Analysis and attribution of climate change in the upper atmosphere from 1950 to 2015 simulated by WACCM-X

Monitoring climatic changes in the thermosphere and ionosphere and understanding their causes is important for practical purposes. To support this effort and facilitate comparisons between observations and model results, a long transient simulation with the Whole Atmosphere Community Climate Model eXtension (WACCM‐X) from 1950 to 2015 was conducted. This simulation used realistic variations in solar and geomagnetic activity, main magnetic field changes, and trace gas emissions, including CO2, thereby including all known drivers of upper atmosphere climate change. Analysis of the full 1950‐2015 interval with a standard multi‐linear regression approach demonstrated difficulties in removing solar cycle effects sufficiently to obtain reliable trends. Results improved when an (F10.7a)2 was included in the regression model, in addition to terms for F10.7a, KP, and the trend itself. Comparisons with previous studies and analysis of spatial variations in trend estimates confirmed that the increase in CO2 concentration is the main driver of trends in thermosphere temperature and density, but at high (magnetic) latitudes effects of main magnetic field changes play a role as well, especially in the Northern hemisphere. Spatial patterns of trends in hmF2, NmF2, and total electron content indicate a superposition of CO2 and geomagnetic field effects, with the latter dominating trends in the region of ~50°S‐20°N, ~60°W‐20°E. Additional model experiments to investigate the indirect dynamical effects of climate change in the lower atmosphere (100 km) suggested that these effects are small and insignificant. However, current model limitations could mean that these effects are underestimated

SMLTM simulations of the diurnal tide: comparison with UARS observations

Wind and temperature observations in the mesosphere and lower thermosphere (MLT) from the Upper Atmosphere Research Satellite (UARS) reveal strong seasonal variations of tides, a dominant component of the MLT dynamics. Simulations with the Spectral mesosphere/lower thermosphere model (SMLTM) for equinox and solstice conditions are presented and compared with the observations. The diurnal tide is generated by forcing specified at the model lower boundary and by in situ absorption of solar radiation. The model incorporates realistic parameter-izations of physical processes including various dissipation processes important for propagation of tidal waves in the MLT. A discrete multi-component gravity-wave parameterization has been modified to account for seasonal variations of the background temperature. Eddy diffusion is calculated depending on the gravitywave energy deposition rate and stability of the background flow. It is shown that seasonal variations of the diurnal-tide amplitudes are consistent with observed variations of gravity-wave sources in the lower atmosphere.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47861/1/585_1997_Article_70151187.pd

Tidal influences on O 2 atmospheric band dayglow: HRDI observations vs. model simulations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95496/1/grl13062.pd

Future decreases in thermospheric neutral density in low Earth orbit due to carbon dioxide emissions

Increasing carbon dioxide causes cooling in the upper atmosphere and a secular decrease in atmospheric density over time. With the use of the Whole Atmospheric Community Climate Model with thermosphere and ionosphere extension (WACCM‐X), neutral thermospheric densities up to 500 km have been modelled under increasing carbon dioxide concentrations. Only carbon dioxide and carbon monoxide concentrations are changed between simulations, and solar activity is held low at F10.7 = 70 throughout. Neutral density decreases through to the year 2100 have been modelled using four carbon dioxide emission scenarios produced by the Intergovernmental Panel on Climate Change (IPCC). The years 1975 and 2005 have also been simulated, which indicated a historic trend of ‐5.8% change in neutral density per decade. Decreases in the neutral density relative to the year 2000 have been given for increasing ground‐level carbon dioxide concentrations. WACCM‐X shows there has already been a 17% decrease in neutral densities at 400 km relative to the density in the year 2000. This becomes a 30% reduction at the 50:50 probability threshold of limiting warming to 1.5°C, as set out in the Paris Agreement. A simple orbital propagator has been used to show the impact the decrease in density has on the orbital lifetime of objects travelling through the thermosphere. If the 1.5°C target is met, objects in LEO will have orbital lifetimes around 30% longer than comparable objects from the year 2000

A human glomerular SAGE transcriptome database

Background: To facilitate in the identification of gene products important in regulating renal glomerular structure and function, we have produced an annotated transcriptome database for normal human glomeruli using the SAGE approach. Description: The database contains 22,907 unique SAGE tag sequences, with a total tag count of 48,905. For each SAGE tag, the ratio of its frequency in glomeruli relative to that in 115 non-glomerular tissues or cells, a measure of transcript enrichment in glomeruli, was calculated. A total of 133 SAGE tags representing well-characterized transcripts were enriched 10-fold or more in glomeruli compared to other tissues. Comparison of data from this study with a previous human glomerular Sau3A-anchored SAGE library reveals that 47 of the highly enriched transcripts are common to both libraries. Among these are the SAGE tags representing many podocyte-predominant transcripts like WT-1, podocin and synaptopodin. Enrichment of podocyte transcript tags SAGE library indicates that other SAGE tags observed at much higher frequencies in this glomerular compared to non-glomerular SAGE libraries are likely to be glomerulus-predominant. A higher level of mRNA expression for 19 transcripts represented by glomerulus-enriched SAGE tags was verified by RT-PCR comparing glomeruli to lung, liver and spleen. Conclusions: The database can be retrieved from, or interrogated online at http://cgap.nci.nih.gov/SAGE. The annotated database is also provided as an additional file with gene identification for 9,022, and matches to the human genome or transcript homologs in other species for 1,433 tags. It should be a useful tool for in silico mining of glomerular gene expression

Pan-ethnic carrier screening and prenatal diagnosis for spinal muscular atrophy: clinical laboratory analysis of >72 400 specimens

Spinal muscular atrophy (SMA) is a leading inherited cause of infant death with a reported incidence of ∼1 in 10 000 live births and is second to cystic fibrosis as a common, life-shortening autosomal recessive disorder. The American College of Medical Genetics has recommended population carrier screening for SMA, regardless of race or ethnicity, to facilitate informed reproductive options, although other organizations have cited the need for additional large-scale studies before widespread implementation. We report our data from carrier testing (n=72 453) and prenatal diagnosis (n=121) for this condition. Our analysis of large-scale population carrier screening data (n=68 471) demonstrates the technical feasibility of high throughput testing and provides mutation carrier and allele frequencies at a level of accuracy afforded by large data sets. In our United States pan-ethnic population, the calculated a priori carrier frequency of SMA is 1/54 with a detection rate of 91.2%, and the pan-ethnic disease incidence is calculated to be 1/11 000. Carrier frequency and detection rates provided for six major ethnic groups in the United States range from 1/47 and 94.8% in the Caucasian population to 1/72 and 70.5% in the African American population, respectively. This collective experience can be utilized to facilitate accurate pre- and post-test counseling in the settings of carrier screening and prenatal diagnosis for SMA