161 research outputs found

    Preliminary Assessment of Suomi-NPP VIIRS On-orbit Radiometric Performance

    Get PDF
    The Visible-Infrared Imaging Radiometer Suite (VIIRS) is a key instrument on-board the Suomi National Polar-orbiting Partnership (NPP) spacecraft that was launched on October 28th 2011. VIIRS was designed to provide moderate and imaging resolution of most of the globe twice daily. It is a wide-swath (3,040 km) cross-track scanning radiometer with spatial resolutions of 370.and 740 m at nadir for imaging and moderate bands, respectively. It has 22 spectral bands covering the spectrum between 0.412 11m and 12.01 11m, including 14 reflective solar bands (RSB), 7 thermal emissive bands (TEB), and 1 day-night band (ON B). VIIRS observations are used to generate 22 environmental data products (EORs). This paper will briefly describe NPP VIIRS calibration strategies performed by the independent government team, for the initial on-orbit Intensive Calibration and Validation (ICV) activities. In addition, this paper will provide an early assessment of the sensor on-orbit radiometric performance, such as the sensor signal to noise ratios (SNRs), dual gain transition verification, dynamic range and linearity, reflective bands calibration based on the solar diffuser (SO) and solar diffuser stability monitor (SOSM), and emissive bands calibration based on the on-board blackbody calibration (OBC). A comprehensive set of performance metrics generated during the pre-launch testing program will be compared to VIIRS on-orbit early performance, and a plan for future cal/val activities and performance enhancements will be presented

    Book Reviews

    Get PDF

    Book Reviews

    Get PDF

    Book Reviews

    Get PDF

    Book Reviews

    Get PDF

    Global variations in oceanic evaporation (1958–2005) : the role of the changing wind speed

    Get PDF
    Author Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 20 (2007): 5376–5390, doi:10.1175/2007JCLI1714.1.Global estimates of oceanic evaporation (Evp) from 1958 to 2005 have been recently developed by the Objectively Analyzed Air–Sea Fluxes (OAFlux) project at the Woods Hole Oceanographic Institution (WHOI). The nearly 50-yr time series shows that the decadal change of the global oceanic evaporation (Evp) is marked by a distinct transition from a downward trend to an upward trend around 1977–78. Since the transition, the global oceanic Evp has been up about 11 cm yr−1 (10%), from a low at 103 cm yr−1 in 1977 to a peak at 114 cm yr−1 in 2003. The increase in Evp was most dramatic during the 1990s. The uncertainty of the estimates is about ±2.74 cm yr−1. By utilizing the newly developed datasets of Evp and related air–sea variables, the study investigated the cause of the decadal change in oceanic Evp. The decadal differences between the 1990s and the 1970s indicates that the increase of Evp in the 1990s occurred over a global scale and had spatially coherent structures. Larger Evp is most pronounced in two key regions—one is the paths of the global western boundary currents and their extensions, and the other is the tropical Indo-Pacific warm water pools. It is also found that Evp was enlarged primarily during the hemispheric wintertime (defined as the mean of December–February for the northern oceans and June–August for the southern oceans). Despite the dominant upward tendency over the global basins, a slight reduction in Evp appeared in such regions as the subtropical centers of the Evp maxima as well as the eastern equatorial Pacific and Atlantic cold tongues. An empirical orthogonal function (EOF) analysis was performed for the yearly winter-mean time series of Evp and the related air–sea variables [i.e., wind speed (U) and air–sea humidity differences (dq)]. The analysis suggested a dominant role of the wind forcing in the decadal change of both Evp and dq. It is hypothesized that wind impacts Evp in two ways. The first way is direct: the greater wind speed induces more evaporation by carrying water vapor away from the evaporating surface to allow the air–sea humidity gradients to be reestablished at a faster pace. The second way is indirect: the enhanced surface wind strengthens the wind-driven subtropical gyre, which in turn drives a greater heat transport by the western boundary currents, warms up SST along the paths of the currents and extensions, and causes more evaporation by enlarging the air–sea humidity gradients. The EOF analysis performed for the time series of the global annual-mean Evp fields showed that the first three EOF modes account for nearly 50% of the total variance. The mode 1 variability represents the upward trend in Evp after 1978 and is attributable to the increased U, and the mode 2 variability explains much of the downward trend in Evp before 1978 and is correlated to the global dq variability. The EOF mode 3 of Evp captures the interannual variability of Evp on time scales of the El Niño–Southern Oscillation, with the center of action over the eastern equatorial Pacific.The author acknowledges the supporting grants from the NOAA Office of Climate Observations (OCO) and Climate Change Data and Detection (CCDD) and from the NASA Ocean Vector Wind Science Team

    Effect of Restricted Preen-Gland Access on Maternal Self Maintenance and Reproductive Investment in Mallards

    Get PDF
    As egg production and offspring care are costly, females should invest resources adaptively into their eggs to optimize current offspring quality and their own lifetime reproductive success. Parasite infections can influence maternal investment decisions due to their multiple negative physiological effects. The act of preening--applying oils with anti-microbial properties to feathers--is thought to be a means by which birds combat pathogens and parasites, but little is known of how preening during the reproductive period (and its expected disease-protecting effects) influences maternal investment decisions at the level of the egg.Here, we experimentally prevented female mallards (Anas platyrhynchos) from accessing their preen gland during breeding and monitored female immunoresponsiveness (e.g., plasma lysozyme concentration) as well as some egg traits linked to offspring quality (e.g., egg mass, yolk carotenoid content, and albumen lysozyme levels). Females with no access to their preen gland showed an increase in plasma lysozyme level compared to control, normally preening females. In addition, preen-gland-restricted females laid significantly lighter eggs and deposited higher carotenoid concentrations in the yolk compared to control females. Albumen lysozyme activity did not differ significantly between eggs laid by females with or without preen gland access.Our results establish a new link between an important avian self-maintenance behaviour and aspects of maternal health and reproduction. We suggest that higher yolk carotenoid levels in eggs laid by preen-gland-restricted females may serve to boost health of offspring that would hatch in a comparatively microbe-rich environment
    • 

    corecore