Pub Date : 2023-08-01DOI: 10.1080/07055900.2023.2239194
D. Jeong, Alex J. Cannon
Abstract Given the growing number of global climate models (GCMs) with simulations available for impacts and adaptation studies, methods have been introduced to select models that are ‘fit-for-purpose’. This study applies a GCM selection process to historical and future climate projections from 38 and 43 GCMs contributing to the fifth and sixth phases of the Coupled Model Intercomparison Project (CMIP5 and CMIP6). Models are selected based on historical performance, with a further selection step targeted at reducing interdependencies between closely related model variants and ensemble members. Ten performance measures are calculated based on climatological statistics (mean, standard deviation, and seasonal cycle) of three climate variables (precipitation, sea level pressure, and surface air temperature (SAT)), as well as SAT warming trend for the 1985–2014 period. Performance is assessed over Canada and six Canadian sub-regions, at both annual and seasonal timescales. As initial-condition members and minor variants of GCMs are not independent, a representative democracy approach – using ensemble averages of initial-condition members and including only the best performance model among minor variants – is employed to reduce redundancy in selected subsets. There is a strong correlation between recent warming trends and future warming projections across Canada; therefore, observed SAT warming trends are recognized as important observational-constraints to aid in model selection. By removing “hot models” that fail to reproduce the historical SAT warming trend, a representative subset of observationally-constrained GCMs projects lower annual SAT than model democracy (using all model runs assuming independence and equal plausibility) over Canada and six Canadian sub-regions for 2071–2100.
{"title":"An Approach for Selecting Observationally-Constrained Global Climate Model Ensembles for Regional Climate Impacts and Adaptation Studies in Canada","authors":"D. Jeong, Alex J. Cannon","doi":"10.1080/07055900.2023.2239194","DOIUrl":"https://doi.org/10.1080/07055900.2023.2239194","url":null,"abstract":"Abstract\u0000 Given the growing number of global climate models (GCMs) with simulations available for impacts and adaptation studies, methods have been introduced to select models that are ‘fit-for-purpose’. This study applies a GCM selection process to historical and future climate projections from 38 and 43 GCMs contributing to the fifth and sixth phases of the Coupled Model Intercomparison Project (CMIP5 and CMIP6). Models are selected based on historical performance, with a further selection step targeted at reducing interdependencies between closely related model variants and ensemble members. Ten performance measures are calculated based on climatological statistics (mean, standard deviation, and seasonal cycle) of three climate variables (precipitation, sea level pressure, and surface air temperature (SAT)), as well as SAT warming trend for the 1985–2014 period. Performance is assessed over Canada and six Canadian sub-regions, at both annual and seasonal timescales. As initial-condition members and minor variants of GCMs are not independent, a representative democracy approach – using ensemble averages of initial-condition members and including only the best performance model among minor variants – is employed to reduce redundancy in selected subsets. There is a strong correlation between recent warming trends and future warming projections across Canada; therefore, observed SAT warming trends are recognized as important observational-constraints to aid in model selection. By removing “hot models” that fail to reproduce the historical SAT warming trend, a representative subset of observationally-constrained GCMs projects lower annual SAT than model democracy (using all model runs assuming independence and equal plausibility) over Canada and six Canadian sub-regions for 2071–2100.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46105560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-08DOI: 10.1080/07055900.2023.2221217
Jingying Wang, Zhiwei Wu
ABSTRACT The East Asian summer monsoon (EASM) and tropical cyclones (TCs) in the Western North Pacific (WNP) are both responsible for the East Asian summer rainfall, yet most studies only examine their rainfall separately. In this study, the East Asian summer rainfall for the past 39-years (1983-2021, May to September) is divided into three categories: monsoon rainfall without TCs’ influence (monsoon-only rainfall), TC rainfall independent of monsoon (TC-only rainfall) and monsoon-TC joint (MS-TC) rainfall. Compared with the other two categories, MS-TC rainfall exhibits distinctive features. During strong MS-TC years, a distinct cyclonic anomaly centre prevails over tropical WNP with anomalous southeasterlies extending from the tropics to the subtropics. Large rainfall centres are located at the west edge of the northern Philippines, the Philippine Basin, and the Korean Peninsula. The WNP Subtropical High (WNPSH) withdrawals eastward, with an eastward extension of the monsoon trough. These circulation configurations provide favourable environmental conditions for more northward movements of TCs, including low-level positive relative vorticity and enhanced vertical motion in WNP. Observational and theoretical analysis results show that anomalous thermal conditions in the southern Maritime Continent (MC) (97.5°−112.5°E, 8°−18°S) in early spring (March to April) can be a precursor for anomalous MS-TC rainfall. Strong MS-TC rainfall is usually preceded by depressed convection and anomalous westerlies near the MC. These anomalies can persist through the following summer and induce the positive feedback of cooling sea surface temperature (SST) in MC and cyclonic anomalies in tropical WNP through the wind-evaporation-SST (WES) effect and local Hadley circulation anomalies. The linear baroclinic model (LBM) experiments demonstrate that enhanced convection in tropical WNP further maintains the anomalous cyclone through Gill's response, which in turn modulates the distribution and amount of MS-TC rainfall.
