Here we propose a new concept,the Pan-Asian monsoon,and use empirical orthogonal function (EOF) analysis and linear regression approach to define it and to analyze the monsoon-related rainfall variability.The Pan-Asia...Here we propose a new concept,the Pan-Asian monsoon,and use empirical orthogonal function (EOF) analysis and linear regression approach to define it and to analyze the monsoon-related rainfall variability.The Pan-Asian monsoon is referred to as the monsoon occurred over the great region (60°E-140°E,10°S-35°N),consisting of the Indian monsoon,Southeast Asian monsoon,East Asian monsoon,and Western North Pacific monsoon.The Pan-Asian monsoon region is the principal region of the summer rainfall over the Asian-Pacific monsoon region and is also water vapor channel connecting several Asian-Pacific sub-monsoon systems.The first EOF mode of the Pan-Asian monsoon precipitation (PAMP_F) shows a meridional tripole pattern with more (less) rainfall zonal belt over the Bay of Bengal (BOB),the Indo-China Peninsula,South China,the South China Sea (SCS),Philippines and the Philippine Sea,and less (more) rainfall on both sides.The first rainfall mode is associated with the weakened Somali cross-equatorial flows,enhanced southerly over the eastern coast of Australia,and strengthened westerly over the tropical Pacific.The first EOF rainfall mode shows a close relationship with the simultaneous El Nio-Southern Oscillation (ENSO) and Pacific South America (PSA).The preceding spring and simultaneous summer Antarctic Oscillation (AAO) in the western Hemisphere (AAO in Pacific) has a connection with the first summer rainfall mode of the Pan-Asian monsoon.Because the main influence factors are over the Pacific,the first rainfall mode is named as the Pacific mode.The second mode of the Pan-Asian monsoon precipitation (PAMP_S) shows a dipole pattern from northeast to southwest,which is associated with the weakened Somali cross-equatorial flows,enhanced easterlies over the Maritime Continent,and weak easterly over the tropical Pacific.The second rainfall model has a close relationship with the atmospheric convection activity and the sea surface temperature variability over the Maritime Continent and South Indian Ocean.Because the influ展开更多
A previously developed hybrid coupled model(HCM)is composed of an intermediate tropical Pacific Ocean model and a global atmospheric general circulation model(AGCM),denoted as HCMAGCM.In this study,different El Ni...A previously developed hybrid coupled model(HCM)is composed of an intermediate tropical Pacific Ocean model and a global atmospheric general circulation model(AGCM),denoted as HCMAGCM.In this study,different El Niño flavors,namely the Eastern-Pacific(EP)and Central-Pacific(CP)types,and the associated global atmospheric teleconnections are examined in a 1000-yr control simulation of the HCMAGCM.The HCMAGCM indicates profoundly different characteristics among EP and CP El Niño events in terms of related oceanic and atmospheric variables in the tropical Pacific,including the amplitude and spatial patterns of sea surface temperature(SST),zonal wind stress,and precipitation anomalies.An SST budget analysis indicates that the thermocline feedback and zonal advective feedback dominantly contribute to the growth of EP and CP El Niño events,respectively.Corresponding to the shifts in the tropical rainfall and deep convection during EP and CP El Niño events,the model also reproduces the differences in the extratropical atmospheric responses during the boreal winter.In particular,the EP El Niño tends to be dominant in exciting a poleward wave train pattern to the Northern Hemisphere,while the CP El Niño tends to preferably produce a wave train similar to the Pacific North American(PNA)pattern.As a result,different climatic impacts exist in North American regions,with a warm-north and cold-south pattern during an EP El Niño and a warm-northeast and cold-southwest pattern during a CP El Niño,respectively.This modeling result highlights the importance of internal natural processes within the tropical Pacific as they relate to the genesis of ENSO diversity because the active ocean–atmosphere coupling is allowed only in the tropical Pacific within the framework of the HCMAGCM.展开更多
