Marine Low Clouds : Radiation, Turbulence, and Forecasting

High-resolution ship-based observations of a nearly uniform stratocumulus deck in the southeast Pacific during 17 days of the 2008 VOCALS regional experiment elucidate radiation and turbulence in the marine boundary layer (MBL). A new method for prescribing observations-based cloud properties to the Rapid Radiative Transfer Model is presented and applied to the VOCALS dataset. The simulated radiative fluxes compare well with surface observations and with simulations from several other commonly employed methods, particularly during times of high drizzle content and/or precipitation. Clear-sky and cloudy scenarios illustrate the radiative effect of clouds on the MBL. Turbulence estimates are made for the stratocumulus layer using the simulated radiative fluxes and vertical velocity observations from the NOAA W-band Doppler cloud radar. The averages and diurnal cycles of the terms in the turbulent kinetic energy (TKE) budget are presented. 10-minute vertical velocity statistics and estimates of TKE budget terms reveal a robust diurnal cycle of weak turbulence during daylight hours with a rapid increase near sundown followed by sustained strong turbulence at night. Buoyant production is driven by cloud-top longwave radiative cooling during the night, but is offset and dominated by absorption of solar radiation from ~0900-1600 LT. At night, dissipation increases toward cloud base while vertical velocity variance is nearly constant with height. This suggests larger-scale turbulence occurs near cloud-top while dissipation interacts with smaller-scale turbulence near cloud base. Cloud-top entrainment rates are estimated from the entrainment heat flux calculated as a residual from the heat budget. Entrainment, with an average value of 4.6 mm s-1, has a diurnal cycle similar to turbulence with larger values at night. The third part of this dissertation presents one of the first studies using reforecast data to produce downscaled low cloud probabilistic forecasts for aviation applications. Probability of low cloud ceiling and visibility are forecast using analogs chosen from an ensemble of reforecasts, on the basis of their agreement with thermodynamic soundings. Skillful forecasts are produced for up to 30-hour leads times using reforecasts of 1° resolution at major airports across the continental United States. These probabilistic forecasts outperform climatology at all lead times and trained forecasters at nine-hour and longer lead times. These results suggest that real-time forecasts based on analog reforecasts is a useful approach for aviation applications with potential to enhance safety and commerce

The Time Scales of Variability of Marine Low Clouds

Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. All AMS journals and monograph publications are registered with the Copyright Clearance Center (http://www.copyright.com). Questions about permission to use materials for which AMS holds the copyright can also be directed to the AMS Permissions Officer at [email protected]. Additional details are provided in the AMS Copyright Policy statement, available on the AMS website (http://www.ametsoc.org/CopyrightInformation).Multidecade global regressions of inversion strength, vertical velocity, and sea surface temperature (SST) on low cloud amount, from subdaily to multiyear time scales, refute the dominance of seasonal inversion strength on marine low cloud variability. Multiday low cloud variance averaged over the eastern Pacific and Atlantic stratocumulus regions [5 × 10−2 (cloud amount)2] is twice the subdaily variance and 5 times larger than the multimonth variance. The broad multiday band contains most (60%) of the variance, despite strong seasonal (annual) and diurnal spectral peaks. Multiday low cloud amount over the eastern tropical and midlatitude oceans is positively correlated to inversion strength, with a slope of 2%–5% K−1. Anecdotes show multiday low cloud and inversion strength anomalies propagate equatorward from midlatitudes. Previously shown correlations of low clouds to strong inversions and cool SST on monthly and longer time scales in the stratocumulus regions imply positive cloud-radiative feedbacks, with e-folding time scales of 300 days for SST and 14 days for atmospheric boundary layer temperature. On multimonth time scales, removing the effect of SST on low clouds reduces the low cloud amount explained by inversion strength by a factor of 3, but SST has a small effect at other time scales. Contrary to their positive correlation in the stratocumulus cloud decks, low clouds are anticorrelated to inversion strength over most of the tropics on daily and subdaily time scales

The complex genetics of gait speed:Genome-wide meta-analysis approach

Emerging evidence suggests that the basis for variation in late-life mobility is attributable, in part, to genetic factors, which may become increasingly important with age. Our objective was to systematically assess the contribution of genetic variation to gait speed in older individuals. We conducted a meta-analysis of gait speed GWASs in 31,478 older adults from 17 cohorts of the CHARGE consortium, and validated our results in 2,588 older adults from 4 independent studies. We followed our initial discoveries with network and eQTL analysis of candidate signals in tissues. The meta-analysis resulted in a list of 536 suggestive genome wide significant SNPs in or near 69 genes. Further interrogation with Pathway Analysis placed gait speed as a polygenic complex trait in five major networks. Subsequent eQTL analysis revealed several SNPs significantly associated with the expression of PRSS16, WDSUB1 and PTPRT, which in addition to the meta-analysis and pathway suggested that genetic effects on gait speed may occur through synaptic function and neuronal development pathways. No genome-wide significant signals for gait speed were identified from this moderately large sample of older adults, suggesting that more refined physical function phenotypes will be needed to identify the genetic basis of gait speed in aging

The three-dimensional distribution of clouds over the Southern Hemisphere high latitudes

The authors exploit three years of data from the CloudSat and Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellites to document for the first time the seasonally varying vertical structure of cloudiness throughout Antarctica and the high-latitude Southern Ocean. The results provide a baseline reference of Southern Hemisphere high-latitude cloudiness for future observational and modeling studies, and they highlight several previously undocumented aspects and key features of Antarctic cloudiness. The key features of high-latitude Southern Hemisphere cloudiness documented here include 1) a pronounced seasonal cycle in cloudiness over the high-latitude Southern Hemisphere, with higher cloud incidences generally found during the winter season over both the Southern Ocean and Antarctica; 2) two distinct maxima in vertical profiles of cloud incidence over the Southern Ocean, one centered near the surface and another centered in the upper troposphere; 3) a nearly discontinuous drop-off in cloudiness near 8 km over much of the continent that peaks during autumn, winter, and spring; 4) large east–west gradients in upper-level cloudiness in the vicinity of the Antarctic Peninsula that peak during the austral spring season; and 5) evidence that cloudiness in the polar stratosphere is marked not by a secondary maximum at stratospheric levels but by a nearly monotonic decrease with height from the tropopause. Key results are interpreted in the context of the seasonally varying profiles of vertical motion and static stability and compared with results of previous studies

Correction: The complex genetics of gait speed: Genome-wide metaanalysis approach [Aging, (Albany NY), 9, 1, (2017), (209-246)]doi 10.18632/aging.101151

Applying HaploReg v4.1 analysis to the 536 variants resulted in 9 categories (Supplementary Table 8): miscRNA (1 variant); snoRNA (2 variants); microRNA (4 variants); snRNA (9 variants); pseudogenes (14 variants); sequencing in progress (43 variants); LINC RNA (86 variants); and 372 variants within protein coding genes. In addition, some variants annotate to the same gene resulting in a total of 139 genes (protein-coding or non-coding). Of those genes, 6 are exceptionally long, containing over a million base-pairs, the longest of which is PTPRT coded by 1117219bp. The shortest genes are the ones coding for micro (MIR3143) or small nuclear (U7) RNAs at 63bp each. There is only partial information regarding the chromatin state of each variant. However, from the information gathered in the analysis we observed 14 transcription start sites and 245 enhancers (Supplementary Table 8)