Abstract
Due to global warming, drought events have become more frequent, which resulted in aggravated crop failures, food shortage, larger and more energetic wildfires, and have seriously affected socio-economic development and agricultural production. In this study, a global long-term (1981–2021), high-resolution (4 km) improved vegetation health index (VHI) dataset integrating climate, vegetation and soil moisture was developed. Based on drought records from the Emergency Event Database, we compared the detection efficiency of the VHI before and after its improvement in the occurrence and scope of observed drought events. The global drought detection efficiency of the improved high-resolution VHI dataset reached values as high as 85%, which is 14% higher than the original VHI dataset. The improved VHI dataset was also more sensitive to mild droughts and more accurate regarding the extent of droughts. This improved dataset can play an important role in long-term drought monitoring but also has the potential to assess the impact of drought on the agricultural, forestry, ecological and environmental sectors.
Similar content being viewed by others
Background & Summary
Drought is a complex phenomenon1, and can trigger crop failures, food shortages, famines, epidemics, and even mass migration2,3. Severe drought events were responsible for widespread negative impacts on natural and socioeconomic systems4,5. Therefore, it is urgent to improve our understanding of the spatiotemporal characteristics and the evolutionary trends of droughts6,7. This would provide a basis for quantifying drought impacts and the social, economic and natural ecological responses to droughts across regions and times8.
According to different subjects, drought usually presents four processes or types: meteorological (insufficient precipitation), agricultural, also called vegetation drought (insufficient soil moisture), hydrological (insufficient runoff and/or groundwater), and socioeconomic (social response to water supply and demand)9. Among these, vegetation drought is highly correlated with food production, and the extent of vegetation drought have been increasing10,11.The global average harvested area has decreased by 4.1% during droughts from 1964–200712. The number and duration of severe drought events in the world are expected to maintain its growth in the future13,14. An efficient technique to detect vegetation drought events and monitor the potential risk of droughts in the long term is thus urgently needed15,16. This may be seen as a key asset to help policymakers implement timely mitigation and adaptation strategies17.
Traditional meteorological drought index has been widely used for vegetation drought assessment18,19,20. For example, the self-calibrating Palmer drought severity index (sc-PDSI)21 significantly improves spatial homogeneity, taking into account soil moisture conditions. Four values related to the soil moisture are computed along with their complementary potential values. These eight values are evapotranspiration (ET), recharge (R), runoff (RO), loss (L), potential evapotranspiration (PE), potential recharge (PR), potential runoff (PRO), and potential loss (PL). The PDSI depends on a two-stage “bucket” model of the soil22. The top layer of soil is assumed to hold one inch of moisture. The amount of moisture that can be held by the rest of the underlying soil is a location-dependent value, which must be provided as an input parameter to the program. The sc-PDSI automatically calibrates the behavior of the index at any location by replacing empirical constants in the index computation with dynamically calculated values21. Compared with other meteorological drought indices [such as the standard precipitation index (SPI) and the standardized precipitation-evapotranspiration index (SPEI)], the sc-PDSI has a higher correlation with vegetation drought23. However, these indices still face problems such as inaccurate station observation and delayed data collection7,24, and do not consider either the impact of water and heat stress on vegetation growth or do not fully consider land cover and vegetation information of the underlying surface25. Therefore, the traditional meteorological drought index is not suitable for direct use in vegetation drought research. But using it as an auxiliary information supplement tool and combining it with other relevant technologies can help us better understand and study vegetation drought. Currently, satellite data are widely used for drought assessment, because of its ability to identify drought conditions on different underlying surfaces26. Remotely sensed drought monitoring has advantages such as being suitable for large-scale drought monitoring27, having a powerful real-time update function28,29, and high accuracy, as well as unmatched cost-effectiveness when compared to other methods30,31. Therefore, the combination of satellite remote sensing technology and traditional drought index is a very promising drought assessment method.
The vegetation health index (VHI) is one of the most popular remote sensing drought monitoring indices32,33,34,35. VHI is composed by two terms: the vegetation condition index (VCI) and the thermal condition index (TCI). VHI considers local biophysical and climatic conditions, and can be used for actual plant drought monitoring in various agrometeorological regions36. The basic principles of VHI are as follows: (1) a low normalized differences vegetation index (NDVI) and high land surface temperature (LST) suggest poor vegetation health37,38; and (2) the contributions of VCI and TCI to VHI are assumed to be equal, since there are no data on the relative contributions of other conditions to vegetation health35. However, the contributions of TCI and VCI to VHI depend on climatic and other environmental factor39. Indeed, environmental conditions in different regions are usually different, which implies that giving equal weights to VCI and TCI may reduce the application prospects of the VHI, increasing the uncertainty in drought detection33. Therefore, evaluating the contributions of VCI and TCI to VHI while considering the underlying surface and hydrothermal conditions is a key issue that needs to be addressed. Bento, et al.39 used SPEI index combined with Pearson correlation analysis to evaluate the contribution of TCI and VCI to VHI in arid regions, while Zeng, et al.23 compared SPEI and sc-PDSI as a control drought index to evaluate the contribution of TCI and VCI to VHI.
