T. M. McHardy, David A. Peterson, Jason M. Apke, Steven D. Miller, James R. Campbell, E. Hyer
Convective dynamics in a supercell thunderstorm, a volcanic eruption, and two pyrocumulonimbus (pyroCb) events are compared by computing cloud‐top divergence (CTD) with an optical flow technique called Deepflow. Visible 0.64‐μm imagery sequences from Geostationary Operational Environmental Satellites (GOES)‐R series Advanced Baseline Imager (ABI) are used as input into the optical flow algorithm. CTD is computed after post‐processing of the retrieved motions. Analysis is performed on specific image times, as well as the full time series of each case. Multiple CTD‐based parameters, such as the maximum and the two‐dimensional area exceeding a specified CTD threshold, are examined along with the optical flow‐retrieved wind speed. CTD is shown to accurately and quantitatively represent the behavior and magnitude of different deep convective phenomena, including distinguishing between convective pulses within each individual event. CTD captures updraft intensification as well as differences in convective activity between two pyroCb events and individual updraft pulses occurring within a single pyroCb event. Finally, the characteristics of high‐altitude smoke plumes injected by two separate pyroCb pulses are linked to CTD using ultraviolet aerosol index and satellite imagery. Optical flow‐derived parameters can therefore be applied to individual pyroCbs in real‐time, with potential to characterize pyroCb smoke source inputs for downstream smoke modeling applications and to facilitate future tools supporting air quality modeling and firefighting efforts.
{"title":"Novel Comparison of Pyrocumulonimbus Updrafts to Volcanic Eruptions and Supercell Thunderstorms Using Optical Flow Techniques","authors":"T. M. McHardy, David A. Peterson, Jason M. Apke, Steven D. Miller, James R. Campbell, E. Hyer","doi":"10.1029/2023jd039418","DOIUrl":"https://doi.org/10.1029/2023jd039418","url":null,"abstract":"Convective dynamics in a supercell thunderstorm, a volcanic eruption, and two pyrocumulonimbus (pyroCb) events are compared by computing cloud‐top divergence (CTD) with an optical flow technique called Deepflow. Visible 0.64‐μm imagery sequences from Geostationary Operational Environmental Satellites (GOES)‐R series Advanced Baseline Imager (ABI) are used as input into the optical flow algorithm. CTD is computed after post‐processing of the retrieved motions. Analysis is performed on specific image times, as well as the full time series of each case. Multiple CTD‐based parameters, such as the maximum and the two‐dimensional area exceeding a specified CTD threshold, are examined along with the optical flow‐retrieved wind speed. CTD is shown to accurately and quantitatively represent the behavior and magnitude of different deep convective phenomena, including distinguishing between convective pulses within each individual event. CTD captures updraft intensification as well as differences in convective activity between two pyroCb events and individual updraft pulses occurring within a single pyroCb event. Finally, the characteristics of high‐altitude smoke plumes injected by two separate pyroCb pulses are linked to CTD using ultraviolet aerosol index and satellite imagery. Optical flow‐derived parameters can therefore be applied to individual pyroCbs in real‐time, with potential to characterize pyroCb smoke source inputs for downstream smoke modeling applications and to facilitate future tools supporting air quality modeling and firefighting efforts.","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141798920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Iron (Fe) has profound impacts on Earth's ecosystem and global biogeochemical cycles. Fe deposited onto glacier surfaces reduces snow and ice albedo, thereby accelerating glacier melting, and supplying downstream ecosystems with dissolved Fe. However, the origins of atmospheric Fe deposition in glacier regions of western China remain unclear. This study presents novel insights into Fe isotopic composition (refer to δ56Fe) and origins, gained from geochemical analysis of large‐scale cryoconite samples collected from glaciers in western China, which encompass the Tibetan Plateau (TP) and the Tianshan Mountains. Results showed that cryoconite δ56Fe ranged from −1.06 ± 0.07‰ to 0.33 ± 0.04‰, regardless of their concentration. Moreover, anomalous δ56Fe values deviating significantly from the upper continental crust values (with an average of 0.09‰) were detected, indicating a significant impact of anthropogenic Fe materials on the investigated glaciers. This impact was particularly prominent in the margin regions of the TP and its surroundings, but was less apparent in the interior and southern of the plateau. Using MixSIAR isotope mixing model, we determined that coal combustion and other anthropogenic combustion sources (such as liquid fuel combustion and steel smelting) contributed to cryoconite Fe in the range of 6.9%–43.1% and 0.8%–23.4%, respectively. Among these, coal combustion was the predominant anthropogenic source of cryoconite Fe in western China's glaciers. Compared with other sink areas in the Northern Hemisphere, glaciers in western China are obviously affected by anthropogenically sourced Fe. This study has significant implications for understanding glacier‐fed downstream ecosystems and the regional biogeochemical cycle.