The troubled forecast of El Nio’s onset in2014 requires an explanation as well as an open dialogue with the user community that depends on such an important forecast. A review of the forecasts on the Internet refle...The troubled forecast of El Nio’s onset in2014 requires an explanation as well as an open dialogue with the user community that depends on such an important forecast. A review of the forecasts on the Internet reflects two different perceptions about what transpired. The forecast community suggests they got it right, while the popular media suggests forecasters got it wrong. Why such a gap? The major El Nio that was alluded to by several organizations did not materialize when or even as expected. A science-fed media frenzy took place about an event considered in retrospect to have been an unusual borderline(weak) El Nio event, 'trickiest ever to forecast.'That is understandable, as the science of El Nio is still on a learning curve. But it suggests that the forecasting of El Nio’s onset is still in an experimental phase and not yet operational. Forecasting its onset(as a specific event)should be separated from forecasting its behavior and impacts(as a process) once the onset has been assured.Whenever a forecast is made, someone is responding to it.Therefore, such a distinction is necessary for the benefit of those societies and economic sectors affected by El Nio.展开更多
In this study, we unveil atmospheric circulation anomalies associated with the large-scale tropical teleconnections using National Center for Environmental Prediction (NCEP) reanalysis dataset. Composite analyses have...In this study, we unveil atmospheric circulation anomalies associated with the large-scale tropical teleconnections using National Center for Environmental Prediction (NCEP) reanalysis dataset. Composite analyses have been performed to know the impact of large-scale tropical circulations on the Horn of Africa. The composite analysis performed at the geopotential height of 850 Mb and 200 Mb, and precipitation rate (mm/day) during six strong El Niño and La Niña episodes revealed that the large-scale tropical variability induced climate anomalies in space and time. A substantial decrease in upper-level height (200 Mb) has been observed in the study area during El Niño composite years as compared to the La Niña years. During El Niño conditions, the upper-level divergence initiates low-level vertical motion, thereby enhancing convection, however, during La Niña composite years, nearly contrasting situations are noticed in Belg (February to May) season in Ethiopia. However, geopotential height anomalies at 850 Mb are above-normal during the strong El Niño years, suggesting suppressed convection due to vertical shrinking and enhancement of divergence at the lower level. Compared to the Belg (February to May), geopotential anomalies were generally positive during the Kiremt (June to September) season, thereby suppressing the rainfall, particularly in Southern Ethiopia and Northern Part of Kenya. In contrast, an increase in rainfall was observed during the Belg season (February to May).展开更多
This preliminary study examines the definition problem and challenges of climate forecasting and disaster responses associated with the El Nio costero(coastal) of2017, which developed rapidly with no warning and had...This preliminary study examines the definition problem and challenges of climate forecasting and disaster responses associated with the El Nio costero(coastal) of2017, which developed rapidly with no warning and had catastrophic effects in Peru. Such a localized El Nio was not documented since 1925. An initial review suggests that in addition to the characteristics of the event(surprise),government responses may have been inadequate(as media reported) because of conflicting forecast reports(U.S. and Peru), which provoked a hydrometeorological debate and stifled decision making. Partly to blame was the El Nio definition problem, which can cause uncertainty and affect perception of risk, depending on which region of the equatorial Pacific one uses to identify an event. Responses were further complicated by the fact that some regions within Peru were experiencing drought prior to the El Nio costero's onset and impacts from the El Nio 2015–2016 were less than expected. Furthermore, a new government was in place, which may have hindered action. Thus, El Nio costero provides lessons to heed, not only with respect to the forecast information, but also with reference to the context of the forecast and disaster setting, which can influence disaster responses to hydrometeorological threats.展开更多
