DSpace community: 全球大氣觀測與資料應用研究中心

Two overlooked biases of the advanced research wrf (arw) model in geopotential height and temperature

title: Two overlooked biases of the advanced research wrf (arw) model in geopotential height and temperature abstract: 摘要： The authors have discovered two sizeable biases in the Weather Research and Forecasting (WRF) model: a negative bias in geopotential and a warm bias in temperature, appearing both in the initial condition and the forecast. The biases increase with height and thus manifest themselves at the upper part of the model domain. Both biases stem from a common root, which is that vertical structures of specific volume and potential temperature are convex functions. The geopotential bias is caused by the particular discrete hydrostatic equation used in WRF and is proportional to the square of the thickness of model layers. For the vertical levels used in this study, the bias far exceeds the gross 1-day forecast bias combining all other sources. The bias is fixed by revising the discrete hydrostatic equation. WRF interpolates potential temperature from the grids of an external dataset to the WRF grids in generating the initial condition. Associated with the Exner function, this leads to the marked bias in temperature. By interpolating temperature to the WRF grids and then computing potential temperature, the bias is removed. The bias corrections developed in this study are expected to reduce the disparity between the forecast and observations, and eventually to improve the quality of analysis and forecast in the subsequent data assimilation. The bias corrections might be especially beneficial to assimilating height-based observations (e.g., radio occultation data). 出版者： Boston, MA: American Meteorological Society 出版日期： 2012-12-01 出處： Monthly weather review, 2012-12, Vol.140 (12), p.3907-3918 資源來源： EBSCOhost OmniFile Full Text Select 版權： 2014 INIST-CNRS 版權： Copyright American Meteorological Society Dec 2012 識別號： ISSN: 0027-0644 識別號： EISSN: 1520-0493 識別號： DOI: 10.1175/MWR-D-12-00045.1 識別號： CODEN: MWREAB

Traveling magnetopause distortion related to a large-scale magnetosheath plasma jet: THEMIS and ground-based observations

title: Traveling magnetopause distortion related to a large-scale magnetosheath plasma jet: THEMIS and ground-based observations abstract: 摘要： Here, we present a case study of THEMIS and ground‐based observations of the perturbed dayside magnetopause and the geomagnetic field in relation to the interaction of an interplanetary directional discontinuity (DD) with the magnetosphere on 16 June 2007. The interaction resulted in a large‐scale local magnetopause distortion of an “expansion – compression – expansion” (ECE) sequence that lasted for ∼15 min. The compression was caused by a very dense, cold, and fast high‐βmagnetosheath plasma flow, a so‐called plasma jet, whose kinetic energy was approximately three times higher than the energy of the incident solar wind. The plasma jet resulted in the effective penetration of magnetosheath plasma inside the magnetosphere. A strong distortion of the Chapman‐Ferraro current in the ECE sequence generated a tripolar magnetic pulse “decrease – peak– decrease” (DPD) that was observed at low and middle latitudes by some ground‐based magnetometers of the INTERMAGNET network. The characteristics of the ECE sequence and the spatial‐temporal dynamics of the DPD pulse were found to be very different from any reported patterns of DD interactions with the magnetosphere. The observed features only partially resembled structures such as FTE, hot flow anomalies, and transient density events. Thus, it is difficult to explain them in the context of existing models. Key Points A magnetosheath jet causes a strong distortion of the dayside magnetopause The jet results in intense plasma penetration inside the magnetosphere Ground magnetic variations trace the jet traveling along the magnetopause 其他題名： J. Geophys. Res 出版者： Washington, DC: Blackwell Publishing Ltd 出版日期： 2012-08 出處： Journal of Geophysical Research: Space Physics, 2012-08, Vol.117 (A8), p.n/a 資源來源： Wiley Online Library 版權： 2012. American Geophysical Union. All Rights Reserved. 版權： 2015 INIST-CNRS 版權： Copyright American Geophysical Union 2012 識別號： ISSN: 0148-0227 識別號： ISSN: 2169-9380 識別號： EISSN: 2156-2202 識別號： EISSN: 2169-9402 識別號： DOI: 10.1029/2011JA016861

