scholarly journals OZO v.1.0: software for solving a generalised omega equation and the Zwack–Okossi height tendency equation using WRF model output

2017 ◽  
Vol 10 (2) ◽  
pp. 827-841 ◽  
Author(s):  
Mika Rantanen ◽  
Jouni Räisänen ◽  
Juha Lento ◽  
Oleg Stepanyuk ◽  
Olle Räty ◽  
...  
Keyword(s):  
Diabatic Heating ◽  
Physical Mechanism ◽  
Wrf Model ◽  
Vertical Motion ◽  
Weather Research And Forecasting ◽  
Cartesian Geometry ◽  
Diabatic Processes ◽  
Research And Education ◽  
The Individual ◽  
Omega Equation

Abstract. A software package (OZO, Omega–Zwack–Okossi) was developed to diagnose the processes that affect vertical motions and geopotential height tendencies in weather systems simulated by the Weather Research and Forecasting (WRF) model. First, this software solves a generalised omega equation to calculate the vertical motions associated with different physical forcings: vorticity advection, thermal advection, friction, diabatic heating, and an imbalance term between vorticity and temperature tendencies. After this, the corresponding height tendencies are calculated with the Zwack–Okossi tendency equation. The resulting height tendency components thus contain both the direct effect from the forcing itself and the indirect effects (related to the vertical motion induced by the same forcing) of each physical mechanism. This approach has an advantage compared with previous studies with the Zwack–Okossi equation, in which vertical motions were used as an independent forcing but were typically found to compensate the effects of other forcings.The software is currently tailored to use input from WRF simulations with Cartesian geometry. As an illustration, results for an idealised 10-day baroclinic wave simulation are presented. An excellent agreement is found between OZO and the direct WRF output for both the vertical motion and the height tendency fields. The individual vertical motion and height tendency components demonstrate the importance of both adiabatic and diabatic processes for the simulated cyclone. OZO is an open-source tool for both research and education, and the distribution of the software will be supported by the authors.

scholarly journals OZO v.1.0: Software for solving a generalized omega equation and the Zwack-Okossi height tendency equation using WRF model output

2016 ◽  
Author(s):  
Mika Rantanen ◽  
Jouni Räisänen ◽  
Juha Lento ◽  
Oleg Stepanyuk ◽  
Olle Räty ◽  
...  
Keyword(s):  
Diabatic Heating ◽  
Physical Mechanism ◽  
Wrf Model ◽  
Vertical Motion ◽  
Weather Research And Forecasting ◽  
Cartesian Geometry ◽  
Diabatic Processes ◽  
Research And Education ◽  
The Individual ◽  
Omega Equation

Abstract. A software package (OZO, Omega-Zwack-Okossi) was developed to diagnose the processes that affect vertical motions and geopotential height tendencies in weather systems simulated by the Weather Research and Forecasting (WRF) model. First, this software solves a generalized omega equation to calculate the vertical motions associated with different physical forcings: vorticity advection, thermal advection, friction, diabatic heating, and an imbalance term between vorticity and temperature tendencies. After this, the corresponding height tendencies are calculated with the Zwack-Okossi tendency equation. The resulting height tendency components thus contain both the direct effect from the forcing itself and the indirect effects (related to the vertical motion induced by the same forcing) of each physical mechanism. This approach has an advantage compared with previous studies with the Zwack-Okossi equation, in which vertical motions were used as an independent forcing but were typically found to compensate the effects of other forcings. The software is tailored to use input from WRF simulations with Cartesian geometry. As an illustration, results for an idealized 10-day baroclinic wave simulation are presented. An excellent agreement is found between OZO and the direct WRF output for both the vertical motion (correlation 0.97 in the midtroposphere) and the height tendency fields (correlation 0.95–0.98 in the whole troposphere). The individual vertical motion and height tendency components demonstrate the importance of both adiabatic and diabatic processes for the simulated cyclone. OZO is an open source tool for both research and education, and the distribution of the software will be supported by the authors.

