Further evidences of deep convective vertical transport of water vapor through the tropopause   总被引：2，自引：0，他引：2  

Pao K. Wang  Martin Setvk  Walter Lyons  Willi Schmid  Hsin-Mu Lin 《Atmospheric Research》2009,94(3):400-408

A few years ago, we identified a deep convective transport mechanism, of water vapor through the tropopause, namely, storm top gravity wave breaking, such that tropospheric water substance can be injected into the lower stratosphere via this pathway. The main evidence presented previously was taken from the lower resolution AVHRR images of the storm anvil top cirrus plumes obtained by polar orbiting satellites. Recent observations have provided further supporting evidence for this important cross-tropopause transport mechanism. There are now many higher resolution satellite images, mainly from MODIS instrument, that show more definitely the existence of these plumes, many of which would probably be unseen by lower resolution images.Furthermore, a thunderstorm movie taken in Denver (USA) area during STEPS2000 field campaign and another thunderstorm movie taken by a building top webcam in Zurich also demonstrate that the jumping cirrus phenomenon, first identified by T. Fujita in 1980s, may be quite common in active thunderstorm cells, quite contrary to previous belief that it is rare. We have used a cloud model to demonstrate that the jumping cirrus is exactly the gravity wave breaking phenomenon that transports water vapor through the tropopause.These additional evidences provide increasing support that deep convection contributes substantially to the troposphere-to-stratosphere transport of water substance. This corroborates well with recent studies of the stratospheric HDO/H₂O ratio which is much highly than it would be if the transport is via slow ascent. The only explanation that can be used to interpret this observation at present is that water substance is transported through the tropopause via rapid vertical motion, i.e., deep convection.  相似文献   

Modeling climate change and biophysical impacts of crop production in the Austrian Marchfeld Region     

Franziska Strauss  Erwin Schmid  Elena Moltchanova  Herbert Formayer  Xiuying Wang 《Climatic change》2012,111(3-4):641-664

Climate change affects major biophysical processes in agricultural crop production (e.g. evaporation of plants and soils, nutrient cycles, and growth of plants). This analysis aims to assess some of these effects by simulating regional climate projections that are integrated in the biophysical process model EPIC (Environmental Policy Integrated Climate). Statistical climate models have been developed for six weather parameters based on daily weather records of a weather station in the Austrian Marchfeld region from 1975 to 2006. These models have been used to estimate daily weather parameters for the period 2007–2038. The resulting projections have been compared to climate scenarios provided from the TYNDALL Centre for Climate Change Research, which are based on General Circulation Models (GCMs). The comparison indicates some differences, namely a smaller temperature increase and a higher precipitation amount in the TYNDALL data. Both climate datasets have been used to simulate impacts of climate change on crop yields, topsoil organic carbon content, and nitrate leaching with EPIC and thus to perform a sensitivity analysis of EPIC. Yield impacts have been assessed for four simulated crops, i.e. 6.2?t/ha for winter wheat for statistical climate projections compared to 5.7?t/ha for TYNDALL scenarios, 10.6?t/ha for corn compared to 10.5?t/ha, 3.9?t/ha for sunflower compared to 3.7?t/ha, and 4.5?t/ha for spring barley compared to 4.3?t/ha—all values as an average over the period 2007–2038. Smaller differences have been simulated for topsoil organic carbon content i.e. 55.1?t/ha for the statistical climate projections compared to 55.3?t/ha for the TYNDALL scenarios and nitrate leaching i.e. 7.1?kg/ha compared to 11.1?kg/ha. All crop yields as well as topsoil organic carbon content and nitrate leaching show highest sensitivity to temperature and solar radiation.  相似文献   

IGS08: the IGS realization of ITRF2008   总被引：22，自引：6，他引：16  

P. Rebischung  J. Griffiths  J. Ray  R. Schmid  X. Collilieux  B. Garayt 《GPS Solutions》2012,16(4):483-494

On April 17, 2011, the International GNSS Service (IGS) stopped using the IGS05 reference frame and adopted a new one, called IGS08, as the basis of its products. The latter was derived from the latest release of the International Terrestrial Reference Frame (ITRF2008). However, the simultaneous adoption of a new set of antenna phase center calibrations by the IGS required slight adaptations of ITRF2008 positions for 65 of the 232 IGS08 stations. The impact of the switch from IGS05 to IGS08 on GNSS station coordinates was twofold: in addition to a global transformation due to the frame change from ITRF2005 to ITRF2008, many station coordinates underwent small shifts due to antenna calibration updates, which need to be accounted for in any comparison or alignment of an IGS05-consistent solution to IGS08. Because the heterogeneous distribution of the IGS08 network makes it sub-optimal for the alignment of global frames, a smaller well-distributed sub-network was additionally designed and designated as the IGS08 core network. Only 2?months after their implementation, both the full IGS08 network and the IGS08 core network already strongly suffer from the loss of many reference stations. To avoid a future crisis situation, updates of IGS08 will certainly have to be considered before the next ITRF release.  相似文献   

Sheath fold formation around slip surfaces     

Jacqueline E. Reber  Marcin Dabrowski  Daniel W. Schmid 《地学学报》2012,24(5):417-421

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Irrigation as adaptation strategy to climate change��a biophysical and economic appraisal for Swiss maize production     

Robert Finger  Werner Hediger  St��phanie Schmid 《Climatic change》2011,105(3-4):509-528

The impact of climate change on Swiss maize production is assessed using an approach that integrates a biophysical and an economic model. Simple adaptation options such as shifts in sowing dates and adjustments of production intensity are considered. In addition, irrigation is evaluated as an adaptation strategy. It shows that the impact of climate change on yield levels is small but yield variability increases in rainfed production. Even though the adoption of irrigation leads to higher and less variable maize yields in the future, economic benefits of this adoption decision are expected to be rather small. Thus, no shift from the currently used rainfed system to irrigated production is expected in the future. Moreover, we find that changes in institutional and market conditions rather than changes in climatic conditions will influence the development of the Swiss maize production and the adoption of irrigation in the future.  相似文献   