{"title":"Using Iron Stable Isotopes to Quantify the Origins of the Cryoconite Iron Materials in Western China and Exploring Controlling Factors","authors":"Zhiwen Dong, Ting Wei, E. Parteli, Xiaoli Liu, Jiawen Ren, Yaping Shao","doi":"10.1029/2023jd040711","DOIUrl":"https://doi.org/10.1029/2023jd040711","url":null,"abstract":"Iron (Fe) has profound impacts on Earth's ecosystem and global biogeochemical cycles. Fe deposited onto glacier surfaces reduces snow and ice albedo, thereby accelerating glacier melting, and supplying downstream ecosystems with dissolved Fe. However, the origins of atmospheric Fe deposition in glacier regions of western China remain unclear. This study presents novel insights into Fe isotopic composition (refer to δ56Fe) and origins, gained from geochemical analysis of large‐scale cryoconite samples collected from glaciers in western China, which encompass the Tibetan Plateau (TP) and the Tianshan Mountains. Results showed that cryoconite δ56Fe ranged from −1.06 ± 0.07‰ to 0.33 ± 0.04‰, regardless of their concentration. Moreover, anomalous δ56Fe values deviating significantly from the upper continental crust values (with an average of 0.09‰) were detected, indicating a significant impact of anthropogenic Fe materials on the investigated glaciers. This impact was particularly prominent in the margin regions of the TP and its surroundings, but was less apparent in the interior and southern of the plateau. Using MixSIAR isotope mixing model, we determined that coal combustion and other anthropogenic combustion sources (such as liquid fuel combustion and steel smelting) contributed to cryoconite Fe in the range of 6.9%–43.1% and 0.8%–23.4%, respectively. Among these, coal combustion was the predominant anthropogenic source of cryoconite Fe in western China's glaciers. Compared with other sink areas in the Northern Hemisphere, glaciers in western China are obviously affected by anthropogenically sourced Fe. This study has significant implications for understanding glacier‐fed downstream ecosystems and the regional biogeochemical cycle.","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141798457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Evelyn Workman, Rebecca E. Fisher, James L. France, Katrin Linse, Mingxi Yang, Thomas Bell, Yuanxu Dong, Anna E. Jones
Sea-air methane flux was measured directly by the eddy-covariance method across approximately 60,000 km of Arctic and Antarctic cruises during a number of summers. The Arctic Ocean (north of 60°N, between 20°W and 50°E) and Southern Ocean (south of 50°S, between 70°W and 30°E) are found to be on-shelf sources of atmospheric methane with mean sea-air fluxes of 9.17 ± 2.91 (SEM (standard error of the mean)) μmol m−2 d−1 and 8.98 ± 0.91 μmol m−2 d−1, respectively. Off-shelf, this region of the Arctic Ocean is found to be a source of methane (mean flux of 2.39 ± 0.68 μmol m−2 d−1), while this region of the Southern Ocean is found to be a methane sink (mean flux of −0.77 ± 0.37 μmol m−2 d−1). The highest fluxes observed are found around west Svalbard, South Georgia, and South Shetland Islands and Bransfield Strait; areas with evidence of the presence of methane flares emanating from the seabed. Hence, this study may provide evidence of direct emission of seabed methane to the atmosphere in both the Arctic and Antarctic. Comparing with previous studies, the results of this study may indicate an increase in sea-air flux of methane in areas with seafloor seepage over timescales of several decades. As climate change exacerbates rising water temperatures, continued monitoring of methane release from polar oceans into the future is crucial.
