Simulations of the Boreal Winter Upper Mesosphere and Lower Thermosphere With Meteorological Specifications in SD‐WACCM‐X

Sassi, Fabrizio; Siskind, David E.; Tate, J.; Liu, Hanli; Randall, C. E.

doi:10.1002/2017jd027782

Cited by 16 publications

(18 citation statements)

References 65 publications

(128 reference statements)

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“…Smith‐Johnsen et al () showed better agreement with observations when D region chemistry was added to the Whole Atmosphere Community Climate Model (WACCM) but the NO underestimate persisted between 90 and 110 km. Recent studies have shown that either constraining the model up to 90 km or assimilating mesospheric data improves the representation of the EPP IE (Pedatella, Liu, et al, ; Sassi et al, ; Siskind et al, ). In the Antarctic, Hendrickx et al () show EPP‐NO x underestimates despite MLT descent rates in WACCM that agree with observations.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Mesospheric Polar Vortices in WACCM

et al. 2019

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This work evaluates the wintertime mesospheric polar vortices in the Whole Atmosphere Community Climate Model. Mesospheric altitudes are where high‐top models underestimate the concentration of nitrogen oxides produced by energetic particle precipitation. For this reason, we seek to determine the extent to which the observed mesospheric vortex size and frequency of occurrence is reproduced by the model. We compare 13 years (2005–2017) of “specified dynamics” Whole Atmosphere Community Climate Model (where meteorology in the troposphere and stratosphere is constrained by observations) to Sounding of the Atmosphere using Broadband Emission Radiometry and Mesospheric Limb Sounder observations. Near 75 km, the model reproduces observed winter mesospheric vortex frequency of occurrence rates and size reasonably well. The simulated Antarctic mesospheric vortex is displaced toward the Pacific longitude sector, and the Arctic mesospheric vortex is present 10–20% less often over the pole but ~5% more often in midlatitudes, particularly over the continents. These differences are attributed to larger planetary waves in the model. There are significant differences between the modeled and observed mean polar winter circulation near 90 km. Model‐measurement differences suggest that the simulated Antarctic mesospheric vortex does not extend to high enough altitudes, and the Arctic mesospheric vortex is too displaced from the pole. Despite these differences, the model accurately captures the evolution of structural changes to the mesospheric vortex following prolonged sudden stratospheric warmings. Thus, we conclude that model underestimates of nitrogen oxides produced by energetic particle precipitation after these warmings are not due to a misrepresentation of the mesospheric vortex strength and size below 80 km.

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Section: Introductionmentioning

confidence: 99%

Evaluation of the Mesospheric Polar Vortices in WACCM

et al. 2019

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“…Global climate models (GCMs) underestimate these effects (Funke et al, ; Hendrickx et al, ; Holt et al, ; Orsolini et al, ; Randall et al, ; Sheese et al, ), and optimum performance occurs when the models are constrained by observations to mesospheric heights (Pedatella et al, ; Sassi et al, ; Siskind et al, ). Indeed, GCMs often simulate a reversal of the winter westerlies above 70–80 km that is not consistent with observations (e.g., Smith, , see their Figure 2).…”

Section: Introductionmentioning

confidence: 99%

On the Upward Extension of the Polar Vortices Into the Mesosphere

et al. 2018

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The polar vortices play a central role in vertically coupling the atmosphere from the ground to geospace by shaping the background wind field through which atmospheric waves propagate. This work extends the vertical range of previous polar vortex climatologies into the upper mesosphere. The mesospheric polar vortices are defined using the CO gradient method with Microwave Limb Sounder satellite data; the stratospheric polar vortices are defined using a stream function‐based algorithm with data from meteorological reanalyses. Strengths and weaknesses of the two vortex definitions are given, as well as recommendations for when, where, and why to use each definition. Midwinter mean vortex geometry in the mesosphere is funnel shaped in the Arctic, with a wide top and narrow bottom. The Antarctic mesospheric vortex tapers with height in early winter and broadens with height in late winter. The seasonal evolution of mesospheric vortex frequency of occurrence, size, and zonal symmetry in both hemispheres is presented. Unexpected behavior above 60 km includes late season vortex broadening in both hemispheres, especially following winters without sudden stratospheric warmings. Following extreme stratospheric disturbances the polar night jet in the mesosphere strengthens and shifts poleward, resulting in a mesospheric vortex that contracts. Overall, the mesospheric polar vortices are more similar between the two hemispheres than their stratospheric counterparts. The vortex climatology presented here serves as an observational benchmark to which the mesospheric polar vortices in high‐top climate models can be evaluated.

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“…They indicated that better analysis of the mesosphere requires assimilation of the mesospheric 150 observational data. Similar discussion was made by Sassi et al (2018) using the Specified Dynamics (SD)-WACCM, in which a nudging method was implemented. The reality of the analysis highly depends on the model's performance in the MLT region.…”

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confidence: 88%

An ensemble Kalman filter data assimilation system for the whole neutral atmosphere

Koshin

Sato

Miyazaki

et al. 2019

Preprint

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Abstract. A data assimilation system with a four-dimensional local ensemble transform Kalman filter (4D-LETKF) is developed to make a new analysis data for the atmosphere up to the lower thermosphere using the Japanese Atmospherics General Circulation model for Upper Atmosphere Research. The time period from 10 January 2017 to 20 February 2017, when an international radar network observation campaign was performed, is focused on. The model resolution is T42L124 which can resolve phenomena at synoptic and larger scales. A conventional observation dataset provided by National Centers for Environmental Prediction, PREPBUFR, and satellite temperature data from the Aura Microwave Limb Sounder (MLS) for the stratosphere and mesosphere are assimilated. First, the performance of the forecast model is improved by modifying the vertical profile of the horizontal diffusion coefficient and modifying the source intensity in the non-orographic gravity wave parameterization, by comparing it with radar wind observations in the mesosphere. Second, the MLS observational bias is estimated as a function of the month and latitude and removed before the data assimilation. Third, data assimilation parameters, such as the degree of gross error check, localization length, inflation factor, and assimilation window are optimized based on a series of sensitivity tests. The effect of increasing the ensemble member size is also examined. The obtained global data are evaluated by comparison with the Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2) reanalysis data covering pressure levels up to 0.1 hPa and by the radar mesospheric observations which are not assimilated.

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Simulations of the Boreal Winter Upper Mesosphere and Lower Thermosphere With Meteorological Specifications in SD‐WACCM‐X

Cited by 16 publications

References 65 publications

Evaluation of the Mesospheric Polar Vortices in WACCM

Evaluation of the Mesospheric Polar Vortices in WACCM

On the Upward Extension of the Polar Vortices Into the Mesosphere

An ensemble Kalman filter data assimilation system for the whole neutral atmosphere

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