The correlation of the Southern Oscillation Index (SOI), Pacific Decadal Oscillation (PDO), Pacific North American Oscillation (PNA), Arctic Oscillation (AO), and Scandinavia (SCAND) indices with winter (DJF) temperat...The correlation of the Southern Oscillation Index (SOI), Pacific Decadal Oscillation (PDO), Pacific North American Oscillation (PNA), Arctic Oscillation (AO), and Scandinavia (SCAND) indices with winter (DJF) temperature and precipitation for the period of 1943 to 2011 was analyzed to study climate change and variability of Yellowknife, NWT. SOI correlated negatively with both temperature (r = -0.14) and precipitation (r = -0.06) causing colder, drier conditions during La Nina and warmer, wetter conditions during El Nino. PDO was shown to have a strong positive correlation with both temperature (r = 0.60) and precipitation (r = 0.33) causing warmer, wetter weather in the positive phase and colder, drier weather in the negative phase. PNA showed the strongest positive correlation for both temperature (r = 0.69) and precipitation (r = 0.37) causing very warm and wet conditions in the positive phase and very cold and dry conditions during the negative phase. AO correlated negatively with temperature (r = -0.04) and positively with precipitation (r = 0.24) causing colder, wetter conditions in the positive phase and warmer, drier conditions in the negative phase. Finally SCAND was shown to have a weak negative correlation with both temperature (r = -0.10) and precipitation (r = -0.18). Sunspot area showed a strong negative correlation (r = -0.30) with temperature and a very weak positive correlation (r = 0.07) with total annual precipitation. Yellowknife’s average annual temperature and precipitation has increased by 2.5°C and 120 mm, respectively throughout the past 69 years.展开更多
Monthly mean summer (DJF) temperature and precipitation from Global Historical Climate Network (GHCN-V3) for the period of 1870-2011, are analyzed to assess the role of teleconnections on climate of Darwin, Australia....Monthly mean summer (DJF) temperature and precipitation from Global Historical Climate Network (GHCN-V3) for the period of 1870-2011, are analyzed to assess the role of teleconnections on climate of Darwin, Australia. Indices of El Nino-Southern Oscillation (ENSO), Antarctic Oscillation (AAO), Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), Arctic Oscillation (AO), and Pacific North American Oscillation (PNA) are extracted from monthly means and compared with climatic data of Darwin. Most of these climate modes are shown to have a strong influence on the monthly mean summer temperature and precipitation. ENSO is shown to have a positive relationship with the amount of precipitation received and a negative relationship with the temperature. Where an El Nino event produces warmer drier conditions and a La Nina event produces colder wetter conditions. The AAO is shown to cause cold and dry conditions during the positive phase and warm and wet conditions during the negative phase. The PDO is shown to cause El Nino like condition during the positive phase causing warmer, drier weather, and La Nina like conditions during the negative phase causing cooler, wetter weather. Through the analysis it is also shown that the NAO, AO, and PNA have little effect on the temperature and precipitation patterns of Darwin.展开更多
Previous research has identified specific areas of frequent tropical cyclone activity in the North Atlantic basin. This study examines long-term and decadal spatio-temporal patterns of Atlantic tropical cyclone freque...Previous research has identified specific areas of frequent tropical cyclone activity in the North Atlantic basin. This study examines long-term and decadal spatio-temporal patterns of Atlantic tropical cyclone frequencies from 1944 to 2009, and analyzes categorical and decadal centroid patterns using kernel density estimation (KDE) and centrographic statistics. Results corroborate previous research which has suggested that the Bermuda-Azores anticyclone plays an