scholarly journals Assessing the impact of sea surface temperatures on a simulated medicane using ensemble simulations

2019 ◽  
Vol 19 (4) ◽  
pp. 941-955 ◽  
Author(s):  
Robin Noyelle ◽  
Uwe Ulbrich ◽  
Nico Becker ◽  
Edmund P. Meredith
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
Western Mediterranean ◽  
Sea Surface ◽  
Tyrrhenian Sea ◽  
Sea Surface Temperatures ◽  
Surface Temperatures ◽  
Western Mediterranean Basin ◽  
A Minor ◽  
The Impact

Abstract. The sensitivity of the October 1996 Medicane in the western Mediterranean basin to sea surface temperatures (SSTs) is investigated with a regional climate model via ensemble sensitivity simulations. For 11 SST states, ranging from −4 K below to +6 K above the observed SST field (in 1 K steps), 24-member ensembles of the medicane are simulated. By using a modified phase space diagram and a simple compositing method, it is shown that the SST state has a minor influence on the tracks of the cyclones but a strong influence on their intensities. Increased SSTs lead to greater probabilities of tropical transitions, to stronger lower- and upper-level warm cores and to lower pressure minima. The tropical transition occurs sooner and lasts longer, which enables a greater number of transitioning cyclones to survive landfall over Sardinia and re-intensify in the Tyrrhenian Sea. The results demonstrate that SSTs influence the intensity of fluxes from the sea, which leads to greater convective activity before the storms reach their maturity. These results suggest that the processes at steady state for medicanes are very similar to tropical cyclones.

scholarly journals Assessing the impact of SSTs on a simulated medicane using ensemble simulations

2018 ◽  
Author(s):  
Robin Noyelle ◽  
Uwe Ulbrich ◽  
Nico Becker ◽  
Edmund P. Meredith
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
Western Mediterranean ◽  
Tyrrhenian Sea ◽  
Western Mediterranean Basin ◽  
Minor Influence ◽  
Climate Model Simulations ◽  
Upper Level ◽  
A Minor ◽  
The Impact

Abstract. The sensitivity of the October 1996 medicane in the western Mediterranean basin to sea surface temperatures (SSTs) is investigated via 24-member ensembles of regional climate model simulations. Eleven ensembles are created by uniformly changing SSTs in a range of −4 K to +6 K from the observed field, with a 1 K step. By using a modified phase space diagram and a simple compositing method, it is shown that the SST state has a minor influence on the tracks of the cyclones, but a strong influence on their intensities. Increased SSTs lead to greater probabilities of tropical transitions, to stronger low- and upper-level warm cores, and to lower pressure minima. The tropical transition occurs sooner and lasts longer, which enables a greater number of transitioning cyclones to survive landfall over Sardinia and to re-intensify in the Tyrrhenian Sea. The results demonstrate that SSTs influence the intensity of fluxes from the sea, which leads to greater convective activity before the storms reach their maturity. These results suggest that the processes at steady-state for medicanes are very similar to tropical cyclones.

scholarly journals Glacial to Holocene changes in trans-Atlantic Saharan dust transport and dust-climate feedbacks

2016 ◽  
Vol 2 (11) ◽  
pp. e1600445 ◽  
Author(s):  
Ross H. Williams ◽  
David McGee ◽  
Christopher W. Kinsley ◽  
David A. Ridley ◽  
Shineng Hu ◽  
...  
Keyword(s):  
North Atlantic ◽  
Radiative Forcing ◽  
Climate Model ◽  
Regional Climate ◽  
Sea Surface ◽  
Saharan Dust ◽  
Sea Surface Temperatures ◽  
Dust Transport ◽  
Surface Temperatures ◽  
Tropical North Atlantic

Saharan mineral dust exported over the tropical North Atlantic is thought to have significant impacts on regional climate and ecosystems, but limited data exist documenting past changes in long-range dust transport. This data gap limits investigations of the role of Saharan dust in past climate change, in particular during the mid-Holocene, when climate models consistently underestimate the intensification of the West African monsoon documented by paleorecords. We present reconstructions of African dust deposition in sediments from the Bahamas and the tropical North Atlantic spanning the last 23,000 years. Both sites show early and mid-Holocene dust fluxes 40 to 50% lower than recent values and maximum dust fluxes during the deglaciation, demonstrating agreement with records from the northwest African margin. These quantitative estimates of trans-Atlantic dust transport offer important constraints on past changes in dust-related radiative and biogeochemical impacts. Using idealized climate model experiments to investigate the response to reductions in Saharan dust’s radiative forcing over the tropical North Atlantic, we find that small (0.15°C) dust-related increases in regional sea surface temperatures are sufficient to cause significant northward shifts in the Atlantic Intertropical Convergence Zone, increased precipitation in the western Sahel and Sahara, and reductions in easterly and northeasterly winds over dust source regions. Our results suggest that the amplifying feedback of dust on sea surface temperatures and regional climate may be significant and that accurate simulation of dust’s radiative effects is likely essential to improving model representations of past and future precipitation variations in North Africa.

