The Effects Of Tropospheric Biennial Oscillation (TBO) On El Ni(?)o-Southern Oscillation

Tropospheric biennial oscillation (TBO) is a very significant and important signal of annual-scale atmospheric circulation and climate change, and is one of the themes of the International Monsoon Study. El Nino-Southern Oscillation (ENSO) is the strongest ocean-atmosphere coupled system that significantly impacts the weather and climate in our country and the world. While some studies have focused on the effects of ENSO on TBO, understanding the interactions between ENSO and TBO, especially in terms of how TBO modulates ENSO, will help improve the accuracy of short-term climate predictions. Using NCEP/NCAR and ECMWF reanalysis, monthly extended reconstructed sea surface temperature (ERSST) version 3.0 (ERSST.v3) data, monthly thermocline layer data based on Simple Ocean Data Assimilation (SODA), and the Precipitation Reconstruction data set, the effects of TBO on ENSO were studied with power spectral, filtering, correlation, and EOF analyses.Power spectral analysis was used to prove significant quasi-biennial oscillations in the average time series (including wind, temperature, humidity, geopotential height, and pressure vertical velocity) of all the climate variables over the Northwestern Pacific,120-160°E,5-20°N; South China Sea,105-120°E,5-20°N; Southeastern Indian Ocean,90-100°E,15°S-5°N; and Maritime Continent, 100-120°E,10°S-10°N (the vertical direction, from 1000-100 hPa, specific humidity from 1000-300 hPa, except for the v variable over the Southeastern Indian Ocean and Maritime Continent). The phase relationships of the quasi-biennial oscillations of all the climate variables in all regions were also studied.The TBO of the South China Sea summer monsoon (SCSSM) was also used to study the effects of TBO on ENSO. Air-sea interactions obtained, which are associated with SCSSM quasi-biennial changes, showed influences in both the tropical Indian Ocean and the Pacific. Each of the SSTAs in the tropical northern Indian Ocean and the eastern Central Pacific include a positive feedback process with the SCSSM on a quasi-biennial scale. In contrast, only one major positive feedback is found in the eastern Central Pacific. Two negative feedback processes are found here as well.The joining area of the Asia and Indian-Pacific Ocean (AIPO) is a key air-sea interaction area that affects short-term climate variability. The spatial-temporal distribution of sea surface temperatures in the joining area of the AIPO and its impacts on precipitation in East Asia are discussed in the next section.There are two main SST modes in the AIPO:the first is an all-region type, and the second is the eastern and western distribution pattern. All region-type SSTs have a clear upward trend. The decadal cycle of EOF 1 is significant and has a significant impact on SST changes in the Northern Pacific. SST anomalies of EOF2 are mainly observed in the annual cycle, show variations in quasi-biennial oscillation, and last for 4-5 years. The SST in the Nino-3.4 region has a significant effect on the SST anomalies of EOF2. The SST anomalies of EOF2 lead to precipitation anomalies in the Northwestern Pacific and Northeast and North China. Such anomalies are important precursor signals of precipitation anomalies in northern China. The SSTs of the EOF1 and EOF2 in the AIPO region have important influences on precipitation in China, the amount of which can be achieved by as much as 12 months in advance. This is an important indicator of the annual-scale precipitation forecast.