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By observing well‐known sea surface temperature (SST) indices and outputs from Climate Forecast System version 2 (CFSv2) hindcasts and predictions, in this study, we developed a hybrid statistical downscaling prediction model (HSDPM) based on a timescale decomposition approach, which effectively improved the forecasting ability of summer (June–August) precipitation over Hainan Island (HNSP) in China; this precipitation presented multiple obvious timescale variabilities. We found that the interannual variability of the HNSP is closely related to the observed North Atlantic tripole SST anomalies in the preceding winter and the summer sea level pressure over the South China Sea by CFSv2 predicted in March. On the other hand, the interdecadal variability in the HNSP is linked to the prewinter Pacific Interdecadal Oscillation (PDO) according to the observations, the CFSv2 predictions of the summer surface air temperature over the tropical central‐east Pacific. On this basis, both the interannual and interdecadal components of the HNSP are effectively predicted using the corresponding predictors via multiple regression; thus, the HSDPM is ultimately established by combining the above two components. Compared with the original CFSv2 model, the HSDPM model achieves a considerable improvement in performance in predicting the HNSP. Specifically, the temporal correlation coefficient, ratio of root‐mean‐square error and anomaly sign consistency rate between the observed and HSDPM‐predicted HNSPs are 0.70, 17.4% and 80.5%, respectively, which are significantly greater than the above three forecasting index values of 0.23, 38.3% and 48.8%, respectively, obtained from the original CFSv2 predictions. The application of the HSDPM may be beneficial for drought and flood prevention and mitigation in Hainan Island. [ABSTRACT FROM AUTHOR]

In the midsummer of 2022, a rare regional high-temperature event occurred in the Yangtze River Basin. Chongqing, as the center of this event, also experienced its strongest high temperature since 1961. In this paper, the characteristics of this event in Chongqing are reviewed in detail and compared with those of 2006. We have confirmed the following conclusions with detailed data: (1) In the midsummer of 2022, the number of days that the daily maximum temperature is exceeding 35 ℃ in Chongqing was the most since 1961, with the number of days that the daily maximum temperature above 40 ℃ increasing significantly compared with 2006. (2) The impact range of this event in Chongqing was quite extensive, especially the range with the daily maximum temperature exceeding 40 ℃ was the widest since 1961. (3) The high-temperature event was more extreme in 2022 than that in 2006. The maximum of daily maximum temperature was 45 ℃, and this is the first time that China has recorded a high temperature of 45 ℃ outside Turpan. There were 5 stations with daily maximum temperature exceeding 44 ℃, accounting for 1/3 of the number of stations with such temperature (15 stations) in China. (4) In the midsummer of 2022, Chongqing was dominated by the compound high-temperature day. Compared with 2006, the daytime high-temperature day decreased significantly, while the compound one increased obviously. [ABSTRACT FROM AUTHOR]

In 2021, the Yangtze–Huaihe River Basin (YHRB) of China underwent normal precipitation during the classical Meiyu period in June–July but suffered extreme precipitation and severe floods in August. The present study revealed that the extreme heavy precipitation anomalies over the YHRB region were closely related to the combined effect of the strong western North Pacific anomalous anticyclone (WNPAC) and East Asian middle–high latitude circulation anomalies in August 2021. Moreover, the background of sea surface temperature (SST) anomalies was a strong eastern-Pacific La Niña event that rapidly decayed in spring and a second La Niña emerged in late summer, accompanied by a weak tropical Indian Ocean warming and a strong tropical Atlantic warming in summer. The rapidly decaying La Niña event and the weak tropical Indian Ocean warming alone seem to be insufficient to induce the strong WNPAC in August 2021. Observational evidence and numerical experiments suggest that the rapid tropical Atlantic warming from late spring to summer observably contributed to the enhancement and westward shift of the WNPAC, and the cold SST anomalies in the eastern tropical Pacific associated with the second La Niña event also provided favorable conditions for a strong WNPAC in August 2021. Overall, rapid tropical Atlantic warming and the development of the second La Niña contributed to the strong WNPAC in August 2021, while the maintenance mechanism of the East Asian middle–high latitude circulation anomalies that controlled cold air activity remains unclear. [ABSTRACT FROM AUTHOR]

In this paper, the spatial and temporal characteristics of convective precipitation (CP) and large-scale precipitation (LSP) in southern China during 1980–2020 are analyzed using monthly mean precipitation data from MERRA-2. In addition, the possible effects of relative humidity on CP and LSP are explored. The results indicate the following. (1) The LSP dominates the proportion of total precipitation (TP). Both LSP and CP are more prevalent in the south and less prevalent in the north, but there is a difference in the regions of their maximum centers. (2) Significant interannual and seasonal variations are observed in precipitation. TP and LSP tended to be higher than average after the 1990s, while for the CP, a significant negative trend has dominated the past ten years. There are significant increasing trends for TP and LSP, with area-averaged linear trends of 78.1 mm/decade and 85.9 mm/decade, respectively, while that of CP is − 17.1 mm/decade. The increasing trends of LSP are mainly contributed by the precipitation of summer and autumn. (3) The variations of LSP are affected by relative humidity in the troposphere, while CP is only influenced by the changes in relative humidity due to air temperature or specific humidity. The trend of relative humidity is − 0.33%/decade, mainly due to rising temperature in the troposphere. (4) Changes in relative humidity caused by temperature or specific humidity alone act on large-scale precipitation through both interannual and interdecadal processes, causing large-scale precipitation to increase, and the convective precipitation is mainly affected by the interdecadal processes. [ABSTRACT FROM AUTHOR]

