ALBERT

Description: Based on measurements of ultraviolet radiation (UV) for the period 2005-2014 that were obtained from the Chinese Ecosystem Research Network (CERN), we developed an efficient model to estimate UV radiation under various sky conditions. This model can provide an accurate reconstruction of UV radiation data with absolute mean bias error less than 9.65%. We combined this reconstruction model with a hybrid model to obtain the historical dataset of daily UV radiation from 1961 to 2014 at 37 weather stations belonging to the China Meteorological Administration (CMA) over the Tibetan Plateau (TP). Based on the historical dataset, the spatial distribution and temporal variation of UV radiation over the TP region were discussed. The decreasing and increasing periods of ultraviolet radiation over the TP were significantly different from those over the entire China. There was an increasing trend in UV radiation over the TP from 1961 to 1983, followed by a decreasing one until 2014; while UV radiation decreased from 1961 to 1989 and then increased slightly after 1989 for the entire China. The average UV radiation values in the increasing and decreasing periods over the TP were 0.598 MJ · m -2  · d -1 and 0.594 MJ · m -2  · d -1 , respectively. In addition, aerosol optical depth, column ozone and cloud prevent approximately 7.13%, 1.31%, and 15.05% of UV radiation reaching the Earth's surface respectively.

Description: We search for possible localized tidal triggering in earthquake occurrence near Japan by testing for tidal periodicities in seismicity within a variety of space/time bins. We examine 74,610 earthquakes of M ≥3 in the Japan Meteorological Agency (JMA) catalog from January 2000 to April 2013. Because we use many earthquakes for which accurate focal mechanisms are not available, we do not compute tidal stresses on individual fault planes, but instead assume that the mechanisms are likely to be similar enough among nearby events that tidal triggering will promote earthquake occurrence at specific tidal phases. After dividing the data into cells at a range of spatial (0.2 ∘ , 0.5 ∘ , 1.0 ∘ ) and temporal dimensions (100, 200, 400 days), we apply Schuster's test for non-random event occurrence with respect to both the semi-diurnal and semi-monthly tidal phases. Because the resulting p -values will be biased by temporal clustering caused by aftershocks, we apply a declustering method that retains only one event per tidal cycle per phase increment. Our results show a wide range of p -values for the localized earthquake bins, but the number of bins with very small p -values (e.g., p 〈 0.05) is no more than might be expected due to random chance, and there is no correlation of low p -value bins with the time of the 2010 M 9.0 Tohoku-oki earthquake.

Description: A batch system is an inherently parametric sensitivity system where small changes of input parameters can induce large changes of output variables. In the present work, temperature and temperature sensitivity with respect to the initial temperature were investigated by parametric sensitivity analysis using a dimensionless batch reactor model. The influence of the Semenov number, the heat of reaction parameter and the Arrhenius-type number on reactor temperature and temperature sensitivity were studied. It is demonstrated that batch reactors can exhibit high sensitivity when small changes in input parameters lead to large changes in temperature and temperature sensitivity trajectories. A criterion is established for thermal runaway by analyzing temperature sensitivity trajectories and applied to some experimental examples. This criterion allows runaway and safe conditions to be identified, the results being in agreement with the experimental data. The proposed criterion can satisfactorily predict the safety limits of the operating conditions. Increasing attention has been paid to thermally safe operation of chemical reactors to avoid runaway accidents. A new and simple sensitivity-based criterion was developed for thermal runaway in batch reactors by analyzing temperature sensitivity trajectories and applied to experimental examples. The proposed criterion has proved to be very effective in predicting the critical conditions of thermal runaway.