integral role in the direction of tropical cyclone tracks. Other teleconnections such as the North Atlantic Oscillation (NAO) may also have an impact on tropical cyclone tracks, but at a different temporal resolution. Results expand on existing knowledge of the spatial trends of tropical cyclones based on storm category and time through the use of spatial statistics. Overall, location of peak frequency varies by tropical cyclone category, with stronger storms being more concentrated in narrow regions of the southern Caribbean Sea and Gulf of Mexico, while weaker storms occur in a much larger area that encompasses much of the Caribbean Sea, Gulf of Mexico, and Atlantic Ocean off of the east coast of the United States. Additionally, the decadal centroids of tropical cyclone tracks have oscillated over a large area of the Atlantic Ocean for much of recorded history. Data collected since 1944 can be analyzed confidently to reveal these patterns.展开更多
Existing limited understanding on the teleconnections between ocean-atmosphere coupled phenomena and drought occurrences in Ethiopia has been undermining the decisions and interventions related to climate change adapt...Existing limited understanding on the teleconnections between ocean-atmosphere coupled phenomena and drought occurrences in Ethiopia has been undermining the decisions and interventions related to climate change adaptation and mitigation. The two drought indices Standardized Precipitation Index and Reconnaissance Drought Index were used for correlation and lag correlation with global indices El-Nino Southern Oscillation, Oceanic Nino, Indian Ocean Dipole and Pacific Decadal Oscillation. The indices were obtained from their respective database websites of the National Center for Environmental Prediction. Historical EL-Nino and La-Nina years and Ethiopian drought years were collected from literatures. Meteorological data on seasonal mean rainfall, maximum and minimum temperatures from 1916-2016 were collected from Tigray regional meteorology agency. In addition, the Cru/ Model data were collected from KNMI climate explorer. The analysis results the strong correlations of global indices Nino3.4, IOD and PDO with local indices for April to June rainy season while SOI and IOD indices for July-Sep. The positive correlation of indices weakened and/or dislocated the rain-producing components for main rainy season, while those systems enhanced in low rain season. This shows global indices alter rain fall distribution & conveys Meteorological and Agricultural drought. The study revealed that, in addition to El Nino impacts, other events such as PDO, SOI and IOD are important factors for triggering meteorological and agricultural droughts in Tigray region of Ethiopia. This information has multiple implications, among others, improves seasonal forecast to make informed decisions.展开更多
The apparent teleconnection between cosmic-ray muon flux over a base point in the Caribbean is discussed against the background of an extensive record of indices representing large-scale climatic phenomena, but limite...The apparent teleconnection between cosmic-ray muon flux over a base point in the Caribbean is discussed against the background of an extensive record of indices representing large-scale climatic phenomena, but limited cosmic-ray muon flux data. Many investigators have shown that large-scale climate phenomena influence sub-seasonal and seasonal climate variability, especially in the northern hemisphere and their impacts on the Caribbean are well documented. These climatic phenomena that impact the Caribbean include, but are not limited to, the El Nino Southern Oscillation, the Quasi-Biennial Oscillation, the North Atlantic Oscillation, and the Arctic Oscillation which is now being investigated. Although strong statistical correlation between variables over non-contiguous regions are not absolute as proof of teleconnections, the correlation strength can be used as an indication of its existence. The data gathered at the Mona Campus of the University of the West Indies, in Jamaica, using a simple QuarkNet 6000 muon detector over the period September 2011 to September 2013, showed an apparent significant relationship with these climatic indices. This suggests that cosmic-ray muon flux might be linked to the behavior of the climate phenomena and therefore can be used as a climate or meteorological index over the Caribbean.展开更多
