Abstract
A novel dynamically based index that reflects the strength of the regional potential vorticity (PV) intrusion on the 300 K isentropic surface is proposed as a reliable measure of East Asian winter monsoon (EAWM) intensity. The index captures essential aspects of the EAWM, including its climatic influences on East Asia, its continuous weakening trend since the 1980s, and its close relationships with the Siberian high, Arctic Oscillation, and El Niño. The use of a potential vorticity framework enables the definition of a new metric called continuous PV intrusion duration (CPVID), which can be used to monitor and explain wintertime weather extremes like the extreme snowfall event that occurred in south China during January 2008. The CPVID of March is comparable to that of December, indicating that data from this month should be included in estimates of the strength of the EAWM.
| Original language | English |
|---|---|
| Pages (from-to) | 9382-9399 |
| Number of pages | 18 |
| Journal | Journal of Geophysical Research: Biogeosciences |
| Volume | 121 |
| Issue number | 16 |
| DOIs | |
| State | Published - 2016 |
| Externally published | Yes |
Funding
We thank three anonymous reviewers for constructive comments that led to improvement of the manuscript. This work has been jointly supported by the National Basic Research Program of China (2015CB953703 and 2014CB441302), the National Natural Science Foundation of China (41505063), the China Meteorological Welfare Research Fund (GYHY201406007), and the Tsinghua University Initiative Scientific Research Program (20131089356). The reanalysis data sets used in this paper can be downloaded from the following sites: http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis.html (NCEP-NCAR), http://apps.ecmwf.int/datasets/data/era40-moda (ERA40), http://apps.ecmwf.int/datasets/data/era20c-moda (ERA20C), http://www.esrl.noaa.gov/psd/data/gridded/data.20thC_ReanV2c.html (20CR_V2c), and http://jra.kishou.go.jp/JRA-55/index_en.html (JRA55). The Ni?o indices can be downloaded from http://www.esrl.noaa.gov/psd/gcos_wgsp/Timeseries/.