Northeast China (NEC) is located between the subtropical monsoon and temperate-frigid monsoon regions and exhibits two successive rainy seasons with different natures: the northeast cold vortex rainy season in early summer (May–June) and the monsoon rainy season in late summer (July–August). Summer rainfall over NEC (NECR) has a fundamental influence on society, yet its successful seasonal prediction remains a long-term scientific challenge to current dynamical models. The poor NECR prediction skill is partly attributed to the large NECR variability at both the interannual and interdecadal time scales. Here, we focus on the oceanic drivers of the late summer NECR variability and associated physical processes at interannual time scale. Then, we establish an empirical prediction model to predict the interannual variability of summer NECR at 1-month lead time (in June). The analysis of observations spanning 40 years (1963–2002) reveals three physically and synergistically influencing predictors of the late summer NECR interannual variability. Above-normal NECR is preceded in the previous spring by (a) warm sea surface temperature (SST) anomalies in the tropical northern Indian Ocean, (b) a positive thermal contrast tendency in the tropical West–East Pacific SST, and (c) a positive tendency of the North Atlantic tripolar SST. These precursors enhance the anomalous low-level anticyclone over the western North Pacific and southerly anomalies over NEC in late summer, which are beneficial to enhancing NECR. An empirical prediction model built on these three predictors achieves a forecast temporal correlation coefficient (TCC) skill of 0.72 for 1961–2019, and a 17-year (2003–2019) independent forecast shows a significant TCC skill of 0.70. The skill is substantially higher than that of five state-of-the-art dynamical models and their ensemble mean for 1979–2019 (TCC = 0.24). These results suggest that the proposed empirical model is a meaningful approach for the prediction of NECR, although the dynamical prediction of NECR has considerable room for improvement. [ABSTRACT FROM AUTHOR]

This study identified an enhanced interannual relationship between early‐summer (June–July) tropical eastern Pacific (TEP) sea surface temperature (SST) and subsequent mid‐summer (July–August) precipitation in North China (NC) since the late 1970s. For 1951–1972, the relationship between early‐summer TEP SST and mid‐summer NC precipitation were statistically insignificant. In contrast, for 1977–2018, they were positively significant. Since the late 1970s, the early‐summer negative TEP SST anomaly was generally followed by a significant anomalous anticyclone over the Korean Peninsula and its environs; that facilitated anomalous southerly winds over NC, conveying more moisture from the North Pacific, leading more precipitation over NC. Further studies show that the enhanced relationship between early‐summer TEP SST and tropical Indian Ocean to WNP SST are suggested to be responsible for significantly anticyclonic anomalies over WNP after the late 1970s. [ABSTRACT FROM AUTHOR]

Persistent extreme heat events (PEHEs) exert a more negative impact on society, including agriculture, plant phenology, power production and human health, compared to general EHEs. The temporal and spatial characteristics of summer PEHEs in eastern China were analysed based on a daily maximum temperature dataset from 759 stations over the period of 1961–2018. The results show the following: Persistent distributions of PEHEs show that they are characterized by an exponential decay with a drop in the decay rate. In terms of spatial distribution, there is an apparent regional difference in the duration of PEHEs. North China is dominated by multi-frequency and short-duration EHEs, while South China is the opposite. PEHEs in North China and the Huanghuai region mainly occur in June-July but mostly in July and August in South China. Strongly responding to global warming, the frequency and duration of PEHEs in North China have increased since the 1990s. However, the frequency of PEHEs in North China and the Huanghuai region has shown opposite trends in June-July since the beginning of the twenty-first century. Affected by the atmospheric circulations, the regional differences in PEHE frequency are also apparent. Since the beginning of the twenty-first century, the PEHEs in North China and the Huanghuai area have shown an increasing trend in August. The short-term PEHEs in the middle and lower reaches of the Yangtze River and South China increased rapidly in the 2000s, while long-term PEHEs increased in the 2010s. This study implies that attention should be paid to not only the frequency of EH days but also to the persistence of EHE which is a key characteristic of damaging EH. [ABSTRACT FROM AUTHOR]