{"title":"Methane Emissions From Seabed to Atmosphere in Polar Oceans Revealed by Direct Methane Flux Measurements","authors":"Evelyn Workman, Rebecca E. Fisher, James L. France, Katrin Linse, Mingxi Yang, Thomas Bell, Yuanxu Dong, Anna E. Jones","doi":"10.1029/2023jd040632","DOIUrl":"https://doi.org/10.1029/2023jd040632","url":null,"abstract":"Sea-air methane flux was measured directly by the eddy-covariance method across approximately 60,000 km of Arctic and Antarctic cruises during a number of summers. The Arctic Ocean (north of 60°N, between 20°W and 50°E) and Southern Ocean (south of 50°S, between 70°W and 30°E) are found to be on-shelf sources of atmospheric methane with mean sea-air fluxes of 9.17 ± 2.91 (SEM (standard error of the mean)) μmol m<sup>−2</sup> d<sup>−1</sup> and 8.98 ± 0.91 μmol m<sup>−2</sup> d<sup>−1</sup>, respectively. Off-shelf, this region of the Arctic Ocean is found to be a source of methane (mean flux of 2.39 ± 0.68 μmol m<sup>−2</sup> d<sup>−1</sup>), while this region of the Southern Ocean is found to be a methane sink (mean flux of −0.77 ± 0.37 μmol m<sup>−2</sup> d<sup>−1</sup>). The highest fluxes observed are found around west Svalbard, South Georgia, and South Shetland Islands and Bransfield Strait; areas with evidence of the presence of methane flares emanating from the seabed. Hence, this study may provide evidence of direct emission of seabed methane to the atmosphere in both the Arctic and Antarctic. Comparing with previous studies, the results of this study may indicate an increase in sea-air flux of methane in areas with seafloor seepage over timescales of several decades. As climate change exacerbates rising water temperatures, continued monitoring of methane release from polar oceans into the future is crucial.","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":4.4,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141784583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Spring Predictability Barrier (SPB) phenomenon is characterized by the reduced accuracy of El Niño/Southern Oscillation (ENSO) forecasts during the spring, which substantially limits our ability to predict ENSO events. By investigating the nonlinear dynamic characteristics of ENSO systems simulated by a box model, we found that the strong surface heating process in spring may contribute to the SPB by regulating the different coupling processes between the ocean and atmosphere. Specifically, the intensified springtime surface heating increases the Sea Surface Temperature (SST), further amplifying the thermal damping effect of SST anomalies and reducing the dynamic connection between zonal SST gradient and upwelling process, and finally increasing the chaotic degree of ENSO systems simulated by the box model. The enhanced chaotic degree of ENSO systems leads to a more rapid growth of initial errors in the forecast model in spring, potentially leading to the SPB phenomenon.
{"title":"The Potential Role of Seasonal Surface Heating on the Chaotic Origins of the El Niño/Southern Oscillation Spring Predictability Barrier","authors":"Dakuan Yu, Meng Zhou, Chaoxun Hang","doi":"10.1029/2024jd041034","DOIUrl":"https://doi.org/10.1029/2024jd041034","url":null,"abstract":"The Spring Predictability Barrier (SPB) phenomenon is characterized by the reduced accuracy of El Niño/Southern Oscillation (ENSO) forecasts during the spring, which substantially limits our ability to predict ENSO events. By investigating the nonlinear dynamic characteristics of ENSO systems simulated by a box model, we found that the strong surface heating process in spring may contribute to the SPB by regulating the different coupling processes between the ocean and atmosphere. Specifically, the intensified springtime surface heating increases the Sea Surface Temperature (SST), further amplifying the thermal damping effect of SST anomalies and reducing the dynamic connection between zonal SST gradient and upwelling process, and finally increasing the chaotic degree of ENSO systems simulated by the box model. The enhanced chaotic degree of ENSO systems leads to a more rapid growth of initial errors in the forecast model in spring, potentially leading to the SPB phenomenon.","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":4.4,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141784435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Daily mean albedo, a crucial variable of the earth radiation budget, is significantly affected by the diurnal variation of land surface albedo (DVLSA). The DVLSA typically exhibits asymmetry, thereby affecting the estimation of the daily mean albedo. However, the asymmetry in the DVLSA is generally ignored in daily mean albedo estimation. In this study, we investigated the influencing factors of the asymmetry in the DVLSA and evaluated its impacts on estimating the daily mean albedo based on field observations and simulated data. Our findings reveal that the asymmetry in the DVLSA varies among land cover types, with forests exhibiting more pronounced asymmetry compared to croplands, grasslands, and bare soil. The diurnal variation of the atmospheric conditions is the primary factor controlling the asymmetry in the DVLSA, with that of land surface conditions being a secondary factor. Neglecting the asymmetry in the DVLSA leads to estimation error in daily mean albedo, particularly pronounced during winter. The relative error of daily mean albedo can exceed 10% when the mean asymmetry index of diffuse irradiance fraction reaches 40%. However, the DVLSA retrieved from the satellite Bidirectional Reflectance Distribution Function product inadequately captures asymmetry, resulting in a relative error of approximately 13.7% in estimating daily mean albedo.
