scholarly journals Physical Process Contributions to the Development of a Super Explosive Cyclone Over the Gulf Stream

2021 ◽  
Vol 9 ◽  
Author(s):  
Shuqin Zhang ◽  
Chunlei Liu ◽  
Jianjun Xu ◽  
Shaojing Zhang ◽  
Ruoying Tang ◽  
...  
Keyword(s):  
Gulf Stream ◽  
Diabatic Heating ◽  
Rapid Development ◽  
Cyclonic Vorticity ◽  
Upper Troposphere ◽  
Explosive Cyclone ◽  
Weather Forecasts ◽  
Vorticity Advection ◽  
Medium Range ◽  
Water Vapor Convergence

Contributions of different physical processes to the development of a super explosive cyclone (SEC) migrating over the Gulf Stream with the maximum deepening rate of 3.45 Bergeron were investigated using the ERA5 atmospheric reanalysis from European Centre for Medium-Range Weather Forecasts (ECMWF). The evolution of the SEC resembled the Shapiro-Keyser model. The moisture transported to the bent-back front by easterlies from Gulf Stream favored precipitation and enhanced the latent heat release. The bent-back front and warm front were dominated by the water vapor convergence in the mid-low troposphere, the cyclonic-vorticity advection in the mid-upper troposphere and the divergence in the upper troposphere. These factors favored the rapid development of the SEC, but their contributions showed significant differences during the explosive-developing stage. The diagnostic results based on the Zwack-Okossi equation suggested that the early explosive development of the SEC was mainly forced by the diabatic heating in the mid-low troposphere. From the early explosive-developing moment to maximum-deepening-rate moment, the diabatic heating, warm-air advection and cyclonic-vorticity advection were all enhanced significantly, their combination forced the most explosive development, and the diabatic heating had the biggest contribution, followed by the warm-air advection and cyclonic-vorticity advection, which is different from the previous studies of ECs over the Northwestern Atlantic. The cross section of these factors suggested that during the rapid development, the cyclonic-vorticity advection was distributed and enhanced significantly in the mid-low troposphere, the warm-air advection was strengthened significantly in the mid-low and upper troposphere, and the diabatic heating was distributed in the middle troposphere.

scholarly journals The stratospheric Brewer–Dobson circulation inferred from age of air in the ERA5 reanalysis

2021 ◽  
Author(s):  
Felix Ploeger ◽  
Mohamadou Diallo ◽  
Edward Charlesworth ◽  
Paul Konopka ◽  
Bernard Legras ◽  
...  
Keyword(s):  
Diabatic Heating ◽  
Climate Models ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Residual Circulation ◽  
Heating Rates ◽  
Weather Forecasts ◽  
Trend Pattern ◽  
Transit Times ◽  
Medium Range

Abstract. This paper investigates the global stratospheric Brewer–Dobson circulation (BDC) in the ERA5 meteorological reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF). The analysis is based on simulations of stratospheric mean age of air, including the full age spectrum, with the Lagrangian transport model CLaMS, driven by winds and total diabatic heating rates from the reanalysis. ERA5-based results are compared to those of the preceding ERA–Interim reanalysis. Our results show a significantly slower BDC for ERA5 than for ERA–Interim, manifesting in weaker diabatic heating rates and larger age of air. In the tropical lower stratosphere, heating rates are 30–40 % weaker in ERA5, likely correcting a known bias in ERA–Interim. Above, ERA5 age of air appears slightly high-biased and the BDC slightly slow compared to tracer observations. The age trend in ERA5 over 1989–2018 is negative throughout the stratosphere, as climate models predict in response to global warming. However, the age decrease is not linear over the period but exhibits steplike changes which could be caused by muti-annual variability or changes in the assimilation system. Over the 2002–2012 period, ERA5 age shows a similar hemispheric dipole trend pattern as ERA–Interim, with age increasing in the NH and decreasing in the SH. Shifts in the age spectrum peak and residual circulation transit times indicate that reanalysis differences in age are likely caused by differences in the residual circulation. In particular, the shallow BDC branch accelerates similarly in both reanalyses while the deep branch accelerates in ERA5 and decelerates in ERA–Interim.

