Comparative analysis of land surface parameters on three typical underlying surfaces over the Tibetan Plateau

2020 ◽  
Author(s):  
Zhangwei Ding ◽  
Yaoming Ma ◽  
Xuelong Chen
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Alpine Meadow ◽  
Bare Soil ◽  
Alpine Grassland ◽  
The Tibetan Plateau ◽  
Transfer Coefficients ◽  
Surface Parameters ◽  
Yearly Average ◽  
Land Surface Parameters

<p>To improve land surface parameterizations of radiation and energy balance, eddy covariance measurements were performed on three typical land covers types over the Tibetan Plateau , including bare soil, naturally sparse alpine meadow and dense alpine grassland from 2007 to 2012. We investigated how land surface parameters changed with surface properties and vegetation canopy growth and analyzed the characteristics of diurnal and seasonal variations of aerodynamic parameters. Results show that the annual mean surface albedo and surface roughness lengths for momentum were 0.27 and 2.29 cm, 0.241 and 1.39 cm and 0.19 and 6.52 cm over bare soil, naturally sparse alpine meadow and dense alpine grassland areas, respectively. The yearly average turbulence transfer coefficients for momentum and sensible heat under neutral condition were 4.12×10<sup>-3</sup> and 2.29×10<sup>-3</sup>, 4.11×10<sup>-3</sup> and 2.33×10<sup>-3</sup> and 6.67×10<sup>-3</sup> and 4.14×10<sup>-3</sup>, respectively. The median values of κB<sup>-1</sup> averaged over multiple years are 6.65, 5.89 and 4.88, respectively.</p>

scholarly journals Analysis of land surface parameters and turbulence characteristics over the Tibetan Plateau and surrounding region

2016 ◽  
Vol 121 (16) ◽  
pp. 9540-9560 ◽  
Author(s):  
Yinjun Wang ◽  
Xiangde Xu ◽  
Huizhi Liu ◽  
Yueqing Li ◽  
Yaohui Li ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
The Tibetan Plateau ◽  
Turbulence Characteristics ◽  
Surface Parameters ◽  
Land Surface Parameters

Developing the soil texture effects on the surface resistance to bare soil based on MOD16 algorithm to estimate evapotranspiration over the Tibetan Plateau

2020 ◽  
Author(s):  
Ling Yuan ◽  
Yaoming Ma ◽  
Xuelong Chen
Keyword(s):  
Tibetan Plateau ◽  
Soil Texture ◽  
Land Surface ◽  
Bare Soil ◽  
The Other ◽  
Accurate Estimation ◽  
Surface Model ◽  
The Tibetan Plateau ◽  
The Mean ◽  
Modified Algorithm

<p>Evapotranspiration (ET), composed of evaporation (ETs) and transpiration (ETc) and intercept water (ETw), plays an indispensable role in the water cycle and energy balance of land surface processes. A more accurate estimation of ET variations is essential for natural hazard monitoring and water resource management. For the cold, arid, and semi-arid regions of the Tibetan Plateau (TP), previous studies often overlooked the decisive role of soil properties in ETs rates. In this paper, an improved algorithm for ETs in bare soil and an optimized parameter for ETc over meadow based on MOD16 model are proposed for the TP. The nonlinear relationship between surface evaporation resistance (r<sub>s</sub><sup>s</sup>) and soil surface hydration state in different soil texture is redefined by ground-based measurements over the TP. Wind speed and vegetation height were integrated to estimate aerodynamic resistance by Yang et al. (2008). The validated value of the mean potential stomatal conductance per unit leaf area (C<sub>L</sub>) is 0.0038m s<sup>-1</sup>. And the algorithm was then compared with the original MOD16 algorithm and a soil water index–based Priestley-Taylor algorithm (SWI–PT). After examining the performance of the three models at 5 grass flux tower sites in different soil texture over the TP, East Asia, and America, the validation results showed that the half-hour estimates from the improved-MOD16 were closer to observations than those of the other models under the all-weather in each site. The average correlation coefficient(R<sup>2</sup>) of the improved-MOD16 model was 0.83, compared with 0.75 in the original MOD16 model and 0.78 in SWI-PT model. The average values of the root mean square error (RMSE) are 35.77W m<sup>-2</sup>, 79.46 W m<sup>-2</sup>, and 73.88W m<sup>-2</sup> respectively. The average values of the mean bias (MB) are -4.08W m<sup>-2</sup>, -52.36W m<sup>-2</sup>, and -11.74 W m<sup>-2</sup> overall sites, respectively. The performance of these algorithms are better achieved on daily (R<sup>2</sup>=0.81, RMSE=17.22W m<sup>-2</sup>, MB=-4.12W m<sup>-2</sup>; R<sup>2</sup>=0.64, RMSE=56.55W m<sup>-2</sup>, MB=-48.74W m<sup>-2</sup>; R2=0.78, RMSE=22.3W m<sup>-2</sup>, MB=-9.82W m<sup>-2</sup>) and monthly (R2=0.93, RMSE=23.35W m<sup>-2</sup>, MB=-2.8W m<sup>-2</sup>; R2=0.86, RMSE=69.11W m<sup>-2</sup>, MB=-39.5W m<sup>-2</sup>; R2=0.79, RMSE=62.8W m<sup>-2</sup>, MB=-9.7W m<sup>-2</sup>) scales. Overall, the results showed that the newly developed MOD16 model captured ET more accurately than the other two models. The comparisons between the modified algorithm and two mainstream methods suggested that the modified algorithm could produce high accuracy ET over the meadow sites and has great potential for land surface model improvements and remote sensing ET promotion for the ET region.</p>

