The Experts below are selected from a list of 30306 Experts worldwide ranked by ideXlab platform
Bruce T. Anderson - One of the best experts on this subject based on the ideXlab platform.
-
tropical pacific Sea surface temperatures and preceding Sea Level Pressure anomalies in the subtropical north pacific
Journal of Geophysical Research, 2003Co-Authors: Bruce T. AndersonAbstract:[1] The correspondence of Sea-surface temperature (SST) anomalies to changes in antecedent large-scale Sea Level Pressure anomalies is investigated using reanalysis data. By statistically examining linearly coupled precursor Sea Level Pressure fields and subsequent SST fields for different lag periods, it is possible to isolate a precursor mode of Sea Level Pressure (SLP) variability in the central subtropical North Pacific that precedes variations in the January–March El Nino/Southern Oscillation (ENSO) by approximately 12–15 months. A Sea Level Pressure index, which captures the important characteristics of this precursor mode of variability, is developed and evaluated. It is shown that both analyzed and observed versions of the index are significantly correlated with the January–March ENSO one year later. The SLP index is then used to examine the evolution of the surface circulation and temperature structures leading up to mature ENSO events. Initially, the January–March subtropical North Pacific SLP anomalies are associated with changes in the intensity of the subtropical trade wind regime over the North Pacific, as well as with SST anomalies over the eastern equatorial Pacific and subtropical central Pacific. In agreement with the correlation statistics associated with the SLP and lagged NINO3.4 indices, both the Sea Level Pressure field and the SST field subsequently develop ENSO-like structures over the course of the following year. Significant discussion of these results and pertinent areas of future reSearch are provided within the broader context of the ENSO system.
-
Tropical Pacific Sea‐surface temperatures and preceding Sea Level Pressure anomalies in the subtropical North Pacific
Journal of Geophysical Research, 2003Co-Authors: Bruce T. AndersonAbstract:[1] The correspondence of Sea-surface temperature (SST) anomalies to changes in antecedent large-scale Sea Level Pressure anomalies is investigated using reanalysis data. By statistically examining linearly coupled precursor Sea Level Pressure fields and subsequent SST fields for different lag periods, it is possible to isolate a precursor mode of Sea Level Pressure (SLP) variability in the central subtropical North Pacific that precedes variations in the January–March El Nino/Southern Oscillation (ENSO) by approximately 12–15 months. A Sea Level Pressure index, which captures the important characteristics of this precursor mode of variability, is developed and evaluated. It is shown that both analyzed and observed versions of the index are significantly correlated with the January–March ENSO one year later. The SLP index is then used to examine the evolution of the surface circulation and temperature structures leading up to mature ENSO events. Initially, the January–March subtropical North Pacific SLP anomalies are associated with changes in the intensity of the subtropical trade wind regime over the North Pacific, as well as with SST anomalies over the eastern equatorial Pacific and subtropical central Pacific. In agreement with the correlation statistics associated with the SLP and lagged NINO3.4 indices, both the Sea Level Pressure field and the SST field subsequently develop ENSO-like structures over the course of the following year. Significant discussion of these results and pertinent areas of future reSearch are provided within the broader context of the ENSO system.
Philip Jones - One of the best experts on this subject based on the ideXlab platform.
-
Southern hemisphere Sea‐Level Pressure data: An analysis and reconstructions back to 1951 and 1911
International Journal of Climatology, 2007Co-Authors: Philip JonesAbstract:The reliability of Australian (1972-1985) and NOTOS (1951-1962) gridded monthly mean Sea-Level Pressure data sets over the Southern Hemisphere (15-60"s) is examined by comparison with station mean Sea-Level Pressure data from 77 sites. The station data are used in a principal components regression scheme to reconstruct gridded data back to 1951 and to 1911 using different sets of station data. The reconstructions are best near the continental areas but useful reconstructions are possible near the many ocean islands that have data since 1951. The reconstructions that extend back to 191 1 are only useful near the continental areas and over the south-westem Pacific Ocean. The reconstructions are used to compare the Australian, NOTOS data sets and a New Zealand gridded set available for the Southern Hemisphere (60°E-15O0W) since 1954, and to assess changes in the strength of the three subtropical anticyclones and the southern westerlies since 1951.
