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Physical Sciences and Mathematics
University of Nebraska - Lincoln
Department of Earth and Atmospheric Sciences: Faculty Publications
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A Gridded Reconstruction Of Warm Season Precipitation For Asia Spanning The Past Half Millennium, Song Feng, Q. Steven Hu, Qianru Wu, Michael E. Mann
A Gridded Reconstruction Of Warm Season Precipitation For Asia Spanning The Past Half Millennium, Song Feng, Q. Steven Hu, Qianru Wu, Michael E. Mann
Department of Earth and Atmospheric Sciences: Faculty Publications
The authors reconstructed May–September precipitation over the Asian continent (5°–55°N, 60°–135°E) back to AD 1470 on the basis of tree-ring data, historical documentary records, ice core records, and the few long-term instrumental data series available in the region. They employed the method of Regularized Expectation Maximization (RegEM) and applied it to 44 subregions within the continent. Verification exercises demonstrate that the reconstruction is skillful over most of the study domain, with eastern China, India, and other regions of humid climate displaying the greatest skill. Lower reconstruction skill is observed in semiarid and arid regions, which was attributable at least in …
The Freshwater System West Of The Antarctic Peninsula: Spatial And Temporal Changes, Michael P. Meredith, Hugh J. Venables, Andrew Clarke, Hugh W. Ducklow, Matthew Erickson, Melanie J. Leng, Jan T. M. Lenaerts, Michiel R. Van Den Broeke
The Freshwater System West Of The Antarctic Peninsula: Spatial And Temporal Changes, Michael P. Meredith, Hugh J. Venables, Andrew Clarke, Hugh W. Ducklow, Matthew Erickson, Melanie J. Leng, Jan T. M. Lenaerts, Michiel R. Van Den Broeke
Department of Earth and Atmospheric Sciences: Faculty Publications
Climate change west of the Antarctic Peninsula is the most rapid of anywhere in the Southern Hemisphere, with associated changes in the rates and distributions of freshwater inputs to the ocean. Here, results from the first comprehensive survey of oxygen isotopes in seawater in this region are used to quantify spatial patterns of meteoric water (glacial discharge and precipitation) separately from sea ice melt. High levels of meteoric water are found close to the coast, due to orographic effects on precipitation and strong glacial discharge. Concentrations decrease offshore, driving significant southward geostrophic flows (up to ;30 cm s21). These produce …
Jurassic Earthquake Sequence Recorded By Multiple Generations Of Sand Blows, Zion National Park, Utah, David Loope, James F. Elder, Vitaly A. Zlotnik, Richard M. Kettler, Darryll T. Pederson
Jurassic Earthquake Sequence Recorded By Multiple Generations Of Sand Blows, Zion National Park, Utah, David Loope, James F. Elder, Vitaly A. Zlotnik, Richard M. Kettler, Darryll T. Pederson
Department of Earth and Atmospheric Sciences: Faculty Publications
Earthquakes along convergent plate boundaries commonly occur in sequences that are complete within 1 yr, and may include 8–10 events strong enough to generate sand blows. Dune crossbeds within the Jurassic Navajo Sandstone of Utah (western United States) enclose intact and truncated sand blows, and the intrusive structures that fed them. We mapped the distribution of more than 800 soft-sediment dikes and pipes at two small sites. All water-escape structures intersect a single paleo-surface, and are limited to the upper portion of the underlying set of cross-strata and the lower portion of the overlying set. A small portion of one …
Salinity And Climate Reconstructions From Continental Lakes, Sherilyn C. Fritz
Salinity And Climate Reconstructions From Continental Lakes, Sherilyn C. Fritz
Department of Earth and Atmospheric Sciences: Faculty Publications
Diatoms are widely used to reconstruct past environments because of their sensitivity to a range of environmental variables. Among the variables that exert a strong influence on diatoms are ionic concentration, expressed as salinity or conductivity, and ionic composition. Because the ionic concentration and composition of inland water bodies is affected by changes in effective moisture (precipitation minus evaporation, P – E), changes in the abundance of diatom species that vary in their salinity tolerances provide a tool for the reconstruction of past climate.
