一个诊断极区平流层温度变化的近似方程的检验及应用

根据一个诊断极区平流层温度变化的近似方程及其滑动累加计算方案,采用1980—2000年的MERRA-2再分析日资料计算了北半球极区低平流层100 hPa逐月的温度增量项、动力加热项和非绝热加热项,以及各项的线性趋势。结果表明,各月温度增量项与累积的动力和非绝热加热之和在气候平均的年循环意义上接近平衡,而且它们的趋势也近似平衡。进一步通过多元回归,得到了动力和非绝热加热作用对当前月温度趋势的分别贡献,动力作用是北极低平流层冬季温度趋势的主导因素并且在冬季内不一致,而非绝热作用在其他季节是主导因素。

Verification and application of an approximate thermodynamic equation for diagnosing the polar stratospheric temperature changes

Temperature changes in the Arctic lower stratosphere on both the short-and long-term timescales are critical for changing the magnitude of ozone losses in the Arctic vortex.In the present paper,first we give an approximate thermodynamic equation,which is in the form of that described by Hu and Tung (2002),for diagnosing the polar stratospheric temperature changes,along with its time-sliding calculation scheme.Next,according to this scheme and using the MERRA-2 reanalysis daily data for the period of 1980-2000,we calculate the terms of monthly temperature increment,dynamical heating and diabatic heating,as well as their respective linear trends,at 100 hPa in the Arctic lower stratosphere.The results show that the monthly temperature increment term and sum of the cumulative dynamical and diabatic heating,as well as their trends,are approximately balanced during the annual cycle of climatological average.Then,based on a multivariate linear regression,we further obtain the respective contributions of the dynamical and diabatic heating to the current month temperature trends.It is shown that the dynamical contribution to the temperature trend is dominant and varied with the different months in the Arctic lower stratosphere wintertime,while the diabatic contribution is dominant in other seasons.This is particularly pertinent to the attribution of decadal scale Arctic stratospheric temperature changes,due to the internal dynamics variability and anthropogenic climate forcings.In future work,it would be desirable to determine the reasonable range of the eddy heat flux approximation with regard to the reference latitude,pressure height and integration timescale,as well as to disclose more application aspects of the simplified thermodynamic energy equation.An assessment for the relative impact of each deviation factor is also required to obtain an accurate explanation for sources of some large departures and limits of the approximate temperature change equation.Of course,verifications and comparisons using greater numbers of and more varied data sets are required.