The purpose of this study is to produce a global, long-term (1981–2021), high-spatial-resolution, improved vegetation drought detection dataset and a reference parameter dataset for calculating the improved VHI for different regions. Here, we supplemented meteorological and soil moisture information on the basis of the VHI of the original algorithm and used the sc-PDSI as the control drought index, combined with the Pearson correlation analysis method, to evaluate the best contributions of VCI and TCI to VHI in different regions. Then, we generated a global long-term dataset for detecting vegetation drought. We also used drought event records from the Emergency Events Database (EM-DAT) to assess the drought detection ability of our improved VHI dataset. The developed global vegetation drought dataset has the potential to monitor and assess drought and its impact on the agricultural, forestry, ecological, and environmental sectors.
Data and Methods
Dataset coverage
Dataset coverage ranges from approximately from −50°S to 70°N and from −180°W to 180°E. Antarctica, the high latitude regions of the Northern Hemisphere (due to the lack of VCI and TCI data in this area), and the Sahara Desert region in Africa (due to the lack of sc-PDSI in this area) were excluded from the study area. These areas have little vegetation or extremely low vegetation coverage, so this part is usually excluded when studying vegetation drought40,41,42,43, and these areas are not considered in this dataset. The colors on Figure 1 represent the number of drought events since 1900. Figure 1 also shows information on the change in global annual mean temperature (Fig. 1b), change in global annual precipitation (Fig. 1c), and the change in global annual number of droughts (Fig. 1d). Since the 20th century, global temperatures have substantially increased, and precipitation also showed a positive trend, but with high fluctuations and large uncertainties. Significantly higher temperatures and greater uncertainty in precipitation could dramatically increase drought risk. According to statistics, drought events have been on the rise since 1900 (p < 0.001), and especially since the 1980s.
Data sources
Global VCI and TCI data were downloaded from the National Oceanic and Atmospheric Administration (NOAA) Center for Satellite Application and Research (STAR) (https://www.star.nesdis.noaa.gov/smcd/emb/vci/VH/vh_ftp.php), with a spatial resolution of 4 km, a weekly temporal resolution, and a time span ranging from 1981 to 2021. We organized the data in annual values through the arithmetic mean, and processed the background value (−9999) as a null value through the spatial masking technique to facilitate subsequent spatial and related statistical analyses.
Global sc-PDSI data were downloaded from the Climate Research Unit (CRU), with a spatial resolution of 0.5°, a monthly temporal resolution, and a time span ranging from 1901 to 2020 (https://crudata.uea.ac.uk/cru/data//drought/#global)44,45. We organized the data in annual data by the arithmetic mean, then resampled to 4 km by the nearest neighbor method to match the VCI and TCI data. Resampling the 0.5 ° sc-PDSI to 4-km will not lose the information it contains, making the results acceptable. However, the use of sc-PDSI with higher spatial resolution may provide more information on hydrothermal and soil characteristics and may reduce the uncertainty of results.
Data on global drought events from 1900 to 2021 were obtained from the EM-DAT (https://public.emdat.be/)46. After filtering and eliminating invalid data, a total of 592 valid records from 1981 to 2021 were selected. We have uploaded the drought event data records for verification to figshare, which can be obtained from https://doi.org/10.6084/m9.figshare.19811854.v547.
Annual VHI calculation
According to Kogan35, the VCI for each pixel and period in a given year was calculated as follows:
where NDVI is the value of a given pixel and period, and NDVIMIN and NDVIMAX are the minimum and maximum values of NDVI for all pixels and periods, respectively. Equation (2) was used to calculate the TCI:
where LST is the value of a given pixel and period. LSTMIN and LSTMAX are the minimum and maximum values of LST for all pixels and periods, respectively. The VHI represents the overall health of the vegetation and is used to identify drought48. It is calculated by combining the VCI and the TCI as follows:
where a determines the contributions of VCI and TCI to VHI, which varies depending on the environment of the study area33. The original VHI (VHIori) assumes equal contributions from water demand (here, a proxy of NDVI) and temperature during plant growth, and the coefficient a is assigned the value of 0.5. Following other studies35,49,50, we classified drought levels on the basis of the VHI (Table 1):
Improvement of the VHI algorithm
We chose the meteorological drought index sc-PDSI, which considers hydrothermal conditions and soil moisture, as the control drought index, and combined it with Pearson correlation analysis to evaluate the contribution of VCI and TCI on a grid by grid basis, thereby obtaining an improved VHI index. To improve VHI, the following steps are taken: (1) The parameter a was set to vary in steps of 0.02, starting from 0.02 and gradually increasing to 0.98 (49 values in total). The VHI was then calculated in each step for each year from 1981 to 2021 based on different a values. The specific formula is as follows:
Where VHIi,t,a represents the VHI when the VCI contribution of the ith pixel is a at time t. VCIi,t represents the VCI of pixel i at time t, and TCIi,t represents the TCI of pixel i at time t.