Improved antenna phase center models for GLONASS   总被引：6，自引：2，他引：4  

Rolf Dach  Ralf Schmid  Martin Schmitz  Daniela Thaller  Stefan Schaer  Simon Lutz  Peter Steigenberger  Gerhard Wübbena  Gerhard Beutler 《GPS Solutions》2011,15(1):49-65

Thanks to the increasing number of active GLONASS satellites and the increasing number of multi-GNSS tracking stations in the network of the International GNSS Service (IGS), the quality of the GLONASS orbits has become significantly better over the last few years. By the end of 2008, the orbit RMS error had reached a level of 3–4 cm. Nevertheless, the strategy to process GLONASS observations still has deficiencies: one simplification, as applied within the IGS today, is the use of phase center models for receiver antennas for the GLONASS observations, which were derived from GPS measurements only, by ignoring the different frequency range. Geo++ GmbH calibrates GNSS receiver antennas using a robot in the field. This procedure yields now separate corrections for the receiver antenna phase centers for each navigation satellite system, provided its constellation is sufficiently populated. With a limited set of GLONASS calibrations, it is possible to assess the impact of GNSS-specific receiver antenna corrections that are ignored within the IGS so far. The antenna phase center model for the GLONASS satellites was derived in early 2006, when the multi-GNSS tracking network of the IGS was much sparser than it is today. Furthermore, many satellites of the constellation at that time have in the meantime been replaced by the latest generation of GLONASS-M satellites. For that reason, this paper also provides an update and extension of the presently used correction tables for the GLONASS satellite antenna phase centers for the current constellation of GLONASS satellites. The updated GLONASS antenna phase center model helps to improve the orbit quality.  相似文献   

Application of polypyrrole actuators: feasibility of variable camber foils     

Madden  J.D.W. Schmid  B. Hechinger  M. Lafontaine  S.R. Madden  P.G.A. Hover  F.S. Kimball  R. Hunter  I.W. 《Oceanic Engineering, IEEE Journal of》2004,29(3):738-749

A decade of research into electroactive polymer actuators is leading to the exploration of applications. These technologies are not ready to compete with the internal combustion engine and electric motors in high power propulsion systems but are suitable for intermittent or aperiodic applications with moderate cycle life requirements, providing an alternative to solenoids and direct drive electric motors. Polypyrrole, an emerging actuator material, is applied to drive hydrodynamic control surfaces and in particular to change the camber of a foil. The foil is intended for use in the propeller blade of an autonomous underwater vehicle. A scaled prototype is constructed which employs polypyrrole actuators imbedded within the blade itself to vary camber. The kinematics required to generate camber change are demonstrated, with >30/spl deg/ deflections of the trailing edge being observed from both bending bilayer and linear actuator designs. Forces developed in still conditions are five times lower than the 3.5 N estimated to be required to implement variable camber. The observed 70 kJ/m/sup 3/ polypyrrole work density however is more than sufficient to produce the desired actuation from within the limited blade volume, enabling an application that is not feasible using direct drive electric motors. A key challenge with the polypyrrole actuators is to increase force without sacrificing speed of actuation.  相似文献   

Ground‐based lidar measurements of aerosols during ACE‐2: instrument description, results, and comparisons with other ground‐based and airborne measurements     

Ellsworth J. Welton  Kenneth J. Voss  Howard R. Gordon  Hal Maring  Alexander Smirnov  Brent Holben  Beat Schmid  John M. Livingston  Philip B. Russell  Philip A. Durkee  Paola Formenti  Meinrat O. Andreae 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):636-651

A micro‐pulse lidar system (MPL) was used to measure the vertical and horizontal distribution of aerosols during the Aerosol Characterization Experiment 2 (ACE‐2) in June and July of 1997. The MPL measurements were made at the Izaña observatory (IZO), a weather station located on a mountain ridge (28°18' N, 16°30' W, 2367 m asl) near the center of the island of Tenerife, Canary Islands. The MPL was used to acquire aerosol backscatter, extinction, and optical depth profiles for normal background periods and periods influenced by Saharan dust from North Africa. System tests and calibration procedures are discussed, and an analysis of aerosol optical profiles acquired during ACE‐2 is presented. MPL data taken during normal IZO conditions (no dust) showed that upslope aerosols appeared during the day and dissipated at night and that the layers were mostly confined to altitudes a few hundred meters above IZO. MPL data taken during a Saharan dust episode on 17 July showed that peak aerosol extinction values were an order of magnitude greater than molecular scattering over IZO, and that the dust layers extended to 5 km asl. The value of the dust backscatter–extinction ratio was determined to be 0.027±0.007 sr⁻¹. Comparisons of the MPL data with data from other co‐located instruments showed good agreement during the dust episode.  相似文献   

In situ aerosol‐size distributions and clear‐column radiative closure during ACE‐2     

D. R. Collins  H. H. Johnsson  J. H. Seinfeld  R. C. Flagan  S. Gassó  D. A. Hegg  P. B. Russell  B. Schmid  J. M. Livingston  E. Öström  K. J. Noone  L. M. Russell  J. P. Putaud 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):498-525

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Late Quaternary folding in the Jura Mountains: evidence from syn‐erosional deformation of fluvial meanders     

Herfried Madritsch  Frank Preusser  Olivier Fabbri  Vincent Bichet  Fritz Schlunegger  Stefan M. Schmid 《地学学报》2010,22(2):147-154

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