scholarly journals Application of the Compressible, Nonhydrostatic, Balanced Omega Equation in Estimating Diabatic Forcing for Parameterization of Inertia–Gravity Waves: Case Study of Moist Baroclinic Waves Using WRF

2019 ◽  
Vol 77 (1) ◽  
pp. 113-129
Author(s):  
Mahnoosh Haghighatnasab ◽  
Mohammad Mirzaei ◽  
Ali R. Mohebalhojeh ◽  
Christoph Zülicke ◽  
Riwal Plougonven
Keyword(s):  
Gravity Waves ◽  
General Circulation ◽  
Diabatic Heating ◽  
Wrf Model ◽  
Vertical Motion ◽  
General Circulation Models ◽  
Baroclinic Waves ◽  
Diabatic Forcing ◽  
Omega Equation ◽  
Inertia Gravity Waves

Abstract The parameterization of inertia–gravity waves (IGWs) is of considerable importance in general circulation models. Among the challenging issues faced in studies concerned with parameterization of IGWs is the estimation of diabatic forcing in a way independent of the physics parameterization schemes, in particular, convection. The requirement is to estimate the diabatic heating associated with balanced motion. This can be done by comparing estimates of balanced vertical motion with and without diabatic effects. The omega equation provides the natural method of estimating balanced vertical motion without diabatic effects, and several methods for including diabatic effects are compared. To this end, the assumption of spatial-scale separation between IGWs and balanced flows is combined with a suitable form of the balanced omega equation. To test the methods constructed for estimating diabatic heating, an idealized numerical simulation of the moist baroclinic waves is performed using the Weather Research and Forecasting (WRF) Model in a channel on the f plane. In overall agreement with the diabatic heating of the WRF Model, in the omega-equation-based estimates, the maxima of heating appear in the warm sector of the baroclinic wave and in the exit region of the upper-level jet. The omega-equation-based method with spatial smoothing for estimating balanced vertical motion is thus presented as the proper way to evaluate diabatic forcing for parameterization of IGWs.

scholarly journals Systematic Variation in Wintertime Precipitation in East Asia by MJO-Induced Extratropical Vertical Motion

2008 ◽  
Vol 21 (4) ◽  
pp. 788-801 ◽  
Author(s):  
Jee-Hoon Jeong ◽  
Baek-Min Kim ◽  
Chang-Hoi Ho ◽  
Yeon-Hee Noh
Keyword(s):  
East Asia ◽  
Large Scale ◽  
Diabatic Heating ◽  
Daily Precipitation ◽  
Lower Troposphere ◽  
Vertical Motion ◽  
Mean Value ◽  
Asian Countries ◽  
The Indian Ocean ◽  
Omega Equation

Abstract The variations in the wintertime precipitation over East Asia and the related large-scale circulation associated with the Madden–Julian oscillation (MJO) are examined. By analyzing the observed daily precipitation for the period 1974–2000, it is found that the MJO significantly modulates the distribution of precipitation over four East Asian countries; the precipitation rate difference between wet and dry periods over East Asia, when the centers of MJO convective activities are located over the Indian Ocean and western Pacific, respectively, reaches 3–4 mm day−1, which corresponds to the climatological winter-mean value. Composite analysis with respect to the MJO suggests that the MJO–precipitation relation is mostly explained by the strong vertical motion anomalies near an entrance region of the East Asia upper-tropospheric jet and moisture supply in the lower troposphere. To elucidate different dynamic origins of the vertical motion generated by the MJO, diagnostic analysis of a generalized omega equation is adopted. It is revealed that about half of the vertical motion anomalies in East Asia are induced by the quasigeostrophic forcings by the MJO, while diabatic heating forcings explain a very small fraction, less than 10% of total anomalies.

