This study examines the long-term variability (1980–2022) of low-level clouds and their base heights using cloud observations from India Meteorological Department (IMD) over the Indo-Gangetic Plain (IGP) crucial for aviation. For this purpose, synoptic cloud observation data, coded as per World Meteorological Organisation (WMO) standards, were collected every three hours from four weather stations of IMD namely Amritsar, Delhi, Lucknow, and Patna. Highest prevalence of cloud types namely Stratus (St), Stratocumulus (Sc), Cumulus (Cu), and Cumulonimbus (Cb) was observed during monsoon than pre-monsoon. We have reported the occurrence of Cb clouds during monsoon in the range of 20–50 %. Sc clouds show diurnal variation, peaking at 00, 03 UTC, and 15, 18, and 21 UTC. Cu and Cb clouds exhibit maxima in the afternoon during pre-monsoon and monsoon seasons, possibly due to the diurnal cycle of the atmospheric boundary layer height variations. Monsoon cases surpass pre-monsoon at all IGP sites. Notably, Cb with CBH 600–1000 m causes maximum rainfall during monsoon, and predominant Cb base heights are 600–1000 m, 1000–1500 m, and 1500–2000m across decades.
{"title":"Long-term variability of the low-level clouds across Indo-Gangetic Plain","authors":"Krishna Kumar Shukla , Gajendra Kumar , Chander Singh Tomar , Raju Attada , Kondapalli Niranjan Kumar , Anoop Kumar Mishra","doi":"10.1016/j.dynatmoce.2024.101521","DOIUrl":"10.1016/j.dynatmoce.2024.101521","url":null,"abstract":"<div><div>This study examines the long-term variability (1980–2022) of low-level clouds and their base heights using cloud observations from India Meteorological Department (IMD) over the Indo-Gangetic Plain (IGP) crucial for aviation. For this purpose, synoptic cloud observation data, coded as per World Meteorological Organisation (WMO) standards, were collected every three hours from four weather stations of IMD namely Amritsar, Delhi, Lucknow, and Patna<em>.</em> Highest prevalence of cloud types namely Stratus (St), Stratocumulus (Sc), Cumulus (Cu), and Cumulonimbus (Cb) was observed during monsoon than pre-monsoon. We have reported the occurrence of Cb clouds during monsoon in the range of 20–50 %. Sc clouds show diurnal variation, peaking at 00, 03 UTC, and 15, 18, and 21 UTC. Cu and Cb clouds exhibit maxima in the afternoon during pre-monsoon and monsoon seasons, possibly due to the diurnal cycle of the atmospheric boundary layer height variations. Monsoon cases surpass pre-monsoon at all IGP sites. Notably, Cb with CBH 600–1000 m causes maximum rainfall during monsoon, and predominant Cb base heights are 600–1000 m, 1000–1500 m, and 1500–2000m across decades.</div></div>","PeriodicalId":50563,"journal":{"name":"Dynamics of Atmospheres and Oceans","volume":"109 ","pages":"Article 101521"},"PeriodicalIF":1.9,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143160127","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 : 2024-12-05DOI: 10.1016/j.dynatmoce.2024.101520
Vasubandhu Misra , C.B. Jayasankar
In this study we examine a 25-year simulation of a Regional Coupled Ocean-Atmosphere Model (RCOM) forced by global atmospheric and ocean reanalysis at the lateral boundaries over eastern equatorial Africa which includes parts of the Great Horn of Africa (GHA). It is a first of its kind use of a RCOM for the region. The model shows several observed features of the regional climate with bimodal peaks in the seasonal cycle interspersed with regions of unimodal peak, significant diurnal and intra-seasonal variations of precipitation especially over Lake Victoria and robust seasonal cycle of the upper western India Ocean. Nonetheless the model shows significant dry bias of seasonal precipitation that is persistent throughout the year, which is also reflected at diurnal and intra-seasonal scales. The mixed layer and thermocline depths are found to be shallower in the model simulation suggesting a far more stratified upper western Indian Ocean than the observations indicate.