Description: The present paper addresses the stochastic heating of minor ions by obliquely-propagating low-frequency Alfvén waves in the solar wind. An important characteristics of the stochastic heating is unearthed by means of test particle simulation. That is, when the wave amplitude exceeds some threshold condition for stochasticity, the time-asymptotic kinetic temperature associated with the minor ions becomes independent of the wave amplitude, and it always approaches the value dictated by the Alfvén speed, to wit, Tkin. ∼ mivA2/2. During the course of the heating process the minor ions gain a net average parallel speed, v$\parallel$ ∼ vA in the laboratory frame. These results are consistent with observations which find that minor heavy ions often move faster than the local protons with a speed roughly equal to the local Alfvén speed.

Description: Using measurements of the electron density ne found from passive radio wave observations by the IMAGE spacecraft RPI instrument on consecutive passes through the magnetosphere, we calculate the long-term (〉1 day) refilling rate of equatorial electron density dne,eq/dt from L = 2 to 9. Our events did not exhibit saturation, probably because our data set did not include a deep solar minimum and because saturation is an unusual occurrence, especially outside of solar minimum. The median rate in cm−3/day can be modeled with log10(dne,eq/dt) = 2.22 − 0.006L − 0.0347L2, while the third quartile rate can be modeled with log10(dne,eq/dt) = 3.39 − 0.353L, and the mean rate can be modeled as log10(dne,eq/dt) = 2.74 − 0.269L. These statistical values are found from the ensemble of all observed rates at each L value, including negative rates (decreases in density due to azimuthal structure or radial motion or for other reasons), in order to characterize the typical behavior. The first quartile rates are usually negative for L 〈 4.7 and close to zero for larger L values. Our rates are roughly consistent with previous observations of ion refilling at geostationary orbit. Most previous studies of refilling found larger refilling rates, but many of these examined a single event which may have exhibited unusually rapid refilling. Comparing refilling rates at solar maximum to those at solar minimum, we found that the refilling rate is larger at solar maximum for small L 〈 4, about the same at solar maximum and solar minimum for L = 4.2 to 5.8, and is larger at solar minimum for large L 〉 5.8 such as at geostationary orbit (L ∼ 6.8) (at least to L of about 8). These results agree with previous results for ion refilling at geostationary orbit, may agree with previous results at lower L, and are consistent with some trends for ionospheric density.

Description: Enhancements in F-region electron density and temperature and bottomside Pedersen conductivity caused by soft electron precipitation are shown to enhance the Joule heating per unit mass and the mass density of the thermosphere at F-region altitudes. The results are derived from the coupled magnetosphere-ionosphere-thermosphere model (CMIT) including two types of causally specified soft electron precipitation—direct-entry cusp precipitation and Alfvén-wave induced, broadband electron precipitation—the effects of which are self-consistently included for the first time in a coupled global simulation model. The simulation results provide a causal explanation of CHAMP satellite measurements of statistical enhancements in thermospheric mass density at 400 km altitudes in the cusp and premidnight auroral region.

Description: Abstract Seismic coda waves can be used to constrain attenuation, estimate earthquake magnitudes, and determine site amplification factors. We have developed a new multistation and multievent method to determine these three important seismic parameters simultaneously. We analyze 642 representative local (≤100 km) and shallow (≤20 km) earthquakes with catalog magnitudes between 1.8 and 5.4 in southern California at multiple frequency bands centered at 1.5, 3, 6, and 12 Hz. We find that the length of the moving average time window can affect the measurement of coda attenuation QC, but our tests indicate that the optimal window length is about 15 times the dominant data period. We use linear regression to fit each coda section and use only those portions that agree with the model decay rate with a correlation coefficient larger than 0.9. For a frequency‐dependent coda‐QC model (QC = Q0fn) at 1‐Hz reference frequency, our results yield estimates for Q0 and n of 107–288 and 0.42–1.14, respectively. Our coda magnitude estimates are linearly correlated with catalog magnitudes, and our observed lateral variations in coda‐QC and our site amplification factors are in general agreement with previous results, although there are notable differences at some locations. This approach provides a unified, accurate, and stable method to measure coda‐QC, earthquake magnitude, and site amplification using coda waves of locally recorded earthquakes.