{"title":"Asymmetry in the Diurnal Variation of Land Surface Albedo and Its Impacts on Daily Mean Albedo Estimation","authors":"Yuan Han, Jianguang Wen, Qing Xiao, Dongqin You, Lei Meng, Shengbiao Wu, Dalei Hao, Yong Tang, Xi Chen, Qinhuo Liu, Congcong Zhao","doi":"10.1029/2023jd039728","DOIUrl":"https://doi.org/10.1029/2023jd039728","url":null,"abstract":"Daily mean albedo, a crucial variable of the earth radiation budget, is significantly affected by the diurnal variation of land surface albedo (DVLSA). The DVLSA typically exhibits asymmetry, thereby affecting the estimation of the daily mean albedo. However, the asymmetry in the DVLSA is generally ignored in daily mean albedo estimation. In this study, we investigated the influencing factors of the asymmetry in the DVLSA and evaluated its impacts on estimating the daily mean albedo based on field observations and simulated data. Our findings reveal that the asymmetry in the DVLSA varies among land cover types, with forests exhibiting more pronounced asymmetry compared to croplands, grasslands, and bare soil. The diurnal variation of the atmospheric conditions is the primary factor controlling the asymmetry in the DVLSA, with that of land surface conditions being a secondary factor. Neglecting the asymmetry in the DVLSA leads to estimation error in daily mean albedo, particularly pronounced during winter. The relative error of daily mean albedo can exceed 10% when the mean asymmetry index of diffuse irradiance fraction reaches 40%. However, the DVLSA retrieved from the satellite Bidirectional Reflectance Distribution Function product inadequately captures asymmetry, resulting in a relative error of approximately 13.7% in estimating daily mean albedo.","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":4.4,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141784585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. R. Schoeberl, Y. Wang, G. Taha, D. J. Zawada, R. Ueyama, A. Dessler
We calculate the climate forcing for the 2 ys after the 15 January 2022, Hunga Tonga-Hunga Ha'apai (Hunga) eruption. We use satellite observations of stratospheric aerosols, trace gases and temperatures to compute the tropopause radiative flux changes relative to climatology. Overall, the net downward radiative flux decreased compared to climatology. The Hunga stratospheric water vapor anomaly initially increases the downward infrared radiative flux, but this forcing diminishes as the anomaly disperses. The Hunga aerosols cause a solar flux reduction that dominates the net flux change over most of the 2 yrs period. Hunga induced temperature changes produce a decrease in downward long-wave flux. Hunga induced ozone reduction increases the short-wave downward flux creating small sub-tropical increase in total flux from mid-2022 to 2023. By the end of 2023, most of the Hunga induced radiative forcing changes have disappeared. There is some disagreement in the satellite measured stratospheric aerosol optical depth (SAOD) observations which we view as a measure of the uncertainty; however, the SAOD uncertainty does not alter our conclusion that, overall, aerosols dominate the radiative flux changes.