An extremely heavy snowfall event occurred in early winter (November–December) 2018 over the northeast of Tibetan Plateau (NTP), with snowfall amounts ranking the highest since 1961. It is necessary to better understand the causes and reveal the physical mechanism of this extreme snowfall event. In this article, the features of this extreme snowfall event and its possible linkage with atmospheric circulation anomalies, and sea surface temperature (SST) anomaly effects are analyzed. The results show that in early winter 2018, (1) there was a similar Eurasian teleconnection (EU) pattern in the mid-latitudes with a periodic strengthening of the Siberian High, which favored northern cold airflow into the NTP, providing the suitable temperature conditions for snowfall. (2) Low-latitude meridional and mid-latitude zonal water vapor transport were both significantly greater than normal, causing much more water vapor flow than normal into the NTP region through the western and southern boundaries, leading to the second highest net water vapor input since 1961 and creating sufficient continuous water vapor conditions for extreme snowfall. (3) The baroclinicity and the instability of the atmospheric circulation, accompanied by abnormal cold and warm advection and vertical movement over the NTP, provided the dynamic atmospheric conditions for the snowfall event. (4) Under the background of warm El Niño Southern Oscillation (ENSO) event and the positive phase of the Tropical Indian Ocean dipole (IOD) SST, the EU pattern initiated by the tele-influence of IOD mode dominated the midlatitude region across Eurasia continent. The positive anomalies of EU teleconnection over western Asia guided the heavy water vapor flow into the NTP through the western and southern boundaries, respectively. In addition, the effects of ENSO/IOD caused the northern Indian Ocean and northwest Pacific to be dominated by anticyclones, creating more northward water vapor transport from the tropical region. Accordingly, sufficient water vapor flowed into the NTP along the eastern edge of the Tibetan Plateau, providing the moisture conditions for the severe snowfall event. [ABSTRACT FROM AUTHOR]

The inter‐decadal variation of autumn rain of west China (ARWC) and its relationship with atmospheric circulation and sea surface temperature anomalies (SSTAs) was analysed. The intensity of ARWC shows significant inter‐decadal variability. The year 1990 is one of the abrupt change points of ARWC in both the southern and northern zone, and the year 2000 is another one in the northern zone. The inter‐annual correlation between the intensity of ARWC in the northern (southern) zone and the El Niño–Southern Oscillation continuously weakens (strengthens) from 1961. The relationship between the intensity of ARWC in the northern zone and atmospheric circulation of September–October mean significantly weakens after 2000, so does the relationship with the SSTAs in the equatorial central Pacific. On the contrary, the relationship between the intensity of ARWC in the southern zone and atmospheric circulation of September–October mean significantly strengthens after 1990, so does the relationship with the east–west contrast pattern of SSTAs in the equatorial central–western Pacific. The positive phase of the east–west contrast pattern of SSTAs in the equatorial central–western Pacific (i.e., when the tropical central [western] Pacific is colder [warmer] than normal) gradually strengthening and maintaining from the preceding spring to September–October is favourable for a stronger western Pacific subtropical high, which further facilitates northwards transportation of water vapour and provides better dynamic conditions for ARWC in the southern zone by strengthening the local Hadley circulation. [ABSTRACT FROM AUTHOR]

We analyzed the anomalous characteristics of autumn rain in western China (ARWC) (26.2–36° N, 101.9–111.8° E) in 2017 and the related large-scale atmospheric circulations based on new monitoring indicators published by the China Meteorological Administration in 2015 and the National Center for Environmental Prediction reanalysis data. We found that the characteristics of autumn rain in the southern (33–36° N, 101.9–111.8° E) and northern (26.2–33° N, 101.9–111.8° E) regions of the monitoring area were different. The onset date of autumn rain in the north (south) of the monitoring area in 2017 was 14 (16) days earlier than in normal years, which is in the 4th (4th) place since 1961. The end of the autumn rain was 5 days later (earlier) than in normal years. The autumn rain period was 54 (63) days long, 19 (11) days longer than in normal years. The autumn rainfall in the north (south) of the monitoring area was 234.1 (322.2) mm, 72.6% (74.4%) higher than that in normal years. The amount of autumn rain in the southern region is in the second place since 1965. The cause of this significantly early onset of the ARWC in 2017 was the advanced transition of the East Asian atmospheric circulation system from a summer pattern to a winter pattern. The westerly jet in the upper troposphere appeared about 10 days earlier than in normal years. The meridional circulation of a west-high and east-low pattern was observed in the mid- and lower troposphere in the mid- and high latitudes of Eurasia. This circulation configuration resulted in an early onset of the ARWC. As a result of the influence of the persistent warming of the Indian Ocean basin-wide mode from spring to summer, the west Pacific subtropical high was extremely strong (the second strongest since 1981) and its westernmost point was greatly extended to the west (the second greatest extension since 1981) during the autumn rain period. The intensity of the moisture flux from the southwest of the western Pacific subtropical high was stronger than usual and the low trough of Lake Baikal was also strong. Cold air from the north and the abundant warm, humid water vapor from the south converged in western China, resulting in more precipitation during the autumn rain period. [ABSTRACT FROM AUTHOR]

Abstract We report here a high temperature directed, self-assembly to the synthesis of ordered mesoporous organic polymers (OMPs) with different nanopore sizes and BET surface areas. The synthesized OMPs have large BET surface areas (219–512 m2/g), ordered mesopores, and adjustable pore volumes (0.20–0.48 cm3/g). Their rules of sub-nano level structures such as free volumes, unopened nanopores and electronic environment in the synthesized OMP materials were systematically investigated by using positron annihilation lifetime spectroscopy, which acts as an important technique for investigating microstructures of ordered mesoporous organic polymers and optimization of synthetic conditions of porous organic polymers. Highlights • Ordered mesoporous polymers (OMPs) were hydrothermally synthesized at high temperatures. • Ordered mesopores was constructed from self assembly of copolymer template with resol. • OMPs contain abundant sub-nano level structures such as free volumes, unopened nanopores. • Sub-nano level structures of OMPs were investigated by positron annihilation technique. • Positron annihilation act as useful technique for optimization of synthetic conditions of OMPs. [ABSTRACT FROM AUTHOR]