(2) The Pearson correlation was then used to evaluate the correlation between sc-PDSI and the VHI calculated in each iterative step of contribution values a pixel by pixel. The sc-PDSI based on the water balance theory fully considers meteorological factors and soil moisture conditions, suitable for improving the VHI23. The Pearson correlation coefficient is calculated as follows:
Where Ri represents the correlation coefficient between VHI and sc-PDSI of pixel i, xi represents the VHI of pixel i, \(\overline{{x}_{i}}\) represents the average value of VHI of pixel i from 1981 to 2021, yi represents the sc-PDSI of pixel i, and \(\overline{{y}_{i}}\) denotes the mean value of sc-PDSI for pixel i from 1981 to 2021. The range of |R| is 0 to 1.
(3) After obtaining the spatial correlation coefficient map of sc-PDSI and VHI calculated with different a values, the optimal contribution value a was estimated pixel by pixel according to the following formula:
Where ai,opt represents the best contribution value a of VCI to VHI at pixel i, and (1-ai,opt) represents the best contribution value of TCI to VHI. R is the correlation coefficient between VHI and sc-PDSI, VHIi,a is the VHI of pixel i when the contribution value of VCI is a, and scPDSIi is the sc-PDSI of the ith pixel. By comparing the correlation coefficients between sc-PDSI and VHI calculated for the 49 values of a pixel by pixel, the a value of the largest correlation coefficient was selected as the best contribution value a of the VCI to VHI of this pixel.
(4) Finally, according to the best contribution value a and the calculation formula of VHI, the improved VHI, namely VHIopt, is obtained. The specific formula is as follows:
Where VHIi,t,opt represents the VHI obtained by the best contribution value a of the ith pixel at time t, and ai,opt represents the best contribution value of the VCI to the VHI of the ith pixel. The algorithms used to improve the VHI index have been uploaded to Github and can be obtained from https://github.com/BNUJingyuZeng/A-new-global-VHI-dataset-code. A general overview of the working scheme is given in Fig. 2.
We compared the scatterplots and linear regression fittings of sc-PDSI and VHI before and after the improvement using detrending. The method of detrending is as follows:
Where VHIdei,t represents the VHI for the ith pixel at time t after detrending, VHIi,t represents the VHI for ith pixel at time t before detrending, and VHIi,t−1 represents the VHI of pixel ith at time t-1 before detrending.
Evaluation of the drought detection efficiency
Drought detection efficiency of the VHI dataset was evaluated before and after the improvement, based on drought event records in the EM-DAT. The specific formula is as follows:
DTE is the drought detection efficiency, S is the score, and TDE is the total number of drought events. The score is evaluated according to the following principles. The VHI-based vegetation drought rating scale threshold is selected as 40. When the VHI is lower than 40, this means dryness (Table 1) - let’s assume drought, and if it is higher than 40, this means normal or wet conditions (Table 1). Given the occurrence time and location of the drought event, VHIs before and after the improvement are compared one by one. When the number of pixels detected by drought accounts for more than 80% of the number of pixels in the area where the drought event occurred, the score is 1, when the number of pixels detected by drought accounts for more than 40% of the number of pixels in the area where the drought event occurred, the score is 0.5, when the number of pixels detected by drought accounts for less than 40% of the number of pixels in the area where the drought event occurred, the score is 0.
Statistical methods
The Mann–Kendell (MK) method is widely used in meteorology, ecology, environmental research51,52,53,54. It is a nonparametric test method55,56. We used the Theil-sen trend analysis and the MK trend detection methods to study the temporal and spatial trends of global vegetation drought.
Data Records
Extent, projection, resolution and data format
The VHIopt dataset covers most of the world’s land areas except Antarctica, with an approximate range of −50°S to 70°N and −180°W to 180°E. The data projection is GCS_WGS_1984. This dataset is available as a 4-km GeoTIFF accessible from a data repository on figshare (https://doi.org/10.6084/m9.figshare.19811854.v5)47. For each year’s VHIopt image, the globe is divided into 10000 × 3616 1-km × 1-km grid cells. In addition to annual data, we also provide monthly data, which can be used to analyze vegetation drought and related research from the seasonal scale analysis, and also provide a list to explain which months’ data are missing due to the lack of data, and how to combine weekly data into monthly data. We also provide a global best contribution parameter dataset based on the 1981–2021 VHI dataset, i.e., the aopt parameter file. The file’s extent, projection, spatial resolution and data format are consistent with the VHIopt dataset. The annual VHIopt dataset does not exceed 12 GB (about 3 GB for the compressed download). To preserve as much information as possible, we kept the value of each cell to six decimal places. Missing data are represented by “Nodata”.