{"title":"Distinctive Features of Monsoon-TC Joint Rainfall over Western North Pacific and its Relationship with the Maritime Continent Thermal Condition","authors":"Jingying Wang, Zhiwei Wu","doi":"10.1080/07055900.2023.2221217","DOIUrl":"https://doi.org/10.1080/07055900.2023.2221217","url":null,"abstract":"ABSTRACT The East Asian summer monsoon (EASM) and tropical cyclones (TCs) in the Western North Pacific (WNP) are both responsible for the East Asian summer rainfall, yet most studies only examine their rainfall separately. In this study, the East Asian summer rainfall for the past 39-years (1983-2021, May to September) is divided into three categories: monsoon rainfall without TCs’ influence (monsoon-only rainfall), TC rainfall independent of monsoon (TC-only rainfall) and monsoon-TC joint (MS-TC) rainfall. Compared with the other two categories, MS-TC rainfall exhibits distinctive features. During strong MS-TC years, a distinct cyclonic anomaly centre prevails over tropical WNP with anomalous southeasterlies extending from the tropics to the subtropics. Large rainfall centres are located at the west edge of the northern Philippines, the Philippine Basin, and the Korean Peninsula. The WNP Subtropical High (WNPSH) withdrawals eastward, with an eastward extension of the monsoon trough. These circulation configurations provide favourable environmental conditions for more northward movements of TCs, including low-level positive relative vorticity and enhanced vertical motion in WNP. Observational and theoretical analysis results show that anomalous thermal conditions in the southern Maritime Continent (MC) (97.5°−112.5°E, 8°−18°S) in early spring (March to April) can be a precursor for anomalous MS-TC rainfall. Strong MS-TC rainfall is usually preceded by depressed convection and anomalous westerlies near the MC. These anomalies can persist through the following summer and induce the positive feedback of cooling sea surface temperature (SST) in MC and cyclonic anomalies in tropical WNP through the wind-evaporation-SST (WES) effect and local Hadley circulation anomalies. The linear baroclinic model (LBM) experiments demonstrate that enhanced convection in tropical WNP further maintains the anomalous cyclone through Gill's response, which in turn modulates the distribution and amount of MS-TC rainfall.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48422490","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-02DOI: 10.1080/07055900.2023.2202656
Sacré Régis Mailly Didi, Moussa Diakhaté, A. Diedhiou
ABSTRACT A 37-year record of rainfall gridded data covering West Africa and a Global Sea Surface Temperature (SST) dataset are used to investigate the remote influence of SST anomalies in the Equatorial Pacific on the interannual variability of West Africa’s extreme rainfall indices over the period 1981–2018. The top five (5) years with the strongest and weakest peak of Niño3.4 SST monthly anomalies are selected, and May-to-September (MJJAS) composite anomalies of the total and extreme rainfall indices are performed. Results reveal that Equatorial Pacific SST’s impacts on daily rainfall intensity are generally more robust than that on their frequency. The significant changes in the mean zonal atmospheric circulation associated with the SST lead to significant dynamic and thermodynamic changes that affect the West African monsoon system locally. During El Niño (La Niña) years, (i) a weakening (strengthening) of the Tropical Easterly Jet (TEJ), (ii) a strengthening (weakening), and southward (northward) shift position of the African Easterly Jet (AEJ), and (iii) a decrease (increase) of the monsoon flow are noted. These changes in the atmospheric circulation prevent (encourage) a supply of moisture, resulting in a reduction (increase) in extreme precipitation observed across West Africa. Equatorial eastern Pacific warming (cooling) is also shown to lead to stable (unstable) atmospheric conditions over West Africa that block (generate) the development of convective systems.