Dynamical Forcing of Subseasonal Variability in the Tropical Brewer–Dobson Circulation

2014 ◽  
Vol 71 (9) ◽  
pp. 3439-3453 ◽  
Author(s):  
Marta Abalos ◽  
William J. Randel ◽  
Encarna Serrano
Keyword(s):  
Lower Stratosphere ◽  
Momentum Balance ◽  
Strongly Correlated ◽  
Temperature Changes ◽  
Upper Troposphere ◽  
Weather Forecasts ◽  
Wave Forcing ◽  
Tropical Tropopause ◽  
Subseasonal Variability ◽  
Medium Range

Abstract Upwelling across the tropical tropopause exhibits strong subseasonal variability superimposed on the well-known annual cycle, and these variations directly affect temperature and tracers in the tropical lower stratosphere. In this work, the dynamical forcing of tropical upwelling on subseasonal time scales is investigated using the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) for 1979–2011. Momentum balance diagnostics reveal that transience in lower-stratospheric upwelling is linked to the effects of extratropical wave forcing, with centers of action in the extratropical winter stratosphere and in the subtropical upper troposphere of both hemispheres. The time-dependent forcing in these regions induces a remote coupled response in the zonal mean wind and the meridional circulation (with associated temperature changes), which drives upwelling variability in the tropical stratosphere. This behavior is observed in the reanalysis, consistent with theory. Dynamical patterns reflect distinctive forcing of the shallow versus deep branches of the Brewer–Dobson circulation; the shallow branch is most strongly correlated with wave forcing in the subtropical upper troposphere and lower stratosphere, while the deep branch is mainly influenced by high-latitude planetary waves.

scholarly journals The stratospheric Brewer-Dobson circulation inferred from age of air in the ERA5 reanalysis

2021 ◽  
Author(s):  
Felix Ploeger ◽  
Mohamadou Diallo ◽  
Edward Charlesworth ◽  
Paul Konopka ◽  
Bernard Legras ◽  
...  
Keyword(s):  
Diabatic Heating ◽  
Climate Models ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Residual Circulation ◽  
Heating Rates ◽  
Weather Forecasts ◽  
Trend Pattern ◽  
Transit Times ◽  
Medium Range

<p>This paper investigates the global stratospheric Brewer-Dobson circulation (BDC) in the ERA5 meteorological reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF). The analysis is based on simulations of stratospheric mean age of air, including the full age spectrum, with the Lagrangian transport model CLaMS, driven by winds and total diabatic heating rates from the reanalysis. ERA5-based results are compared to those of the preceding ERA-Interim reanalysis. Our results show a significantly slower BDC for ERA5 than for ERA-Interim, manifesting in weaker diabatic heating rates and larger age of air. In the tropical lower stratosphere, heating rates are 30-40% weaker in ERA5, likely correcting a known bias in ERA-Interim. Above, ERA5 age of air appears slightly high-biased and the BDC slightly slow compared to tracer observations. The age trend in ERA5 over 1989-2018 is negative throughout the stratosphere, as climate models predict in response to global warming. However, the age decrease is not linear over the period but exhibits steplike changes which could be caused by muti-annual variability or changes in the assimilation system. Over the 2002-2012 period, ERA5 age shows a similar hemispheric dipole trend pattern as ERA-Interim, with age increasing in the NH and decreasing in the SH. Shifts in the age spectrum peak and residual circulation transit times indicate that reanalysis differences in age are likely caused by differences in the residual circulation. In particular, the shallow BDC branch accelerates similarly in both reanalyses while the deep branch accelerates in ERA5 and decelerates in ERA-Interim.</p>

Intensification of Hurricane Sandy (2012) through Extratropical Warm Core Seclusion

2013 ◽  
Vol 141 (12) ◽  
pp. 4296-4321 ◽  
Author(s):  
Thomas J. Galarneau ◽  
Christopher A. Davis ◽  
Melvyn A. Shapiro
Keyword(s):  
New Jersey ◽  
Rhode Island ◽  
North Atlantic ◽  
Gulf Stream ◽  
Diabatic Heating ◽  
Hurricane Sandy ◽  
Cyclonic Vorticity ◽  
Near Surface ◽  
Warm Core ◽  
Upper Level

Abstract Hurricane Sandy's landfall along the New Jersey shoreline at 2330 UTC 29 October 2012 produced a catastrophic storm surge stretching from New Jersey to Rhode Island that contributed to damage in excess of $50 billion—the sixth costliest U.S. tropical cyclone on record since 1900—and directly caused 72 fatalities. Hurricane Sandy's life cycle was marked by two upper-level trough interactions while it moved northward over the western North Atlantic on 26–29 October. During the second trough interaction on 29 October, Sandy turned northwestward and intensified as cold continental air encircled the warm core vortex and Sandy acquired characteristics of a warm seclusion. The aim of this study is to determine the dynamical processes that contributed to Sandy's secondary peak in intensity during its warm seclusion phase using high-resolution numerical simulations. The modeling results show that intensification occurred in response to shallow low-level convergence below 850 hPa that was consistent with the Sawyer–Eliassen solution for the secondary circulation that accompanied the increased baroclinicity in the radial direction. Additionally, cyclonic vertical vorticity generated by tilting of horizontal vorticity along an axis of frontogenesis northwest of Sandy was axisymmetrized. The axis of frontogenesis was anchored to the Gulf Stream in a region of near-surface differential diabatic heating. The unusual northwestward track of Sandy allowed the cyclonic vorticity over the Gulf Stream to form ahead of the main vortex and be readily axisymmetrized. The underlying dynamics driving intensification were nontropical in origin, and supported the reclassification of Sandy as extratropical prior to landfall.