Data naming and availability
The global 1981–2021 VHIopt dataset is named “VHIopt_year.tif”, where year corresponds to the year of the data, with a total of 41 files. The VHIopt data of the corresponding year is calculated from annual VCI and TCI data of the year with the best contribution parameter graph from the aopt file. The parameter file of the global best contribution value a is directly named aopt, which can be used to calculate VHI data from small to macro scales and from daily to seasonal scales.
Technical Validation
Drought detection efficiency of the VHIopt dataset
The best contribution value aopt is less than 0.5 in most regions of the world. The proportion of regions dominated by TCI reaching 70% and the proportion of regions dominated by VCI of ~28% (Fig. 3). VHIopt is affected by TCI and VCI differently in different regions. Most of Africa is dominated by VCI, while South America, Australia, and regions north of 30° latitude are dominated by TCI. This is especially visible in Europe, where TCI-dominated regions are concentrated and contiguous, with aopt values generally lower than 0.3. Overall, an abnormally high surface temperature is the main driving factor affecting vegetation drought.
The coefficient of determination of the VHI before and after the improvement and the sc-PDSI were compared, as well as the performance before and after detrending (Fig. 4). The coefficient of determination of VHIopt and sc-PDSI (Fig. 4a,c) agree better compared with VHIori (Fig. 4b,d). The correlation between VHIopt and sc-PDSI was 0.13 higher than that between VHIori and sc-PDSI (i.e., 0.51 and 0.38, respectively) after excluding time-dependent trends (Fig. 4a,b), which implies an improvement of 34% in correlation. The correlation between VHIopt and sc-PDSI without detrending was 0.04 higher than that between VHIori and sc-PDSI (i.e., 0.41 and 0.37, respectively; Fig. 4c,d), i.e., an improvement of 10%. The improved VHI dataset can better capture soil moisture anomalies and heat stress levels than the original VHI dataset, thus improving the detection of vegetation drought.
Based on global drought events recorded in the EM-DAT, we compared the ability of VHIopt and VHIori to detect drought in a year-by-year globally (Fig. 5). The ability of VHIopt to detect drought was higher than that of VHIori, with drought detection efficiencies about 84.97% and 70.69%, respectively. The period from 1997 to 2002 was a period of frequent drought events in the world. The year 2001 experienced the largest number of drought events, i.e., 27. Drought events have declined in recent years.
The same analysis was repeated but by continent (Fig. 6). The drought detection efficiency of VHIopt was higher than that of VHIori in all continents except Oceania. The drought event frequency from high to low was 251, 143, 84, 56, 42, and 16 for Africa, Asia, North America, South America, Europe, and Oceania, respectively. The VHIopt drought detection efficiency was highest in North America at 90% and lowest in Oceania at 81%. The VHIori drought detection efficiency is the highest in Oceania at 84% and lowest in Asia at 62%. The drought detection efficiencies of VHIopt and VHIori in Oceania were not much different, related to the small number of drought events occurring there. In addition, in many areas of Oceania, drought occurs on small islands, which are affected by the resolution of the data. In Australia, the drought detection efficiency of VHIopt was still higher than that of VHIori.
In general, compared with the original VHIori, our improved VHIopt dataset has an improved drought detection efficiency in all continents. It has broad application prospects for the detection and long-term monitoring of vegetation drought.
Spatial differences between VHIopt and VHIori
Based on the estimated global best contribution value aopt, we analyzed global annual VHIopt and VHIori from 1981 to 2021 and compared their spatial patterns (Fig. 7). A relatively low degree of global vegetation drought is seen, with normal to good levels in most areas over the past 40 years, especially near the Equator, eastern North America, and southeastern South America. Clear differences between the two indices are seen (Fig. 7c). VHIopt effectively detected mild vegetation drought, while VHIori underestimated the occurrence and impact range of mild vegetative drought. VHIori was significantly higher than VHIopt along the western coasts of North America, Europe, South America, and southwest Asia.
We also compared VHIopt and VHIori globally and by continents (Fig. 7b,d). VHIori is higher than VHIopt in 66.5% of the cases. Oceania was the region with the lowest level of vegetation health in the world, as well as the region with the greatest variability, the highest uncertainty, and a higher risk of vegetation health. The vegetation health level in North America was the highest in the world, with average values of 49.02 and 47.98 for VHIori and VHIopt, respectively, which are significantly different from Oceania (p < 0.05).
