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Furtado J.C.,Atmospheric and Environmental Research Inc. | Cohen J.L.,Atmospheric and Environmental Research Inc. | Butler A.H.,University of Colorado at Boulder | Riddle E.E.,National Oceanic and Atmospheric Administration | And 2 more authors.
Climate Dynamics | Year: 2015

Observational studies and modeling experiments illustrate that variability in October Eurasian snow cover extent impacts boreal wintertime conditions over the Northern Hemisphere (NH) through a dynamical pathway involving the stratosphere and changes in the surface-based Arctic Oscillation (AO). In this paper, we conduct a comprehensive study of the Eurasian snow–AO relationship in twenty coupled climate models run under pre-industrial conditions from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Our analyses indicate that the coupled climate models, individually and collectively, do not capture well the observed snow–AO relationship. The models lack a robust lagged response between October Eurasian snow cover and several NH wintertime variables (e.g., vertically propagating waves and geopotential heights). Additionally, the CMIP5 models do not simulate the observed spatial distribution and statistics of boreal fall snow cover across the NH including Eurasia. However, when analyzing individual 40-year time slices of the models, there are periods of time in select models when the observed snow–AO relationship emerges. This finding suggests that internal variability may play a significant role in the observed relationship. Further analysis demonstrates that the models poorly capture the downward propagation of stratospheric anomalies into the troposphere, a key facet of NH wintertime climate variability irrespective of the influence of Eurasian snow cover. A weak downward propagation signal may be related to several factors including too few stratospheric vortex disruptions and weaker-than-observed tropospheric wave driving. The analyses presented can be used as a roadmap for model evaluations in future studies involving NH wintertime climate variability, including those considering future climate change. © 2015 Springer-Verlag Berlin Heidelberg Source


Jha B.,5830 University Research Court | Jha B.,INNOVIM LLC | Kumar A.,5830 University Research Court | Hu Z.-Z.,5830 University Research Court
Climate Dynamics | Year: 2016

In this analysis, an update in the estimate of predictable component in the wintertime seasonal variability of atmosphere documented by Kumar et al. (J Clim 20: 3888–3901, 2007) is provided. The updated estimate of seasonal predictability of 200-hPa height (Z200) was based on North American Multi-Model Ensemble (NMME) forecast system. The seasonal prediction systems participating in the NMME have gone through an evolution over a 10-year period compared to models that were used in the analysis by Kumar et al. (J Clim 20: 3888–3901, 2007). The general features in the estimates of predictable signal conform with previous results—estimates of predictability remain high in the tropical latitudes and decrease towards the extratropical latitudes; and predictability in the initialized coupled seasonal forecast systems is still primarily associated with ENSO variability. As the horizontal and vertical resolution of the models used in the current analysis is generally higher, it did not have a marked influence on the estimate of the relative amplitude of predictable component. Although the analysis indicates an increase in the estimate of predictable component, however, it maybe related to the increase in ENSO related SST variance over 1982–2000 relative to 1950–2000 (over which the analysis of Kumar et al. in J Clim 20: 3888–3901, 2007 was). The focus of the analysis is wintertime variability in Z200 and its comparison with results in Kumar et al. (J Clim 20: 3888–3901, 2007), some analyses for summertime variability in Z200, and further, for sea surface temperature, 2-m temperature and precipitation are also presented. © 2016 Springer Source


Si D.,National Climate Center | Si D.,Nanjing University of Information Science and Technology | Hu Z.-Z.,National Oceanic and Atmospheric Administration | Kumar A.,National Oceanic and Atmospheric Administration | And 5 more authors.
Climate Dynamics | Year: 2016

The present study examined the major features of the interdecadal variation of the summer rainfall over eastern China (IVRC) and the possible association with sea surface temperature (SST). We noted that the first leading mode of IVRC (accounting for nearly half of the total variance and with maximum loading for the summer rainfall anomalies over South China) may be not forced by SST. On the other hand, the second and third leading modes [accounting for 17.1 and 13.6 % of the total variance and mainly associated with the summer rainfall anomalies over the Yangtze River valley (YRV) and North China, respectively] in some extent are forced by SST anomalies. These observational results are confirmed by atmospheric general circulation model (AGCM) simulations forced by observed SST. By eliminating the internal dynamical process driven rainfall though ensemble mean, the simulations further suggest an overall enhancement of the intensity of IVRC in the corresponding ensemble mean, especially in the YRV and North China regions, but not in South China. That implies the different role of SST in driving IVRC over different regions. © 2015, Springer-Verlag Berlin Heidelberg. Source


Pan C.,The Interdisciplinary Center | Flynn L.,National Oceanic and Atmospheric Administration | Buss R.,INNOVIM LLC | Wu X.,National Oceanic and Atmospheric Administration | And 2 more authors.
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing | Year: 2014

Launched on October 28, 2011, the S-NPP satellite carried an ozone mapping and profiler suite (OMPS) of sensors. OMPS opened its aperture door on January 26, 2012 to begin its Earth observation mission. After an early orbit checkout of the sensors for a couple of months and an intensive evaluation of the sensor data for several more months, an initial on-orbit calibration for OMPS was established using data acquired during these periods. To date in 2013, this sensor system calibration has been applied to produce OMPS nadir sensor data records (SDRs) and the resulting ozone environment data records (EDRs). This paper provides an evaluation of the combined performance of the orbital OMPS nadir sensors coupled with the ground data processing system for the current SDR's provisional status, and offers lessons learned during the first 1.5 years of operation. Examples of the sensors' short-term and limited long-term responses are provided, including cross-comparisons of OMPS EDRs with concurrent solar backscatter ultraviolet instrument (SBUV2) data from other NOAA orbital sensors, to illustrate the on-orbit stability of the data products despite some secular changes to the calibration and sensor. © 2008-2012 IEEE. Source


Pan C.,The Interdisciplinary Center | Flynn L.,National Oceanic and Atmospheric Administration | Wu X.,National Oceanic and Atmospheric Administration | Buss R.,INNOVIM LLC
Journal of Applied Remote Sensing | Year: 2014

This paper analyzes the in-flight performance of the Suomi National Polar-orbiting Partnership Ozone Mapping & Profiling Suite (OMPS) nadir instruments and evaluates sensors' on-orbit calibrations after sensors' two-year operation. All uncertainty values quoted in this paper are 1 - σ values unless stated otherwise. With the data collected from in-flight nominal calibration, our results have demonstrated that sensor performance complies with the system specifications in most cases. The largest term in the wavelength-dependent albedo calibration uncertainty for Nadir Mapper is the cross-track position difference effect of 2.5%. Final adjustments of stray light and wavelength variation are still being made to optimize OMPS sensor data records before reaching the validation mature level. © 2014 Society of Photo-Optical Instrumentation Engineers (SPIE). Source

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