increase in atmospheric zonal wind, atmospheric angular momentum and LOD. The dominant factor producing such an oscillation in atmospheric circulation is the periodic change of lunar declination during the lunar revolution around the earth. The 27.3-day and 13.6-day atmospheric oscillatory phenomenon is akin to a strong atmospheric tide, which is different from the weak atmospheric tides, diurnal and semidiurnal, previously documented in the literature. Also it is different from the tides in the ocean in accordance with their frequency and date of occurrence. Estimation shows that the 27.3-day lunar forcing produces a 1–2 m s−1 change in atmospheric zonal wind. Therefore, it should be considered in models of atmospheric circulation and short and middle term weather forecasting. The physical mechanism and dynamic processes in lunar forcing on atmospheric circulation are discussed.

The frequency composition of the Madden-Julian oscillation. An indication of the solar activity contribution to the global atmospheric circulation and the Earth's rotation

In the series of the solar activity indices, the zonal component of the atmospheric momentum (AAM), and the Earth rotation variations (UT1-TAI), power spectra concentrations at 40, 50, and 60–80 day period are detected. This result indicates the solar origin of the Madden-Julian oscillation in atmospheric circulation and the 50-day oscillation of the Earth's rotation.