scholarly journals A Comparison of Initial Developments Between Explosive and Ordinary Mid-latitude Cyclones Off the East Asian Coast in Winter

2021 ◽  
Author(s):  
Xiaoyu Gao ◽  
Ping Lu ◽  
Yang Hu ◽  
Shuqin Zhang ◽  
Xiaoyan Sun ◽  
...  
Keyword(s):  
Human Life ◽  
East Asian ◽  
Baroclinic Instability ◽  
Wrf Model ◽  
Detailed Comparison ◽  
Static Stability ◽  
Reanalysis Data ◽  
Sensitivity Experiment ◽  
Initial Development ◽  
Explosive Cyclones

Abstract Explosive cyclones (ECs) off the East Asian coast post challenges in forecasting and significant threats to human life and property. In searching for the key features that distinguish explosive cyclones (ECs) from ordinary extratropical cyclones (OCs), this study presents detailed comparison of winter ECs versus OCs in the perspective of potential vorticity (PV) using 10 years of reanalysis data with high temporal and spatial resolutions. ECs feature greater low-level baroclinity and stronger PV than OCs. The decomposition of local PV tendency shows the important contribution of cold advection (with correlation coefficient of 0.8) in the initial development of ECs. A stronger cold advection for ECs increases upstream static stability, leading to intrusion of higher PV along the steeper isentropic surfaces. The importance of cold advection is further proved by numerical experiments with the Weather Research and Forecast (WRF) model on a typical winter EC. The weakening of cold advection within low-troposphere in sensitivity experiment can significantly decrease PV and stop the cyclone from explosive deepening. In addition to the consensus that diabatic processes play important roles in the intensification of explosive cyclogenesis, this study emphasizes the importance of horizontal cold advection (which is also associated with baroclinic instability) in the preconditioning PV for explosive cyclogenesis.

Impacts of Multi-Timescale Circulations on Meridional Moisture Transport

2021 ◽  
pp. 1-64
Author(s):  
Qiao Liu ◽  
Tim Li ◽  
Weican Zhou
Keyword(s):  
Moisture Transport ◽  
Baroclinic Instability ◽  
Wrf Model ◽  
Phase Relationship ◽  
Reanalysis Data ◽  
Specific Humidity ◽  
Small Contribution ◽  
Wind Variability ◽  
The Mean ◽  
Meridional Moisture Transport

AbstractRelative impacts of the climatological annual mean, the climatological annual variation, the synoptic, the intra-seasonal and the inter-annual flows on meridional moisture transport were investigated based on reanalysis data. Due to an in-phase relationship between the poleward wind and specific humidity, the synoptic and intra-seasonal motions contribute about 50% and 30% of the maximum zonal and annual mean poleward moisture transport in the middle latitudes, respectively. The preferred latitudinal location (40°N or S) of the maximum zonal mean moisture transport by the synoptic motion is attributed to the combined effect of the maximum wind variability poleward of 40°N or S in association with atmospheric baroclinic instability and the maximum moisture variability equatorward of 40°N or S in association with the anomalous advection of the mean moisture. While the MJO and ENSO have a small contribution to the long-term mean transport, they may strongly affect regional moisture transport through interaction with the mean moisture and through the modulation to higher-frequency modes. A statistical relationship between tropical cyclone (TC) moisture and intensity was constructed based on a large number of high-resolution Weather Research and Forecasting (WRF) model simulations, and the so-derived relationship was further applied to estimate TC moisture transport. It is found that TC transport accounts for about 30% (53%) of the climatological seasonal mean total moisture transport over key northern (southern) hemispheric TC track regions in the northern (southern) hemispheric TC season.

scholarly journals The concurrence of Atmospheric Rivers and explosive cyclogenesis in the North Atlantic and North Pacific basins

2017 ◽  
Author(s):  
Jorge Eiras-Barca ◽  
Alexandre M. Ramos ◽  
Joaquim G. Pinto ◽  
Ricardo M. Trigo ◽  
Margarida L. R. Liberato ◽  
...  
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Reanalysis Data ◽  
Water Vapour Flux ◽  
Atmospheric Rivers ◽  
The North ◽  
Explosive Cyclones ◽  
The North Atlantic ◽  
Characteristic Features ◽  
Western Side

