scholarly journals Influence of Early Winter Upward Wave Activity Flux on Midwinter Circulation in the Stratosphere and Troposphere

2004 ◽  
Vol 17 (22) ◽  
pp. 4443-4452 ◽  
Author(s):  
Alexei Karpetchko ◽  
Grigory Nikulin
Keyword(s):  
Heat Flux ◽  
Reanalysis Data ◽  
Wave Activity ◽  
Heat Fluxes ◽  
Early Winter ◽  
Polar Night ◽  
Wave Refraction ◽  
Eddy Heat Flux ◽  
Wave Flux

Abstract Using NCEP–NCAR reanalysis data the authors show that the November–December averaged stratospheric eddy heat flux is strongly anticorrelated with the January–February averaged eddy heat flux in the midlatitude stratosphere and troposphere. This finding further emphasizes differences between early and midwinter stratospheric wave flux behavior, which has recently been found in long-term variations. Analysis suggests that the intraseasonal anticorrelation of stratospheric heat fluxes results from changes in the upward wave propagation in the troposphere. Stronger (weaker) upward wave fluxes in early winter lead to weaker (stronger) upward wave fluxes from the troposphere during midwinter. Also, enhanced equatorward wave refraction during midwinter (due to the stronger polar night jet) is associated with weak heat flux in the early winter. It is suggested that the effect of enhanced midwinter upward wave flux from the troposphere in the years with weak early winter heat flux overcompensates the effect of increased equatorward wave refraction in midwinter, leading to a net increase of midwinter upward wave fluxes into the stratosphere.

scholarly journals Variability and trends in dynamical forcing of tropical lower stratospheric temperatures

2014 ◽  
Vol 14 (24) ◽  
pp. 13439-13453 ◽  
Author(s):  
S. Fueglistaler ◽  
M. Abalos ◽  
T. J. Flannaghan ◽  
P. Lin ◽  
W. J. Randel
Keyword(s):  
Heat Flux ◽  
Time Series ◽  
Reanalysis Data ◽  
Heat Fluxes ◽  
Momentum Balance ◽  
Latitude Belt ◽  
Eddy Heat Flux ◽  
Temperature Trends ◽  
Highly Correlated ◽  
Additional Support

Abstract. The contribution of dynamical forcing to variations and trends in tropical lower stratospheric 70 hPa temperature for the period 1980–2011 is estimated based on ERA-Interim and Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis data. The dynamical forcing is estimated from the tropical mean residual upwelling calculated with the momentum balance equation, and with a simple proxy based on eddy heat fluxes averaged between 25° and 75° in both hemispheres. The thermodynamic energy equation with Newtonian cooling is used to relate the dynamical forcing to temperature. The deseasonalised, monthly mean time series of all four calculations are highly correlated (~ 0.85) with temperature for the period 1995–2011 when variations in radiatively active tracers are small. All four calculations provide additional support to previously noted prominent aspects of the temperature evolution 1980–2011: an anomalously strong dynamical cooling (~ −1 to −2 K) following the Pinatubo eruption that partially offsets the warming from enhanced aerosol, and a few years of enhanced dynamical cooling (~ −0.4 K) after October 2000 that contributes to the prominent drop in water entering the stratosphere at that time. The time series of dynamically forced temperature calculated with the same method are more highly correlated and have more similar trends than those from the same reanalysis but with different methods. For 1980–2011 (without volcanic periods), the eddy heat flux calculations give a dynamical cooling of ~ −0.1 to ~ −0.25 K decade−1 (magnitude sensitive to latitude belt considered and reanalysis), largely due to increasing high latitude eddy heat flux trends in September and December–January. The eddy heat flux trends also explain the seasonality of temperature trends very well, with maximum cooling in January–February. Trends derived from momentum balance calculations show near-zero annual mean dynamical cooling, with weaker seasonal trends especially in December–January. These contradictory results arising from uncertainties in data and methods are discussed and put in context to previous analyses.

scholarly journals Influence of Northern Hemispheric Winter Warming on the Pacific Storm Track

2021 ◽  
Author(s):  
Hyung-Ju Park ◽  
Kwang-Yul Kim
Keyword(s):  
Heat Flux ◽  
Global Warming ◽  
Energy Conversion ◽  
Storm Track ◽  
The Arctic ◽  
Late Winter ◽  
Turbulent Heat ◽  
Early Winter ◽  
Eddy Heat Flux ◽  
Northern Hemispheric

