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Typhoon-induced magnetic disturbances: Cases in the western Pacific

title: Typhoon-induced magnetic disturbances: Cases in the western Pacific abstract: 摘要： Three typhoons occurred over the western Pacific in September 2008 and were enhanced beyond category 3 as they approached Taiwan. The geomagnetic total intensity field recorded at 2 local monitoring stations in Taiwan and 1 remote station in Japan was utilized to examine the magnetic disturbances induced by these typhoons. Analytical results show that amplitude changes in the frequency domain, which are retrieved from the total intensity data via the Fourier transform, at the monitoring and remote stations were consistent, even though magnetic storms strongly affected the magnetic field. However, obvious discrepancies were repeatedly found in the amplitudes in the frequency band between 0.0025 - 0.007 Hz, when typhoons of category > 3 were the closest to the monitoring stations. The frequency band is different from the induction fields from either oceanic storm waves or swells, and is consistent with that of magnetic pulsations triggered by acoustic waves from upward air motion during typhoons. 出版者： Taiwan: 中華民國地球科學學會出版日期： 2014-10-01 出處： TAO : Terrestrial, atmospheric, and oceanic sciences, 2014-10, Vol.25 (5), p.647-653 資源來源： CEPS中文電子期刊版權： 2014. 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.2014.05.08.01(AA)

Transient climate response in coupled atmospheric-ocean general circulation models

title: Transient climate response in coupled atmospheric-ocean general circulation models abstract: 摘要： The equilibrium climate sensitivity (ECS) has a large uncertainty range among models participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) and has recently been presented as “inherently unpredictable.” One way to circumvent this problem is to consider the transient climate response (TCR). However, the TCR among AR4 models also differs by more than a factor of 2. The authors argue that the situation may not necessarily be so pessimistic, because much of the intermodel difference may be due to the fact that the models were run with their oceans at various stages of flux adjustment with their atmosphere. This is shown by comparing multimillennium-long runs of the Goddard Institute for Space Studies model, version E, coupled with the Hybrid Coordinate Ocean Model (GISS-EH) and the Community Climate System Model, version 4 (CCSM4) with what were reported to AR4. The long model runs here reveal the range of variability (~30%) in their TCR within the same model with the same ECS. The commonly adopted remedy of subtracting the “climate drift” is ineffective and adds to the variability. The culprit is the natural variability of the control runs, which exists even at quasi equilibration. Fortunately, for simulations with multidecadal time horizon, robust solutions can be obtained by branching off thousand-year-long control runs that reach “quasi equilibration” using a new protocol, which takes advantage of the fact that forced solutions to radiative forcing forget their initial condition after 30–40 yr and instead depend mostly on the trajectory of the radiative forcing. 出版者： Boston, MA: American Meteorological Society 出版日期： 2013-04-01 出處： Journal of the atmospheric sciences, 2013-04, Vol.70 (4), p.1291-1296 資源來源： EBSCOhost OmniFile Full Text Select 版權： 2014 INIST-CNRS 版權： Copyright American Meteorological Society Apr 2013 版權： Copyright American Meteorological Society 2013 識別號： ISSN: 0022-4928 識別號： ISSN: 1520-0469 識別號： EISSN: 1520-0469 識別號： DOI: 10.1175/JAS-D-12-0338.1 識別號： CODEN: JAHSAK

Impact of climate drift on twenty-first-century projection in a coupled atmospheric-ocean general circulation model

title: Impact of climate drift on twenty-first-century projection in a coupled atmospheric-ocean general circulation model abstract: 摘要： Reducing climate drift in coupled atmosphere–ocean general circulation models (AOGCMs) usually requires 1000–2000 years of spinup, which has not been practical for every modeling group to do. For the purpose of evaluating the impact of climate drift, the authors have performed a multimillennium-long control run of the Goddard Institute for Space Studies model (GISS-EH) AOGCM and produced different twentieth-century historical simulations and subsequent twenty-first-century projections by branching off the control run at various stages of equilibration. The control run for this model is considered at quasi equilibration after a 1200-yr spinup from a cold start. The simulations that branched off different points after 1200 years are robust, in the sense that their ensemble means all produce the same future projection of warming, both in the global mean and in spatial detail. These robust projections differ from the one that was originally submitted to the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), which branched off a not-yet-equilibrated control run. The authors test various common postprocessing schemes in removing climate drift caused by a not-yet-equilibrated ocean initial state and find them to be ineffective, judging by the fact that they differ from each other and from the robust results that branched off an equilibrated control. The authors' results suggest that robust twenty-first-century projections of the forced response can be achieved by running climate simulations from an equilibrated ocean state, because memory of the different initial ocean state is lost in about 40 years if the forced run is started from a quasi-equilibrated state. 出版者： Boston, MA: American Meteorological Society 出版日期： 2013-10-01 出處： Journal of the atmospheric sciences, 2013-10, Vol.70 (10), p.3321-3327 資源來源： EBSCOhost OmniFile Full Text Select 版權： 2014 INIST-CNRS 版權： Copyright American Meteorological Society Oct 2013 版權： Copyright American Meteorological Society 2013 識別號： ISSN: 0022-4928 識別號： EISSN: 1520-0469 識別號： DOI: 10.1175/JAS-D-13-0149.1 識別號： CODEN: JAHSAK

High-frequency sea level variations observed by GPS buoys using precise point positioning technique

title: High-frequency sea level variations observed by GPS buoys using precise point positioning technique abstract: 摘要： In this study, sea level variation observed by a 1-Hz Global Positioning System (GPS) buoy system is verified by comparing with tide gauge records and is decomposed to reveal high-frequency signals that cannot be detected from 6-minute tide gauge records. Compared to tide gauges traditionally used to monitor sea level changes and affected by land motion, GPS buoys provide high-frequency geocentric measurements of sea level variations. Data from five GPS buoy campaigns near a tide gauge at Anping, Tainan, Taiwan, were processed using the Precise Point Positioning (PPP) technique with four different satellite orbit products from the International GNSS Service (IGS). The GPS buoy data were also processed by a differential GPS (DGPS) method that needs an additional GPS receiver as a reference station and the accuracy of the solution depends on the baseline length. The computation shows the average Root Mean Square Error (RMSE) difference of the GPS buoy using DGPS and tide gauge records is around 3 - 5 cm. When using the aforementioned IGS orbit products for the buoy derived by PPP, its average RMSE differences are 5 - 8 cm, 8 - 13 cm, decimeter level, and decimeter-meter level, respectively, so the accuracy of the solution derived by PPP highly depends on the accuracy of IGS orbit products. Therefore, the result indicates that the accuracy of a GPS buoy using PPP has the potential to measure the sea surface variations to several cm. Finally, high-frequency sea level signals with periods of a few seconds to a day can be successfully detected in GPS buoy observations using the Ensemble Empirical Mode Decomposition (EMD) method and are identified as waves, meteotsunamis, and tides. 出版者： Taiwan: 中華民國地球科學學會出版日期： 2012-04-01 出處： TAO : Terrestrial, atmospheric, and oceanic sciences, 2012-04, Vol.23 (2), p.209-218 資源來源：華藝線上圖書館版權： 2012. 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.2011.10.05.01(Oc)