scholarly journals Modification and comparison of thermal and hydrological parameterization schemes for different underlying surfaces on the Tibetan Plateau in the warm season

2021 ◽  
Author(s):  
Yuan Yuan ◽  
Yaoming Ma ◽  
Hongchao Zuo ◽  
Chenyi Yang ◽  
Ling Yuan ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Warm Season ◽  
The Tibetan Plateau ◽  
Parameterization Schemes

scholarly journals Characteristics of Deep Convective Systems and Initiation during Warm Seasons over China and Its Vicinity

2021 ◽  
Vol 13 (21) ◽  
pp. 4289
Author(s):  
Yang Li ◽  
Yubao Liu ◽  
Yun Chen ◽  
Baojun Chen ◽  
Xin Zhang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
South China ◽  
Warm Season ◽  
Statistical Characteristics ◽  
The Tibetan Plateau ◽  
Spatiotemporal Resolution ◽  
Convective Systems ◽  
Seasonal And Diurnal Variations ◽  
Deep Convective Systems ◽  
Guizhou Plateau

The spatiotemporal statistical characteristics of warm-season deep convective systems, particularly deep convective systems initiation (DCSI), over China and its vicinity are investigated using Himawari-8 geostationary satellite measurements collected during April-September from 2016 to 2020. Based on a satellite brightness temperature multiple-threshold convection identification and tracking method, a total of 47593 deep convective systems with lifetimes of at least 3 h were identified in the region. There are three outstanding local maxima in the region, located in the southwestern, central and eastern Tibetan Plateau and Yunnan-Guizhou Plateau, followed by a region of high convective activities in South China. Most convective systems are developed over the Tibetan Plateau, predominantly eastward-moving, while those developed in Yunnan-Guizhou Plateau and South China mostly move westward and southwestward. The DSCI occurrences become extremely active after the onset of the summer monsoon and tend to reach a maximum in July and August, with a diurnal peak at 11–13 LST in response to the enhanced solar heating and monsoon flows. Several DCSI hotspots are identified in the regions of inland mountains, tropical islands and coastal mountains during daytime, but in basins, plains and coastal areas during nighttime. DCSI over land and oceans exhibits significantly different sub-seasonal and diurnal variations. Oceanic DCSI has an ambiguous diurnal variation, although its sub-seasonal variation is similar to that over land. It is demonstrated that the high spatiotemporal resolution satellite dataset provides rich information for understanding the convective systems over China and vicinity, particularly the complex terrain and oceans where radar observations are sparse or none, which will help to improve the convective systems and initiation nowcasting.

Diurnal Variations of Warm-Season Precipitation East of the Tibetan Plateau over China

2011 ◽  
Vol 139 (9) ◽  
pp. 2790-2810 ◽  
Author(s):  
Xinghua Bao ◽  
Fuqing Zhang ◽  
Jianhua Sun
Keyword(s):  
Tibetan Plateau ◽  
Warm Season ◽  
Propagation Speed ◽  
Western Pacific Subtropical High ◽  
Diurnal Variations ◽  
The Tibetan Plateau ◽  
Diurnal Cycles ◽  
Thermally Driven ◽  
The Difference ◽  
Precipitation Cycle

This study explores the diurnal variations of the warm-season precipitation to the east of the Tibetan Plateau over China using the high-resolution NOAA/Climate Prediction Center morphing technique (CMORPH) precipitation data and the Global Forecast System (GFS) gridded analyses during mid-May to mid-August of 2003–09. Complementary to the past studies using satellite or surface observations, it is found that there are strong diurnal variations in the summertime precipitation over the focus domain to the east of the Tibetan Plateau. These diurnal precipitation cycles are strongly associated with several thermally driven regional mountain–plains solenoids due to the differential heating between the Tibetan Plateau, the highlands, the plains, and the ocean. The diurnal cycles differ substantially from region to region and during the three different month-long periods: the pre-mei-yu period (15 May–15 June), the mei-yu period (15 June–15 July), and the post-mei-yu period (15 July–15 August). In particular, there is a substantial difference in the propagation speed and eastward extent of the peak phase of the dominant diurnal precipitation cycle that is originated from the Tibetan Plateau. This diurnal peak has a faster (slower) eastward propagation speed, the more (less) coherent propagation duration, and thus covers the longest (shortest) distance to the east during the pre-mei-yu (post-mei-yu) period than that during the mei-yu period. The differences in the mean midlatitude westerly flow and in the positioning and strength of the western Pacific subtropical high during different periods are the key factors in explaining the difference in the propagation speed and the eastward extent of this dominant diurnal precipitation cycle.

