Understanding and Attribution of Extreme Heat and Drought Events in 2022: Current Situation and Future Challenges

Zhang, Lixia; Yu, Xiaojing; Zhou, Tianjun; Zhang, Wenxia; Hu, Shuai; Clark, Robin

doi:10.1007/s00376-023-3171-x

Cited by 31 publications

(3 citation statements)

References 37 publications

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“…Figure 9 presents the daily variations in ET from August 28 th , 2022, to September 1 st , 2022, within the Yangtze River Basin, along with the mean ET and Global Unified Gauge-Based Analysis of Daily Precipitation recorded during this period. According to a study by Zhang et al (2023), the summer of 2022 witnessed a severe drought within the Yangtze River Basin. This drought commenced in July, gradually relenting in late August and early September.…”

Section: Resultsmentioning

confidence: 99%

Satellite-based Near-Real-Time Global Daily Terrestrial Evapotranspiration Estimates

Huang,

Luo,

Chen

et al. 2024

Preprint

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Abstract. Accurate and timely information on global terrestrial actual evapotranspiration (ET) is crucial in agriculture, water resource management and drought forecasting in a changing climate. While numerous satellite-based ET products have been developed in recent decades, few provide near-real-time global terrestrial ET estimates. The MOD16 ET dataset, currently updating at the fastest rate, still experiences a delay of over two weeks. This is because most satellite-based ET algorithms rely on meteorological data from land surface models or in situ measurements, which cannot be obtained in near-real-time, resulting in delays of more than two weeks. To expedite global ET data access, we developed the Moderate Resolution Imaging Spectroradiometer (MODIS) based Variation of Standard Evapotranspiration Algorithm (VISEA) to provide global daily ET data within a week of the actual measurements at a spatial resolution of 0.05°. The VISEA model incorporates several key components: (1) A vegetation index (VI)-temperature (Ts) triangle method to simulate air temperature (Ta), serves as a basis for calculating other meteorological parameters (e.g., water vapor deficit and wind speed); (2) A daily evaporation fraction (EF) method based on the decoupling parameter, converts satellite-based instantaneous observations into daily ET estimates; (3) A net radiation calculation program takes into account cloud coverage in the atmosphere's downward longwave radiation. The VISEA model is driven by shortwave radiation from the European Centre for Medium-range Weather Forecasts (ERA5-Land) and MODIS land products, e.g., surface reflectance, land surface temperature/emissivity, land cover products), vegetation indices, and albedo as inputs. To assess its accuracy, we compared VISEA-with measurements from 149 flux towers, five other satellite-based global ET products, and precipitation data from the Global Precipitation Climatology Centre (GPCC). The evaluations show that the near-real-time ET using VISEA performs with similar accuracy to other existing data products and offers a significantly shorter time frame for daily data availability. Over 12 landcover types, the mean R is about 0.6 with an RMSE of 1.4 mm day-1 at a daily scale. Furthermore, the consistent spatial patterns of multi-year average VISEA align closely with GPCC precipitation data, reaffirming the dataset's ability to accurately represent global terrestrial ET distribution. To emphasize the capabilities of the VISEA for drought monitoring, we analyzed the spatial and temporal variations of ET during a drought event and subsequent recovery with precipitation in the Yangtze River basin from August 28th to September 1st, 2022. The VISEA distinctly illustrated low ET levels (<0.2 mm day-1) across most areas of the Yangtze River Basin on August 28th, indicating the severity of the drought. Conversely, a noticeable increase in ET (>0.9 mm day-1) is observed on August 29th, signifying the retreat of the drought due to precipitation. The near-real-time global daily terrestrial ET estimates could be valuable for meteorology and hydrology applications requiring real-time data, particularly in coordinating relief efforts during droughts. The VISEA code and dataset are available at https://doi.org/10.11888/Terre.tpdc.300782 (Huang et al., 2023a).

