Impact of the current feedback on the representation of tropical cyclones in coupled models

2020 ◽  
Author(s):  
Lisa Maillard ◽  
Julien Boucharel ◽  
Lionel Renault ◽  
Thomas Arsouze
Keyword(s):  
Tropical Cyclones ◽  
Large Scale ◽  
Earth Model ◽  
Lead Times ◽  
Oceanic Circulation ◽  
Coupled Models ◽  
Current Feedback ◽  
Oceanic Current ◽  
Operational Forecasts ◽  
The Impact

<p><span>Tropical Cyclones (TCs) are among the most destructive natural phenomena on Earth and severely impact nearly a billion people. Coupled models have become a necessary tool to improve our knowledge on those natural hazards. Improving their ability to statistically represent TCs is of prior importance. In the present study, we investigate the impact of the mechanical interaction between the surface oceanic current and the atmosphere (i.e., the Current FeedBack, CFB) on the statistic of TCs in different basins. We perform sensitivity experiments using the EC-Earth model in its High-Resolution version (1/12˚), by switching on and off CFB. As CFB has been shown to strongly improve the realism of the oceanic circulation at both large scale and mesoscale, we expect an improvement, i.e., a better realism, of the statistical TCs representation when CFB is taken into account in the model. Improving coupled models will help design forecast schemes with lead times longer than those currently provided by operational forecasts centers.</span></p>

scholarly journals Assessing the impact of hydrodynamics on large-scale flood wave propagation – a case study for the Amazon Basin

2017 ◽  
Vol 21 (1) ◽  
pp. 117-132 ◽  
Author(s):  
Jannis M. Hoch ◽  
Arjen V. Haag ◽  
Arthur van Dam ◽  
Hessel C. Winsemius ◽  
Ludovicus P. H. van Beek ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Hydrodynamic Model ◽  
Large Scale ◽  
Hydrologic Model ◽  
Flood Events ◽  
Coupled Models ◽  
Validation Parameters ◽  
Directional Coupling ◽  
Inundation Extent ◽  
The Impact

Abstract. Large-scale flood events often show spatial correlation in neighbouring basins, and thus can affect adjacent basins simultaneously, as well as result in superposition of different flood peaks. Such flood events therefore need to be addressed with large-scale modelling approaches to capture these processes. Many approaches currently in place are based on either a hydrologic or a hydrodynamic model. However, the resulting lack of interaction between hydrology and hydrodynamics, for instance, by implementing groundwater infiltration on inundated floodplains, can hamper modelled inundation and discharge results where such interactions are important. In this study, the global hydrologic model PCR-GLOBWB at 30 arcmin spatial resolution was one-directionally and spatially coupled with the hydrodynamic model Delft 3D Flexible Mesh (FM) for the Amazon River basin at a grid-by-grid basis and at a daily time step. The use of a flexible unstructured mesh allows for fine-scale representation of channels and floodplains, while preserving a coarser spatial resolution for less flood-prone areas, thus not unnecessarily increasing computational costs. In addition, we assessed the difference between a 1-D channel/2-D floodplain and a 2-D schematization in Delft 3D FM. Validating modelled discharge results shows that coupling PCR-GLOBWB to a hydrodynamic routing scheme generally increases model performance compared to using a hydrodynamic or hydrologic model only for all validation parameters applied. Closer examination shows that the 1-D/2-D schematization outperforms 2-D for r2 and root mean square error (RMSE) whilst having a lower Kling–Gupta efficiency (KGE). We also found that spatial coupling has the significant advantage of a better representation of inundation at smaller streams throughout the model domain. A validation of simulated inundation extent revealed that only those set-ups incorporating 1-D channels are capable of representing inundations for reaches below the spatial resolution of the 2-D mesh. Implementing 1-D channels is therefore particularly of advantage for large-scale inundation models, as they are often built upon remotely sensed surface elevation data which often enclose a strong vertical bias, hampering downstream connectivity. Since only a one-directional coupling approach was tested, and therefore important feedback processes are not incorporated, simulated discharge and inundation extent for both coupled set-ups is generally overpredicted. Hence, it will be the subsequent step to extend it to a two-directional coupling scheme to obtain a closed feedback loop between hydrologic and hydrodynamic processes. The current findings demonstrating the potential of one-directionally and spatially coupled models to obtain improved discharge estimates form an important step towards a large-scale inundation model with a full dynamic coupling between hydrology and hydrodynamics.