{"title":"The regional coupled ocean-atmosphere model simulation over Eastern Tropical Africa","authors":"Vasubandhu Misra , C.B. Jayasankar","doi":"10.1016/j.dynatmoce.2024.101520","DOIUrl":"10.1016/j.dynatmoce.2024.101520","url":null,"abstract":"<div><div>In this study we examine a 25-year simulation of a Regional Coupled Ocean-Atmosphere Model (RCOM) forced by global atmospheric and ocean reanalysis at the lateral boundaries over eastern equatorial Africa which includes parts of the Great Horn of Africa (GHA). It is a first of its kind use of a RCOM for the region. The model shows several observed features of the regional climate with bimodal peaks in the seasonal cycle interspersed with regions of unimodal peak, significant diurnal and intra-seasonal variations of precipitation especially over Lake Victoria and robust seasonal cycle of the upper western India Ocean. Nonetheless the model shows significant dry bias of seasonal precipitation that is persistent throughout the year, which is also reflected at diurnal and intra-seasonal scales. The mixed layer and thermocline depths are found to be shallower in the model simulation suggesting a far more stratified upper western Indian Ocean than the observations indicate.</div></div>","PeriodicalId":50563,"journal":{"name":"Dynamics of Atmospheres and Oceans","volume":"109 ","pages":"Article 101520"},"PeriodicalIF":1.9,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143160128","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 : 2024-12-01DOI: 10.1016/j.dynatmoce.2024.101516
Ximei Zhao , Bo Lu
Using the Wyrtki index, which comprehensively characterizes the dynamics of ENSO, we evaluated the fitting performance of 24 CMIP6 models for the ENSO dynamic processes during the period from 1980 to 2014. We identified the high-skill (HS) models with better simulation capabilities and the low-skill (LS) models with poorer simulation abilities. Compared to observational and reanalysis data, the HS models better simulate the average state of the tropical Pacific and the associated dynamic processes of ENSO from 1980 to 2014. In contrast, the LS models show a colder equatorial cold tongue, a steeper thermocline slope, and stronger trade winds in the central and western Pacific. The zonal advection feedback in the LS models is weaker, while the thermocline feedback is stronger, which may contribute to the deviations observed in the LS models when simulating the historical ENSO periodicity. The HS models indicate a trend of shorter conventional ENSO periodicity for the period from 2066 to 2100, which contrasts sharply with the conclusion drawn from the 24 CMIP6 models that show no significant change in ENSO periodicity duration. Additionally, the period of CP ENSO is projected to become shorter under SSP585 scenario for the HS models and all models. In contrast, the CP ENSO period change is insignificant for the LS models.
{"title":"Uncertainty reduction in ENSO periodicity projection based on the Wyrtki index","authors":"Ximei Zhao , Bo Lu","doi":"10.1016/j.dynatmoce.2024.101516","DOIUrl":"10.1016/j.dynatmoce.2024.101516","url":null,"abstract":"<div><div>Using the Wyrtki index, which comprehensively characterizes the dynamics of ENSO, we evaluated the fitting performance of 24 CMIP6 models for the ENSO dynamic processes during the period from 1980 to 2014. We identified the high-skill (HS) models with better simulation capabilities and the low-skill (LS) models with poorer simulation abilities. Compared to observational and reanalysis data, the HS models better simulate the average state of the tropical Pacific and the associated dynamic processes of ENSO from 1980 to 2014. In contrast, the LS models show a colder equatorial cold tongue, a steeper thermocline slope, and stronger trade winds in the central and western Pacific. The zonal advection feedback in the LS models is weaker, while the thermocline feedback is stronger, which may contribute to the deviations observed in the LS models when simulating the historical ENSO periodicity. The HS models indicate a trend of shorter conventional ENSO periodicity for the period from 2066 to 2100, which contrasts sharply with the conclusion drawn from the 24 CMIP6 models that show no significant change in ENSO periodicity duration. Additionally, the period of CP ENSO is projected to become shorter under SSP585 scenario for the HS models and all models. In contrast, the CP ENSO period change is insignificant for the LS models.</div></div>","PeriodicalId":50563,"journal":{"name":"Dynamics of Atmospheres and Oceans","volume":"109 ","pages":"Article 101516"},"PeriodicalIF":1.9,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143160124","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 : 2024-12-01DOI: 10.1016/j.dynatmoce.2024.101499
