Simulated historical precipitation is evaluated for Coupled Model Intercomparison Project Phase 6 (CMIP6) models using indices defined by the Expert Team on Climate Change Detection and Indices. The model are against corresponding from CPC unified gauge-based analyses of over seven geographical regions across contiguous US (CONUS). assessed match those in recent National Assessment Reports. To estimate observational uncertainty, three other datasets (HadEx2, Livneh PRISM) analyses. Both...

Objective methods for identifying and quantifying atmospheric blocking have been developed over recent decades, primarily targeting North Atlantic blocks. Differences arise from these methods, leading to changes in the resultant climatology. To understand differences, better inform future assessments built on quantitative detection of blocks, this paper examines properties produced by three different objective algorithms global extratropics. Blocking criteria examined include 500 hPa...

Abstract Filaments of intense vapor transport called atmospheric rivers (ARs) are responsible for the majority poleward in midlatitudes. Despite their importance to hydrologic cycle, there remain many unanswered questions about changes ARs a warming climate. In this study we perform series escalating uniform SST increases (+2, +4, and +6K, respectively) Community Atmosphere Model version 5 an aquaplanet configuration evaluate thermodynamic dynamical response AR content, transport,...

Abstract In climate science and applications, the term “metric” is used to describe distillation of complex, multifaceted evaluations summarize overall quality a model simulation, or other data product, and/or as means quantify some response change. Metrics provide insights into fidelity processes outcomes from models can assist with both differentiating models' representation variables informing whether are “fit for purpose.” also valuable reference point co‐production knowledge between...

Abstract We analyze large‐scale statistically meaningful patterns (LSMPs) that precede extreme precipitation (PEx) events over Northern California (NorCal). find LSMPs by applying k‐means clustering to the two leading principal components of daily 500 hPa geopotential height anomalies days before onset, from October March during 1948–2015. Statistical significance testing based on Monte Carlo simulations suggests a minimum four distinguished LSMP clusters. The clusters are characterized as...

Abstract Extraordinary weather events in the Sacramento, California, region are examined using a simple compositing technique. The extraordinary identified uncommon and worst of their kind, but not necessarily severe. While criteria outlined herein drawn from Sacramento station data, elsewhere over much, if all, California’s Central Valley. Several types highlighted, including hardest freezes, heaviest prolonged rain events, longest-duration fog, heat waves (onset end) 21-yr period....

This study examines associations between California Central Valley (CCV) heat waves and the Madden Julian Oscillation (MJO). These have major economic impact. Our prior work showed that CCV are frequently preceded by convection over tropical Indian eastern Pacific oceans, in patterns identifiable with MJO phases. The main analysis method is lagged composites (formed after each phase pair) of synoptic station temperature, outgoing longwave radiation (OLR), velocity potential (VP). Over CCV,...

The errors introduced by the use of various numerical schemes for solving mathematical models have generally been only vaguely determined previously modelers. A method a more quantitative analysis inaccuracies is outlined. error associated with some simple analyzed several linear hyperbolic systems representative typical problems in meteorology and oceanography. Results previous studies phase velocity are confirmed form basis an extension to group velocities. Significant angular magnitude...

A pilot scheme uses upper air data from a few extreme hottest days to identify those and other measured by 3 stations sampling the California Central Valley (CV). Prior work showed that CV heat wave onsets have characteristic large scale patterns in many upper-air variables; also occur for days. areas of two variables with high significance consistency forecast surface temperatures. The projects key parts composite one or more onto daily weather maps corresponding resulting 'circulation...

Abstract California Central Valley (CCV) heat waves are grouped into two types based on the temporal and spatial evolution of large-scale meteorological patterns (LSMPs) prior to onset. The k-means clustering key features in anomalous temperature zonal wind identifies groups. Composite analyses show different developing a similar ridge–trough–ridge pattern spanning North Pacific at onset CCV hot spells. Backward trajectories adiabatic heating air enhanced by sinking plus horizontal advection...

Abstract Traditional multimodel methods for estimating future changes in precipitation intensity, duration, and frequency (IDF) curves rely on mean or median of models’ IDF estimates. Such estimates are impaired by large estimation uncertainty, shadowing their efficacy planning efforts. Here, assuming that each climate model is one representation the underlying data generating process, i.e., Earth system, we propose a novel extension current through pooling data: (i) evaluate performance...

Warming is a major climate change concern, but the impact of high maximum temperatures depends upon air's moisture content. Trends in summertime temperature, moisture, and heat index are tracked over three time periods: 1900-2011, 1950-2011, 1979-2011; these trends differ notably from annual temperature trends. emphasized two CRU datasets (CRUTS3.25 CRUTS4.01) reanalyses (ERA-20C 20CRv2). Maximum tend towards warming that stronger Great Lakes, interior western northeastern contiguous United...

For the past two years, authors have been involved in production of computer-animated movies at National Center for Atmospheric Research (NCAR). The computer- generated frames are high-quality graphs two- and three-dimensional variables featuring trajectories, contour lines, shading patterns, or surfaces (viewed perspective). original application was comparing FGGE dataset motion fields with satellite film loops. Applications broadened to include model-generated data. Computer animation is...

Abstract Previous work showed that climate models capture historical large‐scale meteorological patterns (LSMPs) associated with California Central Valley heat waves including both ways these form. This examines what predict under the Representative Concentration Pathway (RCP) 4.5 and RCP8.5 scenarios. Model performance varies, so a multimodel average weights each model based on its in four parameters. An LSMP index (LSMPi) defined using upper atmosphere variables captures dates of past...

"An Interdisciplinary Approach to the Study of Extreme Weather Events: Large-Scale Atmospheric Controls and Insights from Dynamical Systems Theory Statistical Mechanics" published on May 2018 by American Meteorological Society.

This article describes results from numerical experiments which isolate the influence of horizontal curvature upon various linear properties growing baroclinic eddies. Cylindrically symmetric mean flows on an f-plane are studied; they have either strong or weak curvature. The radius is twice as large for it Strong reduces growth rates and this most evident only short waves. energy conversion positive (from flow to eddy) little influenced by barotropic made more negative stronger curvature;...

How does extreme cold air reach the California Central Valley (CCV) and most of U.S. west coast? This question is answered using composite patterns for 10 coldest outbreaks (CAOs) to CCV during 1979–2013. While unusually over occurs in all events by design, how it arrives there complicated varies. The only other feature present several days prior CAO onset strong surface high pressure south Gulf Alaska. has low-level on its side a deep layer moving southward east side. Cold aloft flows...