From the Global Historical Climate Network (GHCN-V3), monthly mean summer (DJF) temperature (1856-2012) and total precipitation (1861-2012) are analyzed in correlation with four climate modes and sunspot number to bet...From the Global Historical Climate Network (GHCN-V3), monthly mean summer (DJF) temperature (1856-2012) and total precipitation (1861-2012) are analyzed in correlation with four climate modes and sunspot number to better understand the role of teleconnections on Buenos Aires’ (Argentina) climate. A general increase in temperature and precipitation was observed. Temperature has increased by about 1.8°C and precipitation has increased by about 300 mm in the past century and a half. Indices of Arctic Oscillation (AO), Pacific North American (PNA), Antarctic Oscillation (AAO), and El Nino-Southern Oscillation (ENSO) are evaluated to study their effects on wheat and corn production and export. AO and PNA show strong relationships with precipitation and temperature received. AAO and ENSO show strong negative correlations with precipitation patterns and weak correlations with temperature. Sunspot Number shows a positive correlation with temperature. ENSO phases are strongly linked with the wheat and corn production and export;during El Nino Buenos Aires tends to experience extremely wet summer weather, causing soggy fields and extremely dry summer weather during La Nina causing drought. Both of these conditions result in reducing wheat and corn production and export.展开更多
基金supported by National Basic Research Program of China (Grant No. 2009CB421406)National Natural Science Foundation of China (Grant No. 40905041)+1 种基金Knowledge Innovation Program of Chinese Academy of Sciences (Grant No. KZCX2-YW-QN202)National Key Scientific Research Project of Global Changes Research of China (Grant No. 2010CB950304)
文摘Here we propose a new concept,the Pan-Asian monsoon,and use empirical orthogonal function (EOF) analysis and linear regression approach to define it and to analyze the monsoon-related rainfall variability.The Pan-Asian monsoon is referred to as the monsoon occurred over the great region (60°E-140°E,10°S-35°N),consisting of the Indian monsoon,Southeast Asian monsoon,East Asian monsoon,and Western North Pacific monsoon.The Pan-Asian monsoon region is the principal region of the summer rainfall over the Asian-Pacific monsoon region and is also water vapor channel connecting several Asian-Pacific sub-monsoon systems.The first EOF mode of the Pan-Asian monsoon precipitation (PAMP_F) shows a meridional tripole pattern with more (less) rainfall zonal belt over the Bay of Bengal (BOB),the Indo-China Peninsula,South China,the South China Sea (SCS),Philippines and the Philippine Sea,and less (more) rainfall on both sides.The first rainfall mode is associated with the weakened Somali cross-equatorial flows,enhanced southerly over the eastern coast of Australia,and strengthened westerly over the tropical Pacific.The first EOF rainfall mode shows a close relationship with the simultaneous El Nio-Southern Oscillation (ENSO) and Pacific South America (PSA).The preceding spring and simultaneous summer Antarctic Oscillation (AAO) in the western Hemisphere (AAO in Pacific) has a connection with the first summer rainfall mode of the Pan-Asian monsoon.Because the main influence factors are over the Pacific,the first rainfall mode is named as the Pacific mode.The second mode of the Pan-Asian monsoon precipitation (PAMP_S) shows a dipole pattern from northeast to southwest,which is associated with the weakened Somali cross-equatorial flows,enhanced easterlies over the Maritime Continent,and weak easterly over the tropical Pacific.The second rainfall model has a close relationship with the atmospheric convection activity and the sea surface temperature variability over the Maritime Continent and South Indian Ocean.Because the influ
基金supported by the National Natural Science Foundation of China(NSFCGrant No.42275061)+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB40000000)the Laoshan Laboratory(Grant No.LSKJ202202404)the NSFC(Grant No.42030410)the Startup Foundation for Introducing Talent of Nanjing University of Information Science and Technology.