Mukesh Singh Raghav , Sharath Jose , Amit Apte , Rama Govindarajan
{"title":"Corrigendum to “Effects of equatorially-confined shear flow on MRG and Rossby waves” [Dyn. Atmos. Oceans 100 (2022) 101331]","authors":"Mukesh Singh Raghav , Sharath Jose , Amit Apte , Rama Govindarajan","doi":"10.1016/j.dynatmoce.2024.101499","DOIUrl":"10.1016/j.dynatmoce.2024.101499","url":null,"abstract":"","PeriodicalId":50563,"journal":{"name":"Dynamics of Atmospheres and Oceans","volume":"108 ","pages":"Article 101499"},"PeriodicalIF":1.9,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142757542","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}
The relationship between El Niño events and surface air temperature (SAT) over Sri Lanka (SL) has been well documented. However, the impact of the two different types of El Niño flavors on seasonal SAT variability in SL remains to be thoroughly investigated. Therefore, to identify the effect of two different types of El Niño on SAT over SL, we analyzed reanalysis and observational datasets from 1981 to 2020. This study mainly focused on the boreal spring season during the decaying phase of El Niño events. We show the presence of a strong SAT cooling in spring over the SL during the decaying phase of Central Pacific (CP) El Niño events, while intense spring SAT warming over SL is particularly pronounced during the Eastern Pacific (EP) El Niño decaying phase. It is found that low-level convergence over SL and the east coast of India associated with easterlies extending from the southern flank of the westward-shifted Western North Pacific anticyclones (WNPA) lead to updrafts. This results in enhanced cloud conditions and decreased incoming shortwave radiation, thereby causing strong cooling during CP El Niño events. Conversely, during EP El Niño, the WNPA shifts eastward, and the easterlies are confined around the equator, which helps develop the anti-cyclonic circulation over the Bay of Bengal (BoB). As a result, anomalous low-level divergence induces a strong downdraft over SL. This leads to cloud-free conditions and significantly enhanced incoming shortwave radiation during EP El Niño events, helping to enhance the SAT warming over SL. In addition, a composite analysis of CP and EP El Niño events demonstrated that strong cool (warm) conditions are prevalent in CP (EP) El Niño decaying spring years. This study highlights two distinct types of El Niño as a significant driver for understanding the SAT variability in Sri Lanka.
El Niño事件与斯里兰卡（SL）地面气温（SAT）之间的关系已被充分记录。然而，两种不同类型的El Niño口味对SL季节性SAT变异性的影响仍有待深入研究。因此，为了确定两种不同类型的El Niño对SL上空SAT的影响，我们分析了1981 - 2020年的再分析和观测数据集。本次研究主要集中在El Niño事件衰减期的北方春季。在中太平洋（CP） El Niño事件衰减阶段，南亚春季存在强烈的SAT变冷，而在东太平洋（EP） El Niño事件衰减阶段，南亚春季强烈的SAT变暖尤为明显。研究发现，北太平洋西部反气旋（WNPA）向西移动的南侧延伸的东风导致了南太平洋和印度东海岸上空的低层辐合。这导致云层条件增强，入射短波辐射减少，从而导致CP El Niño事件期间的强烈冷却。相反，在EP El Niño期间，西西北低压东移，东风被限制在赤道附近，这有助于孟加拉湾（BoB）上空反气旋环流的发展。因此，异常的低层辐散在SL上空引起强烈的下沉气流。这导致在EP El Niño事件期间无云条件和显著增强的入射短波辐射，有助于增强SL上空的SAT变暖。此外，CP和EP El Niño事件的综合分析表明，在CP (EP) El Niño衰减的春季，强烈的冷（暖）条件普遍存在。本研究强调了两种不同类型的El Niño作为理解斯里兰卡SAT变异性的重要驱动因素。
{"title":"Impacts of two types of El Niño events on spring surface air temperature over Sri Lanka","authors":"Pathmarasa Kajakokulan , Raju Attada , Dzung Nguyen-Le , Jasti S. Chowdary","doi":"10.1016/j.dynatmoce.2024.101517","DOIUrl":"10.1016/j.dynatmoce.2024.101517","url":null,"abstract":"<div><div>The relationship between El Niño events and surface air temperature (SAT) over Sri Lanka (SL) has been well documented. However, the impact of the two different types of El Niño flavors on seasonal SAT variability in SL remains to be thoroughly investigated. Therefore, to identify the effect of two different types of El Niño on SAT over SL, we analyzed reanalysis and observational datasets from 1981 to 2020. This study mainly focused on the boreal spring season during the decaying phase of El Niño events. We show the presence of a strong SAT cooling in spring over the SL during the decaying phase of Central Pacific (CP) El Niño events, while intense spring SAT warming over SL is particularly pronounced during the Eastern Pacific (EP) El Niño decaying phase. It is found that low-level convergence over SL and the east coast of India associated with easterlies extending from the southern flank of the westward-shifted Western North Pacific anticyclones (WNPA) lead to updrafts. This results in enhanced cloud conditions and decreased incoming shortwave radiation, thereby causing strong cooling during CP El Niño events. Conversely, during EP El Niño, the WNPA shifts eastward, and the easterlies are confined around the equator, which helps develop the anti-cyclonic circulation over the Bay of Bengal (BoB). As a result, anomalous low-level divergence induces a strong downdraft over SL. This leads to cloud-free conditions and significantly enhanced incoming shortwave radiation during EP El Niño events, helping to enhance the SAT warming over SL. In addition, a composite analysis of CP and EP El Niño events demonstrated that strong cool (warm) conditions are prevalent in CP (EP) El Niño decaying spring years. This study highlights two distinct types of El Niño as a significant driver for understanding the SAT variability in Sri Lanka.