{"title":"Changes in the West Africa Monsoon Precipitation Extremes during ENSO developing Phases","authors":"Sacré Régis Mailly Didi, Moussa Diakhaté, A. Diedhiou","doi":"10.1080/07055900.2023.2202656","DOIUrl":"https://doi.org/10.1080/07055900.2023.2202656","url":null,"abstract":"ABSTRACT A 37-year record of rainfall gridded data covering West Africa and a Global Sea Surface Temperature (SST) dataset are used to investigate the remote influence of SST anomalies in the Equatorial Pacific on the interannual variability of West Africa’s extreme rainfall indices over the period 1981–2018. The top five (5) years with the strongest and weakest peak of Niño3.4 SST monthly anomalies are selected, and May-to-September (MJJAS) composite anomalies of the total and extreme rainfall indices are performed. Results reveal that Equatorial Pacific SST’s impacts on daily rainfall intensity are generally more robust than that on their frequency. The significant changes in the mean zonal atmospheric circulation associated with the SST lead to significant dynamic and thermodynamic changes that affect the West African monsoon system locally. During El Niño (La Niña) years, (i) a weakening (strengthening) of the Tropical Easterly Jet (TEJ), (ii) a strengthening (weakening), and southward (northward) shift position of the African Easterly Jet (AEJ), and (iii) a decrease (increase) of the monsoon flow are noted. These changes in the atmospheric circulation prevent (encourage) a supply of moisture, resulting in a reduction (increase) in extreme precipitation observed across West Africa. Equatorial eastern Pacific warming (cooling) is also shown to lead to stable (unstable) atmospheric conditions over West Africa that block (generate) the development of convective systems.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42330122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-05DOI: 10.1080/07055900.2023.2191831
B. Casati, T. Robinson, F. Lemay, M. Køltzow, T. Haiden, E. Mekis, F. Lespinas, V. Fortin, G. Gascon, J. Milbrandt, Greg Smith
ABSTRACT As a contribution to the Year of Polar Prediction (YOPP), Environment and Climate Change Canada (ECCC) developed the Canadian Arctic Prediction System (CAPS), a high-resolution (3-km horizontal grid-spacing) deterministic Numerical Weather Prediction (NWP) system that ran in real-time from February 2018 to November 2021. During YOPP, ECCC was also running two other operational systems that cover the Arctic: the 10-km Regional Deterministic Prediction System (RDPS) and the 25-km Global Deterministic Prediction System (GDPS). The performance of these three systems over the Arctic was monitored and routinely compared during 2018, both subjectively and with objective verification scores. This work provides a description of CAPS and compares the surface variable objective verification for the Canadian deterministic NWP systems operational during YOPP, focusing on the Arctic winter and summer Special Observing Periods (Feb-March and July-Aug-Sept, 2018). CAPS outperforms RDPS and GDPS in predicting near-surface temperature, dew-point temperature, wind and precipitation, in both seasons and domains. All three systems exhibit a diurnal cycle in the near-surface temperature biases, with maxima at night and minima in day-time. In order to mitigate representativeness issues associated with complex topography, model tile temperatures are adjusted to the station elevation by applying a standard atmosphere lapse-rate: especially for the coarse-resolution models, the lapse-rate adjustment reduces the temperature cold biases characterising mountain terrains. Verification of winter precipitation is performed by adjusting solid precipitation measurement errors from the undercatch in windy conditions: the Canadian models’ systematic positive bias, which was artificially inflated by the undercatch, is reduced by the adjustment, to attain neutral bias. These YOPP dedicated intense verification activities have identified some strengths, weaknesses and systematic behaviours of the Canadian deterministic prediction systems at high latitudes: these results can serve as a benchmark, for comparison and further development. Moreover, this YOPP verification exercise has revealed some issues related to the verification of surface variables and has led to the development of better verification practices for the polar regions (and beyond).
