The features of the MJO during two types of El Ni no events are investigated in this paper using the daily NCEP-2reanalysis data, OLR data from NOAA, and Real-time Multivariate MJO index for the period 1979–2012. The results indicate that the MJO exhibits distinct features during eastern Pacific(EP) El Ni no events, as compared to central Pacific(CP) El Ni no events. First, the intensity of the MJO is weakened during EP El Ni no winters from the tropical eastern Indian Ocean to the western Pacific, but enhanced during CP El Ni no winters. Second, the range of the MJO eastward propagation is different during the two types of El Ni no events. During EP El Ni no winters, the MJO propagates eastwards to 120?W, but only to 180?during CP El Ni no winters. Finally, the frequency in eight phases of the MJO may be affected by the two types of El Ni no. Phases 2 and 3 display a stronger MJO frequency during EP El Ni no winters, but phases 4 and 5 during CP El Ni no winters.
By aggregating MODIS(moderate-resolution imaging spectroradiometer) AOD(aerosol optical depth) and OMI(ozone monitoring instrument) UVAI(ultra violet aerosol index)datasets over 2010–2014, it was found that peak aerosol loading in seasonal variation occurred annually in spring over the Gulf of Tonkin(17–23°N, 105–110°E). The vertical structure of the aerosol extinction coefficient retrieved from the spaceborne lidar CALIOP(cloud-aerosol lidar with orthogonal polarization) showed that the springtime peak AOD could be attributed to an abrupt increase in aerosol loading between altitudes of 2 and 5 km.In contrast, aerosol loading in the low atmosphere(below 1 km) was only half of that in winter. Wind fields in the low and high atmosphere exhibited opposite transportation patterns in spring over the Gulf of Tonkin, implying different sources for each level. By comparing the emission inventory of anthropogenic sources with biomass burning, and analyzing the seasonal variation of the vertical structure of aerosols over the Northern Indo-China Peninsula(NIC), it was concluded that biomass burning emissions contributed to high aerosol loading in spring. The relatively high topography and the high surface temperature in spring made planetary boundary layer height greater than 3 km over NIC. In addition, small-scale cumulus convection frequently occurred, facilitating pollutant rising to over 3 km, which was a height favoring long-range transport. Thus, pollutants emitted from biomass burning over NIC in spring were raised to the high atmosphere, then experienced long-range transport, leading to the increase in aerosol loading at high altitudes over the Gulf of Tonkin during spring.更多还原
The Gravity Recovery and Climate Experiment(GRACE) has been measuring temporal and spatial variations of mass redistribution within the Earth system since2002. As large earthquakes cause significant mass changes on and under the Earth’s surface,GRACE provides a new means from space to observe mass redistribution due to earthquake deformations. GRACE serves as a good complement to other earthquake measurements because of its extensive spatial coverage and being free from terrestrial restriction. During its over 10 years mission,GRACE has successfully detected seismic gravitational changes of several giant earthquakes,which include the 2004 Sumatra–Andaman earthquake,2010 Maule(Chile) earthquake,and 2011 Tohoku-Oki(Japan) earthquake. In this review,we describe by examples how to process GRACE timevariable gravity data to retrieve seismic signals,and summarize the results of recent studies that apply GRACE observations to detect co- and post-seismic signals and constrain fault slip models and viscous lithospheric structures. We also discuss major problems and give an outlook in this field of GRACE application.
Isopycnal analyses were performed on the Global Ocean Data Assimilation System(GODAS) to determine the oceanic processes leading to so-called second-year cooling of the La Nina event. In 2010–12, a horseshoe-like pattern was seen,connecting negative temperature anomalies off and on the Equator, with a dominant influence from the South Pacific. During the 2010 La Nina event, warm waters piled up at subsurface depths in the western tropical Pacific. Beginning in early 2011,these warm subsurface anomalies propagated along the Equator toward the eastern basin, acting to reverse the sign of sea surface temperature(SST) anomalies(SSTAs) there and initiate a warm SSTA. However, throughout early 2011, pronounced negative anomalies persisted off the Equator in the subsurface depths of the South Pacific. As isopycnal surfaces outcropped in the central equatorial Pacific, negative anomalies from the subsurface spread upward along with mean circulation pathways, naturally initializing a cold SSTA. In the summer, a cold SSTA reappeared in the central basin, which subsequently strengthened due to the off-equatorial effects mostly in the South Pacific. These SSTAs acted to initiate local coupled air–sea interactions, generating atmospheric–oceanic anomalies that developed and evolved with the second-year cooling in the fall of 2011. However, the cooling tendency in mid-2012 did not develop into another La Nina event, since the cold anomalies in the South Pacific were not strong enough. An analysis of the 2007–09 La Nina event revealed similar processes to the2010–12 La Nina event.
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