The Analysis On Atmospheric Intraseasonal Oscillation And Its Numerical Simulation

Intraseasonal Oscillation (ISO) is one of the most significant atmospheric oscillationphenomena. It is the important component of climate variability. It is an important linkbetween weather variations, seasonal variation, annual variation and decadal variation. So far,both atmospheric models and coupled models can’t simulate ISO well. It indicates that wehave not understood ISO fully. The further research of ISO can help improve the numericalsimulation and the ability of climate prediction.In our study, we analyse the decadal characteristics of ISO and difference of three kindsof reanalysis data(NCEP/NCAR reanalysis data， NCEP/DOE reanalysis data andECMWF/ERA40reanalysis data). We analyse the numerical simulation of ISO characteristicsin1979-2008with BCC-AGCM2.1and BCC-CSM1.1, the numerical simulation of ISOcharacteristics of East Asia area in the summer of1998with BCC-AGCM2.2,BCC-CSM1.1-M, BCC-AGCM2.1and BCC-CSM1.1. Then we assess the simulation abilityof models by compared with reanalysis data. We find the following points:1. NCEP/NCAR reanalysis data and NCEP/DOE reanalysis data match well in thetropical intraseasonal oscillation’s spatial distribution, intensity and energy propagation.While NCEP/NCAR reanalysis data and ERA40reanalysis data have some distinctions.2. ISO has obvious interdecadal variation characteristics, it cycles for10-18years, andthe decadal variation contributes significantly. ISO is stronger in2001-2010, while is weakerin1991-2000. In the decade of strong ISO, the power spectrum of ISO is strong, theoscillation period is more obvious, and the active areas extend east and move south, theeastward propagating energy centers more in short wave, while the westward propagatingenergy becomes weaker.3. Compared with reanalysis data, the simulation results of850hPa zonal wind ISOindicate that the simulation of spectrum power is stronger. In summer, the simulation ofatmospheric model tends to be more low-frequency, which the coupled model tends to bemore high-frequency. In winter, the simulation of atmospheric model tends to be morehigh-frequency, which the coupled models appear double-centers. The simulation of coupledmodel about the northward propagation is more accurate than that of atmospheric model. Thenumerical simulation of ISO is stronger in the tropical western Pacific Ocean, weaker in thetropical Indian Ocean and the tropical eastern Pacific Ocean. The simulations of ISO’s annualcycle character which is strong in winter and summer and weak in summer and autumn are not good. For the simulation of OLR’s ISO, the two models simulate ISO weaker in thetropical Indian Ocean and the Bay of Bengal, stronger in the tropical Pacific Ocean. Thecoupled model simulates ISO’s annual cycle character better than the atmospheric model.4. For the simulation of the East Asian ISO in the summer of1998, compared withreanalysis data, models simulate wind field well, the atmospheric model simulate it betterthan the coupled in ISO’s zonal and meridional propagation. The simulations of precipitationISO’s meridional propagation are weaker. BCC-AGCM2.2simulates precipitation weaker.BCC-CSM1.1-M started in May can simulate the precipitation in South China well, which isnot good in the middle and lower reaches of the Yangtze River. BCC-CSM1.1-M started inMarch can simulate the precipitation in Southeast China well, which is not good in the middleand lower reaches of the Yangtze River and the west of South China. BCC-AGCM2.1simulate more precipitation in the middle and lower reaches of the Yangtze River, while lessprecipitation in South China. BCC-CSM1.1simulate less precipitation in the middle andlower reaches of the Yangtze River...