{"title":"Performance of the Canadian Arctic Prediction System during the YOPP Special Observing Periods","authors":"B. Casati, T. Robinson, F. Lemay, M. Køltzow, T. Haiden, E. Mekis, F. Lespinas, V. Fortin, G. Gascon, J. Milbrandt, Greg Smith","doi":"10.1080/07055900.2023.2191831","DOIUrl":"https://doi.org/10.1080/07055900.2023.2191831","url":null,"abstract":"ABSTRACT As a contribution to the Year of Polar Prediction (YOPP), Environment and Climate Change Canada (ECCC) developed the Canadian Arctic Prediction System (CAPS), a high-resolution (3-km horizontal grid-spacing) deterministic Numerical Weather Prediction (NWP) system that ran in real-time from February 2018 to November 2021. During YOPP, ECCC was also running two other operational systems that cover the Arctic: the 10-km Regional Deterministic Prediction System (RDPS) and the 25-km Global Deterministic Prediction System (GDPS). The performance of these three systems over the Arctic was monitored and routinely compared during 2018, both subjectively and with objective verification scores. This work provides a description of CAPS and compares the surface variable objective verification for the Canadian deterministic NWP systems operational during YOPP, focusing on the Arctic winter and summer Special Observing Periods (Feb-March and July-Aug-Sept, 2018). CAPS outperforms RDPS and GDPS in predicting near-surface temperature, dew-point temperature, wind and precipitation, in both seasons and domains. All three systems exhibit a diurnal cycle in the near-surface temperature biases, with maxima at night and minima in day-time. In order to mitigate representativeness issues associated with complex topography, model tile temperatures are adjusted to the station elevation by applying a standard atmosphere lapse-rate: especially for the coarse-resolution models, the lapse-rate adjustment reduces the temperature cold biases characterising mountain terrains. Verification of winter precipitation is performed by adjusting solid precipitation measurement errors from the undercatch in windy conditions: the Canadian models’ systematic positive bias, which was artificially inflated by the undercatch, is reduced by the adjustment, to attain neutral bias. These YOPP dedicated intense verification activities have identified some strengths, weaknesses and systematic behaviours of the Canadian deterministic prediction systems at high latitudes: these results can serve as a benchmark, for comparison and further development. Moreover, this YOPP verification exercise has revealed some issues related to the verification of surface variables and has led to the development of better verification practices for the polar regions (and beyond).","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":"61 1","pages":"246 - 272"},"PeriodicalIF":1.2,"publicationDate":"2023-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45466832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-16DOI: 10.1080/07055900.2023.2184321
Y. Lin, L. Bianucci
{"title":"Seasonal Variability of the Ocean Circulation in Queen Charlotte Strait, British Columbia","authors":"Y. Lin, L. Bianucci","doi":"10.1080/07055900.2023.2184321","DOIUrl":"https://doi.org/10.1080/07055900.2023.2184321","url":null,"abstract":"","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":"1 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41526596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-27DOI: 10.1080/07055900.2023.2177136
B. H. Vaid, X. Liang
ABSTRACT It has been recognized by the scientific community for many years that erratic monsoon attribution should be prioritized in order to meet the growing demand for reliable monsoon forecasts. It is believed that the severe 2009 drought in the South and East Asian regions was caused by an erratic monsoon season, which has sparked enormous interest in its cause. In this study, we have identified a factor in the upper troposphere, i.e. the large-scale upper tropospheric temperature, which may have potentially functioned as a new cause. We have observed that a major change in the upper tropospheric temperature occurred, with one region over Central Asia and another over the eastern Tibetan Plateau; also observed is the interaction between these two local systems. The thermal wind link suggests that the 2009 circulations over the two different regions at 250 hPa – are characterized by a cyclone and an anti-cyclone over Central Asia and the eastern Tibetan Plateau, respectfully, and that this could be the dynamic cause of the 2009 monsoon prediction failure. Subtropical jets provide a means of connecting the dynamical systems in the two different regions, which have enhanced the convection over Central Asia and reduced the convection over South and East Asia during that period. Also revealed is the role of the thermodynamic processes, specifically the role of the vertical thermal contrast (VTC) over Central Asia and the eastern Tibetan Plateau, which is responsible for changing the convective patterns during the 2009 monsoon season. This is further substantiated by the inferred causal relationship between the upper VTC and longwave fluxes (LWFs) at the top of the atmosphere.
