The impact of the Westerlies on the PBL growth and land surface energy balance on the north of the central Himalaya

2020 ◽  
Author(s):  
Xuelong Chen ◽  
Yue Lai ◽  
Yaoming Ma
Keyword(s):  
Energy Balance ◽  
Tibetan Plateau ◽  
Surface Energy ◽  
Land Surface ◽  
Surface Energy Balance ◽  
The Tibetan Plateau ◽  
Central Himalaya ◽  
Mountainous Areas ◽  
The North ◽  
The Impact

<p>The spatial-temporal structure of the Planetary Boundary Layer (PBL) over mountainous areas can be strongly modified by topography. The PBL over the mountainous terrain of the Tibetan Plateau (TP) is more complex than that observed over its flat areas. To date, there have been no detailed analyses which have taken into account the topography effects exerted on PBL growth over the Tibetan Plateau (TP). A clear understanding of the processes involved in the PBL growth and depth over the TP’s mountainous areas is therefore long overdue.<br>The PBL in the Himalayan region of the Tibetan Plateau (TP) is important to the study of interaction between the area’s topography and synoptic circulation. This study used radiosonde, in-situ measurements and ECMWF ERA5 reanalysis dataset to investigate the vertical structure of the PBL and the land surface energy balance in the Rongbuk Valley on the north of the central Himalaya, and their association with the Westerlies, which control the climate of the Himalaya in winters. Measurements show that the altitude of the PBL’s top in November was the highest of three intensive observation periods (i.e., June, August and November). The PBLs in November appeared to have been influenced by the Westerlies which prevails in this region during the non-monsoon season. We discovered that the deep PBLs seen in November correlate with the downward transmission of the Westerlies to the valley floor (DTWTV). It was found that DTWTV happened in the direction of southwest when the synoptic wind above the valley ridges height blow from southwest, which is parallel to the valley axis. DTWTV happened in the direction of southwest promotes a stronger near-surface wind, smaller aerodynamic resistance, and larger sensible heat flux, which cause PBLs grow high.</p>

scholarly journals Evapotranspiration Estimation Using Surface Energy Balance System Model: A Case Study in the Nagqu River Basin

Atmosphere ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 268 ◽  
Author(s):  
Lei Zhong ◽  
Kepiao Xu ◽  
Yaoming Ma ◽  
Ziyu Huang ◽  
Xian Wang ◽  
...  
Keyword(s):  
Energy Balance ◽  
Tibetan Plateau ◽  
Surface Energy ◽  
River Basin ◽  
Land Surface ◽  
Surface Energy Balance ◽  
Hydrological Cycle ◽  
The Tibetan Plateau ◽  
Balance System ◽  
Northern Tibetan Plateau

Calculation of actual evapotranspiration (AET) is of vital importance for the study of climate change, ecosystem carbon cycling, flooding, drought, and agricultural water demand. It is one of the more important components in the hydrological cycle and surface energy balance (SEB). How to accurately estimate AET especially for the Tibetan Plateau (TP) with complex terrain remains a challenge for the scientific community. Using multi-sensor remote sensing data, meteorological forcing data, and field observations, AET was derived for the Nagqu river basin of the Northern Tibetan Plateau from a surface energy balance system (SEBS) model. As inputs for SEBS, improved algorithms and datasets for land surface albedo and a cloud-free normalized difference vegetation index (NDVI) were also constructed. The model-estimated AET were compared with results by using the combinatory method (CM). The validation indicated that the model estimates of AET agreed well with the correlation coefficient, the root mean square error, and the mean percentage error of 0.972, 0.052 mm/h, and −10.4%, respectively. The comparison between SEBS estimation and CM results also proved the feasibility of parameterization schemes for land surface parameters and AET.

scholarly journals High-resolution modelling of interactions between soil moisture and convection development in mountain enclosed Tibetan basin

2015 ◽  
Vol 12 (5) ◽  
pp. 4631-4675
Author(s):  
T. Gerken ◽  
W. Babel ◽  
M. Herzog ◽  
K. Fuchs ◽  
F. Sun ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Energy Balance ◽  
Tibetan Plateau ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Local Development ◽  
Lake Basin ◽  
Strong Impact ◽  
The Tibetan Plateau ◽  
Moist Convection

