The role of latent heating in atmospheric blocking dynamics: a global climatology

Steinfeld, Daniel; Pfahl, Stephan

doi:10.1007/s00382-019-04919-6

Cited by 91 publications

(210 citation statements)

References 103 publications

Supporting

Mentioning

160

Contrasting

Order By: Relevance

“…Overall, the diabatic heating is a more rapid process compared to the diabatic cooling (not shown). Therefore, the heating branch can be interpreted as a strongly cross-isentropic branch transporting low-PV air from the lower to the upper troposphere, whereas the cooling branch is a quasi-adiabatic process that advects low-PV air towards the upper-tropospheric anticyclone, in line with the analysis of Pfahl et al (2015) and Steinfeld and Pfahl (2019) for blocks.…”

Section: Two Diabatic Regimessupporting

confidence: 62%

“…The latter excludes starting points in the stratosphere, similar to Steinfeld and Pfahl (2019). Physical parameters traced along 100 the trajectories include temperature and potential temperature.…”

Section: Backward Trajectories 95mentioning

confidence: 99%

“…If the magnitude of diabatic cooling and heating are equal, the trajectory will be sorted in the cooling branch. This approach is similar to Steinfeld and Pfahl (2019), but differs in the categorisation of the diabatic heating and cooling branches. Figure 2 shows an example for a three-day period: the backward trajectory in Fig.…”

Section: Backward Trajectories 95mentioning

confidence: 99%

See 2 more Smart Citations

A Lagrangian analysis of upper-tropospheric anticyclones associated with heat waves in Europe

Zschenderlein¹,

Wernli²,

Fink³

2020

Preprint

Self Cite

View full text Add to dashboard Cite

<p><strong>Abstract.</strong> This study presents a Lagrangian analysis of upper-tropospheric anticyclones that are connected to surface heat waves in different European regions for the period 1979 to 2016. In order to elucidate the formation of these anticyclones and the role of diabatic processes, we trace air parcels backwards from the upper-tropospheric anticyclones and quantify the diabatic heating in these air parcels. Around 25&#8211;45&#8201;% of the air parcels are diabatically heated during the last three days prior to their arrival in the upper-tropospheric anticyclones and this amount increases to 35&#8211;50&#8201;% for the last seven days. The influence of diabatic heating is larger for heat wave-related anticyclones in northern Europe and western Russia and smaller in southern Europe. Interestingly, the diabatic heating occurs in two geographically separated air streams. Three days prior to arrival, one heating branch (western branch) is located above the western North Atlantic and the other heating branch (eastern branch) is located to the southwest of the target upper-tropospheric anticyclone. The diabatic heating in the western branch is related to warm conveyor belts in North Atlantic cyclones upstream of the evolving upper-level ridge. In contrast, the eastern branch is diabatically heated by convection, as indicated by elevated mixed-layer convective available potential energy along the western side of the matured upper-level ridge. Most European regions are influenced by both branches, whereas western Russia is predominantly affected by the eastern branch. The western branch predominantly affects the formation of the upper-tropospheric anticyclone, and therefore of the heat wave, whereas the eastern branch is more active during its maintenance. For long-lasting heat waves, the western branch regenerates. The results from this study show that the dynamical processes leading to heat waves may be sensitive to small-scale microphysical and convective processes, whose accurate representation in models is thus supposed to be crucial for heat wave predictions on weather and climate time scales.</p>

show abstract

Section: Two Diabatic Regimessupporting

confidence: 62%

Section: Backward Trajectories 95mentioning

confidence: 99%

Section: Backward Trajectories 95mentioning

confidence: 99%

See 1 more Smart Citation

A Lagrangian analysis of upper-tropospheric anticyclones associated with heat waves in Europe

Zschenderlein¹,

Wernli²,

Fink³

2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…Extratropical cyclones force the geopotential height rises in developing blocks through thermal and vorticity advection (Colucci, ; Nakamura and Wallace, ), and the repeated transfer of low‐PV air polewards and upwards within cyclones into blocking ridges can act to maintain them against dissipation (Shutts, ; Yamazaki and Itoh, ; Luo et al ., ). Diabatically heated air masses can contribute considerably (>50%) to the total mass of blocked regions in the Northern Hemisphere (Pfahl et al ., ) and diabatic heating is typically strong during the onset of blocking (Steinfeld and Pfahl, ). Atmospheric blocks are notoriously difficult to forecast in NWP models (e.g., Tibaldi and Molteni, ; Pelly and Hoskins, ; Matsueda, ) and are the cause of some of the worst forecasts produced at operational NWP centres (Rodwell et al ., ; Lillo and Parsons, ).…”