</div></div>","PeriodicalId":50563,"journal":{"name":"Dynamics of Atmospheres and Oceans","volume":"109 ","pages":"Article 101517"},"PeriodicalIF":1.9,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143160123","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 : 2024-11-22DOI: 10.1016/j.dynatmoce.2024.101508
Yanjun Qi, Ting Zhong
The convective activity is one of the most important features of the tropics, which is closely related to climate variability on multiple time scales. Observational evidence of the coexistence of different time scales in the variation of tropical convective activity was presented in previous studies. This paper mainly reviews the recent progress of variability of convective system over the Indo-western Pacific sector on diurnal, synoptic, intraseasonal, interannual, and decadal-interdecadal time scales, as well as the associated physical processes. The interannual variability of tropical convective activity is strongly modulated by the anomalous large-scale Walker circulation, which is tied to ENSO event. Periodical intraseasonal oscillations in convection are the prominent feature in the tropical Indo-western Pacific Ocean. The tropical cyclones and monsoonal precipitation occurred at the equator and off-equator are closely linked to the synoptic-scale variation of convective activity, northward- and northwestward-propagating intraseasonal oscillation of convection in the Asian monsoon region during boreal summer. The impact of anomalous tropical convective system and associated large-scale circulation on climate variability is of great importance to surrounding countries in the Asian summer monsoon region.
{"title":"Multi-timescale variability of tropical convection in the Indo-western Pacific Ocean","authors":"Yanjun Qi, Ting Zhong","doi":"10.1016/j.dynatmoce.2024.101508","DOIUrl":"10.1016/j.dynatmoce.2024.101508","url":null,"abstract":"<div><div>The convective activity is one of the most important features of the tropics, which is closely related to climate variability on multiple time scales. Observational evidence of the coexistence of different time scales in the variation of tropical convective activity was presented in previous studies. This paper mainly reviews the recent progress of variability of convective system over the Indo-western Pacific sector on diurnal, synoptic, intraseasonal, interannual, and decadal-interdecadal time scales, as well as the associated physical processes. The interannual variability of tropical convective activity is strongly modulated by the anomalous large-scale Walker circulation, which is tied to ENSO event. Periodical intraseasonal oscillations in convection are the prominent feature in the tropical Indo-western Pacific Ocean. The tropical cyclones and monsoonal precipitation occurred at the equator and off-equator are closely linked to the synoptic-scale variation of convective activity, northward- and northwestward-propagating intraseasonal oscillation of convection in the Asian monsoon region during boreal summer. The impact of anomalous tropical convective system and associated large-scale circulation on climate variability is of great importance to surrounding countries in the Asian summer monsoon region.</div></div>","PeriodicalId":50563,"journal":{"name":"Dynamics of Atmospheres and Oceans","volume":"109 ","pages":"Article 101508"},"PeriodicalIF":1.9,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142743191","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}