Abstract. The explosive cyclogenesis of extra-tropical cyclones and the occurrence of atmospheric rivers are characteristic features of baroclinic atmospheres, and are both closely related to extreme hydrometeorological events in the mid-latitudes, particularly on coastal areas on the western side of the continents. The potential role of atmospheric rivers in the explosive cyclone deepening has been previously analysed for selected case studies, but a general assessment from the climatological perspective is still missing. Using ERA-Interim reanalysis data for 1979–2011, we analyse the concurrence of atmospheric rivers and explosive cyclogenesis over the North Atlantic and North Pacific Basins for the extended winter months (ONDJFM). Atmospheric rivers are identified for almost 80 % of explosive deepening cyclones. For non-explosive cyclones, atmospheric rivers are found only in roughly 40 % of the cases. The analysis of the time evolution of the high values of water vapour flux associated with the atmospheric river during the cyclone development phase leads us to hypothesize that the identified relationship is the fingerprint of a mechanism that raises the odds of an explosive cyclogenesis occurrence and not merely a statistical relationship. This insight can be helpful for the predictability of high impact weather associated with explosive cyclones and atmospheric rivers.

scholarly journals Assessing the Potential of a Long-Term Climate Forecast for Cuba Using the WRF Model

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Lourdes Álvarez-Escudero ◽  
Yandy G. Mayor ◽  
Israel Borrajero-Montejo ◽  
Arnoldo Bezanilla-Morlot
Keyword(s):  
Mesoscale Model ◽  
Initial Conditions ◽  
Wrf Model ◽  
Reanalysis Data ◽  
Weather Research And Forecasting ◽  
Tropical Storms ◽  
Precipitation Regime ◽  
Wide Debate ◽  
One Year ◽  
Cumulative Precipitation

Seasonal climatic prediction studies are a matter of wide debate all over the world. Cuba, a mainly agricultural nation, should greatly benefit from the knowledge, which is available months in advance of the precipitation regime and allows for the proper management of water resources. In this work, a series of six experiments were made with a mesoscale model WRF (Weather Research and Forecasting Model) that produced a 15-month forecast for each month of cumulative precipitation starting at two dates, and for three non-consecutive years with different meteorological characteristics: one dry year (2004), one year that started dry and turned rainy (2005), and one year where several tropical storms occurred (2008). ERA-Interim reanalysis data were used for the initial and border conditions and experiments started 1 month before the beginning of the rainy and the dry seasons, respectively. In a general sense, the experience of using WRF indicated that it was a valid resource for seasonal forecast, since the results obtained were in the same range as those reported by the literature for similar cases. Several limitations were revealed by the results: the forecasts underestimated the monthly cumulative precipitation figures, tropical storms entering through the borders sometimes followed courses different from the real courses inside the working domain, storms that developed inside the domain were not reproduced by WRF, and differences in initial conditions led to significantly different forecasts for the corresponding time steps (nonlinearity). Changing the model parameterizations and initial conditions of the ensemble forecast experiments was recommended.

Non-linearity in the pathway of El Niño-Southern Oscillation to the tropical North Atlantic

2021 ◽  
pp. 1-54
Author(s):  
Jake W. Casselman ◽  
Andréa S. Taschetto ◽  
Daniela I.V. Domeisen
Keyword(s):  
North Atlantic ◽  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Southern Oscillation ◽  
Static Stability ◽  
Reanalysis Data ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Tropical North Atlantic

AbstractEl Niño-Southern Oscillation can influence the Tropical North Atlantic (TNA), leading to anomalous sea surface temperatures (SST) at a lag of several months. Several mechanisms have been proposed to explain this teleconnection. These mechanisms include both tropical and extratropical pathways, contributing to anomalous trade winds and static stability over the TNA region. The TNA SST response to ENSO has been suggested to be nonlinear. Yet the overall linearity of the ENSO-TNA teleconnection via the two pathways remains unclear. Here we use reanalysis data to confirm that the SST anomaly (SSTA) in the TNA is nonlinear with respect to the strength of the SST forcing in the tropical Pacific, as further increases in El Niño magnitudes cease to create further increases of the TNA SSTA. We further show that the tropical pathway is more linear than the extratropical pathway by sub-dividing the inter-basin connection into extratropical and tropical pathways. This is confirmed by a climate model participating in the CMIP5. The extratropical pathway is modulated by the North Atlantic Oscillation (NAO) and the location of the SSTA in the Pacific, but this modulation insufficiently explains the nonlinearity in TNA SSTA. As neither extratropical nor tropical pathways can explain the nonlinearity, this suggests that external factors are at play. Further analysis shows that the TNA SSTA is highly influenced by the preconditioning of the tropical Atlantic SST. This preconditioning is found to be associated with the NAO through SST-tripole patterns.

scholarly journals A comparison between the GNSS tomography technique and the WRF model in retrieving 3D wet refractivity field in Hong Kong

2018 ◽  
Author(s):  
Zhaohui Xiong ◽  
Bao Zhang ◽  
Yibin Yao
Keyword(s):  
Hong Kong ◽  
Water Vapor ◽  
Weather Prediction ◽  
Wrf Model ◽  
Vertical Direction ◽  
Lower Troposphere ◽  
Reanalysis Data ◽  
Radiosonde Data ◽  
Rainy Period ◽  
Lower Accuracy