The moisture budget of tropical cyclones: large scale environmental constraints and sensitivity to model horizontal resolution

2020 ◽  
Author(s):  
Benoit Vanniere ◽  
Malcolm Roberts ◽  
Pier Luigi Vidale ◽  
Kevin Hodges ◽  
Marie-Estelle Demory
Keyword(s):  
Tropical Cyclones ◽  
Large Scale ◽  
Climate Models ◽  
Potential Temperature ◽  
Large Change ◽  
Moisture Flux ◽  
Horizontal Resolution ◽  
Moisture Budget ◽  
High Resolution Models ◽  
The Impact

<p>Previous studies have shown that, the number, intensity and structure of simulated tropical cyclones (TC) in climate models get closer to the observations as the horizontal resolution is increased. However, the sensitivity of tropical cyclone precipitation and moisture budget to changes in resolution has received less attention. In this study, we use the five-model ensemble from project PRIMAVERA/HighResMIP to investigate the systematic changes associated with the water budget of tropical cyclones in a range of horizontal resolutions from 1º to 0.25º. Our results show that despite a large change in the distribution of TC intensity with resolution, the distribution of precipitation per TC does not change significantly. This result is explained by the large scale balance which characterises the moisture budget of TCs, i.e. radii of ~15º a scale that low and high resolution models represent equally well. The wind profile is found to converge between low and high resolutions for radii > 5º, resulting in a moisture flux convergence into the TC with similar magnitude at low and high resolutions. In contrast to precipitation per TC, the larger TC intensity at higher resolution is explained by the larger surface latent heat flux near the center of the storm, which leads to an increase in equivalent potential temperature and warmer core anomalies, despite representing a negligible contribution to the moisture budget. We discuss the complication arising from the choice of the tracking algorithm when assessing the impact of model resolution and the implications of such a constraint on the TC moisture budget in the context of climate change.</p>

Diurnal Variation of the Convective Area and Eye Size Associated with the Rapid Intensification of Tropical Cyclones

2020 ◽  
Vol 148 (10) ◽  
pp. 4061-4082
Author(s):  
Jae-Deok Lee ◽  
Chun-Chieh Wu ◽  
Kosuke Ito
Keyword(s):  
Diurnal Variation ◽  
Tropical Cyclones ◽  
Satellite Imagery ◽  
Large Scale ◽  
Linear Regression Analysis ◽  
Heat Content ◽  
Vertical Wind Shear ◽  
Mixed Phase ◽  
Eye Size ◽  
The Impact

AbstractThis study examines the diurnal variation of the convective area and eye size of 30 rapidly intensifying tropical cyclones (RI TCs) that occurred in the western North Pacific from 2015 to 2017 utilizing Himawari-8 satellite imagery. The convective area can be divided into the active convective area (ACA), mixed phase, and inactive convective area (IACA) based on specific thresholds of brightness temperature. In general, ACA tends to develop vigorously from late afternoon to early the next morning, while mixed phase and IACA develop during the day. This diurnal pattern indicates the potential for ACA to evolve into mixed phase or IACA over time. From the 30 samples, RI TCs tend to have at least a single-completed diurnal signal of ACA inside the radius of maximum wind (RMW) during the rapidly intensifying period. In the same period, the RMW also contracts significantly. Meanwhile, more intense storms such as those of category 4 or 5 hurricane intensity are apt to have continuous ACA inside the RMW and maintain eyewall convective clouds. These diurnal patterns of the ACA could vary depending on the impact of large-scale environments such as vertical wind shear, ocean heat content, environmental mesoscale convection, and terrain. The linear regression analysis shows that from the tropical storm stage, RI commences after a slow intensification period, which enhances both the primary circulation and eyewall convective cloud. Finally, after the eye structure appears in satellite imagery, its size changes inversely to the diurnal variation of the convective activity (e.g., the eye size becomes larger during the daytime).

scholarly journals Research Progress for Dynamic Effects of Cities on Precipitation: A Review

