Zhao Yang, Jiali Wang, Yun Qian, TC Chakraborty, Pengfei Xue, William J. Pringle, Chenfu Huang, Miraj Bhakta Kayastha, Huilin Huang, Jianfeng Li, Robert Hetland
To understand future summer precipitation changes over the Great Lakes Region (GLR), we performed an ensemble of regional climate simulations through the Pseudo-Global Warming (PGW) approach. We found that different types of convective precipitation respond differently to the PGW signal. Isolated deep convection (IDC), usually concentrated in the southern domain, shows an increase in precipitation to the north of the GLR. Mesoscale convective systems (MCSs), usually concentrated upwind of the GLR, shift to the downwind region with increased precipitation. Thermodynamic variables such as convective available potential energy (CAPE) and convective inhibition energy (CIN) are found to increase across almost the entire studied domain, creating a potential environment more favorable for stronger convection systems and less favorable for weaker ones. Meanwhile, changes in the lifting condensation level (LCL) and level of free convection (LFC) show a strong correlation with variations in convective precipitation, highlighting the significance of these thermodynamic factors in controlling precipitation over the domain. Our results indicate that the decrease in LCL and LCF in areas with increased convective precipitation is mainly due to increased atmospheric moisture. In response to the prescribed warming perturbation, MCSs occur more frequently downwind, while localized IDCs exhibit more intense rain rates, longer durations, and larger rainfall area.
{"title":"Summer Convective Precipitation Changes Over the Great Lakes Region Under a Warming Scenario","authors":"Zhao Yang, Jiali Wang, Yun Qian, TC Chakraborty, Pengfei Xue, William J. Pringle, Chenfu Huang, Miraj Bhakta Kayastha, Huilin Huang, Jianfeng Li, Robert Hetland","doi":"10.1029/2024JD041011","DOIUrl":"https://doi.org/10.1029/2024JD041011","url":null,"abstract":"<p>To understand future summer precipitation changes over the Great Lakes Region (GLR), we performed an ensemble of regional climate simulations through the Pseudo-Global Warming (PGW) approach. We found that different types of convective precipitation respond differently to the PGW signal. Isolated deep convection (IDC), usually concentrated in the southern domain, shows an increase in precipitation to the north of the GLR. Mesoscale convective systems (MCSs), usually concentrated upwind of the GLR, shift to the downwind region with increased precipitation. Thermodynamic variables such as convective available potential energy (CAPE) and convective inhibition energy (CIN) are found to increase across almost the entire studied domain, creating a potential environment more favorable for stronger convection systems and less favorable for weaker ones. Meanwhile, changes in the lifting condensation level (LCL) and level of free convection (LFC) show a strong correlation with variations in convective precipitation, highlighting the significance of these thermodynamic factors in controlling precipitation over the domain. Our results indicate that the decrease in LCL and LCF in areas with increased convective precipitation is mainly due to increased atmospheric moisture. In response to the prescribed warming perturbation, MCSs occur more frequently downwind, while localized IDCs exhibit more intense rain rates, longer durations, and larger rainfall area.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD041011","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141968303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Improving tropical cyclone (TC) rainfall prediction is vital as climate change has led to an increase in TC rainfall rates. Enhanced reliability in predicting TC tracks has paved the way for statistical methodologies to make use of them in estimating current TC rainfall, achieved by identifying similar past TC tracks and obtaining their corresponding rainfall data. While the Fuzzy C Means (FCM) clustering algorithm is widely used, it has limitations stemming from its clustering-centric design, hindering its ability to pinpoint the most appropriate similar TCs. Our study introduces the Sinkhorn distance, a novel similarity metric that measures the cost of transforming one set of data to another, for assessing TC similarity in rainfall prediction. Our findings indicate that utilizing Sinkhorn distance enhances the accuracy of TC rainfall predictions across the Western North Pacific region. When compared to the conventional approach using FCM, our Sinkhorn distance-based methodology yields slightly better yet statistically significant results. The improvement is due to better identification of similar TCs, characterized by closer proximity of similar TC tracks to the target TC track, facilitated by Sinkhorn distance. This underscores how minor differences in TC track can alter rainfall distribution, emphasizing the critical importance of accurate track prediction in rainfall prediction and the need to reconsider how we categorize TCs together, which can have implications for climate and atmospheric sciences. Collectively, the inclusion of Sinkhorn distance stands as a valuable addition to our toolkit for discerning similar TC tracks, thus elevating the accuracy of TC rainfall predictions.
