On the detection of a high-altitude peak of atmospheric ozone by the NOMAD/UVIS onboard the ExoMars TGO

The Nadir and Occultation for MArs Discovery (NOMAD) is a spectrometer suite onboard the ExoMars Trace Gas Orbiter (TGO), providing observations in the nadir, limb, and solar occultation modes since April 2018. UVIS, a single spectrometer unit within NOMAD spans the ultraviolet-visible range between 200 nm and 650 nm. It obtained ~ 4000 vertically resolved (< 1 km) solar occultation observations of the martian atmosphere for over a full Mars year (MY, 687 days) starting at MY 34 during late northern summer at Ls = 163&#176;. Ozone (O3), a principal component of the martian atmosphere, is highly responsive to the incoming UV flux, and is a sensitive tracer of the odd hydrogen chemistry. Transmittance spectra returned by UVIS sampled the O3 Hartley band around 250 nm and provided unique insights into understanding the vertical, latitudinal and temporal behavior of O3. UVIS detected a high-altitude peak of O3 between 40 and 60 km that is mostly persistent between Ls = 340&#176; and ~ 200&#176; at polar latitudes, and is found to be highly dependent on latitude and season. We will present high-resolution results tracking the vertical, latitudinal, diurnal and seasonal evolution of the secondary peak of ozone for a full Mars year. In comparison, we will also provide O3 simulations from the GEM-Mars General Circulation Model (GCM) with the purpose of shedding light into understanding the photochemical processes that lead to the presence and disappearance of the high-altitude peak of atmospheric ozone.&#160;

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Pemanfaatan CFSRv2 untuk Statistical Downscaling menggunakan Principal Component Regression dan Partial Least Square

Xplore Journal of Statistics ◽

10.29244/xplore.v8i1.275 ◽

2019 ◽

Vol 8 (1) ◽

Author(s):

Khairunnisa Khairunnisa ◽

Rizka Pitri ◽

Victor P Butar-Butar ◽

Agus M Soleh

Keyword(s):

Statistical Downscaling ◽

General Circulation ◽

Principal Component Regression ◽

Circulation Model ◽

Principal Component ◽

Meteorological Station ◽

Grid Size ◽

Partial Least Square ◽

Least Square ◽

Output Data

This research used CFSRv2 data as output data general circulation model. CFSRv2 involves some variables data with high correlation, so in this research is using principal component regression (PCR) and partial least square (PLS) to solve the multicollinearity occurring in CFSRv2 data. This research aims to determine the best model between PCR and PLS to estimate rainfall at Bandung geophysical station, Bogor climatology station, Citeko meteorological station, and Jatiwangi meteorological station by comparing RMSEP value and correlation value. Size used was 3×3, 4×4, 5×5, 6×6, 7×7, 8×8, 9×9, and 11×11 that was located between (-40) N - (-90) S and 1050 E -1100 E with a grid size of 0.5×0.5 The PLS model was the best model used in stastistical downscaling in this research than PCR model because of the PLS model obtained the lower RMSEP value and the higher correlation value. The best domain and RMSEP value for Bandung geophysical station, Bogor climatology station, Citeko meteorological station, and Jatiwangi meteorological station is 9 × 9 with 100.06, 6 × 6 with 194.3, 8 × 8 with 117.6, and 6 × 6 with 108.2, respectively.

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Influence of gravity waves on the climatology of high-altitude Martian carbon dioxide ice clouds

10.5194/angeo-2018-61 ◽

2018 ◽

Author(s):

Erdal Yiğit ◽

Alexander S. Medvedev ◽

Paul Hartogh

Keyword(s):

Carbon Dioxide ◽

High Altitude ◽

Gravity Waves ◽

General Circulation ◽

Middle Atmosphere ◽

Circulation Model ◽

Upper Atmosphere ◽

Cloud Formation ◽

Ice Clouds ◽

Ice Cloud

Abstract. Carbon dioxide (CO2) ice clouds have been routinely observed in the middle atmosphere of Mars. However, there are still uncertainties concerning physical mechanisms that control their altitude, geographical, and seasonal distributions. Using the Max Planck Institute Martian General Circulation Model (MPI-MGCM), incorporating a state-of-the-art whole atmosphere subgrid-scale gravity wave parameterization (Yiğit et al., 2008), we demonstrate that internal gravity waves generated by lower atmospheric weather processes have wide reaching impact on the Martian climate. Globally, GWs cool the upper atmosphere of Mars by ~10 % and facilitate high-altitude CO2 ice cloud formation. CO2 ice cloud seasonal variations in the mesosphere and the mesopause region appreciably coincide with the spatio-temporal variations of GW effects, providing insight into the observed distribution of clouds. Our results suggest that GW propagation and dissipation constitute a necessary physical mechanism for CO2 ice cloud formation in the Martian upper atmosphere during all seasons.