scholarly journals MIPAS reduced spectral resolution UTLS-1 mode measurements of temperature, O<sub>3</sub>, HNO<sub>3</sub>, N<sub>2</sub>O, H<sub>2</sub>O and relative humidity over ice: retrievals and comparison to MLS

2009 ◽  
Vol 2 (1) ◽  
pp. 439-487 ◽  
Author(s):  
S. Chauhan ◽  
M. Höpfner ◽  
G. P. Stiller ◽  
T. von Clarmann ◽  
B. Funke ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Pressure Range ◽  
Michelson Interferometer ◽  
Analysis Data ◽  
Height Range ◽  
Upper Troposphere ◽  
Weather Forecasts ◽  
Mixing Ratios ◽  
Medium Range ◽  
The Tropics

Abstract. During several periods since 2005 the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat has performed observations dedicated to the region of the upper troposphere/lower stratosphere (UTLS). For the duration of November/December 2005 global distributions of temperature and several trace gases from MIPAS UTLS-1 mode measurements have been retrieved using the IMK/IAA (Institut für Meteorologie und Klimaforschung/Instituto de Astrofísica de Andalucía) scientific processor. In the UTLS region a vertical resolution of 2.5 to 3 km has been achieved. The retrieved temperature, H2O, O3, HNO3, N2O, and relative humidity over ice are intercompared with the Microwave Limb Sounder (MLS/Aura) v2.2 data. In general, MIPAS and MLS temperatures agree within ±4 K over the whole pressure range of 316–0.68 hPa. Systematic, latitude-independent differences of −2 to −4 K (MIPAS-MLS) at 121 hPa are explained by previously observed biases in the MLS v2.2 temperature retrievals. Temperature differences of −4 K up to 12 K above 10.0 hPa are present similarly in MIPAS and MLS with respect to ECMWF (European Centre for Medium-Range Weather Forecasts) and are likely due to deficiencies of the ECMWF analysis data. MIPAS and MLS stratospheric volume mixing ratios (vmr) of H2O agree within ±1 ppmv, with indication of oscillations between 146 and 26 hPa in the MLS dataset. Tropical upper tropospheric values of relative humidity over ice measured by the two instruments differ by ±20% in the pressure range ~146 to 68 hPa. These differences are mainly caused by the MLS temperature biases. Ozone mixing ratios agree within 0.5 ppmv (10 to 20%) between 68 and 14 hPa. At pressures smaller than 10 hPa, MIPAS O3 vmr are higher than MLS by an average of 0.5 ppmv (10%). General agreement between MIPAS and MLS HNO3 is within the range of −1.0 (−10%) to 1.0 ppbv (20%). MIPAS HNO3 is 1.0 ppbv (10%) higher compared to MLS in the height range of 46 to 10 hPa over the Northern Hemisphere. Over the tropics at 31.6 hPa MLS shows a low bias of more than 1 ppbv (>50%). In general, MIPAS and MLS N2O vmr agree within 20 to 40 ppbv (20 to 40%). Differences in the height range between 100 to 21 hPa are attributed to a known 20% positive bias in MIPAS N2O data.

An Assessment of ECMWF and NCEP–NCAR Reanalyses in the Southern Hemisphere at the End of the Presatellite Era: Results from the EOLE Experiment (1971–72)

2006 ◽  
Vol 134 (11) ◽  
pp. 3367-3383 ◽  
Author(s):  
Albert Hertzog ◽  
Claude Basdevant ◽  
François Vial
Keyword(s):  
Southern Hemisphere ◽  
Storm Track ◽  
Upper Troposphere ◽  
Weather Forecasts ◽  
Subtropical Jet ◽  
Observation Network ◽  
Medium Range ◽  
Standard Deviations ◽  
Environmental Prediction

