An evaluation of a general circulation model (GCM) and the NCEP–NCAR reanalysis data for winter precipitation in Greece

2006 ◽  
Vol 26 (7) ◽  
pp. 935-955 ◽  
Author(s):  
K. Tolika ◽  
P. Maheras ◽  
H. A. Flocas ◽  
A. Arseni-Papadimitriou
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Winter Precipitation ◽  
Reanalysis Data

Statistical downscaling of general circulation model outputs to precipitation, evaporation and temperature using a key station approach

2016 ◽  
Vol 7 (4) ◽  
pp. 683-707
Author(s):  
D. A. Sachindra ◽  
F. Huang ◽  
A. Barton ◽  
B. J. C. Perera
Keyword(s):  
General Circulation Model ◽  
Statistical Downscaling ◽  
General Circulation ◽  
Emission Scenario ◽  
Circulation Model ◽  
Reanalysis Data ◽  
Maximum Temperature ◽  
Monthly Precipitation ◽  
Regression Equations ◽  
Highly Correlated

Using a key station approach, statistical downscaling of monthly general circulation model outputs to monthly precipitation, evaporation, minimum temperature and maximum temperature at 17 observation stations located in Victoria, Australia was performed. Using the observations of each predictand, over the period 1950–2010, correlations among all stations were computed. For each predictand, the station which showed the highest number of correlations above 0.80 with other stations was selected as the first key station. The stations that were highly correlated with that key station were considered as the member stations of the first cluster. By employing this same procedure on the remaining stations, the next key station was found. This procedure was performed until all stations were segregated into clusters. Thereafter, using the observations of each predictand, regression equations (inter-station regression relationships) were developed between the key stations and the member stations for each calendar month. The downscaling models at the key stations were developed using reanalysis data as inputs to them. The outputs of HadCM3 pertaining to A2 emission scenario were introduced to these downscaling models to produce projections of the predictands over the period 2000–2099. Then the outputs of these downscaling models were introduced to the inter-station regression relationships to produce projections of predictands at all member stations.

scholarly journals Technical Note: Description and assessment of a nudged version of the new dynamics Unified Model

2007 ◽  
Vol 7 (6) ◽  
pp. 17261-17297 ◽  
Author(s):  
P. J. Telford ◽  
P. Braesicke ◽  
O. Morgenstern ◽  
J. A. Pyle
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Circulation Model ◽  
Reanalysis Data ◽  
Technical Note ◽  
Unified Model ◽  
Quantitative Assessments

Abstract. We present a "nudged" version of the Met Office general circulation model, the Unified Model. We constrain this global climate model using ERA-40 reanalysis data with the aim of reproducing the observed "weather" over a year from September 1999. Quantitative assessments are made of its performance, focussing on dynamical aspects of nudging and demonstrating that the "weather" is well simulated.

scholarly journals A study of the dynamical characteristics of inertia–gravity waves in the Antarctic mesosphere combining the PANSY radar and a non-hydrostatic general circulation model

2018 ◽  
Author(s):  
Ryosuke Shibuya ◽  
Kaoru Sato
Keyword(s):  
General Circulation Model ◽  
Gravity Waves ◽  
General Circulation ◽  
Initial Conditions ◽  
Circulation Model ◽  
Reanalysis Data ◽  
Wind Fields ◽  
High Latitude Region ◽  
The Antarctic ◽  
Inertia Gravity Waves

