Interannual Variability of Springtime Extreme Heat Events over the Southeastern Edge of the Tibetan Plateau: Role of A Spring-type Circum-global Teleconnection Pattern

2021 ◽  
pp. 1-47
Author(s):  
Tuantuan Zhang ◽  
Xingwen Jiang ◽  
Junwen Chen ◽  
Song Yang ◽  
Yi Deng ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Interannual Variability ◽  
Extreme Heat ◽  
Boreal Summer ◽  
The Tibetan Plateau ◽  
Mean Flow ◽  
The North ◽  
Extreme Heat Events ◽  
Spring Type ◽  
Heat Events

AbstractDue to the high mountains to the west and north of the plateau, and the control by westerly mean flow in spring, hot and dry conditions are often observed over the southeastern edge of the Tibetan Plateau (SETP), and hence favoring occurrences of extreme heat events there. Indeed, maximum centers and remarkable increasing trends of extreme heat (EH) days in spring are found over the region. Springtime EH events over the SETP also exhibit strong interannual variability and are closely linked to a spring-type circum-global teleconnection (SCGT) pattern, which is the second leading mode of 200-hPa meridional wind over the North Hemisphere in spring. This SCGT shows distinctive features from the traditional circum-global teleconnection patterns found in boreal summer and winter. It is revealed by a circum-globally navigated Rossby wave train along the mid-high latitudes, which splits to a north branch along the polar jet and a south branch along the subtropical jet over Eurasia after propagating through the North Atlantic. The two branches eventually reach the SETP, forming an anomalous anticyclonic circulation over the region. Hence, conditions in the SETP are controlled by significant anomalous subsidence and a clearer sky, resulting in below-normal rainfall and above-normal air temperature, in favor of more EH events in the region. The SETP EH events are also closely linked to the spring-type CGT-like pattern in April and May, but not in March. In addition, the influence of the foehn effect on the SETP EH is discussed.

scholarly journals Human and natural drivers of the recent contrasting trends between daytime and nighttime hot extremes

2021 ◽  
Author(s):  
Sang-Wook Yeh ◽  
Eun-Hye Lee ◽  
Seung-Ki Min
Keyword(s):  
Climate Models ◽  
Heat Waves ◽  
Low Frequency ◽  
Extreme Heat ◽  
Boreal Summer ◽  
Human Society ◽  
Sudden Increase ◽  
Tropical Night ◽  
Extreme Heat Events ◽  
Heat Events

Abstract The frequency and duration of extreme heat events, including heat waves (HWs, daytime hot extremes) and tropical night (TNs), are increasing significantly as the climate warms, adversely affecting human health, agriculture, and energy consumption. Although many detection and attribution studies have examined extreme heat events, the underlying mechanisms associated with the recent increase in HWs and TNs remain unclear. In this study, we analyze the controlling factors behind the distinct increases in HW and TN events over the Northern Hemisphere during boreal summer (June to August). We found that the occurrence of HW events has been increasing gradually since 1980, mostly due to anthropogenic forcing. However, the occurrence of TN events increased abruptly during the late 1990s and has changed little since then. We demonstrate that this sudden increase in TN events is closely associated with low frequency variability in sea surface temperature, including the Pacific Decadal Oscillation, indicating its natural origin. We further found that CMIP5 climate models fail to capture the observed non-linear increases in TN events, implying potentially large uncertainty in future projections of nighttime heat events and its impacts on human society and ecosystem.

scholarly journals Interannual Variability of the North Pacific Mixed Layer Associated with the Spring Tibetan Plateau Thermal Forcing

2019 ◽  
Vol 32 (11) ◽  
pp. 3109-3130 ◽  
Author(s):  
Ruizao Sun ◽  
Anmin Duan ◽  
Lilan Chen ◽  
Yanjie Li ◽  
Zhiang Xie ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Interannual Variability ◽  
Mixed Layer ◽  
North Pacific ◽  
General Circulation ◽  
Sea Surface ◽  
The Tibetan Plateau ◽  
The North ◽  
Anomalous Anticyclone ◽  
The North Pacific

