REanalysis of the TROpospheric chemical composition over the past 40 years (RETRO)��A long-term global modeling study of tropospheric chemistry (original) (raw)

Evaluation of the new UKCA climate-composition model – Part 2: The Troposphere

Geoscientific Model Development, 2014

Atmospheric chemistry, aerosols, and the biosphere are important features of the Earth System (ES). The atmospheric abundance and lifetime of many greenhouse gases, such as methane (CH 4 ) and nitrous oxide (N 2 O), depend on atmospheric chemistry. Likewise, heterogeneous chemistry involving reactive chlorine from chlorofluorocarbons (CFCs) Published by Copernicus Publications on behalf of the European Geosciences Union. Geosci. Model Dev., 7, 41-91, 2014 www.geosci-model-dev.net/7/41/2014/ www.geosci-model-dev.net/7/41/2014/ Geosci. Model Dev., 7, 41-91, 2014 Geosci. Model Dev., 7, 41-91, 2014 www.geosci-model-dev.net/7/41/2014/ F. M. O'Connor et al.: UKCA: the troposphere Geosci. Model Dev., 7, 41-91, 2014 www.geosci-model-dev.net/7/41/2014/ Geosci. Model Dev., 7, 41-91, 2014 www.geosci-model-dev.net/7/41/2014/ www.geosci-model-dev.net/7/41/2014/ Geosci. Model Dev., 7, 41-91, 2014 Geosci. Model Dev., 7, 41-91, 2014 www.geosci-model-dev.net/7/41/2014/ www.geosci-model-dev.net/7/41/2014/ Geosci. Model Dev., 7, 41-91, 2014 Geosci. Model Dev., 7, 41-91, 2014 www.geosci-model-dev.net/7/41/2014/ F. M. O'Connor et al.: UKCA: the troposphere 55 Geosci. Model Dev., 7, 41-91, 2014 www.geosci-model-dev.net/7/41/2014/ Geosci. Model Dev., 7, 41-91, 2014 www.geosci-model-dev.net/7/41/2014/

Genthon_et_al-2001-Journal_of_Geophysical_Research__Atmospheres_(1984-2012).pdf

Atmospheric general circulation models (GCMs) simulate two of the main components of the Antarctic surface mass balance (SMB), precipitation and sublimation, which are generally assumed to dominate the SMB. Resemblances between the Antarctic SMB simulated by seven different GCMs run at high (•100-200 kin) resolution, and differences with a recently produced observation-based map are analyzed. A number of these differences are common to all seven models. They are called systematic model biases and are summarized as a composite of all seven models. It is found unlikely that higher model resolution would significantly affect the systematic biases. All but one of the models studied here use an inaccurate prescribed topography of Antarctica, with errors as large as 1000 m. Although wrong topography does not seem to consistently explain model SMB biases, it is strongly recommended that the Antarctic topography in GCMs be updated. Wind erosion and drifting snow are not simulated in GCMs. Because the processes of wind erosion are complex and nonlinear, evaluation of its possible contribution to systematic model biases is not straightforward. Partial correspondence between regions of strongest winds and model biases suggest that wind erosion may contribute and should be formulated in GCMs. Sublimation is another significant potential negative term in the SMB of Antarctica, but it does not seem to explain any systematic model bias. Finally, it is proposed that some of the systematic differences between models and observation-based maps actually signal errors in the latter rather than in the models. These errors occur in regions devoid of field observation. They may thus be related to the process of interpolation used to build the SMB maps. 20,653

Evaluation of the new UKCA climate-composition model – Part I: The stratosphere

Geoscientific Model Development Discussions, 2008

tese_com_capa_4_final_YC.pdf

GLOBAL AND MID-LATITUDE IMPACT OF TEN YEARS OF SOLAR ACTIVITY USING OBSERVATIONAL DATA OF THE GEOPHYSICAL AND ASTRONOMICAL OBSERVATORY OF THE UNIVERSITY OF COIMBRA, 2018

