Distinct Interdecadal Change Contrasts between Summer and Autumn in Latitude‐Longitude Covariability of Northwest Pacific Typhoon Genesis Locations

Abstract The correlation of northwest (NW) Pacific climate anomalies during summer with El Niño–Southern Oscillation (ENSO) in the preceding winter strengthens in the mid-1970s and remains high. This study investigates the hypothesis that the tropical Indian Ocean (TIO) response to ENSO is key to this interdecadal change, using a 21-member ensemble simulation with the Community Atmosphere Model, version 3 (CAM3) forced by the observed history of sea surface temperature (SST) for 1950–2000. In the model hindcast, the TIO influence on the summer NW Pacific strengthens in the mid-1970s, and the strengthened TIO teleconnection coincides with an intensification of summer SST variability over the TIO. This result is corroborated by the fact the model’s skills in simulating NW Pacific climate anomalies during summer increase after the 1970s shift. During late spring to early summer, El Niño–induced TIO warming decays rapidly for the epoch prior to the 1970s shift but grows and persists through summer for the epoch occurring after it. This difference in the evolution of the TIO warming determines the strength of the TIO teleconnection to the NW Pacific in the subsequent summer. An antisymmetric wind pattern develops in spring across the equator over the TIO, and the associated northeasterly anomalies aid the summer warming over the north Indian Ocean by opposing the prevailing southwest monsoon. In the model, this antisymmetric spring wind pattern is well developed after but absent before the 1970s shift.

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Decadal Variation of the Precipitation Relationship Between June and August over South China and Its Mechanism

10.21203/rs.3.rs-720627/v1 ◽

2021 ◽

Author(s):

shuai li ◽

Zhiqiang Gong ◽

Shixuan zhang ◽

Jie Yang ◽

Shaobo Qiao ◽

...

Keyword(s):

South China ◽

Late Summer ◽

Summer Rainfall ◽

Feedback Mechanism ◽

Interdecadal Change ◽

Northwest Pacific ◽

Decadal Variation ◽

Central Pacific ◽

Anomaly Pattern ◽

Dipole Pattern

Abstract This paper investigates the characteristics and causes for the interdecadal change in the relationships between early and late summer rainfall over South China (SC). This study finds that the correlations of the precipitation over SC between June and August shift from weakly positive in 1979 – 1995 to obviously negative in 1996-2019. Further analysis demonstrates that the interdecadal variations of monthly SST anomaly (SSTA) and associated air-sea interactions in June and August account for the decadal variations of the precipitation relationships. During the prior period 1979-1995, the tropical West Indian Ocean (WIO) shows a significant positive SSTA in June, which triggers Kevin waves and an anticyclone circulation over the tropical Northwest Pacific (NWP). The warm and wet air transported by the southwest airflow at the north of the anticyclone provides favorable environmental condition to produce more precipitation over SC region in June. In contrast, the SST dipole pattern with the negative SSTAs in the maritime continent (MC) and positive SSTAs in the tropical Central Pacific (CP) is dominant in August. The SST dipole pattern is inconducive to the formation of anticyclone over SC, causing a weak positive precipitation correlation between June and August. During the latter period 1996-2019, the precipitation over SC in June is the same as that in the prior period as there is no significant decadal change in tropical WIO SST and East Asian circulation. However, an opposite phase of the SST dipole anomaly pattern in MC and the tropical CP is dominant in August during the latter period. Accordingly, the positive feedback mechanism of air-sea interaction leads to the enhancement of local convection activities in MC and the meridional Hadley circulations and the NWP subtropical high, leading to a decrease of precipitation over SC in August. Overall, the decadal variation of the SST dipole anomaly pattern in MC and the tropical CP is the key factor affecting the adjustment of the correlations between June and August precipitation in the two periods.

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Archibald Menzies (1754–1842), an early botanist on the northwestern seaboard of North America, 1792–1794, with further notes on his life and work

Archives of Natural History ◽

10.3366/anh.2001.28.1.71 ◽

2001 ◽

Vol 28 (1) ◽

pp. 71-122 ◽

Cited By ~ 8

Author(s):

ERIC W. GROVES

Keyword(s):

North America ◽

Pacific Coast ◽

Later Life ◽

Northwest Pacific ◽

Historical Events ◽

Short Biography

ABSTRACT: This paper includes a short biography of Menzies and an outline of the historical events on the northwest Pacific coast leading up to Vancouver's voyage. A table listing the botanical visitors to that area prior to 1792 is given followed by a résumé of the evolution of Menzies's journal. Sources used in compiling the chronology of his movements during Vancouver's voyage are then set down, ending the section with an account of Menzies's own visit, 1792–1794. His method of plant collecting is discussed along with an account of his collections and their subsequent disposal. The paper concludes with details of Menzies's later life, his connection with other botanists of the day, and an assessment of his achievements.

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