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Introduction
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May 2018 - May 2023
March 2016 - April 2018
September 2014 - February 2016
Publications
Publications (45)
A convective gravity-wave parameterization (GWP) is introduced in the
Met Office Unified Model (MetUM) in addition to the existing GWPs, and
the tropical quasi-biennial oscillation (QBO) is simulated. We replace a
significant amount of momentum flux, which is originally launched by the
background GWP, with the convective gravity-wave (CGW) momentum...
The contributions of the equatorial waves to the quasi-biennial oscillation (QBO) are investigated using Hadley Centre Global Environment Model version 2 (HadGEM2). A gravity wave parameterization that couples its source spectrum to the convection is used. The equatorial wave modes are identified in the spectral domain, based on their distinct char...
Equatorial Kelvin and mixed Rossby–gravity (MRG) waves in the tropical tropopause layer and stratosphere represented in recent reanalyses for the period of 1981–2010 are compared in terms of spectral characteristics, spatial structures, long-term variations, and their forcing of the quasi-biennial oscillation (QBO). For both wave types, the spectra...
In a companion paper, the Multi-Scale Gravity-Wave Model (MS-GWaM) has been introduced and its application to a global model as a transient subgrid-scale parameterization has been described. This paper focuses on the examination of intermittency of gravity waves (GWs) modeled by MS-GWaM. To introduce the variability and intermittency in wave source...
In climate modelling, the reality of simulated flows in the middle atmosphere is largely affected by the model's representation of gravity wave processes that are unresolved, while these processes are usually simplified to facilitate computations. The simplification commonly applied in existing climate models is to neglect wave propagation in horiz...
The Hadley circulation (HC) has been expanding poleward in recent decades. The Coupled Model Intercomparison Project Phase 6 (CMIP6) models predict that the expansion will accelerate in the future, more so in the Southern Hemisphere (SH). However, the extent of the expansion varies widely among the models. We investigate the mechanisms driving the...
The tropical stratosphere is characterized by a periodic oscillation of wind direction between westerly and easterly, known as the quasi-biennial oscillation, which modulates middle atmospheric circulations and surface climate on interannual time scales. The oscillation period fluctuates irregularly between 20 and 35 months. The causes of this fluc...
Infrasound technology is used to monitor atmospheric events in order to guarantee compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Over the 60 infrasound stations initially planned, 53 are operational to date as part of the International Monitoring System (IMS). As opposed to the waveform-related technologies that are used by the I...
Gravity‐wave (GW) parameterizations from 12 general circulation models (GCMs) participating in the Quasi‐Biennial Oscillation initiative (QBOi) are compared with Strateole 2 balloon observations made in the tropical lower stratosphere from November 2019–February 2020 (phase 1) and from October 2021–January 2022 (phase 2). The parameterizations empl...
Parametrizations for internal gravity waves in atmospheric models are traditionally subject to a number of simplifications. Most notably, they rely on both neglecting wave propagation and advection in the horizontal direction (single-column assumption) and an instantaneous balance in the vertical direction (steady-state assumption). While these sim...
The international monitoring system (IMS) has been put in place to monitor compliance with the comprehensive nuclear-test-ban treaty (CTBT). Its infrasound component, dedicated to the monitoring of atmospheric events, gives also room to civil applications (e.g. monitoring of volcanic eruptions, meteorites, severe weather). Infrasound detection capa...
Accurate nowcasting is critical for preemptive action in response to heavy rainfall events (HREs). However, operational numerical weather prediction models have difficulty predicting HREs in the short term, especially for rapidly and sporadically developing cases. Here, we present multi-year evaluation statistics showing that deep-learning-based HR...
In climate modelling, the reality of simulated flows in the middle atmosphere is largely affected by the model's representation of gravity wave processes that are unresolved, while these processes are usually simplified to facilitate computations. The simplification commonly applied in existing climate models is to neglect wave propagation in horiz...
The interaction between small-scale waves and a larger-scale flow can be described by a multi-scale theory that forms the basis for a new class of parameterizations of subgrid-scale gravity waves (GW) in weather and climate models. The development of this theory is reviewed here. It applies to all interesting regimes of atmospheric stratification,...
Convectively generated gravity waves (CGGWs) are important for numerical weather prediction due to their effect on the quasi‐biennial oscillation (QBO) in the stratosphere. Using global ECMWF IFS simulations at TCo7999 (or 1.25 km), TCo2559 (or 3.9 km) and TCo1279 (or 7.8 km) horizontal resolutions, sensitivity of resolved CGGWs to the horizontal r...