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1355
Author(s):  
Caijun Yue ◽  
Zhihui Han ◽  
Wen Gu ◽  
Yuqi Tang ◽  
Xiangyu Ao
Keyword(s):  
Tropical Cyclones ◽  
Large Scale ◽  
Horizontal Distribution ◽  
Research Progress ◽  
Layer By Layer ◽  
Distribution Characteristics ◽  
Dynamic Effects ◽  
Momentum Exchange ◽  
Extreme Precipitation Events ◽  
The Impact

Citization significantly changes original surface properties. City areas can cause surface winds to decrease; furthermore, ground friction can be transferred layer by layer through the momentum exchange of air movement, which affects the air layers above. Precipitation modification by city environments has been an active research area. Under the conditions of high wind speed, the dynamic effects of cities on precipitation are relatively obvious. Generally, the dynamic effects fall into two main categories: (1) for weather systems under weak forcing synoptic backgrounds, such as local convective systems, shorter-lived extreme precipitation events and fronts and city barrier effects can delay the movement of weather systems, directly change the horizontal distribution characteristics and occurrence time for precipitation, change the flow field and structure, cause the bifurcation of weather systems, and change the horizontal distribution characteristics of precipitation; (2) for weather systems under strong forcing synoptic backgrounds, such as extratropical systems (with large-scale moisture transport), monsoon systems, landfalling tropical cyclones, and supercell storms, the impact of the dynamic effects of cities cannot lead to the bifurcation of the weather system, nor can it change the horizontal distribution characteristics of the whole precipitation field, but it can have an impact on the local precipitation intensity and distribution. However, currently, people do not agree on the impact of cities on precipitation, especially regarding tropical cyclones. Hence, we provide a review and provide insights into the dynamic effects of cities on precipitation.

scholarly journals Rapid Weakening of Tropical Cyclones in Monsoon Gyres over the Tropical Western North Pacific

2018 ◽  
Vol 31 (3) ◽  
pp. 1015-1028 ◽  
Author(s):  
Jia Liang ◽  
Liguang Wu ◽  
Guojun Gu
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Vertical Wind Shear ◽  
Tropical Cyclone Intensity ◽  
Cyclone Intensity ◽  
Operational Forecasts ◽  
Tropical Western North Pacific

Abstract As one major source of forecasting errors in tropical cyclone intensity, rapid weakening of tropical cyclones [an intensity reduction of 20 kt (1 kt = 0.51 m s−1) or more over a 24-h period] over the tropical open ocean can result from the interaction between tropical cyclones and monsoon gyres. This study aims to examine rapid weakening events occurring in monsoon gyres in the tropical western North Pacific (WNP) basin during May–October 2000–14. Although less than one-third of rapid weakening events happened in the tropical WNP basin south of 25°N, more than 40% of them were associated with monsoon gyres. About 85% of rapid weakening events in monsoon gyres occurred in September and October. The rapid weakening events associated with monsoon gyres are usually observed near the center of monsoon gyres when tropical cyclone tracks make a sudden northward turn. The gyres can enlarge the outer size of tropical cyclones and tend to induce prolonged rapid weakening events with an average duration of 33.2 h. Large-scale environmental factors, including sea surface temperature changes, vertical wind shear, and midlevel environmental humidity, are not primary contributors to them, suggesting the possible effect of monsoon gyres on these rapid weakening events by modulating the tropical cyclone structure. This conclusion is conducive to improving operational forecasts of tropical cyclone intensity.

Diurnal Radiation Cycle Impact on the Pregenesis Environment of Hurricane Karl (2010)

2014 ◽  
Vol 71 (4) ◽  
pp. 1241-1259 ◽  
Author(s):  
Christopher Melhauser ◽  
Fuqing Zhang
Keyword(s):  
Tropical Cyclones ◽  
Large Scale ◽  
Environmental Stability ◽  
Shortwave Radiation ◽  
Radiative Cooling ◽  
Moist Convection ◽  
Heating And Cooling ◽  
Highly Sensitive ◽  
Deep Moist Convection ◽  
The Impact

Abstract Through convection-permitting ensemble and sensitivity experiments, this study examines the impact of the diurnal radiation cycle on the pregenesis environment of Hurricane Karl (2010). It is found that the pregenesis environmental stability and the intensity of deep moist convection can be considerably modulated by the diurnal extremes in radiation. Nighttime destabilization of the local and large-scale environment through radiative cooling may promote deep moist convection and increase the genesis potential, likely enhancing the intensity of the resultant tropical cyclones. Modified longwave and shortwave radiation experiments found tropical cyclone development to be highly sensitive to the periodic cycle of heating and cooling, with suppressed formation in the daytime-only and no-radiation experiments and quicker intensification compared with the control for nighttime-only experiments.