Using precipitation data from weather stations in China and reanalysis data from National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR), the inter‐annual and inter‐decadal variability of early‐summer (May–June) and late‐summer (July–August) precipitation (hereinafter referred to as MJP and JAP, respectively) over northeast China (NEC) and their background circulation during 1951–2016 were analysed. The following new findings have been highlighted: (a) There are significantly different inter‐annual and inter‐decadal variability characteristics between MJP and JAP over NEC. The inter‐annual variability of MJP is independent from that of JAP, while the inter‐decadal variability of the former is opposite to that of the latter. A significant shift to more MJP (less JAP) occurred in the early 2000s (late 1990s). (b) In terms of the inter‐annual timescale, the large‐scale atmospheric circulations‐associated MJP is notably different from JAP over NEC. The variation in MJP is mainly dominated by the northeast China low (NECL) and the Okhotsk blocking high (OBH), while JAP is mainly influenced by the western Pacific subtropical high (WPSH), the NEC south wind (NESW), and the NECL. (c) On the inter‐decadal timescale, MJP is associated with the inter‐decadal variation of the East Asia/Pacific (EAP) teleconnection, while JAP is closely related to the inter‐decadal variation of the NECL and NESW. When the EAP is in a positive phase, MJP is more than average. Furthermore in late summer, the strong NECL and NESW are both of benefit to the convergence of water vapour from the tropical southwest and East Asian subtropical westerlies over NEC, which contributes to the more JAP than average. [ABSTRACT FROM AUTHOR]

In this study, the simultaneous atmospheric circulation system configuration characteristics of the four rainfall patterns (FRP) over the East China during the period 1951–2015 are analyzed in order to investigate their formation mechanisms. The results confirm that the FRP possess obvious differences in the upper-level, middle-level, and lower-level troposphere. In northern China rainfall pattern (NCP) years, the East Asian subtropical westerly jet stream (EAJS) shows a northward trend, with a higher intensity than normal; the blocking high (BH) in the mid-high latitudes is inactive; and the western Pacific subtropical high (WPSH) tends to be stronger, with a location to the north of its normal position. The East Asian summer monsoon (EASM) is stronger, which promotes vapor transport to northern China, and this leads to increased rainfall. In intermediate rainfall pattern (IRP) years, the EAJS position is close to that in normal years; the BH is inactive; the WPSH tends to be weaker, with a location to the east of its normal position; and the EASM is stronger, which is conducive to increased rainfall over the Huaihe River Basin. In Yangtze River rainfall pattern (YRP) years, the circulations are found to be almost opposite in their features to those in NCP years. In South China rainfall pattern (SCP) years, the circulations are found to be almost opposite in their features to those in IRP years. This leads to increased rainfall over South China. Therefore, the different circulation system configuration characteristics lead to the different rainfall patterns. [ABSTRACT FROM AUTHOR]

In this study, the summer rainfall patterns in the East China monsoon region during 1951-2015 were objectively classified into four typical categories: the northern China rainfall pattern (NCP), the intermediate rainfall pattern (IRP), the Yangtze River rainfall pattern (YRP), and the South China rainfall pattern (SCP). The periods of the four patterns show significant decadal characteristics. The NCP occurred mainly between the late 1950s and the early 1980s, and the IRP in the late 1950s to the early 1970s and the 2000s. The YRP occurred mainly between the 1980s and the 1990s, and the SCP between the mid-1990s and the early 21st century. The relationship between the East Asian summer monsoon index (EASM I ) and the four rainfall patterns was comparatively analyzed. The results confirmed that the four rainfall patterns have obvious differences in the EASM. In the NCP, IRP, or SCP years, the EASM I primarily showed a positive phase and a strong summer monsoon; in the YRP years, the EASM I primarily showed a negative phase and a weak summer monsoon. [ABSTRACT FROM AUTHOR]

Have the onset dates of regional extreme hot events threatening human health been advancing? Based on the daily maximum temperature data from Chinese metrological stations and reanalysis datasets, we quantified the variations in the onset dates of the first regional extreme hot events (EHE-ODs) and revealed the early-onset characteristics of the regional EHEs in southeastern China. The results show that the EHE-ODs in southeastern China have a significant early-onset trend with an average advanced rate of 7.1 days/decade since 1987. The rate in the middle and lower reaches of the Yangtze River and South China exceeds 10.3 days/decade. The interannual variation in the sea ice over the Barents Sea (SICBS) in March and the snow depth over western Eurasia (SDWEA) in April are closely related to the first regional EHE-ODs in southeastern China, which both provide favorable atmospheric circulation patterns and significant descending motion for the occurrence of regional EHEs. The pathway of the physical process originates from the northern Eurasia propagating southeastward, and spreads to southeastern China, which can enhance the anticyclonic anomaly in southeastern China and favor the occurrence of regional EHEs in southeastern China in the early summer. Therefore, the SICBS in March might be a critical potential predictor for the onset of the regional EHEs in southeastern China. • The onset date of extreme hot events (EHE) in southeastern China has an early-onset trend. • The advanced rate of the early-onset trend of regional EHE exceeds 10.3 days/decade. • Barents Sea ice plays as a precursor for the onset date of EHE in eastern China. • Midlatitude Eurasian atmospheric wave train is related to the early onset of EHE. [ABSTRACT FROM AUTHOR]