This study evaluated the accuracy of six planetary boundary layer (PBL) parameterization schemes in simulating two different seasons of pre-monsoon and monsoon in India's North-East region through the Weather Research and Forecasting (WRF) model. Twelve one-month simulations were conducted with the PBL schemes, six each for April (pre-monsoon) and July (monsoon), and the model outputs were compared against observations. Three non-local schemes, Asymmetric Convective Model (ACM2), Yonsei University (YSU), Shin-Hong (HONG), and three local schemes, Quasi Normal Scale Elimination (QNSE), Mellor Yamada Janjic (MYJ) and Mellor Yamada Nakanishi Nino (MYNN3), were tested. The meteorological variables of temperature, relative humidity (RH), wind speed, wind direction, and rainfall were evaluated, and the performance of each scheme for each meteorological variable is reported. The 2 m temperature (T2) variable was well simulated by ACM2, MYJ in April, and YSU in July, while MYNN3 best simulated the 2 m RH (RH2) during both seasons. 10 m wind speed (WS10) and directions (WD10) were better simulated by MYNN3, HONG and YSU. HONG also best-simulated rainfall in April and MYJ in July. April and July being rainfall periods, an analysis of the schemes’ simulated rainfall frequency was also carried out. Moreover, the PBL schemes were also ranked, considering their combined performance with all the above meteorological parameters. While considering both the seasons and all meteorological variables, the scale-aware scheme, HONG, was the best scheme and can be used to simulate both seasons. Additionally, an in-depth analysis of surface and atmospheric parameters was also carried out to reason the simulated meteorology. QNSE expends the highest amount of its surface energy through surface evaporation, leading to the lowest surface skin temperature and T2 predictions. In contrast, MYNN3 produced the lowest mixing, which caused the moistest boundary layer, highest RH, cloud cover, and highly overestimated rainfall. Besides evaluation, which will help to choose a suitable PBL scheme for weather predictions in this region, this study also identifies the characteristics and deficiencies of PBL and surface layer schemes for improvement.
{"title":"Impact of boundary layer parameterizations on simulated seasonal meteorology over North-East India","authors":"Neeldip Barman , Sharad Gokhale , Dewashish Tiwari","doi":"10.1016/j.dynatmoce.2024.101505","DOIUrl":"10.1016/j.dynatmoce.2024.101505","url":null,"abstract":"<div><div>This study evaluated the accuracy of six planetary boundary layer (PBL) parameterization schemes in simulating two different seasons of pre-monsoon and monsoon in India's North-East region through the Weather Research and Forecasting (WRF) model. Twelve one-month simulations were conducted with the PBL schemes, six each for April (pre-monsoon) and July (monsoon), and the model outputs were compared against observations. Three non-local schemes, Asymmetric Convective Model (ACM2), Yonsei University (YSU), Shin-Hong (HONG), and three local schemes, Quasi Normal Scale Elimination (QNSE), Mellor Yamada Janjic (MYJ) and Mellor Yamada Nakanishi Nino (MYNN3), were tested. The meteorological variables of temperature, relative humidity (RH), wind speed, wind direction, and rainfall were evaluated, and the performance of each scheme for each meteorological variable is reported. The 2 m temperature (T2) variable was well simulated by ACM2, MYJ in April, and YSU in July, while MYNN3 best simulated the 2 m RH (RH2) during both seasons. 10 m wind speed (WS10) and directions (WD10) were better simulated by MYNN3, HONG and YSU. HONG also best-simulated rainfall in April and MYJ in July. April and July being rainfall periods, an analysis of the schemes’ simulated rainfall frequency was also carried out. Moreover, the PBL schemes were also ranked, considering their combined performance with all the above meteorological parameters. While considering both the seasons and all meteorological variables, the scale-aware scheme, HONG, was the best scheme and can be used to simulate both seasons. Additionally, an in-depth analysis of surface and atmospheric parameters was also carried out to reason the simulated meteorology. QNSE expends the highest amount of its surface energy through surface evaporation, leading to the lowest surface skin temperature and T2 predictions. In contrast, MYNN3 produced the lowest mixing, which caused the moistest boundary layer, highest RH, cloud cover, and highly overestimated rainfall. Besides evaluation, which will help to choose a suitable PBL scheme for weather predictions in this region, this study also identifies the characteristics and deficiencies of PBL and surface layer schemes for improvement.</div></div>","PeriodicalId":50563,"journal":{"name":"Dynamics of Atmospheres and Oceans","volume":"108 ","pages":"Article 101505"},"PeriodicalIF":1.9,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652131","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 : 2024-11-09DOI: 10.1016/j.dynatmoce.2024.101507
