A Record of Holocene Climate Change from Lake Geochemical Analyses in Southeastern Arabia

2006 ◽  
Vol 66 (3) ◽  
pp. 465-476 ◽  
Author(s):  
Adrian G. Parker ◽  
Andrew S. Goudie ◽  
Stephen Stokes ◽  
Kevin White ◽  
Martin J. Hodson ◽  
...  
Keyword(s):  
North Atlantic ◽  
Lake Level ◽  
Lacustrine Sediments ◽  
Summer Rainfall ◽  
Late Glacial ◽  
Human Occupation ◽  
The North ◽  
Holocene Climate Change ◽  
The North Atlantic ◽  
Geochemical Analyses

AbstractLacustrine sediments from southeastern Arabia reveal variations in lake level corresponding to changes in the strength and duration of Indian Ocean Monsoon (IOM) summer rainfall and winter cyclonic rainfall. The late glacial/Holocene transition of the region was characterised by the development of mega-linear dunes. These dunes became stabilised and vegetated during the early Holocene and interdunal lakes formed in response to the incursion of the IOM at approximately 8500 cal yr BP with the development of C3 dominated savanna grasslands. The IOM weakened ca. 6000 cal yr BP with the onset of regional aridity, aeolian sedimentation and dune reactivation and accretion. Despite this reduction in precipitation, the lake was maintained by winter dominated rainfall. There was a shift to drier adapted C4 grasslands across the dune field. Lake sediment geochemical analyses record precipitation minima at 8200, 5000 and 4200 cal yr BP that coincide with Bond events in the North Atlantic. A number of these events correspond with changes in cultural periods, suggesting that climate was a key mechanism affecting human occupation and exploitation of this region.

Analysis of the Dominant Spatial Patterns of Summer Precipitation and Circulation Characteristics in Northwest China

2020 ◽  
Author(s):  
liwei liu ◽  
guoyang lu ◽  
dong wei ◽  
danhua li ◽  
xing wang ◽  
...  
Keyword(s):  
North Atlantic ◽  
Summer Precipitation ◽  
Summer Rainfall ◽  
Northwest China ◽  
Diagnostic Methods ◽  
Height Field ◽  
Main Mode ◽  
The North ◽  
Circulation Characteristic ◽  
The North Atlantic

<p>In recent years, the summer rainfall shows an increasing trend in Northwest China. Based on the NCEP/NCAR reanalysis data, the RESST data from NOAA and the precipitation data from 351 meteorological observation stations in Northwest China from 1981-2018, the dominant modes of summer precipitation anomalies, the corresponded circulation characteristic and the main influence systems were analyzed by diagnostic methods. There were three dominant EOF modes about summer rainfall, the first one showed the same anomaly in whole region, the second showed a inverse pattern between the east and west, and the third showed the opposite anomaly between the south and north. The variance contribution of the first mode accounted for 20% and the first mode was represented as the primary mode in the subsequent analysis. The high impact region of circulation which affected the precipitation in Northwest China was the middle and high latitudes area of Eurasia and the subtropical area: for the first mode’s positive phase, the 500hPa height field showed a "+ - +" distribution in the middle latitude of Eurasia, while on the 200hPa wind field, there was an anticyclone near the Ural and a cyclone near Lake Baikal, it also has an anticyclone on the Chinese mainland, this configuration will facilitates the strengthening of westerly jets. The tropical Pacific and the North Atlantic are the main external forcing signals of the circulation pattern: SST characteristics showed that the negative phase of the North Atlantic SST Tripole in spring, from winter of the previous year to summer of the current year, SST of the equatorial Middle East Pacific developed from warm to cold. The distribution of 500 hPa height field corresponding to the main mode of summer precipitation in Northwest China is similar to that of EU remote correlation type. An index(I<sub>Hgt</sub>) was defined to reflect circulation patterns in mid-latitude and subtropical regions, when the index is positive/negative, most of the precipitation in northwest China is more/less. After 2000, the correlation between the two increased significantly. Given the performance of the I<sub>Hgt</sub> index in describing the summer precipitation, it could be used as a good indicator in the monitoring and prediction of the summer precipitation in Northwest China.</p>