We further zoomed in on the above regions to compare spatial differences between VHIopt and VHIori (Fig. 8). In South America and Europe, VHIopt values below 40 indicates that this index effectively detected vegetation drought, especially in specific years. VHIori values above 40 indicate normal conditions. VHIopt was more sensitive to mild vegetation drought than VHIori, illustrating its better ability to detect mild drought. VHIopt also improved the ability to assess the occurrence range of vegetation drought compared with VHIori. For example, in the western United States and southwestern Asia, the spatial range of VHIori values below 40 was smaller than that of VHIopt, and there was an overly optimistic estimate of vegetation health. Furthermore, VHIopt also more effectively assessed the extent of vegetation drought in specific years. In general, VHIopt has clear advantages over VHIori in both drought detection efficiency and drought occurrence range identification.
Trends seen in the global VHIopt dataset
We analyzed global and continental trends in VHIopt and VHIori from 1981 to 2021 (Fig. 9). Results show that over the past 40 years, the VHIopt in Europe, South America, and Oceania has decreased significantly by about 0.14, 0.31, and 0.35 per year, respectively. There was no significant change in Asia, North America, and Africa. Globally, VHIopt showed an overall downward trend, with an average annual decrease of 0.16. VHIori showed a significant increase in Europe, with an annual increase of about 0.2, and a significant decline in Africa, with a decrease of about 0.24 per year. A further analysis showed that South America was the region with the most obvious downward trend in VHIopt (R2 = 0.54). From 1981 to 2005, inter-annual differences in Asia were relatively large, and from 2005 to 2021, changes in VHIopt and VHIori gradually stabilized. This suggests that the future uncertainty of vegetation health in Asia may be less than in other regions.
Since VHIopt has noticeable advantages over VHIori in both drought detection efficiency and drought occurrence range identification, we used the VHIopt dataset to evaluate the changing trend of global vegetation drought to identify hot spots where vegetation drought may be further aggravated in the future and areas with improved vegetation health (Fig. 9). Results show that the spatial heterogeneity of global vegetation drought changes may be high in the future. The western United States, South America, central and southern Australia, and southwestern Asia are regions where VHIopt will decreases. On the other hand, central Africa, India, southern China, North America, and high-latitude parts of Asia are areas where vegetation droughts will be alleviated and vegetation health levels will improve. These changes have passed the significance assessment in the MK trend test. In the context of climate change, the changes in vegetation drought in areas where VHIopt has declined are subject to large uncertainties and required more attention.
Usage Notes
We produced a long-term (1981–2021) high-spatial-resolution (4 km) improved vegetation drought detection dataset and the best contribution parameter dataset that can be used to calculate improved VHIs in different regions. We also evaluated the efficiency of the VHIopt dataset to detect drought and the spatial pattern and changing trends of global vegetation drought to improve our techniques for long-term monitoring of vegetation drought. Based on the best global contribution parameter dataset, VHIopt data in different regions can be calculated for performing drought assessment and studying food production and vegetation carbon sinks.
The data set can help people to carry out drought assessment more conveniently and efficiently, but there are areas where improvements are needed. First, the spatial resolution of the data may have an impacts on findings57. Using higher-spatial-resolution remote sensing products and sc-PDSI data will help further improve the detection efficiency of vegetation drought. Second, increased human activities may complicate changes in vegetation aridity25. Human interventions may have more complex impacts on vegetation health, requiring further research58.
Our research was conducted on a global scale, providing a tool aimed at understanding global and regional vegetation drought characteristics. This dataset greatly improves the ability of VHI to detect vegetation drought, and can help people better understand the impact of temperature on vegetation drought in different regions. This research is also conducive to the effective implementation of vegetation drought resistance ecological engineering, and helps local governments and farmers reduce the losses caused by vegetation drought. The global vegetation drought dataset developed here also has the potential to be used to monitor and assess drought and its impact on the agricultural, forestry, ecological, and environmental sectors.
Code availability
All calculations of a global long term (1981–2021), high resolution (4 km) improved vegetation health index (VHI) dataset are based on MATLAB, and relevant step codes can be obtained from Github: https://github.com/BNUJingyuZeng/A-new-global-VHI-dataset-code.git.
References
Van Loon, A. F. Hydrological drought explained. Wiley Interdisciplinary Reviews-Water 2, 359–392, https://doi.org/10.1002/wat2.1085 (2015).
Hameed, M., Ahmadalipour, A. & Moradkhani, H. Drought and food security in the middle east: An analytical framework. Agricultural and Forest Meteorology 281, 107816, https://doi.org/10.1016/j.agrformet.2019.107816 (2020).