文摘A previously developed hybrid coupled model(HCM)is composed of an intermediate tropical Pacific Ocean model and a global atmospheric general circulation model(AGCM),denoted as HCMAGCM.In this study,different El Niño flavors,namely the Eastern-Pacific(EP)and Central-Pacific(CP)types,and the associated global atmospheric teleconnections are examined in a 1000-yr control simulation of the HCMAGCM.The HCMAGCM indicates profoundly different characteristics among EP and CP El Niño events in terms of related oceanic and atmospheric variables in the tropical Pacific,including the amplitude and spatial patterns of sea surface temperature(SST),zonal wind stress,and precipitation anomalies.An SST budget analysis indicates that the thermocline feedback and zonal advective feedback dominantly contribute to the growth of EP and CP El Niño events,respectively.Corresponding to the shifts in the tropical rainfall and deep convection during EP and CP El Niño events,the model also reproduces the differences in the extratropical atmospheric responses during the boreal winter.In particular,the EP El Niño tends to be dominant in exciting a poleward wave train pattern to the Northern Hemisphere,while the CP El Niño tends to preferably produce a wave train similar to the Pacific North American(PNA)pattern.As a result,different climatic impacts exist in North American regions,with a warm-north and cold-south pattern during an EP El Niño and a warm-northeast and cold-southwest pattern during a CP El Niño,respectively.This modeling result highlights the importance of internal natural processes within the tropical Pacific as they relate to the genesis of ENSO diversity because the active ocean–atmosphere coupling is allowed only in the tropical Pacific within the framework of the HCMAGCM.
文摘The troubled forecast of El Nio’s onset in2014 requires an explanation as well as an open dialogue with the user community that depends on such an important forecast. A review of the forecasts on the Internet reflects two different perceptions about what transpired. The forecast community suggests they got it right, while the popular media suggests forecasters got it wrong. Why such a gap? The major El Nio that was alluded to by several organizations did not materialize when or even as expected. A science-fed media frenzy took place about an event considered in retrospect to have been an unusual borderline(weak) El Nio event, 'trickiest ever to forecast.'That is understandable, as the science of El Nio is still on a learning curve. But it suggests that the forecasting of El Nio’s onset is still in an experimental phase and not yet operational. Forecasting its onset(as a specific event)should be separated from forecasting its behavior and impacts(as a process) once the onset has been assured.Whenever a forecast is made, someone is responding to it.Therefore, such a distinction is necessary for the benefit of those societies and economic sectors affected by El Nio.
基金the Research Council of Norway through the project COMBINED[grant number 328935]the contribution of Professor Yongqi Gao(1965-2021)to the design of the experimentsThe CAM6-Nor simulations were performed on resources provided by UNINETT Sigma2—the National Infrastructure for High Performance Computing and Data Storage in Norway(nn2343k,NS9015K).
文摘In this study, we unveil atmospheric circulation anomalies associated with the large-scale tropical teleconnections using National Center for Environmental Prediction (NCEP) reanalysis dataset. Composite analyses have been performed to know the impact of large-scale tropical circulations on the Horn of Africa. The composite analysis performed at the geopotential height of 850 Mb and 200 Mb, and precipitation rate (mm/day) during six strong El Niño and La Niña episodes revealed that the large-scale tropical variability induced climate anomalies in space and time. A substantial decrease in upper-level height (200 Mb) has been observed in the study area during El Niño composite years as compared to the La Niña years. During El Niño conditions, the upper-level divergence initiates low-level vertical motion, thereby enhancing convection, however, during La Niña composite years, nearly contrasting situations are noticed in Belg (February to May) season in Ethiopia. However, geopotential height anomalies at 850 Mb are above-normal during the strong El Niño years, suggesting suppressed convection due to vertical shrinking and enhancement of divergence at the lower level. Compared to the Belg (February to May), geopotential anomalies were generally positive during the Kiremt (June to September) season, thereby suppressing the rainfall, particularly in Southern Ethiopia and Northern Part of Kenya. In contrast, an increase in rainfall was observed during the Belg season (February to May).
文摘This preliminary study examines the definition problem and challenges of climate forecasting and disaster responses associated with the El Nio costero(coastal) of2017, which developed rapidly with no warning and had catastrophic effects in Peru. Such a localized El Nio was not documented since 1925. An initial review suggests that in addition to the characteristics of the event(surprise),government responses may have been inadequate(as media reported) because of conflicting forecast reports(U.S. and Peru), which provoked a hydrometeorological debate and stifled decision making. Partly to blame was the El Nio definition problem, which can cause uncertainty and affect perception of risk, depending on which region of the equatorial Pacific one uses to identify an event. Responses were further complicated by the fact that some regions within Peru were experiencing drought prior to the El Nio costero's onset and impacts from the El Nio 2015–2016 were less than expected. Furthermore, a new government was in place, which may have hindered action. Thus, El Nio costero provides lessons to heed, not only with respect to the forecast information, but also with reference to the context of the forecast and disaster setting, which can influence disaster responses to hydrometeorological threats.
