Diurnal and seasonal variation, intensity, and structure of deep convective systems (DCSs; with 20-dBZecho tops exceeding 14 km) over the Tibetan Plateau–South Asian monsoon region from the Tibetan ...Plateau (TP) to the ocean are investigated using 14 yr of Tropical Rainfall Measuring Mission (TRMM) data. Four unique regions characterized by different orography are selected for comparison, including the TP, the southern Himalayan front (SHF), the South Asian subcontinent (SAS), and the ocean. DCSs and intense DCSs (IDCSs; with 40-dBZecho tops exceeding 10 km) occur more frequently over the continent than over the ocean. About 23% of total DCSs develop into IDCSs in the SHF, followed by the TP (21%) and the SAS (15%), with the least over the ocean (2%). The average 20-dBZecho-top height of IDCSs exceeds 16km and 9% of them even exceed 18 km. DCSs and IDCSs are the most frequent over the SHF, especially in the westernmost SHF, where the intensity—in terms of strong radar echo-top (viz., 40 dBZ) height, ice-particle content, and lightning flash rate—is the strongest. DCSs over the TP are relatively weak in convective intensity and small in size but occur frequently. Oceanic DCSs possess the tallest cloud top (which mainly reflects small ice particles) and the largest size, but their convective intensity is markedly weaker. DCSs and IDCSs show a similar diurnal variation, mainly occurring in the afternoon with a peak at 1600 local time over land. Although most of both DCSs and IDCSs occur between April and October, DCSs have a peak in August, whereas IDCSs have a peak in May.
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Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The Asian summer monsoon （ASM） anticyclone is a dominant feature of the circulation in the upper troposphere- lower stratosphere （UTLS） during boreal summer, which is found to have persistent maxima ...in carbon monoxide （CO）. This enhancement is due to the upward transport of air with high CO from the planetary boundary layer （PBL）, and confinement within the anticyclonic circulation. With rapid urbanization and industrialization, CO surface emissions are relatively high in the ASM region, especially in India and East China. To reveal the transport pathway of CO surface emissions over these two regions, and investigate the contribution of these to the CO distribution within the ASM anticyclone, a source sensitivity experiment was performed using the Weather Research and Forecasting （WRF） with chemistry model （WRF- Chem）. According to the experiment results, the CO within the ASM anticyclone mostly comes from India, while the contribution from East China is insignificant. The result is mainly caused by the different transportation mechanisms. In India, CO transportation is primarily affected by convection. The surface air with high CO over India is directly transported to the upper troposphere, and then confined within the ASM anticyclone, leading to a maximum value in the UTLS region. The CO transportation over East China is affected by deep convection and large-scale circulation, resulting mainly in transportation to Korea, Japan, and the North Pacific Ocean, with little upward transport to the anticyclone, leading to a high CO value at 215 hPa over these regions.
An enhanced aerosol layer near the tropopause over Asia during the June–September period of the Asian summer monsoon (ASM) was recently identified using satellite observations. Its sources and ...climate impact are presently not well-characterized. To improve understanding of this phenomenon, we made in situ aerosol measurements during summer 2015 from Kunming, China, then followed with a modeling study to assess the global significance. The in situ measurements revealed a robust enhancement in aerosol concentration that extended up to 2 km above the tropopause. A climate model simulation demonstrates that the abundant anthropogenic aerosol precursor emissions from Asia coupled with rapid vertical transport associated with monsoon convection leads to significant particle formation in the upper troposphere within the ASM anticyclone. These particles subsequently spread throughout the entire Northern Hemispheric (NH) lower stratosphere and contribute significantly (∼15%) to the NH stratospheric column aerosol surface area on an annual basis. This contribution is comparable to that from the sum of small volcanic eruptions in the period between 2000 and 2015. Although the ASM contribution is smaller than that from tropical upwelling (∼35%), we find that this region is about three times as efficient per unit area and time in populating the NH stratosphere with aerosol. With a substantial amount of organic and sulfur emissions in Asia, the ASM anticyclone serves as an efficient smokestack venting aerosols to the upper troposphere and lower stratosphere. As economic growth continues in Asia, the relative importance of Asian emissions to stratospheric aerosol is likely to increase.
Cadmium (Cd) is an important environmental pollutant that causes liver damage and induces nonalcoholic fatty liver disease (NAFLD). NAFLD is a fat accumulation disease and has significant effects on ...the body. Melatonin (Mel) is an endogenous protective molecule with antioxidant, anti-inflammatory, antiobesity, and antiaging effects. However, whether Mel can alleviate Cd-induced NAFLD and its mechanism remains unclear. First, in vivo, we found that Mel maintained mitochondrial structure and function, inhibited oxidative stress, and reduced Cd-induced liver injury. In addition, Mel alleviated lipid accumulation in the liver induced by Cd. In this process, Mel inhibits fatty acid production and promotes fatty acid oxidation. Interestingly, Mel regulated PPAR-α expression and alleviated Cd-induced autophagy blockade. In vitro model, the oil Red O staining, and WB results showed that Mel alleviated Cd-induced lipid accumulation. In addition, RAPA was used to activate autophagy to alleviate Cd-induced lipid accumulation, and TG was used to block autophagy flux to aggravate Cd-induced autophagy accumulation. After knocking down PPAR-α, the autophagosome fusion with lysosomes, and autophagic flux was inhibited and increased Cd-induced lipid accumulation. Mel alleviates mitochondrial damage and oxidative stress, and attenuates Cd-induced NAFLD by restoring the expression of PPAR-α and restoring autophagy flux.