{"title":"Evolution of the Climate Forcing During the Two Years After the Hunga Tonga-Hunga Ha'apai Eruption","authors":"M. R. Schoeberl, Y. Wang, G. Taha, D. J. Zawada, R. Ueyama, A. Dessler","doi":"10.1029/2024jd041296","DOIUrl":"https://doi.org/10.1029/2024jd041296","url":null,"abstract":"We calculate the climate forcing for the 2 ys after the 15 January 2022, Hunga Tonga-Hunga Ha'apai (Hunga) eruption. We use satellite observations of stratospheric aerosols, trace gases and temperatures to compute the tropopause radiative flux changes relative to climatology. Overall, the net downward radiative flux decreased compared to climatology. The Hunga stratospheric water vapor anomaly initially increases the downward infrared radiative flux, but this forcing diminishes as the anomaly disperses. The Hunga aerosols cause a solar flux reduction that dominates the net flux change over most of the 2 yrs period. Hunga induced temperature changes produce a decrease in downward long-wave flux. Hunga induced ozone reduction increases the short-wave downward flux creating small sub-tropical increase in total flux from mid-2022 to 2023. By the end of 2023, most of the Hunga induced radiative forcing changes have disappeared. There is some disagreement in the satellite measured stratospheric aerosol optical depth (SAOD) observations which we view as a measure of the uncertainty; however, the SAOD uncertainty does not alter our conclusion that, overall, aerosols dominate the radiative flux changes.","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":4.4,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141784589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Christian P. Lackner, Bart Geerts, Timothy W. Juliano, Branko Kosovic, Lulin Xue
During marine cold-air outbreaks (MCAOs), when cold polar air moves over warmer ocean, a well-recognized cloud pattern develops, with open or closed mesoscale cellular convection (MCC) at larger fetch over open water. The Cold-Air Outbreaks in the Marine Boundary Layer Experiment provided a comprehensive set of ground-based in situ and remote sensing observations of MCAOs at a coastal location in northern Norway. MCAO periods that unambiguously exhibit open or closed MCC are determined. Individual cells observed with a profiling Ka-band radar are identified using a watershed segmentation method. Using self-organizing maps (SOMs), these cells are then objectively classified based on the variability in their vertical structure. The SOM nodes contain some information about the location of the cell transect relative to the center of the MCC. This adds classification noise, requiring numerous cell transects to isolate cell dynamical information. The SOM-based classification shows that comparatively intense convection occurs only in open MCC. This convection undergoes an apparent lifecycle. Developing cells are associated with stronger updrafts, large spectrum width, larger amounts of liquid water, lower surface precipitation rates, and lower cloud tops than mature and weakening cells. The weakening of these cells is associated with the development of precipitation-induced cold pools. The SOM classification also reveals less intense convection, with a similar lifecycle. More stratiform vertical cloud structures with weak vertical motions are common during closed MCC periods and are separated into precipitating and non-precipitating stratiform cores. Convection is observed only occasionally in the closed MCC environment.
在海洋冷空气爆发（MCAOs）期间，当极地冷空气移动到较暖的海洋上空时，会形成一种公认的云模式，在开阔水域的较大风口处出现开放或封闭的中尺度细胞对流（MCC）。海洋边界层冷空气爆发实验提供了一套全面的挪威北部沿海 MCAO 地面原位和遥感观测数据。确定了明确显示开放或封闭 MCC 的 MCAO 时段。利用分水岭分割方法，确定了用 Ka 波段雷达观测到的单个单元。然后使用自组织图（SOM），根据垂直结构的变化对这些小区进行客观分类。自组织图节点包含一些有关小区横断面相对于 MCC 中心位置的信息。这就增加了分类噪音，需要大量的单元横断面来分离单元动态信息。基于 SOM 的分类显示，只有在开放的 MCC 中才会出现相对强烈的对流。这种对流经历了一个明显的生命周期。与成熟和减弱的小区相比，发展中的小区具有较强的上升气流、较大的频谱宽度、较多的液态水、较低的地表降水率和较低的云顶。这些细胞的减弱与降水引起的冷池的发展有关。SOM 分类也显示对流强度较低，但生命周期相似。更多的层状垂直云结构具有微弱的垂直运动，在封闭的 MCC 期间很常见，并分为降水层状核心和非降水层状核心。在封闭的 MCC 环境中偶尔会观测到对流。
{"title":"Characterizing Mesoscale Cellular Convection in Marine Cold Air Outbreaks With a Machine Learning Approach","authors":"Christian P. Lackner, Bart Geerts, Timothy W. Juliano, Branko Kosovic, Lulin Xue","doi":"10.1029/2024jd041651","DOIUrl":"https://doi.org/10.1029/2024jd041651","url":null,"abstract":"During marine cold-air outbreaks (MCAOs), when cold polar air moves over warmer ocean, a well-recognized cloud pattern develops, with open or closed mesoscale cellular convection (MCC) at larger fetch over open water. The Cold-Air Outbreaks in the Marine Boundary Layer Experiment provided a comprehensive set of ground-based in situ and remote sensing observations of MCAOs at a coastal location in northern Norway. MCAO periods that unambiguously exhibit open or closed MCC are determined. Individual cells observed with a profiling Ka-band radar are identified using a watershed segmentation method. Using self-organizing maps (SOMs), these cells are then objectively classified based on the variability in their vertical structure. The SOM nodes contain some information about the location of the cell transect relative to the center of the MCC. This adds classification noise, requiring numerous cell transects to isolate cell dynamical information. The SOM-based classification shows that comparatively intense convection occurs only in