文摘The correlation of the Southern Oscillation Index (SOI), Pacific Decadal Oscillation (PDO), Pacific North American Oscillation (PNA), Arctic Oscillation (AO), and Scandinavia (SCAND) indices with winter (DJF) temperature and precipitation for the period of 1943 to 2011 was analyzed to study climate change and variability of Yellowknife, NWT. SOI correlated negatively with both temperature (r = -0.14) and precipitation (r = -0.06) causing colder, drier conditions during La Nina and warmer, wetter conditions during El Nino. PDO was shown to have a strong positive correlation with both temperature (r = 0.60) and precipitation (r = 0.33) causing warmer, wetter weather in the positive phase and colder, drier weather in the negative phase. PNA showed the strongest positive correlation for both temperature (r = 0.69) and precipitation (r = 0.37) causing very warm and wet conditions in the positive phase and very cold and dry conditions during the negative phase. AO correlated negatively with temperature (r = -0.04) and positively with precipitation (r = 0.24) causing colder, wetter conditions in the positive phase and warmer, drier conditions in the negative phase. Finally SCAND was shown to have a weak negative correlation with both temperature (r = -0.10) and precipitation (r = -0.18). Sunspot area showed a strong negative correlation (r = -0.30) with temperature and a very weak positive correlation (r = 0.07) with total annual precipitation. Yellowknife’s average annual temperature and precipitation has increased by 2.5°C and 120 mm, respectively throughout the past 69 years.
文摘Monthly mean summer (DJF) temperature and precipitation from Global Historical Climate Network (GHCN-V3) for the period of 1870-2011, are analyzed to assess the role of teleconnections on climate of Darwin, Australia. Indices of El Nino-Southern Oscillation (ENSO), Antarctic Oscillation (AAO), Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), Arctic Oscillation (AO), and Pacific North American Oscillation (PNA) are extracted from monthly means and compared with climatic data of Darwin. Most of these climate modes are shown to have a strong influence on the monthly mean summer temperature and precipitation. ENSO is shown to have a positive relationship with the amount of precipitation received and a negative relationship with the temperature. Where an El Nino event produces warmer drier conditions and a La Nina event produces colder wetter conditions. The AAO is shown to cause cold and dry conditions during the positive phase and warm and wet conditions during the negative phase. The PDO is shown to cause El Nino like condition during the positive phase causing warmer, drier weather, and La Nina like conditions during the negative phase causing cooler, wetter weather. Through the analysis it is also shown that the NAO, AO, and PNA have little effect on the temperature and precipitation patterns of Darwin.
文摘Previous research has identified specific areas of frequent tropical cyclone activity in the North Atlantic basin. This study examines long-term and decadal spatio-temporal patterns of Atlantic tropical cyclone frequencies from 1944 to 2009, and analyzes categorical and decadal centroid patterns using kernel density estimation (KDE) and centrographic statistics. Results corroborate previous research which has suggested that the Bermuda-Azores anticyclone plays an integral role in the direction of tropical cyclone tracks. Other teleconnections such as the North Atlantic Oscillation (NAO) may also have an impact on tropical cyclone tracks, but at a different temporal resolution. Results expand on existing knowledge of the spatial trends of tropical cyclones based on storm category and time through the use of spatial statistics. Overall, location of peak frequency varies by tropical cyclone category, with stronger storms being more concentrated in narrow regions of the southern Caribbean Sea and Gulf of Mexico, while weaker storms occur in a much larger area that encompasses much of the Caribbean Sea, Gulf of Mexico, and Atlantic Ocean off of the east coast of the United States. Additionally, the decadal centroids of tropical cyclone tracks have oscillated over a large area of the Atlantic Ocean for much of recorded history. Data collected since 1944 can be analyzed confidently to reveal these patterns.