Abstract. The Tibetan Plateau plays a significant role in the atmospheric circulation and the Asian monsoon system. Turbulent surface fluxes and the evolution of boundary layer clouds to deep and moist convection provide a feedback system that modifies the Plateau's surface energy balance on scales that are currently unresolved in mesoscale models. This work analyses the land surface's role and specifically the influence of soil moisture on the triggering of convection at a cross-section of the Nam Co Lake basin, 150 km north of Lhasa using a cloud resolving atmospheric model with a fully coupled surface. The modelled turbulent fluxes and development of convection compare reasonably well with the observed weather. The simulations span Bowen-ratios of 0.5 to 2.5. It is found that convection development is strongest at intermediate soil moistures. Dry cases with soils close to the permanent wilting point are moisture limited in the convection development, while convection in wet soil moisture cases is limited by cloud cover reducing incoming solar radiation and sensible heat fluxes. This has a strong impact on the surface energy balance. This study also shows that local development of convection is an important mechanism for the upward transport of water vapour that originates from the lake basin that can then be transported to dryer regions of the plateau. Both processes demonstrate the importance of soil moisture and surface–atmosphere interactions on the energy and hydrological cycles of the Tibetan Plateau.

scholarly journals Development of a 10 year (2001–2010) 0.1° dataset of land-surface energy balance for mainland China

2014 ◽  
Vol 14 (10) ◽  
pp. 14471-14518 ◽  
Author(s):  
X. Chen ◽  
Z. Su ◽  
Y. Ma ◽  
S. Liu ◽  
Q. Yu ◽  
...  
Keyword(s):  
Energy Balance ◽  
High Resolution ◽  
Surface Energy ◽  
Land Surface ◽  
Surface Energy Balance ◽  
Water Cycle ◽  
Surface Radiation ◽  
Balance Model ◽  
Wave Radiation ◽  
The Tibetan Plateau

Abstract. In the absence of high resolution estimates of the components of surface energy balance for China, we developed an algorithm based on the surface energy balance system (SEBS) to generate a dataset of land-surface energy and water fluxes on a monthly time scale from 2001 to 2010 at a 0.1° × 0.1° spatial resolution by using multi-satellite and meteorological forcing data. A remote-sensing-based method was developed to estimate canopy height, which was used to calculate roughness length and flux dynamics. The land-surface flux dataset was validated against "ground-truth" observations from 11 flux tower stations in China. The estimated fluxes correlate well with the stations' measurements for different vegetation types and climatic conditions (average bias = 15.3 W m−2, RMSE = 26.4 W m−2). The quality of the data product was also assessed against the GLDAS dataset. The results show that our method is efficient for producing a high-resolution dataset of surface energy flux for the Chinese landmass from satellite data. The validation results demonstrate that more accurate downward long-wave radiation datasets are needed to be able to accurately estimate turbulent fluxes and evapotranspiration when using the surface energy balance model. Trend analysis of land-surface radiation and energy exchange fluxes revealed that the Tibetan Plateau has undergone relatively stronger climatic change than other parts of China during the last 10 years. The capability of the dataset to provide spatial and temporal information on water-cycle and land–atmosphere interactions for the Chinese landmass is examined. The product is free to download for studies of the water cycle and environmental change in China.

Relating Precipitating Ice Radiative Effects to Surface Energy Balance and Temperature Biases Over the Tibetan Plateau in Winter

2019 ◽  
Vol 124 (23) ◽  
pp. 12455-12467
Author(s):  
Wei‐Liang Lee ◽  
Jui‐Lin Frank Li ◽  
Kuan‐Man Xu ◽  
Ettamal Suhas ◽  
Jonathan H. Jiang ◽  
...  
Keyword(s):  
Energy Balance ◽  
Tibetan Plateau ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
The Tibetan Plateau ◽  
Radiative Effects

scholarly journals High-resolution modelling of interactions between soil moisture and convective development in a mountain enclosed Tibetan Basin

2015 ◽  
Vol 19 (9) ◽  
pp. 4023-4040 ◽  
Author(s):  
T. Gerken ◽  
W. Babel ◽  
M. Herzog ◽  
K. Fuchs ◽  
F. Sun ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Energy Balance ◽  
Tibetan Plateau ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Local Development ◽  
Lake Basin ◽  
Strong Impact ◽  
The Tibetan Plateau ◽  
Moist Convection