The Eurasian teleconnection pattern (EU) is an important low-frequency pattern with well-known impacts on climate anomalies in Eurasia. The difference of low-level v-winds in several regions in the Eurasian mid-high latitudes is defined as the EU index (EUI). In this study, the relationship between the winter EUI and precipitation in the following summer over China is investigated. Results show that there is a significant positive (negative) correlation between the winter EUI and the following summer precipitation over North China (the Yangtze River-Huaihe River basins). Meanwhile, an interdecadal variability exists in the interannual relationship, and the correlation has become significantly enhanced since the early 1980s. Thus, the proposed EUI may have implications for the prediction of summer precipitation anomalies over China. In positive winter EUI years, three cyclonic circulation anomalies are observed-over the Ural Mountains, the Okhotsk Sea, and the subtropical western North Pacific. That is, the Ural blocking and Okhotsk blocking are inactive, zonal circulation prevails in the mid-high latitudes, and the western Pacific subtropical high tends to be weaker and locates to the north of its normal position in the following summer. This leads to above-normal moisture penetrating into the northern part of East China, and significant positive (negative) precipitation anomalies over North China (the Yangtze River-Huaihe River basins), and vice versa. Further examination shows that the SST anomalies over the Northwest Pacific and subtropical central North Pacific may both contribute to the formation of EUI-related circulation anomalies over the western North Pacific. [ABSTRACT FROM AUTHOR]

Recently, the European Center for Medium-Range Weather Forecasts (ECMWF) released a new set of reanalysis data—ERA-Interim. We make an intercomparison between ERA-Interim precipitation and observed precipitation in Northeast China. The results show that, in general, the ERA-Interim reanalysis precipitation data can describe the spatial and temporal characteristics of seasonal precipitation in Northeast China well. In terms of spatial distribution, ERA-Interim precipitation is generally consistent with the observation data in different seasons in Northeast China. There is a larger difference in the center of Northeast China than in other areas between the two kinds of data. The ERA-Interim precipitation is larger than observed precipitation in most of Northeast China. In spring, autumn, and winter, the ERA-Interim precipitation value is close to the observation one, while in summer there is a large difference in Liaoning Peninsula and Changbai Mountain between the two kinds of precipitation data. In terms of temporal characteristics, the time series of the ERA-Interim precipitation matches well with the observed precipitation in whole. In different seasons, the annual variation of the ERA-Interim precipitation is well correlated with that of the observed precipitation. [ABSTRACT FROM AUTHOR]

Based on the 1983∼2011 CMAP data, the precipitation anomaly in East Asia and its nearby sea regions (hereafter called East Asia for short) demonstrates the '+−+' pattern before 1999 and the '−+−' pattern afterwards; this decadal change is contained principally in the corresponding EOF3 component. However, the NCC_CGCM forecast results are quite different, which reveal the '+−+−' pattern before 1999 and the '−+−+' pattern afterwards. Meanwhile, the probability of improving NCC_CGCM's forecast accuracy based on these key SST areas is discussed, and the dynamic-statistics combined forecast scheme is constructed for increasing the information of decadal change contained in the summer precipitation in East Asia. The independent sample forecast results indicate that this forecasting scheme can effectively modify the NCC_CGCM's decadal change information contained in the summer precipitation in East Asia (especially in the area of 30°N-55°N). The ACC is 0.25 and ACR is 61% for the forecasting result based on the V SST area, and the mean ACC is 0.03 and ACR is 51% for the seven key areas, which are better than NCC_CGCM's system error correction results (ACC is −0.01 and ACR is 49%). Besides, the modified forecast results also provide the information that the precipitation anomaly in East Asia mainly shows the '+−+' pattern before 1999 and the '−+−' pattern afterwards. [ABSTRACT FROM AUTHOR]