An Evaluation of a Hybrid, Terrain-Following Vertical Coordinate in the WRF-Based RAP and HRRR Models

2020 ◽  
Vol 35 (3) ◽  
pp. 1081-1096 ◽  
Author(s):  
Jeffrey Beck ◽  
John Brown ◽  
Jimy Dudhia ◽  
David Gill ◽  
Tracy Hertneky ◽  
...  
Keyword(s):  
Complex Terrain ◽  
Wrf Model ◽  
Vertical Motion ◽  
Weather Research And Forecasting ◽  
Mountainous Terrain ◽  
Vertical Coordinate ◽  
Numerical Noise ◽  
Terrain Following ◽  
Model Equations ◽  
Real Time Simulations

Abstract A new hybrid, sigma-pressure vertical coordinate was recently added to the Weather Research and Forecasting (WRF) Model in an effort to reduce numerical noise in the model equations near complex terrain. Testing of this hybrid, terrain-following coordinate was undertaken in the WRF-based Rapid Refresh (RAP) and High-Resolution Rapid Refresh (HRRR) models to assess impacts on retrospective and real-time simulations. Initial cold-start simulations indicated that the majority of differences between the hybrid and traditional sigma coordinate were confined to regions downstream of mountainous terrain and focused in the upper levels. Week-long retrospective simulations generally resulted in small improvements for the RAP, and a neutral impact in the HRRR when the hybrid coordinate was used. However, one possibility is that the inclusion of data assimilation in the experiments may have minimized differences between the vertical coordinates. Finally, analysis of turbulence forecasts with the new hybrid coordinate indicate a significant reduction in spurious vertical motion over the full length of the Rocky Mountains. Overall, the results indicate a potential to improve forecast metrics through implementation of the hybrid coordinate, particularly at upper levels, and downstream of complex terrain.

scholarly journals Effects of Asymmetric SST Distribution on Straight-Moving Typhoon Ewiniar (2006) and Recurving Typhoon Maemi (2003)

2013 ◽  
Vol 141 (11) ◽  
pp. 3950-3967 ◽  
Author(s):  
Yumi Choi ◽  
Kyung-Sook Yun ◽  
Kyung-Ja Ha ◽  
Kwang-Yul Kim ◽  
Soon-Jo Yoon ◽  
...  
Keyword(s):  
Diabatic Heating ◽  
Physical Mechanism ◽  
Vertical Wind Shear ◽  
Sea Surface ◽  
Weather Research And Forecasting ◽  
Forecasting Model ◽  
Asymmetric Flow ◽  
Horizontal Advection ◽  
Acceleration And Deceleration ◽  
Sst Forcing

Abstract The effects of asymmetric sea surface temperature (SST) distribution on the tropical cyclone (TC) motion around East Asia have been examined using the Weather Research and Forecasting Model for the straight-moving Typhoon Ewiniar (2006) and recurving Typhoon Maemi (2003). The SST–TC motion relationships associated with the two different TCs and the physical mechanism of recurvature are investigated in the context of the potential vorticity tendency framework. A zonally asymmetric SST distribution alters the TC translating direction and speed, which is ascribable to the interaction between a TC and the environmental current associated with asymmetric SST forcing. A north–south SST gradient has an insignificant role in the TC motion. It is noted that the straight-moving (i.e., northward moving) TC deflects toward the region of warmer SST when SST is zonally asymmetric. A contribution of the horizontal advection including asymmetric flow induced by asymmetric forcing is dominant for the deflection. The recurving TC reveals northeastward acceleration and deceleration after the recurvature point in the western warming (WW) and eastern warming (EW) experiments, respectively. When it comes to a strong southerly vertical wind shear under the recurvature condition, diabatic heating can be a significant physical process associated with the downward motion over the region of upshear right. The enhanced (reduced) southwesterly flow effectively produces the acceleration (deceleration) of northeastward movement in WW (EW) after recurvature.