Abstract. The Tibetan Plateau plays a significant role in atmospheric circulation and the Asian monsoon system. Turbulent surface fluxes and the evolution of boundary-layer clouds to deep and moist convection provide a feedback system that modifies the plateau's surface energy balance on scales that are currently unresolved in mesoscale models. This work analyses the land surface's role and specifically the influence of soil moisture on the triggering of convection at a cross section of the Nam Co Lake basin, 150 km north of Lhasa using a cloud-resolving atmospheric model with a fully coupled surface. The modelled turbulent fluxes and development of convection compare reasonably well with the observed weather. The simulations span Bowen ratios of 0.5 to 2.5. It is found that convective development is the strongest at intermediate soil moisture. Dry cases with soils close to the permanent wilting point are moisture limited in convective development, while convection in wet soil moisture cases is limited by cloud cover reducing incoming solar radiation and sensible heat fluxes, which has a strong impact on the surface energy balance. This study also shows that local development of convection is an important mechanism for the upward transport of water vapour, which originates from the lake basin that can then be transported to dryer regions of the plateau. Both processes demonstrate the importance of soil moisture and surface–atmosphere interactions on the energy and hydrological cycles of the Tibetan Plateau.

An Improvement of Roughness Height Parameterization of the Surface Energy Balance System (SEBS) over the Tibetan Plateau

2013 ◽  
Vol 52 (3) ◽  
pp. 607-622 ◽  
Author(s):  
Xuelong Chen ◽  
Zhongbo Su ◽  
Yaoming Ma ◽  
Kun Yang ◽  
Jun Wen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Balance ◽  
Tibetan Plateau ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Bare Soil ◽  
Roughness Height ◽  
The Tibetan Plateau ◽  
Sensible Heat ◽  
Balance System

AbstractRoughness height for heat transfer is a crucial parameter in the estimation of sensible heat flux. In this study, the performance of the Surface Energy Balance System (SEBS) has been tested and evaluated for typical land surfaces on the Tibetan Plateau on the basis of time series of observations at four sites with bare soil, sparse canopy, dense canopy, and snow surface, respectively. Both under- and overestimation at low and high sensible heat fluxes by SEBS was discovered. Through sensitivity analyses, it was identified that these biases are related to the SEBS parameterization of bare soil’s excess resistance to heat transfer (kB−1, where k is the von Kármán constant and B−1 is the Stanton number). The kB−1 of bare soil in SEBS was replaced. The results show that the revised model performs better than the original model.

scholarly journals Estimation of Hourly Land Surface Heat Fluxes over the Tibetan Plateau by the Combined Use of Geostationary and Polar Orbiting Satellites

2018 ◽  
Author(s):  
Lei Zhong ◽  
Yaoming Ma ◽  
Zeyong Hu ◽  
Yunfei Fu ◽  
Yuanyuan Hu ◽  
...  
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Surface Energy ◽  
Land Surface ◽  
Surface Energy Balance ◽  
Surface Heat ◽  
Heat Fluxes ◽  
The Tibetan Plateau ◽  
Surface Heat Fluxes ◽  
Land Surface Heat Fluxes

Abstract. The estimation of land surface heat fluxes has significant meaning for energy and water cycle studies, especially for the Tibetan Plateau (TP), which has unique topography and strong land–atmosphere interactions. The land surface heating status also directly influences the movement of atmospheric circulation. However, for a long time, plateau-scale land surface heat flux information with high temporal resolution has been lacking, which greatly limits understanding of diurnal variations in land–atmosphere interactions. Based on geostationary and polar orbiting satellite data, a surface energy balance system (SEBS) was used in this paper to derive hourly land surface heat fluxes with a spatial resolution of 10 km. Six stations scattered through the TP and equipped for flux tower measurements were used to correct the energy imbalance problem existing in the measurements and to perform cross-validation. The results showed good agreement between derived fluxes and in situ measurements through 3738 validation samples. The RMSEs for net radiation flux, sensible heat flux, latent heat flux and soil heat flux were 76.63 W m−2, 60.29 W m−2, 64.65 W m−2 and 37.5 W m−2, respectively. The derived results were also found to be superior to GLDAS flux products (RMSEs for the surface energy balance components were 114.32 W m−2, 67.77 W m−2, 75.6 W m−2 and 40.05 W m−2, respectively). The diurnal and seasonal cycles of land surface energy balance components were clearly identified. Their spatial distribution was found to be consistent with the heterogeneous land surface status and general hydrometeorological conditions of the TP.

scholarly journals Surface energy balance closure at ten sites over the Tibetan plateau

2018 ◽  
Vol 259 ◽  
pp. 317-328 ◽  
Author(s):  
Yu-Fei Xin ◽  
Fei Chen ◽  
Ping Zhao ◽  
Michael Barlage ◽  
Peter Blanken ◽  
...  
Keyword(s):  
Energy Balance ◽  
Tibetan Plateau ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
The Tibetan Plateau ◽  
Energy Balance Closure
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