Ibrahim Shaik , P.V. Nagamani , Yash Manmode , Sandesh Yadav , Venkatesh Degala , G. Srinivasa Rao
Sea Surface Nitrate (SSN) is crucial for assessing phytoplankton growth and the initiation of new production within the marine environment. Precise estimation of SSN concentrations plays a significant role in understanding marine ecosystem dynamics. In this study, the deep learning model TabularNet (TabNet) was assessed using quality-controlled in-situ measurements from the Global Ocean Data Analysis Project (GLODAP). These measurements included Sea Surface Temperature (SST), Sea Surface Salinity (SSS), Chlorophyll-a concentration (Chla), and nitrate, collected from various regions of the global ocean to achieve accurate SSN estimation. The TabNet model demonstrated superior performance and robustness, achieving accurate global SSN estimations using satellite data. The model yielded a root mean square error (RMSE) of 2.02 μmol/kg, a mean bias (MB) of −0.32 μmol/kg, a mean ratio (MR) of 0.78, and a coefficient of determination (R2) of 0.96. Furthermore, a comparative analysis of TabNet against Random Forest (RF) and Feed Forward Neural Network (FFNN) models was conducted. The results highlighted the robust performance of TabNet in accurately estimating SSN dynamics. TabNet effectively utilized in-situ and satellite data, providing accurate SSN dynamics. This technique offers valuable insights for monitoring global surface ocean nitrate dynamics, enhancing our ability to understand and manage marine ecosystems.
{"title":"Mapping the dynamics of global sea surface nitrate using ocean color data","authors":"Ibrahim Shaik , P.V. Nagamani , Yash Manmode , Sandesh Yadav , Venkatesh Degala , G. Srinivasa Rao","doi":"10.1016/j.dynatmoce.2024.101507","DOIUrl":"10.1016/j.dynatmoce.2024.101507","url":null,"abstract":"<div><div>Sea Surface Nitrate (SSN) is crucial for assessing phytoplankton growth and the initiation of new production within the marine environment. Precise estimation of SSN concentrations plays a significant role in understanding marine ecosystem dynamics. In this study, the deep learning model TabularNet (TabNet) was assessed using quality-controlled in-situ measurements from the Global Ocean Data Analysis Project (GLODAP). These measurements included Sea Surface Temperature (SST), Sea Surface Salinity (SSS), Chlorophyll-a concentration (Chla), and nitrate, collected from various regions of the global ocean to achieve accurate SSN estimation. The TabNet model demonstrated superior performance and robustness, achieving accurate global SSN estimations using satellite data. The model yielded a root mean square error (RMSE) of 2.02 μmol/kg, a mean bias (MB) of −0.32 μmol/kg, a mean ratio (MR) of 0.78, and a coefficient of determination (R<sup>2</sup>) of 0.96. Furthermore, a comparative analysis of TabNet against Random Forest (RF) and Feed Forward Neural Network (FFNN) models was conducted. The results highlighted the robust performance of TabNet in accurately estimating SSN dynamics. TabNet effectively utilized in-situ and satellite data, providing accurate SSN dynamics. This technique offers valuable insights for monitoring global surface ocean nitrate dynamics, enhancing our ability to understand and manage marine ecosystems.</div></div>","PeriodicalId":50563,"journal":{"name":"Dynamics of Atmospheres and Oceans","volume":"108 ","pages":"Article 101507"},"PeriodicalIF":1.9,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652132","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 : 2024-11-03DOI: 10.1016/j.dynatmoce.2024.101506
Mingze Ji , Xiongbo Zheng , Fangli Qiao , Jingyi Lu , He Liu , Xiaole Li
Mesoscale vortices are major carriers of oceanic material and energy transfer, transporting large amounts of high-energy, temperature-anomalous water bodies during their movement. This significantly impacts both the ocean and the atmosphere. Based on the distribution of the North Brazil Curren rings and the Lesser Antilles in the eastern Caribbean Sea, we use the Regional Ocean Model System ocean circulation model to construct an idealized vortex. Simulations are conducted by varying the distances between the two islands and the scales of the islands to analyze how different parameters affect the vortex path and structural evolution. Using theoretical derivation and numerical simulation results, we construct a dimensionless parameter involving vortex diameter, island diameter, and the distance between the islands to determine the conditions under which vortex splitting occurs. The reliability of this dimensionless parameter is verified using experimental data and satellite data from St. Vincent and Barbados from April 6 to May 6, 2000.