AbstractEffect of global warming on the sub-seasonal variability of the Northern Hemispheric winter (NDJFM) Pacific storm-track (PST) activity has been investigated. Previous studies showed that the winter-averaged PST has shifted northward and intensified, which was explained in terms of energy exchange with the mean field. Effect of global warming exhibits spatio-temporal heterogeneity with predominance over the Arctic region and in the winter season. Therefore, seasonal averaging may hide important features on sub-seasonal scales. In this study, distinct sub-seasonal response in storm track activities to winter Northern Hemispheric warming is analyzed applying cyclostationary empirical orthogonal function analysis to ERA5 data. The key findings are as follows. Change in the PST is not uniform throughout the winter; the PST shifts northward in early winter (NDJ) and intensifies in late winter (FM). In early winter, the combined effect of weakened baroclinic process to the south of the climatological PST and weakened barotropic damping to the north is responsible for the northward shift. In late winter, both processes contribute to the amplification of the PST. Further, change in baroclinic energy conversion is quantitatively dominated by eddy heat flux, whereas axial tilting of eddies is primarily responsible for change in barotropic energy conversion. A close relationship between anomalous eddy heat flux and anomalous boundary heating, which is largely determined by surface turbulent heat flux, is also demonstrated.

Combustor Wall Surface Temperature and Heat Flux Measurement Using a Fiber-Coupled Long Wave Infrared Hyperspectral Sensor

2021 ◽  
Author(s):  
Aravind Chandh ◽  
Oleksandr Bibik ◽  
Subodh Adhikari ◽  
David Wu ◽  
Tim Lieuwen ◽  
...  
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Flux Measurement ◽  
Heat Fluxes ◽  
Long Wavelength ◽  
Combustion Gases ◽  
Acoustic Perturbation ◽  
Accuracy And Precision ◽  
Long Wavelength Infrared

Abstract In this paper, we discuss the development of a non-intrusive surface temperature sensor based on long-wavelength infrared (LWIR) hyperspectral technology. The LWIR detection enables to minimize optical interferences from hot combustion gases (emission mostly within UV-MWIR region). Utilization of hyperspectral detection allows to further improve temperature measurement accuracy and precision. The developed sensor with fiber coupling provides the required flexibility to be maneuvered around/through combustor hardware. The LWIR fiber probe is fully protected by the custom-designed water-cooled probe housing. This device is designed to sustain temperature of 2400 K at pressure of 50 bar, which enables long-term optical diagnostics inside the practical high-pressure combustion facilities where extreme thermal acoustic perturbation and intense heat fluxes are present. The housing featured a diamond window to selectively measure spectra in the LWIR region to get accurate surface temperature exclusively of the combustor wall. The probe was installed into a RQL style combustor to get surface temperature of both hot and cold side of the combustor wall. Further, pointwise heat flux estimates across the combustion liner wall was derived using the temperature measurements.

scholarly journals Total ozone trends and variability during 1979–2012 from merged datasets of various satellites

2013 ◽  
Vol 13 (11) ◽  
pp. 30407-30452 ◽  
Author(s):  
W. Chehade ◽  
J. P. Burrows ◽  
M. Weber
Keyword(s):  
Heat Flux ◽  
Solar Cycle ◽  
Trend Analysis ◽  
Total Ozone ◽  
Montreal Protocol ◽  
The Other ◽  
The Arctic ◽  
Eddy Heat Flux ◽  
Other Hand

