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The lightning clustering algorithm for spaceborne lightning observations clusters events into flash products and plays a crucial role in lightning-related research. This paper modified the lightning clustering algorithm based on the routine algorithm of Lightning Mapping Imager (LMI) and applied it to lightning events recorded by the LMI in 2019 to study the flash duration and flash area and specially to reveal the extreme lightning. To reveal the temporal and spatial features of lightning, the MCA (modified cluster algorithm) flash products defined flash duration and flash area. The results showed that continental regions have higher lightning frequencies but smaller events per flash, flash durations and flash areas than the ocean. The Tibetan Plateau has a low lightning frequency and smaller flash duration and area than eastern China. The flash count, events per flash, flash duration and flash area are higher during nighttime than during daytime. The relationship between flash duration and flash area showed distinct regional differences. In the MCA flash product, about 0.6% (0.1%) flashes have duration (area) that exceeds 1.0 s (5,000 km2). Finally, we analyzed two extreme lightning cases in eastern China, where the longest flash duration was 4.748 s and the largest flash area was 17,100 km2. This research contributes to advancing our understanding in the features of space-based lightning in the Eastern Hemisphere and applications to convection study. • Clustering algorithm was modified to study lightning with extreme duration and area. • Lightning duration and area both implied regional differences. • Quantitative relationship of duration and area was established in different regions. • The longest flash duration/largest flash area was 4.75 s/17100 km2 in eastern China. [ABSTRACT FROM AUTHOR]

South Asian air pollutants exert substantial effect on the climate and environment change over the Tibetan Plateau (TP). This paper investigates the trans-boundary transport of PM 10 , PM 2.5 , and O 3 from South Asia to the TP via WRF-Chem sensitive analysis. It is found that PM 10 , PM 2.5 , and O 3 over South Asia are mainly sourced from anthropogenic sources. South Asian emissions contribute up to 54% of PM 10 (PM 2.5) in the TP in the pre-monsoon season. For O 3 , the highest contribution of 18.13% is in the monsoon season, while the lowest contribution of 8.67% is in the winter season. To evaluate the respective contributions of anthropogenic and biomass burning emissions in South Asia to PM 10 , PM 2.5 , and O 3 in the TP, anthropogenic and biomass burning emissions in South Asia are considered separately. The results show that the largest percentage contribution of PM 10 (PM 2.5) from South Asian anthropogenic emissions to PM 10 (PM 2.5) in the TP with value of 35.86% (37.77%) occurs in winter, while the lowest percentage contribution of 16.52% (16.77%) appears in the monsoon season. For O 3 , the largest contribution of 17.74% from South Asian anthropogenic emissions appears in the monsoon season, whereas the lowest contribution of 8.59% occurs in winter. Compared to the anthropogenic emissions, the biomass burning emissions in South Asia have a relative less contribution to PM 10 , PM 2.5 , and O 3 in the TP. The largest contribution of PM 10 (PM 2.5) from South Asian biomass burning emissions to PM 10 (PM 2.5) in the TP is 20.04% (18.37%) in the pre-monsoon season. Conversely, the lowest contribution of 0.58% (0.53) appears in the monsoon season. O 3 from South Asian biomass burning emissions contributes <1% to O 3 in the TP in each season, implying that the biomass burning emissions in South Asia have little effect on O 3 in the TP. This study is of great significance to the ecological environment protection for the TP. • Contributions of South Asian emissions to PM 10 , PM 2.5 , and O 3 in the TP are quantified. • Anthropogenic emissions in South Asia have a larger contribution to PM 10 , PM 2.5 , and O 3 in the TP. • O 3 from South Asian biomass burning emissions contributes <1% to O 3 in the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The ozone valley over the Tibetan Plateau (TP) has an important effect on global weather and climate. As a significant source of atmospheric gravity waves (GWs), TP is also a key area of global stratosphere-troposphere exchange (STE), yet the exploration of the causes of low ozone values over the TP has been scarce from the perspective of GW. In this paper, we