Abstract. Water vapor plays an important role in various scales of weather processes. However, there are limited means to monitor its 3-dimensional (3D) dynamical changes. The Numerical Weather Prediction (NWP) model and the Global Navigation Satellite System (GNSS) tomography technique are two of the limited means. Here, we conduct an interesting comparison between the GNSS tomography technique and the Weather Research and Forecasting (WRF) model (a representative of the NWP models) in retrieving Wet Refractivity (WR) in Hong Kong area during a rainy period and a rainless period. The GNSS tomography technique is used to retrieve WR from the GNSS slant wet delay. The WRF Data Assimilation (WRFDA) model is used to assimilate GNSS Zenith Tropospheric Delay (ZTD) to improve the background data. The WRF model is used to generate reanalysis data using the WRFDA output as the initial values. The radiosonde data are used to validate the WR derived from the GNSS tomography and the reanalysis data. The Root Mean Square (RMS) of the tomographic WR, the reanalysis WR that assimilate GNSS ZTD, and the reanalysis WR that without assimilating GNSS ZTD are 6.50 mm/km, 4.31 mm/km and 4.15 mm/km in the rainy period. The RMS becomes 7.02 mm/km, 7.26 mm/km and 6.35 mm/km in the rainless period. The lower accuracy in the rainless period is mainy due to the sharp variation of WR in the vertical direction. The results also show that assimilating GNSS ZTD into the WRFDA model only slightly improves the accuracy of the reanalysis WR and that the reanalysis WR is better than the tomographic WR in most cases. However, in a special experimental period when the water vapor is highly concentrated in the lower troposphere, the tomographic WR outperforms the reanalysis WR in the lower troposphere. When we assimilate the tomographic WR in the lower troposphere into the WRFDA model, the reanalysis WR is improved.

scholarly journals On the Effect of Red Sea and Topography on Rainfall over Saudi Arabia: Case Study

Atmosphere ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 669
Author(s):  
Al-Mutairi ◽  
Abdel Basset ◽  
Morsy ◽  
Abdeldym
Keyword(s):  
Saudi Arabia ◽  
Red Sea ◽  
Sea Water ◽  
Wrf Model ◽  
Temporal Distribution ◽  
Surface Fluxes ◽  
Sensitivity Experiment ◽  
Low Level ◽  
Spatio Temporal ◽  
The Impact

This paper aimed to investigate the impact of Red Sea topography and water on the development and rainfall of a case of cyclogenesis occurs over Saudi Arabia during the period 16–18 November 2015 using the Weather Research and Forecasting (WRF) model. The WRF Control Run (WRF-CR) experiment was performed with presence of actual topography and surface water of the Red Sea, while the other three sensitivity experiments were carried out without (i) Red Sea Topography (NRST), (ii) Red Sea Water (NRSW), and (iii) Red Sea Topography and Water (NRSTW). The simulated rainfall in the control experiment depicts in well agreement with Tropical Rainfall Measurement Mission (TRMM) rainfall estimates in terms of intensity as well as spatio-temporal distribution. Results demonstrate that rainfall intensity and spatio-temporal distribution significantly changes through each sensitivity experiment compared to the WRF-CR, where the significant variation was found in the NRST experiment. The absence of topography (NRST) leads to formation of strong convergence area over the middle of Red Sea which enhanced uplift motion that further strengthened the low-level jet over Red Sea and the surrounding regions, which enhanced the moisture and temperature gradient and created a conditionally unstable atmosphere that favored the development of the cyclonic system. The absence of Red Sea water (NRSW) changed rainfall spatial distribution and reduced its amount by about 30–40% due to affecting of the dynamics of the upward motion and moisture gradient, suggesting that surface fluxes play an important role in regulating the low-level moist air convergence prior to convection initiation and development.

scholarly journals Evaluating Multiple WRF Configurations and Forcing over the Northern Patagonian Icecap (NPI) and Baker River Basin

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 815
Author(s):  
Marcelo Somos-Valenzuela ◽  
Francisco Manquehual-Cheuque
Keyword(s):  
River Basin ◽  
Land Surface ◽  
Weather Prediction ◽  
Wrf Model ◽  
Land Surface Model ◽  
Short Wave ◽  
Reanalysis Data ◽  
Wave Radiation ◽  
Surface Model ◽  
Nwp Model