scholarly journals The impact of atmospheric and oceanic circulations on the Greenland Sea iceconcentration

2020 ◽  
Author(s):  
Sourav Chatterjee ◽  
Roshin P. Raj ◽  
Laurent Bertino ◽  
Sebastian H. Merlind ◽  
Nuncio Murukesh ◽  
...  
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
Ice Formation ◽  
Oceanic Circulation ◽  
Greenland Sea ◽  
Wind Stress Curl ◽  
Northerly Wind ◽  
Sea Ice Concentration ◽  
Ice Dynamics ◽  
The Impact

Abstract. The amount and spatial extent of Greenland Sea (GS) sea ice are primarily driven by the sea ice export across the Fram Strait (FS) and by local seasonal sea ice formation, melting and sea ice dynamics. Maximum sea ice concentration (SIC) variability is found in the marginal ice zone and ‘Odden’ region in the central GS. In this study, using satellite passive microwave sea ice observations, atmospheric and a coupled ocean-sea ice reanalysis system we show that both the atmospheric and oceanic circulation in the GS act in tandem to explain the SIC variability in the GS. Anomalous low/high sea level pressure (SLP) over the Nordic Seas is found to strengthen/weaken the Greenland Sea Gyre (GSG) circulation. The large-scale atmospheric circulation pattern associated with this GSG variability features North Atlantic Oscillation (NAO) like SLP pattern with its northern center of action shifted north-eastward from its canonical position. During anomalous low SLP periods, northerly wind anomalies reduce the sea ice export in the central GS due to westward Ekman drift of sea ice. This in turn decreases the freshwater content and weakens ocean stratification in the central GS. At the same time, the associated positive wind stress curl anomaly strengthens the GSG circulation which recirculates warm and saline Atlantic water (AW) into this region. Under a weakly stratified condition, the subsurface AW anomalies can reach the surface to inhibit new sea ice formation, further reducing the SIC in the central GS. Thus, this study highlights combined influence of atmospheric and oceanic circulation in the central GS SIC variability.

scholarly journals The Moisture Budget of Tropical Cyclones in HighResMIP Models: Large-Scale Environmental Balance and Sensitivity to Horizontal Resolution

2020 ◽  
Vol 33 (19) ◽  
pp. 8457-8474
Author(s):  
Benoît Vannière ◽  
Malcolm Roberts ◽  
Pier Luigi Vidale ◽  
Kevin Hodges ◽  
Marie-Estelle Demory ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Latent Heat ◽  
Large Scale ◽  
Climate Models ◽  
Potential Temperature ◽  
Large Change ◽  
Moisture Flux ◽  
Horizontal Resolution ◽  
Moisture Budget ◽  
The Impact

AbstractPrevious studies have shown that the number, intensity, and structure of simulated tropical cyclones (TCs) in climate models get closer to the observations as the horizontal resolution is increased. However, the sensitivity of tropical cyclone precipitation and moisture budget to changes in resolution has received less attention. In this study, we use the five-model ensemble from project PRIMAVERA/HighResMIP to investigate the systematic changes of the water budget of tropical cyclones in a range of horizontal resolutions from 1° to 0.25°. Our results show that, despite a large change in the distribution of TC intensity with resolution, the distribution of precipitation per TC (i.e., averaged in a 5° radial cap) does not change significantly. This result is explained by the fact that low- and high-resolution models represent equally well the large-scale balance that characterizes the moisture budget of TCs, with the radius of the moisture source extending to ~15° from the center of the TC (i.e. well beyond the TC edge). The wind profile is found to converge in the low and high resolutions for radii > 5°, resulting in a moisture flux convergence into the TC of similar magnitude at low and high resolutions. In contrast to precipitation per TC, TC intensity does increase at higher resolution and this is explained by the larger surface latent heat flux near the center of the storm, which leads to an increase in equivalent potential temperature and warmer core anomalies, although this extra latent heat represents a negligible contribution to the overall moisture budget. We discuss the complication arising from the choice of the tracking algorithm when assessing the impact of model resolution.