Abstract By using multisourced data and two sets of sensitivity runs from the coupled general circulation model CESM1.2.0, we investigated the effects of the spring [March, April, and May (MAM)] surface sensible heating over the Tibetan Plateau (SHTP) on the interannual variability of the North Pacific Ocean sea surface temperature (SST) and mixed layer. The results indicated that an above-normal MAM SHTP can generate a Rossby wave downstream and form an anomalous equivalent barotropic anticyclone over the North Pacific, inducing anticyclonic wind stress anomalies. As a result of Ekman transport and Ekman pumping, sea currents converge near 40°N, accompanied by weak downwelling motion. The mixed layer heat budget diagnosis indicates that the net heat fluxes, together with meridional advection anomalies, contributed significantly to changes in the mixed layer temperature (MLT). As a result, the SST anomalies (SSTAs) and MLT anomalies both present a horseshoelike pattern. In addition, the significant warm SSTAs show a maximum in the late spring, but the significant warm MLT anomalies centered under the sea surface (25-m depth) could be sustained until summer, acting like a signal storage for the anomalous spring SHTP. Moreover, the midlatitude ocean–atmosphere interaction provides a positive feedback on the development of the anomalous anticyclone over the North Pacific, since the SSTA pattern could strengthen the oceanic front and induce more active transient eddy activities. The eddy vorticity forcing that is dominant among the total atmospheric forcings tends to produce an equivalent barotropic atmospheric high pressure, which in turn intensifies the initial anomalous anticyclone.

scholarly journals Moisture Sources for East Asian Precipitation: Mean Seasonal Cycle and Interannual Variability

2019 ◽  
Vol 20 (4) ◽  
pp. 657-672 ◽  
Author(s):  
Liang Guo ◽  
Ruud J. van der Ent ◽  
Nicholas P. Klingaman ◽  
Marie-Estelle Demory ◽  
Pier Luigi Vidale ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Interannual Variability ◽  
Seasonal Cycle ◽  
East Asian ◽  
The Black Sea ◽  
The Tibetan Plateau ◽  
The Caspian Sea ◽  
Moisture Sources ◽  
The North ◽  
Thaw Cycle

ABSTRACT This study investigates the moisture sources that supply East Asian (EA) precipitation and their interannual variability. Moisture sources are tracked using the Water Accounting Model-2layers (WAM-2layers), based on the Eulerian framework. WAM-2layers is applied to five subregions over EA, driven by the ERA-Interim reanalysis from 1979 to 2015. Due to differences in regional atmospheric circulation and in hydrological and topographic features, the mean moisture sources vary among EA subregions. The tropical oceanic source dominates southeastern EA, while the extratropical continental source dominates other EA subregions. The moisture sources experience large seasonal variations, due to the seasonal cycle of the EA monsoon, the freeze–thaw cycle of the Eurasian continent, and local moisture recycling over the Tibetan Plateau. The interannual variability of moisture sources is linked to interannual modes of the coupled ocean–atmosphere system. The negative phase of the North Atlantic Oscillation increases moisture transport to northwestern EA in winter by driving a southward shift in the midlatitude westerly jet over the Mediterranean Sea, the Black Sea, and the Caspian Sea. Atmospheric moisture lifetime is also reduced due to the enhanced westerlies. In summers following El Niños, an anticyclonic anomaly over the western North Pacific increases moisture supplied from the South China Sea to the southeastern EA and shortens the traveling distance. A stronger Somali Jet in summer increases moisture to the Tibetan Plateau and therefore increases precipitation over the eastern Tibetan Plateau. The methods and findings in this study can be used to evaluate hydrological features in climate simulations.

scholarly journals Lake-Related Cloud Dynamics on the Tibetan Plateau: Spatial Patterns and Interannual Variability

2015 ◽  
Vol 28 (23) ◽  
pp. 9080-9104 ◽  
Author(s):  
F. Rüthrich ◽  
C. Reudenbach ◽  
B. Thies ◽  
J. Bendix
Keyword(s):  
Tibetan Plateau ◽  
Interannual Variability ◽  
The Arctic ◽  
Boreal Summer ◽  
Land Breeze ◽  
Monsoon Circulation ◽  
The Tibetan Plateau ◽  
Convective Activity ◽  
Lake Effect ◽  
Cloud Dynamics