Effect Of The Strengthened Western Pacific Subtropical High On Summer Visibility Decrease Over Eastern China Since 1973, Wenjun Qu, Jun Wang, Shanhong Gao, Tongwen Wu
Effect Of The Strengthened Western Pacific Subtropical High On Summer Visibility Decrease Over Eastern China Since 1973, Wenjun Qu, Jun Wang, Shanhong Gao, Tongwen Wu
Department of Earth and Atmospheric Sciences: Faculty Publications
Daily visibility (Vis) data from 354 meteorological stations are used to evaluate the seasonal Vis trends over China from 1973 to 2009, which show that Vis decline is most distinct over eastern China in summer, with a trend of -1.4 km per decade or -34% in the 37 years. This rapid decline of summertime Vis is found to be partially associated with the intensification and westward extension of the western Pacific subtropical high (WPSH) that has occurred in recent years. Such a change in the strength and breadth of WPSH has resulted in more days with stable, hot, and humid …
Optimal Estimation For Global Ground-Level Fine Particulate Matter Concentrations, Aaron Van Donkelaar, Randall V. Martin, Robert J. D. Spurr, Eason Drury, Lorraine A. Remer, Robert C. Levy, Jun Wang
Optimal Estimation For Global Ground-Level Fine Particulate Matter Concentrations, Aaron Van Donkelaar, Randall V. Martin, Robert J. D. Spurr, Eason Drury, Lorraine A. Remer, Robert C. Levy, Jun Wang
Department of Earth and Atmospheric Sciences: Faculty Publications
We develop an optimal estimation (OE) algorithm based on top-of-atmosphere reflectances observed by the MODIS satellite instrument to retrieve near-surface fine particulatematter (PM2.5). The GEOS-Chem chemical transport model is used to provide prior information for the Aerosol Optical Depth (AOD) retrieval and to relate total column AOD to PM2.5. We adjust the shape of the GEOS-Chem relative vertical extinction profiles by comparison with lidar retrievals from the CALIOP satellite instrument. Surface reflectance relationships used in the OE algorithm are indexed by land type. Error quantities needed for this OE algorithm are inferred by comparison with AOD …
Constraints On Aerosol Sources Using Geos-Chem Adjoint And Modis Radiances, And Evaluation With Multisensor (Omi, Misr) Data, Xiaoguang Xu, Jun Wang, Daven Henze, Wenjun Qu, Monika Kopacz
Constraints On Aerosol Sources Using Geos-Chem Adjoint And Modis Radiances, And Evaluation With Multisensor (Omi, Misr) Data, Xiaoguang Xu, Jun Wang, Daven Henze, Wenjun Qu, Monika Kopacz
Department of Earth and Atmospheric Sciences: Faculty Publications
We present a new top-down approach that spatially constrains the amount of aerosol emissions using satellite (Moderate Resolution Imaging Spectroradiometer (MODIS)) observed radiances with the adjoint of a chemistry transport model (GEOS-Chem). This paper aims to demonstrate the approach through applying it to a case study that yields the following emission estimates over China for April 2008: 1.73 Tg for SO2, 0.72 Tg for NH3, 1.38 Tg for NOx, 0.10 Tg for black carbon, and 0.18 Tg for organic carbon from anthropogenic sources, which reflects, respectively, a reduction of 33.5%, 34.5%, 18.8%, 9.1%, and 15% in comparison to the prior …
Prelude To Seven Slots: Filling And Subsequent Modification Of Seven Broad Canyons In The Navajo Sandstone, South-Central Utah, David B. Loope, Ronald J. Goble, Joel P. L. Johnson
Prelude To Seven Slots: Filling And Subsequent Modification Of Seven Broad Canyons In The Navajo Sandstone, South-Central Utah, David B. Loope, Ronald J. Goble, Joel P. L. Johnson
Department of Earth and Atmospheric Sciences: Faculty Publications
Within a four square kilometer portion of Grand Staircase-Escalante National Monument, seven distinct slot canyons cut the Jurassic Navajo Sandstone. Four of the slots developed along separate reaches of a trunk stream (Dry Fork of Coyote Gulch), and three (including canyons locally known as “Peekaboo” and “Spooky”) are at the distal ends of south-flowing tributary drainages. All these slot canyons are examples of epigenetic gorges—bedrock channel reaches shifted laterally from previous reach locations. The previous channels became filled with alluvium, allowing active channels to shift laterally in places and to subsequently re-incise through bedrock elsewhere. New evidence, based on optically …
Optimal Estimation For Global Ground-Level Fine Particulate Matter Concentrations, Aaron Van Donkelaar, Randall V. Martin, Robert J. D. Spurr, Easan Drury, Lorraine A. Remer, Robert C. Levy, Jun Wang
Optimal Estimation For Global Ground-Level Fine Particulate Matter Concentrations, Aaron Van Donkelaar, Randall V. Martin, Robert J. D. Spurr, Easan Drury, Lorraine A. Remer, Robert C. Levy, Jun Wang
Department of Earth and Atmospheric Sciences: Faculty Publications
We develop an optimal estimation (OE) algorithm based on top-of-atmosphere reflectances observed by the MODIS satellite instrument to retrieve near-surface fine particulatematter (PM2.5). The GEOS-Chem chemical transport model is used to provide prior information for the Aerosol Optical Depth (AOD) retrieval and to relate total column AOD to PM2.5. We adjust the shape of the GEOS-Chem relative vertical extinction profiles by comparison with lidar retrievals from the CALIOP satellite instrument. Surface reflectance relationships used in the OE algorithm are indexed by land type. Error quantities needed for this OE algorithm are inferred by comparison with AOD observations taken by a …