Abstract This article estimates the biases and standard deviations of the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and the 50-yr National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) Reanalysis (NN50) in the upper troposphere and lower stratosphere in 1971–72. These estimates are obtained by comparing the reanalyzed temperatures and winds with EOLE observations, a dataset collected during 480 superpressure-ballon flights in the Southern Hemisphere (SH). Dedicated algorithms have been developped to control the quality of this dataset and a stringent selection has been performed on the observations. None of the atmospheric centers has assimilated the EOLE dataset, which is therefore fully independent from the reanalyses. It is furthermore argued that the statistics obtained in this study at the end of the presatellite era may be representative of the reanalysis accuracy since 1957. The results of these comparisons indicate that NN50 tends to be a few degrees colder than the observations in the SH subpolar latitudes, while ERA-40 is less hit by this cold-pole issue. Both reanalyses, on the other hand, are found to be warmer than the observations by about 1 K in the subtropics. In contrast, the wind comparisons only exhibit nonsignificant or small reanalysis biases, even though the reanalyzed subtropical jet is slightly displaced equatorward with respect to the observations. The ability of reanalyses to capture the atmospheric synoptic-scale variability in the upper troposphere is assessed by computing the standard deviations of the reanalysis minus observation differences. The ERA-40 and NN50 standard deviations show a maximum (i.e., a poorer reanalysis accuracy) in the SH storm track. However, ERA-40 standard deviations are found to be much larger than NN50 standard deviations. The standard deviations also exhibit a marked decrease above the continents, stressing the heterogeneity of the atmospheric observation network during the presatellite era. Finally, in contrast with previous studies, the reanalysis accuracy does not appear to be better during summer than during winter.

scholarly journals Predictability of the Strong Ural blocking Event in January 2012 in the Subseasonal to Seasonal Models of Europe and Canada

Atmosphere ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 538
Author(s):  
Dong Chen ◽  
Shaobo Qiao ◽  
Shankai Tang ◽  
Ho Nam Cheung ◽  
Jieyu Liu ◽  
...  
Keyword(s):  
Climate Change ◽  
East Asia ◽  
Development Stage ◽  
Weather Forecasts ◽  
Vorticity Advection ◽  
Medium Range ◽  
Ecmwf Model ◽  
Temperature Tendency ◽  
Blocking Event ◽  
Vorticity Tendency

The occurrence of a Ural blocking (UB) event is an important precursor of severe cold air outbreaks in Siberia and East Asia, and thus is significant to accurately predict UB events. Using subseasonal to seasonal (S2S) models of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Environment and Climate Change Canada (ECCC), we evaluated the predictability of a persistent UB event on 18 to 26 January 2012. Results showed that the ECCC model was superior to the ECMWF model in predicting the development stage of the UB event ten days in advance, while the ECMWF model had better predictions than the ECCC model for more than ten days in advance and the decaying stage of the UB event. By comparing the dynamic and thermodynamic evolution of the UB event predicted by the two models via the geostrophic vorticity tendency equation and temperature tendency equation, we found that the ECCC model better predicted the vertical vorticity advection, ageostrophic vorticity tendency, the tilting effect, horizontal temperature advection, and adiabatic heating during the development stage, whereas the ECMWF model better predicted the three dynamic and the two thermodynamic terms during the decaying stage. In addition, during both the development and decaying stages, the two models were good (bad) at predicting the vortex stretching term (horizontal vorticity advection), with the PCC between both the predictions and the observations larger (smaller) than +0.70 (+0.10) Thus, we suggest that the prediction of the persistent UB event in the S2S model might be improved by the better prediction of the horizontal vorticity advection.

scholarly journals The stratospheric Brewer–Dobson circulation inferred from age of air in the ERA5 reanalysis

2021 ◽  
Vol 21 (11) ◽  
pp. 8393-8412
Author(s):  
Felix Ploeger ◽  
Mohamadou Diallo ◽  
Edward Charlesworth ◽  
Paul Konopka ◽  
Bernard Legras ◽  
...  
Keyword(s):  
Diabatic Heating ◽  
Climate Models ◽  
Transport Model ◽  
Lagrangian Model ◽  
Residual Circulation ◽  
Heating Rates ◽  
Uncertainty Range ◽  
Weather Forecasts ◽  
Transit Times ◽  
Medium Range