-
Intercomparison of four different Southern Hemisphere Sea Level Pressure datasets
Geophysical Research Letters, 2007Co-Authors: Philip Jones, David ListerAbstract:Abstract Two different Sea-Level Pressure datasets for the strip between 20° and 40°S are intercompared. At large space-time scales the sets are virtually identical. However, for studies of short-term, regional changes caution must be exercised because the datasets may differ substantially.
-
Daily Mean Sea Level Pressure Reconstructions for the European–North Atlantic Region for the Period 1850–2003
Journal of Climate, 2006Co-Authors: T J Ansell, Rob Allan, Philip Jones, David Lister, Manola Brunet, Anders Moberg, Jucundus Jacobeit, Philip Brohan, David Parker, Nick RaynerAbstract:Abstract The development of a daily historical European–North Atlantic mean Sea Level Pressure dataset (EMSLP) for 1850–2003 on a 5° latitude by longitude grid is described. This product was produced using 86 continental and island stations distributed over the region 25°–70°N, 70°W–50°E blended with marine data from the International Comprehensive Ocean–Atmosphere Data Set (ICOADS). The EMSLP fields for 1850–80 are based purely on the land station data and ship observations. From 1881, the blended land and marine fields are combined with already available daily Northern Hemisphere fields. Complete coverage is obtained by employing reduced space optimal interpolation. Squared correlations (r 2) indicate that EMSLP generally captures 80%–90% of daily variability represented in an existing historical mean Sea Level Pressure product and over 90% in modern 40-yr European Centre for Medium-Range Weather Forecasts Re-Analyses (ERA-40) over most of the region. A lack of sufficient observations over Greenland and...
-
Intercomparison of two different southern hemisphere Sea Level Pressure datasets
Journal of Climate, 1992Co-Authors: Tim P. Barnett, Philip JonesAbstract:Two different Sea-Level Pressure datasets for the strip between 20 o and 40 o S are intercompared. At large space-time scales the sets are virtually identical. However, for studies of short-term, regional changes caution must be exercised because the datasets may differ substantially
John A Knaff - One of the best experts on this subject based on the ideXlab platform.
-
implications of summertime Sea Level Pressure anomalies in the tropical atlantic region
Journal of Climate, 1997Co-Authors: John A KnaffAbstract:Abstract This study explores the inverse relationship between Sea Level Pressure and tropical cyclones in the tropical Atlantic (TA). Upper-air observations, the National Centers for Environmental Prediction (formerly the National Meteorological Center)/National Center for Atmospheric ReSearch (NCEP/NCAR) reanalysis, and regional SSTs provide clues as to the physics of this relationship using composite and regression methods. Stratification of upper-air data by Sea Level Pressure anomalies in the TA yields several interesting results, including anomalously high (low) Pressure association with relatively dry (moist) middle Levels, cooler (warmer) midLevel temperatures, and stronger (weaker) 200–850-mb vertical wind shears. The configuration of these composite wind differences suggests that higher summertime Pressure in the TA is associated with an anomalously strong tropical upper tropospheric trough (TUTT) circulation. The observations show systematic association between the composite moisture, temperatur...
-
implications of summertime Sea Level Pressure anomalies in the tropical atlantic region
Journal of Climate, 1997Co-Authors: John A KnaffAbstract:This study explores the inverse relationship between Sea Level Pressure and tropical cyclones in the tropical Atlantic (TA). Upper-air observations, the National Centers for Environmental Prediction (formerly the National Meteorological Center)/National Center for Atmospheric ReSearch (NCEP/NCAR) reanalysis, and regional SSTs provide clues as to the physics of this relationship using composite and regression methods. Stratification of upper-air data by Sea Level Pressure anomalies in the TA yields several interesting results, including anomalously high (low) Pressure association with relatively dry (moist) middle Levels, cooler (warmer) midLevel temperatures, and stronger (weaker) 200‐850-mb vertical wind shears. The configuration of these composite wind differences suggests that higher summertime Pressure in the TA is associated with an anomalously strong tropical upper tropospheric trough (TUTT) circulation. The observations show systematic association between the composite moisture, temperature, and wind differences. Studies of longwave sensitivity using a two stream model show that the moisture field dominates the longwave radiative cooling; hence, dry midLevels enhance cooling of the atmosphere. The effects of SST variations and tropical cyclones on TA Pressure anomalies suggest that summertime Pressure in this region is strongly influenced by additional (unresolved) climate forcings. These findings lead to a hypothesis that explains both the persistent nature of the summertime Pressure (in the TA) as well as how variations of this Pressure modulate the TUTT circulation strength. The hypothesis states that positive feedbacks operate between Pressure/subsidence variations, midLevel moisture, and differential longwave radiative cooling that affects local baroclinicity (i.e., TUTT). When Pressures are anomalously high, subsidence is greater and middle Levels are dryer, resulting in increased atmospheric cooling to space and increased baroclinicity. Hence, Pressure-related variations of both the midLevel moisture field and the TUTT circulation result in modulations of the upper-Level winds and vertical wind shears in the TA. These, in turn, are found to be the primary cause of the observed Pressure‐tropical cyclone relationship; higher tropical Atlantic Pressure results in an environment that is dryer and more sheared and, thus, less favorable for tropical cyclone formation and development.