Quantifying Teleconnection pathways leading to Low Rainfall anomalies during Boreal Summer in Indonesian Borneo

2021 ◽  
Author(s):  
Timothy Lam ◽  
Marlene Kretschmer ◽  
Samantha Adams ◽  
Alberto Arribas ◽  
Rachel Prudden ◽  
...  
Keyword(s):  
Causal Inference ◽  
Climate Model ◽  
Southern Oscillation ◽  
Sea Surface ◽  
Boreal Summer ◽  
Climate Indices ◽  
Sea Surface Temperatures ◽  
Study Region ◽  
Surface Temperatures ◽  
Rainfall Anomalies

<p>Teleconnections are sources of predictability for regional weather and climate, which can be represented by causal relationships between climate features in physically separated regions. In this study, teleconnections of low rainfall anomalies in Indonesian Borneo are analysed and quantified using causal inference theory and causal networks. Causal hypotheses are first developed based on climate model experiments in literature and then justified by means of partial regression analysis between NCEP reanalysis sea surface temperatures and climate indices (drivers) and rainfall data in Indonesian Borneo from various sources (target variable). We find that, as previous studies have highlighted, El Niño Southern Oscillation (ENSO) has a profound effect on rainfall in Indonesia Borneo, with positive Niño 3.4 index serving as a direct driver of low rainfall, also partially through reduced sea surface temperatures (SSTs) over Indonesian waters. On the other hand, while Indian Ocean Dipole (IOD) influences Indonesian Borneo rainfall through SSTs over the same area as a thermodynamic effect, its remaining effect has shifted at multidecadal timescale, opening the rooms for further research. This work informs the potential of a systematic causal approach to statistical inference as a powerful tool to verify and explore atmospheric teleconnections and enables seasonal forecasting to strengthen prevention and control of drought and fire multihazards over peatlands in the study region.</p><p>Keywords: Tropical teleconnections, Causal inference, Climate variability, Drought, Indonesia</p>

tamh tm iedor sphere -1 el 9a8 ti 0vse , lyc li s m im a p te le models. Much more detailed than in the Australian region (Simpson and Downey 1975; run. Rather they are models than simp allysofomuuscehdm ro ourte in eelxypesn in si cvee th to e V ha osicbe ee anndfoH rc uendt 198 recasting El Nino behav­ tures for the p w er iitohd4o ). bsT1eh rv e BMRC climate model iour (e.g., sea surface temperatures in the east simulated by the model ha 9s49e -d 9 1 se , aasnud rf ac th eet em ra p in efraal ­ lfeoqrueactaosrti al r Pacific), they could, in theory, be used to ob been compared with the coupling o ai fnftahleloacnedantetmoptehrea tu artemoosvpehre re la nidn . th Tehseew te asse rv ru end ra fiinvfea ll t i ( m Fr eesd , er w ik istehne th teal. s1a9m9e5 ). seTahesm ur o fa dceelmmo od deellss , ( hPoowweevrere , tis less than perfect. Improved ocean ph m er p ic e ra ctoun re d s it io bnust . s T li h ghtly different starting atmos­ these coupled mode alls . . 1995) are being developed for ialg lu rseterm ate esnttw he it h ‘ noobisseer ’ veind iffe ed rtahier ence betw nfa m ll, o w de e l . neTeoenge th t e ed to av mru uns O era cghep se aarsto ne pro onfalthperebd le ic m ti own it ihstthheeduisfef ic oufltcy oupled models in all five runs as an ‘ens coupled models has in sitmhue la attim ng osrp ai hnefrailclA of u st p ra rleicainpp it raetc io ip n i tat sihoon, w em abtls le’. eoam st e The en o ve srkin ll sem o rt ihne bl sei ave rn Amuusl rag t a ra ti lnegsgoennte he ia. (Ni ra l sp su a c ti caelsssca in le ssiimmuploartt in an gtaftomrousspeh rs e , ridcesvpairtieab th il e it iyr Fur T th h e es resoau tm th o , stphheem ri odels are less successful. sea cshuo rf l a ls ce1t9e9m6p ) e . ra M tu ordeealneoxmpaelriiemsehnatvsewailtohngspheicsitfo ie ry djtohb er e o fo f re si m pr uolbaa ti bnlgyc th cemSoOdIel ( eFx ig pe urrieme3n .3 ts ) . do ThaegSoO od I an be predicted without the need

Droughts ◽  
2016 ◽  
pp. 77-77
Keyword(s):  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Coupled Models ◽  
Coupled Mode ◽  
Australian Region ◽  
Surface Temperatures

The Transient Circulation Response to Radiative Forcings and Sea Surface Warming*

2014 ◽  
Vol 27 (24) ◽  
pp. 9323-9336 ◽  
Author(s):  
Paul W. Staten ◽  
Thomas Reichler ◽  
Jian Lu
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Indirect Response ◽  
Radiative Forcings ◽  
Surface Warming ◽  
Impact Surface ◽  
Surface Temperatures