Kogan, F., Guo, W. & Yang, W. Z. Drought and food security prediction from NOAA new generation of operational satellites. Geomatics Natural Hazards & Risk 10, 651–666, https://doi.org/10.1080/19475705.2018.1541257 (2019).
Dadson, S. J., Lopez, H. P., Peng, J. & Vora, S. in Water Science, Policy, and Management 11–28 (2019).
Marvel, K. et al. Twentieth-century hydroclimate changes consistent with human influence. Nature 569, 59–65, https://doi.org/10.1038/s41586-019-1149-8 (2019).
Bento, V. A., Russo, A., Vieira, I. & Gouveia, C. M. Identification of forest vulnerability to droughts in the Iberian Peninsula. Theoretical and Applied Climatology 152, 559–579, https://doi.org/10.1007/s00704-023-04427-y (2023).
Zhang, R. et al. The first high spatial resolution multi-scale daily SPI and SPEI raster dataset for drought monitoring and evaluating over China from 1979 to 2018. Big Earth Data, 1–26, https://doi.org/10.1080/20964471.2022.2148331 (2023).
AghaKouchak, A. et al. Remote sensing of drought: Progress, challenges and opportunities. Reviews of Geophysics 53, 452–480, https://doi.org/10.1002/2014rg000456 (2015).
AghaKouchak, A. A multivariate approach for persistence-based drought prediction: Application to the 2010–2011 East Africa drought. Journal of Hydrology 526, 127–135, https://doi.org/10.1016/j.jhydrol.2014.09.063 (2015).
Wu, X. et al. The Effect of Drought on Vegetation Gross Primary Productivity under Different Vegetation Types across China from 2001 to 2020. Remote Sensing 14, 4658 (2022).
Wu, Z. et al. Recent changes in the drought of China from 1960 to 2014. International Journal of Climatology 40, 3281–3296, https://doi.org/10.1002/joc.6397 (2020).
Lesk, C., Rowhani, P. & Ramankutty, N. Influence of extreme weather disasters on global crop production. Nature 529, 84–87, https://doi.org/10.1038/nature16467 (2016).
Wang, Q. et al. Temporal-spatial characteristics of severe drought events and their impact on agriculture on a global scale. Quaternary International 349, 10–21, https://doi.org/10.1016/j.quaint.2014.06.021 (2014).
Zhang, Z. et al. Spatial pattern and decadal change of agro-meteorological disasters in the main wheat production area of China during 1991–2009. Journal of Geographical Sciences 24, 387–396, https://doi.org/10.1007/s11442-014-1095-1 (2014).
He, B., Huang, L. & Wang, Q. Precipitation deficits increase high diurnal temperature range extremes. Scientific Reports 5, 12004, https://doi.org/10.1038/srep12004 (2015).
He, B., Wang, H. L., Wang, Q. F. & Di, Z. H. A quantitative assessment of the relationship between precipitation deficits and air temperature variations. Journal of Geophysical Research: Atmospheres 120, 5951–5961, https://doi.org/10.1002/2015JD023463 (2015).
Johansson, R., Luebehusen, E., Morris, B., Shannon, H. & Meyer, S. Monitoring the impacts of weather and climate extremes on global agricultural production. Weather and Climate Extremes 10, 65–71, https://doi.org/10.1016/j.wace.2015.11.003 (2015).
Wang, Q. et al. A multi-scale daily SPEI dataset for drought characterization at observation stations over mainland China from 1961 to 2018. Earth Syst. Sci. Data 13, 331–341, https://doi.org/10.5194/essd-13-331-2021 (2021).
Wang, Q. et al. An improved daily standardized precipitation index dataset for mainland China from 1961 to 2018. Scientific Data 9, 124, https://doi.org/10.1038/s41597-022-01201-z (2022).
Zhang, R. et al. Investigating the effect of improved drought events extraction method on spatiotemporal characteristics of drought. Theoretical and Applied Climatology 147, 395–408, https://doi.org/10.1007/s00704-021-03838-z (2022).
Wells, N., Goddard, S. & Hayes, M. J. A self-calibrating Palmer Drought Severity Index. Journal of Climate 17, 2335–2351, 10.1175/1520-0442(2004)017<2335:aspdsi>2.0.co;2 (2004).
Palmer, W. C. in U.S. Weather Bureau, Res. Pap. No. 45 58–58 (1965).
Zeng, J. et al. Improving the drought monitoring capability of VHI at the global scale via ensemble indices for various vegetation types from 2001 to 2018. Weather and Climate Extremes 35, 100412, https://doi.org/10.1016/j.wace.2022.100412 (2022).
Wang, Q. et al. The alleviating trend of drought in the Huang-Huai-Hai Plain of China based on the daily SPEI. International Journal of Climatology 35, 3760–3769, https://doi.org/10.1002/joc.4244 (2015).