open MCC. This convection undergoes an apparent lifecycle. Developing cells are associated with stronger updrafts, large spectrum width, larger amounts of liquid water, lower surface precipitation rates, and lower cloud tops than mature and weakening cells. The weakening of these cells is associated with the development of precipitation-induced cold pools. The SOM classification also reveals less intense convection, with a similar lifecycle. More stratiform vertical cloud structures with weak vertical motions are common during closed MCC periods and are separated into precipitating and non-precipitating stratiform cores. Convection is observed only occasionally in the closed MCC environment.","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":4.4,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141784675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nadja Landshuter, Franziska Aemisegger, Thomas Mölg
Stratiform and convective precipitation are known to be associated with distinct isotopic fingerprints in the tropics. Such rain type specific isotope signals are of key importance for climate reconstructions derived from climate proxies (e.g., stable isotopes in tree rings). Recently, the relation between rain type and isotope signal in present-day climate has been intensively discussed. While some studies point out the importance of deep convection, other studies emphasize the role of stratiform precipitation for strongly depleted isotope signals in precipitation. Uncertainties arise from observational studies due to data scarcity while modeling approaches with global climate models cannot explicitly resolve convective processes and rely on parameterizations. High-resolution climate models are particularly important for studies over complex topography and for the simulation of convective cloud formation and organization. Therefore, we applied the isotope-enabled version of the high-resolution climate model from the Consortium for Small-Scale Modeling (COSMOiso) over the Andes of tropical south Ecuador, South America, to investigate the influence of stratiform and convective rain on the stable oxygen isotope signal of precipitation (δ18OP). Our results highlight the importance of deep convection for depleting the isotopic signal of precipitation and increasing its deuterium excess. Due to the opposing effect of shallow and deep convection on the δ18OP signal, the use of a stratiform fraction might be misleading. We therefore propose to use a shallow and deep convective fraction to analyze the effect of rain types on δ18OP.
{"title":"Stable Water Isotope Signals and Their Relation to Stratiform and Convective Precipitation in the Tropical Andes","authors":"Nadja Landshuter, Franziska Aemisegger, Thomas Mölg","doi":"10.1029/2023jd040630","DOIUrl":"https://doi.org/10.1029/2023jd040630","url":null,"abstract":"Stratiform and convective precipitation are known to be associated with distinct isotopic fingerprints in the tropics. Such rain type specific isotope signals are of key importance for climate reconstructions derived from climate proxies (e.g., stable isotopes in tree rings). Recently, the relation between rain type and isotope signal in present-day climate has been intensively discussed. While some studies point out the importance of deep convection, other studies emphasize the role of stratiform precipitation for strongly depleted isotope signals in precipitation. Uncertainties arise from observational studies due to data scarcity while modeling approaches with global climate models cannot explicitly resolve convective processes and rely on parameterizations. High-resolution climate models are particularly important for studies over complex topography and for the simulation of convective cloud formation and organization. Therefore, we applied the isotope-enabled version of the high-resolution climate model from the Consortium for Small-Scale Modeling (COSMO<sub>iso</sub>) over the Andes of tropical south Ecuador, South America, to investigate the influence of stratiform and convective rain on the stable oxygen isotope signal of precipitation (δ<sup>18</sup>O<sub>P</sub>). Our results highlight the importance of deep convection for depleting the isotopic signal of precipitation and increasing its deuterium excess. Due to the opposing effect of shallow and deep convection on the δ<sup>18</sup>O<sub>P</sub> signal, the use of a stratiform fraction might be misleading. We therefore propose to use a shallow and deep convective fraction to analyze the effect of rain types on δ<sup>18</sup>O<sub>P</sub>.","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":4.4,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141784584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Eric Saboya, Alistair J. Manning, Peter Levy, Kieran M. Stanley, Joseph Pitt, Dickon Young, Daniel Say, Aoife Grant, Tim Arnold, Chris Rennick, Samuel J. Tomlinson, Edward J. Carnell, Yuri Artoli, Ann Stavart, T. Gerard Spain, Simon O’Doherty, Matthew Rigby, Anita L. Ganesan
