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Weather regime based stochastic weather generators (WR‐SWGs) have recently been proposed as a tool to better understand multi‐sector vulnerability to deeply uncertain climate change. WR‐SWGs can distinguish and simulate different types of climate change that have varying degrees of uncertainty in future projections, including thermodynamic changes (e.g., rising temperatures, Clausius‐Clapeyron scaling of extreme precipitation) and dynamic changes (e.g., shifting circulation and storm tracks). These models require the accurate identification of WRs that are representative of both historical and plausible future patterns of atmospheric circulation, while preserving the complex space–time variability of weather processes. This study proposes a novel framework to identify such WRs based on WR‐SWG performance over a broad geographic area and applies this framework to a case study in California. We test two components of WR‐SWG design, including the method used for WR identification (Hidden Markov Models (HMMs) vs. K‐means clustering) and the number of WRs. For different combinations of these components, we assess performance of a multi‐site WR‐SWG using 14 metrics across 13 major California river basins during the cold season. Results show that performance is best using a small number of WRs (4–5) identified using an HMM. We then juxtapose the number of WRs selected based on WR‐SWG performance against the number of regimes identified using metastability analysis of atmospheric fields. Results show strong agreement in the number of regimes between the two approaches, suggesting that the use of metastable regimes could inform WR‐SWG design. We conclude with a discussion of the potential to expand this framework for additional WR‐SWG design parameters and spatial scales. [ABSTRACT FROM AUTHOR]

Frequency and duration of flood events are analyzed using Dartmouth Flood Observatory's (DFO) global flood database to detect significant trends and regime shifts during 1985-2015 at global and latitudinal scales. Three classes of flood duration (i.e. short: 1-7, moderate: 8-20, and long: 21 days and above) are also considered for this analysis. The non-parametric Mann-Kendall trend test and Pettitt change-point analysis are used to evaluate three hypotheses (H1, H2, and H3) addressing potential monotonic trends and regime shifts in flood frequency, moments of the duration, and the frequency of a specific flood duration type. The results show that long duration flood frequency has increased across most spatial scales with significant change-point observed in the 2000s. In the tropics, floods have increased four-fold since the 2000s. This increase is 2.5 fold in the north mid-latitudes. There is no monotonic trend in the frequency of short duration floods across all global and latitudinal scales. There is also a significant increasing trend in the annual median and tails of flood durations globally and in each latitudinal belt. The possible causes of these trends are analyzed using a Generalized Linear Model framework and also discussed qualitatively. This analysis provides the framework for understanding simultaneously changing climate and socioeconomic conditions and how they relate to the frequency and persistence in the organization of global and local dynamical systems that cause hydrologic extremes. [ABSTRACT FROM AUTHOR]

GNSS-R (Global Navigation Satellite System-Reflectometry) can remotely sense Earth's surface characteristics and retrieve geophysical parameters, e.g., snow depth and soil moisture. However the surface reflectivity interaction and scattering characteristics from GNSS signals are not clear. In this paper, we model the scattering properties and investigate the surface's reflectivity characteristics interacting with GPS L1 and L2 signals in order to retrieve multipath signals and precisely infer surface characteristics. Furthermore, the effects of snow accumulating and melting together with bare soil and fixed snow depth are studied by GNSS-R. A case study from GPS observations at BAKE site is also presented as well as discussed. [ABSTRACT FROM AUTHOR]