Summer Rainfall Seesaw between Hetao and the Middle and Lower Reaches of the Yangtze River and Its Relationship with the North Atlantic Oscillation

2017 ◽  
Vol 30 (17) ◽  
pp. 6629-6643 ◽  
Author(s):  
Dachao Jin ◽  
Zhaoyong Guan
Keyword(s):  
Rossby Wave ◽  
North Atlantic ◽  
Yangtze River ◽  
Lower Troposphere ◽  
Summer Rainfall ◽  
Northern China ◽  
Upper Troposphere ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Using the NCEP–NCAR reanalysis and other observational datasets, the authors have investigated the relationship of summer rainfall variations between the Hetao region of northern China and the middle and lower reaches of Yangtze River (MLRYR). The results have demonstrated that rainfall in Hetao varies out of phase with that in MLRYR on the interannual time scales. This phenomenon is referred to as the Hetao–Yangtze rainfall seesaw (HYRS). An HYRS index is defined to reveal both spatial and temporal features of HYRS. It is found that the North Atlantic Oscillation (NAO) affects the HYRS. In years when the NAO is in its positive phase, anomalous divergences in the lower troposphere and anomalous convergences in the upper troposphere are observed in regions of the Mediterranean and eastern Europe. The anomalous convergences in the upper troposphere occur as the positive Rossby wave source excites a circumglobal teleconnection (CGT) in the midlatitudes, exhibiting the eastward propagation of Rossby wave energy along the Asian jet. Meanwhile, the Eurasian–Pacific (EUP) teleconnection also affects the HYRS. Influenced mainly by the CGT pattern, the circulations over Hetao and MLRYR are consequently perturbed. The atmosphere over Hetao converges anomalously in the lower troposphere and diverges anomalously in the upper troposphere, facilitating more than normal rainfall there. At the same time, the atmosphere over MLRYR diverges anomalously in the lower troposphere and converges anomalously in the upper troposphere, resulting in more than normal summer rainfall in MLRYR. In this way, the north–south rainfall seesaw is formed. This NAO-induced rainfall seesaw is potentially useful for summer rainfall predictions in both MLRYR and the Hetao region of northern China.

Reply to “Comments on ‘Changes to the North Atlantic Subtropical High and Its Role in the Intensification of Summer Rainfall Variability in the Southeastern United States’”

2013 ◽  
Vol 26 (2) ◽  
pp. 683-688 ◽  
Author(s):  
Wenhong Li ◽  
Laifang Li ◽  
Rong Fu ◽  
Yi Deng ◽  
Hui Wang
Keyword(s):  
North Atlantic ◽  
Rainfall Variability ◽  
Southeastern United States ◽  
Summer Rainfall ◽  
Subtropical High ◽  
North Atlantic Subtropical High ◽  
The North ◽  
Westward Movement ◽  
The North Atlantic ◽  
Potential Impact

Abstract Recently Diem questioned the western ridge movement of the North Atlantic subtropical high (NASH) reported in a 2011 paper of Li et al. This reply shows more analysis that further strengthens the conclusions originally put forth by Li et al. Diem’’s analysis of the trend in the western ridge of the NASH was based on the data over a 30-yr period (1978–2007), whereas the main conclusions in Li et al. were drawn according to the data over a 60-yr period (1948–2007). Over the last 60 years, the NASH has shown a significant trend of westward movement, the meridional movement of the western ridge of the NASH has enhanced in the recent three decades, and the potential impact of global warming cannot be ruled out in an attempt to explain these changes of the NASH.

scholarly journals Asymmetric Relationship Between Mid-latitude Eurasian Circulation and Summer Rainfall in Hong Kong in Different Phases of ENSO

2021 ◽  
Vol 9 ◽  
Author(s):  
Yana Li ◽  
Ho-Nam Cheung ◽  
Wen Zhou
Keyword(s):  
South China ◽  
North Atlantic ◽  
Summer Rainfall ◽  
The South ◽  
The Urals ◽  
The North ◽  
Westerly Jet ◽  
The North Atlantic ◽  
South China Coast ◽  
China Coast