scholarly journals Impact of Storm Size on Prediction of Storm Track and Intensity Using the 2016 Operational GFDL Hurricane Model

2017 ◽  
Vol 32 (4) ◽  
pp. 1491-1508 ◽  
Author(s):  
Morris A. Bender ◽  
Timothy P. Marchok ◽  
Charles R. Sampson ◽  
John A. Knaff ◽  
Matthew J. Morin
Keyword(s):  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Numerical Models ◽  
Storm Track ◽  
Eastern Pacific ◽  
Lead Times ◽  
Rapid Intensification ◽  
Forecast Lead Time ◽  
The Impact

Abstract The impact of storm size on the forecast of tropical cyclone storm track and intensity is investigated using the 2016 version of the operational GFDL hurricane model. Evaluation was made for 1529 forecasts in the Atlantic, eastern Pacific, and western North Pacific basins, during the 2014 and 2015 seasons. The track and intensity errors were computed from forecasts in which the 34-kt (where 1 kt = 0.514 m s−1) wind radii obtained from the operational TC vitals that are used to initialize TCs in the GFDL model were replaced with wind radii estimates derived using an equally weighted average of six objective estimates. It was found that modifying the radius of 34-kt winds had a significant positive impact on the intensity forecasts in the 1–2 day lead times. For example, at 48 h, the intensity error was reduced 10%, 5%, and 4% in the Atlantic, eastern Pacific, and western North Pacific, respectively. The largest improvements in intensity forecasts were for those tropical cyclones undergoing rapid intensification, with a maximum error reduction in the 1–2 day forecast lead time of 14% and 17% in the eastern and western North Pacific, respectively. The large negative intensity biases in the eastern and western North Pacific were also reduced 25% and 75% in the 12–72-h forecast lead times. Although the overall impact on the average track error was neutral, forecasts of recurving storms were improved and tracks of nonrecurving storms degraded. Results also suggest that objective specification of storm size may impact intensity forecasts in other high-resolution numerical models, particularly for tropical cyclones entering a rapid intensification phase.

scholarly journals The impact of precipitation evaporation on the atmospheric aerosol distribution in EC-Earth v3.2.0

2018 ◽  
Vol 11 (4) ◽  
pp. 1443-1465 ◽  
Author(s):  
Marco de Bruine ◽  
Maarten Krol ◽  
Twan van Noije ◽  
Philippe Le Sager ◽  
Thomas Röckmann
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Climate Models ◽  
Circulation Model ◽  
Global Climate Models ◽  
Orthogonal Polarization ◽  
Earth Model ◽  
Climate Projections ◽  
Aerosol Distribution ◽  
The Impact

Abstract. The representation of aerosol–cloud interaction in global climate models (GCMs) remains a large source of uncertainty in climate projections. Due to its complexity, precipitation evaporation is either ignored or taken into account in a simplified manner in GCMs. This research explores various ways to treat aerosol resuspension and determines the possible impact of precipitation evaporation and subsequent aerosol resuspension on global aerosol burdens and distribution. The representation of aerosol wet deposition by large-scale precipitation in the EC-Earth model has been improved by utilising additional precipitation-related 3-D fields from the dynamical core, the Integrated Forecasting System (IFS) general circulation model, in the chemistry and aerosol module Tracer Model, version 5 (TM5). A simple approach of scaling aerosol release with evaporated precipitation fraction leads to an increase in the global aerosol burden (+7.8 to +15 % for different aerosol species). However, when taking into account the different sizes and evaporation rate of raindrops following Gong et al. (2006), the release of aerosols is strongly reduced, and the total aerosol burden decreases by −3.0 to −8.5 %. Moreover, inclusion of cloud processing based on observations by Mitra et al. (1992) transforms scavenged small aerosol to coarse particles, which enhances removal by sedimentation and hence leads to a −10 to −11 % lower aerosol burden. Finally, when these two effects are combined, the global aerosol burden decreases by −11 to −19 %. Compared to the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations, aerosol optical depth (AOD) is generally underestimated in most parts of the world in all configurations of the TM5 model and although the representation is now physically more realistic, global AOD shows no large improvements in spatial patterns. Similarly, the agreement of the vertical profile with Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite measurements does not improve significantly. We show, however, that aerosol resuspension has a considerable impact on the modelled aerosol distribution and needs to be taken into account.

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