scholarly journals The Physical Mechanisms Behind the Change in the Precipitation Recycling Rate in the Mid- and Lower Reaches of the Yangtze River

2021 ◽  
Vol 9 ◽  
Author(s):  
Wen-Kang Guo ◽  
Xi-Yu Wang ◽  
Wang-Ze Gao ◽  
Jia-Hua Yong ◽  
Xin-Yue Bao ◽  
...  
Keyword(s):  
Water Vapor ◽  
South China Sea ◽  
South China ◽  
External Source ◽  
Recycling Rate ◽  
Northwest Pacific ◽  
China Sea ◽  
Physical Mechanisms ◽  
The Pacific ◽  
Precipitation Recycling

The precipitation recycling rate (PRR) is an important index when trying to understand the physical mechanisms behind the effects of different sources of water vapor on regional precipitation. We studied the change in the PRR in the mid- and lower reaches of the Yangtze River (MLRYR), the correlation between the PRR and the external source of water vapor and local evaporation, and the possible reasons for the interannual variation of the PRR. Our study was based on an evaluation model of the PRR and used precipitation data from meteorological stations in China and NCEP/NCAR reanalysis datasets. Our results show that the mean PRR in the MLRYR for the time period 1961–2017 was largest in autumn (about 0.3) and smallest in summer (about 0.23), with a clear upward trend (passed the 95% significance F-test), except in summer. The highest trend coefficient of the PRR was in autumn (0.38), indicating that the contribution of an external source of water vapor to local precipitation was reduced. The PRR of the MLRYR was strongly correlated with the input of water vapor through the western and southern boundaries. Water vapor was mainly sourced from the Northwest Pacific Ocean, the South China Sea and the Bay of Bengal. The anomalous Northwest Pacific cyclone induced by the Pacific sea surface temperature restrained the input of water vapor into the MLRYR from the Western Pacific, the South China Sea and the Bay of Bengal, contributing to the upward trend in the PRR. We suggest that increases in the sea surface temperature in the Pacific Ocean, South China Sea and especially the Indian Ocean will have an important impact on precipitation in East Asia.

scholarly journals Observations of the Intermediate Water Exchange Between the South China Sea and the Pacific Ocean Deduced From Transient Tracer Measurements

2018 ◽  
Vol 123 (10) ◽  
pp. 7495-7510 ◽  
Author(s):  
Hengxiang Deng ◽  
Peng Huang ◽  
Toste Tanhua ◽  
Tim Stöven ◽  
Hongwei Ke ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
South China Sea ◽  
South China ◽  
Water Exchange ◽  
The South China Sea ◽  
Intermediate Water ◽  
China Sea ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Transient Tracer

Persistent Spring Shortwave Cloud Radiative Effect and the Associated Circulations over Southeastern China

2019 ◽  
Vol 32 (11) ◽  
pp. 3069-3087 ◽  
Author(s):  
Jiandong Li ◽  
Wei-Chyung Wang ◽  
Jiangyu Mao ◽  
Ziqian Wang ◽  
Gang Zeng ◽  
...  
Keyword(s):  
Water Vapor ◽  
Tibetan Plateau ◽  
South China Sea ◽  
South China ◽  
Water Vapor Transport ◽  
Radiation Balance ◽  
Radiative Effect ◽  
Southeastern China ◽  
China Sea ◽  
Cloud Radiative Effect

Abstract Clouds strongly modulate regional radiation balance and their evolution is profoundly influenced by circulations. This study uses 2001–16 satellite and reanalysis data together with regional model simulations to investigate the spring shortwave cloud radiative effect (SWCRE) and the associated circulations over southeastern China (SEC). Strong SWCRE, up to −110 W m−2, persists throughout springtime in this region and its spring mean is the largest among the same latitudes of the Northern Hemisphere. SWCRE exhibits pronounced subseasonal variation and is closely associated with persistent regional ascending motion and moisture convergence, which favor large amounts of cloud liquid water and resultant strong SWCRE. Around pentad 12 (late February), SWCRE abruptly increases and afterward remains stable between 22° and 32°N. The thermal and dynamic effects of Tibetan Plateau and westerly jet provide appropriate settings for the maintenance of ascending motion, while water vapor, as cloud water supply, stably comes from the southern flank of the Tibetan Plateau and South China Sea. During pentads 25–36 (early May to late June), SWCRE is further enhanced by the increased water vapor transport caused by the march of East Asian monsoon systems, particularly after the onset of the South China Sea monsoon. After pentad 36, these circulations quickly weaken and the SWCRE decreases accordingly. Individual years with spring strong and weak rainfall are chosen to highlight the importance of the strength of the ascending motion. The simulation broadly reproduced the observed results, although biases exist. Finally, the model biases in SWCRE–circulation associations are discussed.

scholarly journals The Changing Influences of ENSO and the Pacific Meridional Mode on Mesoscale Eddies in the South China Sea

2019 ◽  
Vol 32 (3) ◽  
pp. 685-700 ◽  
Author(s):  
Pengfei Tuo ◽  
Jin-Yi Yu ◽  
Jianyu Hu
Keyword(s):  
South China Sea ◽  
Wind Stress ◽  
South China ◽  
Southern Oscillation ◽  
The South China Sea ◽  
Eddy Correlation ◽  
The South ◽  
Vector Method ◽  
China Sea ◽  
The Pacific