During the period 1979–2019, the interannual variation of summer rainfall in Hong Kong (HK), located on the South China coast, is weakly correlated with tropical forcing, including the El Niño/Southern Oscillation (ENSO). Instead, HK summer rainfall is strongly correlated with the mid-latitude circulation over the Urals and the preceding spring sea surface temperature (SST) over the North Atlantic (SST-Atl). The above relationship is stronger in negative ENSO summers, where the SST-Atl anomaly tends to persist from spring to summer. The persistence of the warm SST-Atl anomaly is associated with a Rossby wave train propagating from the North Atlantic to East Asia, with a low over the Urals and a high over the high latitudes of Asia. Correspondingly, the upper-tropospheric westerly jet in East Asia becomes stronger and shifts southward toward South China. The enhanced westerly wind over South China is accompanied by an anomalous Philippine Sea anticyclone, which transports more water vapor to the South China coast and causes more rainfall in HK. On the other hand, during positive ENSO summers, HK summer rainfall is affected by variation in the subtropical westerly jet over South China, which is related to water vapor transport from the Indian Ocean and Bay of Bengal. This is also associated with a height anomaly over northeastern China and the spring sub-polar North Atlantic SST. Therefore, it is important to investigate the impact of mid-latitude forcing on summer rainfall on the South China coast.

scholarly journals Comments on “Changes to the North Atlantic Subtropical High and Its Role in the Intensification of Summer Rainfall Variability in the Southeastern United States”

2013 ◽  
Vol 26 (2) ◽  
pp. 679-682 ◽  
Author(s):  
Jeremy E. Diem
Keyword(s):  
United States ◽  
Global Warming ◽  
North Atlantic ◽  
Rainfall Variability ◽  
Southeastern United States ◽  
Summer Rainfall ◽  
Subtropical High ◽  
North Atlantic Subtropical High ◽  
The North ◽  
The North Atlantic

Abstract In a recent article, Li et al. examined changes in the summer-season location of the western ridge of the North Atlantic subtropical high from 1948 to 2007 because there has been an increase in interannual summer rainfall variability in the southeastern United States. The following major conclusions by Li et al. are incorrect: the western ridge has undergone a significant westward trend since the late 1970s; the western ridge had increased meridional movement during 1978–2007 compared to 1948–1977; and global warming appears to be contributing to the westward expansion of the western ridge. Results presented in this paper reveal that the western ridge has been moving eastward over the past three decades, there was no change in latitudinal variance, and a westward movement of the western ridge should not be linked to global warming.

Synchronization of late-glacial vegetation changes at Crystal Lake, Illinois, USA with the North Atlantic Event Stratigraphy

2009 ◽  
Vol 72 (2) ◽  
pp. 234-245 ◽  
Author(s):  
Leila M. Gonzales ◽  
Eric C. Grimm
Keyword(s):  
North Atlantic ◽  
Late Quaternary ◽  
Ice Core ◽  
Late Glacial ◽  
Vegetation Changes ◽  
Pollen Record ◽  
Climate Conditions ◽  
The North ◽  
Event Stratigraphy ◽  
The North Atlantic

AbstractLate-glacial (17–11 cal ka BP) pollen records from midwestern North America show similar vegetation trends; however, poor dating resolution, wide-interval pollen counts, and variable sedimentation rates have prevented the direct correlation with the North Atlantic Event Stratigraphy as represented in the Greenland ice-core records, thus preventing the understanding of the teleconnections and mechanisms of late-Quaternary events in the Northern Hemisphere. The widespread occurrence of late-glacial vegetation and climates with no modern analogs also hinders late-glacial climate reconstructions. A high-resolution pollen record with a well-controlled age model from Crystal Lake in northeastern Illinois reveals vegetation and climate conditions during the late-glacial and early Holocene intervals. Late-glacial Crystal Lake pollen assemblages, dominated by Picea mariana and Fraxinus nigra with lesser amounts of Abies and Larix, suggest relatively wet climate despite fluctuations between colder and warmer temperatures. Vegetation changes at Crystal Lake are coeval with millennial-scale trends in the NGRIP ice-core record, but major shifts in vegetation at Crystal Lake lag the NGRIP record by 300–400 yr. This lag may be due to the proximity of the Laurentide ice sheet, the ice sheet's inherent slowness in response to rapid climate changes, and its effect on frontal boundary conditions and lake-effect temperatures.

Sign in / Sign up

Export Citation Format

Share Document