scholarly journals Isotopic constraints on atmospheric sulfate formation pathways in the Mt. Everest region, southern Tibetan Plateau

2021 ◽  
Author(s):  
Kun Wang ◽  
Shohei Hattori ◽  
Mang Lin ◽  
Sakiko Ishino ◽  
Becky Alexander ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Warm Season ◽  
Cold Season ◽  
Sulfur Cycle ◽  
Formation Mechanisms ◽  
The Tibetan Plateau ◽  
Sampling Campaign ◽  
Water Ph ◽  
Southern Tibetan Plateau ◽  
Sulfate Formation

Abstract. As an important atmosphere constituent, sulfate aerosols exert profound impacts on climate, ecological environment, and human health. The Tibetan Plateau (TP), identified as the Third Pole, contains the largest land ice masses outside the poles and has attracted wide attention on its environment and climatic change. However, the mechanisms of sulfate formation in this specific region remain poorly characterized. Oxygen-17 anomaly (Δ17O) has been used as a probe to constrain the relative importance of different pathways leading to sulfate formation. Here, we report the Δ17O values in atmospheric sulfate collected at a remote site in the Mt. Everest region to decipher the possible formation mechanisms of sulfate in such a pristine environment. Throughout the sampling campaign (April–September 2018), the Δ17O in non-dust sulfate show an average of 1.7 ± 0.5 ‰ which is higher than most existing data in modern atmospheric sulfate. The seasonality of Δ17O in non-dust sulfate exhibits high values in the pre-monsoon and low values in the monsoon, opposite to the seasonality in Δ17O for both sulfate and nitrate (i.e., minima in warm season and maxima in cold season) observed from diverse geographic sites. This high Δ17O in non-dust sulfate found in this region clearly indicates the important role of the S(IV) + O3 pathway in atmospheric sulfate formation promoted by high cloud water pH condition. Overall, our study provides an observational constraint on atmospheric acidity in altering sulfate formation pathways particularly in dust-rich environments, and such identification of key processes provides an important basis for a better understanding of the sulfur cycle in the TP.

scholarly journals Comparison of the diurnal variations of warm-season precipitation for East Asia vs. North America downstream of the Tibetan Plateau vs. the Rocky Mountains

2014 ◽  
Vol 14 (19) ◽  
pp. 10741-10759 ◽  
Author(s):  
Yuanchun Zhang ◽  
Fuqing Zhang ◽  
Jianhua Sun
Keyword(s):  
North America ◽  
Tibetan Plateau ◽  
East Asia ◽  
Diurnal Cycle ◽  
Warm Season ◽  
Wave Number ◽  
The Tibetan Plateau ◽  
Data Set ◽  
Number Frequency ◽  
The Difference

Abstract. A wave-number-frequency spectral decomposition technique is used to analyze the high-resolution NOAA/Climate Prediction Center morphing technique (CMORPH) precipitation data set and to explore the differences and similarities of the diurnal variation of warm-season precipitation in the East Asia and North America downstream of big topography. The predominant phase speed of precipitation at different time scales for North America, averaged over all warm-season months (May–August) for 2003–2010, is ~20 ms−1, which is faster than the speed of ~14 ms−1 calculated for East Asia. Consistent with the recent studies of the precipitation diurnal cycles for these two regions, the difference in the diurnal phase propagation is likely due to the difference in the mean steering level wind speed for these two regions. The wave-number-frequency spectral analysis further reveals the complex, multi-scale, multi-modal nature of the warm-season precipitation variation embedded within the diurnal cycle over both continents, with phase speeds varying from 10 to 30 ms−1 and wave periods varying from diurnal to a few hours. At the diurnal frequency regulated by the thermodynamically driven mountains–plains solenoids (MPSs), increased precipitation for both continents first originates in the afternoon from the eastern edge of big topography and subsequently moves downslope in the evening and reaches the broad plains area at night. More complex diurnal evolutions are observed in East Asia due to the more complex, multistep terrains east of the Tibetan Plateau and the associated localized MPS circulations. Nevertheless, increased variation of precipitation at smaller spatial and temporal scales is evident in the active phase of the dominant diurnal cycle for both continents.