{"title":"The vortex splitting process from interaction between a mesoscale vortex and two islands","authors":"Mingze Ji , Xiongbo Zheng , Fangli Qiao , Jingyi Lu , He Liu , Xiaole Li","doi":"10.1016/j.dynatmoce.2024.101506","DOIUrl":"10.1016/j.dynatmoce.2024.101506","url":null,"abstract":"<div><div>Mesoscale vortices are major carriers of oceanic material and energy transfer, transporting large amounts of high-energy, temperature-anomalous water bodies during their movement. This significantly impacts both the ocean and the atmosphere. Based on the distribution of the North Brazil Curren rings and the Lesser Antilles in the eastern Caribbean Sea, we use the Regional Ocean Model System ocean circulation model to construct an idealized vortex. Simulations are conducted by varying the distances between the two islands and the scales of the islands to analyze how different parameters affect the vortex path and structural evolution. Using theoretical derivation and numerical simulation results, we construct a dimensionless parameter involving vortex diameter, island diameter, and the distance between the islands to determine the conditions under which vortex splitting occurs. The reliability of this dimensionless parameter is verified using experimental data and satellite data from St. Vincent and Barbados from April 6 to May 6, 2000.</div></div>","PeriodicalId":50563,"journal":{"name":"Dynamics of Atmospheres and Oceans","volume":"108 ","pages":"Article 101506"},"PeriodicalIF":1.9,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652130","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}
An ensemble of forecasts is necessary to identify the uncertainty in predicting a non-linear system like climate. While ensemble averages are often used to represent the mean state and diagnose physical mechanisms, they can lead to information loss and inaccurate assessment of the model’s characteristics. Here, we highlight an intriguing case in the seasonal hindcasts of the Climate Forecast System version 2 (CFSv2). While all ensemble members often agree on the sign of predicted El Niño Southern Oscillation (ENSO) for a particular season, non-ENSO climate forcings, although present in some of the individual members, are disparate. As a result, an ensemble mean retains ENSO anomalies while diminishing non-ENSO signals. This difference between ENSO and non-ENSO signals significantly influences moisture convergence and Indian summer monsoon rainfall (ISMR). This stronger influence of ENSO on seasonal predictions increases ENSO–ISMR correlation in ensemble mean seasonal hindcasts. Thus, this discrepancy in the ENSO–ISMR relationship is not present in the individual ensemble members, considered individually or together (without averaging) as independent realizations. Therefore, adequate care should be taken while evaluating physical mechanisms of teleconnection in ensemble mean predictions that can often be skewed due to constructive or destructive superposition of different impacts.
{"title":"The curious case of a strong relationship between ENSO and Indian summer monsoon in CFSv2 model","authors":"Priyanshi Singhai , Arindam Chakraborty , Kaushik Jana , Kavirajan Rajendran , Sajani Surendran , Kathy Pegion","doi":"10.1016/j.dynatmoce.2024.101504","DOIUrl":"10.1016/j.dynatmoce.2024.101504","url":null,"abstract":"<div><div>An ensemble of forecasts is necessary to identify the uncertainty in predicting a non-linear system like climate. While ensemble averages are often used to represent the mean state and diagnose physical mechanisms, they can lead to information loss and inaccurate assessment of the model’s characteristics. Here, we highlight an intriguing case in the seasonal hindcasts of the Climate Forecast System version 2 (CFSv2). While all ensemble members often agree on the sign of predicted El Niño Southern Oscillation (ENSO) for a particular season, non-ENSO climate forcings, although present in some of the individual members, are disparate. As a result, an ensemble mean retains ENSO anomalies while diminishing non-ENSO signals. This difference between ENSO and non-ENSO signals significantly influences moisture convergence and Indian summer monsoon rainfall (ISMR). This stronger influence of ENSO on seasonal predictions increases ENSO–ISMR correlation in ensemble mean seasonal hindcasts. Thus, this discrepancy in the ENSO–ISMR relationship is not present in the individual ensemble members, considered individually or together (without averaging) as independent realizations. Therefore, adequate care should be taken while evaluating physical mechanisms of teleconnection in ensemble mean predictions that can often be skewed due to constructive or destructive superposition of different impacts.</div></div>","PeriodicalId":50563,"journal":{"name":"Dynamics of Atmospheres and Oceans","volume":"108 ","pages":"Article 101504"},"PeriodicalIF":1.9,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593276","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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