With the influence of global warming, the global climate has undergone significant inter-decadal variation since the late 1970s. Although El Niño-Southern Oscillation (ENSO) has been the strongest signal for predicting global climate inter-annual variability, its relation with the summer rainfall in China has significantly changed, and its indicative function on the summer rainfall in China has weakened. This has led to a significant decrease in the accuracy rate of early conceptual prediction models for the Three Rainfall Patterns in the summer of eastern China. On the basis of the difference analysis of atmospheric circulation system configuration in summer, as well as the interaction of ocean and atmospheric in previous winter between two phases, i.e. before and after the significant global warming (1951 to 1978 and 1979 to 2012, respectively), we concluded that (1) Under different inter-decadal backgrounds, the atmospheric circulations that impacted the Three Rainfall Patterns in the summer of eastern China showed consistency, but in the latter phase of the global warming, the Western Pacific Subtropical High (WPSH) was on the strong side, the position of which was in the south, and the blocking high in the Eurasia mid-high latitudes was active, while the polar vortex extended to the south, and meridional circulation intensified. This circulation background may have been conducive to the increase of the circulation frequency of Patterns II and III, and the decrease of the circulation frequency of Pattern I, thus leading to more Patterns II and III and fewer Pattern I in the summer rainfall of eastern China. (2) In the former phase, the corresponding previous winter SST fields of different rainfall patterns showed visible differences. The impact of ENSO on North Pacific Oscillation (NPO) was great, and the identification ability of which on Patterns I and II of summer rainfall was effective. In the latter phase, this identification ability decreased, while the impact of ENSO on the Pacific/North American (PNA) teleconnection pattern increased, and the identification ability of the PNA on Patterns II and III also increased. Based on the new inter-decadal climate background, this study reconstructs the conceptual prediction model for the Three Rainfall Patterns in summer of eastern China by using the previous winter PNA and the Eurasian (EU) teleconnection indexes. The fitting effect was satisfying, though it is necessary to be further tested. [ABSTRACT FROM AUTHOR]

Annual maximum 7-day precipitation has increased over South China since 1961. Ten CMIP6 climate models simulate either weaker increases in risk ratio than observed or nonsignificant changes. [ABSTRACT FROM AUTHOR]

Thundersnow is a special kind of thunderstorm that combines snowfall and lightning. A 10‐year thundersnow climatology over China was obtained based on observations during 2008–2017. Our results show that thundersnows are widely distributed in China, and most of the high‐frequency areas are located in the Tibetan Plateau and northeastern China. The average frequency of thundersnow decreases with decreasing altitude, and thundersnow usually occurs at low‐altitude stations once every 10 years. Thundersnow, which likely induces great total snowfall depths, appears mostly in spring, autumn and late winter and can occur in high‐altitude areas in summer. The blizzard probability on a thundersnow day is 12.7%. The percentage of positive cloud‐to‐ground lightning of winter thundersnow is approximately 20.7%, which is lower than those in other seasons. The negative phase of the Arctic Oscillation and anomalous western North Pacific anticyclone are favorable background conditions for thundersnow events. Plain Language Summary: Though the snowfall process is different from common rainfall processes that are accompanied by lightning, it can also occasionally produce lightning. This special type of thunderstorm is called thundersnow. It can induce heavy snowfall, which results in partial paralysis of modern cities. Electrified winter clouds may pose an aviation hazard. Although the frequency of thundersnow is low, it is widely distributed in China. Thundersnow can occur throughout the year, mainly in February‐May and October‐November. Thundersnow events increase the probability of blizzards, especially in the Shandong Peninsula in spring, North China and the Changbai Mountain in autumn, and the middle and lower reaches of the Yangtze River basin and Bohai Rim in winter. The variations of the thundersnow number are closely associated with extratropical atmospheric circulation anomalies. The climatological and atmospheric conditions of thundersnow in China that are revealed by this study help establish an important basis for thundersnow forecasting. Key Points: A 10‐year climatology of thundersnow in China was revealed for the first timeThe high‐frequency areas of thundersnow are mainly located in the Tibetan Plateau and northeastern ChinaThundersnow is significantly influenced by the Arctic Oscillation and associated with the anomalous western North Pacific anticyclone [ABSTRACT FROM AUTHOR]

Accurate short-term climate predictions, specifically the prediction of dominant rain belts during flood seasons, represent a significant challenge, particularly in the absence of notable external forcing signal anomalies in the previous winter. To address this challenge, we propose a novel climate index based on an Auto-Encoder (AE) Neural Network that exhibits superior performance in indicating several significant precipitation events in the Yangtze and Huaihe River Basins under varying El Niño conditions. Notably, the novel climate index rectifies the discrepancy between the 2019/2020 Niño index and the 2020 summer precipitation. In order to understand the information source of AE, the causality between AE and other indices was further analyzed by Granger Causality. The results show that AE index mainly contains the information of subtropical high index and ocean index, which is consistent with previous studies. • AE obtained by Auto-encoder can make up for the "failure" of Nino index in abnormally heavy precipitation events. • In terms of magnitude and state, AE has better description of precipitation than Nino3.4. • The main indices of AE information are subtropical high-pressure index and sea surface temperature index. [ABSTRACT FROM AUTHOR]

A continuous overcast-rainy weather (CORW) process occurred over the mid-lower reaches of the Yangtze River (MLRYR) in China from February 14 to March 9 in 2009, with a large stretch and long duration that was rarely seen in historical records. Using the empirical orthogonal function (EOF), we analyzed the geopotential height anomaly field of the NCEP-DOE Reanalysis II in the same period, and defined the stable components of extended-range (10-30 days) weather forecast (ERWF). Furthermore, we defined anomalous and climatic stable components based on the variation characteristics of the variance contribution ratio of EOF components. The climatic stable components were able to explain the impact of climatically averaged information on the ERWF, and the anomalous stable components revealed the abnormal characteristics of the continuous overcast-rainy days. Our results show that the stable components, especially the anomalous stable components, can maintain the stability for a longer time (more than 10 days) and manifest as monthly scale low-frequency variation and ultra-long-wave activities. They also behave as ultra-long waves of planetary scale with a stable and vertically coherent structure, reflect the variation of general circulation in mid-high latitudes, display the cycle of the zonal circulation and the movement and adjustment of the ultra-long waves, and are closely linked to the surface CORW process. [ABSTRACT FROM AUTHOR]