scholarly journals Holocene vegetation and biomass changes on the Tibetan Plateau – a model-pollen data comparison

2011 ◽  
Vol 7 (3) ◽  
pp. 881-901 ◽  
Author(s):  
A. Dallmeyer ◽  
M. Claussen ◽  
U. Herzschuh ◽  
N. Fischer
Keyword(s):  
Tibetan Plateau ◽  
Land Cover ◽  
Land Cover Change ◽  
Vegetation Change ◽  
Climatic Factors ◽  
Warm Season ◽  
Total Biomass ◽  
The Tibetan Plateau ◽  
Vegetation Shift ◽  
Natural Land

Abstract. Results of a transient numerical experiment performed in a coupled atmosphere-ocean-vegetation model with orbital forcing alone are compared to pollen-based vegetation reconstructions covering the last 6000 yr from four representative sites on the Tibetan Plateau. Causes of the vegetation change and consequences of the biomass storage are analysed. In general, simulated and reconstructed vegetation trends at each site are in good agreement. Both methods reveal a general retreat of the biomass-rich vegetation that is particularly manifested in a strong decrease of forests. However, model and reconstructions often differ with regard to the climatic factors causing the vegetation change at each site. The reconstructions primarily identify decreasing summer monsoon precipitation and changes in the temperature of the warm season as the responsible mechanisms for the vegetation shift. In the model, the land cover change mainly originates from differences in warm/cold seasonal temperatures and only to a lesser extent from precipitation changes. According to the model results, the averaged forest fraction on the Plateau shrinks by almost one-third from mid-Holocene (41.4 %) to present-day (28.3 %). Shrubs, whose fraction is quadrupled at present-day (12.3 %), replace most of this forest. Grass fraction increases from 38.1 % during the mid-Holocene to 42.3 % at present-day. This land cover change results in a decrease of living biomass by 0.62 kgC m−2. Total biomass on the Tibetan Plateau decreases by 1.9 kgC m−2, i.e. approx. 6.64 PgC are released due to the natural land cover change.

scholarly journals Increasing warm-season precipitation in Asian drylands and response to reducing spring snow cover over the Tibetan Plateau

2021 ◽  
pp. 1-69
Author(s):  
Jie Zhang ◽  
Qianrong Ma ◽  
Haishan Chen ◽  
Siwen Zhao ◽  
Zhiheng Chen
Keyword(s):  
Water Vapor ◽  
Tibetan Plateau ◽  
Snow Cover ◽  
Northeast Asia ◽  
Warm Season ◽  
Summer Precipitation ◽  
South Asian High ◽  
The Tibetan Plateau ◽  
Water Vapor Flux ◽  
Vapor Flux

AbstractPrecipitation is crucial for life and the ecological environment in Asian drylands. This study investigated precipitation trends in Asian drylands in previous four decades and simulated its possible linkage with snow cover reduction over the Tibetan Plateau. The results show that precipitation has been increasing and contributing to wetter conditions in Asian drylands. The increasing trends can be attributed to the deepened quasi-stationary wave trough around the Lake Balkhash and the meridional water-vapor flux originated from the Arabian Sea and the Bay of Bengal. The mid-latitude waves and eddy disturbances correspond to the northward upper-level Tibetan Plateau (TP) mode of the South Asian High (TP-SAH) and the Afro-Asia jet with cyclonic rotation. Both SAH and Afro-Asia jet anomalies strengthen the ascending motion and northward water-vapor convergence in Asian drylands, and those are favorable for summer precipitation. The anomalous circulations are linked to the following: (1) the reduced snow cover (SC) over the west TP in the late spring results in decreasing soil moisture and increasing diabatic heating in summer and favors northward extension of TP-SAH and the Afro-Asia jet; (2) the reduced TP/SC increases surface temperature over TP and northeast Asia, which decreases the temperature gradient between the TP and the Indian Ocean, between northeast Asia and East Asia. Decreased temperature gradients are beneficial to the southwest-northeast cyclonic rotation of Afro-Asia jet and consequently strengthen the southerly wind and northward water-vapor flux over TP and surrounding regions. This study emphasizes important effects of the reducing TP/SC on intensifying summer precipitation in Asian drylands.

