scholarly journals Detecting and Attributing Evapotranspiration Deviations Using Dynamical Downscaling and Convection-Permitting Modeling over the Tibetan Plateau

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2096
Author(s):  
Jingyu Dan ◽  
Yanhong Gao ◽  
Meng Zhang
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Dynamical Downscaling ◽  
Water Cycle ◽  
Monsoon Season ◽  
Precipitation Pattern ◽  
The Tibetan Plateau ◽  
Local Climate ◽  
Surface Data ◽  
Global Land

Terrestrial evapotranspiration (ET) over the Tibetan Plateau (TP) exerts considerable impacts on the local climate and the water cycle. However, the high-altitude, mountainous areas over the TP pose a challenge for field observations. To finely capture its ET characteristics, we employed dynamical downscaling modeling (DDM) with a 28 km resolution and convection-permitting modeling (CPM) with a 4 km resolution in a normal climatology year, 2014. The benchmark data were the surface energy balance–based global land ET dataset (EB). Other compared data included the Global Land-Surface Data Assimilation System (GLDAS) and two reanalysis datasets: ERA-Interim and ERA5. Results showed that EB exhibits a gradient from the southeastern to northwestern TP, which is in line with the precipitation pattern. GLDAS generally reproduces the annual mean magnitude and pattern but poorly represents the seasonal variations. DDM and CPM perform well in the monsoon season but underestimate ET in the non-monsoon season. The two reanalysis datasets greatly overestimate the ET in the monsoon season, but ERA-Interim performs well in the non-monsoon season. All five datasets underestimate the ET over tundra and snow/ice areas, both in the annual and seasonal means. ET deviations are dominated by precipitation deviations in the monsoon season and by surface net radiation deviations in the non-monsoon season.

Detecting evapotranspiration biases in reanalyses and regional climate modeling

2021 ◽  
Author(s):  
Jingyu Dan ◽  
Yanhong Gao
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Water Cycle ◽  
Climate Modeling ◽  
Global Climate ◽  
Monsoon Season ◽  
Regional Climate ◽  
Horizontal Resolution ◽  
The Tibetan Plateau ◽  
Free Atmosphere

<p>As the highest plateau in the world, the Tibetan Plateau (TP) exerts great impacts on regional and global climate and water cycle through interactions between land and free atmosphere. Terrestrial evapotranspiration is a critical component of the Earth's water cycle. To better understand the heterogeneity of the evapotranspiration over the Tibetan Plateau and its influences, we conducted a whole year dynamical downscale modelling (DDM) with the horizontal resolution at 28km and a convection permitting modelling (CPM) at 4km for 2014. DDM and CPM simulation results are compared with an satellite retrieving dataset, which is referred as OBS in the following, the global land surface data assimilation system (GLDAS) and two commonly used reanalyses ERA-Interim and ERA5, as well. The annual and seasonal means and seasonal variabilities are inter-compared. The evapotranspiration over ten dominant land use types are investigated based on six datasets. Differences with the satellite dataset are illustrated and relationships with soil moisture and temperature, precipitation and radiation are explored. The followings are obtained. GLDAS generally reproduces magnitude and pattern of the OBS; reanalyses overestimate, DDM and CPM underestimate compared to the OBS and GLDAS.</p><p>The overestimations in reanalyses occur in the monsoon season and the underestimations in DDM and CPM occur in the non-monsoon season. Large evapotranspiration biases exist over the vegetated ground which exert large impacts on the TP-average biases for growing season.</p>

Estimation of land surface key parameters for the study of energy and water cycle over the Tibetan Plateau based on geostationary and polar orbiting satellites

2021 ◽  
Author(s):  
Lei Zhong ◽  
Yaoming Ma ◽  
Zhongbo Su ◽  
Weiqiang Ma ◽  
Zeyong Hu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Water Cycle ◽  
Surface Characteristic ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
The Tibetan Plateau ◽  
Characteristic Parameters ◽  
Turbulent Heat Fluxes ◽  
Land Surface Parameters

<p>Estimation of land surface characteristic parameters and turbulent heat fluxes is important for energy and water cycle studies, especially on the Tibetan Plateau (TP), where the topography is unique and the land-atmosphere interactions are strong. The land surface heating conditions also directly influence the movement of atmospheric circulation. However, high temporal resolution information on the plateau-scale land surface parameters has lacked for a long time, which significantly limits the understanding of diurnal variations in land-atmosphere interactions. On the other hand, how to remove cloud effects for optical satellite images is another important research issue. Based on Chinese FY geostationary satellite data and other polar orbiting satellite data, the hourly land surface characteristic parameters and turbulent heat fluxes were estimated. A new cloud‐free time series of vegetation index data sets was reconstructed, and the vegetation density showed a general increasing trend along with a warming trend in the TP. The regions showing significant increases accounted for 7.63% of the total Tibetan territory. Downwelling shortwave and longwave radiation parameterization schemes were improved to derive all-sky radiation over the TP. The diurnal and seasonal cycles of the land surface parameters were clearly identified, and their spatial distribution was found to be consistent with the heterogeneous land surface conditions and the general hydrometeorological conditions of the TP.</p>

Influence of Mesoscale Soil Moisture Patterns on Convective Initiation over the Tibetan Plateau

2020 ◽  
Author(s):  
Emma Barton ◽  
Christopher Taylor ◽  
Cornelia Klein ◽  
Phil Harris
Keyword(s):  
Soil Moisture ◽  
Tibetan Plateau ◽  
Land Surface ◽  
Climate Models ◽  
Monsoon Season ◽  
The Tibetan Plateau ◽  
Extreme Rainfall Events ◽  
Convective Initiation ◽  
Hourly Data ◽  
The Impact

