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Deng Y.,University of Texas at Arlington | Huang Y.,University of Texas at Arlington | Solomon S.,High Altitude Observatory | Qian L.,High Altitude Observatory | And 3 more authors.
Journal of Geophysical Research: Space Physics

The record-low thermospheric density during the last solar minimum has been reported and it has been mainly explained as the consequence of the anomalously low solar extreme ultraviolet (EUV) irradiance. In this study, we examined the variation of the energy budget to the Earth's upper atmosphere during last solar cycle from both solar EUV irradiance and geomagnetic energy, including Joule heating and particle precipitation. The globally integrated solar EUV power was calculated from the EUV flux model for aeronomic calculations (EUVAC) driven by the MgII index. The annal average of solar power in 2008 was 33 GW lower than that in 1996. The decrease of the globally integrated geomagnetic energy from 1996 to 2008 was close to 29 GW including 13 GW for Joule heating from Weimer (2005b) and 16 GW for particle precipitation from NOAA Polar-Orbiting Environmental Satellites (POES) measurements. Although the estimate of the solar EUV power and geomagnetic energy vary from model to model, the reduction of the geomagnetic energy was comparable to the solar EUV power. The Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM) simulations indicate that the solar irradiance and geomagnetic energy variations account for 3/4 and 1/4 of the total neutral density decrease in 2008, respectively. © 2012. American Geophysical Union. All Rights Reserved. Source

Mao J.,Oak Ridge National Laboratory | Shi X.,Oak Ridge National Laboratory | Ma L.,National Climate Center | Kaiser D.P.,Oak Ridge National Laboratory | And 2 more authors.
Journal of Climate

Using a recently homogenized observational daily maximum (TMAX) and minimum temperature (TMIN) dataset for China, the extreme temperatures from the 40-yr ECMWF Re-Analysis (ERA-40), the Japanese 25-year Reanalysis (JRA-25), the NCEP/Department of Energy Global Reanalysis 2 (NCEP-2), and the ECMWF's ERA-Interim (ERAIn) reanalyses for summer (June-August) and winter (December-February) are assessed by probability density functions for the periods 1979-2001 and 1990-2001. For 1979-2001, no single reanalysis appears to be consistently accurate across eight areas examined over China. The ERA-40 and JRA-25 reanalyses show similar representations and close skill scores over most of the regions of China for both seasons. NCEP-2 generally has lower skill scores, especially over regions with complex topography. The regional and seasonal differences identified are commonly associated with different geographical locations and the methods used to diagnose these quantities. All the selected reanalysis products exhibit better performance for winter compared to summer over most regions of China. The TMAX values from the re-analysis tend to be systematically underestimated, while TMIN is systematically closer to observed values than TMAX. Comparisons of the reanalyses to reproduce the 99.7 percentiles for TMAX and 0.3 percentiles for TMIN show that most reanalyses tend to underestimate the 99.7 percentiles in maximum temperature both in summer and winter. For the 0.3 percentiles in TMIN, NCEP-2 is relatively inaccurate with a 2128C cold bias over the Qinghai-Tibetan Plateau in winter. ERA-40 and JRA-25 generally overestimate the extreme TMIN, and the extreme percentage differences of ERA-40 and JRA-25 are quite similar over all of the regions. The results are generally similar for 1990-2001, but in contrast to the other three reanalysis products the newly released ERAIn is very reasonable, especially for wintertime TMIN, with a skill score greater than 0.83 for each region of China. This demonstrates the great potential of this product for use in future impact assessments on continental scales where those impacts are based on extreme temperatures. © 2010 American Meteorological Society. Source

Yu G.,Ocean University of China | Zhang J.-Y.,China Meteorological Administration
Energy Procedia