Abstract. The study presents a~long term statistical trend analysis of total ozone datasets obtained from various satellites. A multi-variate linear regression was applied to annual mean zonal mean data using various natural and anthropogenic explanatory variables that represent dynamical and chemical processes which modify global ozone distributions in a changing climate. The study investigated the magnitude and zonal distribution of the different atmospheric chemical and dynamical factors to long-term total ozone changes. The regression model included the equivalent effective stratospheric chlorine (EESC), the 11 yr solar cycle, the Quasi-Biennial Oscillation (QBO), stratospheric aerosol loading describing the effects from major volcanic eruptions, the El Niño/Southern Oscillation (ENSO), the Arctic and Antarctic Oscillation (AO/AAO), and accumulated eddy heat flux (EHF), the latter representing changes due to the Brewer–Dobson circulation. The total ozone column dataset used here comprises the SBUV/TOMS/OMI merged data (1979–2012) MOD V8.0, the SBUV/SBUV-2 merged V8.6 and the merged GOME/SCIAMACHY/GOME-2 (GSG) WFDOAS merged data (1995–2012). The trend analysis was performed for twenty six 5° wide latitude bands from 65° S to 65° N, the analysis explained most of the ozone variability. The results show that QBO dominates the ozone variability in the tropics (±7 DU) while at higher latitudes, the dynamical indices, AO/AAO and eddy heat flux, have substantial influence on total ozone variations by up to ±10 DU. Volcanic aerosols are only prominent during the eruption periods and these together with the ENSO signal are more evident in the Northern Hemisphere. The signature of the solar cycle is evident over all latitudes and contributes about 10 DU from solar maximum to solar minimum. EESC is found to be a main contributor to the long-term ozone decline and the trend changes after the end of 1990s. A positive significant trend in total ozone columns is found after 1997 (between 1 and 8.2 DU decade−1) which points at the slowing of ozone decline and the onset of ozone recovery. The EESC based trends are compared with the trends obtained from the statistical piecewise linear trend (PWLT or hockey stick) model with a turnaround in 1997 to examine the differences between both approaches. Similar and significant pre-turnaround trends are observed. On the other hand, our results do indicate that the positive PWLT turnaround trends are larger than indicated by the EESC trends, however, they agree within 2-sigma, thus demonstrating the success of the Montreal Protocol phasing out of the ozone depleting substances (ODS). A sensitivity study is carried out by comparing the regression results, using SBUV MOD 8.0 merged time series (1979–2012) and a merged dataset combining TOMS/SBUV (1979–June 1995) and GOME/SCIAMACHY/GOME-2 ("GSG") WFDOAS (Weighting Function DOAS) (July 1995–2012) as well as SBUV/SBUV-2 MOD 8.6 (1979–2012) in the regression analysis in order to investigate the uncertainty in the long-term trends due to different ozone datasets and data versions. Replacing the late SBUV merged data record with GSG data (unscaled and adjusted) leads to very similar results demonstrating the high consistency between satellite datasets. However, the comparison of the new SBUV merged Mod V8.6 with the V8.0 data showed somewhat smaller sensitivities with regard to several proxies, however, the EESC and PWLT trends are very similar. On the other hand, the new MOD 8.6 data in the PWLT model revealed a~reduced ODS related upward trend after 1997.

scholarly journals Thermal Regime of Ice Covered Swedish Lakes

1996 ◽  
Vol 27 (1-2) ◽  
pp. 39-56 ◽  
Author(s):  
Lars Bengtsson ◽  
Thorbjörn Svensson
Keyword(s):  
Heat Flux ◽  
Solar Radiation ◽  
Heat Source ◽  
Lake Water ◽  
Heat Budget ◽  
Heat Content ◽  
Heat Fluxes ◽  
Late Winter ◽  
Temperature Profiles ◽  
Early Winter

Temperature conditions and heat fluxes in ice covered lakes are discussed analyzing measurements in eight Swedish lakes. Heat fluxes from sediments and heat fluxes from water to ice are determined from temperature profiles. The contribution of solar radiation is estimated from heat-budget calculations. It is found that the heat content of most of the lakes changes very little when they are ice covered, but that the lake-water temperature slightly increases. All heat fluxes are small. The heat flux from the sediments is the highest flux in early winter, but is later in the winter balanced by the heat loss from the water to the underside of the ice. Solar radiation is an important heat source in late winter, when the snow cover is thin.

scholarly journals The relationship between tropospheric wave forcing and tropical lower stratospheric water vapor

2008 ◽  
Vol 8 (3) ◽  
pp. 471-480 ◽  
Author(s):  
S. Dhomse ◽  
M. Weber ◽  
J. Burrows
Keyword(s):  
Heat Flux ◽  
Water Vapor ◽  
Satellite Data ◽  
Planetary Wave ◽  
Wave Activity ◽  
Stratospheric Water Vapor ◽  
Average Decrease ◽  
Eddy Heat Flux ◽  
Sudden Decrease ◽  
Cold Point