Abstract The scarcity of meteorological observations has hitherto prevented spatially comprehensive and complete assessments on regional and local-scale atmospheric processes such as breeze systems on the Tibetan Plateau (TiP). Because of the high abundance of lakes, the steep topography, and the intense insolation of the TiP, lake breeze and land breeze systems might, however, contribute substantially to the local climatic and hydrological variability. The presented study aims at unveiling the influence of the lake effect over the whole TiP by using a novel high-mountain satellite cloud product, based on Meteosat Indian Ocean Data Coverage (IODC) data from 1999 to 2012, focusing on 70 lake systems larger than 72 km2. Of particular interest are the spatial and interannual variability of lake-related cloud dynamics during boreal summer and autumn. For both seasons, a significant effect of lakes on cloudiness is shown during the early morning. Its mean strength is mainly determined by each basin’s temperature difference between lake and surroundings. For boreal summer the large-scale influences of tropical and extratropical circulation pattern on the interannual variability of the lake effect are also investigated. The results show that the Arctic and North Atlantic Oscillations (AO and NAO) inhibit convective activity above lakes in the northern and central-eastern domain. A positive polarity of the Southern Oscillation index (SOI), in contrast, is in phase with enhanced convective activity. The variability of the Indian summer monsoon circulation does not affect cloud dynamics at more than two locations. Case studies are employed to illustrate interactions between cloud activity and the SOI and NAO. For this purpose satellite data are combined with the modeled 10 km × 10 km High Asia Refined Analysis dataset on a daily basis.

Size distribution of PM20 observed to the north of the Tibetan Plateau

2021 ◽  
Vol 18 (2) ◽  
pp. 367-376
Author(s):  
Cheng-long Zhou ◽  
Fan Yang ◽  
Wen Huo ◽  
Ali Mamtimin ◽  
Xing-hua Yang
Keyword(s):  
Tibetan Plateau ◽  
Size Distribution ◽  
The Tibetan Plateau ◽  
The North

Possible Effect of the Thermal Condition of the Tibetan Plateau on the Interannual Variability of the Summer Asian–Pacific Oscillation

2017 ◽  
Vol 30 (24) ◽  
pp. 9965-9977 ◽  
Author(s):  
Ge Liu ◽  
Ping Zhao ◽  
Junming Chen
Keyword(s):  
Twentieth Century ◽  
Tibetan Plateau ◽  
Interannual Variability ◽  
North Pacific ◽  
Thermal Condition ◽  
The Tibetan Plateau ◽  
Tropospheric Temperature ◽  
Upward Motion ◽  
Central Eastern ◽  
Asian Pacific

The summer (June–August) Asian–Pacific Oscillation (APO), a large-scale atmospheric teleconnection pattern, is closely associated with climate anomalies over the Northern Hemisphere. Using the NOAA/CIRES twentieth-century reanalysis, the ECMWF twentieth-century atmospheric reanalysis, and the NCEP reanalysis, this study investigates the variability of the summer APO on the interannual time scale and its relationship with the thermal condition over the Tibetan Plateau (TP). The results show that the interannual variability of the APO is steadily related to the summer TP surface air temperature during the last 100 years. Observation and simulation further show that a positive heating anomaly over the TP can increase the upper-tropospheric temperature and upward motion over Asia. This anomalous upward flow moves northward in the upper troposphere, and then turns and moves eastward, before finally descending over the mid- to high latitudes of the central-eastern North Pacific, concurrently accompanied by anomalous upward motion over the lower latitudes of the central-eastern North Pacific. The anomalous downward and upward motions over the central-eastern North Pacific reduce the in situ mid- and upper-tropospheric temperature, mainly through modulating condensation latent heat from precipitation and/or dry adiabatic heat, which ultimately leads to the interannual variability of the summer APO. In this process, the zonal vertical circulation over the extratropical Asian–North Pacific sector plays an important bridging role.

Sign in / Sign up

Export Citation Format

Share Document