The focus of this thesis is to identify the role and dynamics of different current systems for storm-time activity at mid-latitude ground level and their relation with other solar, interplanetary and geomagnetic parameters, in the 2007-2016 time interval. For this purpose, I compared the synthetic series of six magnetospheric current systems computed with the data-based semi-empirical model of Tsyganenko and Sitnov 2005 (TS05), with the measurements of four mid-latitude geomagnetic stations at very near geomagnetic latitudes, but well apart in longitude (Coimbra (COI), Portugal; Panagyurishte (PAG), Bulgary; Novosibirsk (NVS), Russia; Boulder (BOU), USA), and with other ground and satellite-based solar, interplanetary and geomagnetic parameters obtained from the OMNI/NASA database. An evaluation of TS05 model is presented, in order to determine the model ability to reproduce both the total magnetospheric transient signal and to explain this signal through the contribution of each TS05 magnetospheric current system at ground level, comparing them with hourly data of the four geomagnetic stations selected. It was found that TS05 model is a useful tool to explain ground-based North-South (or X) component of geomagnetic activity at mid-latitudes, in terms of main current sources. It was verified that TS05 is efficient to reproduce the X component of terrestrial magnetospheric field at mid-latitudes during high geomagnetic activity time, with correlations r ≥ 0.7 in ∼50% of compared data, presenting a lower efficiency during calm time, with correlations r ≥ 0.7 only in ∼30% of data compared. Results are less favourable for the East-West (or Y ) component, probably due to the fact that TS05 model closes Birkeland (or field-aligned, FAC) currents through the Earth’s centre instead of through the ionosphere. It was found that currents that contribute most to the X component during geomagnetic active periods are the cross-tail (TAIL), the symmetric ring (SRC) and the partial ring (PRC) currents. The currents that contribute most to Y component are FAC and PRC currents. For all stations the highest correlations among observations and TS05 simulations are obtained for stronger geomagnetic activity. The results in this study indicate that the implementation of TAIL and SRC currents in TS05 model is more successful than that for the FAC current. The quiet daily (QD) variation has a main contribution from ionospheric currents, which are not considered in TS05 model. For observatories at Northern Hemisphere’s mid-latitudes that are localized close to the ionospheric current vortex center (COI and PAG), it was possible to separate efficiently the QD ionospheric contribution using Principal Component Analysis (PCA). For the other two stations (NVS and BOU) it was found a relatively higher contribution of magnetospheric signal in the QD variation. After removing the QD variation from data, COI and PAG are better correlated with TS05 series than BOU and NVS. However, BOU and NVS are better correlated with geomagnetic indices Dst (disturbance storm-time) and RC (ring current), with RC showing a slightly less good performance with respect to Dst. Correlations between 33 solar, interplanetary magnetic field (IMF) and geomagnetic activity proxies were analysed for the 2009-2016 time interval. It was found that series of 27-day averages (Bartels’ rotation) give higher correlations than daily or annual series. Parameters that show higher cross-correlations among different groups are the Sun’s northern and southern facular areas (FA-N and FA-S), two geomagnetic indices derived from TS05 model (T-SRC and T-PRC), the total IMF intensity (B), the percentage of IMF southward component (BZS GSM) and the interplanetary coupling Newell’s function. We propose that these parameters are the best candidates to use if we want to relate meaningfully the solar surface events to geomagnetic activity felt on the Earth’s surface. Two new proxies were tested, 1) TI-indices, calculated from the X TS05-derived series of TAIL, SRC, PRC and FAC contributions for the four observatories and 2) BZS GSM, calculated as the daily percentage of IMF southward component along the GSM Z-axis. Helio-magnetic asymmetries were calculated for the 33 parameters, as the difference between their averaged values in the towards and away magnetic sectors of the interplanetary medium. Improvement in 27-day correlations with respect to annual correlations is the result of an annual oscillation in this asymmetry, which is present in most studied proxies and is probably due to the Russell-McPherron effect. Due to this effect, BZS GSM and BZ GSM have a well-defined annual modulation, and geomagnetic activity indices (GAI) also have annual oscillation and good correlations with BZS GSM and BZ GSM. TI-indices have annual oscillation at declining phase of the cycle, but insignificant oscillation near the minimum. Major percentage of towards days in negative polarity epoch and of away days in positive polarity epoch means that the Earth has been mostly at the northern magnetic hemisphere during the solar cycle 24. In conclusion, the main part of this Ph.D. thesis was dedicated to the design and implementation of a statistical approach that was applied to test the performance of the TS05 model in explaining geomagnetic activity observed at Earth’s Northern Hemisphere mid-latitudes. This approach can be applied to test any other magnetospheric model. At the end of this work, a prospective study was made using different proxies that describe the Sun surface, the interplanetary medium and geomagnetic activity, to identify those parameters that should be more meaningfully used to relate the Sun to the geomagnetic activity observed on Earth. Keywords: Sun-Earth interaction, solar activity, solar and geomagnetic data, space weather.

REanalysis of the TROpospheric chemical composition over the past 40 years (RETRO)���A long-term global modeling study of tropospheric chemistry (original) (raw)

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REanalysis of the TROpospheric chemical composition over the past 40 years (RETRO)��A long-term global modeling study of tropospheric chemistry (original) (raw)