摘要
本工作系列讨论大气环流的季节划分和季节突变问题.本文是第一篇,提出普适的概念、理论和方法,使大气环流和其他气候场的季节划分和季节突变定义建立在客观定量的基础之上.首先用两个场的相关系数R作为其相似性度量,也可以用归范化的两个场之差的根方值d作为差异性的度量.当存在着冬、夏季的典型场F_n和F_s时,取任何时刻t函数F与F~*≡(F_w+F_s)/2之差F~'作为变量场,则其与F~'_w≡F_w-F~*的相关系数R_w(t)及标准根方差d_w(t)可以作为F与其冬季典型的相似性或差异性度量.R_w与d_w^2之间有一定关系,一般只研究R_w即可.(1)可以定义冬季对应于1≥R_w(t)>0.5,夏季为-1≤R_w(t)<-0.5,过渡季节为-0.5<R_w(t)<0.5.(2)设由此算得的冬季长度为T_w,由冬至夏的过渡季节(春季)长度为t_w,则1-τ/T_w为由冬至夏的突变性度量.当有理想突变时,τ_w=0,1-τ_w/T_w=1;当季节变化为简谐函数给出时,有1-τ_W/T_w=1/2;而当过渡为缓慢的,就有1-τ_w/T_w《1/2,例如当τ_w=T_w时有1-τ_w/T_w=0.(3)个别年份的季节强度只能由R_w(t)[||F~'||/||F_w~'||]来度量,其中F_w为长期气候平均的典型冬季场.此外,当没有确定的典型函数场时,只能计算函数时间变化系列的滞后相关R_τ(t)和滞后离差d_τ(f),其中τ为时间间隔。
This is the first paper of our series of papers on the seasons of general atmospheric circulation and their abrupt changes. General concept, theory and method which are suitable to the division of seasons and the definition of abruptness of their transitions are developed based on objective and quantitative. Firat of all, the measure of similarity of two fields is defined by their coefficient of correlation, and the measure of their difference by the normalized root-mean-square deviation. In the cases of typical winter field Fw and typical summer field Fs, taking F'w≡FW = F* and F'≡F-F*, where F *≡(Fw+ Fs )/2, the correlation coefficient, Rw(t), between F'(t) and F'K and the associated normalized roormean-square deviation, dw(t), can be taken as suitable measures of the similarity and difference between F ' and the typical winter regime, respectively. Because there is certain relationship between Rw(t) and dw2(t), one can analyze only Rw in most cases. We have: (1 ) Winter regime is defined as 1≤Rw (t)>0.5, summer regimeas -1≤Rw(t)<- 0.5, and transitional seasons as -0. 5<Rw (t) <0. 5. (2) Denoting the lengths of winter and spring (transition from winter to summer.) as Tw and tw, respectively, then 1-τ/Tw is a measure of the abruptness of the transition from winter to summer. We have τw. = 0, and 1-τw/Tw,= 1, if the transition is of ideal abruptness (discontinuous function); while τw=1/2, and 1 -τw/Tw,= 1/2, if the seasonal cycle is given by a harmonic function; but 1 -τw,/Tw.《1/2,if the transition is a slow process, for example, 1 -τw/Tw = 0 if τw=Tw. (3) The intensity of season of an individual year can be represented by Rw(t)[||F '||/|| Fw|| ], where Fw is the climatological mean of Fw for a long enough period. In the case of nonexistence of typical fields, we can only define the persistency and abruptness of transition by calculating the time-lag correlation coefficient and normalized root-mean-square deviation Rτ(t)and dτ(t), respectively, where τ is the interval of time lag. However such definitions are not clear enough unless some other additional criteria are also introduced. Finally, some differences between the regional climate and the climate of larger area are also indicated in the paper.Some applications of the theory to individual years and climatological mean state will be presented in the following paper of our series.
出处
《大气科学》
CSCD
北大核心
1992年第6期641-648,共8页
Chinese Journal of Atmospheric Sciences
关键词
大气环流
季节
划分
变化
Season
Abrubt seasonal change
Measure of similarity.