used the hyperspectral Atmospheric Infrared Sounder (AIRS) data to extract GWs and deep convection over the TP and analyzed the statistical characteristics of ozone for corresponding events. The results show that: (1) The GWs observed by AIRS mainly occur in the mid-latitude region, with a maximum frequency of >10%, and their intensity varies with longitude. Three large-value regions have been identified on the coast of Southeast Asia, Central America, and Central Africa. (2) Most deep convection occurs in the Intertropical Convergence Zone (ITCZ), with three large value centers in the East Asian monsoon region, Central America and Central Africa. Among them, the Indian monsoon region, the Northwest Pacific region to the east of the Philippines, and the western side of the South China Sea (SCS) are the large-value areas within the East Asian monsoon region, with the maximum occurrence frequency exceeding 15%. (3) TP is a region with a large frequency of convective gravity waves. In most areas of the southern foothills of the TP, the frequency of GWs related to convection is 30%–50%. Almost all deep convection over the TP and its adjacent areas are accompanied by GWs, with a frequency of 60–90%. (4) The composite analysis results show that the occurrence of GWs or deep convection is accompanied by negative anomalies of ozone in most areas of the southern foothills of the TP, indicating a decrease in the integrated column amount of ozone. (5) By analyzing the anomaly distribution of meteorological elements such as cloud fraction, cloud top height, tropopause height, and outgoing longwave radiation (OLR), the results show a dual effect in the presence of GWs or deep convection. The effect involves not only an increased generation of clouds, conducive to convection but also elevated cloud top height, promoting the formation of high clouds, some even beyond the tropopause. In addition, the occurrence of GW or deep convection can also affect the tropopause height, strengthen convective activity, and facilitate the upward transfer of low-concentration ozone from the lower layer to the upper layer, thereby causing a decrease in the integrated column amount of ozone. • The gravity waves (GWs) observed by AIRS mainly occur in the mid-latitude region. • Tibetan Plateau (TP) is a region with a large frequency of convective gravity waves. Almost all deep convection over the TP and its adjacent areas are accompanied by GWs, with a frequency of 60–90%. • The occurrence of GWs or deep convection is accompanied by negative anomalies of ozone in most areas of the southern foothills of the TP, indicating a decrease in the integrated column amount of ozone. • Occurrence of GW or deep convection can affect the tropopause height, strengthen convective activity, and facilitate the upward transfer of low-concentration ozone from the lower layer to the upper layer, thereby causing a decrease in the integrated column amount of ozone. [ABSTRACT FROM AUTHOR]

Based on the observational and reanalysis datasets, a dipole pattern of the early summer (June) precipitation over the eastern Tibetan Plateau (TP) is identified through empirical orthogonal function. In contrast to previous researches, this paper introduces the May North Atlantic Oscillation (NAO) as a preceding signal and investigates its connection with subsequent early summer precipitation over the eastern TP during 1980–2019, focusing on predictive aspects. Results reveal that the correlation between NAO and primary eastern TP precipitation pattern (Precip_EOF1) has weakened since 2000. During 1980–2000, an equivalent barotropic Silk Road Pattern (SRP) observed across Eurasia triggers southerly wind anomalies over the TP. This, in turn, leads to the northward shift of the water vapor, which favors the ascending motion over the northern TP (NTP) due to water vapor convergence. Additionally, the SRP-related sensible heating also plays a critical role in vertical motion over the eastern TP by enhancing the TP thermal effect. Consequently, these factors contribute to shaping the dipole pattern of eastern TP precipitation. However, the weakened relationship between NAO and Precip_EOF1 during 2001–2019 is attributed to the absence of NAO-related atmospheric circulation over Eurasia. Further analysis suggests that these circulation anomalies arise from the interdecadal variability of the NAO and its phase shift. Moreover, when the influence of sea surface temperature anomalies over the northern North Atlantic is removed, the correlation