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Zhang Y.,Chinese Academy of Meteorological Sciences | Zhao Y.,Shanghai Institute of Meteorological Science | Zhao Y.,Chinese Academy of Meteorological Sciences | Chen S.,Tianjin Climate Center | And 2 more authors.
Journal of Applied Meteorology and Climatology | Year: 2015

Projections of climate change impacts on crop yields are subject to uncertainties, and quantification of such uncertainty is essential for the effective use of the projection results for adaptation and mitigation purposes. This work analyzes the uncertainties in maize yield predictions using two crop models together with three climate projections downscaled with one regional climate model nested with three global climate models under the A1B emission scenario in northeast China (NEC). Projections were evaluated for the Zhuanghe agrometeorological station in NEC for the 2021-50 period, taking 1971-2000 as the baseline period. The results indicated a yield reduction of 13% during 2021-50, with 95% probability intervals of (-41%, +12%) relative to 1971-2000. Variance decomposition of the yield projections showed that uncertainty in the projections caused by climate and crop models is likely to change with prediction period, and climate change uncertainty generally had a larger impact on projections than did crop model uncertainty during the 2021-50 period. In addition, downscaled climate projections had significant bias that can introduce significant uncertainties in yield projections. Therefore, they have to be bias corrected before use. © 2015 American Meteorological Society. Source

Han Z.-H.,Shanghai Institute of Meteorological Science | Han Z.-H.,Tongji University | Gu M.,Tongji University
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2015

Based on rigid model wind tunnel tests, the wind load characteristics of double-side and three-side single column-supported billboards were analyzed, and their wind-induced vibration characteristics were studied using the time history analysis method. The results showed that the mean and fluctuating total wind loading coefficients for a double-side billboard have the maximum values of 1.46 and 0.17 under 0°~15° wind direction angle, while those of a three-side billboard have the maximum values of 1.45 and 0.16 under 0° wind direction angle; their mean torgue coefficient reaches the maximum value under 52.5° and 30° wind direction angles, respectively; the resonance energy of node displacement for a double-side billboard is provided by the bending mode perpendicular to the panels, while that for a three-side billboard is provided by the bending modes perpendicular to and parallel to the center line of the triangle composed with panels; the resonance energy of beam torsion angle for two billboards is provided by torsional modes; the most unfavorable condition for bending vibration of two billboards is 0° wind direction angle, and the wind vibration coefficients are 1.51 and 1.59, respectively; while the most unfavorable conditions for torsional vibration of two billboards are 52.5° and 30° wind direction angles the wind vibration coefficient are 1.63 and 2.65, respectively. ©, 2015, Chinese Vibration Engineering Society. All right reserved. Source

Zhou X.,Tongji University | Han Z.,Shanghai Institute of Meteorological Science | Gu M.,Tongji University | Zhang A.-A.,Shanghai World Expo Land Holding Co. | And 2 more authors.
Earthquake Engineering and Engineering Vibration | Year: 2013

The wind-induced responses of a large-scale membrane structure, Expo Boulevard, are evaluated in this study. To obtain the wind pressure distribution on the roof surface, a wind tunnel test is performed. A brief analysis of wind pressure on the membrane roof is conducted first and then an analysis of the wind-induced responses of the structure is carried out using a numerical integral method in the time domain. In the process of calculation, the geometrical nonlinearity is taken into account. Results indicate that mean, RSM and peak values of the structure responses increase nonlinearly while the approaching flow velocity increases. Strong nonlinear characteristics are observed in the displacement responses, whereas the responses of nodal stress and cable axial force show minimal nonlinear properties when the membrane structure is subjected to wind loads. Different values of the damping ratio only have a minimal impact on the RSM response of the structure because the background component is a dominant part of the total dynamic response and the resonant component is too small. As the damping ratio increases from 0.02 to 0.05, the RMS responses of vertical displacement, nodal stress and cable axial force decrease by 8.1%, 6.7% and 17.9%, respectively. Since the mean component plays a significant role in the wind-induced response, the values of the gust response factor are not high for Expo Boulevard. © 2013 Institute of Engineering Mechanics, China Earthquake Administration and Springer-Verlag Berlin Heidelberg. Source

Fang P.-Z.,Shanghai Typhoon Institute of China Meteorological Administration | Gu M.,Tongji University | Tan J.-G.,Shanghai Institute of Meteorological Science | Han Z.-H.,Shanghai Institute of Meteorological Science
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2015

Wall function is preferred to model the low Reynolds-number flow near wall based on the Reynolds-averaged Navier-Stokes turbulent models. Then wall function problem in simulating the atmospheric boundary layer based on the standard turbulent model was investigated. An extra term which considers the extra effects induced by non-uniform and irregular distribution of rough elements such as various structures on the land surface was proposed and appended to the widely accepted standard wall function. The effectiveness and application situation of the proposed term were demonstrated by simulating a neutral wind field with the scale of 1: 300 featured by larger aerodynamic roughness length. The flow around the TTU model in a neutral wind field with the scale of 1: 50 was then simulated. The extra term is shown to be necessary to solve the wall function problem, i.e., the preservation inlet flow boundary conditions in computation domain in both cases ©, 2015, Chinese Vibration Engineering Society. All right reserved. Source

Peng J.,Beijing Normal University | Peng J.,Shanghai Institute of Meteorological Science | Li Z.,Beijing Normal University | Li Z.,The Interdisciplinary Center | And 6 more authors.
Journal of the Atmospheric Sciences | Year: 2016

It has been widely recognized that aerosols can modify cloud properties, but it remains uncertain how much the changes and associated variations in cloud radiative forcing are related to aerosol loading. Using 4 yr of A-Train satellite products generated from CloudSat, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations satellite, and the Aqua satellite, the authors investigated the systematic changes of deep cloud properties and cloud radiative forcing (CRF) with respect to changes in aerosol loading over the entire tropics. Distinct correlations betweenCRF and aerosol loading were found. Systematic variations in both shortwave and longwave CRF with increasing aerosol index over oceans and aerosol optical depth over land for mixed-phase clouds were identified, but little change was seen in liquid clouds. The systematic changes are consistent with themicrophysical effect and the aerosol invigoration effect. Although this study cannot fully exclude the influence of other factors, attempts were made to explore various possibilities to the extent that observation data available can offer. Assuming that the systematic dependence originates from aerosol effects, changes in CRF with respect to aerosol loading were examined using satellite retrievals. Mean changes in shortwave and longwave CRF from very clean to polluted conditions ranged from -192.84 to -296.63 W m-2 and from 18.95 to 46.12 W m -2 over land, respectively, and from -156.12 to -170.30 W m-2 and from 6.76 to 11.67 W m-2 over oceans, respectively. © 2016 American Meteorological Society. Source

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