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On the relative roles of dynamics and chemistry governing the abundance and diurnal variation of low latitude thermospheric nitric oxide

10.5194/angeo-2018-112 ◽

2018 ◽

Author(s):

David E. Siskind ◽

McArthur Jones Jr. ◽

Douglas P. Drob ◽

John P. McCormack ◽

Mark E. Hervig ◽

...

Keyword(s):

Nitric Oxide ◽

Diurnal Variation ◽

Empirical Model ◽

General Circulation ◽

Lower Boundary ◽

Circulation Model ◽

Potential Conflict ◽

Solar Occultation ◽

Free Running ◽

Data Discrepancy

Abstract. We use data from two NASA satellites, the Thermosphere Ionosphere Energetics and Dynamics (TIMED) and the Aeronomy of Ice in the Mesosphere (AIM) satellites in conjunction with model simulations from the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) to elucidate the key dynamical and chemical factors governing the abundance and diurnal variation of nitric oxide (NO) at near solar minimum conditions and low latitudes. This analysis was enabled by the recent orbital precession of the AIM satellite which caused the solar occultation pattern measured by the Solar Occultation for Ice Experiment (SOFIE) to migrate down to low and mid latitudes for specific periods of time. We use a month of NO data collected in January 2017 to compare with two versions of the TIME-GCM, one driven solely by climatological tides and analysis-derived planetary waves at the lower boundary and free running at all other altitudes, while the other is constrained by a high-altitude analysis from the Navy Global Environmental Model (NAVGEM) up to the mesopause. We also compare SOFIE data with a NO climatology from the Nitric Oxide Empirical Model (NOEM). Both SOFIE and NOEM yield peak NO abundances of around 4 × 107 cm−3; however, the SOFIE profile peaks about 6–8 km lower than NOEM. We show that this difference is likely a local time effect; SOFIE being a dawn measurement and NOEM representing late morning/near noon. The constrained version of TIME-GCM exhibits a low altitude dawn peak while the model that is forced solely at the lower boundary and free running above does not. We attribute this difference due to a phase change in the semi-diurnal tide in the NAVGEM-constrained model causing descent of high NO mixing ratio air near dawn. This phase difference between the two models arises due to differences in the mesospheric zonal mean zonal winds. Regarding the absolute NO abundance, all versions of the TIME-GCM overestimate this. Tuning the model to yield calculated atomic oxygen in agreement with TIMED data helps, but is insufficient. Further, the TIME-GCM underestimates the electron density [e-] as compared with the International Reference Ionosphere empirical model. This suggests a potential conflict with the requirements of NO modeling and [e-] modeling since one solution typically used to increase model [e-] is to increase the solar soft X ray flux which would, in this case, worsen the NO model/data discrepancy.

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A global view of gravity waves in the Martian atmosphere inferred from a high-resolution general circulation model

Geophysical Research Letters ◽

10.1002/2015gl066332 ◽

2015 ◽

Vol 42 (21) ◽

pp. 9213-9222 ◽

Cited By ~ 16

Author(s):

Takeshi Kuroda ◽

Alexander S. Medvedev ◽

Erdal Yiğit ◽

Paul Hartogh

Keyword(s):

High Resolution ◽

General Circulation Model ◽

Gravity Waves ◽

General Circulation ◽

Circulation Model ◽

Martian Atmosphere ◽

Global View

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Vertical distribution of dust in the Martian atmosphere during northern spring and summer: High-altitude tropical dust maximum at northern summer solstice

Journal of Geophysical Research Atmospheres ◽

10.1029/2010je003692 ◽

2011 ◽

Vol 116 (E1) ◽

Cited By ~ 33

Author(s):

N. G. Heavens ◽

M. I. Richardson ◽

A. Kleinböhl ◽

D. M. Kass ◽

D. J. McCleese ◽

...