scholarly journals Influence of organic matter on soil hydrothermal processes in the Tibetan Plateau: Observation and parameterization

2021 ◽  
Author(s):  
Jing Sun ◽  
Yingying Chen ◽  
Kun Yang ◽  
Hui Lu ◽  
Long Zhao ◽  
...  
Keyword(s):  
Organic Matter ◽  
Tibetan Plateau ◽  
Land Surface ◽  
High Surface ◽  
Sensible Heat Flux ◽  
Warm Season ◽  
Surface Energy Budget ◽  
The Tibetan Plateau ◽  
Undisturbed Soil ◽  
Soil Hydraulic

AbstractIn the central-eastern Tibetan Plateau (TP) there is abundant organic matter in topsoils, which plays a crucial role in determining soil hydraulic properties that need to be properly described in land surface models. Limited soil parameterizations consider the impacts of soil organic matter (SOM), but they still show poor performance in the TP. A dedicated field campaign is therefore conducted by taking undisturbed soil samples in the central TP to obtain in-situ soil hydraulic parameters and to advance SOM parameterizations. The observed findings are twofold. 1) The SOM pore-size distribution parameter, derived from measured soil water retention curves, has been demonstrated to be much underestimated in previous studies. 2) SOM saturated hydraulic conductivity is overestimated. Accordingly, a new soil hydraulic parameterization is established by modifying a commonly used one based on observations, which is then evaluated by incorporating it into Noah-MP. Compared with the original ones, the new parameterization significantly improves surface soil liquid water simulations at stations with high surface SOM content, especially in the warm season. A further application with the revised Noah-MP indicates that SOM can enhance sensible heat flux but decrease evaporation and subsurface soil temperature in the warm season, and tends to have a much weak effect in the cold season. This study provides insights into the role of SOM in modulating soil state and surface energy budget. Note that, however, there are many other factors at play and the new parameterization is not necessarily applicable beyond the TP.

scholarly journals Isotopic constraints on atmospheric sulfate formation pathways in the Mt. Everest region, southern Tibetan Plateau

2021 ◽  
Vol 21 (10) ◽  
pp. 8357-8376
Author(s):  
Kun Wang ◽  
Shohei Hattori ◽  
Mang Lin ◽  
Sakiko Ishino ◽  
Becky Alexander ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Warm Season ◽  
Cold Season ◽  
Sulfur Cycle ◽  
Formation Mechanisms ◽  
The Tibetan Plateau ◽  
Sampling Campaign ◽  
Water Ph ◽  
Southern Tibetan Plateau ◽  
Sulfate Formation

Abstract. As an important atmosphere constituent, sulfate aerosols exert profound impacts on climate, the ecological environment, and human health. The Tibetan Plateau (TP), identified as the “Third Pole”, contains the largest land ice masses outside the poles and has attracted widespread attention for its environment and climatic change. However, the mechanisms of sulfate formation in this specific region still remain poorly characterized. An oxygen-17 anomaly (Δ17O) has been used as a probe to constrain the relative importance of different pathways leading to sulfate formation. Here, we report the Δ17O values in atmospheric sulfate collected at a remote site in the Mt. Everest region to decipher the possible formation mechanisms of sulfate in such a pristine environment. Throughout the sampling campaign (April–September 2018), the Δ17O in non-dust sulfate show an average of 1.7 ‰±0.5 ‰, which is higher than most existing data on modern atmospheric sulfate. The seasonality of Δ17O in non-dust sulfate exhibits high values in the pre-monsoon and low values in the monsoon, opposite to the seasonality in Δ17O for both sulfate and nitrate (i.e., minima in the warm season and maxima in the cold season) observed from diverse geographic sites. This high Δ17O in non-dust sulfate found in this region clearly indicates the important role of the S(IV)+O3 pathway in atmospheric sulfate formation promoted by conditions of high cloud water pH. Overall, our study provides an observational constraint on atmospheric acidity in altering sulfate formation pathways, particularly in dust-rich environments, and such identification of key processes provides an important basis for a better understanding of the sulfur cycle in the TP.

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