<p>The Tibetan Plateau is the highest and most extensive plateau in the world, profoundly affecting climate and weather in the region. Due to its average elevation of more than 4000m, provides a strong thermal and dynamical forcing in the mid-troposphere during the summer months, fostering the frequent development of intense storms. Mesoscale convective systems (MCSs) are known to be associated with particularly extreme rainfall events and contribute up to ~60% of rainfall over the Tibetan Plateau (TP) and adjacent areas. In particular, MCSs that form on the TP may move off and bring heavy rain and flooding to downstream parts of China, affecting millions of people. A better understanding of the processes that impact MCS genesis over the TP could contribute to improved forecasting of these extreme events. Furthermore, there is strong evidence for accelerated climate warming on the TP, which may affect convection and makes the identification of factors for MCS development even more important.</p><p>Previous work in the Sahel has shown that mesoscale soil moisture patterns can influence the initiation of new MCSs, however the relationship has yet to be investigated for the more hydrologically and topographically complex TP. In this study we investigate the impact of mesoscale soil moisture features on convective initiation over the TP during the monsoon season (May – September) using satellite imagery. Convective clouds are identified using the Fengyun-2 cloud top temperature product. Fengyun-2 is a series of geostationary satellites that provide hourly data, allowing us to track systems as they evolve. Land surface temperature anomalies are used as a proxy to map pre-storm mesoscale soil moisture patterns.</p><p>Despite the presence of complex topography, we identify a tendency for MCS initiations to occur in the vicinity of mesoscale soil moisture gradients. Our results suggest that improved representation of land-atmosphere coupling on the TP within weather and climate models could impact the entire region.</p>

scholarly journals Comparison of satellite based evapotranspiration estimates over the Tibetan Plateau

2016 ◽  
Author(s):  
Jian Peng ◽  
Alexander Loew ◽  
Xuelong Chen ◽  
Yaoming Ma ◽  
Zhongbo Su
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Water Cycle ◽  
Global Climate ◽  
Spatial Scales ◽  
Heat Fluxes ◽  
The Tibetan Plateau ◽  
Comparison Results ◽  
Mean Square Difference ◽  
Land Surface Parameters

Abstract. The Tibetan Plateau (TP) plays a major role in regional and global climate. Land–atmosphere interactions are largely influenced by surface latent heat fluxes through evapotranspiration. Despite its importance, a ccurate estimation of ET over the TP remains challenging, due to its unique and special geographical position and physical environment. Satellite observations allow for ET estimat ion at high temporal and spatial scales. The purpose of this paper is to provide a detailed cross comparison of existing ET products over the TP. Six available ET products based on different approaches and using different forcing data are included for comparison. Results show that all products capture well the seasonal variability with minimum ET in the summer and maximum ET in the winter. Regarding the spatial pattern, the High Resolution Land Surface Parameters from Space (HOLAPS) ET demonstrator dataset is very similar to the LandFlux-EVAL dataset (a benchmark ET product from the Global Energy and Water Cycle Experiment), with ET decreases from the s outheast to northwest over the TP. Further comparison against the LandFlux-EVAL over four sub-regions reveals that HOLAPS agrees best with LandFlux-EVAL having the highest correlation coefficient (R) and lowest Root Mean Square Difference (RMSD). These results indicate the potential for the application of the HOLAPS demonstrator dataset in understanding the and–atmosphere–biosphere interactions over the TP.

Trends of land surface heat fluxes on the Tibetan Plateau from 2001 to 2012

2017 ◽  
Vol 37 (14) ◽  
pp. 4757-4767 ◽  
Author(s):  
Cunbo Han ◽  
Yaoming Ma ◽  
Xuelong Chen ◽  
Zhongbo Su
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Surface Heat ◽  
Heat Fluxes ◽  
The Tibetan Plateau ◽  
Surface Heat Fluxes ◽  
Land Surface Heat Fluxes

scholarly journals Impact of Land Use Change on the Local Climate over the Tibetan Plateau

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
Jiming Jin ◽  
Shihua Lu ◽  
Suosuo Li ◽  
Norman L. Miller
Keyword(s):  
Land Use ◽  
Tibetan Plateau ◽  
Land Use Change ◽  
Lower Surface ◽  
Warming Trend ◽  
The Tibetan Plateau ◽  
Area Index ◽  
Local Climate ◽  
Significant Downward Trend ◽  
Three Rivers

Observational data show that the remotely sensed leaf area index (LAI) has a significant downward trend over the east Tibetan Plateau (TP), while a warming trend is found in the same area. Further analysis indicates that this warming trend mainly results from the nighttime warming. The Single-Column Atmosphere Model (SCAM) version 3.1 developed by the National Center for Atmospheric Research is used to investigate the role of land use change in the TP local climate system and isolate the contribution of land use change to the warming. Two sets of SCAM simulations were performed at the Xinghai station that is located near the center of the TP Sanjiang (three rivers) Nature Reserve where the downward LAI trend is largest. These simulations were forced with the high and low LAIs. The modeling results indicate that, when the LAI changes from high to low, the daytime temperature has a slight decrease, while the nighttime temperature increases significantly, which is consistent with the observations. The modeling results further show that the lower surface roughness length plays a significant role in affecting the nighttime temperature increase.

Recent climate changes over the Tibetan Plateau and their impacts on energy and water cycle: A review

2014 ◽  
Vol 112 ◽  
pp. 79-91 ◽  
Author(s):  
Kun Yang ◽  
Hui Wu ◽  
Jun Qin ◽  
Changgui Lin ◽  
Wenjun Tang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Climate Changes ◽  
Water Cycle ◽  
The Tibetan Plateau ◽  
Recent Climate
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