scholarly journals Contrasting Effects of Temperature and Precipitation on Vegetation Greenness along Elevation Gradients of the Tibetan Plateau

2020 ◽  
Vol 12 (17) ◽  
pp. 2751
Author(s):  
Yan Wang ◽  
Dailiang Peng ◽  
Miaogen Shen ◽  
Xiyan Xu ◽  
Xiaohua Yang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Global Climate ◽  
The Tibetan Plateau ◽  
Elevation Gradients ◽  
Vegetation Greenness ◽  
Temperature And Precipitation ◽  
Variation Rate ◽  
Effects Of Temperature

The Tibetan Plateau (TP) is one of the most sensitive regions to global climate warming, not only at the inter-annual time scale but also at the altitudinal scale. We aim to investigate the contrasting effects of temperature and precipitation on vegetation greenness at different altitudes across the TP. In this study, interannual and elevational characteristics of the Normalized Difference Vegetation Index (NDVI), temperature, and precipitation were examined during the growing season from 1982 to 2015. We compared the elevational movement rates of the isolines of NDVI, temperature, and precipitation, and the sensitivities of elevational NDVI changes to temperature and precipitation. The results show that from 1982 to 2015, the elevational variation rate of isolines for NDVI mismatched with that for temperature and precipitation. The elevational movements of NDVI isolines were mostly controlled by precipitation at elevations below 2400 m and by the temperature at elevations above 2400 m. Precipitation appears to plays a role similar to temperature, and even a more effective role than the temperature at low elevations, in controlling elevational vegetation greenness changes at both spatial and interannual scales in the TP. This study highlights the regulation of temperature and precipitation on vegetation ecosystems along elevation gradients over the whole TP under global warming conditions.

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

2016 ◽  
Vol 20 (8) ◽  
pp. 3167-3182 ◽  
Author(s):  
Jian Peng ◽  
Alexander Loew ◽  
Xuelong Chen ◽  
Yaoming Ma ◽  
Zhongbo Su
Keyword(s):  
Tibetan Plateau ◽  
Vegetation Index ◽  
Water Cycle ◽  
Global Climate ◽  
Spatial Scales ◽  
Accurate Estimation ◽  
The Tibetan Plateau ◽  
North West ◽  
Comparison Results ◽  
Normalised Difference Vegetation Index

Abstract. The Tibetan Plateau (TP) plays a major role in regional and global climate. The understanding of latent heat (LE) flux can help to better describe the complex mechanisms and interactions between land and atmosphere. Despite its importance, accurate estimation of evapotranspiration (ET) over the TP remains challenging. Satellite observations allow for ET estimation 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 are included for comparison. Results show that all products capture the seasonal variability well with minimum ET in the winter and maximum ET in the summer. Regarding the spatial pattern, the High resOlution Land Atmosphere 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 decreasing ET from the south-east to north-west over the TP. Further comparison against the LandFlux-EVAL over different sub-regions that are decided by different intervals of normalised difference vegetation index (NDVI), precipitation, and elevation reveals that HOLAPS agrees best with LandFlux-EVAL having the highest correlation coefficient (R) and the lowest root mean square difference (RMSD). These results indicate the potential for the application of the HOLAPS demonstrator dataset in understanding the land–atmosphere–biosphere interactions over the TP. In order to provide more accurate ET over the TP, model calibration, high accuracy forcing dataset, appropriate in situ measurements as well as other hydrological data such as runoff measurements are still needed.

scholarly journals Growing Season Precipitation Rather than Growing Season Length Predominates Maximum Normalized Difference Vegetation Index in Alpine Grasslands on the Tibetan Plateau

2020 ◽  
Vol 12 (3) ◽  
pp. 968
Author(s):  
Jiang Wei Wang ◽  
Meng Li ◽  
Guang Yu Zhang ◽  
Hao Rui Zhang ◽  
Cheng Qun Yu
Keyword(s):  
Tibetan Plateau ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Growing Season ◽  
The Tibetan Plateau ◽  
Season Length ◽  
Alpine Grasslands ◽  
Vegetation Productivity ◽  
Growing Season Length ◽  
Growing Season Precipitation

Precipitation and growing season length (GSL) are vital abiotic and biotic variables in controlling vegetation productivity in alpine regions. However, their relative effects on vegetation productivity have not been fully understood. In this study, we examined the responses of the maximum normalized difference vegetation index (NDVImax) to growing season precipitation (GSP) and GSL from 2000 to 2013 in 36 alpine grassland sites on the Tibetan Plateau. Our results indicated that NDVImax showed a positive relationship with prolonged GSL (R2 = 0.12) and GSP (R2 = 0.39). The linear slope of NDVImax increased with that of GSP rather than GSL. Therefore, GSP had a stronger effect on NDVImax than did GSL in alpine grasslands on the Tibetan Plateau.