Zeng, J. et al. Drought frequency characteristics of China, 1981–2019, based on the vegetation health index. Climate Research 81, 131–147, https://doi.org/10.3354/cr01616 (2020).
Wu, Z., Yu, L., Zhang, X., Du, Z. & Zhang, H. Satellite-based large-scale vegetation dynamics in ecological restoration programmes of Northern China. International Journal of Remote Sensing 40, 2296–2312, https://doi.org/10.1080/01431161.2018.1519286 (2019).
Leng, S. et al. Assessing the Impact of Extreme Droughts on Dryland Vegetation by Multi-Satellite Solar-Induced Chlorophyll Fluorescence. Remote Sensing 14, 1581 (2022).
Zhang, R., Qi, J., Leng, S. & Wang, Q. Long-Term Vegetation Phenology Changes and Responses to Preseason Temperature and Precipitation in Northern China. Remote Sensing 14, 1396 (2022).
Leng, S. et al. Spatiotemporal Variations of Dryland Vegetation Phenology Revealed by Satellite-Observed Fluorescence and Greenness across the North Australian Tropical Transect. Remote Sensing 14, 2985 (2022).
Tang, J. et al. A modified flexible spatiotemporal data fusion model. Frontiers of Earth Science 14, 601–614, https://doi.org/10.1007/s11707-019-0800-x (2020).
Ezzine, H., Bouziane, A. & Ouazar, D. Seasonal comparisons of meteorological and agricultural drought indices in Morocco using open short time-series data. International Journal of Applied Earth Observation and Geoinformation 26, 36–48, https://doi.org/10.1016/j.jag.2013.05.005 (2014).
Li, Y., Strapasson, A. & Rojas, O. Assessment of El Niño and La Niña impacts on China: Enhancing the Early Warning System on Food and Agriculture. Weather and Climate Extremes 27, 100208, https://doi.org/10.1016/j.wace.2019.100208 (2020).
Bento, V. A., Gouveia, C. M., DaCamara, C. C. & Trigo, I. F. A climatological assessment of drought impact on vegetation health index. Agricultural and Forest Meteorology 259, 286–295, https://doi.org/10.1016/j.agrformet.2018.05.014 (2018).
Kogan, F. N. in Natural Hazards: Monitoring and Assessment Using Remote Sensing Technique Vol. 15 Advances in Space Research-Series (eds Singh, R. P. & Furrer, R.) 91–100 (1995).
Kogan, F. N. Global drought watch from space. Bulletin of the American Meteorological Society 78, 621–636, 10.1175/1520-0477(1997)078<0621:gdwfs>2.0.co;2 (1997).
Bhuiyan, C., Singh, R. P. & Kogan, F. N. Monitoring drought dynamics in the Aravalli region (India) using different indices based on ground and remote sensing data. International Journal of Applied Earth Observation and Geoinformation 8, 289–302, https://doi.org/10.1016/j.jag.2006.03.002 (2006).
Tang, J. et al. Self-adapting extraction of cropland phenological transitions of rotation agroecosystems using dynamically fused NDVI images. International Journal of Biometeorology 64, 1273–1283, https://doi.org/10.1007/s00484-020-01904-1 (2020).
Yousef, F., Gebremichael, M., Ghebremichael, L. & Perine, J. Remote-sensing Based Assessment of Long-term Riparian Vegetation Health in Proximity to Agricultural Lands with Herbicide Use History. Integrated Environmental Assessment and Management 15, 528–543, https://doi.org/10.1002/ieam.4144 (2019).
Bento, V. A., Gouveia, C. M., DaCamara, C. C., Libonati, R. & Trigo, I. F. The roles of NDVI and Land Surface Temperature when using the Vegetation Health Index over dry regions. Global and Planetary Change 190, 103198, https://doi.org/10.1016/j.gloplacha.2020.103198 (2020).
Bi, W. et al. A global 0.05 degrees dataset for gross primary production of sunlit and shaded vegetation canopies from 1992 to 2020. Scientific Data 9, https://doi.org/10.1038/s41597-022-01309-2 (2022).
Liu, X. F. et al. Compound droughts slow down the greening of the Earth. Global Change Biology 00, 1–13, https://doi.org/10.1111/gcb.16657 (2023).
Vicente-Serrano, S. M. et al. Response of vegetation to drought time-scales across global land biomes. Proceedings of the National Academy of Sciences of the United States of America 110, 52–57, https://doi.org/10.1073/pnas.1207068110 (2013).
Zhu, X. R. et al. Soil coarsening alleviates precipitation constraint on vegetation growth in global drylands. Environmental Research Letters 17, https://doi.org/10.1088/1748-9326/ac953f (2022).
