若是逐日資料，則原始逐日資料減去對應(yīng)這一日的氣候態(tài)，就去掉了年循環(huán)（或者季節(jié)循環(huán)），只剩下低頻信號，年際信號，年代際信號了。

若原始資料是逐月資料，則減去對應(yīng)月份的氣候態(tài)，就去掉了年循環(huán)，只剩下年際、年代際等異常信號了。

去除全球變暖趨勢，可采用直接去掉最小二乘線性趨勢

Hi, Jianping

With regarding to your question about figure 4 you sent me by Wechat, here is my explanation. If you horizontal wind to indicate circulation change, there is no need to remove global mean.

??????When you ?use geopotential height as an indicator of anomalous circulation you need to remove the global mean since global warming will raise geopotential height everywhere. ?Anomalous circulation is related to the gradient of geopotential height and therefore global mean height does not contribute to circulation change and removing global mean height does not affect circulation at all. Removing zonal mean further emphasize wave like pattern of circulation since it only remove a constant of zonal wind at each latitude circle, but does not affect meridional wind at all. ?Therefore, ?in order to illustrate anomalous circulation changes with global warming by using height variable, you have to remove the global mean. In order to emphasize zonally asymmetric of circulation (wave pattern), you can remove zonal mean as well. Hope this is clear.

Regards

Buwen ?

?

計算說明：1. 1979-2013年夏季（JJA平均）ERAI的海平面氣壓和500 hPa位勢高度分別減去各自的全球平均，再去趨勢，最后與基于ERAI計算的已去趨勢的HWI的相關(guān)關(guān)系，以及N216中historical的海平面氣壓和500 hPa位勢高度分別減去各自的全球平均，再去趨勢，最后與基于historical計算的去趨勢的熱浪指數(shù)的相關(guān)系數(shù)空間分布，其中相關(guān)系數(shù)計算是利用NCL自帶的皮爾遜相關(guān)的函數(shù)計算得來。

計算說明：1. 1979-2013年夏季（JJA平均）ERAI的海平面氣壓和500 hPa位勢高度分別減去各自的緯向平均，再去趨勢，最后與基于ERAI計算的已去趨勢的HWI的相關(guān)關(guān)系，以及N216中historical的海平面氣壓和500 hPa位勢高度分別減去各自的緯向平均，再去趨勢，最后與基于historical計算的去趨勢的熱浪指數(shù)的相關(guān)系數(shù)空間分布，其中相關(guān)系數(shù)計算是利用NCL自帶的皮爾遜相關(guān)的函數(shù)計算得來。