Atmospheric trace gas measurements can be used to independently assess national greenhouse gas inventories through inverse modeling. Atmospheric nitrous oxide (N2O) measurements made in the United Kingdom (UK) and Republic of Ireland are used to derive monthly N2O emissions for 2013–2022 using two different inverse methods. We find mean UK emissions of 90.5 ± 23.0 (1σ) and 111.7 ± 32.1 (1σ) Gg N2O yr−1 for 2013–2022, and corresponding trends of −0.68 ± 0.48 (1σ) Gg N2O yr−2 and −2.10 ± 0.72 (1σ) Gg N2O yr−2, respectively, for the two inverse methods. The UK National Atmospheric Emissions Inventory (NAEI) reported mean N2O emissions of 73.9 ± 1.7 (1σ) Gg N2O yr−1 across this period, which is 22%–51% smaller than the emissions derived from atmospheric data. We infer a pronounced seasonal cycle in N2O emissions, with a peak occurring in the spring and a second smaller peak in the late summer for certain years. The springtime peak has a long seasonal decline that contrasts with the sharp rise and fall of N2O emissions estimated from the bottom-up UK Emissions Model (UKEM). Bayesian inference is used to minimize the seasonal cycle mismatch between the average top-down (atmospheric data-based) and bottom-up (process model and inventory-based) seasonal emissions at a sub-sector level. Increasing agricultural manure management and decreasing synthetic fertilizer N2O emissions reduces some of the discrepancy between the average top-down and bottom-up seasonal cycles. Other possibilities could also explain these discrepancies, such as missing emissions from NH3 deposition, but these require further investigation.
{"title":"Combining Top-Down and Bottom-Up Approaches to Evaluate Recent Trends and Seasonal Patterns in UK N2O Emissions","authors":"Eric Saboya, Alistair J. Manning, Peter Levy, Kieran M. Stanley, Joseph Pitt, Dickon Young, Daniel Say, Aoife Grant, Tim Arnold, Chris Rennick, Samuel J. Tomlinson, Edward J. Carnell, Yuri Artoli, Ann Stavart, T. Gerard Spain, Simon O’Doherty, Matthew Rigby, Anita L. Ganesan","doi":"10.1029/2024jd040785","DOIUrl":"https://doi.org/10.1029/2024jd040785","url":null,"abstract":"Atmospheric trace gas measurements can be used to independently assess national greenhouse gas inventories through inverse modeling. Atmospheric nitrous oxide (N<sub>2</sub>O) measurements made in the United Kingdom (UK) and Republic of Ireland are used to derive monthly N<sub>2</sub>O emissions for 2013–2022 using two different inverse methods. We find mean UK emissions of 90.5 ± 23.0 (1<i>σ</i>) and 111.7 ± 32.1 (1<i>σ</i>) Gg N<sub>2</sub>O yr<sup>−1</sup> for 2013–2022, and corresponding trends of −0.68 ± 0.48 (1<i>σ</i>) Gg N<sub>2</sub>O yr<sup>−2</sup> and −2.10 ± 0.72 (1<i>σ</i>) Gg N<sub>2</sub>O yr<sup>−2</sup>, respectively, for the two inverse methods. The UK National Atmospheric Emissions Inventory (NAEI) reported mean N<sub>2</sub>O emissions of 73.9 ± 1.7 (1<i>σ</i>) Gg N<sub>2</sub>O yr<sup>−1</sup> across this period, which is 22%–51% smaller than the emissions derived from atmospheric data. We infer a pronounced seasonal cycle in N<sub>2</sub>O emissions, with a peak occurring in the spring and a second smaller peak in the late summer for certain years. The springtime peak has a long seasonal decline that contrasts with the sharp rise and fall of N<sub>2</sub>O emissions estimated from the bottom-up UK Emissions Model (UKEM). Bayesian inference is used to minimize the seasonal cycle mismatch between the average top-down (atmospheric data-based) and bottom-up (process model and inventory-based) seasonal emissions at a sub-sector level. Increasing agricultural manure management and decreasing synthetic fertilizer N<sub>2</sub>O emissions reduces some of the discrepancy between the average top-down and bottom-up seasonal cycles. Other possibilities could also explain these discrepancies, such as missing emissions from NH<sub>3</sub> deposition, but these require further investigation.","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":4.4,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141784588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the context of China's “dual carbon” goal, emissions of air pollutants are expected to significantly decrease in the future. Thus, the direct climate effects of black carbon (BC) aerosols in East Asia are investigated under this goal using an updated regional climate and chemistry model. The simulated annual average BC concentration over East Asia is approximately 1.29 μg/m3 in the last decade. Compared to those in 2010–2020, both the BC column burden and instantaneous direct radiative forcing in East Asia decrease by more than 55% and 80%, respectively, in the carbon peak year (2030s) and the carbon neutrality year (2060s). Conversely, the BC effective radiative forcing (ERF) and regional climate responses to BC exhibit substantial nonlinearity to emission reduction, possibly resulting from different adjustments of thermal-dynamic fields and clouds from BC-radiation interactions. The regional mean BC ERF at the tropopause over East Asia is approximately +1.11 W/m2 in 2010–2020 while negative in the 2060s. BC-radiation interactions in the present-day impose a significant annual mean cooling of −0.2 to −0.5 K in central China but warming +0.3 K in the Tibetan Plateau. As China's BC emissions decline, surface temperature responses show a mixed picture compared to 2010–2020, with more cooling in eastern China and Tibet of −0.2 to −0.3 K in the 2030s, but more warming in central China of approximately +0.3 K by the 2060s. The Indian BC might play a more important role in East Asian climate with reduction of BC emissions in China.