Description: Characterizing scattering and absorbing properties and the power spectrum of crustal heterogeneity is a fundamental problem for informing strong ground motion estimates at high frequencies, where scattering and attenuation effects are critical. We perform a comprehensive study of local earthquake coda waves in southern California to constrain scattering and intrinsic attenuation structure. We analyze data from 1195 spatially distributed earthquakes from 1981–2013 at source depths of 10 to 15 km and epicentral distances from 0–250 km with magnitudes larger than 1.8. We stack envelope functions from 28,127 vertical-component and 27,521 transverse-component seismograms, filtered from 2 to 4 Hz. We model these observations using a particle-based Monte Carlo algorithm that includes intrinsic attenuation as well as both P- and S-wave scattering and both single and multiple scattering events. We find that spatially averaged coda-wave behavior for southern California can be explained only with models containing an increase in scattering strength and intrinsic attenuation within the uppermost crust, i.e., they are poorly fit with half-space models of constant scattering strength. A reasonable fit to our data is obtained with a two-layer model, composed of a shallow crustal layer with strong wide-angle scattering and high P and S intrinsic attenuation and a deeper layer with weaker scattering and lower intrinsic attenuation (top 5.5 km: α Q I = 250, β Q I = 125, heterogeneity correlation length a = 50 m, fractional velocity heterogeneity ε = 0.4; lower crust: α Q I = 900, β Q I = 400, a = 2 km, ε = 0.05).

Description: Abstract Radar‐rain gauge merging techniques have been widely used to improve the applicability of radar and rain gauge rainfall estimates by combining their advantages, while partially overcoming their individual weaknesses. Despite significant research in this area, guidance on the suitability of, and factors affecting merging techniques at the fine spatial‐temporal resolutions required for urban hydrological applications is still insufficient. In this paper, an in‐depth review of radar‐rain gauge merging techniques is conducted, with a focus on their potential for urban hydrological applications. An overview is first given of existing merging techniques and an application‐oriented categorization is proposed: (1) radar bias adjustment methods; (2) rain gauge interpolation methods using radar spatial association as additional information; (3) radar‐rain gauge integration methods. A detailed review is given of studies focusing on the evaluation and inter‐comparison of merging methods, based upon which the most widely used and best performing techniques from each category are identified. These are: Mean Field Bias (MFB) adjustment, Kriging with External Drift (KED), and Bayesian (BAY) merging. Climatological, operational and methodological factors affecting merging performance are then reviewed and their relevance for urban applications discussed. Based on this review, conclusions on merging potential for urban applications are drawn and research gaps are identified which should be addressed to provide further guidance on the use of merging techniques for urban hydrological applications.

Description: The primary goal of this paper is to introduce two new surface reflectivity climatologies. The two databases contain the Lambertian-equivalent reflectivity (LER) of the Earth's surface, and they are meant to support satellite retrieval of trace gases and of cloud and aerosol information. The surface LER databases are derived from the GOME-2 and SCIAMACHY instruments and can be considered as improved and extended descendants of earlier surface LER climatologies based on the TOMS, GOME-1, and OMI instruments. The GOME-2 surface LER database consists of 21 wavelength bands that span the wavelength range from 335 to 772 nm. The SCIAMACHY surface LER database covers the wavelength range between 335 and 1670 nm in 29 wavelength bands. The two databases are made for each month of the year and their spatial resolution is 1 ∘ ×1 ∘ . In this paper we present the methods that are used to derive the surface LER, we analyze the spatial and temporal behavior of the surface LER fields, and study the amount of residual cloud contamination in the databases. For several surface types we analyze the spectral surface albedo and the seasonal variation. When compared to the existing surface LER databases, both databases are found to perform well. As an example of possible application of the databases we study the performance of the FRESCO cloud information retrieval when it is equipped with the new surface albedo databases. We find considerable improvements. The databases introduced here can not only improve retrievals from GOME-2 and SCIAMACHY, but also support those from other instruments, such as TROPOMI, to be launched in 2017.