Simulation of the Downshear Reformation of a Tropical Cyclone

2015 ◽  
Vol 72 (12) ◽  
pp. 4529-4551 ◽  
Author(s):  
Leon T. Nguyen ◽  
John Molinari
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Diabatic Heating ◽  
Wrf Model ◽  
Relative Vorticity ◽  
Horizontal Resolution ◽  
Cyclonic Circulation ◽  
Tropical Storm ◽  
Weather Research And Forecasting ◽  
Cyclonic Vorticity

Abstract The downshear reformation of Tropical Storm Gabrielle (2001) was simulated at 1-km horizontal resolution using the Weather Research and Forecasting (WRF) Model. The environmental shear tilted the initial parent vortex downshear left and forced azimuthal wavenumber-1 kinematic, thermodynamic, and convective asymmetries. The combination of surface enthalpy fluxes and a lack of penetrative downdrafts right of shear allowed boundary layer moist entropy to increase to a maximum downshear right. This contributed to convective instability that fueled the downshear convection. Within this convection, an intense mesovortex rapidly developed, with maximum boundary layer relative vorticity reaching 2.2 × 10−2 s−1. Extreme vortex stretching played a key role in the boundary layer spinup of the mesovortex. Cyclonic vorticity remained maximized in the boundary layer and intensified upward with the growth of the convective plume. The circulation associated with the mesovortex and adjacent localized cyclonic vorticity anomalies comprised a developing “inner vortex” on the downshear-left (downtilt) periphery of the parent cyclonic circulation. The inner vortex was nearly upright within a parent vortex that was tilted significantly with height. This inner vortex became the dominant vortex of the system, advecting and absorbing the broad, tilted parent vortex. The reduction of tropical cyclone (TC) vortex tilt from 65 to 20 km in 3 h reflected the emerging dominance of this upright inner vortex. The authors hypothesize that downshear reformation, resulting from diabatic heating associated with asymmetric convection, can aid the TC’s resistance to shear by reducing vortex tilt and by enabling more diabatic heating to occur near the center, a region known to favor TC intensification.

scholarly journals The characteristics and structure of extra-tropical cyclones in a warmer climate

2020 ◽  
Vol 1 (1) ◽  
pp. 1-25 ◽  
Author(s):  
Victoria A. Sinclair ◽  
Mika Rantanen ◽  
Päivi Haapanala ◽  
Jouni Räisänen ◽  
Heikki Järvinen
Keyword(s):  
Tropical Cyclones ◽  
Diabatic Heating ◽  
Vertical Motion ◽  
Atmospheric Model ◽  
Sea Surface ◽  
Intermediate Step ◽  
Thermal Advection ◽  
Vorticity Advection ◽  
Omega Equation ◽  
Total Column

Abstract. Little is known about how the structure of extra-tropical cyclones will change in the future. In this study aqua-planet simulations are performed with a full-complexity atmospheric model. These experiments can be considered an intermediate step towards increasing knowledge of how, and why, extra-tropical cyclones respond to warming. A control simulation and a warm simulation in which the sea surface temperatures are increased uniformly by 4 K are run for 11 years. Extra-tropical cyclones are tracked, cyclone composites created, and the omega equation applied to assess causes of changes in vertical motion. Warming leads to a 3.3 % decrease in the number of extra-tropical cyclones, with no change to the median intensity or lifetime of extra-tropical cyclones but to a broadening of the intensity distribution resulting in both more stronger and more weaker storms. Composites of the strongest extra-tropical cyclones show that total column water vapour increases everywhere relative to the cyclone centre and that precipitation increases by up to 50 % with the 4 K warming. The spatial structure of the composite cyclone changes with warming: the 900–700 hPa layer averaged potential vorticity, 700 hPa ascent, and precipitation maximums associated with the warm front all move polewards and downstream, and the area of ascent expands in the downstream direction. Increases in ascent forced by diabatic heating and thermal advection are responsible for the displacement, whereas increases in ascent due to vorticity advection lead to the downstream expansion. Finally, maximum values of ascent due to vorticity advection and thermal advection weaken slightly with warming, whereas those attributed to diabatic heating increase. Thus, cyclones in warmer climates are more diabatically driven.