Abstract. This paper investigates the global stratospheric Brewer–Dobson circulation (BDC) in the ERA5 meteorological reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF). The analysis is based on simulations of stratospheric mean age of air, including the full age spectrum, with the Lagrangian transport model CLaMS (Chemical Lagrangian Model of the Stratosphere), driven by reanalysis winds and total diabatic heating rates. ERA5-based results are compared to results based on the preceding ERA-Interim reanalysis. Our results show a significantly slower BDC for ERA5 than for ERA-Interim, manifesting in weaker diabatic heating rates and higher age of air. In the tropical lower stratosphere, heating rates are 30 %–40 % weaker in ERA5, likely correcting a bias in ERA-Interim. At 20 km and in the Northern Hemisphere (NH) stratosphere, ERA5 age values are around the upper margin of the uncertainty range from historical tracer observations, indicating a somewhat slow–biased BDC. The age trend in ERA5 over the 1989–2018 period is negative throughout the stratosphere, as climate models predict in response to global warming. However, the age decrease is not linear but steplike, potentially caused by multi-annual variability or changes in the observations included in the assimilation. During the 2002–2012 period, the ERA5 age shows a similar hemispheric dipole trend pattern as ERA-Interim, with age increasing in the NH and decreasing in the Southern Hemisphere (SH). Shifts in the age spectrum peak and residual circulation transit times indicate that reanalysis differences in age are likely caused by differences in the residual circulation. In particular, the shallow BDC branch accelerates in both reanalyses, whereas the deep branch accelerates in ERA5 and decelerates in ERA-Interim.

scholarly journals MIPAS reduced spectral resolution UTLS-1 mode measurements of temperature, O<sub>3</sub>, HNO<sub>3</sub>, N<sub>2</sub>O, H<sub>2</sub>O and relative humidity over ice: retrievals and comparison to MLS

2009 ◽  
Vol 2 (2) ◽  
pp. 337-353 ◽  
Author(s):  
S. Chauhan ◽  
M. Höpfner ◽  
G. P. Stiller ◽  
T. von Clarmann ◽  
B. Funke ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Pressure Range ◽  
Michelson Interferometer ◽  
Analysis Data ◽  
Upper Troposphere ◽  
Weather Forecasts ◽  
Latitude Range ◽  
Mixing Ratios ◽  
Medium Range ◽  
The Tropics

Abstract. During several periods since 2005 the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat has performed observations dedicated to the region of the upper troposphere/lower stratosphere (UTLS). For the duration of November/December 2005 global distributions of temperature and several trace gases from MIPAS UTLS-1 mode measurements have been retrieved using the IMK/IAA (Institut für Meteorologie und Klimaforschung/Instituto de Astrofísica de Andalucía) scientific processor. In the UTLS region a vertical resolution of 3 km for temperaure, 3 to 4 km for H2O, 2.5 to 3 km for O3, 3.5 km for HNO3 and 3.5 to 2.5 km for N2O has been achieved. The retrieved temperature, H2O, O3, HNO3, N2O, and relative humidity over ice are intercompared with the Microwave Limb Sounder (MLS/Aura) v2.2 data in the pressure range 316 to 0.68 hPa, 316 to 0.68 hPa, 215 to 0.68 hPa, 215 to 3.16 hPa, 100 to 1 hPa and 316 to 10 hPa, respectively. In general, MIPAS and MLS temperatures are biased within ±4 K over the whole pressure and latitude range. Systematic, latitude-independent differences of −2 to −4 K (MIPAS-MLS) at 121 hPa are explained by previously observed biases in the MLS v2.2 temperature retrievals. Temperature differences of −4 K up to 12 K above 10.0 hPa are present both in MIPAS and MLS with respect to ECMWF (European Centre for Medium-Range Weather Forecasts) and are likely due to deficiencies of the ECMWF analysis data. MIPAS and MLS stratospheric volume mixing ratios (vmr) of H2O are biased within ±1 ppmv, with indication of oscillations between 146 and 26 hPa in the MLS dataset. Tropical upper tropospheric values of relative humidity over ice measured by the two instruments differ by ±20% in the pressure range ~146 to 68 hPa. These differences are mainly caused by the MLS temperature biases. Ozone mixing ratios agree within 0.5 ppmv (10 to 20%) between 68 and 14 hPa. At pressures smaller than 10 hPa, MIPAS O3 vmr are higher than MLS by an average of 0.5 ppmv (10%). General agreement between MIPAS and MLS HNO3 is within the range of −1.0 (−10%) to 1.0 ppbv (20%). MIPAS HNO3 is 1.0 ppbv (10%) higher compared to MLS between 46 hPa and 10 hPa over the Northern Hemisphere. Over the tropics at 31.6 hPa MLS shows a low bias of more than 1 ppbv (>50%). In general, MIPAS and MLS N2O vmr agree within 20 to 40 ppbv (20 to 40%). Differences in the range between 100 to 21 hPa are attributed to a known 20% positive bias in MIPAS N2O data.

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