T J Ansell - One of the best experts on this subject based on the ideXlab platform.
-
daily mean Sea Level Pressure reconstructions for the european north atlantic region for the period 1850 2003
Journal of Climate, 2006Co-Authors: T J Ansell, Rob Allan, David Lister, D E Parker, P D Jones, Manola Brunet, Anders Moberg, Jucundus Jacobeit, Philip Brohan, N A RaynerAbstract:Abstract The development of a daily historical European–North Atlantic mean Sea Level Pressure dataset (EMSLP) for 1850–2003 on a 5° latitude by longitude grid is described. This product was produced using 86 continental and island stations distributed over the region 25°–70°N, 70°W–50°E blended with marine data from the International Comprehensive Ocean–Atmosphere Data Set (ICOADS). The EMSLP fields for 1850–80 are based purely on the land station data and ship observations. From 1881, the blended land and marine fields are combined with already available daily Northern Hemisphere fields. Complete coverage is obtained by employing reduced space optimal interpolation. Squared correlations (r 2) indicate that EMSLP generally captures 80%–90% of daily variability represented in an existing historical mean Sea Level Pressure product and over 90% in modern 40-yr European Centre for Medium-Range Weather Forecasts Re-Analyses (ERA-40) over most of the region. A lack of sufficient observations over Greenland and...
-
Daily Mean Sea Level Pressure Reconstructions for the European–North Atlantic Region for the Period 1850–2003
Journal of Climate, 2006Co-Authors: T J Ansell, Rob Allan, Philip Jones, David Lister, Manola Brunet, Anders Moberg, Jucundus Jacobeit, Philip Brohan, David Parker, Nick RaynerAbstract:Abstract The development of a daily historical European–North Atlantic mean Sea Level Pressure dataset (EMSLP) for 1850–2003 on a 5° latitude by longitude grid is described. This product was produced using 86 continental and island stations distributed over the region 25°–70°N, 70°W–50°E blended with marine data from the International Comprehensive Ocean–Atmosphere Data Set (ICOADS). The EMSLP fields for 1850–80 are based purely on the land station data and ship observations. From 1881, the blended land and marine fields are combined with already available daily Northern Hemisphere fields. Complete coverage is obtained by employing reduced space optimal interpolation. Squared correlations (r 2) indicate that EMSLP generally captures 80%–90% of daily variability represented in an existing historical mean Sea Level Pressure product and over 90% in modern 40-yr European Centre for Medium-Range Weather Forecasts Re-Analyses (ERA-40) over most of the region. A lack of sufficient observations over Greenland and...
-
Detection of external influence on Sea Level Pressure with a multi‐model ensemble
Geophysical Research Letters, 2005Co-Authors: Nathan P Gillett, Rob Allan, T J AnsellAbstract:[1] Over the past fifty years, December–February mean Sea Level Pressure has decreased markedly over both poles, corresponding to a trend toward strengthened westerlies in both hemispheres. In this study we compare observed Sea Level Pressure trends with those simulated in response to natural and anthropogenic influence in a suite of eight up-to-date coupled general circulation models. A global analysis indicates that Sea Level Pressure trends may be attributed to external influence. However, while simulated Southern Hemisphere Sea Level Pressure trends are consistent with those observed, simulated Northern Hemisphere Sea Level Pressure trends are not: Observations show a large negative trend in the Arctic and a positive trend over the subtropical North Atlantic and Mediterranean which is not reproduced in the simulations.