scholarly journals Precipitation and aridity index regulating spatial patterns of vegetation production and species diversity based on alpine grassland transect, Tibetan Plateau

2016 ◽  
Author(s):  
Jian Sun
Keyword(s):  
Tibetan Plateau ◽  
Primary Production ◽  
Alpine Meadow ◽  
Net Primary Production ◽  
Aridity Index ◽  
Alpine Grassland ◽  
The Tibetan Plateau ◽  
Aboveground Net Primary Production ◽  
Alpine Steppe ◽  
Unimodal Pattern

Although the relationship between the aboveground net primary production (ANPP) and speciesdiversity (SR) have been widely reported, there is considerable disagreement about the fitting patterns of SR–ANPP, which has been variously described as ‘positive’, ‘negative’, ‘unimodal’, ‘U-shaped’ and so on. Not surprisingly, the effect-factors including precipitation, aridity index and geographic conditions (e.g.,altitude, longitude and latitude) on ANPP and SR continue to interest researchers, especially the effects at high altitude regions. We investigated ANPP and SR from 113 sampled sites (399 plots) across alpine meadow and steppe in the Tibetan Plateau, which included Tibet, Qinghai and Sichuan province. The effects of various environmental factors (precipitation, temperature, aridity index, altitude, longitude,latitude and vegetation type on SR and ANPP) were explored. The results indicate that a unimodal pattern was confirmed between ANPP and SR in alpine steppe (R 2 =0.45, P <0.0001), alpine meadow ( R 2 =0.4, P <0.0001), and all samples across alpine grassland ( R 2 =0.52, P <0.0001). For the aboveground net primary production, the appropriate precipitation and aridity is 600mm and 42, respectively. Under thesame moisture conditions, the maximum value of diversity is 0.75. Longitude ( R 2 =0.69, P <0.0001) and altitude ( R 2 =0.48, P <0.0001) have positive and negative effects on aboveground net primary production, and a similar relationship exists with diversity ( R 2 =0.44, P <0.0001 and R 2 =0.3, P <0.0001).The same patterns of diversity and production responding to precipitation and the aridity index were evident in alpine steppe and meadow, and a unimodal pattern was confirmed between ANPP and SR in both locations.

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

&lt;p&gt;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&amp;#8208;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.&lt;/p&gt;

scholarly journals Field evidence for earlier leaf-out dates in alpine grassland on the eastern Tibetan Plateau from 1990 to 2006

2014 ◽  
Vol 10 (8) ◽  
pp. 20140291 ◽  
Author(s):  
H. K. Zhou ◽  
B. Q. Yao ◽  
W. X. Xu ◽  
X. Ye ◽  
J. J. Fu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Alpine Meadow ◽  
Grassland Management ◽  
The Tibetan Plateau ◽  
Spring Phenology ◽  
Ecosystem Responses ◽  
Vegetation Communities ◽  
Alpine Steppe ◽  
Field Evidence