Abstract. Using water vapor data from HALOE and SAGE II, an anti-correlation between planetary wave driving (here expressed by the mid-latitude eddy heat flux at 50 hPa added from both hemispheres) and tropical lower stratospheric (TLS) water vapor has been obtained. This appears to be a manifestation of the inter-annual variability of the Brewer-Dobson (BD) circulation strength (the driving of which is generally measured in terms of the mid-latitude eddy heat flux), and hence amount of water vapor entering the stratosphere. Some years such as 1991 and 1997 show, however, a clear departure from the anti-correlation which suggests that the water vapor changes in TLS can not be attributed solely to changes in extratropical planetary wave activity (and its effect on the BD circulation). After 2000 a sudden decrease in lower stratospheric water vapor has been reported in earlier studies based upon satellite data from HALOE, SAGE II and POAM III indicating that the lower stratosphere has become drier since then. This is consistent with a sudden rise in the combined mid-latitude eddy heat flux with nearly equal contribution from both hemispheres as shown here and with the increase in tropical upwelling and decrease in cold point temperatures found by Randel et al. (2006). The low water vapor and enhanced planetary wave activity (in turn strength of the BD circulation) has persisted until the end of the satellite data records. From a multi-variate regression analysis applied to 27 years of NCEP and HadAT2 (radiosonde) temperatures (up to 2005) with contributions from solar cycle, stratospheric aerosols and QBO removed, the enhancement wave driving after 2000 is estimated to contribute up to 0.7 K cooling to the overall TLS temperature change during the period 2001–2005 when compared to the period 1996–2000. NCEP cold point temperature show an average decrease of nearly 0.4 K from changes in the wave driving, which is consistent with observed mean TLS water vapor changes of about −0.2 ppm after 2000.

scholarly journals Estimates of Eddy Heat Flux Crossing the Antarctic Circumpolar Current from Observations in Drake Passage

2016 ◽  
Vol 46 (7) ◽  
pp. 2103-2122 ◽  
Author(s):  
D. Randolph Watts ◽  
Karen L. Tracey ◽  
Kathleen A. Donohue ◽  
Teresa K. Chereskin
Keyword(s):  
Heat Flux ◽  
Heat Transport ◽  
Antarctic Circumpolar Current ◽  
Baroclinic Instability ◽  
Drake Passage ◽  
Heat Fluxes ◽  
Poleward Heat Transport ◽  
Eddy Heat Flux ◽  
Circumpolar Current ◽  
The Antarctic

AbstractThe 4-yr measurements by current- and pressure-recording inverted echo sounders in Drake Passage produced statistically stable eddy heat flux estimates. Horizontal currents in the Antarctic Circumpolar Current (ACC) turn with depth when a depth-independent geostrophic current crosses the upper baroclinic zone. The dynamically important divergent component of eddy heat flux is calculated. Whereas full eddy heat fluxes differ greatly in magnitude and direction at neighboring locations within the local dynamics array (LDA), the divergent eddy heat fluxes are poleward almost everywhere. Case studies illustrate baroclinic instability events that cause meanders to grow rapidly. In the southern passage, where eddy variability is weak, heat fluxes are weak and not statistically significant. Vertical profiles of heat flux are surface intensified with ~50% above 1000 m and uniformly distributed with depth below. Summing poleward transient eddy heat transport across the LDA of −0.010 ± 0.005 PW with the stationary meander contribution of −0.004 ± 0.001 PW yields −0.013 ± 0.005 PW. A comparison metric, −0.4 PW, represents the total oceanic heat loss to the atmosphere south of 60°S. Summed along the circumpolar ACC path, if the LDA heat flux occurred at six “hot spots” spanning similar or longer path segments, this could account for 20%–70% of the metric, that is, up to −0.28 PW. The balance of ocean poleward heat transport along the remaining ACC path should come from weak eddy heat fluxes plus mean cross-front temperature transports. Alternatively, the metric −0.4 PW, having large uncertainty, may be high.

scholarly journals Variability and trends in dynamical forcing of tropical lower stratospheric temperatures

2014 ◽  
Vol 14 (9) ◽  
pp. 13381-13412 ◽  
Author(s):  
S. Fueglistaler ◽  
M. Abalos ◽  
T. J. Flannaghan ◽  
P. Lin ◽  
W. J. Randel
Keyword(s):  
Heat Flux ◽  
Time Series ◽  
Heat Fluxes ◽  
Momentum Balance ◽  
Dynamical Response ◽  
Temporal Shift ◽  
Radiative Balance ◽  
Residual Time ◽  
Eddy Heat Flux ◽  
Maximum Warming

