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Das L.,Japan Agency for Marine - Earth Science and Technology | Annan J.D.,Japan Agency for Marine - Earth Science and Technology | Hargreaves J.C.,Japan Agency for Marine - Earth Science and Technology | Emori S.,National Institutes for Environmental Studies
Climate Research | Year: 2012

In the present study we investigate the performance of climate models which contributed to the past 3 Intergovernmental Panel for Climate Change (IPCC) assessment reports for the Gangetic West Bengal region of east India (6° × 6°). Analysing present-day seasonal rainfall and temperature over the domain, we compare the results of the models (from the 6 modelling centres common to the second, third and fourth assessment reports-SAR, TAR and AR4, respectively) in order to judge to what extent these global models have improved on a regional scale. Metrics for model evaluation are not yet firmly established in the literature, so in this paper we compare and contrast the results from a number of different statistics used in previous studies. We also analyse the impact of topography on the results obtained for the AR4 models. We find that most models improved from SAR to AR4, although there is some variation in this result depending on seasons, variables and on which statistical methods are used in the analysis. The multi-model mean of the 6 models improves from SAR to TAR to AR4. The overall best performance in this region in the AR4 is the Japanese model, MIROC, but the best model in terms of improving skill from SAR to AR4 is the GFDL model from the United States. Correcting for errors in the model topographies produced an overall improvement of spatial patterns and error statistics, and greatly improves the performance of 1 model (CGCM) which has poor topography, but does not affect the ranking of the other models. © Inter-Research 2012. Source


Das L.,Japan Agency for Marine - Earth Science and Technology | Annan J.D.,Japan Agency for Marine - Earth Science and Technology | Hargreaves J.C.,Japan Agency for Marine - Earth Science and Technology | Emori S.,National Institutes for Environmental Studies
Atmospheric Science Letters | Year: 2011

In this study, we used two novel methods to estimate urban contamination in the Japanese temperature record of the last century. First, we tested different criteria for choosing the rural stations, and found little sensitivity to the method, though the presence of a decreasing local population trend appeared to be a useful indicator. Second, we investigated the relationship between the regional sea surface temperature (SST) and surface air temperature over land, and found a very strong relationship across the coupled model intercomparison project phase 3 multi-model ensemble. Applying this relationship to observational SST data indicates little or no contamination of the trends from the stations identified as rural. © 2011 Royal Meteorological Society. Source


Okamoto H.,Kyushu University | Sato K.,Kyushu University | Hagihara Y.,Kyushu University | Nishizawa T.,National Institutes for Environmental Studies
AIP Conference Proceedings | Year: 2013

We develop algorithms that can be applied to EarthCARE Cloud Profiling Radar (CPR) and Atmospheric backscatter LIdar (ATLID) and discuss about the expected products. EarthCARE will carry CPR and ATLID and these combination corresponds to the CloudSat and CALIPSO for the A-train. Due to the similarities between the EarthCARE and the A-train, it will be possible to apply the similar types of algorithms that have been already developed and extensively used for the analyses of the A-train satellites and it is therefore expected to obtain the similar cloud products for the EarthCARE. On the other hand, there are some differences between the EarthCARE and A-train satellites, e.g., the EarthCRAE CPR has better sensitivity compared with the CloudSat. And Doppler capability of the EarthCARE-CPR is a new element and is expected to provide the better constraint for the retrievals of cloud/precipitation microphysics. And the vertical air motion and sedimentation velocity of cloud particles will be inferred. © 2013 AIP Publishing LLC. Source


Watanabe H.,National Institutes for Environmental Studies
Magnetic Resonance in Medical Sciences | Year: 2012

When radiofrequency (RF) transmission field represents B1 +, the reception field represents B1 -*. The distribution of those maps demonstrates asymmetric features at high field magnetic resonance (MR) imaging. Both maps are in mirror symmetry to one another. Almost symmetric distribution of the B1 field was expected on the laboratory frame in a symmetric sample loaded inside the RF coil designed to achieve a homogeneous B1 field. Then, a simple change was made in the coordinate transformation equation of RF fields between the rotating and laboratory frames in both linear and quadrature modes to investigate the source of this feature of asymmetry. The magnitude of rotating frame components, B1 + and B1 -, consists of the magnitude and the phase difference of the laboratory frame components. The rotating frame components differ in the sign of the sinusoidal phase difference. B1 + is equal to B1 - at lower field because phase changes that depend on position can be ignored. At higher fields, the magnitude component has a symmetric profile, and distribution in the phase component is antisymmetric. Thus, the distributions of B1 + and B1 - maps demonstrate mirror symmetry. Maps of magnitude and phase components were examined in the laboratory frame. Their maps were computed from B1 + and B1 - maps of the human brain and of a spherical saline phantom measured at 4.7T. It was concluded from these analytical and experimental results that the asymmetric and mirror symmetric distributions in B1 + and B1 - are derived from the phase difference in the laboratory frame. Source


Watanabe H.,National Institutes for Environmental Studies
Magnetic Resonance in Medical Sciences | Year: 2012

We demonstrated that the radiofrequency (RF) reception field is proportional to B1 -*straightforwardly in magnetic resonance (MR) imaging experiments at 4.7T. We compared maps of the reception field and the B1 - of a saline phantom in magnitude and phase. First, we measured the image using an adiabatic spin echo (ASE) sequence with homogeneous excitation. That image corresponds to a map of the reception field. Next, we rotated the RF coil with the sample 180° around the vertical axis to measure the map of the transmission field that corresponded to B1 - in the original configuration. The magnitude of the distribution fields of the reception field and B1 - maps was almost identical. Examining the phases of the ASE images in the original and inverted configurations, we observed almost the same distribution in both phase maps, which indicated the proportionality of the reception field to B1 -*. Source

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