Impacts of urban expansion on the diurnal variations of summer monsoon precipitation over the south China coast

Abstract The intensity change of past (1976–2005) tropical cyclones that made landfall along the south China coast (110.5°–117.5°E) is examined in this study using the best-track data from the Hong Kong Observatory. The change in the central pressure deficit (environmental pressure minus central pressure) and maximum surface wind after landfall are found to fit fairly well with an exponential decay model. Of the various potential predictors, the landfall intensity, landward speed, and excess of 850-hPa moist static energy have significant influence on the decay rates. Prediction equations for the exponential decay constants are developed based on these predictors.

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Changing Relationship Between Tibetan Plateau Temperature and South China Sea Summer Monsoon Precipitation

Frontiers in Environmental Science ◽

10.3389/fenvs.2020.583466 ◽

2020 ◽

Vol 8 ◽

Author(s):

Mei Liang ◽

Jianjun Xu ◽

Johnny C. L. Chan ◽

Liguang Wu ◽

Xiangde Xu

Keyword(s):

Tibetan Plateau ◽

South China Sea ◽

Summer Monsoon ◽

South China ◽

Negative Correlation ◽

The South China Sea ◽

Monsoon Precipitation ◽

The South ◽

China Sea ◽

The Relationship

The present study documents the changes in the relationship between the Tibetan Plateau summer surface temperature (TPST) and the South China Sea summer monsoon precipitation (SCSSMP). A stepwise regression model is used to exclude the signals of global warming, El Niño–Southern Oscillation (ENSO), western North Pacific Subtropical High (WNPSH), Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO). The results indicate that the relationship between TPST–SCSSMP changes with time, going from a negative correlation during the period of 1980–1994 to an obvious positive correlation during 1998–2016 in the South China Sea. Meanwhile, the negative correlation between TPST and the East Asia subtropical front (Meiyu) is enhanced during 1998–2016. This change in the TPST–SCSSMP relationship is associated with the change of the atmospheric circulation, which is mainly due to TPST interdecadal variation. A wave–like structure at the low latitude moves eastward along the low–level monsoon flow, and a strong cyclonic circulation is apparent in the southwestern part of the Plateau, including the Indochina Peninsula, South China Sea, and the ocean to the east of the Philippines, which is consistent with the negative correlation between TPST and Outgoing Longwave Radiation (OLR). The increase in water–vapor convergence and more favorable convection conditions lead to more precipitation in the region after the late 1990s. The present results suggest that, in a changing climate, we should be cautious when using predictor with interdecadal variations.

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The Crucial Role of Synoptic Pattern in Determining the Spatial Distribution and Diurnal Cycle of Heavy Rainfall over the South China Coast

Journal of Climate ◽

10.1175/jcli-d-20-0274.1 ◽

2020 ◽

pp. 1-47

Author(s):

Chenli Wang ◽

Kun Zhao ◽

Anning Huang ◽

Xingchao Chen ◽

Xiaona Rao

Keyword(s):

South China ◽

Heavy Rainfall ◽

Warm Season ◽

Early Morning ◽

The South ◽

Synoptic Patterns ◽

Low Level ◽

South China Coast ◽

China Coast

AbstractSouth China coast suffers frequent heavy rainfall every warm-season. Based on the objective classification method of principle components analysis, the key role of synoptic pattern in determining the heavy rainfall processes occurred over the South China coast in warm season during 2008-2018 is examined in this study. We found heavy rainfall occurs most frequently under three typical synoptic patterns (P1-P3 hereafter) characterized by strong low-level onshore winds. P1 and P3 are featured by a prevailing southwesterly monsoonal flow in the lower troposphere, with heavy rainfall frequently occurring over the inland windward region in the afternoon associated with the orographic lifting and solar heating. The onshore wind of P3 is stronger than P1 as the western Pacific subtropical high extends more westward to 122°E, which induces stronger low-level convergence along the coastline than P1 when the ageostrophic wind veers from offshore to onshore direction in the early morning. Hence, a secondary early morning rainfall peak can be found along the coastline. P2 is characterized by a low-level vortex located over the southwest of south China. Heavy rainfall under P2 usually initiate over the western part of the coastal region in the morning and then propagate towards inland in the afternoon. Overall, the synoptic patterns strongly determine the spatial distribution and diurnal cycle of heavy rainfall over the South China coast. It is closely related to the diurnally varying low-level onshore winds rather than the low-level jets, as well as the different interactions between the low-level onshore winds and the local orography, coastline and land-sea breeze circulations under different synoptic patterns.

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