scholarly journals Interannual Variability of Precipitation Recycle Ratio over the Tibetan Plateau

2020 ◽  
Author(s):  
Yin Zhao ◽  
Tianjun Zhou
Keyword(s):  
Tibetan Plateau ◽  
Interannual Variability ◽  
The Tibetan Plateau ◽  
Recycle Ratio

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.

scholarly journals East Asian Summer Monsoon Precipitation Response to Variations in Upstream Westerly Wind

2021 ◽  
Author(s):  
Jun-Hyeok Son ◽  
Kyong-Hwan Seo
Keyword(s):  
Wind Speed ◽  
Tibetan Plateau ◽  
Interannual Variability ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
The Tibetan Plateau ◽  
Westerly Wind ◽  
Dynamical Mechanism ◽  
Asian Summer

Abstract From spring to summer, the East Asian summer monsoon (EASM) rainband migrates northwestward. During summer, East Asian countries experience extensive precipitation due to the EASM rainband, but the springtime monsoon rainband lies over the Pacific. The seasonal evolution of the EASM rainband is influenced by the mechanical effect of the Tibetan Plateau, and seasonal changes in the westerly wind speeds impinging on the Tibetan Plateau are a key driver of this process. In this study, using interannual variability of the upstream zonal wind speed, the dynamical mechanism for the interannual variations of the EASM precipitation is revealed based on the topographically forced stationary Rossby wave theory. The dynamical mechanism regulating interannual variability in the EASM rainband is essentially the same mechanism that drives the seasonal evolution of the climatological EASM rainband. If the westerly winds impinging on the Tibetan Plateau are stronger (weaker) than average, then the EASM rainband shifts eastward (westward). Large variations in the upstream westerly wind during May induced considerable interannual variation in the zonal location of the rainband (up to a 20–30º shift). The westerly wind speed exhibited less variations in June and July, resulting in a smaller zonal shift of approximately 10º.

scholarly journals Modulation of springtime surface sensible heating over the Tibetan Plateau on the interannual variability of East Asian dust cycle

2020 ◽  
Vol 20 (18) ◽  
pp. 11143-11159
Author(s):  
Xiaoning Xie ◽  
Anmin Duan ◽  
Zhengguo Shi ◽  
Xinzhou Li ◽  
Hui Sun ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Heat Source ◽  
Interannual Variability ◽  
East Asian ◽  
Asian Dust ◽  
Dust Concentration ◽  
The Tibetan Plateau ◽  
Dust Source ◽  
Surface Dust ◽  
Surface Sensible Heating

Abstract. Previous observational evidence and numerical simulations have revealed that the surface sensible heating in spring (March–April–May, MAM) over the Tibetan Plateau (TPSH) can affect the Asian regional hydrological cycle, surface energy balance, and climate through altering atmospheric heat source of the Tibetan Plateau (TP). This study aims to investigate the impacts of MAM TPSH on the interannual variability of East Asian dust cycle by using CAM4-BAM (version 4 of the Community Atmosphere Model coupled to a bulk aerosol model), MERRA-2 (version 2 of the Modern-Era Retrospective analysis for Research and Applications) surface dust concentration, and TPSH measurements. Our simulations show that the surface dust concentrations over the East Asian (EA) dust source region and over the northwestern Pacific (NP) in MAM are significantly positively correlated with TPSH, with regionally averaged correlation coefficients of 0.49 for EA and 0.44 for NP. Similar positive correlations are also shown between the MAM TPSH measurements averaged over the 73 observation sites and the surface dust concentration from MERRA-2. Simulation-based comparisons between strongest and weakest TPSH years reveal that, the MAM surface dust concentration in the strongest TPSH years increases with relative differences of 13.1 % over EA and 36.9 % over NP. These corresponding differences are found in MERRA-2 with 22.9 % and 13.3 % over EA and NP, respectively. Further simulated results show that the processes of whole dust cycles (e.g., dust loading, emission, and transport, as well as dust deposition) are also significantly enhanced during the strongest TPSH years over EA and NP. Through enhancing the TP heat source, stronger TPSH in MAM generates an anticyclonic anomaly in middle and upper troposphere over the TP and over the downstream Pacific region, respectively. These atmospheric circulation anomalies induced by the increased TPSH result in increasing the westerly winds over both EA and NP, which in turn increases dust emissions over the dust source, and dust transport over these two regions, as well as the regional dust cycles. These results suggest that addressing the East Asian dust changes in the future climates requires considering not only increasing greenhouse gas emissions but also the variations of the TP's heat source under global warming.

scholarly journals Modulation of surface sensible heating over the Tibetan Plateau on the interannual variability of East Asian dust cycle

2020 ◽  
Author(s):  
Xiaoning Xie ◽  
Anmin Duan ◽  
Zhengguo Shi ◽  
Xinzhou Li ◽  
Hui Sun ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Heat Source ◽  
Interannual Variability ◽  
East Asian ◽  
Asian Dust ◽  
Dust Concentration ◽  
The Tibetan Plateau ◽  
Dust Source ◽  
Surface Dust ◽  
Surface Sensible Heating

Abstract. Previous observational evidence and numerical simulations have revealed that the surface sensible heating in MAM (March–April–May) over the Tibetan Plateau (TPSH) can affect the Asian regional hydrological cycle, surface energy balance, and climate through altering atmospheric heat source of the Tibetan Plateau (TP). This study aims to investigate the impacts of MAM TPSH on the interannual variability of East Asian dust cycle by use of CAM4-BAM (version 4 of the Community Atmosphere Model coupled to a bulk aerosol model), the MERRA-2 (version 2 of the Modern Era Retrospective-Analysis for Research and Applications) surface dust concentration, and TPSH measurements. Our simulations show that the surface dust concentrations over the East Asian dust source region (EA) and over the northwestern Pacific (NP) in MAM are significantly positively correlated with TPSH, with regionally averaged correlation coefficients of 0.49 for EA and 0.44 for NP. Similar positive correlations are also shown to exist between the MAM TPSH measurements averaged over the 73 observation sites and the surface dust concentration from MERRA-2. Simulation-based comparisons between strongest and weakest TPSH years reveal that, the MAM surface dust concentration in the strongest TPSH years increases with relative differences of 13.1 % over EA and 36.9 % over NP. These corresponding differences are found in MERRA-2 with 22.9 % and 13.3 % over EA and NP, respectively. Further simulated results show that the processes of whole dust cycles (e.g., dust loading, emission, and transport, as well as dust depositions) are also significantly enhanced during the strongest TPSH yeas over EA and NP. Through enhancing the TP heat source, stronger TPSH in MAM generates an anticyclonic anomaly in middle and upper troposphere over TP and over the downstream Pacific region, respectively. These atmospheric circulation anomalies induced by the increased TPSH result in increasing the westerly winds over both EA and NP, which in turn increases dust emissions over the dust source, and dust transports over these two regions, as well as the regional dust cycles. These results suggest that addressing the East Asian dust changes in the future climates require considering not only increasing greenhouse gas emissions but also the variations of the TP's heat source under global warming.

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 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.

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