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Section: Resultsmentioning

confidence: 99%

Satellite-based Near-Real-Time Global Daily Terrestrial Evapotranspiration Estimates

Huang,

Luo,

Chen

et al. 2024

Preprint

View full text Add to dashboard Cite

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“…As the longest river in China and the third-longest river globally, the Yangtze River spans a total length of 6300 km and covers a drainage area of 1.8 million km 2 (Figure 1), linked to the lives of hundreds of millions of people. In the summer of 2022, the whole Yangtze River Basin experienced an unprecedented drought characterized by unusual spatial extent and intensity (Liu et al, 2023;Wang & Yuan, 2023;Zhang, Yu, et al, 2023). The 2022 extreme drought combined with record-breaking high temperatures had a profound impact on various sectors, including water resources, agriculture, ecosystems and even hydropower generation (Hao et al, 2023;Xu et al, 2023).…”

Section: Introductionmentioning

confidence: 99%

Response of evapotranspiration to the 2022 unprecedented extreme drought in the Yangtze River Basin

Zhang,

Liu,

Wang

et al. 2024

Intl Journal of Climatology

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The response of evapotranspiration (ET) to drought is essential for understanding water availability under drought conditions, which has received increasing scientific attention but remains highly uncertain. An unprecedented extreme drought sweeping the whole Yangtze River Basin during the summer and autumn of 2022 provides a novel opportunity to explore the ET response to drought within large river basins. Here, we apply multiple ET products to investigate the spatiotemporal variation of ET during the 2022 extreme drought and analyse the response of ET to drought in the Yangtze River Basin. The results show that this drought, characterized by widespread substantial precipitation deficit and high level of atmospheric evaporative demand (AED), leads to evident abnormal ET. Over the whole basin, ET exhibits a notable increase in the initial 2 months of this drought, which can significantly reduce water availability. However, despite continued high AED, the increase in ET fails to remain in the following months due to limited moisture supply. This suggests that ET response to drought varies as drought progresses. Among other drought events from 2003 to 2022, the response of ET is similar to that in the 2022 extreme drought. Specifically, for most sub‐basins, ET typically shows positive anomalies in the early stage of drought, followed by negative anomalies in the late stage. Generally, our findings improve the understanding of the dynamic response of ET to drought at the basin scale, which is crucial for basin water security.

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“…The positive-phase CGT promotes the descending motion and suppresses the cloud cover and rainfall, directly promoting heatwaves and droughts over the mid-latitude NH 16 , 17 . For example, the highly enhanced CGT was the direct cause of unprecedented heatwaves in the Yangtze River valley of China, the whole of Europe, and the Great Lakes region of America in 2022 midsummer 11,18 . Besides the influence of atmospheric internal variability, the CGT is a typical tropical-extratropical teleconnection modulated by the El Niño-Southern Oscillation (ENSO) 19 .…”

Section: Main 1 Introductionmentioning

confidence: 99%

Recent change in ENSO’s impacts on the summertime circumglobal teleconnection and mid-latitude extremes

Qiao,

Tang,

Wang

et al. 2024

Preprint

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The boreal summer circumglobal teleconnection (CGT) provides valuable predictability sources for mid-latitude Northern Hemisphere climate anomalies and extreme events. Here, we show that the CGT’s circulation structure has displaced westward by a half-wavelength since the late 1970s, more severely impacting heatwaves and droughts over East Europe, East Asia and southwestern America. We present convergent empirical and modelling evidence to reveal the essential role of El Niño-Southern Oscillation (ENSO) in shaping this change. Before the late 1970s, ENSO indirectly promoted CGT by modulating the Indian summer monsoon rainfall (ISMR). Recently, the ENSO–ISMR linkage was weakened, but the westward-displaced ENSO forcing was able to directly trigger a Rossby wave response at the exit of the East Asian westerly jet due to the easterly vertical shear of the zonal basic flow over the tropical western North Pacific, thus shifting the previous CGT’s North Pacific and downstream centers westward along the subtropical jet waveguide. Moreover, the state-of-the-art models with prescribed anthropogenic forcing cannot simulate such changes, indicating their origin from natural variability. The knowledge gained from this work highlights the importance of studying the impacts of changing ENSO to improve seasonal prediction of mid-latitude extreme events.

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Understanding and Attribution of Extreme Heat and Drought Events in 2022: Current Situation and Future Challenges

Cited by 31 publications

References 37 publications

Satellite-based Near-Real-Time Global Daily Terrestrial Evapotranspiration Estimates

Satellite-based Near-Real-Time Global Daily Terrestrial Evapotranspiration Estimates

Response of evapotranspiration to the 2022 unprecedented extreme drought in the Yangtze River Basin

Recent change in ENSO’s impacts on the summertime circumglobal teleconnection and mid-latitude extremes

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