Reclamation is the important utilization manner of ocean for mankind. Yet because reclamation changes natural bank shape in short term and small scale, so it can strongly disturb the whole natural system and bring a new misbalance, which affect the stability, diversity and sustainability of the seashore. In order to avoid and lighten the influence of reclamation, we should analyze and diagnose the possible effects, which can do some theory preparations for settling this problem. As a case study in Jiaozhou Bay, this paper selects 9 indicators to base the indicator system. The frame principle of the indicator system includes scientific, synthetical, viable, representative, hierarchical, systematic and data available. Basing the influencing aspects, this article uses the method of analytic hierarchy process (AHP), qualitative and quantitive method to calculate the indicators. By using the judging matrix, hierarchy sorting and indicators, the paper calculates the effect degree of reclamation to environment and ecosystem is comparatively high, and its growth is an increasing process in Jiaozhou Bay. From this point, with the reclamation scale is increasing, the effect degree of reclamation to environment and ecosystem is more and more serious. © 2011 Published by Elsevier Ltd. Source

Xu J.,Sichuan Agricultural University | Xu J.,CAS Institute of Atmospheric Physics | Zhang W.,Chinese Academy of Sciences | Zheng Z.,CAS Institute of Atmospheric Physics | And 2 more authors.
Acta Meteorologica Sinica

There is an increasing trend to incorporate the basin hydrological model into the traditional land surface model (LSM) to improve the description of hydrological processes in them. For incorporating with the Noah LSM, a new rainfall-runoff model named XXT (the first X stands for Xinanjiang, the second X stands for hybrid, and T stands for TOPMODEL) was developed and presented in this study, based on the soil moisture storage capacity distribution curve (SMSCC), some essential modules of the Xinanjiang model, together with the simple model framework of the TOPMODEL (a topography based hydrological model). The innovation of XXT is that the water table is incorporated into SMSCC and it connects the surface runoff production with base flow production. This improves the description of the dynamically varying saturated areas that produce runoff and also captures the physical underground water level. XXT was tested in a small-scale watershed Youshuijie (946 km 2) and a large-scale watershed Yinglouxia (10009 km 2) in China. The results show that XXT has better performance against the TOPMODEL and the Xinanjiang model for the two watersheds in both the calibration period and the validation period in terms of the Nash-Sutcliffe efficiency. Moreover, XXT captures the largest peak flow well for both the small- and large-scale watersheds during the validation period, while the TOPMODEL produces significant overestimates or underestimates, so does the Xinanjiang model. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2012. Source

Wang Y.,Chinese Academy of Meteorological Sciences | Zhao P.,National Meteorological Information Center | Yu R.,China Meteorological Administration
International Journal of Climatology

Using the Normalized Difference Vegetation Index of NOAA/AVHRR, the European Centre for Medium-Range Weather Forecast reanalysis and the Climate Prediction Center Merged Analysis of Precipitation data for the period 1982-1999, the relationship between the inter-decadal variability of spring (April-May) vegetation over the Tibetan Plateau (TP) and spring rainfall over eastern China was investigated. The results show that when the vegetation over the TP increases in spring, the spring rainfall enhances to the north of the Yangtze River and reduces to the south of the river. This relationship is well supported by the feedback of vegetation to climate and the background atmospheric circulation changes. Corresponding to more vegetation over the TP in spring, the surface sensible heating increases and local air temperature at the surface and in the troposphere also increases. The air volume expands, and the divergence becomes dominant in high-level atmosphere over the TP, with an increase in the upper-tropospheric geopotential height. This indicates an upper-tropospheric intensified ridge over the TP in spring. The intensified ridge extends toward eastern China. An anomalous anti-cyclone appears over the TP and eastern China, with anomalous divergence in the upper troposphere and anomalous convergence in the lower troposphere. Meanwhile, an anomalous cyclonic circulation appears in the lower troposphere over the northern region of eastern China, accompanying with the local anomalous upward motion. Therefore, the spring rainfall enhances over these regions. To the south of the upper-tropospheric anomalous anti-cyclonic centre, however, the upper easterlies from the western North Pacific Ocean retard while reaching the southeast coasts of China. This may result in the upper-tropospheric anomalous convergence, with anomalous divergence and an anomalous anti-cyclonic circulation in the lower troposphere over southeastern China and its coasts. Consequently, the spring rainfall weakens over these regions. © 2009 Royal Meteorological Society. Source

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