Abstract. The first long-term simulation using the high-top non-hydrostatic general circulation model (NICAM) was executed to analyze mesospheric gravity waves in the period from April to August in 2016. Successive runs lasting 7 days are performed using initial conditions from the MERRA reanalysis data with an overlap of 2 days between consecutive runs. The data for the analyses were compiled from the last 5 days of each run. The simulated wind fields were closely compared to the MERRA reanalysis data and to the observational data collected by a complete PANSY (Program of the Antarctic Syowa MST/IS Radar) radar system installed at Syowa Station (39.6° E 69.0° S). It is shown that the NICAM mesospheric wind fields are realistic, even though the amplitudes of the wind disturbances appear to be larger than the radar observations. The power spectrum of the meridional wind fluctuations at a height of 70 km has an isolated and broad peak at frequencies slightly lower than the inertial frequency, f, for latitudes from 30° S to 75° S, while another isolated peak is observed at frequencies of approximately 2π/8 h at latitudes from 78° S to 90° S. The spectrum of the vertical fluxes of the zonal momentum also has an isolated peak at frequencies slightly lower than f at latitudes from 30° S to 75° S at a height of 70 km. It is shown that these isolated peaks are primarily composed of gravity waves with horizontal wavelengths of more than 1000 km. The latitude–height structure of the momentum fluxes indicates that the isolated peaks at frequencies slightly lower than f originate from two branches of gravity wave propagation paths. It is thought that one branch originates from 75° S due to topographic gravity waves generated over the Antarctic Peninsula and its coast, while more than 80 % of the other branch originates from 45° S and includes contributions by non-orographic gravity waves. The existence of isolated peaks in the high-latitude region in the mesosphere is likely explained by the poleward propagation of quasi-inertia–gravity waves and by the accumulation of wave energies near the inertial frequency at each latitude.

scholarly journals Tropical Pacific Decadal Variability and the Subtropical–Tropical Cells

2005 ◽  
Vol 18 (23) ◽  
pp. 5163-5178 ◽  
Author(s):  
Katja Lohmann ◽  
Mojib Latif
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Decadal Variability ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Reanalysis Data ◽  
Tropical Pacific ◽  
Pacific Decadal Variability ◽  
Decadal Scale ◽  
Decadal Mode

Abstract The decadal-scale variability in the tropical Pacific has been analyzed herein by means of observations and numerical model simulations. The two leading modes of the sea surface temperature (SST) variability in the central western Pacific are a decadal mode with a period of about 10 yr and the ENSO mode with a dominant period of about 4 yr. The SST anomaly pattern of the decadal mode is ENSO like. The decadal mode, however, explains most variance in the western equatorial Pacific and off the equator. A simulation with an ocean general circulation model (OGCM) forced by reanalysis data is used to explore the origin of the decadal mode. It is found that the variability of the shallow subtropical–tropical overturning cells is an important factor in driving the decadal mode. This is supported by results from a multicentury integration with a coupled ocean–atmosphere general circulation model (CGCM) that realistically simulates tropical Pacific decadal variability. Finally, the sensitivity of the shallow subtropical–tropical overturning cells to greenhouse warming is discussed by analyzing the results of a scenario integration with the same CGCM.

scholarly journals Climatology of Borneo Vortices in the HadGEM3-GC31 General Circulation Model

2021 ◽  
pp. 1-61
Author(s):  
Ju Liang ◽  
Jennifer L. Catto ◽  
Matthew Hawcroft ◽  
Kevin I. Hodges ◽  
Mouleong Tan ◽  
...  
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Deep Convection ◽  
Circulation Model ◽  
Winter Precipitation ◽  
Reanalysis Data ◽  
Horizontal Resolution ◽  
Hadley Centre

AbstractBorneo Vortices (BVs) are intense precipitating winter storms that develop over the equatorial South China Sea and strongly affect the weather and climate over the western Maritime Continent due to their association with deep convection and heavy rainfall. In this study, the ability of the HadGEM3-GC31 (Hadley Centre Global Environment Model 3 - Global Coupled vn. 3.1) global climate model to simulate the climatology of BVs at different horizontal resolutions are examined using an objective feature tracking algorithm. The HadGEM3-GC31 at the N512 ( 25 km) horizontal resolution simulates BVs with well-represented characteristics, including their frequency, spatial distribution and their lower-tropospheric structures when compared with BVs identified in a climate reanalysis, whereas the BVs in the N96 (∼135 km) and N216 (∼65 km) simulations are much weaker and less frequent. Also, the N512 simulation better captures the contribution of BVs to the winter precipitation in Borneo and Malay Peninsula compared with precipitation from a reanalysis data and from observations, while the N96 and N216 simulations underestimate this contribution due to the overly weak low-level convergence of the simulated BVs. The N512 simulation also exhibits an improved ability to reproduce the modulation of BV activity by the occurrence of northeasterly cold surges and active phases of Madden-Julian Oscillation in the region, including increased BV track densities, intensities and lifetimes. A sufficiently high model resolution is thus found to be important to realistically simulate the present-climate precipitation extremes associated with BVs and to study their possible changes in a warmer climate.