Abstract Tropospheric circulation shifts have strong potential to impact surface climate. However, the magnitude of these shifts in a changing climate and the attending regional hydrological changes are difficult to project. Part of this difficulty arises from the lack of understanding of the physical mechanisms behind the circulation shifts themselves. To better delineate circulation shifts and their respective causes the circulation response is decomposed into 1) the “direct” response to radiative forcings themselves and 2) the “indirect” response to changing sea surface temperatures. Using ensembles of 90-day climate model simulations with immediate switch-on forcings, including perturbed greenhouse gas concentrations, stratospheric ozone concentrations, and sea surface temperatures, this paper documents the direct and indirect transient responses of the zonal-mean general circulation, and investigates the roles of previously proposed mechanisms in shifting the midlatitude jet. It is found that both the direct and indirect wind responses often begin in the lower stratosphere. Changes in midlatitude eddies are ubiquitous and synchronous with the midlatitude zonal wind response. Shifts in the critical latitude of wave absorption on either flank of the jet are not indicted as primary factors for the poleward-shifting jet, although some evidence for increasing equatorward wave reflection over the Southern Hemisphere in response to sea surface warming is seen. Mechanisms for the Northern Hemisphere jet shift are less clear.

Evolution of Water Vapor Concentrations and Stratospheric Age of Air in Coupled Chemistry-Climate Model Simulations

2007 ◽  
Vol 64 (3) ◽  
pp. 905-921 ◽  
Author(s):  
John Austin ◽  
John Wilson ◽  
Feng Li ◽  
Holger Vömel
Keyword(s):  
Water Vapor ◽  
Greenhouse Gas ◽  
Climate Model ◽  
Sea Surface ◽  
Time Slice ◽  
Sea Surface Temperatures ◽  
Model Simulations ◽  
Stratospheric Water Vapor ◽  
Surface Temperatures ◽  
Climate Model Simulations

Abstract Stratospheric water vapor concentrations and age of air are investigated in an ensemble of coupled chemistry-climate model simulations covering the period from 1960 to 2005. Observed greenhouse gas concentrations, halogen concentrations, aerosol amounts, and sea surface temperatures are all specified in the model as time-varying fields. The results are compared with two experiments (time-slice runs) with constant forcings for the years 1960 and 2000, in which the sea surface temperatures are set to the same climatological values, aerosol concentrations are fixed at background levels, while greenhouse gas and halogen concentrations are set to the values for the relevant years. The time-slice runs indicate an increase in stratospheric water vapor from 1960 to 2000 due primarily to methane oxidation. The age of air is found to be significantly less in the year 2000 run than the 1960 run. The transient runs from 1960 to 2005 indicate broadly similar results: an increase in water vapor and a decrease in age of air. However, the results do not change gradually. The age of air decreases significantly only after about 1975, corresponding to the period of ozone reduction. The age of air is related to tropical upwelling, which determines the transport of methane into the stratosphere. Oxidation of increased methane from enhanced tropical upwelling results in higher water vapor amounts. In the model simulations, the rate of increase of stratospheric water vapor during the period of enhanced upwelling is up to twice the long-term mean. The concentration of stratospheric water vapor also increases following volcanic eruptions during the simulations.

scholarly journals A Hydrodynamical Atmosphere/Ocean Coupled Modeling System for Multiple Tropical Cyclones

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 869
Author(s):  
Ghassan J. Alaka ◽  
Dmitry Sheinin ◽  
Biju Thomas ◽  
Lew Gramer ◽  
Zhan Zhang ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Sea Surface ◽  
Intensity Change ◽  
Coupling Scheme ◽  
Sea Surface Temperatures ◽  
Improvement Program ◽  
Surface Temperatures ◽  
Skill Scores ◽  
Basin Scale ◽  
The Impact

The goal of this paper is to introduce a new multi-storm atmosphere/ocean coupling scheme that was implemented and tested in the Basin-Scale Hurricane Weather Research and Forecasting (HWRF-B) model. HWRF-B, an experimental model developed at the National Oceanic and Atmospheric Administration (NOAA) and supported by the Hurricane Forecast Improvement Program, is configured with multiple storm-following nested domains to produce high-resolution predictions for several tropical cyclones (TCs) within the same forecast integration. The new coupling scheme parallelizes atmosphere/ocean interactions for each nested domain in HWRF-B, and it may be applied to any atmosphere/ocean coupled system. TC forecasts from this new hydrodynamical modeling system were produced in the North Atlantic and eastern North Pacific from 2017–2019. The performance of HWRF-B was evaluated, including forecasts of TC track, intensity, structure (e.g., surface wind radii), and intensity change, and simulated sea-surface temperatures were compared with satellite observations. Median forecast skill scores showed significant improvement over the operational HWRF at most forecast lead times for track, intensity, and structure. Sea-surface temperatures cooled by 1–8 °C for the five HWRF-B case studies, demonstrating the utility of the model to study the impact of the ocean on TC intensity forecasting. These results show the value of a multi-storm modeling system and provide confidence that the multi-storm coupling scheme was implemented correctly. Future TC models within NOAA, especially the Unified Forecast System’s Hurricane Analysis and Forecast System, would benefit from the multi-storm coupling scheme whose utility and performance are demonstrated in HWRF-B here.

Sign in / Sign up

Export Citation Format

Share Document