热带夏季风场与对流场季节内振荡传播模比较

Comparison of Propagating Boreal Summer Intraseasonal Oscillation over Tropics Represented by Wind and Convection Fields

利用1979-2007年卫星观测日平均OLR资料以及NCEP/DOE第2套再分析资料中的风场资料,采用有限区域波一频分析、合成分析等方法,分析对比对流层高、低层风场与对流场所表征的热带北半球夏季季节内振荡(BSISO)各种传播模态谱分布气候特征及其年际异常。结果表明:各要素反映的BSISO各种模态的气候特征及其年际变化存在一定差异,总体而言对流层低层风(850hPa纬向风或经向风)与对流比较一致。850hPa经向风(纬向风)所反映的纬向(经向)传播BSISO谱分布气候特征与对流情况最相似。在ENSO发展年,850hPa经向风反映的赤道东传波加强趋势与对流较为一致;850hPa纬向风、经向风反映的北传波变化趋势都与对流相似。在ENSO衰减年,850hPa纬向风(经向风)反映的赤道东传波(赤道外西传波)减弱趋势与对流较为一致;对流以及850hPa经向风、200hPa纬向风和200hPa经向风4种要素都能体现南海及周边地区北传波明显减弱这一特征。对流和850hPa纬向风所反映的北传波与印度洋偶极子模态之间关系一致。

Finite-domain wavenumber-frequency analysis and components analysis are applied to analyze the spectrum climatology and inter-annual anomaly of diversified propagating boreal summer intra-seasonal oscillation （BSISO） over tropics denoted by tropospheric wind field and convection field,based on the daily outgoing longwave radiation（OLR） data and the second set reanalysis data of NCEP/DOE（daily mean is obtained from 4 times observation）.It shows that differences of BSISO climatology and inter-annual anomaly characteristics exist among different elements.Low level wind（850 hPa zonal wind or meridional wind） is more consistent with convection generally.Zonal（Meridional） propagating BSISO climatology characteristics denoted by 850 hPa meridional（zonal） wind is the most similar to those of convection.During the EN-SO developing year,the enhanced tendency of eastward propagating mode at the equator reflected by 850 hPa meridional wind is more consistent with convection;the changing tendency of northward propagating mode reflected by both of 850 hPa meridional wind and zonal wind is similar to convection.The weakened tendency of northward propagating mode over eastern Indian Ocean reflected by 850 hPa zonal wind is more significant.During the ENSO decaying year,the weakened tendency of eastward（westward） propagating mode at the equator（off the equator） reflected by 850 hPa zonal（meridional） wind is more consistent with convection;4 elements（convection,850 hPa meridional wind,200 hPa zonal wind and 200 hPa meridional wind） can exhibit the characteristic that the northward propagation over South China Sea and its border is suppressed,i.e.,this characteristic is resulted from the combination of atmospheric anomaly between upper and low troposphere.The relationship between eastward propagation of BSISO at the equator and BWA mode of Indian Ocean is only presented by convection,and the other 4 elements of wind filed cannot reflect it.Both of convection and 850 hPa zonal wind can reflect the relationship between northward propagation and the Indian Ocean dipole mode.The northward propagation of BSISO over middle and eastern Indian Ocean and South China Sea weakened（enhanced） under positive（negative） dipole mode.The conclusions above indicate that different results would be obtained from different meteorological elements. This is one of the possible causes that the results are not consistent in the past.For different conditions, proper element should be selected for analyzing tropical BSISO.For example,from the view of the forecasting of regional weather and climate,element which indicates the forecasting area well can be chosen based on diagnoses of the remote relationship between weather in forecasting region and the activity of tropical BSISO.