scholarly journals A study of the dynamical characteristics of inertia–gravity waves in the Antarctic mesosphere combining the PANSY radar and a non-hydrostatic general circulation model

2019 ◽  
Vol 19 (5) ◽  
pp. 3395-3415 ◽  
Author(s):  
Ryosuke Shibuya ◽  
Kaoru Sato
Keyword(s):  
General Circulation Model ◽  
Gravity Waves ◽  
General Circulation ◽  
Circulation Model ◽  
Reanalysis Data ◽  
Wind Fields ◽  
Dynamical Characteristics ◽  
High Latitude Region ◽  
The Antarctic ◽  
Inertia Gravity Waves

Abstract. This study aims to examine the dynamical characteristics of gravity waves with relatively low frequency in the Antarctic mesosphere via the first long-term simulation using a high-top high-resolution non-hydrostatic general circulation model (NICAM). Successive runs lasting 7 days are performed using initial conditions from the MERRA reanalysis data with an overlap of 2 days between consecutive runs in the period from April to August in 2016. The data for the analyses were compiled from the last 5 days of each run. The simulated wind fields were closely compared to the MERRA reanalysis data and to the observational data collected by a complete PANSY (Program of the Antarctic Syowa MST/IS radar) radar system installed at Syowa Station (39.6∘ E, 69.0∘ S). It is shown that the NICAM mesospheric wind fields are realistic, even though the amplitudes of the wind disturbances appear to be larger than those from the radar observations. The power spectrum of the meridional wind fluctuations at a height of 70 km has an isolated and broad peak at frequencies slightly lower than the inertial frequency, f, for latitudes from 30 to 75∘ S, while another isolated peak is observed at frequencies of approximately 2π∕8 h at latitudes from 78 to 90∘ S. The spectrum of the vertical fluxes of the zonal momentum also has an isolated peak at frequencies slightly lower than f at latitudes from 30 to 75∘ S at a height of 70 km. It is shown that these isolated peaks are primarily composed of gravity waves with horizontal wavelengths of more than 1000 km. The latitude–height structure of the momentum fluxes indicates that the isolated peaks at frequencies slightly lower than f originate from two branches of gravity wave propagation paths. It is thought that one branch originates from 75∘ S due to topographic gravity waves generated over the Antarctic Peninsula and its coast, while more than 80 % of the other branch originates from 45∘ S and includes contributions by non-orographic gravity waves. The existence of isolated peaks in the high-latitude region in the mesosphere is likely explained by the poleward propagation of quasi-inertia–gravity waves and by the accumulation of wave energies near the inertial frequency at each latitude.

Can we improve gravity wave parameterizations by imposing sources at all altitudes in the atmosphere?

2020 ◽  
Author(s):  
Bruno Ribstein ◽  
Christophe Millet ◽  
Francois Lott ◽  
Alvaro de la Camara
Keyword(s):  
Gravity Wave ◽  
General Circulation Model ◽  
General Circulation ◽  
Middle Atmosphere ◽  
Phase Speed ◽  
Circulation Model ◽  
Reanalysis Data ◽  
Inertial Waves ◽  
Vertical Propagation

<p>A multiwave non-orographic gravity wave (GW) scheme is adapted to represent waves of small intrinsic phase speed and sources located at all altitudes in the troposphere and middle atmosphere. Using reanalysis data, these changes impose larger amplitude saturated waves everywhere in the middle atmosphere, which permits to produce more realistic GW vertical spectra than when the phase speeds are large and the sources are in the troposphere only. The same scheme, tested online in the Laboratoire de Météorologie Dynamique Zoom(LMDz) general circulation model, performs at least as well as the operational non-orographic GW scheme.  Some modest benefits are seen, for instance, in the equatorial tilt with altitude of the winter jets in the middle atmosphere. Although the scheme includes the effects of inertial waves, which are more and more often detected in the mesosphere, the configuration that gives a reasonable climatology in LMDz hinders the vertical propagation of these parameterized waves and do not generally reach mesospheric altitudes.</p>

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