A general circulation model is used to study the interaction between parameterized gravity waves (GWs) and large-scale Kelvin waves in the tropical stratosphere. The simulation shows that Kelvin waves with substantial amplitudes (~10 m/s) can significantly affect the distribution of GW drag by modulating the local shear. Furthermore, this effect is...
The Quasi‐biennial Oscillation (QBO) dominates the interannual variability of the tropical stratosphere and influences other regions of the atmosphere. The high predictability of the QBO implies that its teleconnections could lead to increased skill of seasonal and decadal forecasts provided the relevant mechanisms are accurately represented in mod...
Current gravity-wave (GW) parameterization (GWP) schemes are using the steady-state assumption, where an instantaneous balance between GWs and mean flow is postulated, thereby neglecting transient, non-dissipative direct interactions between the GW field and the resolved flow. These schemes rely exclusively on wave dissipation, by GW breaking or ne...
A multi‐model study is carried out to investigate the ability of models to predict the evolution of the quasi‐biennial oscillation (QBO) up to 12 months in advance. All models are initialised from common reanalysis data, and forecasts run for a common set of 30 start dates over 15 years. All models have high skill in predicting the phase evolution...
We analyze the stratospheric waves in models participating in phase 1 of the Stratosphere–troposphere Processes And their Role in Climate (SPARC) Quasi‐Biennial Oscillation initiative (QBOi). All models have robust Kelvin and mixed Rossby‐gravity wave modes in winds and temperatures at 50 hPa and represent them better than most of the Coupled Model...
Quasi‐biennial oscillations (QBOs) in thirteen atmospheric general circulation models forced with both observed and annually repeating sea surface temperatures (SSTs) are evaluated. In most models the QBO period is close to, but shorter than, the observed period of 28 months. Amplitudes are within ±20% of the observed QBO amplitude at 10 hPa, but t...
The Quasi‐Biennial Oscillation initiative (QBOi) is a model intercomparison programme that specifically targets simulation of the QBO in current global climate models. Eleven of the models or model versions that participated in a QBOi intercomparison study have upper boundaries in or above the mesosphere and therefore simulate the region where the...
Equatorial Kelvin and mixed Rossby-gravity (MRG) waves in the tropical tropopause layer and stratosphere represented in recent reanalyses for the period of 1981–2010 are compared in terms of spectral characteristics, spatial structures, long-term variations and their forcing of the quasi-biennial oscillation. For both wave types, the spectral distr...
Jet/front systems are the important sources of the atmospheric gravity waves (GWs). Based on mesoscale simulation results, dominant GWs associated with the jet/front systems have horizontal wavelengths of approximately 150 km, which need for parameterization in global models. Nevertheless, there is no comprehensive parameterization scheme of the je...
We investigated the characteristics of the total ozone column (TOC) around West Antarctica (near the Weddell Sea) compared with ambient meteorological factors. For this analysis, we used ground-based and satellite TOC measurements as well as meteorology (air temperature, potential vorticity and wind field) from reanalysis data. Long-term patterns o...
Characteristics of inertia-gravity waves (IGWs) at high latitude in Antarctica are investigated using radiosondes launched daily at Jang Bogo Station (74°37′S, 164°13′E), a new Antarctic station that has been operating since 2014, in the troposphere (z = 2–7 km) and lower stratosphere (z = 15–22 km) for 25 months (December 2014 to December 2016). T...
A composite-based statistical model utilizing Northern Hemisphere teleconnection patterns is developed to predict East Asian wintertime surface air temperature for lead times out to 6 weeks. The level of prediction is determined by using the Heidke skill score. The prediction skill of the statistical model is compared with that of hindcast simulati...
The characteristics of small-scale convective gravity waves (CGWs; horizontal wavelengths < 100 km) and their contributions to the large-scale flow in the stratosphere, including the quasi-biennial oscillation (QBO), are investigated using an offline calculation of a source-dependent, physically based CGW parameterization with global reanalysis dat...
An iterative dynamic initialization method is presented to produce balanced initial conditions for whole-atmospheric global modeling. In this method, a global hydrostatic numerical model is iteratively nudged towards ground-to-space (G2S) wind and temperature profiles at specific date and time. G2S atmospheric profiles are obtained by fitting splin...