文摘Existing limited understanding on the teleconnections between ocean-atmosphere coupled phenomena and drought occurrences in Ethiopia has been undermining the decisions and interventions related to climate change adaptation and mitigation. The two drought indices Standardized Precipitation Index and Reconnaissance Drought Index were used for correlation and lag correlation with global indices El-Nino Southern Oscillation, Oceanic Nino, Indian Ocean Dipole and Pacific Decadal Oscillation. The indices were obtained from their respective database websites of the National Center for Environmental Prediction. Historical EL-Nino and La-Nina years and Ethiopian drought years were collected from literatures. Meteorological data on seasonal mean rainfall, maximum and minimum temperatures from 1916-2016 were collected from Tigray regional meteorology agency. In addition, the Cru/ Model data were collected from KNMI climate explorer. The analysis results the strong correlations of global indices Nino3.4, IOD and PDO with local indices for April to June rainy season while SOI and IOD indices for July-Sep. The positive correlation of indices weakened and/or dislocated the rain-producing components for main rainy season, while those systems enhanced in low rain season. This shows global indices alter rain fall distribution & conveys Meteorological and Agricultural drought. The study revealed that, in addition to El Nino impacts, other events such as PDO, SOI and IOD are important factors for triggering meteorological and agricultural droughts in Tigray region of Ethiopia. This information has multiple implications, among others, improves seasonal forecast to make informed decisions.
文摘The apparent teleconnection between cosmic-ray muon flux over a base point in the Caribbean is discussed against the background of an extensive record of indices representing large-scale climatic phenomena, but limited cosmic-ray muon flux data. Many investigators have shown that large-scale climate phenomena influence sub-seasonal and seasonal climate variability, especially in the northern hemisphere and their impacts on the Caribbean are well documented. These climatic phenomena that impact the Caribbean include, but are not limited to, the El Nino Southern Oscillation, the Quasi-Biennial Oscillation, the North Atlantic Oscillation, and the Arctic Oscillation which is now being investigated. Although strong statistical correlation between variables over non-contiguous regions are not absolute as proof of teleconnections, the correlation strength can be used as an indication of its existence. The data gathered at the Mona Campus of the University of the West Indies, in Jamaica, using a simple QuarkNet 6000 muon detector over the period September 2011 to September 2013, showed an apparent significant relationship with these climatic indices. This suggests that cosmic-ray muon flux might be linked to the behavior of the climate phenomena and therefore can be used as a climate or meteorological index over the Caribbean.
文摘From the Global Historical Climate Network (GHCN-V3), monthly mean summer (DJF) temperature (1856-2012) and total precipitation (1861-2012) are analyzed in correlation with four climate modes and sunspot number to better understand the role of teleconnections on Buenos Aires’ (Argentina) climate. A general increase in temperature and precipitation was observed. Temperature has increased by about 1.8°C and precipitation has increased by about 300 mm in the past century and a half. Indices of Arctic Oscillation (AO), Pacific North American (PNA), Antarctic Oscillation (AAO), and El Nino-Southern Oscillation (ENSO) are evaluated to study their effects on wheat and corn production and export. AO and PNA show strong relationships with precipitation and temperature received. AAO and ENSO show strong negative correlations with precipitation patterns and weak correlations with temperature. Sunspot Number shows a positive correlation with temperature. ENSO phases are strongly linked with the wheat and corn production and export;during El Nino Buenos Aires tends to experience extremely wet summer weather, causing soggy fields and extremely dry summer weather during La Nina causing drought. Both of these conditions result in reducing wheat and corn production and export.