在中国 "双碳 "目标的背景下，预计未来空气污染物的排放量将大幅减少。因此，在这一目标下，利用更新的区域气候和化学模型研究了东亚地区黑碳气溶胶对气候的直接影响。在过去十年中，东亚上空的模拟年均 BC 浓度约为 1.29 μg/m3 。与2010-2020年相比，在碳峰值年（2030年代）和碳中和年（2060年代），东亚的BC柱负荷和瞬时直接辐射强迫分别减少了55%和80%以上。相反，BC 有效辐射强迫（ERF）和区域气候对 BC 的响应对减排表现出很大的非线性，这可能是由于 BC 辐射相互作用对热动力场和云层的不同调整造成的。东亚对流层顶的区域平均 BC ERF 在 2010-2020 年约为 +1.11 W/m2，而在 2060 年代为负值。目前，BC-辐射相互作用在华中地区造成了显著的年平均降温-0.2 到-0.5 K，而在青藏高原则造成了+0.3 K的升温。与 2010-2020 年相比，随着中国 BC 排放量的减少，地表温度的响应也会有所变化，到 2030 年代，中国东部和西藏的降温幅度会更大，为-0.2 到-0.3 K，但到 2060 年代，中国中部的升温幅度会更大，约为+0.3 K。随着中国 BC 排放的减少，印度 BC 可能会在东亚气候中发挥更重要的作用。
{"title":"Changes in the Direct Climate Effect of Black Carbon Aerosols in East Asia Under the “Dual Carbon” Goal of China","authors":"Peng Gao, Yiman Gao, Yinan Zhou, Heng Cao, Yaxin Hu, Shu Li, Shanrong Liang, Tijian Wang, Min Xie, Mengmeng Li, Bingliang Zhuang","doi":"10.1029/2024jd040874","DOIUrl":"https://doi.org/10.1029/2024jd040874","url":null,"abstract":"In the context of China's “dual carbon” goal, emissions of air pollutants are expected to significantly decrease in the future. Thus, the direct climate effects of black carbon (BC) aerosols in East Asia are investigated under this goal using an updated regional climate and chemistry model. The simulated annual average BC concentration over East Asia is approximately 1.29 μg/m<sup>3</sup> in the last decade. Compared to those in 2010–2020, both the BC column burden and instantaneous direct radiative forcing in East Asia decrease by more than 55% and 80%, respectively, in the carbon peak year (2030s) and the carbon neutrality year (2060s). Conversely, the BC effective radiative forcing (ERF) and regional climate responses to BC exhibit substantial nonlinearity to emission reduction, possibly resulting from different adjustments of thermal-dynamic fields and clouds from BC-radiation interactions. The regional mean BC ERF at the tropopause over East Asia is approximately +1.11 W/m<sup>2</sup> in 2010–2020 while negative in the 2060s. BC-radiation interactions in the present-day impose a significant annual mean cooling of −0.2 to −0.5 K in central China but warming +0.3 K in the Tibetan Plateau. As China's BC emissions decline, surface temperature responses show a mixed picture compared to 2010–2020, with more cooling in eastern China and Tibet of −0.2 to −0.3 K in the 2030s, but more warming in central China of approximately +0.3 K by the 2060s. The Indian BC might play a more important role in East Asian climate with reduction of BC emissions in China.","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":4.4,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141784673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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