Interannual and Interdecadal Variability of Atmospheric Water Vapor Transport in the Haihe River Basin

The seasonal mean atmospheric precipitable water and water vapor transport over the Haihe River Basin (HRB) inNorth China with a focus on their interannual to interdecadal variability, and then the relationships of the interannual andinterdecadal variability of the water cycle over the HRB to the Pacific Decadal Oscillation (PDO) and El Nino-SouthernOscillation (ENSO) phenomena were investigated using the observational and National Centers for Environmental Pre-diction (NCEP) reanalysis data. There was a strong interdecadal variability for the water cycle (such as precipitationand water vapor transport) over the region, with an abrupt change occurring mostly in the mid 1970s. The intensity ofthe East Asian summer monsoon largely affected the atmospheric water vapor transport. Generally, the net meridionalconvergence of the water vapor flux over the region was relatively large before 1965, and it declined gradually from thenon with a further notable decrease since mid 1970s. Zonal water vapor transport was similar to meridional, but with amuch smaller magnitude and no noteworthy turning in the mid 1970s. Results also suggested that the wind field playedan important role in the water vapor transport over the HRB before the mid 1960s, and the interdecadal variability ofthe water cycle (precipitation, water vapor transport, etc.) in the summer was related to the PDO; however, interannualvariation of the water vapor transport could also be related to the ENSO phenomena.

Re-Discussion on East Asian Meiyu Rainy Season

In this paper,the synoptic-climatology of Meiyu in East Asia is discussed.It is proposed that the location of the rain band of Meiyu is stable from the viewpoint of climatology,even though the active(wet)and break(dry)Meiyu are influenced by synoptic systems.The duration and the onset and retreat dates of Meiyu exhibit tremendous interannual variabilities,and thus,they are almost unpredictable in seasonal climate prediction.The Meiyu has been used as a synoptic concept and applied to the operational forecast for many decades by meteorological agencies in East Asian countries.As a result,the prediction of the onset and retreat dates of Meiyu has become an important operational work for meteorological services.This has also misled the public’s and scientists’attention.The northward propagation of the East Asian summer monsoon(EASM)surge associated with the intraseasonal oscillation is closely related to the active and break Meiyu.The activities and propagation of the EASM surge modulate the active/break Meiyu that cause concentrative severe precipitation processes and floods or droughts;hence,the authors suggest changing the current forecasting methodology of Meiyu.It is more meaningful from the scientific as well as application viewpoints to establish the monitoring and forecasting of the EASM surge to replace the current operational forecast of Meiyu after the seasonal progress enters the climatological Meiyu period in a year.