{"title":"Additional Possible Cause of the Erratic 2009 Monsoon Over South and East Asia: Large-Scale Change in the Upper Tropospheric Temperature","authors":"B. H. Vaid, X. Liang","doi":"10.1080/07055900.2023.2177136","DOIUrl":"https://doi.org/10.1080/07055900.2023.2177136","url":null,"abstract":"ABSTRACT It has been recognized by the scientific community for many years that erratic monsoon attribution should be prioritized in order to meet the growing demand for reliable monsoon forecasts. It is believed that the severe 2009 drought in the South and East Asian regions was caused by an erratic monsoon season, which has sparked enormous interest in its cause. In this study, we have identified a factor in the upper troposphere, i.e. the large-scale upper tropospheric temperature, which may have potentially functioned as a new cause. We have observed that a major change in the upper tropospheric temperature occurred, with one region over Central Asia and another over the eastern Tibetan Plateau; also observed is the interaction between these two local systems. The thermal wind link suggests that the 2009 circulations over the two different regions at 250 hPa – are characterized by a cyclone and an anti-cyclone over Central Asia and the eastern Tibetan Plateau, respectfully, and that this could be the dynamic cause of the 2009 monsoon prediction failure. Subtropical jets provide a means of connecting the dynamical systems in the two different regions, which have enhanced the convection over Central Asia and reduced the convection over South and East Asia during that period. Also revealed is the role of the thermodynamic processes, specifically the role of the vertical thermal contrast (VTC) over Central Asia and the eastern Tibetan Plateau, which is responsible for changing the convective patterns during the 2009 monsoon season. This is further substantiated by the inferred causal relationship between the upper VTC and longwave fluxes (LWFs) at the top of the atmosphere.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":"61 1","pages":"162 - 172"},"PeriodicalIF":1.2,"publicationDate":"2023-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44135098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-17DOI: 10.1080/07055900.2023.2173555
Md Tabrez Alam, Youmin Tang, Siraj Ul Islam
ABSTRACT With a westerly wind burst (WWB) parameterization scheme introduced into a hybrid coupled model (HCM), we investigated in Part 1 of this study the impact of WWBs on El Nino – Southern Oscillation (ENSO) simulation features, including asymmetry, phase locking, and diversity. In the second part, we investigate the impact of WWBs on ENSO prediction skills. To achieve this, two ensemble experiments, one with WWBs and one without WWBs, are performed to evaluate the predictions of sea surface temperature (SST) anomalies. The results show that both experiments can predict the SST anomalies in the equatorial central and eastern Pacific up to lead times of 12 months. The correlation coefficient between the model and observations shows that the WWB experiment produces better prediction skills than the experiment without WWBs, especially at lead times longer than four months during El Niño events. This result is consistent with the expectation that the WWB parameterization scheme plays an important role in describing physical processes, which is indicated in Part 1. We also presented a predictability analysis for Central Pacific (CP) and Eastern Pacific (EP) El Niño events. The prediction of both types of El Niño events is also improved by the WWB parameterization scheme at long lead times.
在混合耦合模型(HCM)中引入西风爆发(WWB)参数化方案，研究了西风爆发对厄尔尼诺-南方涛动(ENSO)模拟特征的影响，包括不对称性、锁相性和多样性。在第二部分中，我们研究了wbs对ENSO预测技能的影响。为了实现这一目标，进行了两个集合实验，一个是有水波场，一个是没有水波场，以评估海表温度(SST)异常的预测。结果表明，这两个实验都可以预测赤道中、东太平洋海温异常，预测时间可达12个月。模型与观测值的相关系数表明，与不含水源源的试验相比，有水源源的试验具有更好的预测能力，特别是在El Niño事件期间，提前期超过4个月的预测能力更强。这一结果与第1部分中所指出的WWB参数化方案在描述物理过程中发挥重要作用的期望是一致的。我们还提出了中太平洋(CP)和东太平洋(EP) El Niño事件的可预测性分析。在较长的提前期，WWB参数化方案也改善了这两种类型的El Niño事件的预测。
{"title":"Impact of Westerly Wind Bursts (WWBs) on ENSO based on a Hybrid Coupled Model: Part II – ENSO Prediction","authors":"Md Tabrez Alam, Youmin Tang, Siraj Ul Islam","doi":"10.1080/07055900.2023.2173555","DOIUrl":"https://doi.org/10.1080/07055900.2023.2173555","url":null,"abstract":"ABSTRACT With a westerly wind burst (WWB) parameterization scheme introduced into a hybrid coupled model (HCM), we investigated in Part 1 of this study the impact of WWBs on El Nino – Southern Oscillation (ENSO) simulation features, including asymmetry, phase locking, and diversity. In the second part, we investigate the impact of WWBs on ENSO prediction skills. To achieve this, two ensemble experiments, one with WWBs and one without WWBs, are performed to evaluate the predictions of sea surface temperature (SST) anomalies. The results show that both experiments can predict the SST anomalies in the equatorial central and eastern Pacific up to lead times of 12 months. The correlation coefficient between the model and observations shows that the WWB experiment produces better prediction skills than the experiment without WWBs, especially at lead times longer than four months during El Niño events. This result is consistent with the expectation that the WWB parameterization scheme plays an important role in describing physical processes, which is indicated in Part 1. We also presented a predictability analysis for Central Pacific (CP) and Eastern Pacific (EP) El Niño events. The prediction of both types of El Niño events is also improved by the WWB parameterization scheme at long lead times.