In this study, we investigate the interdecadal variation characteristics of the dominant mode of summer precipitation over East Asia‐Northwest Pacific (EA‐NWP) before and after late 1990s, reveal the physical mechanism, and address its possible connection with the regional ocean warming background. Study results show that the empirical orthogonal function mode 1 (EOF1) of summer precipitation anomalies over EA‐NWP during the global ocean warming acceleration period (1979–1998) present a more significant dipole pattern between Yangtze River Basin (YRB) and tropical NWP compared with that during the global ocean warming slowdown period (1999–2012). And then we find that the anomalous dipoles of low‐level winds, geopotential height, convection, and associated wave activity fluxes over NWP significantly shift westward (eastward) and enhance (weaken) in 1979–1998 (1999–2012), which are regarded as the direct cause of the adjustment of dipole pattern between YRB and tropical NWP. Further analysis reveals that the negative sea surface temperature (SST) anomalies in the tropical NWP are prominent (not prominent), resulting in the stronger (weaker) Pacific–Japan Teleconnection over Japan and Tropics in NWP during the period 1979–1998 (1999–2012), and ultimately lead to the change of summer precipitation EOF1 in EA‐NWP. By regressing vertical velocity, outgoing longwave radiation, relative vorticity, wave activity fluxes, and precipitation onto the NWP SST in the two periods, the impacts of the SST in the NWP on the interdecadal variation of summer precipitation EOF1 in EA‐NWP are verified. Finally, the mechanism diagram of interdecadal variation of summer precipitation is given, which can be useful for short‐term precipitation prediction of East Asia. [ABSTRACT FROM AUTHOR]

By using the one-month‑lead predictions from the Climate Forecast System version 2 (CFSv2), this study evaluates the predictability of the unprecedented heatwaves hitting the Yangtze River Valley (YRV) and Tibetan Plateau (TP) in 2022 late summer. CFSv2 successfully reproduces the central China heatwaves, but shows distinct performances between the YRV and TP. Specifically, CFSv2 exhibits stronger ability to capture TP heatwaves that is close to the highest historical prediction record, whereas the predicted extremity of the YRV heatwaves is underestimated compared to the observations. The accurate simulation of the intense upper-level circumglobal teleconnection (CGT) pattern, particularly for the East Asia CGT center (CGT EA), is essential for the success predictions of high temperature anomalies, due to the strong and accurate linkage between CGT EA and YRV/TP heatwaves in CFSv2. The intense CGT pattern is associated with a stronger model response to developing La Niña in CFSv2, quite different from the observed leading contribution from the unprecedented Pakistan rainfall. The impacts of developing La Niña and Pakistan rainfall on the intense CGT pattern are significantly overestimated and underestimated by CFSv2, respectively. Additionally, the La Niña-forced enhancement of lower-level western Pacific subtropical high (WPSH) plays another important role in YRV heatwaves, but the reproduction of WPSH intensity is unable to reflect YRV heatwaves in CFSv2 due to the southeastward shift of the predicted WPSH location, which should be responsible for the underestimated YRV heatwaves. The model improvements in aspect of the Pakistan rainfall, El Niño-Southern Oscillation–CGT linkage and lower-level WPSH location should help effectively predict the central China heatwaves in the future. • CFSv2 successfully predicts the central China heatwaves in 2022 late summer. • The accurately predicted CGT is essential for the reproduction of heatwaves. • La Niña leads to the intense CGT in CFSv2 rather than Pakistan rainfall in observation. [ABSTRACT FROM AUTHOR]

The present study investigates relative contributions of interannual, intraseasonal, and synoptic variations of environmental factors to tropical cyclone (TC) genesis over the northern tropical Atlantic (NTA) during July–October. Analysis shows that convection, lower-level vorticity, and midlevel specific humidity contribute to TC genesis through intraseasonal and synoptic variations with a larger contribution of the latter. The relative contribution of three components of vertical wind shear depends largely on its magnitude. The contribution of sea surface temperature (SST) to TC genesis is mainly due to the interannual component when total SST is above 27.5°C. The barotropic energy for the development of synoptic-scale disturbances comes mainly from climatological mean flows and intraseasonal wind variations. The proportion of contribution between synoptic and intraseasonal variations of convection, relative vorticity, and specific humidity is larger over the eastern NTA than over the western NTA. The barotropic energy conversion has a larger part related to climatological mean flows and intraseasonal wind variations over the eastern and western NTA, respectively. There are notable differences between the NTA and the western North Pacific (WNP). One is that the relative contribution of synoptic variations of convection, relative vorticity, and specific humidity is larger over the NTA, whereas that of intraseasonal variations is larger over the WNP. The other is that the barotropic energy conversion related to climatological mean flows and intraseasonal wind variations is comparable over the NTA, whereas that related to climatological mean flows is larger over the WNP. [ABSTRACT FROM AUTHOR]