scholarly journals Characteristics and Scenarios Projection of Climate Change on the Tibetan Plateau

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Zhenchun Hao ◽  
Qin Ju ◽  
Weijuan Jiang ◽  
Changjun Zhu
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Climate Models ◽  
Global Climate ◽  
Surface Air Temperature ◽  
Global Climate Models ◽  
The Tibetan Plateau ◽  
Intergovernmental Panel ◽  
Temperature And Precipitation ◽  
Ipcc Ar4

The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4) presents twenty-two global climate models (GCMs). In this paper, we evaluate the ability of 22 GCMs to reproduce temperature and precipitation over the Tibetan Plateau by comparing with ground observations for 1961~1900. The results suggest that all the GCMs underestimate surface air temperature and most models overestimate precipitation in most regions on the Tibetan Plateau. Only a few models (each 5 models for precipitation and temperature) appear roughly consistent with the observations in annual temperature and precipitation variations. Comparatively, GFCM21 and CGMR are able to better reproduce the observed annual temperature and precipitation variability over the Tibetan Plateau. Although the scenarios predicted by the GCMs vary greatly, all the models predict consistently increasing trends in temperature and precipitation in most regions in the Tibetan Plateau in the next 90 years. The results suggest that the temperature and precipitation will both increase in all three periods under different scenarios, with scenario A1 increasing the most and scenario A1B increasing the least.

scholarly journals Vegetation Change and Its Relationship with Climate Factors and Elevation on the Tibetan Plateau

2019 ◽  
Vol 16 (23) ◽  
pp. 4709 ◽  
Author(s):  
Yixin Zhang ◽  
Guoce Xu ◽  
Peng Li ◽  
Zhanbin Li ◽  
Yun Wang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Vegetation Change ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Climatic Factors ◽  
Sunshine Duration ◽  
The Tibetan Plateau ◽  
The North ◽  
Geographical Unit ◽  
Key Factor

As the “roof of the world”, the Tibetan Plateau (TP) is a unique geographical unit on Earth. In recent years, vegetation has gradually become a key factor reflecting the ecosystem since it is sensitive to ecological changes especially in arid and semi-arid areas. Based on the normalized difference vegetation index (NDVI) dataset of TP from 2000 to 2015, this study analyzed the characteristics of vegetation variation and the correlation between vegetation change and climatic factors at different time scales, based on a Mann–Kendall trend analyses, the Hurst exponent, and the Pettitt change-point test. The results showed that the vegetation fractional coverage (VFC) generally increased in the past 16 years, with 60.3% of the TP experiencing an increase, of which significant (p < 0.05) increases accounted for 28.79% and were mainly distributed in the north of the TP. Temperature had the largest response with the VFC on the seasonal scale. During the growing season, the correlation between precipitation and sunshine duration with VFC was high (p < 0.05). The change-points of the VFC were mainly distributed in the north of the TP during 2007–2009. Slope and elevation had an impact on the VFC; the areas with large vegetation change are mainly distributed in slopes <20° and elevation of 3000–5000 m. For elevation above 3000–4000 m, the response of the VFC to precipitation and temperature was the strongest. This study provided important information for ecological environment protection and ecosystem degradation on the Tibetan Plateau.

scholarly journals The Effect of Geographical and Climatic Factors on the Distribution of Phlebotomus papatasi (Diptera: Psychodidae) in Golestan Province, an Endemic Focus of Zoonotic Cutaneous Leishmaniasis in Iran, 2014

2021 ◽  
Author(s):  
Seyed Hamid Hosseini ◽  
Ehsan Allah-Kalteh ◽  
Aiuob Sofizadeh
Keyword(s):  
Cutaneous Leishmaniasis ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Climatic Factors ◽  
Global Climate ◽  
Phlebotomus Papatasi ◽  
Temperature And Precipitation ◽  
Zoonotic Cutaneous Leishmaniasis ◽  
Diurnal Range ◽  
Annual Range

Background: Phlebotomus papatasi is known as the main vector of zoonotic cutaneous leishmaniasis. This study aimed to investigate the effect of geographical and bioclimatic factors on the Ph. papatasi distribution. Methods: A total of 34 villages were selected, and sampling was performed three times using 120 sticky traps in each selected village. All the collected species were mounted and identified their species. The densities of Ph. papatasi were measured in all the villages and entered into ArcMap as a point layer. The required bioclimatic and environmental vari- ables were extracted from the global climate database and The normalized difference vegetation index was obtained from the MODIS satellite imagery, also, all variables entered into ArcMap as raster layers, so The numerical value of each independent variable in the cell where the selected village is located in this, was extracted using spatial analyst tools and the value to point submenu. All the data were finally entered into IBM SPSS, and the relationship was exam- ined between the number of collected Ph. papatasi and the independent variables using Spearman's correlation test. Results: A total of 1773 specimens of Ph. papatasi were collected. The findings of this study showed that max tem­perature of warmest month, temperature annual range, temperature seasonality, mean diurnal range, precipitation sea­sonality, mean temperature of driest and warmest quarter were positively associated with the density of Ph. papatasi. Conclusion: Air temperature and precipitation were shown as the most significant factors in the distribution of Ph. pa­patasi.