Dunn, R. J. H. et al. Global Climate. Bulletin of the American Meteorological Society 103, S11–S142, https://doi.org/10.1175/BAMS-D-22-0092.1 (2022).
van der Schrier, G., Barichivich, J., Briffa, K. R. & Jones, P. D. A scPDSI-based global data set of dry and wet spells for 1901–2009. Journal of Geophysical Research: Atmospheres 118, 4025–4048, https://doi.org/10.1002/jgrd.50355 (2013).
EM-DAT. CRED/UCLouvain, <Brussels, Belgium> (www.emdat.be).
Zeng, J. et al. Global_1981-2021_4km_Improved_VHI_Index_and_Best_Contribution_Parameter. figshare https://doi.org/10.6084/m9.figshare.19811854.v5 (2022).
Karnieli, A. et al. Use of NDVI and Land Surface Temperature for Drought Assessment: Merits and Limitations. Journal of Climate 23, 618–633, https://doi.org/10.1175/2009jcli2900.1 (2010).
Monteleone, B., Bonaccorso, B. & Martina, M. A joint probabilistic index for objective drought identification: the case study of Haiti. Nat. Hazards Earth Syst. Sci. 20, 471–487, https://doi.org/10.5194/nhess-20-471-2020 (2020).
Kogan, F., Salazar, L. & Roytman, L. Forecasting crop production using satellite-based vegetation health indices in Kansas, USA. International Journal of Remote Sensing 33, 2798–2814, https://doi.org/10.1080/01431161.2011.621464 (2012).
Zeng, J. et al. Ecological sustainability assessment of the carbon footprint in Fujian Province, southeast China. Frontiers of Earth Science 15, 12–22, https://doi.org/10.1007/s11707-020-0815-3 (2021).
Wang, Q. et al. Pronounced Increases in Future Soil Erosion and Sediment Deposition as Influenced by Freeze–Thaw Cycles in the Upper Mississippi River Basin. Environmental Science & Technology 55, 9905–9915, https://doi.org/10.1021/acs.est.1c02692 (2021).
Wang, Q., Tang, J., Zeng, J., Leng, S. & Shui, W. Regional detection of multiple change points and workable application for precipitation by maximum likelihood approach. Arabian Journal of Geosciences 12, 745, https://doi.org/10.1007/s12517-019-4790-5 (2019).
Wang, Q. et al. The effects of air temperature and precipitation on the net primary productivity in China during the early 21st century. Frontiers of Earth Science 12, 818–833, https://doi.org/10.1007/s11707-018-0697-9 (2018).
Mann, H. B. Nonparametric Tests Against Trend. Econometrica 13, 245–259, https://doi.org/10.2307/1907187 (1945).
Kendall, M. G. Rank correlation methods. British Journal of Psychology 25, 86–91 (1990).
Jay, S. et al. Exploiting the centimeter resolution of UAV multispectral imagery to improve remote-sensing estimates of canopy structure and biochemistry in sugar beet crops. Remote Sensing of Environment 231, 110898, https://doi.org/10.1016/j.rse.2018.09.011 (2019).
Kou, P. L. et al. Complex anthropogenic interaction on vegetation greening in the Chinese Loess Plateau. Science of the Total Environment 778, 146065, https://doi.org/10.1016/j.scitotenv.2021.146065 (2021).
Acknowledgements
This research received financial support from the Key Laboratory of Environmental Change and Natural Disaster of Ministry of Education (2022-KF-15), the National Natural Science Foundation of China (41601562), the Natural Science Foundation of Fujian Province (2021J01627) and Zhejiang Provincial Department of Science and Technology Public Welfare Technology Research Program Project (LGF21D010001).
Author information
Authors and Affiliations
Contributions
J.Z. developed the data set and methodology, collected and analyzed the data, provided statistics and material (figures and tables) for the paper, and wrote the manuscript. T.Z., Y.Q., V.B., J.Q., Y.X., Y.L. and Q.W. discussed the results of the manuscript.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Zeng, J., Zhou, T., Qu, Y. et al. An improved global vegetation health index dataset in detecting vegetation drought. Sci Data 10, 338 (2023). https://doi.org/10.1038/s41597-023-02255-3
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41597-023-02255-3
This article is cited by
-
The first global multi-timescale daily SPEI dataset from 1982 to 2021
Scientific Data (2024)
-
Understanding climate change impacts on drought in China over the 21st century: a multi-model assessment from CMIP6
npj Climate and Atmospheric Science (2024)
-
Evaluate the differences in carbon sink contribution of different ecological engineering projects
Carbon Research (2024)
-
Vegetation drought risk assessment based on the multi-weight methods in Northwest China
Environmental Monitoring and Assessment (2023)
-
A review of widely used drought indices and the challenges of drought assessment under climate change
Environmental Monitoring and Assessment (2023)