This study finds that the correlation between El Niño–Southern Oscillation (ENSO) and the activity of mesoscale oceanic eddies in the South China Sea (SCS) changed around 2004. The mesoscale eddy number determined from satellite altimetry observations using a geometry of the velocity vector method was significantly and negatively correlated with the Niño-3.4 index before 2004, but the correlation weakened and became insignificant afterward. Further analyses reveal that the ENSO–eddy relation is controlled by two major wind stress forcing mechanisms: one directly related to ENSO and the other indirectly related to ENSO through its subtropical precursor—the Pacific meridional modes (PMMs). Both mechanisms induce wind stress curl variations over the SCS that link ENSO to SCS eddy activities. While the direct ENSO mechanism always induces a negative ENSO–eddy correlation through the Walker circulation, the indirect mechanism is dominated by the northern PMM (nPMM), resulting in a negative ENSO–eddy correlation before 2004, and by the southern PMM (sPMM) after 2004, resulting in a positive ENSO–eddy correlation. As a result, the direct and indirect mechanisms enhance each other to produce a significant ENSO–eddy relation before 2004, but they cancel each other out, resulting in a weak ENSO–eddy relation afterward. The relative strengths of the northern and southern PMMs are the key to determining the ENSO–eddy relation and may be related to a phase change of the interdecadal Pacific oscillation.

scholarly journals Multidecadal Changes of Upper-Ocean Thermal Conditions in the Tropical Northwest Pacific Ocean versus South China Sea during 1960–2015

2018 ◽  
Vol 31 (10) ◽  
pp. 3999-4016 ◽  
Author(s):  
Tzu-Ling Chiang ◽  
Yi-Chia Hsin ◽  
Chau-Ron Wu
Keyword(s):  
Pacific Ocean ◽  
South China Sea ◽  
South China ◽  
Thermal Conditions ◽  
North Equatorial Current ◽  
Upper Ocean ◽  
Northwest Pacific ◽  
Northwest Pacific Ocean ◽  
China Sea ◽  
Basin Scale

Abstract By analyzing the upper-ocean properties of observation-based hydrographic data and validated oceanic reanalysis products, this study presents multidecadal changes of oceanic surface and subsurface thermal conditions in the tropical northwest Pacific Ocean (TNWP) and South China Sea (SCS) during 1960–2015. The analysis reveals that a transition of a 30-yr trend took place in 1980s during the analyzed period for both the surface and subsurface environment. Generally, the warming trend of sea surface temperature (SST) in the TNWP has a similar multidecadal change to that in the SCS. However, a huge accumulating rate of upper-ocean heat content above the 26°C isotherm (UOHC26) showed up in the TNWP (about 3 times compared to that in the SCS) in the last 30 years. In the TNWP, the southward shift of the North Equatorial Current on the multidecadal time scale induces the vertical displacement of isotherms, leading to a strong subsurface warming around the top of the thermocline. Secondarily, the Pacific decadal oscillation (PDO)-related SST regulates the thermal structure in the mixed layer. The multidecadal UOHC26 in the SCS is mainly attributed to the PDO-related SST and further modulated by the isothermal variability caused by the change of basin-scale SCS circulation.

scholarly journals Tropical Cyclone–Induced Ocean Response: A Comparative Study of the South China Sea and Tropical Northwest Pacific*,+

2015 ◽  
Vol 28 (15) ◽  
pp. 5952-5968 ◽  
Author(s):  
Wei Mei ◽  
Chun-Chi Lien ◽  
I.-I. Lin ◽  
Shang-Ping Xie
Keyword(s):  
South China Sea ◽  
Mixed Layer ◽  
South China ◽  
Regional Difference ◽  
Chlorophyll Concentration ◽  
The South China Sea ◽  
Northwest Pacific ◽  
The South ◽  
China Sea ◽  
Sst Cooling

Abstract The thermocline shoals in the South China Sea (SCS) relative to the tropical northwest Pacific Ocean (NWP), as required by geostrophic balance with the Kuroshio. The present study examines the effect of this difference in ocean state on the response of sea surface temperature (SST) and chlorophyll concentration to tropical cyclones (TCs), using both satellite-derived measurements and three-dimensional numerical simulations. In both regions, TC-produced SST cooling strongly depends on TC characteristics (including intensity as measured by the maximum surface wind speed, translation speed, and size). When subject to identical TC forcing, the SST cooling in the SCS is more than 1.5 times that in the NWP, which may partially explain weaker TC intensity on average observed in the SCS. Both a shallower mixed layer and stronger subsurface thermal stratification in the SCS contribute to this regional difference in SST cooling. The mixed layer effect dominates when TCs are weak, fast-moving, and/or small; and for strong and slow-moving TCs or strong and large TCs, both factors are equally important. In both regions, TCs tend to elevate surface chlorophyll concentration. For identical TC forcing, the surface chlorophyll increase in the SCS is around 10 times that in the NWP, a difference much stronger than that in SST cooling. This large regional difference in the surface chlorophyll response is at least partially due to a shallower nutricline and stronger vertical nutrient gradient in the SCS. The effect of regional difference in upper-ocean density stratification on the surface nutrient response is negligible. The total annual primary production increase associated with the TC passage estimated using the vertically generalized production model in the SCS is nearly 3 times that in the NWP (i.e., 6.4 ± 0.4 × 1012 versus 2.2 ± 0.2 × 1012 g C), despite the weaker TC activity in the SCS.

An overview of 10-year observation of the South China Sea branch of the Pacific to Indian Ocean throughflow at the Karimata Strait

2019 ◽  
Vol 38 (4) ◽  
pp. 1-11 ◽  
Author(s):  
Zexun Wei ◽  
Shujiang Li ◽  
R. Dwi Susanto ◽  
Yonggang Wang ◽  
Bin Fan ◽  
...  
Keyword(s):  
Indian Ocean ◽  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
The Pacific ◽  
Karimata Strait
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