Abstract. We analyse the relation between tropical lower stratospheric temperatures and dynamical forcing over the period 1980–2011 using NCEP, MERRA and ERA-Interim reanalyses. The tropical mean thermodynamic energy equation with Newtonian cooling for radiation is forced with two dynamical predictors: (i) the average eddy heat flux of both hemispheres; and (ii) tropical upwelling estimated from momentum balance following Randel et al. (2002). The correlation (1995–2011) for deseasonalised tropical average temperatures at 70 hPa with the eddy heat flux based predictor is 0.84 for ERA-Interim (0.77 for the momentum balance calculation), and 0.87 for MERRA. The eddy heat flux based predictor indicates a dynamically forced cooling of the tropics of ∼−0.1 K decade−1 (∼−0.2 K decade−1 excluding volcanic periods) for the period 1980–2011 in MERRA and ERA-Interim. ERA-Interim eddy heat fluxes drift slightly relative to MERRA in the 2000's, possibly due to onset of GPS temperature data assimilation. While NCEP gives a small warming trend, all 3 reanalyses show a similar seasonality, with strongest cooling in January/February (∼−0.4 K decade−1, from northern hemispheric forcing) and October (∼−0.3 K decade−1, from southern hemispheric forcing). Months preceding and following the peaks in cooling trends show pronounced smaller, or even warming, trends. Consequently, the seasonality in the trends arises in part due to a temporal shift in eddy activity. Over all months, the Southern Hemisphere contributes more to the tropical cooling in both MERRA and ERA-Interim. The residual time series (observed minus estimate of dynamically forced temperature) are well correlated between ERA-Interim and MERRA, with differences largely due to temperature differences. The residual time series is dominated by the modification of the radiative balance by volcanic aerosol following the eruption of El Chichon (maximum warming of ∼3 K at 70 hPa) and Pinatubo (maximum warming of ∼4 K at 70 hPa), with a strong dynamical response during Pinatubo partially masking the aerosol heating.

The role of diabatic heating in Ferrel cell dynamics

2021 ◽  
Author(s):  
Orli Lachmy ◽  
Yohai Kaspi
Keyword(s):  
Heat Flux ◽  
Heating Rate ◽  
Diabatic Heating ◽  
Heat Budget ◽  
Reanalysis Data ◽  
Cell Dynamics ◽  
Data Set ◽  
Eddy Heat Flux ◽  
Ferrel Cell ◽  
Meridional Winds

<p>The Ferrel cell consists of the zonal mean vertical and meridional winds in the midlatitudes. The continuity of the Ferrel circulation and the zonal mean momentum and heat budgets imply a collocation of the eddy-driven jet and poleward eddy heat flux maxima, under certain assumptions, including the negligibility of diabatic heating. The latter assumption is questioned, since midlatitude storms are associated with latent heating in the midtroposphere. In this study, the heat budget of the Ferrel cell in both hemispheres is examined, using the JRA55 reanalysis data set. The diabatic heating rate is significant close to the center of the Ferrel cell during winter and at the ascending branch during summer in both hemispheres. The interannual variability shows a positive correlation between the diabatic heating rate in the midlatitude midtroposphere and the latitudinal separation between the eddy heat flux and the eddy-driven jet maxima during winter in both hemispheres.</p>

Estimating Eddy Heat Flux from Float Data in the North Atlantic: The Impact of Temporal Sampling Interval

2007 ◽  
Vol 24 (5) ◽  
pp. 923-934 ◽  
Author(s):  
Brian S. Chinn ◽  
Sarah T. Gille
Keyword(s):  
Heat Flux ◽  
North Atlantic ◽  
Sampling Interval ◽  
Heat Fluxes ◽  
Temporal Sampling ◽  
The North ◽  
Eddy Heat Flux ◽  
Daily Sampling ◽  
The North Atlantic ◽  
The Impact

Abstract Acoustically tracked float data from 16 experiments carried out in the North Atlantic are used to evaluate the feasibility of estimating eddy heat fluxes from floats. Daily float observations were bin averaged in 2° by 2° by 200-db-deep geographic bins, and eddy heat fluxes were estimated for each bin. Results suggest that eddy heat fluxes can be highly variable, with substantial outliers that mean that fluxes do not converge quickly. If 100 statistically independent observations are available in each bin (corresponding to 500–1000 float days of data), then results predict that 80% of bins will have eddy heat fluxes that are statistically different from zero. Pop-up floats, such as Autonomous Lagrangian Circulation Explorer (ALACE) and Argo floats, do not provide daily sampling and therefore underestimate eddy heat flux. The fraction of eddy heat flux resolved using pop-up float sampling patterns decreases linearly with increasing intervals between float mapping and can be modeled analytically. This implies that flux estimates from pop-up floats may be correctable to represent true eddy heat flux.

Sign in / Sign up

Export Citation Format

Share Document