of Precip_EOF1 with NAO and Atlantic Multidecadal Oscillation (AMO) both become insignificant. This suggests that the NAO-related dipole pattern of eastern TP precipitation is modulated by preceding northern North Atlantic sea surface temperature rather than AMO on the interdecadal timescale. • The relationship between North Atlantic Oscillation (NAO) and Tibetan Plateau (TP) precipitation has weakened since 2000. • The change in NAO-related Silk Road Pattern (SRP) is the dominant reason for the unstable correlation. • The interdecadal variability in TP precipitation is attributed to the NAO phase shift. • This relationship is modulated by northern North Atlantic sea surface temperature on the interdecadal scale. [ABSTRACT FROM AUTHOR]

This paper examines the local and non-local climatic effects of wetter arid areas of Northwestern China (ANWC) in summer using a fully coupled climate model. In response to soil moisture increase, the local air temperature significantly decreases, and precipitation increases in summer. The wetter ANWC results in a warmer and rainless climate over the Central part of North China Plain (CNCP). While the influence of increasing soil moisture on the Tibetan Plateau (TP) precipitation is negligible due to the high altitude. A cooler climate over ANWC leads to an abnormal descending motion occurring. Meanwhile, an anomalous high pressure and an abnormal anticyclonic circulation occurs in 500 hPa over the west of ANWC. Correspondingly, a huge anomalous cyclone circulation occurs over the northeastern part of China and Mongolia, which can hinder the northward movement of the East Asian summer Monsoon (EASM) and reduce the water vapor transport into Central China Plain. As a result, the weakened EASM thus leads to rainless over CNCP. As soil moisture increases over ANWC is stronger, the magnitudes of the influence on the atmospheric field become larger. This study highlights the wetter ANWC effect on local climate and provides more information about the mechanism of wetter ANWC remote effect on non-local climate. • This paper examines the local and non-local climatic effects of wetter arid areas of Northwestern China (ANWC) in summer using a fully coupled climate model. • It finds that the wetter ANWC can result in a warmer and rainless climate over the Central part of North China Plain (CNCP) through a complex atmospheric circulation response. • A cooler climate leads to an abnormal descending motion occurring over ANWC. • A huge anomalous cyclone circulation over the northeastern part of China and Mongolia can block the East Asian summer Monsoon northward and decrease the water vapor transport into Central China Plain. • This study highlights the wetter ANWC effect on local climate and provides more information about the mechanism of wetter ANWC remote effect on non-local climate. [ABSTRACT FROM AUTHOR]

Actual evapotranspiration (ET a) is an important component of the global energy exchange process and hydrological cycle. ET a data with high accuracy are of great significance to the understanding of hydrological processes and the regulation of local climate. In this paper, an ET a product with hourly temporal resolution for the entire Tibetan Plateau (TP) was proposed by using Fengyun-4A geostationary satellite data and a random forest (RF) model. Validation between RF-based ET a and in situ observations from six eddy-covariance stations over the TP showed a root mean square error (RMSE) of 0.991 mm day−1. Compared with the ET a results from the surface energy balance system (SEBS), maximum entropy production (MEP) and the European Centre for Medium-Range Weather Forecasts Reanalysis Fifth Generation (ERA5) with RMSE values of 1.997 mm day−1, 2.182 mm day−1 and 1.555 mm day−1, respectively, the RF model showed the best performance. The annual RF-based ET a over the entire TP was approximately 365.60 mm. Thus, the total water amount evapotranspired from the TP surface was approximately 9811.01×108 t yr−1. Additionally, diurnal, monthly and seasonal ET a variations in different land cover types and climate zones over the TP and their contributions to the total ET a were clearly quantified. • Hourly actual ET over the entire Tibetan Plateau (TP) was firstly obtained by the random forest model (RF). • The RF ET a showed the best performance in estimation of hourly ET a data, including RF, SEBS, MEP and ERA5. • ETa variations of different land cover types and climate zones over the TP were clearly identified. [ABSTRACT FROM AUTHOR]