scholarly journals A WRF Ensemble for Improved Wind Speed Forecasts at Turbine Height

2013 ◽  
Vol 28 (1) ◽  
pp. 212-228 ◽  
Author(s):  
Adam J. Deppe ◽  
William A. Gallus ◽  
Eugene S. Takle
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wrf Model ◽  
Absolute Error ◽  
Weather Research And Forecasting ◽  
Speed Increase ◽  
Ramp Events ◽  
Total Capacity ◽  
The Individual ◽  
Horizontal Grid

Abstract The Weather Research and Forecasting Model (WRF) with 10-km horizontal grid spacing was used to explore improvements in wind speed forecasts at a typical wind turbine hub height (80 m). An ensemble consisting of WRF model simulations with different planetary boundary layer (PBL) schemes showed little spread among the individual ensemble members for forecasting wind speed. A second configuration using three random perturbations of the Global Forecast System model produced more spread in the wind speed forecasts, but the ensemble mean possessed a higher mean absolute error (MAE). A third ensemble of different initialization times showed larger model spread, but model MAE was not compromised. In addition, postprocessing techniques such as training of the model for the day 2 forecast based on day 1 results and bias correction based on observed wind direction are examined. Ramp event forecasting was also explored. An event was considered to be a ramp event if the change in wind power was 50% or more of total capacity in either 4 or 2 h or less. This was approximated using a typical wind turbine power curve such that any wind speed increase or decrease of more than 3 m s−1 within the 6–12 m s−1 window (where power production varies greatly) in 4 h or less would be considered a ramp. Model MAE, climatology of ramp events, and causes were examined. All PBL schemes examined predicted fewer ramp events compared to the observations, and model forecasts for ramps in general were poor.

scholarly journals The characteristics and structure of extra-tropical cyclones in a warmer climate

2019 ◽  
Author(s):  
Victoria A. Sinclair ◽  
Mika Rantanen ◽  
Päivi Haapanala ◽  
Jouni Räisänen ◽  
Heikki Järvinen
Keyword(s):  
Tropical Cyclones ◽  
Diabatic Heating ◽  
Vertical Motion ◽  
Life Time ◽  
Atmospheric Model ◽  
Intermediate Step ◽  
Thermal Advection ◽  
Vorticity Advection ◽  
Omega Equation ◽  
Total Column

Abstract. Little is known about how the structure of extra-tropical cyclones will change in the future. In this study aquaplanet simulations are performed with a full complexity atmospheric model. These experiments can be considered as an intermediate step towards increasing knowledge of how, and why, extra-tropical cyclones respond to warming. A control simulation and a warm simulation in which the sea surface temperatures are increased uniformly by 4 K are run for 11 years. Extra-tropical cyclones are tracked, cyclone composites created, and the omega equation applied to assess causes of changes in vertical motion. Warming leads to a 3.3 % decrease in the number of extra-tropical cyclones, no change to the median intensity nor life time of extra-tropical cyclones, but to a broadening of the intensity distribution resulting in both more stronger and more weaker storms. Composites of the strongest extra-tropical cyclones show that total column water vapour increases everywhere relative to the cyclone centre and that precipitation increases by up to 50 % with the 4 K warming. The spatial structure of the composite cyclone changes with warming: the 900–700-hPa layer averaged potential vorticity, 700-hPa ascent and precipitation maximums associated with the warm front all move polewards and downstream and the area of ascent expands in the downstream direction. Increases in ascent forced by diabatic heating and thermal advection are responsible for the displacement whereas increases in ascent due to vorticity advection lead to the downstream expansion. Finally, maximum values of ascent due to vorticity advection and thermal advection weaken slightly with warming whereas those attributed to diabatic heating increase. Thus, cyclones in warmer climates are more diabatically driven.

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