Keyword(s):

Vertical Distribution ◽

High Altitude ◽

Martian Atmosphere ◽

Summer Solstice ◽

Northern Summer

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Spatial and temporal variation of total electron content as revealed by principal component analysis

Annales Geophysicae ◽

10.5194/angeo-34-1109-2016 ◽

2016 ◽

Vol 34 (12) ◽

pp. 1109-1117 ◽

Cited By ~ 5

Author(s):

Elsayed R. Talaat ◽

Xun Zhu

Keyword(s):

Principal Component Analysis ◽

Total Electron Content ◽

General Circulation ◽

Circulation Model ◽

Principal Component ◽

Component Analysis ◽

Total Variance ◽

Spatial And Temporal Variation ◽

Electron Content ◽

Total Electron

Abstract. Eleven years of global total electron content (TEC) data derived from the assimilated thermosphere–ionosphere electrodynamics general circulation model are analyzed using empirical orthogonal function (EOF) decomposition and the corresponding principal component analysis (PCA) technique. For the daily averaged TEC field, the first EOF explains more than 89 % and the first four EOFs explain more than 98 % of the total variance of the TEC field, indicating an effective data compression and clear separation of different physical processes. The effectiveness of the PCA technique for TEC is nearly insensitive to the horizontal resolution and the length of the data records. When the PCA is applied to global TEC including local-time variations, the rich spatial and temporal variations of field can be represented by the first three EOFs that explain 88 % of the total variance. The spectral analysis of the time series of the EOF coefficients reveals how different mechanisms such as solar flux variation, change in the orbital declination, nonlinear mode coupling and geomagnetic activity are separated and expressed in different EOFs. This work demonstrates the usefulness of using the PCA technique to assimilate and monitor the global TEC field.

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Identification of dominant sources of sea level pressure for precipitation forecasting over Wales

Journal of Hydroinformatics ◽

10.2166/hydro.2012.110 ◽

2012 ◽

Vol 15 (3) ◽

pp. 1002-1021 ◽

Cited By ~ 6

Author(s):

Azadeh Ahmadi ◽

Dawei Han

Keyword(s):

General Circulation ◽

Large Scale ◽

Circulation Model ◽

Principal Component ◽

Support Vector ◽

Monthly Precipitation ◽

Climate Variables ◽

Forward Selection ◽

Precipitation Forecasting ◽

Variable Combination

Downscaling methods are utilized to assess the effects of large scale atmospheric circulation on local hydrological variables such as precipitation and runoff. In this paper, a methodology of statistical downscaling using a support vector machine (SVM) approach is presented to simulate and predict the precipitation using general circulation model (GCM) data. Due to the complexity and issues related to finding a relationship between the large scale climatic parameters and local precipitation, the climate variables (predictors) affecting monthly precipitation variations over Wales are identified using a combination of the methods including the principal component analysis (PCA), fuzzy clustering, backward selection, forward selection, and Gamma test (GT). The effectiveness of those tools is illustrated through their implementations in the case study. It has been found that although the GT itself fails to identify the best input variable combination, it provides useful and narrowed-down options for further exploration. The best input variable combination is achieved by the GT and forward selection method. This approach can be a useful way for assessing the impacts of climate variables on precipitation forecasting.

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Forced Atmospheric Teleconnections during 1979–2014

Journal of Climate ◽

10.1175/jcli-d-15-0226.1 ◽

2016 ◽

Vol 29 (7) ◽

pp. 2333-2357 ◽

Cited By ~ 8

Author(s):

Tao Zhang ◽

Martin P. Hoerling ◽

Judith Perlwitz ◽

Taiyi Xu

Keyword(s):

Northern Hemisphere ◽

Radiative Forcing ◽

General Circulation ◽

Decadal Variability ◽

Southern Oscillation ◽

Wave Train ◽

Circulation Model ◽

Principal Component ◽

Internal Variability ◽

Atmospheric Teleconnections

Abstract Forced atmospheric teleconnections during 1979–2014 are examined using a 50-member ensemble of atmospheric general circulation model (AGCM) simulations subjected to observed variations in sea surface temperatures (SSTs), sea ice, and carbon dioxide. Three primary modes of forced variability are identified using empirical orthogonal function (EOF) analysis of the ensemble mean wintertime extratropical Northern Hemisphere 500-hPa heights. The principal component time series of the first and second modes are highly correlated with Niño-3.4 and trans-Niño (TNI) SST indices, respectively, indicating mostly tropical sources. Their impacts are largely confined to the Pacific–North American (PNA) sector. The leading mode describes the canonical atmospheric teleconnection associated with El Niño–Southern Oscillation (ENSO) resembling the tropical/Northern Hemisphere pattern. The second mode describes a wave train resembling the classic PNA pattern resulting from atmospheric sensitivity to ENSO asymmetry and from sensitivity to a tropical precursor SST for ENSO development. The third mode is characterized by a hemisphere-scale increasing trend in heights. Based on a comparison with 50-member coupled ocean–atmosphere model simulations, it is argued that this mode is strongly related to radiatively forced climate change, while the other two forced teleconnections are principally related to internal coupled variability. A trend in the leading forced mode is related to ENSO-like decadal variability and dominates the overall observed 500-hPa height trend since 1979. These model results indicate that the trend in the first mode is due to internal variability rather than external radiative forcing.

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