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":"61 1","pages":"186 - 196"},"PeriodicalIF":1.2,"publicationDate":"2023-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42542526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-14DOI: 10.1080/07055900.2023.2175639
H. Ueda, Masaya Kuramochi, H. Mitsudera
ABSTRACT This study investigated interannual variations in the late winter (January–March) sea-ice extent in the Okhotsk Sea (OS) and its relationship with the atmospheric circulation from 1971 to 2018. During heavy sea-ice years, negative air temperature anomalies are broadly discernable between the northeastern part of Eurasia and the North Pacific including the coastal polynyas adjacent to the northern and western coast of the OS. Cold air mass (CAM) genesis indicates the importance of the insulation effect of sea-ice in the persistent cold air temperatures in the OS. Light sea-ice years are marked by anomalous southeasterly winds and the resultant warm air advection associated with increases in extratropical cyclones. Southeasterly anomalies are associated with the weakening of the Aleutian low. Upper-tropospheric anticyclones dominating around the OS are closely connected with intensified convection in the vicinity of the South China Sea through propagation of a stationary Rossby wave relevant to La Niña-like warm sea surface temperature anomalies. The seasonal evolution of the CAM amount, sea ice in the Sea of Okhotsk, and the Aleutian low suggest that there may be chain feedback between them.
{"title":"Interannual Variations of Sea-ice Extent in the Okhotsk Sea – A Pan-Okhotsk Climate System Perspective","authors":"H. Ueda, Masaya Kuramochi, H. Mitsudera","doi":"10.1080/07055900.2023.2175639","DOIUrl":"https://doi.org/10.1080/07055900.2023.2175639","url":null,"abstract":"ABSTRACT This study investigated interannual variations in the late winter (January–March) sea-ice extent in the Okhotsk Sea (OS) and its relationship with the atmospheric circulation from 1971 to 2018. During heavy sea-ice years, negative air temperature anomalies are broadly discernable between the northeastern part of Eurasia and the North Pacific including the coastal polynyas adjacent to the northern and western coast of the OS. Cold air mass (CAM) genesis indicates the importance of the insulation effect of sea-ice in the persistent cold air temperatures in the OS. Light sea-ice years are marked by anomalous southeasterly winds and the resultant warm air advection associated with increases in extratropical cyclones. Southeasterly anomalies are associated with the weakening of the Aleutian low. Upper-tropospheric anticyclones dominating around the OS are closely connected with intensified convection in the vicinity of the South China Sea through propagation of a stationary Rossby wave relevant to La Niña-like warm sea surface temperature anomalies. The seasonal evolution of the CAM amount, sea ice in the Sea of Okhotsk, and the Aleutian low suggest that there may be chain feedback between them.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":"61 1","pages":"234 - 245"},"PeriodicalIF":1.2,"publicationDate":"2023-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42134774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-21DOI: 10.1080/07055900.2022.2155103
J. Dumas, D. Gilbert
ABSTRACT The Gulf of St. Lawrence (GSL) is an Eastern Canada semi-enclosed sea under the influence of the freshwater discharge from the Great Lakes – St. Lawrence River drainage basin. Studying the variability of oceanographic conditions in the GSL under a changing climate is important for ecosystem and fisheries management. To supplement the available in situ sea surface salinity (SSS) measurements with satellite SSS data, this study compares all available years of Soil Moisture Ocean Salinity (SMOS) and Soil Moisture Active and Passive (SMAP) satellite SSS to in situ SSS observations. Despite the relatively cold water and proximity to land and sea ice, the satellite SSS is able to capture the interannual variability and annual cycle of SSS in the GSL, with correlations ranging from 0.80 to 0.85 in the Southern GSL, and 0.22 to 0.77 in the Northern GSL. All satellite SSS data products were able to detect the very low salinity year of 2017 in the Southern GSL.