{"title":"An Alternative Similar Tropical Cyclone Identification Algorithm for Statistical TC Rainfall Prediction in the Western North Pacific","authors":"J. A. Hokson, S. Kanae","doi":"10.1029/2023JD040246","DOIUrl":"https://doi.org/10.1029/2023JD040246","url":null,"abstract":"<p>Improving tropical cyclone (TC) rainfall prediction is vital as climate change has led to an increase in TC rainfall rates. Enhanced reliability in predicting TC tracks has paved the way for statistical methodologies to make use of them in estimating current TC rainfall, achieved by identifying similar past TC tracks and obtaining their corresponding rainfall data. While the Fuzzy C Means (FCM) clustering algorithm is widely used, it has limitations stemming from its clustering-centric design, hindering its ability to pinpoint the most appropriate similar TCs. Our study introduces the Sinkhorn distance, a novel similarity metric that measures the cost of transforming one set of data to another, for assessing TC similarity in rainfall prediction. Our findings indicate that utilizing Sinkhorn distance enhances the accuracy of TC rainfall predictions across the Western North Pacific region. When compared to the conventional approach using FCM, our Sinkhorn distance-based methodology yields slightly better yet statistically significant results. The improvement is due to better identification of similar TCs, characterized by closer proximity of similar TC tracks to the target TC track, facilitated by Sinkhorn distance. This underscores how minor differences in TC track can alter rainfall distribution, emphasizing the critical importance of accurate track prediction in rainfall prediction and the need to reconsider how we categorize TCs together, which can have implications for climate and atmospheric sciences. Collectively, the inclusion of Sinkhorn distance stands as a valuable addition to our toolkit for discerning similar TC tracks, thus elevating the accuracy of TC rainfall predictions.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JD040246","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141968304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Theodore M. McHardy, David A. Peterson, Jason M. Apke, Steven D. Miller, James R. Campbell, Edward J. 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":"Theodore M. McHardy, David A. Peterson, Jason M. Apke, Steven D. Miller, James R. Campbell, Edward J. Hyer","doi":"10.1029/2023JD039418","DOIUrl":"10.1029/2023JD039418","url":null,"abstract":"<p>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.</p>","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}
Zhiwen Dong, Ting Wei, Eric J. R. Parteli, Xiaoli Liu, Jiawen Ren, Yaping Shao
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, Eric J. R. Parteli, Xiaoli Liu, Jiawen Ren, Yaping Shao","doi":"10.1029/2023JD040711","DOIUrl":"10.1029/2023JD040711","url":null,"abstract":"<p>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 δ<sup>56</sup>Fe) 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 δ<sup>56</sup>Fe ranged from −1.06 ± 0.07‰ to 0.33 ± 0.04‰, regardless of their concentration. Moreover, anomalous δ<sup>56</sup>Fe 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.</p>","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":"10.1029/2023JD040632","url":null,"abstract":"<p>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.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JD040632","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":"OA","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":"10.1029/2024JD041034","url":null,"abstract":"<p>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.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD041034","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":"OA","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":"10.1029/2023JD039728","url":null,"abstract":"<p>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.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":3.8,"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":"10.1029/2024JD041296","url":null,"abstract":"<p>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.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD041296","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":"OA","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":"10.1029/2024JD041651","url":null,"abstract":"<p>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.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":3.8,"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":"10.1029/2023JD040630","url":null,"abstract":"<p>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>.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JD040630","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":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}