Worldwide, many plant species are experiencing an earlier onset of spring phenophases due to climate warming. Rapid recent temperature increases on the Tibetan Plateau (TP) have triggered changes in the spring phenology of the local vegetation. However, remote sensing studies of the land surface phenology have reached conflicting interpretations about green-up patterns observed on the TP since the mid-1990s. We investigated this issue using field phenological observations from 1990 to 2006, for 11 dominant plants on the TP at the levels of species, families (Gramineae—grasses and Cyperaceae—sedges) and vegetation communities (alpine meadow and alpine steppe). We found a significant trend of earlier leaf-out dates for one species ( Koeleria cristata ). The leaf-out dates of both Gramineae and Cyperaceae had advanced (the latter significantly, starting an average of 9 days later per year than the former), but the correlation between them was significant. The leaf-out dates of both vegetation communities also advanced, but the pattern was only significant in the alpine meadow. This study provides the first field evidence of advancement in spring leaf phenology on the TP and suggests that the phenology of the alpine steppe can differ from that of the alpine meadow. These findings will be useful for understanding ecosystem responses to climate change and for grassland management on the TP.

scholarly journals Precipitation and aridity index regulating spatial patterns of vegetation production and species diversity based on alpine grassland transect, Tibetan Plateau

2016 ◽  
Author(s):  
Jian Sun
Keyword(s):  
Tibetan Plateau ◽  
Primary Production ◽  
Alpine Meadow ◽  
Net Primary Production ◽  
Aridity Index ◽  
Alpine Grassland ◽  
The Tibetan Plateau ◽  
Aboveground Net Primary Production ◽  
Alpine Steppe ◽  
Unimodal Pattern

Although the relationship between the aboveground net primary production (ANPP) and speciesdiversity (SR) have been widely reported, there is considerable disagreement about the fitting patterns of SR–ANPP, which has been variously described as ‘positive’, ‘negative’, ‘unimodal’, ‘U-shaped’ and so on. Not surprisingly, the effect-factors including precipitation, aridity index and geographic conditions (e.g.,altitude, longitude and latitude) on ANPP and SR continue to interest researchers, especially the effects at high altitude regions. We investigated ANPP and SR from 113 sampled sites (399 plots) across alpine meadow and steppe in the Tibetan Plateau, which included Tibet, Qinghai and Sichuan province. The effects of various environmental factors (precipitation, temperature, aridity index, altitude, longitude,latitude and vegetation type on SR and ANPP) were explored. The results indicate that a unimodal pattern was confirmed between ANPP and SR in alpine steppe (R 2 =0.45, P <0.0001), alpine meadow ( R 2 =0.4, P <0.0001), and all samples across alpine grassland ( R 2 =0.52, P <0.0001). For the aboveground net primary production, the appropriate precipitation and aridity is 600mm and 42, respectively. Under thesame moisture conditions, the maximum value of diversity is 0.75. Longitude ( R 2 =0.69, P <0.0001) and altitude ( R 2 =0.48, P <0.0001) have positive and negative effects on aboveground net primary production, and a similar relationship exists with diversity ( R 2 =0.44, P <0.0001 and R 2 =0.3, P <0.0001).The same patterns of diversity and production responding to precipitation and the aridity index were evident in alpine steppe and meadow, and a unimodal pattern was confirmed between ANPP and SR in both locations.

scholarly journals Some practical notes on the land surface modeling in the Tibetan Plateau

2009 ◽  
Vol 6 (1) ◽  
pp. 1291-1320 ◽  
Author(s):  
K. Yang ◽  
Y.-Y. Chen ◽  
J. Qin
Keyword(s):  
Soil Moisture ◽  
Tibetan Plateau ◽  
Land Surface ◽  
Soil Surface ◽  
Bare Soil ◽  
Heat Fluxes ◽  
The Tibetan Plateau ◽  
Central Plateau ◽  
Alpine Meadows ◽  
Common Land Model

Abstract. The Tibetan Plateau is a key region of land-atmosphere interactions, as it provides an elevated heat source to the middle-troposphere. The Plateau surfaces are typically characterized by alpine meadows and grasslands in the central and eastern part while by alpine deserts in the western part. This study evaluates performance of three state-of-the-art land surface models (LSMs) for the Plateau typical land surfaces. The LSMs of interest are SiB2 (the Simple Biosphere), CoLM (Common Land Model), and Noah. They are run with default parameters at typical alpine meadow sites in the central Plateau and typical alpine desert sites in the western Plateau. The recognized key processes and modeling issues are as follows. First, soil stratification is a typical phenomenon beneath the alpine meadows, with dense roots and soil organic matters within the topsoil, and it controls the profile of soil moisture in the central and eastern Plateau; all models significantly under-estimate the soil moisture within the topsoil. Second, a soil surface resistance controls the surface evaporation from the alpine deserts but it has not been reasonably modeled in LSMs; a new scheme is proposed to determine this resistance from soil water content. Third, an excess resistance controls sensible heat fluxes from dry bare-soil or sparsely vegetated surfaces, and all LSMs significantly under-predict the ground-air temperature difference in the daytime. A parameterization scheme for this resistance has been shown effective to remove this bias.