{"title":"Comparison of SMOS, SMAP and In Situ Sea Surface Salinity in the Gulf of St. Lawrence","authors":"J. Dumas, D. Gilbert","doi":"10.1080/07055900.2022.2155103","DOIUrl":"https://doi.org/10.1080/07055900.2022.2155103","url":null,"abstract":"ABSTRACT The Gulf of St. Lawrence (GSL) is an Eastern Canada semi-enclosed sea under the influence of the freshwater discharge from the Great Lakes – St. Lawrence River drainage basin. Studying the variability of oceanographic conditions in the GSL under a changing climate is important for ecosystem and fisheries management. To supplement the available in situ sea surface salinity (SSS) measurements with satellite SSS data, this study compares all available years of Soil Moisture Ocean Salinity (SMOS) and Soil Moisture Active and Passive (SMAP) satellite SSS to in situ SSS observations. Despite the relatively cold water and proximity to land and sea ice, the satellite SSS is able to capture the interannual variability and annual cycle of SSS in the GSL, with correlations ranging from 0.80 to 0.85 in the Southern GSL, and 0.22 to 0.77 in the Northern GSL. All satellite SSS data products were able to detect the very low salinity year of 2017 in the Southern GSL.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":"61 1","pages":"148 - 161"},"PeriodicalIF":1.2,"publicationDate":"2022-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42786925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-15DOI: 10.1080/07055900.2022.2153325
Annaliese C. S. Meyer, J. Cullen, D. Grundle
ABSTRACT This study presents dissolved nitrous oxide (N2O) concentrations in the water column at the Bermuda Atlantic Time-series Study (BATS) station and uses a subset of these measurements to estimate air-to-sea flux for four specific time points between September 2018 and June 2019. N2O concentrations at BATS were in the range of 4.0 nmol L−1–16.9 nmol L−1, with vertical profiles which were the mirror inverse of dissolved oxygen. Regardless of season, N2O concentration maxima were found within the oxygen minimum zone (OMZ). The highest maximum N2O values were observed in November and lowest in October. As the water column at BATS remains consistently at dissolved oxygen concentrations greater than 140 µmol L−1, and therefore aerobic, we assume that the bulk of N2O production occurs through nitrification. A nitrification source is supported by a correlation between excess N2O (ΔN2O) below the mixed layer, apparent oxygen utilization (AOU) and nitrate concentrations. We estimate a pooled average yield of 0.027% to 0.038% N2O from nitrification at BATS. Finally, estimates of air–sea exchange of N2O using regional average monthly wind speeds indicated that this region acts as a weak source or a sink of atmospheric N2O, and varies between months.
{"title":"Nitrous Oxide Distributions in the Oxygenated Water Column of the Sargasso Sea","authors":"Annaliese C. S. Meyer, J. Cullen, D. Grundle","doi":"10.1080/07055900.2022.2153325","DOIUrl":"https://doi.org/10.1080/07055900.2022.2153325","url":null,"abstract":"ABSTRACT This study presents dissolved nitrous oxide (N2O) concentrations in the water column at the Bermuda Atlantic Time-series Study (BATS) station and uses a subset of these measurements to estimate air-to-sea flux for four specific time points between September 2018 and June 2019. N2O concentrations at BATS were in the range of 4.0 nmol L−1–16.9 nmol L−1, with vertical profiles which were the mirror inverse of dissolved oxygen. Regardless of season, N2O concentration maxima were found within the oxygen minimum zone (OMZ). The highest maximum N2O values were observed in November and lowest in October. As the water column at BATS remains consistently at dissolved oxygen concentrations greater than 140 µmol L−1, and therefore aerobic, we assume that the bulk of N2O production occurs through nitrification. A nitrification source is supported by a correlation between excess N2O (ΔN2O) below the mixed layer, apparent oxygen utilization (AOU) and nitrate concentrations. We estimate a pooled average yield of 0.027% to 0.038% N2O from nitrification at BATS. Finally, estimates of air–sea exchange of N2O using regional average monthly wind speeds indicated that this region acts as a weak source or a sink of atmospheric N2O, and varies between months.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":"61 1","pages":"173 - 185"},"PeriodicalIF":1.2,"publicationDate":"2022-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46582116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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