The use of numerical weather prediction (NWP) model to dynamically downscale coarse climate reanalysis data allows for the capture of processes that are influenced by land cover and topographic features. Climate reanalysis downscaling is useful for hydrology modeling, where catchment processes happen on a spatial scale that is not represented in reanalysis models. Selecting proper parameterization in the NWP for downscaling is crucial to downscale the climate variables of interest. In this work, we are interested in identifying at least one combination of physics in the Weather Research Forecast (WRF) model that performs well in our area of study that covers the Baker River Basin and the Northern Patagonian Icecap (NPI) in the south of Chile. We used ERA-Interim reanalysis data to run WRF in twenty-four different combinations of physics for three years in a nested domain of 22.5 and 4.5 km with 34 vertical levels. From more to less confident, we found that, for the planetary boundary layer (PBL), the best option is to use YSU; for the land surface model (LSM), the best option is the five-Layer Thermal, RRTM for longwave, Dudhia for short wave radiation, and Thompson for the microphysics. In general, the model did well for temperature (average, minimum, maximum) for most of the observation points and configurations. Precipitation was good, but just a few configurations stood out (i.e., conf-9 and conf-10). Surface pressure and Relative Humidity results were not good or bad, and it depends on the statistics with which we evaluate the time series (i.e., KGE or NSE). The results for wind speed were inferior; there was a warm bias in all of the stations. Once we identify the best configuration in our experiment, we run WRF for one year using ERA5 and FNL0832 climate reanalysis. Our results indicate that Era-interim provided better results for precipitation. In the case of temperature, FNL0832 gave better results; however, all of the models’ performances were good. Therefore, working with ERA-Interim seems the best option in this region with the physics selected. We did not experiment with changes in resolution, which may have improved results with ERA5 that has a better spatial and temporal resolution.

scholarly journals Moist Formulations of the Eliassen–Palm Flux and Their Connection to the Surface Westerlies

2017 ◽  
Vol 74 (2) ◽  
pp. 513-530 ◽  
Author(s):  
John G. Dwyer ◽  
Paul A. O’Gorman
Keyword(s):  
Wave Propagation ◽  
Lower Troposphere ◽  
Static Stability ◽  
Reanalysis Data ◽  
Similar Amount ◽  
Mean Flow ◽  
Flux Divergence ◽  
Equivalent Potential ◽  
Subtropical Jet ◽  
Anomalous Region

Abstract The Eliassen–Palm (EP) flux is an important diagnostic for wave propagation and wave–mean flow interaction in the atmosphere. Here, two moist formulations of the EP flux are compared with the traditional dry EP flux, and their links to the surface westerlies are analyzed using reanalysis data and simulations with GCMs. The first moist formulation of the EP flux modifies only the static stability to account for latent heat release by eddies, while the second moist formulation simply replaces all potential temperatures with equivalent potential temperatures. For reanalysis data, the peak upward EP flux in the lower troposphere is farther equatorward and stronger when the moist formulations are used, with greater changes for the second moist formulation. The moist formulations have the advantage of giving a closer relationship over the seasonal cycle between the latitudes of the peak surface westerlies and the peak upward EP flux. In simulations with a comprehensive GCM, the dry and moist upward EP fluxes shift poleward by a similar amount as the climate warms. In simulations over a wider range of climates with an idealized GCM, the surface westerlies can shift both poleward and equatorward with warming, and they are influenced by an anomalous region of dry EP flux divergence near the subtropical jet. Using moist EP fluxes weakens this anomalous divergence in the idealized GCM simulations, and the shifts in the surface westerlies can then be understood through changes in the preference for equatorward or poleward wave propagation.

scholarly journals Case Study of Potential Vorticity Tower in Three Explosive Cyclones over Eastern Asia

2017 ◽  
Vol 74 (5) ◽  
pp. 1445-1454 ◽  
Author(s):  
Huaji Pang ◽  
Gang Fu
Keyword(s):  
Potential Vorticity ◽  
Morphological Characteristics ◽  
Lower Troposphere ◽  
Static Stability ◽  
Relative Vorticity ◽  
Eastern Asia ◽  
The North ◽  
Surface Cyclone ◽  
Explosive Cyclones

AbstractThree cases of explosively developing extratropical cyclones over eastern Asia are analyzed using ERA-Interim data. The morphological characteristics of the upper-tropospheric potential vorticity (PV) were examined. The common feature of all of these three cases is a hook-shaped high-PV streamer wrapping counterclockwise around the center of surface cyclones on the southern and eastern sides and an arch-shaped low-PV tongue that wrapped the high-PV hook head from the north. The hook-shaped high-PV tongue overlaps with the maximum centers of both the relative vorticity and static stability parameter, indicating the stratospheric nature of the PV source inside the hook-shaped high-PV tongue.The analysis indicates that there existed a deep tower of high PV above the surface cyclone at the time when these cyclones underwent explosive cyclogenesis. The high PV in the upper troposphere originates from the polar stratospheric PV reservoir associated with the tropopause-folding process. The high PV in the lower troposphere, however, is associated with the latent heat release, as nearly 70%–90% of the high-PV values in the lower troposphere reside in the region where the rainfall is the heaviest.

Sign in / Sign up

Export Citation Format

Share Document