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.

scholarly journals Meta-analysis of relationships between environmental factors and aboveground biomass in the alpine grassland on the Tibetan Plateau

2013 ◽  
Vol 10 (3) ◽  
pp. 1707-1715 ◽  
Author(s):  
J. Sun ◽  
G. W. Cheng ◽  
W. P. Li
Keyword(s):  
Soil Moisture ◽  
Tibetan Plateau ◽  
Environmental Factors ◽  
Aboveground Biomass ◽  
Alpine Meadow ◽  
Meta Analysis ◽  
Alpine Grassland ◽  
Mean Annual Precipitation ◽  
The Tibetan Plateau ◽  
Alpine Steppe

Abstract. The Tibetan Plateau, known as the "world's third pole" for its extremely harsh and fragile ecological environment, has attracted great attention because of its sensitivity to global changes. Alpine grassland on the Tibetan Plateau has an important function in the global carbon cycle. Many studies have examined the effects of various environmental factors on biomass distribution. In this study, the relationships between the habitat parameters and the aboveground biomass (AGB) abundance on the Tibetan Plateau were examined through a meta-analysis of 110 field sites across the widely distributed alpine steppe and meadow. The obtained data were then analysed using the classification and regression tree model and the generalized additive model. The results showed that the AGB abundance in alpine steppe was positively correlated with six environmental factors, namely, soil organic carbon density of the top soil layer from 0 cm to 30 cm (SOC30 cm), longitude, mean annual precipitation (MAP), latitude, clay, and soil moisture. For the alpine meadow, five main factors were detected, namely, altitude, soil moisture, nitrogen, MAP, and mean annual temperature. The increased AGB abundance in the alpine steppe was associated with the increased SOC30 cm, MAP, and latitude, and the increased longitude resulted in decreased AGB abundance. For the alpine meadow, altitude and soil moisture showed strongly negative effects on AGB abundance, and soil nitrogen content was positively related to the AGB distribution across all examined sites. Our results suggest the combined effects of meteorological, topographic, and soil factors on the spatial patterns of AGB on the Tibetan Plateau.

Accelerated Changes of Environmental Conditions on the Tibetan Plateau Caused by Climate Change

2011 ◽  
Vol 24 (24) ◽  
pp. 6540-6550 ◽  
Author(s):  
Lei Zhong ◽  
Zhongbo Su ◽  
Yaoming Ma ◽  
Mhd. Suhyb Salama ◽  
José A. Sobrino
Keyword(s):  
Heat Flux ◽  
Tibetan Plateau ◽  
Air Temperature ◽  
Land Surface ◽  
Asian Monsoon ◽  
Sensible Heat Flux ◽  
Surface Air Temperature ◽  
The Tibetan Plateau ◽  
Sensible Heat ◽  
Land Surface Parameters

Abstract Variations of land surface parameters over the Tibetan Plateau have great importance on local energy and water cycles, the Asian monsoon, and climate change studies. In this paper, the NOAA/NASA Pathfinder Advanced Very High Resolution Radiometer (AVHRR) Land (PAL) dataset is used to retrieve the land surface temperature (LST), the normalized difference vegetation index (NDVI), and albedo, from 1982 to 2000. Simultaneously, meteorological parameters and land surface heat fluxes are acquired from the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) dataset and the Global Land Data Assimilation System (GLDAS), respectively. Results show that from 1982 to 2000 both the LST and the surface air temperature increased on the Tibetan Plateau (TP). The rate of increase of the LST was 0.26±0.16 K decade−1 and that of the surface air temperature was 0.29 ± 0.16 K decade−1, which exceeded the increase in the Northern Hemisphere (0.054 K decade−1). The plateau-wide annual mean precipitation increased at 2.54 mm decade−1, which indicates that the TP is becoming wetter. The 10-m wind speed decreased at about 0.05±0.03 m s−1 decade−1 from 1982 to 2000, which manifests a steady decline of the Asian monsoon wind. Due to the diminishing ground–air temperature gradient and subdued surface wind speed, the sensible heat flux showed a decline of 3.37 ± 2.19 W m−2 decade−1. The seasonal cycle of land surface parameters could clearly be linked to the patterns of the Asian monsoon. The spatial patterns of sensible heat flux, latent heat flux, and their variance could also be recognized.

Sign in / Sign up

Export Citation Format

Share Document