Section: Introductionmentioning

confidence: 99%

“…These questions are motivated by relatively new results showing that the dynamics and predictability of upper‐tropospheric Rossby waves and atmospheric blocking events are influenced strongly by diabatic processes within extratropical cyclones (Pfahl et al ., ; Steinfeld and Pfahl, ), especially those active in their WCBs (Grams and Archambault, ; Martínez‐Alvarado et al ., ; Grams et al . ).…”

Section: Introductionmentioning

confidence: 99%

Impact of model upgrades on diabatic processes in extratropical cyclones and downstream forecast evolution

Maddison

Gray

Martínez‐Alvarado

et al. 2020

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

Models are continuously developed at numerical weather prediction (NWP) centres to improve forecast skill, with new operational model configurations adopted every few years. The parametrizations of diabatic processes are probably the most frequently updated part of NWP models as they are crucial for accurate weather predictions and contain uncertainties in their formulation. The impact of model developments is assessed here in forecasts from the Met Office's weather forecast model initialised throughout the North Atlantic Waveguide and Downstream Impact Experiment field campaign period in autumn 2016. Planned model parametrization developments are considered, together with an 'inexpensive coupled' forecast with daily updating of the sea surface temperature and sea-ice fraction. Forecasts produced from the coupled system have, on average, indistinguishable skill from the control forecasts, suggesting the benefits of coupled atmosphere-ocean NWP systems can be small. In contrast, a reduction in forecast error (∼4%) is identified in forecasts produced using an upgraded convection scheme. Periods of low forecast skill during the study period are shown to be associated with the onset and decay of blocking events and increased diabatic heating of air masses reaching the upper troposphere. In forecasts of a specific block development case that was not accurately predicted in any of the experiments or in the operational ensemble forecast from the Met Office, the representation of diabatic heating in the warm conveyor belt of an upstream cyclone is shown to moderate the subsequent block development; forecasts in which the heating is stronger generally have a more-amplified blocking ridge and amplified heating contributions from all parametrizations as diagnosed using diabatic tracers. Hence, we demonstrate that plausible changes to the representation of several different diabatic processes in models can impact forecast block development via changes within upstream cyclones. K E Y W O R D Satmospheric blocking, numerical weather prediction, parametrized diabatic processes, warm conveyor belts This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.

show abstract

Quantifying the link between heavy precipitation and Northern Hemisphere blocking—A Lagrangian analysis

Lenggenhager

Martius

2020

Atmospheric Science Letters

View full text Add to dashboard Cite

Atmospheric blocks strongly influence surface weather, including extremes such as heat waves and cold spells. Recently, diabatic heating and associated uppertropospheric potential vorticity (PV) modification have been identified as important modulators of atmospheric blocking dynamics. Also, robust links between atmospheric blocks and proximate heavy precipitation events have been established. This leads to the question of the extent to which diabatic heating associated with heavy precipitation events influences Northern Hemisphere blocking. This study uses 5 years of 3-day back trajectories started from objectively identified blocks in the ERA-Interim dataset to investigate this relationship. A substantial fraction of air parcels in blocks pass through heavy precipitation areas. The exact fraction depends on the choice of heavy precipitation threshold. Roughly 19% of all the trajectories in a block pass a heavy precipitation area (>95th percentile) area while being saturated. Of the air parcels in a block that are heated at least 5 K, 60% pass a heavy precipitation area while saturated. This fraction varies with the season and geographical area. The overall fraction is lowest in summer and highest in winter, higher over oceans than over land, and higher over the Pacific than over the Atlantic. In summer, heating is relevant over the continents and heating over North America influences blocks over the eastern Atlantic. For summer blocks in the North Atlantic and over Scandinavia, heating happens partly over the European continent.

show abstract

The role of latent heating in atmospheric blocking dynamics: a global climatology

Cited by 91 publications

References 103 publications

A Lagrangian analysis of upper-tropospheric anticyclones associated with heat waves in Europe

A Lagrangian analysis of upper-tropospheric anticyclones associated with heat waves in Europe

Impact of model upgrades on diabatic processes in extratropical cyclones and downstream forecast evolution

Quantifying the link between heavy precipitation and Northern Hemisphere blocking—A Lagrangian analysis

Contact Info

Product

Resources

About