The shape of strongly disturbed dayside magnetopause

title: The shape of strongly disturbed dayside magnetopause abstract: 摘要： During strong geomagnetic disturbances, the Earth's magnetosphere exhibits unusual and nonlinear interaction with the incident flow of magnetized solar wind plasma. Global Magneto-hydro-dynamic (MHD) modeling of the magnetosphere predicts that the storm-time effects at the magnetopause result from the abnormal plasma transport and/or extremely strong field aligned currents. In-situ observations of the magnetospheric boundary, magnetopause, by Geosynchronous Operational Environmental Satellite (GOES) allowed us to find experimentally such effects as a saturation of the dayside reconnection, unusual bluntness and prominent duskward skewing of the nose magnetopause. The saturation and duskward skewing were attributed to the storm-time magnetopause formation under strong southward interplanetary magnetic field (IMF). The unusual bluntness was observed during both high solar wind pressure and strong southward IMF. We suggest that these phenomena are caused by a substantial contribution of the cross-tail current magnetic field and the hot magnetospheric plasma from the asymmetrical ring current into the pressure balance at the dayside magnetopause. 出版者： Taiwan: 中華民國地球科學學會出版日期： 2013-04-01 出處： TAO : Terrestrial, atmospheric, and oceanic sciences, 2013-04, Vol.24 (2), p.225-232 資源來源：華藝CEPS中文電子期刊服務版權： 2013. This work is licensed under https://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License. 識別號： ISSN: 1017-0839 識別號： ISSN: 2223-8964 識別號： ISSN: 2311-7680 識別號： EISSN: 2311-7680 識別號： DOI: 10.3319/TAO.2012.09.26.02(SEC)

TEC evidence for near-equatorial energy deposition by 30 keV electrons in the topside ionosphere

title: TEC evidence for near-equatorial energy deposition by 30 keV electrons in the topside ionosphere abstract: 摘要： Observations of energetic electrons (10 – 300 keV) by NOAA/POES and DMSP satellites at heights <1000 km during the period from 1999 to 2010 allowed finding abnormal intense fluxes of ~106 – 107 cm−2 s−1 sr−1 for quasi‐trapped electrons appearing within the forbidden zone of low latitudes over the African, Indo‐China, and Pacific regions. Extreme fluxes appeared often in the early morning and persisted for several hours during the maximum and recovery phase of geomagnetic storms. We analyzed nine storm time events when extreme electron fluxes first appeared in the Eastern Hemisphere, then drifted further eastward toward the South‐Atlantic Anomaly. Using the electron spectra, we estimated the possible ionization effect produced by quasi‐trapped electrons in the topside ionosphere. The estimated ionization was found to be large enough to satisfy observed storm time increases in the ionospheric total electron content (TEC) determined for the same spatial and temporal ranges from global ionospheric maps. Additionally, extreme fluxes of quasi‐trapped electrons were accompanied by the significant elevation of the low‐latitude F‐layer obtained from COSMIC/FORMOSAT‐3 radio occultation measurements. We suggest that the storm time ExB drift of energetic electrons from the inner radiation belt is an important driver of positive ionospheric storms within low‐latitude and equatorial regions. Key Points Ionospheric ionization and energetic electrons were studied at low latitudes Positive ionospheric storms correlate well with electron enhancements ExB electron drift results in additional ionization of the ionosphere 其他題名： J. Geophys. Res. Space Physics 出版者： Washington: Blackwell Publishing Ltd 出版日期： 2013-07 出處： Journal of geophysical research : Space physics (2013 - Present), 2013-07, Vol.118 (7), p.4672-4695 資源來源： Wiley Online Library - AutoHoldings Journals 版權： 2013. American Geophysical Union. All Rights Reserved. 識別號： ISSN: 2169-9380 識別號： EISSN: 2169-9402 識別號： DOI: 10.1002/jgra.50439