scholarly journals Local Climatic Factors Mediated Impacts of Large-Scale Climate Oscillations on the Growth of Vegetation Across the Tibetan Plateau

2021 ◽  
Vol 9 ◽  
Author(s):  
Lei Zhang ◽  
Miaogen Shen ◽  
Chunming Shi ◽  
Fangzhong Shi ◽  
Nan Jiang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Large Scale ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Climatic Factors ◽  
Temporal Trends ◽  
Atlantic Multidecadal Oscillation ◽  
The Tibetan Plateau ◽  
Climate Oscillations ◽  
South Central

Large-scale climate oscillations, particularly the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO), have widespread influences on climate systems across the Tibetan Plateau (TP). It is understudied how the temporal changes in AMO and PDO affected growth of vegetation through modifying the local climatic factors in different areas across the TP. We used the AMO and PDO indices, gridded growing season mean temperature (TGS), cumulative precipitation (PGS), and normalized difference vegetation index (NDVIGS) data from 1982 to 2015 to investigate the temporal trends of these variables and the correlations of the TGS and PGS with each of the AMO and PDO indices as well as their correlations with the NDVIGS. The results showed that the warming of the TGS over the TP and the increases of the PGS in western, central, and northeastern areas of the TP may have been related to an increase of the AMO index and a decrease of the PDO index. Combining those relationships with the spatial patterns of the TGS-NDVIGS and PGS-NDVIGS correlations suggested that the changes of the AMO and PDO may have indirectly increased the NDVIGS in the central and northeastern areas of the TP by increasing TGS and PGS, in most parts of the southwestern TP by increasing PGS, and in the eastern and south-central regions of the TP by increasing TGS. In contrast, the decrease of the NDVIGS in some areas of the southeastern and southwestern TP may have been associated with a negative effect of warming as a result of changes in the AMO and PDO. These results highlight the indirect impacts of changes in large-scale climate oscillations on the growth of vegetation through modification of local climatic factors across the TP, and they suggest the substantial spatial heterogeneity of these impacts largely depends on the responses of vegetation to local climatic factors.

scholarly journals Assessment of Vegetation Phenological Extractions Derived From Three Satellite-Derived Vegetation Indices Based on Different Extraction Algorithms Over the Tibetan Plateau

2021 ◽  
Vol 9 ◽  
Author(s):  
Chunchun An ◽  
Zhi Dong ◽  
Hongli Li ◽  
Wentai Zhao ◽  
Hailiang Chen
Keyword(s):  
Remote Sensing ◽  
Tibetan Plateau ◽  
Large Scale ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Accuracy Assessment ◽  
Vegetation Indices ◽  
The Tibetan Plateau ◽  
Phenological Metrics ◽  
The Impact

Remote sensing phenology retrieval can remedy the deficiencies in field investigations and has the advantage of catching the continuous characteristics of phenology on a large scale. However, there are some discrepancies in the results of remote sensing phenological metrics derived from different vegetation indices based on different extraction algorithms, and there are few studies that evaluate the impact of different vegetation indices on phenological metrics extraction. In this study, three satellite-derived vegetation indices (enhanced vegetation index, EVI; normalized difference vegetation index, NDVI; and normalized difference phenology index, NDPI; calculated using surface reflectance data from MOD09A1) and two algorithms were used to detect the start and end of growing season (SOS and EOS, respectively) in the Tibetan Plateau (TP). Then, the retrieved SOS and EOS were evaluated from different aspects. Results showed that the missing rates of both SOS and EOS based on the Seasonal Trend Decomposition by LOESS (STL) trendline crossing method were higher than those based on the seasonal amplitude method (SA), and the missing rate varied using different vegetation indices among different vegetation types. Also, the temporal and spatial stabilities of phenological metrics based on SA using EVI or NDPI were more stable than those from others. The accuracy assessment based on ground observations showed that phenological metrics based on SA had better agreements with ground observations than those based on STL, and EVI or NDVI may be more appropriate for monitoring SOS than NDPI in the TP, while EOS from NDPI had better agreements with ground-observed EOS. Besides, the phenological metrics over the complex terrain also presented worse performances than those over the flat terrain. Our findings suggest that previous results of inter-annual variability of phenology from a single data or method should be treated with caution.

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