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The Hunga Tonga–Hunga Ha’apai (Tonga) injected only small amount of SO2 into the stratosphere, while our analyses of the Microwave Limb Sounder (MLS) measurements show that a massive amount of water ...vapor was directly injected into the stratosphere by the Tonga eruption, which is probably due to its submarine volcanic activity. The Tonga eruption injected a total amount of 139 ± 8 Tg of water vapor into the stratosphere and resulted in an increase of 8.9 ± 0.5% in the global stratospheric water vapor. Analyses also show that the uppermost altitude impacted by Tonga reached the 1 hPa level (~47.6 km). Additionally, the maximum hydration region for increased water vapor is at 38–17 hPa (~22.2–27 km), where the water vapor mixing ratio increased by 6–8 ppmv during the three months after the Tonga eruption. The enhanced stratospheric water vapor has great potential to influence the global radiation budget as well as ozone loss.
Volcanic and wildfire events between 2014 and 2022 injected ∼3.2 Tg of sulfur dioxide and 0.8 Tg of smoke aerosols into the stratosphere. With injections at higher altitudes and lower latitudes, the ...simulated stratospheric lifetime of the 2014–2022 injections is about 50% longer than the volcanic 2005–2013 injections. The simulated global mean effective radiative forcing (ERF) of 2014–2022 is −0.18 W m−2, ∼40% of the ERF of the period of 1991–1999 with a large‐magnitude volcanic eruption (Pinatubo). Our climate model suggests that the stratospheric smoke aerosols generate ∼60% more negative ERF than volcanic sulfate per unit aerosol optical depth. Studies that fail to account for the different radiative properties of wildfire smoke relative to volcanic sulfate will likely underestimate the negative stratospheric forcings. Our analysis suggests that stratospheric injections offset 20% of the increase in global mean surface temperature between 2014–2022 and 1999–2002.
Plain Language Summary
Between 2014 and 2022, volcanic and wildfire events injected about ∼3.2 Tg of sulfur dioxide and 0.8 Tg of smoke aerosols into the stratosphere, about 30%–40% of injected mass of the 1991 Pinatubo eruption. Because the sulfur dioxide and smoke aerosols are injected at higher altitudes and lower latitudes, the simulated aerosol lifetime is 50% longer than the volcanic injections between 2005 and 2013, which have been suggested to play a role in the global warming hiatus. Our climate model suggests that smoke aerosol generates 60% more negative effective radiative forcing compared with volcanic sulfate aerosol per unit change in aerosol optical depth. Our study underscores the distinct optical properties between the wildfire smoke and sulfate aerosol. Our analysis finds that the trend of the global mean surface temperature in the two decades would have been 24% larger without the stratospheric injections.
Key Points
Long‐term balloon‐borne measurements of stratospheric aerosol over Tibetan Plateau and U.S. are compared with an aerosol‐climate model
Stratospheric smoke particles generate 60% more negative effective radiative forcing than volcanic sulfate with the same aerosol optical depth
Stratospheric aerosol abundance offsets 20% of the increase in the global mean surface temperature between 2014–2022 and 1999–2002
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•Cd induces Ca2+i elevation by activation of IP3 and influx of extracellular Ca2+ in OBs.•CaMKII is involved in activation of MAPK pathway induced by Cd in OBs.•CaMKⅡ participates in ...ER stress mediated apoptosis induced by Cd in OBs.
Ca2+ is an important ion in various intracellular metabolic pathways. Endoplasmic reticulum (ER) is a major intracellular calcium store and ER calcium homeostasis plays a key part in the regulation of apoptosis. We have previously shown that Cadmium (Cd) induces apoptosis in osteoblasts (OBs), accompany by increased cytoplasmic calcium. As the role of calcium in OBs apoptosis induced by Cd has not been clarified we investigated the effects of Cd exposure in rat OBs on intracellular Ca2+, CaMKII phosphorylation, and the pathways implicated in inducing apoptosis. The results showed that cadmium(Cd) induced elevation of intracellular Ca2+ (Ca2+i) in OBs by the release of Ca2+ from ER and the inflow of Ca2+ from the extracellular matrix. Cd induced Ca2+i elevation and phosphorylation of CaMKII which might be involved in activation of MAPKs and participated in Cd-induced mitochondrial apoptosis through the alteration of the ratio of Bax/Bcl-2 expression. Meanwhile, CaMKII phosphorylation activated unfolded protein response (UPR) during cadmium treatment and could enable the ER apoptosis pathway through the activation of caspase-12. These results indicated that CaMKII plays an important role in Cd induced ER apoptosis and MAPK activation. Our data provide new insights into the mechanisms underlying apoptosis in OBs following Cd exposure. This provides a theoretical basis for future investigations into the clinical therapeutic application of CaMKⅡ inhibitors in osteoporosis induced by Cd exposure.