This study implements the parameterizations of convective and frontal gravity wave drag (GWD) with wide phase speed spectra into a global forecast model with a model top near 0.3 hPa. The new convective GWD scheme replaces the existing one that considers only a stationary convective GW, and the frontal GWD scheme is newly introduced. When the new G...
The Stratosphere–troposphere Processes And their Role in Climate (SPARC) Quasi-Biennial Oscillation initiative (QBOi) aims to improve the fidelity of tropical stratospheric variability in general circulation and Earth system models by conducting coordinated numerical experiments and analysis. In the equatorial stratosphere, the QBO is the most cons...
The Stratosphere-troposphere Processes And their Role in Climate (SPARC) Quasi-Biennial Oscillation initiative (QBOi) aims to improve the fidelity of tropical stratospheric variability in general circulation and Earth system models by conducting coordinated numerical experiments and analysis. In the equatorial stratosphere, the QBO is the most cons...
Spatiotemporal variations in momentum flux spectra of convective gravity waves (CGWs) at the source level (cloud top), including nonlinear forcing effects, are examined based on calculations using an offline version of CGW parameterization and global reanalysis data for a period of 32 years (1979–2010). The cloud-top momentum flux (CTMF) is not sol...
Vertically propagating low-frequency inertia-gravity waves (IGWs) are retrieved from meteor radar winds observed at King Sejong Station (KSS: 62.22°S, 58.78°W), Antarctica. IGW horizontal winds extracted from temporal band-pass filtering in regular time-height bins show the frequent occurrence of IGWs with the downward phase progression and the cou...
An idealized baroclinic instability case is simulated using
a ∼ 10 km resolution global model to investigate the
characteristics of gravity waves generated in the baroclinic life cycle.
Three groups of gravity waves appear around the high-latitude surface trough
at the mature stage of the baroclinic wave. They have horizontal and vertical
wavelengt...
The momentum forcing of the QBO (quasi-biennial oscillation) by equatorial waves is estimated
using recent reanalyses. Based on the estimation using the
conventional pressure-level data sets, the forcing by the Kelvin
waves (3–9 m s−1 month−1) dominates the net
forcing by all equatorial wave modes (3–11 m s−1 month−1)
in the easterly-to-westerly tr...
For a case study of Typhoon Ewiniar performed with a mesoscale model, we
compare stratospheric gravity wave (GW) momentum flux determined from
temperature variances by applying GW polarization relations and by
assuming upward propagating waves, with GW momentum flux calculated from
model winds which is considered as a reference. The temperature-bas...
Convective gravity wave (GW) sources are spatially localized and emit at
the same time waves with a wide spectrum of phase speeds. Any wave
analysis therefore compromises between spectral and spatial resolution.
Future satellite borne limb imagers will for a first time provide real
3-D volumes of observations. These volumes will be however limited...
The annual cycle of tropical upwelling and contributions by planetary and gravity waves are investigated fromclimatological simulations using theWholeAtmosphere CommunityClimateModel (WACCM) including three gravity wave drag (GWD) parameterizations (orographic, nonstationary background, and convective GWD parameterizations). The tropical upwelling...
The dynamical balances associated with upwelling in the tropical lower stratosphere are investigated based on the two 10-year simulations of the NCAR Whole Atmosphere Community Climate Model (WACCM) with (GWDC simulation) and without (CTL simulation) a ray-based convective gravity-wave drag (GWD) parameterization. The tropical stratospheric upwelli...
Effects of basic-state wind on the secondary waves generated by the breaking of the gravity waves in the mesosphere are investigated based on two-dimensional numerical simulations under three (quiescent, uniform, and sheared) idealized basic-wind profiles. The source of the primary gravity waves is given by a quasi-monochromatic wave oscillator wit...
Gravity waves generated by convective clouds are numerically simulated using a two-dimensional mesoscale model that extends to the upper mesosphere (physical model top of 105 km), and characteristics of the waves are investigated before and after wave breaking occurred in the mesosphere. Gravity waves generated by convective clouds have wide spectr...
Characteristics of inertio-gravity waves (IGWs) observed at six operational rawinsonde stations in Korea from 20 August to 5 September 2002 and their relationship with convective sources are investigated. Several types of convective systems, including mesoscale convective complexes and Typhoon Rusa, passed the Korean peninsula during the observing...