A string of niobium-iron composite oxides with varying Nb/Fe ratios and calcination temperatures were produced and utilized to remove mixed contaminants (500 ppmv chlorobenzene and 500 ppmv toluene in air), and the structure/texture of catalytic materials were systematically characterized. The findings of the structure-performance study revealed that the physicochemical qualities of Nb 2 O 5 -Fe 2 O 3 were greatly enhanced than pure metal oxide. The presence of iron oxide hindered the crystallization of niobium oxide, which aided in the uniform dispersion of niobium-iron components into each other. Forming FeNbO 4 at Nb/Fe molar ratio of 1/2 effectively improved the thermal stability of catalyst, withstood short-time thermal shock below 850 °C. The formation of niobium-iron composite oxides improved the specific surface area, optimized the pore size distribution, increased surface acid centers, enhanced reduction/oxidation cycle, and promoted metal-metal interaction for the Nb-Fe-O catalysts. At 320 °C, the catalytic degradation efficiency of 1Nb2Fe-500 could approach 90% for chlorobenzene and 85% for toluene, and it could sustain this efficiency for at least 80 h without evident deactivation, with a high CO 2 selectivity of 86%. Furthermore, the Nb-Fe-O catalysts met the environmentally benign and low-cost requirements for environmental catalysis. [Display omitted] • The Nb-Fe composite oxides were synthesized and structure/texture were characterized. • The formation of FeNbO 4 was an important factor affecting the catalyst activity. • 1Nb2Fe-500 exhibited high performance for eliminating mixture of C 6 H 5 Cl and C 6 H 5 CH 3. • The 1Nb2Fe-500 catalyst could withstand thermal shock below 800 °C. [ABSTRACT FROM AUTHOR]

Transition metal doped WO 3 mixed oxides (named as W-M-O, M = Nb, Fe, Cr, Cu, Ti or Sn, respectively) with high structure stability were synthesized by modified sol-gel method using citric acid as organic crosslinking agent, and were evaluated for catalytic elimination of low-concentration toluene, monochlorobenzene and 1,2-dichloroethance with high toxicity and relatively stable molecule structure, as the typical examples for the pollutants of various volatile organic compounds (VOCs). Results of the structure-property-performance relationship research showed that mesoporous structure and nanocrystalline/amorphous state were formed, and binary metal components were dispersed into each other, which contributed to promoting the metal/metal electron interaction and adjusting the physicochemical properties of mixed metal oxides. The sequence of apparent catalytic activity for toluene degradation was: W–Nb–O＞W–Fe–O＞W–Cr–O, W–Cu–O＞W–Ti–O＞W–Sn–O＞WO 3 , and the sequence for monochlorobenzene degradation was: W–Nb–O＞W–Fe–O＞W–Cr–O, W–Ti–O＞W–Cu–O＞W–Sn–O＞WO 3. There existed cooperative catalytic effect: mesopore and surface acid sites of catalysts facilitated adsorption, activation and breakage of the C-X bond, and then redox sites of catalysts promoted deep oxidation of a series of reaction intermediates to transform into CO 2 and H 2 O. Especially, the optimized W–Nb–O catalyst deserved more attention, since it represented remarkable catalytic activity, selectivity and durability for three typical VOCs degradation along with good resistance to water vapor and corrosion of HCl. [Display omitted] • WO 3 based transition metal mixed oxides were prepared by modified sol-gel method. • Interaction between WO 3 and MO x affected the properties of mixed oxides. • WO 3 –Nb 2 O 5 displayed the best catalytic performance for VOCs elimination. • Cooperative catalytic effect was observed in WO 3 –Nb 2 O 5 catalyst system. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the spatio-temporal characteristics of the amount of light rain and the number of days with light rain in the ESWC and explored the possible causes of the significant decrease in the number of days with light rain. The results show that: (1) Both the amount of light rain and the number of days with light rain over the ESWC in summer showed a decreasing trend, with linear trends of −1.5 mm/decade and −0.88 day/decade, respectively. The decrease in the number of days with light rain was more distinct than the decrease in the amount of light rain. (2) The decrease in the number of days with light rain was closely related to the decrease in the relative humidity caused by an increase in temperature and specific humidity. The trend in relative humidity resulting from an increase in temperature alone was −1.1%/decade, whereas the trend in relative humidity caused by an increase in specific humidity alone was 0.29%/decade. The trend in relative humidity was −0.76%/decade. The decrease in relative humidity was mainly a result of an increase in temperature. (3) The increase in temperature resulted in a decrease in the relative humidity and an increase in the surface evaporation. The increase in evaporation increased the specific humidity, which, in turn, increased the relative humidity. This compensated for the decrease in the relative humidity caused by the increase in the temperature and further decelerated the decrease in the number of days with light rain. • The number of summer days with light rain in the ESWC decreased significantly during 1961–2018. • The decrease in the number of days with light rain was closely related to the decrease in the relative humidity. • The trend of relative humidity made by an increase in temperature alone was −1.1%/decade. • The increase in evaporation compensated for the decrease in relative humidity caused by the increase in temperature. [ABSTRACT FROM AUTHOR]