Heavy summer precipitation over the southern slope of the Tibetan Plateau has dramatic influences on water resources and hydrological disasters in South Asia. It experienced increasing trends over ...1979–1996 and decreasing trends over 1996–2022, which are not yet well understood. Here we show observational and numerical evidence that stratospheric ozone has significant impacts on long‐term trends of summer precipitation in this strong convection area. It is found that stratospheric ozone depletion, by modulating the lower stratospheric temperature and upper‐tropospheric static stability, enhances deep convection and precipitation over the southern slope of the Tibetan Plateau. The results suggest that the ozone recovery in the future may reduce the summer precipitation over the southern slope of the Tibetan Plateau in the first half of the 21st century, which would be imperative for future water resource management in South Asia.
Plain Language Summary
South Asia, with a population of more than 1.8 billion, is among the most vulnerable regions in the world in response to climate change and a global hotspot for water security. Heavy summer precipitation over the southern slope of the Tibetan Plateau, which directly affects North India and Nepal with a population of more than 200 million and has dramatic influences on water resources and hydrological disasters in South Asia, experienced increasing trends over 1979–1996 and decreasing trends over 1996–2022 (Figure 1). We find that the long‐term variations of the summer precipitation are likely related to the stratospheric ozone depletion and recovery over the Tibetan Plateau in recent decades. The convective precipitation over the southern slope of the Tibetan Plateau is modulated by the upper tropospheric static stability which is affected by the lower‐stratospheric temperature. We find that stratospheric ozone depletion, which radiatively cools the lower stratosphere, enhances the deep convection and precipitation. This work helps to understand the stratospheric contributions to the changes in the summer precipitation over the southern slope of the Tibetan Plateau and future water resource management in South Asia.
Key Points
Trends in heavy summer precipitation over the southern slope of the Tibetan Plateau are positive in 1979–1996 and negative in 1996–2022
Stratospheric ozone depletion led to lower stratospheric cooling and a reduction of upper‐tropospheric static stability
Stratospheric ozone depletion enhanced the deep convection and precipitation over the southern slope of the Tibetan Plateau
Abstract
Surface ultraviolet (UV) radiation has important effects on human health, terrestrial and aquatic ecosystems, and air pollution. Both stratospheric ozone and clouds are key factors that ...influence surface UV radiation. Here we find that Arctic ozone loss may lead to a decrease in surface UV radiation over the Siberian Arctic in spring using ERA5 reanalysis. It is found that Arctic ozone loss is associated with an increase in high clouds by modifying static stability in the upper troposphere. Stratospheric ozone loss allows more UV radiation to reach the surface. On the contrary, the increase in high clouds results in a reduction of surface UV radiation. Interestingly, a composite analysis suggests that this cloud masking effect is found to be stronger than that from stratospheric ozone loss over the Siberian Arctic in spring. These results suggest that we should pay more attention to the high-ozone events which would lead to more surface UV radiation by the cloud effects.
Cadmium is an environmental pollutant that threatens the health of both humans and animals. Current studies have shown that while hepatotoxic damage induced by cadmium is closely related to ...autophagy, its intrinsic mechanism has not been elucidated. MicroRNA plays a regulatory role on different stages of autophagy. In this study, we investigated the mechanisms by which microRNA-155 (miR-155) regulate cadmium-induced hepatotoxicity in rat hepatocytes (BRL 3A cells) and in vivo. We found that cadmium exposure could cause liver injury in rats, resulting in a decreased liver index, increased alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) activity, hepatocyte steatosis, and ultrastructure damage. Cadmium exposure also induced autophagy in hepatocytes, resulting in increased expression of ATG5, Belin1, LC3II, and an increased number of autophagosomes. In addition, cadmium exposure upregulated miR-155 expression, downregulated Rheb mRNA expression, and downregulated the level of protein expression in the Rheb/mTOR signaling pathway in rat hepatocytes. The overexpression of miR-155 followed by cadmium exposure upregulated the level of autophagy in BRL3A cells, whereas miR-155 inhibition had the opposite effect. In addition, miR-155 negatively regulated Rheb. A dual-luciferase reporter assay verified the negative regulatory effect of miR-155 on Rheb targeting. Knockdown of Rheb downregulated cadmium-induced autophagy. Therefore, the Rheb/mTOR signaling can negatively regulate autophagy. The present study demonstrates that miR-155 promotes cadmium-induced autophagy in rat hepatocytes by suppressing Rheb expression.
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•Cadmium induces hepatocyte autophagy.•Cadmium upregulates miR-155 expression and downregulates Rheb/mTOR signaling.•MiR-155 promotes autophagy by suppressing Rheb expression.
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