-
detection of external influence on Sea Level Pressure with a multi model ensemble
Geophysical Research Letters, 2005Co-Authors: Nathan P Gillett, Rob Allan, T J AnsellAbstract:[1] Over the past fifty years, December–February mean Sea Level Pressure has decreased markedly over both poles, corresponding to a trend toward strengthened westerlies in both hemispheres. In this study we compare observed Sea Level Pressure trends with those simulated in response to natural and anthropogenic influence in a suite of eight up-to-date coupled general circulation models. A global analysis indicates that Sea Level Pressure trends may be attributed to external influence. However, while simulated Southern Hemisphere Sea Level Pressure trends are consistent with those observed, simulated Northern Hemisphere Sea Level Pressure trends are not: Observations show a large negative trend in the Arctic and a positive trend over the subtropical North Atlantic and Mediterranean which is not reproduced in the simulations.
Antonio D. Nobre - One of the best experts on this subject based on the ideXlab platform.
-
Comments on “The Tropospheric Land–Sea Warming Contrast as the Driver of Tropical Sea Level Pressure Changes”
Journal of Climate, 2015Co-Authors: Anastassia M. Makarieva, Victor G. Gorshkov, Andrei V. Nefiodov, Douglas Sheil, Antonio D. NobreAbstract:AbstractIn their paper “The tropospheric land–Sea warming contrast as the driver of tropical Sea Level Pressure changes,” Bayr and Dommenget proposed a simple model of temperature-driven air redistribution to quantify the ratio between changes of Sea Level Pressure ps and mean tropospheric temperature Ta in the tropics. This model assumes that the height of the tropical troposphere is isobaric. Here problems with this model are identified. A revised relationship between ps and Ta is derived governed by two parameters—the isobaric and isothermal heights—rather than just one. Further insight is provided by the earlier model of Lindzen and Nigam, which was the first to use the concept of isobaric height to relate tropical ps to air temperature, and they did this by assuming that isobaric height is always around 3 km and isothermal height is likewise near constant. Observational data, presented here, show that neither of these heights is spatially universal nor does their mean values match previous assumption...
-
CORRESPONDENCE Comments on ''The Tropospheric Land-Sea Warming Contrast as the Driver of Tropical Sea Level Pressure Changes''
2015Co-Authors: Anastassia M. Makarieva, Victor G. Gorshkov, Andrei V. Nefiodov, Douglas Sheil, Konstantinov Petersburg, Antonio D. NobreAbstract:In their paper ‘‘The tropospheric land‐Sea warming contrast as the driver of tropical Sea Level Pressure changes,’’ Bayr and Dommenget proposed a simple model of temperature-driven air redistribution to quantify the ratio between changes of Sea Level Pressurepsand mean tropospheric temperatureTain the tropics. This model assumes that theheightofthetropicaltroposphereisisobaric.Hereproblemswiththismodelareidentified.Arevisedrelationship between ps and Ta is derived governed by two parameters—the isobaric and isothermal heights—rather than just one. Further insight is provided by the earlier model of Lindzen and Nigam, which was thefirst to use the concept of isobaric height to relate tropical ps to air temperature, and they did this by assuming that isobaric height is always around 3km and isothermal height is likewise near constant. Observational data, presented here, show that neither of these heights is spatially universal nor does their mean values match previous assumptions. Analyses showthat the ratioofthelong-termchangesinpsandTaassociatedwithland‐Seatemperaturecontrastsina warmingclimate—the focus of Bayr and Dommenget’s work—is in fact determined by the corresponding ratio of spatial differences in the annual mean psand Ta. The latter ratio, reflecting lower Pressure at higher temperature, is significantly impacted bythemeridionalPressureandtemperaturedifferences.Considerationsofisobaricheightsareshown to beunable to predict eitherspatialortemporal variation inps.AsnotedbyBayrandDommenget,theroleofmoisturedynamicsin generating Sea Level Pressure variation remains in need of further theoretical investigations.
